Molecular & crystal design

Abstract The forensic sodium rhodizonate test is used to detect lead in gunshot debris. Areas of interest are sprayed with a sodium rhodizonate solution followed by a tartrate buffer solution of pH 2.8, producing a deep red compound indicative of lead and other metals. A confirmatory hydrochloric acid spray produces a violet color specific to lead. The associated chemical transformations of the insoluble lead rhodizonate complexes have not been specified. Lead rhodizonate, lead rhodizonate tartrate, and lead rhodizonate chloride coordination polymers were synthesized from dilute solutions of sodium rhodizonate and lead nitrate in water, tartrate buffer, and HCl buffer. Nanoparticles of the precipitates were analyzed by three-dimensional electron diffraction (3D ED). A crystal, Pb24+(C6O6)2–Cl22–·3H2O, was characterized in the space group R3̅m (a = 8.0708(3) Å, c = 16.576(3) Å), with rhodizonate layers bidentately coordinated to three lead ions, offset by ca. 0.05 Å from the rhodizonate planes. Solid-state nuclear magnetic resonance revealed the presence of a single axial lead site in the nitrate precipitate, a distribution of lead sites in the lead rhodizonate tartrate precipitate, and three distinct sites in the lead rhodizonate chloride precipitate, suggesting other Pb compounds in the bulk coexisting with the 3D ED product.

Modeling the electric field gradient (EFG) in molecular dynamics (MD) simulations enables the prediction of nuclear magnetic resonance (NMR) relaxation rates thus allowing to unravel the underlying relaxation-active molecular motion. Here, we compare the linear-response Sternheimer model with a novel machine-learning (ML) approach to simulate 14 N quadrupolar T 1 relaxation in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF 4]). Improving the parametrization of the Sternheimer model at the low-symmetry nitrogen sites required an electron density-based charge-partitioning scheme. In contrast, the parameter-free ML descriptor directly captured the EFG dynamics, providing a flexible methodology for computing EFG tensors in complex ionic systems. In the extreme-narrowing regime, both models predicted relaxation rates in excellent agreement with experimental measurements. Finally, using a regularized inverse Laplace transform, we deconvolute the dynamics of the EFG tensor and of the cation inertia tensor, and identify molecular rotation as the dominant mode responsible for 14 N quadrupolar relaxation.

We present an open Molecular Crystal (MC) database of Machine-Learned Interatomic Potentials (MLIPs) called MolCryst-MLIPs. The first release comprises fine-tuned MACE models for nine molecular crystal systems─Benzamide, Benzoic acid, Coumarin, Durene, Isonicotinamide, Nicotinic acid, Niacinamide, Pyrazinamide, and Resorcinol─developed using the Automated Machine Learning Pipeline (AMLP), which streamlines the entire MLIP development workflow, from reference data generation to model training and validation, into a reproducible and user-friendly pipeline. Models are fine-tuned from the MACE-MH-1 foundation model (omol head), yielding a mean energy MAE of 0.141 kJ·mol-1·atom-1 and a mean force MAE of 0.648 kJ·mol-1·Å-1 across all systems. Benchmarked against three state-of-the-art foundation models on the DFT-labeled polymorph set, only the fine-tuned models reliably identify the most stable polymorph, with a mean Kendall τ = 0.397 indicating a moderate rank correlation with the full DFT landscape. Dynamical stability and structural integrity, as assessed through energy conservation, P2 orientational order parameters, and radial distribution functions, are evaluated using molecular dynamics simulations. The released models and data sets constitute a growing open database of validated MLIPs, ready for production MD simulations of molecular crystal polymorphism across the polymorphic landscape of each target compound under different thermodynamic conditions.

The stabilization and functional integration of organic radicals within crystalline frameworks remain a significant challenge in materials chemistry, particularly for applications in optoelectronics and sensing. Herein, we report the design and synthesis of a radical-rich, polyrotaxanated covalent organic framework (VCB COF) featuring viologen-based radical cation dimers mechanically interlocked within cucurbit[8]uril (CB[8]) macrocycles. This supramolecular architecture gives rise to a double-walled framework that significantly enhances radical stability, photophysical properties, and photoresponsivity. Electron paramagnetic resonance (EPR) analysis reveals that VCB retains over 72% of its radical signal after 7 days of air exposure, compared to just 22% in its nonrotaxanated analogue, TpV COF. Photophysical studies reveal a 3-fold increase in photoluminescence intensity, while photoelectrochemical measurements demonstrate a stable photocurrent density of 1.3 μA cm-2 under 405 nm illumination with reversible on/off switching. Molecular dynamics simulations together with solid-state NMR support the localization of CB[8] at COF junctions and are consistent with the formation of a double-walled architecture stabilized by dipolar and long-range noncovalent interactions. This work establishes a generalizable strategy for integrating persistent radicals within COFs through macrocycle-assisted encapsulation and mechanical bonding, opening new avenues for the development of robust photoactive, redox-active, and spin-functional materials.

Organic charge transfer cocrystals (OCTCs) are an appealing platform for solution processable electronics with tunable properties. Thanks to their modular, molecular composition, OCTC electronics and optics can be varied by the design and selection of electron-donors and acceptors, but to achieve the goal of bespoke properties-by-design, detailed structure-function relationships are needed. One particular challenge is separately interrogating the effects of crystal packing from the effects of donor/acceptor strengths, as it is difficult to find systems where packing can be tuned without meaningfully changing the donor or acceptor strength. In this work, we use a series of easily-prepared 2,3,6,7-tetramethoxy-9,10-dialkylanthracene donors with varying substituent sizes and essentially invariant donor strengths in combination with tetracyanoethylene to probe the effects of crystal packing on OCTC properties. Across a set of five OCTCs, we observe both alternating and slip-stacked segregated stacking motifs. The stacking arrangements are correlated with CT absorbances, related optical properties, TCNE C=C bond lengths, and corresponding degree of charge-transfer (DCT). Electrical transport under ambient conditions shows no clear trend in relation to molecular arrangement, with all OCTCs being very poorly semiconducting. Using X-ray crystallography and transmission absorbance spectroscopy of singlecrystals, we inform structure-function relationships for optical properties of OCTCs with an electron donor platform that may be tuned sterically while holding electronics constant.

High Resolution Image Download MS PowerPoint Slide Ionic liquids are complex liquids characterized by high viscosity and high polarity. Their dynamics are of interest due to their use in many fields that require unconventional solvent environments. Here, we develop an MD-based forward-prediction framework to calculate NMR relaxation rates in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, [bmim][BF 4], and investigate their temperature and magnetic-field dependence. We show that the combination of intra- and intermolecular dipolar couplings and chemical shift anisotropy interactions allows accounting for the experimentally observed nuclear spin lifetimes when considering multimodal relaxation processes. A regularized inverse Laplace transformation of MD-derived interactions reveals generally bimodal motional processes active in both inter- and intramolecular effects. The presence of two main motional processes may be somewhat surprising for intramolecular effects, especially in the symmetric [BF 4] − unit, but can be attributed to the restricted motion due to the local environment. We also highlight that the Bloembergen–Purcell–Pound (BPP) approach that is often used to characterize average motional correlation times is not reliable in most situations encountered with realistic systems. Consequently, we argue that achieving quantitative agreement between predicted and measured NMR relaxation rates offers a more robust route to extracting structural and dynamical information from complex liquids.

Molecular crystals are a highly polymorphic class of materials, with a single molecule commonly crystallizing via multiple packing patterns, making structure and property prediction very challenging. Crystal structure prediction typically comprises the production of sets of promising candidate structures, each considered in isolation rather than as samples in a thermodynamic distribution. Likewise, modern generative approaches to this problem, despite naturally sampling distributions of crystals, lack a concrete formulation of the distributions being sampled. Two components are required to impart meaning to the distributions of crystals generated under such models: a canonical parameterization, and a loss function which equilibrates the generated samples to some target distribution. We develop such a parameterization, and train energy-based generative flow networks (GFlowNets) to approximate the Boltzmann distribution over crystal structures for target molecules and space groups. Combined, these components comprise our MXtalGFlow framework for molecular crystal modeling. Going beyond sampling disconnected sets of low-energy structures, MXtalGFlow yields a thermodynamic distribution over crystal structures. We sample and analyze distributions of crystals for two molecules, each under two energy functions, a Lennard-Jones potential and the Universal Model for Atoms. We characterize the local structural basins about the known polymorphs, and identify additional as-yet un-reported packing modes with competitive probabilities to the known experimental structures. With MXtalGFlow, we illustrate how to define and train a model to sample a thermodynamically meaningful distribution of molecular crystals, and analyze such a distribution to glean useful information.

Chiral ensembles can arise through supramolecular curvature that resolves geometric frustrations in the packing of bent, achiral molecular or colloidal building blocks. Here, we leverage orthogonal protection-deprotection click chemistry to create sequence-defined mesogenic heterodimers exhibiting emergent chirality. We compare the hierarchical self-assembly of the synthesized asymmetric, achiral heterodimers, which differ only in the position of a methyl substituent. Both dimers form chiral spherulites composed of nanocylinders. However, the detailed arrangement of nanocylinders depends on the position of the methyl substituent and the crystallization conditions. Despite the chemical similarity, in one dimer, two crystalline forms are optically active. They form conglomerates of dextrorotatory and levorotatory spherulites. The other dimer forms more highly anisotropic spherulites that mask circular birefringence arising from the misorientation of nanocylinders, while mapping of nanocylinder directors reveals a sense at the spherulite surface. We propose that differences in nanocylinder arrangements may arise from changes in nanocylinder curvature and dimensions dictated by the methyl substituent position, inducing chirality. These results demonstrate multiscale hierarchical assembly relevant to dense systems of tubular structures and highlight the role of sequence and molecular design in directing the bottom-up hierarchical self-assembly and chirality of mesogenic systems.

High Resolution Image Download MS PowerPoint Slide Poly(phenylenevinylene)s (PPV)s are a class of fluorescent conjugated polymers used in organic light emitting diodes (OLEDs). Living chain growth polymerization of PPVs is typically achieved by ring-opening metathesis polymerization (ROMP) of highly strained cyclophanedienes. While benzene-based cyclophanedienes are routinely reported, living or controlled ROMP of naphthalene-benzene containing mixed cyclophanedienes remains a challenge. This work describes the synthesis and polymerization of an alkoxy substituted naphthalene-benzene cyclophanediene using Schrock’s molybdenum olefin metathesis catalyst. We demonstrate the efficacy of this strategy in producing poly(naphthalene benzene vinylene) (PNBV)s with controlled molecular weights and narrow dispersities. The produced PNBVs are highly fluorescent polymers in solution and as thin films with distinct emission signatures arising from the benzene and naphthalene chromophores. An unoptimized PNBV thin film transistor exhibited a hole mobility of 8 × 10 –9 cm 2 /V·s, which increased to 1 × 10 –7 cm 2 /V·s upon doping with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) and (tris(2-(1 H-pyrazol-1-yl)-4- tert-butylpyridine)cobalt(III) (FK 209). This expansion of ROMP to include the naphthalene moiety as well as a mixed-aromatic system will usher further development of electronically diverse PPVs with advanced solid-state applications.

Identifying reliable, nondestructive indicators of electrolyte degradation is essential for advancing the diagnostics and lifetime assessment of lithium-ion batteries. In this study, we performed multinuclear nuclear magnetic resonance spectroscopy at various time points during systematic degradation of battery electrolyte components undergoing thermal cycling. We highlight a strong correlation between electrolyte degradation state and the 7Li nuclear spin polarization lifetime, while other nuclei did not respond as strongly. A mechanistic rationale for this phenomenon is provided using molecular dynamics simulations. The remarkable sensitivity of 7Li nuclear spin lifetime to electrolyte health underscores its potential value as a nondestructive, field-independent probe suited for diagnosing defects and evaluating the overall health of lithium-ion batteries.

We present MXtalTools, a flexible Python package for the data-driven modeling of molecular crystals, facilitating machine learning studies of the molecular solid state. MXtalTools comprises several classes of utilities: (1) synthesis, collation, and curation of molecule and crystal data sets, (2) integrated workflows for model training and inference, (3) crystal parametrization and representation, (4) crystal structure sampling and optimization, (5) end-to-end differentiable crystal sampling, construction, and analysis. Our modular functions can be integrated into existing workflows or combined and used to build novel modeling pipelines. MXtalTools leverages CUDA acceleration to enable high-throughput crystal modeling. The Python code is available open-source on our GitHub page, with detailed documentation on ReadTheDocs.

Sticky-ended cohesion has been the driving force for DNA self-assembly and has enabled model and design programmability in DNA nanotechnology for over 40 years. Traditional units within self-assembled crystals have rationally-designed sticky ends to avoid unpredictable packing behavior, but in doing so, the surprising variety of contact flavors available to natural nucleic acids remains unexploited. Here, we employ composable DNA tiles to form complex 3D architectures using blunt-ended motifs with single duplex interfaces, thereby leveraging the geometry of the tile and the terminal nucleobase identity to control self-assembly outcomes. These crystals yielded X-ray diffraction at resolutions between 10.0 and 1.86 Å. We establish programmability and tunable packing, including translational and inversion symmetries, 5’−3’ and 5’−5’ stacking, and both positive and negative helical twist values. Finally, we establish the ability of racemic mixtures of L- and D-DNA motifs to perform programmable co-assembly driven by terminal π–π interactions, demonstrating molecular recognition and coexistence between mirror molecular systems. Sticky-ended cohesion has historically been the driving force for DNA self-assembly and was employed for self-assembled crystals to avoid unpredictable packing; however, this limits the diversity of resulting architectures. Here, the authors employ composable DNA tiles to form complex 3D architectures using blunt-ended motifs with single duplex interfaces, leveraging the geometry of the tile and the terminal nucleobase identity to control self-assembly outcomes.

High Resolution Image Download MS PowerPoint Slide In this journal, Moses Gomberg’s 1900 revelation, “An Instance of Trivalent Carbon: Triphenylmethyl”, lauded on a centennial National Historic Chemical Landmark for challenging the “prevailing belief that carbon can only have four bonds”, shifts its place in our imaginations as the facts given here are accommodated. In 1898 Gomberg presumed that he had made a molecular complex of bromotriphenylmethane and two neutral I 2 molecules. But he was mistaken. Instead, Gomberg produced a mixture of three persistent single crystals of the triphenylmethyl cation before he published his aforementioned, controversial paper. Trigonal carbon coordination was the crack in the valency rules that had organized chemistry prior to the invention of quantum mechanics. Gomberg did not recognize the wealth of trivalent carbon compounds he had in hand before the proposition of the radical and corresponding cation thereafter. This work alludes to a counterfactual history.

Colloidal quantum dots (cQDs) have emerged as a cornerstone of next-generation optoelectronics, offering unparalleled spectral tunability and solution-processability. However, the transition from laboratory-scale devices to sustainable industrial manufacturing is fundamentally hindered by spin-coating workflows, which are intrinsically wasteful and restricted to planar geometries. These limitations are particularly acute for high-performance cQDs containing regulated elements such as lead, cadmium, or mercury, where poor material utilization exacerbates both environmental burden and cost. Here we report a biphasic dip-coating strategy that redefines the material efficiency of nanocrystal film fabrication. By utilizing an immiscible underlayer to displace ~88% of the active reservoir volume, we demonstrate a deposition geometry that decouples material consumption from total precursor volume. Infrared PbS photodetectors fabricated via this approach maintain their performance against spin-coated benchmarks while reducing ink consumption by up to 20-fold. Our technoeconomic analysis reveals that this biphasic architecture achieves cost parity at film thicknesses an order of magnitude lower than conventional monophasic dip-coating. Our results establish a low-waste framework for solution-processed materials, providing a viable pathway for the resource-efficient manufacturing of optoelectronic devices.

Concentrated hydrogen-bonded electrolytes (CoHBEs) are structured, electrochemically stable, less-volatile alternatives to aqueous and dilute nonaqueous electrolytes, however, with high viscosities that limit molecular diffusion. This work provides an understanding of the proton conduction mechanism in CoHBEs based on mixtures of acids and azoles and establishes a link between the structurally dictated transport properties and the proton-coupled electron transfer (PCET) reaction rates that can be leveraged for enhancing electrochemical reactions. Diffusion and relaxation NMR studies suggest a breaking of the viscosity–conductivity tradeoff, where at high azole concentrations (>45 mol%), Grotthuss transport is more likely with lowered proton transfer energy barriers between the azole and the acid according to the machine learning (ML) accelerated ab initio path integral MD (AI-PIMD) simulations. Proton conduction pathways are found to be switchable between the hydrogen bonding networks of the acid and the azole, with imidazole chain forming structures better facilitating Grotthuss hopping. Supported by small-angle neutron scattering studies, the chains are found to have six member molecules on average with maximum of 3 to 4 imidazole/imidazoliums at 50 to 60 mol%. Despite their high viscosities, the measured PCET rates for quinones and phenazines measured in the protic CoHBEs present relatively high electron transfer rate constants (k 0 ~ 10 − 4 cm/s), validated by rotating disc electrode and scanning electrochemical microscopy measurements. The results demonstrate that strategic tuning of hydrogen-bond donor–acceptor interactions enables the decoupling of proton transport and viscosity, thereby impacting PCET reactions.

H NMR spectroscopies. Scanning electron microscopy and energy dispersive X-ray spectroscopy demonstrate the reversibility of these changes, with crystal morphology and surface composition nearly returning to near-pristine single crystals of BP4VA after annealing. The recoverability of single crystals enables a promising platform for the detection of volatile organic compounds.

Ultralow-field nuclear magnetic resonance has the power to see chemistry through metallic enclosures—enabling nondestructive quantitative tracking of the state and composition of liquid-state electrolytes in batteries.

Machine learning interatomic potentials (MLIPs) have become powerful tools to extend molecular simulations beyond the limits of quantum methods, offering near-quantum accuracy at much lower computational cost. Yet, developing reliable MLIPs remains difficult because it requires generating high-quality data sets, preprocessing atomic structures, and carefully training and validating models. In this work, we introduce an Automated Machine Learning Pipeline (AMLP) that unifies the entire workflow from data set creation to model validation. AMLP employs large-language-model agents to assist with electronic-structure code selection, input preparation, and output conversion, while its analysis suite (AMLP-Analysis) based on ASE supports a range of molecular simulations. The pipeline is built on the MACE architecture and validated on acridine polymorphs, where with a straightforward fine-tuning of a foundation model mean absolute errors of 1.7 meV/atom in energies and 7.0 meV/Å in forces are achieved. The fitted MLIP reproduces DFT geometries with sub-Å accuracy and demonstrates stability during molecular dynamics simulations in the microcanonical and canonical ensemble.

ABSTRACT Optically active tetrathiafulvalene (TTF) banded spherulite films comprising helicoidal fibrils exhibit an order of magnitude higher hole mobility compared to their unbanded counterparts. These mobilities of ∼10 −5 cm 2 V −1 s −1 are, however, low among organic semiconductors. We enhance the electrical conductivity of TTF banded spherulite films over seven orders of magnitude by iodine doping. Pale yellow films became dark red as TTF + formed in the presence of iodine vapor, with the local doping rate dependent on the crystal face exposed at the film surface. A six‐order‐of‐magnitude increase in conductivity is observed during the first two min of doping, reaching a maximum value of 0.7 ± 0.6 S cm −1 after 10 min. TTF 7 I 5 needles nucleated at the film surface and grew downwards during iodine vapor exposure, consuming β‐TTF helicoidal fibrils. The four principal linear optical anisotropies, linear and circular birefringence and dichroism, are mapped, and all four properties decreased over 10 min of iodine vapor exposure due to conversion to TTF 7 I 5. For short doping times, however, circular birefringence and dichroism remained unchanged. These results demonstrate that the conductivity of TTF banded spherulite films can be increased without disrupting the microstructure that gives rise to optical activity, expanding their utility in chiroptoelectronics.

The reliable self-assembly and structural programmability of the double helix has enabled the rational design of a wide range of DNA nanostructures and nanodevices. This includes tessellating DNA tiles that form 3D macroscopic crystals, which can be used to arrange periodic matter in three dimensions. Historically, the structural components of DNA tiles are predicated on the self-assembly of double-stranded DNA (dsDNA) components, owing to the predictable nature of the B-form duplex. In this study, we demonstrate that discrete single-stranded domains (SSDs) can exist continuously with dsDNA, with tile integrity enabled by topologically-enforced base stacking. Utilizing a variety of exposed Watson-Crick- Franklin faces, we facilitate time-resolved host-guest interactions between our crystal lattices and functionalized complementary oligomers. Furthermore, we demonstrate using X-ray diffraction that isothermal targeting of SSDs can induce reconfiguration of physical lattice properties without disrupting structural integrity. The ability to incorporate SSDs in three-dimensional lattices, to target these domains as organized binding sites, and to reconfigure the composition and properties of such lattices without dismantling their supramolecular structure will enable the investigation of several applications of single- stranded DNA within the tensegrity nanomaterial framework.

We present MXtalTools, a flexible Python package for the data-driven modelling of molecular crystals, facilitating machine learning studies of the molecular solid state. MXtalTools comprises several classes of utilities: (1) synthesis, collation, and curation of molecule and crystal datasets, (2) integrated workflows for model training and inference, (3) crystal parameterization and representation, (4) crystal structure sampling and optimization, (5) end-to-end differentiable crystal sampling, construction and analysis. Our modular functions can be integrated into existing workflows or combined and used to build novel modelling pipelines. MXtalTools leverages CUDA acceleration to enable high-throughput crystal modelling. The Python code is available open-source on our GitHub page, with detailed documentation on ReadTheDocs.

Cooperative gas adsorption in metal-organic frameworks (MOFs) is a rare phenomenon that generally involves long-range communication between multiple binding sites. We demonstrate a MOF containing cobalt(II)-methyl sites that selectively and reversibly capture two carbon monoxide (CO) molecules per site, leading to record-high adsorption capacities at ambient temperatures and pressures. Gas adsorption and structural, spectroscopic, and computational analyses support a mechanism in which binding of one CO molecule triggers a spin transition, followed by binding of a second CO molecule and migratory insertion of the first CO molecule into the cobalt-methyl bond to form an acetyl. The greater binding affinity associated with the second CO results in sigmoidal adsorption isotherms, a hallmark of cooperativity and phase-change materials, despite the absence of long-range interactions within the framework.

Sticky-ended cohesion has been the driving force for DNA self-assembly and has enabled model and design programmability in DNA nanotechnology for over 40 years. Traditional units within self-assembled crystals have rationally-designed sticky ends to avoid unpredictable packing behavior, but in doing so, the surprising variety of contact flavors available to natural nucleic acids remains unexploited. Here, we employ composable DNA tiles to form complex 3D architectures using blunt-ended motifs with single duplex interfaces, leveraging the geometry of the tile and the terminal nucleobase identity to control self-assembly outcomes. We establish programmability and tunable packing, obtaining both unusual and fundamental assemblies, including translational and inversion symmetries at the blunt ends, both 5'-3' and 5'-5' stacking, and both positive and negative twist values. These motifs self-assemble into seven crystallographic space groups, achieving diffraction from 1.86 to 10.0 Å. Finally, we establish the ability of racemic mixtures of L- and D- DNA motifs to perform programmable co-assembly driven by terminal π–π interactions, demonstrating molecular recognition and coexistence between mirror molecular systems. In sum, we demonstrate the ability to tune and program supramolecular assemblies of DNA relying solely on sequence-driven aromatic stacking and tile shape, obviating the need for hydrogen bond recognition between subunits.

Self-assembling DNA crystals have emerged over the last two decades as an efficient and effective means of organizing matter at the nanoscale, but functionalization of these lattices has proved challenging as physiological buffer conditions are required to maintain structural integrity. In this manuscript, we demonstrate the silicification of mesoporous DNA crystals using sol-gel chemistry. We identify reaction conditions that produce the minimum coating thickness to confer environmental protection, and we subsequently measure this protective ability to various stressors, including heat, low ionic strength solution, organic solvents, and unprotected freezing. By soaking metal ions and dyes into the lattice after silica coating, we demonstrate that the crystals maintain their pores and that the major groove of the DNA can still be used as a sequence-specific template for chemical reactions. We image a library of different crystal motifs by electron microscopy, and we perform X-ray diffraction on these crystals, both with and without cryoprotection, to determine the structure of the DNA frame, underscoring the conserved molecular order after coating. We anticipate these mesoporous silica composites will find use in applications involving extreme, nonphysiological conditions and in experiments which utilize the DNA glass described here as a template for chemical reactions on the internal surface of architected materials.

Hydrogen bonded electrolytes that exhibit accelerated proton transport via sequential reactive hops have drawn interest for their promise in clean energy applications. Molecular dynamics simulations of these electrolytes offer the opportunity to uncover microscopic mechanistic details that could be used to design and tune the properties of candidate electrolyte technologies. However, accurately modeling the proton transfer reactions and transport properties that give rise to high charge conductivites in these electrolytes proves computationally challenging because of the need to perform lengthy condensed phase simulations, treating both the electronic and nuclear degrees of freedom quantum mechanically. In this paper, we demonstrate that such a modeling task can be efficiently achieved with the use of density functional theory (DFT)-trained machine learning potentials (MLP) to accelerate path integral molecular dynamics (PIMD) simulations. We highlight the practical utility of this approach by using it to benchmark how closely PIMD simulations employing different DFT exchange-correlation functionals reproduce the composition-dependent densities, diffusion coefficients, and electrical conductivities of mixtures consisting of imidazole and levulinic acid. Even with the speedup afforded by our MLPs, PIMD simulations remain quite expensive. In order to render PIMD more computationally tractable, we introduce and benchmark the accuracy of a ring polymer contraction approach that leverages a computationally efficient short-range MLP to accelerate our PIMD simulations by an additional factor of four.

The jellium model is a paradigmatic problem in condensed matter physics, exhibiting a phase transition between metallic and Wigner crystal phases. However, its vanishing Berry curvature makes it ill suited for studying recent experimental platforms that combine strong interactions with nontrivial quantum geometry. These experiments inspired the anomalous Hall crystal (AHC)-a topological variant of the Wigner crystal. The AHC spontaneously breaks continuous translation symmetry but has a nonzero Chern number. In this Letter, we introduce λ-jellium, a minimal extension of the two-dimensional jellium model. Its Berry curvature distribution is controlled by a single parameter λ, where λ=0 corresponds to the standard jellium model. This setup facilitates the systematic exploration of Berry curvature's impact on electron crystallization. The phase diagram of this model, established using self-consistent Hartree Fock calculations, reveals several interesting features: (i) The AHC phase occupies a large region of the phase diagram. (ii) Two distinct Wigner crystal phases, the latter enabled by quantum geometry, and two distinct Fermi liquid phases are present. (iii) A continuous phase transition separates the AHC and one of the Wigner crystal phases. (iv) In some parts of the AHC phase, the lattice geometry is nontriangular, unlike in the classical Wigner crystal. In addition to elucidating the physics of correlated electrons with nonzero Berry curvature, we expect that the simplicity of the model makes it an excellent starting point for more advanced numerical methods.

Thin films of vanadium silicide (V-silicide) in the A15 cubic phase (V3Si) are promising for superconducting quantum devices due to their high transition temperature and potential compatibility with scalable semiconductor fabrication. However, solid-phase synthesis often yields secondary silicide phases that degrade performance. Here, we investigate the influence of substrate properties using two silicon-on-insulator architectures: one with a polycrystalline HfO2 buried layer (group A) and the other with amorphous SiO2 (group B). Both systems exhibit superconductivity consistent with V3Si formation, yet structural analysis reveals mixed-phase films in both cases. Crucially, only group A maintains an atomically sharp and chemically stable interface, a prerequisite for phase purity. Prolonged annealing in group A reduces the unwanted V5Si3 phase but also leads to the emergence of Si-rich VSi2, likely due to localized substrate degradation. Preliminary atomic-resolution imaging suggests that HfO2 crystallinity may promote local phase-selective nucleation. These findings highlight the importance of substrate design in promoting phase control and maintaining interfacial integrity in superconducting silicides.

Recent advances in 2D materials featuring nonzero Berry curvature have inspired extensions of the Wigner crystallization paradigm. This paper derives a low-energy effective theory for such quantum crystals, including the anomalous Hall crystal (AHC) with nonzero Chern number. First, we show that the low frequency dispersion of phonons in AHC, despite the presence of Berry curvature, resembles that of the zero field (rather than finite magnetic field) Wigner crystal due to the commutation of translation generators. We explain how key parameters of the phonon theory such as elastic constants and effective mass can be extracted from microscopic models, and apply them to two families of models: the recently introduced [Formula: see text]-jellium model and a model of rhombohedral multilayer graphene (RMG). In the [Formula: see text]-jellium model, we explore the energy landscape as crystal geometry shifts, revealing that AHC can become "soft" under certain conditions. This causes transitions in lattice geometry, although the quantized Hall response remains unchanged. Surprisingly, the Berry curvature seems to enhance the effective mass, leading to a reduction in phonon speed. For the AHC in RMG, we obtain estimates of phonon speed and shear stiffness. We also identify a previously overlooked "kineo-elastic" term in the phonon effective action that is present in the symmetry setting of RMG, and leads to dramatic differences in phonon speeds in opposite directions. We numerically confirm these predictions of the effective actions by time-dependent Hartree-Fock calculations.

ABT-333 and ABT-072 are two potent non-nucleoside NS5B polymerase inhibitors designed for the treatment of the hepatitis C virus (HCV). These structural analogs differ only by a minor substituent change, which disrupts the planarity of the naphthyl group on the ABT-333 compound through the addition of a more flexible trans-olefin substituent. However, this minor change leads to significant differences in their conformational preferences and intermolecular interactions, resulting in a ripple effect with drug development implications, ranging from crystal polymorphism and low aqueous solubility to formulation development challenges. In this article, we demonstrate how a suite of molecular simulation approaches, including crystal structure prediction augmented with a new hydrate CSP algorithm, free-energy perturbation, molecular dynamics (MD) based solubility predictions, and topological assessment to evaluate surface re-crystallization tendencies, provide key atomistic-level insights into the differentiated performance of the two analogs. Through this study, we establish the importance of end-to-end physics-based modeling, which involves explicit considerations of 3-D structure and crystal packing interactions. This approach provides structural and energetic insights into the physicochemical properties and drug development challenges faced when designing best-in-class drug molecules. ABT-333 and ABT-072 are non-nucleoside NS5B polymerase inhibitors for hepatitis C, differing by a minor substituent change that impacts their drug development profiles. Here, the authors use advanced molecular simulations, including crystal structure prediction augmented with a new hydrate CSP algorithm and advanced MD simulations, to reveal how this change affects conformational preferences and interactions, highlighting the importance of physics-based modeling in drug design.

An approach is introduced to reduce the computational cost associated with performing path integral simulations. This work is an extension of the ring-polymer contraction (RPC) approach of Markland and Manolopoulos [J. Chem. Phys. 129, 024105 (2008)], which was originally formulated for simulating closed ring-polymers via molecular dynamics using normal modes to transform the full ring into a contracted ring. This work considers several new contraction transformation schemes, specifically a transformation to the contracted ring employing staging variables, designated as staging RPC, and a transformation for open-chain path integrals used in the calculation of momentum-dependent properties and quantum time correlation functions, which we designate as staging open-polymer contraction (OPC). These approaches are shown to be useful for obtaining equilibrium and dynamical properties for systems ranging from one-dimensional model problems to three-dimensional gas-phase water clusters. Additionally, we show that the accuracy and efficiency of contraction approaches can be improved significantly via a simple reweighting scheme. The advantage of staging RPC/OPC over normal mode RPC is the ability to formulate all transformations as a set of a recursion relations rather than matrix multiplications or Fourier transforms, providing a computationally simpler approach that is as effective as normal mode based contraction.

Toxic per- and polyfluoroalkyl substances (PFAS) are now found in nearly every water source on the planet. Exposure to these molecules can have negative health consequences, but the low concentration of PFAS relative to other solutes in water makes their removal challenging. Adsorbents offer a promising treatment route, but often exhibit low selectivities and removal capacities, as well as slow kinetics. The performance in these metrics can be improved by chemically optimizing PFAS binding sites and maximizing PFAS-adsorbent interactions. To explore how to achieve this, a porous polymer network solid (PPN-6, also known as PAF-1) was postsynthetically modified with various chemical moieties capable of leveraging unique combinations of electrostatic, hydrogen-bonding, hydrophobic, and fluorophilic interactions with PFAS molecules. Batch adsorption experiments and computational studies revealed that electrostatic and hydrogen-bonding interactions drive short-chain PFAS adsorption, while hydrophobic and fluorophilic interactions improve long-chain PFAS adsorption. In complex water matrices, a combination of electrostatic and fluorophilic interactions led to the greatest total PFAS removal. The best-performing material, functionalized with a fluorinated alkylammonium (PPN-6-FNDMB), selectively adsorbs PFAS with high capacity (up to 4.0 mmol/g) and rapid kinetics (equilibrium reached in <30 s). Furthermore, PPN-6-FNDMB outperforms several commercial adsorbents, achieving near-complete removal of 21 different PFAS from a groundwater sample collected at a US Air Force base. The PFAS could subsequently be desorbed from PPN-6-FNDMB, concentrating them by a factor of over 50 times. The recycled PPN-6-FNDMB could then be reused with minimal losses in long-chain PFAS adsorption capacity over four cycles.

DNA nanotechnology leverages the molecular design resolution of the DNA double helix to fold and tile matter into designer architectures. Recent advances in bioinorganic chemistry have exploited the affinity of soft nucleobase functional groups for silver ions in order to template the growth of silver nanoclusters by templated reduction. The coupling of the spatial resolution of DNA nanotechnology and the atomic precision of DNA- based nanocluster synthesis has not been realized. Here we develop a method using 3D DNA crystals to employ silver-ion-mediated base pairs as nucleation sites for atomically- precise nanocluster growth. By leveraging the topology of DNA tensegrity triangles, we provide a mesoporous 3D lattice that is robust to reducing conditions, enabling precise spatial templating. Use of in situ confocal fluorescence microscopy allows for the direct observation of reaction kinetics and reconstruction of the optical bandgap. Control over reaction time and stoichiometry, base pair identity, and buffer composition enable precise tuning of the atomic composition and optical properties of the ensuing nanoclusters. The resulting crystals are of diffraction quality, yielding molecular structures of Ag4 and Ag6 in 3D. Inter-cluster distances of less than 2 nm show strong plasmonic coupling, with red shifting observed relative to literature standards. A thorough computational investigation establishes a theoretical basis for our observed behavior, and establishes the interplay between cluster size, charge, geometry, and resonance. We anticipate that these results will yield advances in materials synthesis, DNA-based plasmonic crystals, and optically-active nanoelectronics

Self-assembling DNA crystals have emerged over the last two decades as an efficient and effective means of organizing matter at the nanoscale, but functionalization of these lattices has proved challenging as physiological buffer conditions are required to maintain structural integrity. In this manuscript, we demonstrate the silicification of porous DNA crystals using sol-gel chemistry. We identify reaction conditions that produce the minimum coating thickness to confer environmental protection, and subsequently measure the protective ability of the silica coating to various stressors, including heat, low ionic strength solution, organic solvents, and unprotected flash freezing. By soaking ions and dyes into the lattice after silica coating, we demonstrate that the crystals maintain their pores, and that the major groove of the DNA can still be used as a site-specific template for chemical modifications. We image a library of different crystal motifs by electron microscopy and confirm the presence of silica using energy dispersive spectroscopy. Finally, we perform X-ray diffraction on these crystals, both with and without cryoprotection and determine the structure of the DNA frame, underscoring the conserved molecular order after coating. We anticipate these mesoporous silica composites for use in applications involving extreme, non-physiological conditions and for experiments which utilize the DNA glass described here as a template for surface science.

Abstract Photoconductive nanomaterials are critical in the development of advanced optoelectronics, which span photovoltaics to biomedicine. These materials are often derived from inorganic, molecular, and polymeric crystalline semiconductors that facilitate charge transfer upon absorption of ultraviolet and near infrared light. These types of materials are broadened to include single‐domain protein‐based nanofibers. Coiled‐coil protein domains found in nature transport electrons when possessing pi‐stacked aromatic rings and undergo supramolecular assembly into fibers. Whereas conductive protein nanofibers have previously been leveraged for high‐resistance organic materials, a conductive helical assembled fiber (CHAF) is reported, composed of phenylalanines in the core capable of photoresponsivity. It is demonstrated that CHAF and a leucine‐replaced CHAF control (L‐CHAF) exhibit distinct photoconductive responses to near infrared (NIR) light. The sequence‐controlled system reported here illustrates photoconductive protein fibers as a promising platform for the next generation of new biocompatible nanomaterials.

Nuclear speckles are membraneless organelles implicated in multiple RNA processing steps. In this work, we systematically characterize the sequence logic determining RNA localization to nuclear speckles. We find extensive similarities between the speckle localization code and the RNA splicing code, even for transcripts that do not undergo splicing. Specifically, speckle localization is enhanced by the presence of unspliced exon-like or intron-like sequence features. We demonstrate that interactions required for early splicesomal complex assembly contribute to speckle localization. We also show that speckle localization of isolated endogenous exons is reduced by disease-associated single nucleotide variants. Finally, we find that speckle localization strongly correlates with splicing kinetics of splicing-competent constructs and is tightly linked to the decision between exon inclusion and skipping. Together, these results suggest a model in which RNA speckle localization is associated with the formation of the early spliceosomal complex and enhances the efficiency of splicing reactions. Highlights: Sequences containing hallmarks of pre-mRNA dictate speckle localizationRNA speckle localization is coupled to early spliceosome assemblyDisease-associated single nucleotide variants reduce localization of isolated exonsRNA speckle localization strongly correlates with splicing kinetics.

High Resolution Image Download MS PowerPoint Slide Chiral halide perovskites (c-HPs) merge the chirality of organic cations with the semiconducting properties of metal halide frameworks, creating a family of chiral semiconductors with tunable chiroptoelectronic behavior. Here, we describe the impact of periodic banded morphologies of textured c-HP (R/S-NEA) 2 PbBr 4 films (NEA = 1-(1-naphthyl)ethylammonium) on their chiroptical behavior. Due to the interplay between the crystalline and glassy phases, the c-HP film growth is driven by rhythmic precipitation, producing a distinctive controllable radial banded pattern with the (R/S-NEA) 2 PbBr 4 inorganic planes oriented parallel to the substrate. The banded morphology can be controlled, as evidenced by the growth temperature dictating the ridge-to-ridge spacing as well as the density of banded regions. The resulting circular dichroism (CD) spectral shape, intensity, and polarity vary in a seemingly random manner across processing conditions. However, these spectral features can be explained by considering key features of the banded morphology, such as refraction of the incident light due to surface morphology, birefringence, and stacked, rotated crystallites. These effects cannot be canceled by averaging front and back CD spectra of c-HP films, and our model incorporating these effects reproduces all observed CD spectra remarkably well. The control over the c-HP morphology and prediction capabilities of our CD modeling leads to further understanding of this class of semiconductors and the possibility of exploiting structural features for light polarization control akin to enhanced metamaterials.

Abstract The rational design of molecular electronics remains a grand challenge of materials science. DNA nanotechnology has offered unmatched control over molecular geometry, but direct electronic functionalization is a challenge. Here a generalized method is presented for tuning the local band structure of DNA using transmetalation in metal‐mediated base pairs (mmDNA). A method is developed for time‐resolved X‐ray diffraction using self‐assembling DNA crystals to establish the exchange of Ag + and Hg 2+ in T:T base pairs driven by pH exchange. Transmetalation is tracked over six reaction phases as crystal pH is changed from pH 8.0 to 11.0, and vice versa. A detailed computational analysis of the electronic configuration and transmission in the ensuing crystal structures is then performed. This findings reveal a high conductance contrast in the lowest unoccupied molecular orbitals (LUMO) as a result of metalation. The ability to exchange single transition metal ions as a result of environmental stimuli heralds a means of modulating the conductance of DNA‐based molecular electronics. In this way, both theoretical and experimental basis are established by which mmDNA can be leveraged to build rewritable memory devices and nanoelectronics.

High Resolution Image Download MS PowerPoint Slide Nanoconfining crystallization to access metastable polymorphs and prescribe crystal orientations typically involves filling inert nanoporous scaffolds with target compounds, resulting in isolated nanocrystals. Such crystal-scaffold composites are unsuitable for optoelectronic devices that require interconnected crystalline pathways for charge transport. Here, we reverse the order of fabricating crystal-scaffold composites by first electrospinning interconnected networks of amorphous methylammonium lead iodide (MAPbI 3) precursor nanofibers, then introducing a poly(methyl methacrylate) (PMMA) scaffold by spin coating from an antisolvent for MAPbI 3. PMMA suppresses MAPbI 3 crystal blooming from the fiber surface during thermal annealing, instead promoting the formation of densely packed polycrystalline networks of MAPbI 3 crystals at the fiber/PMMA interface. Near-IR photodetectors comprising densely packed MAPbI 3 nanocrystals grown within a PMMA scaffold in a coplanar electrode geometry exhibit photocurrents up to 60 times larger than those comprising fibers annealed without PMMA. These results indicate that MAPbI 3 crystals form a percolated network for charge carriers to flow through PMMA-confined fibers, resulting in significantly improved photodetector performance.

We demonstrate the possibility of covalently bonded hybrid DNA–graphene materials by synthesizing a model DNA–polycyclic aromatic hydrocarbon (PAH) conjugate comprising a 33mer oligonucleotide containing thymine and uridine modified with bispyrenyl benzene. This DNA–PAH conjugate (T 13 U PAH T 19; T = thymine, U PAH = PAH-modified uridine) has an atomically thin nanographene protrusion extending by only about 1 nm from the single-stranded DNA (ssDNA). We show that DNA–PAH conjugates can be characterized with high resolution by profiling with a nanopore in a monolayer MoS 2 membrane. The profiling experiments provided sufficient resolution to distinguish the thymine and PAH-modified regions of T 13 U PAH T 19 and confirm the asymmetry of the PAH attachment relative to the 3′ and 5′ ends of the ssDNA due to different lengths of the T 13 and T 19 segments. This work provides the foundation for further exploration of DNA–graphene hybrids, demonstrating an example of their synthesis and the utility of nanopore profiling for their structural characterization with an ∼1 nm resolution.

High Resolution Image Download MS PowerPoint Slide Engineering the electronic band structure of two-dimensional (2D) materials by imposing spatially periodic superlattice (SL) potentials opens a pathway to unconventional electronics. Nanopatterning the gate electrode or surface dielectric near 2D crystals provides a powerful strategy for realizing electrostatically tunable “remote” SLs with flexibility in lattice design. Here, we demonstrate the effectiveness of block copolymer (BCP)-templated dielectric nanopatterns for fabricating etch-free high-grade metal oxide SLs. Alumina (AlO x) nanopatterns with hexagonal symmetry and a 38 nm SL wavelength are produced as a model material by directly converting a self-assembled BCP film via block-selective vapor phase infiltration. Despite micrometer-scale rotational disorder inherent to BCP self-assembly, electronic transport measurements of graphene reveal replica Dirac points at zero field and Hofstadter mini-gaps under finite magnetic fields. These results indicate the successful formation of remote SL potentials in graphene resulting from optimized AlO x nanopattern fabrication to achieve consistent lattice symmetry and periodicity at a macroscopic scale. The findings of this study, combined with the versatile, scalable, and cost-effective nature of BCP nanopatterning, highlight the potential of BCP-templated nanostructures for remote SL engineering in 2D crystals.

High Resolution Image Download MS PowerPoint Slide Room-temperature ionic liquids (RTILs) represent a versatile class of chemical systems composed entirely of oppositely charged species whose bulk properties can be fine-tuned by adjusting molecular structures and, consequently, intermolecular interactions. Understanding the intricate dynamics between ionic species can aid in the rational design of RTILs for specific applications in a range of fields, including catalysis and electrochemistry. Here, we investigate the temperature dependence of intermolecular interactions through magnetization transfer by means of 1 H– 19 F heteronuclear Overhauser effect spectroscopy (HOESY) for two ionic liquids, namely, [BMIM][BF 4] and [BMIM][PF 6]. We find that the cross-relaxation rates vary significantly over a rather small temperature range, even changing sign. Molecular dynamics (MD) simulations on neat RTIL systems replicate this behavior well and further show that the dynamic properties rather than coordination changes of RTILs account for the observed temperature behavior. Furthermore, the investigation of different coordination shells highlights the change of interaction range with temperature even to the point where inner and outer coordination shells could be in distinct motional regimes with cross-relaxation rates of opposite sign. Since temperature changes lead primarily to dynamic changes rather than structural ones, these findings underscore the versatility and high thermal stability of ionic liquids.

Electrosynthesis at an industrial scale offers an opportunity to use renewable electricity in chemical manufacturing, accelerating the decarbonization of large-scale chemical processes. Organic electrosynthesis can improve product selectivity, reduce reaction steps, and minimize waste byproducts. Electrochemical synthesis of adiponitrile (ADN) via hydrodimerization of acrylonitrile (AN) is a prominent example of industrial organic electrochemical processes, with annual production reaching 0.3 MMT. It circumvents the drawbacks of thermochemical synthesis by reducing toxicity and leveraging clean electricity as an energy source. Despite its industrial importance, mechanistic understanding and experimental insights on the near-electrode molecular processes of AN electrohydrodimerization remain insufficient. Here we show, using in situ ATR-FTIR spectroscopy, that tetraalkylammonium ions populate the electrical double layer (EDL), creating a microenvironment that favors interactions with organic molecules and enhances AN concentration while expelling water molecules. Our results provide experimental evidence supporting long-standing mechanistic hypotheses. Kinetic isotope effect studies reveal that propionitrile (PN) formation is rate-limited by proton transfer, while ADN formation likely is not. Electron paramagnetic resonance spectroscopy confirms the presence of free radicals during AN electroreduction, suggesting that coupling of PN radicals occurs primarily in the electrolyte. These insights highlight the importance of carefully controlling the EDL composition for selective organic electrosynthesis and provide fundamental engineering guidance for designing high-performing electro-organic reactions. We anticipate these findings will guide the optimization of electrolyte formulations and electrode interfaces for ADN synthesis and other emerging electro-organic processes.

Transformation of optically active (G) 2 (1,5-NDS)⊃EtOH banded spherulites to guest-free (G) 2 (1,5-NDS) straight crystals upon heating.

This repository contains the datasets, figures, and analysis files supporting the manuscript Structured Electrolytes Facilitate Grotthuss-type Enhanced Proton Coupled Electron Transfer Reactions. The data include experimental measurements and computational results used to investigate proton transport, hydrogen-bond network structure, and electrochemical kinetics in imidazole–acid structured electrolytes.

Room-temperature ionic liquids (RTIL) represent a versatile class of chemical systems, comprised only of oppositely charged species, whose bulk properties can be fine-tuned by adjusting molecular structures and, consequently, intermolecular interactions. Understanding the intricate dynamics between the two ionic species can aid the rational design of RTIL as electrolytes facilitating electron- or proton-transfer reactions useful for energy applications. Here, we investigate the temperature dependency of the intermolecular interactions via magnetization transfer between oppositely charged ions by means of 1H-19F heteronuclear Overhauser effect spectroscopy (HOESY) for two ionic liquids, namely [BMIM][BF4] and [BMIM][PF6]. We find that cross-relaxation rates vary significantly over a rather small temperature range, crossing the null point and changing sign. Other NMR observables such as chemical shifts, scalar couplings or auto-relaxation rates are less affected by temperature, making intermolecular Overhauser transfer a sensitive tool to study the dynamics and especially intermolecular interactions in RTILs. Molecular Dynamics (MD) simulations on neat RTILs systems were performed to identify the origin of the observed behavior. Good agreement between simulated and experimental cross-relaxation rates was found at different temperatures. On this basis, we could attribute the observed temperature behavior to the modulation of dynamic properties rather than coordination changes of RTILs. Specifically, it is the change in relative diffusion coefficients that describes the temperature behavior of internuclear interactions, rather than the distance of closest approach. This information underscores the versatility and high thermal stability of ionic liquids.

Anomalous Hall crystals (AHCs) form a new phase of matter with spontaneous crystallization and quantized Hall response. It has been invoked to explain a recent experiment on rhombohedral pentalayer graphene, but a simple conceptual understanding of its existence has been lacking. Here, the authors propose a simple three-patch model that captures how quantum mechanical exchange interactions can stabilize the AHC phase, and apply it to analyze the phenomenology of rhombohedral pentalayer graphene.

Organic molecular crystals constitute a class of materials of critical importance in numerous industries. Despite the ubiquity of these systems, our ability to predict molecular crystal structures starting only from a two-dimensional diagram of the constituent compound(s) remains a significant challenge. Most structure-prediction protocols require a customized interatomic interaction model on which the quality of the results can depend sensitively. To overcome this problem, we introduce a new topological approach to molecular crystal structure prediction. The approach posits that in a stable structure, molecules are oriented such that principal axes and normal ring plane vectors are aligned with specific crystallographic directions and that heavy atoms occupy positions that correspond to minima of a set of geometric order parameters. By minimizing an objective function that encodes these orientations and atomic positions, and filtering based on the vdW free volume and intermolecular close contact distributions derived from the Cambridge Structural Database, stable structures and polymorphs for a given crystal can be predicted entirely mathematically without reliance on an interaction model.

Nuclear speckles are nuclear membraneless organelles in higher eukaryotic cells playing a vital role in gene expression. Using an in situ reverse transcription-based sequencing method, we study nuclear speckle-associated human transcripts. Our data indicate the existence of three gene groups whose transcripts demonstrate different speckle localization properties: stably enriched in nuclear speckles, transiently enriched in speckles at the pre-messenger RNA stage, and not enriched. We find that stably enriched transcripts contain inefficiently excised introns and that disruption of nuclear speckles specifically affects splicing of speckle-enriched transcripts. We further reveal RNA sequence features contributing to transcript speckle localization, indicating a tight interplay between transcript speckle enrichment, genome organization, and splicing efficiency. Collectively, our data highlight a role of nuclear speckles in both co- and posttranscriptional splicing regulation. Last, we show that genes with stably enriched transcripts are over-represented among genes with heat shock-up-regulated intron retention, hinting at a connection between speckle localization and cellular stress response.

Electrosynthesis at an industrial scale offers an opportunity to use renewable electricity in chemical manufacturing, accelerating the decarbonization of large-scale chemical processes. Organic electrosynthesis can improve product selectivity, reduce reaction steps, and minimize waste byproducts. Electrochemical synthesis of adiponitrile (ADN) via hydrodimerization of acrylonitrile (AN) is a prominent example of industrial organic electrochemical processes. It circumvents the drawbacks of thermochemical synthesis by reducing toxicity and leveraging clean electricity as an energy source. Despite its industrial importance, mechanistic understanding and experimental insights on the near-electrode molecular processes of AN electrohydrodimerization remain insufficient. Here we show, using in-situ ATR-FTIR spectroscopy, that tetraalkylammonium ions populate the electrical double layer (EDL), creating a microenvironment that favors interactions with organic molecules and enhances AN concentration while expelling water molecules. Our results provide experimental evidence supporting long-standing mechanistic hypotheses. Kinetic isotope effect studies reveal that propionitrile (PN) formation is rate-limited by proton transfer, while ADN formation likely is not. Electron paramagnetic resonance spectroscopy confirms the presence of free radicals during AN electroreduction, suggesting that coupling of PN radicals occurs primarily in the electrolyte. These insights highlight the importance of carefully controlling the EDL composition for selective organic electrosynthesis and provide fundamental engineering guidance for designing high-performing electro-organic reactions. We anticipate these findings will guide the optimization of electrolyte formulations and electrode interfaces for ADN synthesis and other emerging electro-organic processes.

Identifying local structural motifs and packing patterns of molecular solids is a challenging task for both simulation and experiment. We demonstrate two novel approaches to characterize local environments in different polymorphs of molecular crystals using learning models that employ either flexibly learned or handcrafted molecular representations. In the first case, we follow our earlier work on graph learning in molecular crystals, deploying an atomistic graph convolutional network combined with molecule-wise aggregation to enable per-molecule environmental classification. For the second model, we develop a new set of descriptors based on symmetry functions combined with a point-vector representation of the molecules, encoding information about the positions and relative orientations of the molecule. We demonstrate very high classification accuracy for both approaches on urea and nicotinamide crystal polymorphs and practical applications to the analysis of dynamical trajectory data for nanocrystals and solid-solid interfaces. Both architectures are applicable to a wide range of molecules and diverse topologies, providing an essential step in the exploration of complex condensed matter phenomena.

High Resolution Image Download MS PowerPoint Slide A previously unreported polymorph of 5,11-bis(triisopropylsilylethynyl)anthradithiophene (TIPS ADT), Form II, crystallizes from melt-processed TIPS ADT films blended with 16 ± 1 wt % medium density polyethylene (PE). TIPS ADT/PE blends that initially are crystallized from the melt produce twisted TIPS ADT crystals of a metastable polymorph (Form IV, space group P 1̅) with a brickwork packing motif distinct from the slipstack packing by solution-processed TIPS ADT crystals (Form I, space group P 2 1 / c) at room temperature. When these films were cooled to room temperature and subsequently annealed at 100 °C, near a PE melting temperature of 110 °C, Form II crystals nucleated and grew while consuming Form IV. The growth rate and orientations of Form II crystals were predetermined by the twisting pitch and growth direction of the original banded spherulites in the melt-processed films of the blends. Notably, the Form IV → II transition was not observed during thermal annealing of neat TIPS ADT films without PE. The presence of the mobile PE phase during thermal annealing of TIPS ADT/PE blend films increases the diffusion rate of TIPS ADT molecules, and the rate of nucleation of Form II. Form IV crystals are more conductive but less emissive compared to Form II crystals.

Hexagonal boron nitride (hBN) is attracting increasing attention for quantum information science due to its ability to host carbon-related color centers that perform as robust, high-temperature quantum light sources, as well as native defects such as charged V B – centers with optically addressable spin states toward spin-based quantum applications. So far, achieving isolation of individual V B – defects out of ensemble emission remains difficult due to their low quantum yield, warranting the search for other candidates. Here, we show that oxygen annealing creates individual quantum emitters characterized by a phonon-sideband-free emission in the 800 nm band. The emission is strongly linearly polarized (79%), with a characteristic emission dipole rotation of 20° and a saturation intensity around 1 MHz, comparable to the brightest hBN quantum emitters reported previously. Their time dynamics appear free of spectral diffusion or blinking, implying excellent room-temperature photostability without additional passivation techniques. Detailed cryogenic studies estimate zero pump power line width down to 87.5 μeV, which is several orders of magnitude narrower compared to carbon-related or V B – defect center emission under nonresonant excitation. The demonstrated photophysical properties of oxygen-related quantum emitters are promising to advance free-space quantum communication and might enable indistinguishable single photons or interfacing with 87 Rb vapor-based quantum memory technologies in future work.

The study of electrolytic solutions is of relevance in many research fields, ranging from biophysics, materials, and colloid science to catalysis and electrochemistry. The dependence of solution dynamics on the nature of electrolytes and their concentrations has been the subject of many experimental and computational studies, yet it remains challenging to obtain a full understanding of the factors that govern solution behavior. Here, we provide additional insights into the behavior of aqueous solutions of alkali chlorides by combining 17O relaxation data with diffusion and viscosity data and contrast their behavior with 1H nuclear magnetic resonance relaxation data. The main findings are that 17O relaxation correlates well with viscosity data but not with diffusion data, while 1H relaxation correlates with neither. Certain ionic trends match known ion-specific series behavior, especially at high concentrations. Notably, we also examine the ranges of the interactions and conclude that the majority of the effects are tied to local water reorientation dynamics.

RNA molecules often play critical roles in assisting the formation of membraneless organelles in eukaryotic cells. Yet, little is known about the organization of RNAs within membraneless organelles. Here, using super-resolution imaging and nuclear speckles as a model system, we demonstrate that different sequence domains of RNA transcripts exhibit differential spatial distributions within speckles. Specifically, we image transcripts containing a region enriched in binding motifs of serine/arginine-rich (SR) proteins and another region enriched in binding motifs of heterogeneous nuclear ribonucleoproteins (hnRNPs). We show that these transcripts localize to the outer shell of speckles, with the SR motif-rich region localizing closer to the speckle center relative to the hnRNP motif-rich region. Further, we identify that this intra-speckle RNA organization is driven by the strength of RNA-protein interactions inside and outside speckles. Our results hint at novel functional roles of nuclear speckles and likely other membraneless organelles in organizing RNA substrates for biochemical reactions.

A novel approach to computationally enhance the sampling of molecular crystal structures is proposed and tested. This method is based on the use of extended variables coupled to a Monte Carlo based crystal polymorph generator. Inspired by the established technique of quasi-random sampling of polymorphs using the rigid molecule constraint, this approach represents molecular clusters as extended variables within a thermal reservoir. Polymorph unit-cell variables are generated using pseudo-random sampling. Within this framework, a harmonic coupling between the extended variables and polymorph configurations is established. The extended variables remain fixed during the inner loop dedicated to polymorph sampling, enforcing a stepwise propagation of the extended variables to maintain system exploration. The final processing step results in a polymorph energy landscape, where the raw structures sampled to create the extended variable trajectory are re-optimized without the thermal coupling term. The foundational principles of this approach are described and its effectiveness using both a Metropolis Monte Carlo type algorithm and modifications that incorporate replica exchange is demonstrated. A comparison is provided with pseudo-random sampling of polymorphs for the molecule coumarin. The choice to test a design of this algorithm as relevant for enhanced sampling of crystal structures was due to the obvious relation between molecular structure variables and corresponding crystal polymorphs as representative of the inherent vapor to crystal transitions that exist in nature. Additionally, it is shown that the trajectories of extended variables can be harnessed to extract fluctuation properties that can lead to valuable insights. A novel thermodynamic variable is introduced: the free energy difference between ensembles of Z' = 1 and Z' = 2 crystal polymorphs.

High Resolution Image Download MS PowerPoint Slide Nanoconfined anion exchange membranes (AEMs) play a vital role in emerging electrochemical technologies. The ability to control dominant hydroxide diffusion pathways is an important goal in the design of nanoconfined AEMs. Such control can shorten hydroxide transport pathways between electrodes, reduce transport resistance, and enhance device performance. In this work, we propose an electrostatic potential (ESP) approach to explore the effect of the polymer electrolyte cation spacing on hydroxide diffusion pathways from a molecular perspective. By exploring cation ESP energy surfaces and validating outcomes through prior ab initio molecular dynamics simulations of nanoconfined AEMs, we find that we can achieve control over preferred hydroxide diffusion pathways by adjusting the cation spacing. The results presented in this work provide a unique and straightforward approach to predict preferential hydroxide diffusion pathways, enabling efficient design of highly conductive nanoconfined AEM materials for electrochemical technologies.

Helicoidal crystallites in rhythmically banded spherulites manifest spectacular optical patterns in small molecules and polymers. It is shown that concentric optical bands indicating crystallographic orientations typically lose coherence (in-phase twisting) with growth from the center of nucleation. Here, coherence is shown to increase as the twist period decreases for seven molecular crystals grown from the melt. This dependence was correlated to crystallite fiber thickness and length, as well as crystallite branching frequency, a parameter that was extracted from scanning electron micrographs, and supported by numerical simulations. Hole mobilities for 2,5-didodecyl-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DPP-C12) measured by using organic field-effect transistors demonstrated that more incoherent boundaries between optical bands in spherulites lead to higher charge transport for films with the same twist period. This was rationalized by combining our growth model with electrodynamic simulations. This work illustrates the emergence of complexity in crystallization processes (spherulite formation) that arises in the extra variable of helicoidal radial twisting. The details of the patterns analyzed here link the added complexity in crystal growth to the electronic and optical properties of the thin films.

Metal halide perovskite crystals grown on close-packed titanium dioxide colloidal monolayers exhibit hopper-like 3D morphologies, with growth initially directed vertically from the substrate before transitioning to the parallel direction.

The dynamic interplay between a copper electrode and a reactive ionic liquid is illustrated in the cover picture, showcasing key components in the electrochemical reduction of CO2. The role of the cation in covering the electrode surface and the in-situ generated hydrogen bond donor from CO2 binding to the ionic liquid in enhancing the kinetics were uncovered by in-situ spectroscopy, complemented by electroanalytical and computational methods. Multi-carbon products with reduced reaction energy were obtained, as reported by Burcu Gurkan et al. in their Research Article (e202312163). Cover image credit: Miguel Munoz.

The dynamic interplay between a copper electrode and a reactive ionic liquid is illustrated in the cover picture, showcasing key components in the electrochemical reduction of CO2. The role of the cation in covering the electrode surface and the in-situ generated hydrogen bond donor from CO2 binding to the ionic liquid in enhancing the kinetics were uncovered by in-situ spectroscopy, complemented by electroanalytical and computational methods. Multi-carbon products with reduced reaction energy were obtained, as reported by Burcu Gurkan et al. in their Research Article (e202312163). Cover image credit: Miguel Munoz.

Abstract Electrochemical CO 2 reduction (CO 2 RR) on copper (Cu) shows promise for higher‐value products beyond CO. However, challenges such as the limited CO 2 solubility, high overpotentials, and the competing hydrogen evolution reaction (HER) in aqueous electrolytes hinder the practical realization. We propose a functionalized ionic liquid (IL) which generates ion‐CO 2 adducts and a hydrogen bond donor (HBD) upon CO 2 absorption to modulate CO 2 RR on Cu in a non‐aqueous electrolyte. As revealed by transient voltammetry, electrochemical impedance spectroscopy (EIS), and in situ surface‐enhanced Raman spectroscopy (SERS) complemented with image charge augmented quantum‐mechanical/molecular mechanics (IC‐QM/MM) computations, a unique microenvironment is constructed. In this microenvironment, the catalytic activity is primarily governed by the IL and HBD concentrations; former controlling the double layer thickness and the latter modulating the local proton availability. This translates to ample CO 2 availability, reduced overpotential, and suppressed HER where C 4 products are obtained. This study deepens the understanding of electrolyte effects in CO 2 RR and the role of IL ions towards electrocatalytic microenvironment design.

Abstract Electrochemical CO2 reduction (CO2RR) on copper (Cu) shows promise for higher‐value products beyond CO. However, challenges such as the limited CO2 solubility, high overpotentials, and the competing hydrogen evolution reaction (HER) in aqueous electrolytes hinder the practical realization. We propose a functionalized ionic liquid (IL) which generates ion‐CO2 adducts and a hydrogen bond donor (HBD) upon CO2 absorption to modulate CO2RR on Cu in a non‐aqueous electrolyte. As revealed by transient voltammetry, electrochemical impedance spectroscopy (EIS), and in situ surface‐enhanced Raman spectroscopy (SERS) complemented with image charge augmented quantum‐mechanical/molecular mechanics (IC‐QM/MM) computations, a unique microenvironment is constructed. In this microenvironment, the catalytic activity is primarily governed by the IL and HBD concentrations; former controlling the double layer thickness and the latter modulating the local proton availability. This translates to ample CO2 availability, reduced overpotential, and suppressed HER where C4 products are obtained. This study deepens the understanding of electrolyte effects in CO2RR and the role of IL ions towards electrocatalytic microenvironment design.

Abstract Phosphate is an essential anion in the human body, comprising approximately 1% of the total body weight, and playing a vital role in metabolism, cell membranes, and bone formation. We have recently provided spectroscopic, microscopic, and computational evidence indicating that phosphates can aggregate much more readily in solution than previously thought. This prior work provided indirect evidence through the observation of unusual P NMR relaxation and line‐broadening effects with increasing temperature. Here, we show that, under conditions of slow exchange and selective RF saturation, additional features become visible in chemical exchange saturation transfer (CEST) experiments, which appear to be related to the previously reported phosphate clustering. In particular, CEST shows pronounced dips several ppm upfield of the main phosphate resonance at low temperatures, while direct P spectroscopy does not produce any signals in that range. We study the pH dependence of these new spectroscopic features and present exchange and spectroscopic parameters based on fitting the CEST data. These findings could be of importance in the investigation of phosphate dynamics, especially in the biological milieu.

Tetrathiafulvalene (TTF) crystals grown from the melt are organized as spherulites in which helicoidal fibrils growing radially from the nucleation center twist in concert with one another. Alternating bright and dark concentric bands are apparent when films are viewed between crossed polarizers, indicating an alternating pattern of crystallographic faces exposed at the film surface. Band-dependent reorganization of the TTF crystals was observed during exposure to methanol vapor. Crystalline growth appears on bright bands at the expense of the dark bands. After a 24 h period of exposure to methanol vapor, the original spherulites were completely restructured, and the films comprise isolated, concentric circles of crystallites whose orientations are determined by the initial TTF crystal fibril orientation. While the surface of these outgrowths appears faceted and smooth, cross-sectional SEM images revealed a semiporous inner structure, suggesting solvent-vapor-induced recrystallization. Collectively, these results show that crystal twisting can be used to rhythmically redistribute material. Crystal twisting is a common and often controllable phenomenon independent of molecular or crystal structure and therefore offers a generalizable path to spontaneous pattern formation in a wide range of materials.

Metal-mediated DNA (mmDNA) presents a pathway toward engineering bioinorganic and electronic behavior into DNA devices. Many chemical and biophysical forces drive the programmable chelation of metals between pyrimidine base pairs. Here, we developed a crystallographic method using the three-dimensional (3D) DNA tensegrity triangle motif to capture single- and multi-metal binding modes across granular changes to environmental pH using anomalous scattering. Leveraging this programmable crystal, we determined 28 biomolecular structures to capture mmDNA reactions. We found that silver(I) binds with increasing occupancy in T-T and U-U pairs at elevated pH levels, and we exploited this to capture silver(I) and mercury(II) within the same base pair and to isolate the titration points for homo- and heterometal base pair modes. We additionally determined the structure of a C-C pair with both silver(I) and mercury(II). Finally, we extend our paradigm to capture cadmium(II) in T-T pairs together with mercury(II) at high pH. The precision self-assembly of heterobimetallic DNA chemistry at the sub-nanometer scale will enable atomistic design frameworks for more elaborate mmDNA-based nanodevices and nanotechnologies.

ions between pyrimidine:pyrimidine pairs with the promise of nanoelectronics. Rational design of mmDNA nanomaterials is impractical without a complete lexical and structural description. Here, the programmability of structural DNA nanotechnology toward its founding mission of self-assembling a diffraction platform for biomolecular structure determination is explored. The tensegrity triangle is employed to build a comprehensive structural library of mmDNA pairs via X-ray diffraction and generalized design rules for mmDNA construction are elucidated. Two binding modes are uncovered: N3-dominant, centrosymmetric pairs and major groove binders driven by 5-position ring modifications. Energy gap calculations show additional levels in the lowest unoccupied molecular orbitals (LUMO) of mmDNA structures, rendering them attractive molecular electronic candidates.

Abstract Porous organic polymers (POPs) have gained tremendous attention owing to their chemical tunability, stability and high surface areas. Whereas there are several examples of fully conjugated two‐dimensional (2D) POPs, three‐dimensional (3D) ones are rather challenging to realize in the absence of structural templates. Herein, we report the base‐catalyzed direct synthesis of a fully conjugated 3D POPs, named benzyne‐derived polymers (BDPs), containing biphenylene and tetraphenylene moieties starting from a simple bisbenzyne precursor, which undergoes [2+2] and [2+2+2+2] cycloaddition reactions to form BDPs primarily composed of biphenylene and tetraphenylene moieties. The resulting polymers exhibited ultramicroporous structures with surface areas up to 544 m2 g−1 and very high CO2/N2 selectivities.

Abstract Recently, the application of magnetic fields to chiral chemical systems has been rewarding. In a forward‐looking 1986 paper, ‘Chiral Metals?’, Wallis, Karrer, and Jack D. Dunitz forecast ‘that the limitation to proper symmetry elements in a chiral conductor could be associated with the emergence of new properties, those connected with interactions between applied electric and magnetic fields and their internal counterparts.’ This was a prescient remark, but it has become manifest in ways that would not have been foreseen in its details by the authors. Here are reviewed the development of chiral conductors broadly imagined by Dunitz and coworkers, based on enantiopure tetrathiafulvalene derivatives that restrict space groups to those that have only symmetry operations of the first kind, as well as the new emergent properties associated with the transport of electrons when magnetic fields are applied to chiral crystals among other systems. These include electrical magnetochiral anisotropy (eMChA), inverse electrical magnetochiral anisotropy (ieMChA), helimagnetism and chirality induced spin selectivity (CISS). The conclusion discussing the circumstances under which achiral TTF crystals becomes chiral, only seems to introduce an oxymoron.

We develop and test new machine learning strategies for accelerating molecular crystal structure ranking and crystal property prediction using tools from geometric deep learning on molecular graphs. Leveraging developments in graph-based learning and the availability of large molecular crystal data sets, we train models for density prediction and stability ranking which are accurate, fast to evaluate, and applicable to molecules of widely varying size and composition. Our density prediction model, MolXtalNet-D, achieves state-of-the-art performance, with lower than 2% mean absolute error on a large and diverse test data set. Our crystal ranking tool, MolXtalNet-S, correctly discriminates experimental samples from synthetically generated fakes and is further validated through analysis of the submissions to the Cambridge Structural Database Blind Tests 5 and 6. Our new tools are computationally cheap and flexible enough to be deployed within an existing crystal structure prediction pipeline both to reduce the search space and score/filter crystal structure candidates.

A great proportion of molecular crystals can be made to grow as twisted fibrils. Typically, this requires high crystallization driving forces that lead to spherulitic textures. Here, it is shown how micron size channels fabricated from poly(dimethylsiloxane) (PDMS) serve to collimate the circular polycrystalline growth fronts of optically banded spherulites of twisted crystals of three compounds, coumarin, 2,5-bis(3-dodecyl-2-thienyl)-thiazolo[5,4-d]thiazole, and tetrathiafulvalene. The relationships between helicoidal pitch, growth front coherence, and channel width are measured. As channels spill into open spaces, collimated crystals "diffract" via small angle branching. On the other hand, crystals grown together from separate channels whose bands are out of phase ultimately become a single in-phase bundle of fibrils by a cooperative mechanism yet unknown. The isolation of a single twist sense in individual channels is described. We forecast that such chiral molecular crystalline channels may function as chiral optical wave guides.

Anion exchange membranes (AEMs) have attracted significant interest for their applications in fuel cells and other electrochemical devices in recent years. Understanding water distributions and hydroxide transport mechanisms within AEMs is critical to improving their performance as concerns hydroxide conductivity. Recently, nanoconfined environments have been used to mimic AEM environments. Following this approach, we construct nanoconfined cylindrical pore structures using graphane nanotubes (GNs) functionalized with trimethylammonium cations as models of local AEM morphology. These structures were then used to investigate hydroxide transport using ab initio molecular dynamics (AIMD). The simulations showed that hydroxide transport is suppressed in these confined environments relative to the bulk solution although the mechanism is dominated by structural diffusion. One factor causing the suppressed hydroxide transport is the reduced proton transfer (PT) rates due to changes in hydroxide and water solvation patterns under confinement compared to bulk solution as well as strong interactions between hydroxide ions and the tethered cation groups.

The synthesis of high-performance gas-sieving zeolitic film is challenging because it involves seeded secondary growth which is complex and difficult to reproduce. Additionally, expensive asymmetric inorganic porous supports are often needed for calcination of the zeolite films. Herein, scalable preparation of H2-sieving RUB-15 nanosheet films is reported bypassing the need for secondary growth and expensive supports. A novel, low-cost, thermally-robust, porous polybenzimidazole copolymer (PBI-AM Fumion®) support is prepared which allows deposition of thin, compact, and oriented RUB-15 nanosheets films without cracks or pinhole defects. The film hosts two transport pathways, H2-sieving six-membered silicate rings in the nanosheets and nonselective intersheet gaps maintained by the organic guest species in the gallery spacing. The latter is eliminated by a low-temperature (330 °C) calcination where the crystalline order in the nanosheets is preserved. The resulting zeolitic films yielded H2 permeances of 100–400 GPU and H2/CO2 selectivities above 20 at temperatures above 200 °C. The facile and scalable fabrication procedure with an attractive H2-sieving performance at elevated temperatures make these membranes promising for pre-combustion carbon capture.

Nuclear magnetic resonance relaxometry represents a powerful tool for extracting dynamic information. Yet, obtaining links to molecular motion is challenging for many ions that relax through the quadrupolar mechanism, which is mediated by electric field gradient fluctuations and lacks a detailed microscopic description. For sodium ions in aqueous electrolytes, we combine ab initio calculations to account for electron cloud effects with classical molecular dynamics to sample long-time fluctuations, and obtain relaxation rates in good agreement with experiments over broad concentration and temperature ranges. We demonstrate that quadrupolar nuclear relaxation is sensitive to subpicosecond dynamics not captured by previous models based on water reorientation or cluster rotation. While ions affect the overall water retardation, experimental trends are mainly explained by dynamics in the first two solvation shells of sodium, which contain mostly water. This work thus paves the way to the quantitative understanding of quadrupolar relaxation in electrolyte and bioelectrolyte systems.

The rational design of nanoscopic DNA tiles has yielded highly ordered crystalline matter in 2D and 3D. The most well-studied 3D tile is the DNA tensegrity triangle, which is known to self-assemble into macroscopic crystals. However, contemporary rational design parameters for 3D DNA crystals nearly universally invoke integer numbers of DNA helical turns and Watson-Crick (WC) base pairs. In this study, 24-bp edges are substituted into a previously 21-bp (two helical turns of DNA) tensegrity triangle motif to explore whether such unconventional motif can self-assemble into 3D crystals. The use of noncanonical base pairs in the sticky ends results in a cubic arrangement of tensegrity triangles with exceedingly high symmetry, assembling a lattice from winding helical axes and diamond-like tessellation patterns. Reverting this motif to sticky ends with Watson-Crick pairs results in a trigonal hexagonal arrangement, replicating this diamond arrangement in a hexagonal context. These results showcase that the authors can generate unexpected, highly complex, pathways for materials design by testing modifications to 3D tiles without prior knowledge of the ensuing symmetry. This study expands the rational design toolbox for DNA nanotechnology; and it further illustrates the existence of yet-unexplored arrangements of crystalline soft matter.

Predictions of the structures of stoichiometric, fractional, or nonstoichiometric hydrates of organic molecular crystals are immensely challenging due to the extensive search space of different water contents, host molecular placements throughout the crystal, and internal molecular conformations. However, the dry frameworks of these hydrates, especially for nonstoichiometric or isostructural dehydrates, can often be predicted from a standard anhydrous crystal structure prediction (CSP) protocol. Inspired by developments in the field of drug binding, we introduce an efficient data-driven and topologically aware approach for predicting organic molecular crystal hydrate structures through a mapping of water positions within the crystal structure. The method does not require a priori specification of water content and can, therefore, predict stoichiometric, fractional, and nonstoichiometric hydrate structures. This approach, which we term a mapping approach for crystal hydrates (MACH), establishes a set of rules for systematic determination of favorable positions for water insertion within predicted or experimental crystal structures based on considerations of the chemical features of local environments and void regions. The proposed approach is tested on hydrates of three pharmaceutically relevant compounds that exhibit diverse crystal packing motifs and void environments characteristic of hydrate structures. Overall, we show that our mapping approach introduces an advance in the efficient performance of hydrate CSP through generation of stable hydrate stoichiometries at low cost and should be considered an integral component for CSP workflows.

Abstract Tri‐cation (Cs+/CH3NH3+/CH(NH2)2+) and dual‐anion (Br–/I–) perovskites are promising light absorbers for inexpensive infrared (IR) photodetectors but degrade under prolonged IR exposure. Here, stable IR photodetectors based on electrospun tri‐cation perovskite fibers infiltrated with hole‐transporting π‐conjugated small molecule 2,2′,7,7′‐tetrakis[N,N‐di(4‐methoxyphenyl)amino]‐9,9‐spirobifluorene (Spiro‐OMeTAD) are demonstrated. These hybrid perovskite photodetectors operate at a low bias of 5 V and exhibit ultra‐high gains with external quantum efficiencies (EQEs) as high as 3009%, decreasing slightly to ≈2770% after 3 months in air. These EQE values are almost ten times larger than those measured for photodetectors comprising bilayer perovskite/Spiro‐OMeTAD films. A high density of charge traps on electrospun fiber surfaces gives rise to a photomultiplication effect in which photogenerated holes can travel through the active layer multiple times before recombining with trapped electrons. Time‐resolved photoluminescence and conductive atomic force microscopy mapping reveal the improved performance of electrospun fibers to originate from the significantly enhanced interfacial surface area between the perovskite and Spiro‐OMeTAD compared to bilayers. As a solution‐based, scalable and continuous method of depositing perovskite layers, electrospinning thus presents a promising strategy for the inexpensive fabrication of high‐performance IR photodetectors for applications ranging from information technology to imaging.

Many molecular crystals (approximately one third) grow as twisted, helicoidal ribbons from the melt, and this preponderance is even higher in restricted classes of materials, for instance, charge-transfer complexes. Previously, twisted crystallites of such complexes present an increase in carrier mobilities. Here, the effect of twisting on charge mobility is better analyzed for a monocomponent organic semiconductor, 2,5-bis(3-dodecyl-2-thienyl)-thiazolo[5,4-d]thiazole (BDT), that forms twisted crystals with varied helicoidal pitches and makes possible a correlation of twist strength with carrier mobility. Films are analyzed by X-ray scattering and Mueller matrix polarimetry to characterize the microscale organization of the polycrystalline ensembles. Carrier mobilities of organic field-effect transistors are five times higher when the crystals are grown with the smallest pitches (most twisted), compared to those with the largest pitches, along the fiber elongation direction. A tenfold increase is observed along the perpendicular direction. Simulation of electrical potential based on scanning electron microscopy images and density functional theory suggests that the twisting-enhanced mobility is mainly controlled by the fiber organization in the film. A greater number of tightly packed twisted fibers separated by numerous smaller gaps permit better charge transport over the film surface compared to fewer big crystallites separated by larger gaps.

Skyrmion racetrack memories are highly attractive for next-generation data storage technologies. Skyrmions are noncollinear spin textures stabilized by chiral interactions. To achieve a fast-operating memory device, it is critical to move skyrmions at high speeds. The skyrmion dynamics induced by spin–orbit torques (SOTs) in the commonly studied ferromagnetic films is hindered by strong pinning effects and a large skyrmion Hall effect causing deflection of the skyrmion toward the racetrack edge, which can lead to information loss. Here, we investigate the current-induced nucleation and motion of skyrmions in ferrimagnetic Pt/CoGd/(W or Ta) thin films. We first reveal field-free skyrmion nucleation mediated by Joule heating. We then achieve fast skyrmion motion driven by SOTs with velocities as high as 610 m s –1 and a small skyrmion Hall angle |θ SkHE | ≲ 3°. Our results show that ferrimagnets are better candidates for fast skyrmion-based memory devices with low risk of information loss.

Nuclear magnetic resonance relaxometry represents a powerful tool for extracting dynamic information. Yet, obtaining links to molecular motion is challenging for many ions that relax through the quadrupolar mechanism, which is mediated by electric field gradient fluctuations and lacks a detailed microscopic description. For sodium ions in aqueous electrolytes, we combine ab initio calculations to account for electron cloud effects with classical molecular dynamics to sample long-time fluctuations, and obtain relaxation rates in good agreement with experiments over broad concentration and temperature ranges. We demonstrate that quadrupolar nuclear relaxation is sensitive to subpicosecond dynamics not captured by previous models based on water reorientation or cluster rotation. While ions affect the overall water retardation, experimental trends are mainly explained by dynamics in the first two solvation shells of sodium, which contain mostly water. This work thus paves the way to the quantitative understanding of quadrupolar relaxation in electrolyte and bioelectrolyte systems.

Recent progress in MRI methods development led to a novel concept for operando screening of commercial battery cells. Sensing electrochemical processes inside an operating cell can be done via the detection of associated magnetic fields. This concept is based on the classic phenomenon described by Ampère's circuital and Biot–Savart laws. A new method referred to as Surface-Scan MRI employs ultra-fast quantitative mapping of the magnetic field in a thin layer of polymer placed in direct contact with the cell. Preliminary experimental work demonstrated the ability of Surface-Scan MRI to detect cells that undergone overcharging, a hazardous event that can degrade cells' components and ultimately creates a risk of fire. In the future, the analysis of Surface-Scan MRI data can rely largely on numerical simulations of electromagnetic phenomena based on accurate models of real cells. A series of numerical tests performed in this work confirms the capacity of Surface-Scan MRI to detect a variety of defects associated with electrochemical degradation of cathode, anode and electrolyte materials. Effects of morphology, location and conductivity of the defects on magnetic field distributions were examined for realistic cell models including flat jelly roll configurations. MRI resolution limits associated with the defect domain size and with the distance between the defect and the detection medium were estimated. Location and morphology of highly conductive defects (σ > 105 S m−1), e.g. regions rich in quasi-metallic dendrites, can be directly identified from Surface-Scan MRI images. Low conductivity defects, e.g. degraded electrolyte or cathode and anode coatings, manifest via patterns much larger than the defects.

Heterostructures obtained from layered assembly of 2D materials such as graphene and hexagonal boron nitride have potential in the development of new electronic devices. Whereas various materials techniques can now produce macroscopic scale graphene, the construction of similar size heterostructures with atomically clean interfaces is still unrealized. A primary barrier has been the inability to remove polymeric residues from the interfaces that arise between layers when fabricating heterostructures. Here, the interface cleaning problem of polymer-contaminated heterostructures is experimentally studied from an energy viewpoint. With this approach, it is established that the interface cleaning mechanism involves a combination of thermally activated polymer residue mobilization and their mechanical actuation. This framework allows a systematic approach for fabricating record large-area clean heterostructures from polymer-contaminated graphene. These heterostructures provide state-of-the-art electronic performance. This study opens new strategies for the scalable production of layered materials heterostructures.

Fuel-cell-based proton exchange membranes (PEMs) show great potential as cost-effective and clean energy conversion devices. In our recent work, we found that for the low-hydrated model PEMs with a inhomogeneous water distribution and a sulfonate anionic functional end group (SO 3 –), the H 3 O + reacts with SO 3 – according to SO 3 – + H 3 O + ↔ SO 3 H + H 2 O, indicating that the anions in PEMs become active participants in the hydronium diffusion. In this work, we use fully atomistic ab initio molecular dynamics simulations to elucidate the optimal conditions that would promote the participation of SO 3 – in the hydronium diffusion mechanism by increasing the H 3 O + /SO 3 – reactivity, thus increasing the hydronium diffusivity along the cell. The results presented in this work allow us to suggest a set of design rules for creating novel, highly conductive PEMs operating at high temperatures under a nonuniform water distribution using a linker/anion with a relatively high p K a such as (CH 2) 2 SO 3. We expect that the discovery of these key design principles will play an important role in the synthesis of high-performing materials for emerging PEM-based fuel cell technologies.

Recent studies suggest that operating anion exchange membrane (AEM) fuel cells at high temperatures has enormous technological potential. However, obtaining a fundamental understanding of the effect of temperature on hydroxide conductivity and membrane stability remains a key hurdle to realizing the full potential of high-temperature AEM fuel cells. In this work, we present a combined theoretical and experimental study to explore the effect of temperature on hydroxide ion and water diffusivities in AEMs. Both fully atomistic ab initio molecular dynamics simulations and 1 H pulsed field gradient NMR measurements confirm that the OH – diffusion changes non-monotonically with increasing temperature. Specifically, the D OH – versus T curve exhibits a region in which d D OH – /d T < 0, indicating the presence of a kink in the curve, which we refer to as a “diffusion kink”. The simulations show that the underlying causes of this behavior vary with the hydration level. Furthermore, we were able to rationalize the conditions underlying this counterintuitive behavior and to suggest ways to identify the optimal operating temperature for each model AEM system. We expect that the discovery of this unusual temperature dependence of the diffusivity will play an important role in the design of new, stable, and highly conductive AEM-based devices such as electrolyzers, redox flow batteries, and fuel cells.

Many crystals grow as banded spherulites from the melt with an optical rhythm indicative of helicoidal twisting. In this work, 23 of 41 charge transfer complexes (CTCs) are grown with twisted morphologies. As a group, CTCs more commonly twist (56%) than molecular crystals arbitrarily chosen in our previous research (31%). To analyze the effect of twisting on charge transport, three tetracyanoethylene-based CTCs with phenanthrene (PhT), pyrene (PyT), and perylene are characterized. PhT and PyT are subject to mobility measurements using organic field-effect transistors. The mobilities for twisted crystals are around three times higher than for crystals with no ostensible optical modulation, which are effectively straight. The differences in mobilities of straight and twisted crystals are considered computationally based on density functional theory. Straight crystal models built from crystallographic information files are calculated and present anisotropic hole and electron transport. For twisted crystal models, adjacent layers in the supercell are rotated by 0.01° around experimentally determined twisting directions. The modified transfer integrals lead to a slight increase (up to 25%) in the calculated mobilities of twisted crystals. Comparisons of model calculations on individual fibrils and measurements of ensembles of fibrils indicate that interfaces between single crystals are likely consequential.

Predictions of crystal structures from first-principles electronic structure calculations and molecular simulations have been performed for an energetic molecule, 4-amino-2,3,6-trinitrophenol. This physics-based approach consists of a series of steps. First, a tailor-made two-body potential energy surface (PES) was constructed with recently developed software, autoPES, using symmetry-adapted perturbation theory based on a density-functional theory description of monomers [SAPT(DFT)]. The fitting procedure ensures asymptotic correctness of the PES by employing a rigorous asymptotic multipole expansion, which seamlessly integrates with SAPT(DFT) interaction energies. Next, crystal structure prediction (CSP) was performed by generating possible crystal structures with rigid molecules, minimizing these structures using the SAPT(DFT) force field, and running isothermal–isobaric molecular dynamics (MD) simulations with flexible molecules based on the tailor-made SAPT(DFT) intermolecular force field and a generic/SAPT(DFT) intramolecular one. This workflow led to the experimentally observed structure being identified as one of the forms with the lowest lattice energy, demonstrating the success of a first-principles, bottom-up approach to CSP. Importantly, we argue that the accuracy of the intermolecular potential, here the SAPT(DFT)-based potential, is determinative of the crystal structure, while generic/SAPT(DFT) force fields can be used to represent the intramolecular potential. This force field approach simplifies the CSP workflow, without significantly compromising the accuracy of the prediction.

Crystal twisting introduces optical activity to organic semiconducting films of centrosymmetric tetrathiafulvalene.

Exposing anion exchange membrane (AEM) fuel cells to ambient air is known to decrease fuel cell efficiency significantly due to the presence of CO 2.

The body-centered cubic (bcc) polymorph of NaCB 11 H 12 has been stabilized at room temperature by high-energy mechanical milling. Temperature-dependent electrochemical impedance spectroscopy shows an optimum at 45-min milling time, leading to an rt conductivity of 4 mS cm –1. Mechanical milling suppresses an order–disorder phase transition in the investigated temperature range. Nevertheless, two main regimes can be identified, with two clearly distinct activation energies. Powder X-ray diffraction and 23 Na solid-state NMR reveal two different Na + environments, which are partially occupied, in the bcc polymorph. The increased number of available sodium sites w.r.t. ccp polymorph raises the configurational entropy of the bcc phase, contributing to a higher ionic conductivity. Mechanical treatment does not alter the oxidative stability of NaCB 11 H 12. Electrochemical test on a symmetric cell (Na|NaCB 11 H 12 |Na) without control of the stack pressure provides a critical current density of 0.12 mA cm –2, able to fully charge/discharge a 120 mA h g –1 specific capacity positive electrode at the rate of C /2.

The number of synthetic strategies used to functionalize MOFs with polymers is rapidly growing; this stems from the knowledge that non-native polymeric guests can significantly boost MOF performance in a number of desirable applications. The current work presents a scalable and solid-state method for MOF/polymer composite production. This simple method constitutes mixing a MOF powder, namely, Fe-BTC (BTC = 1,3,5-benzenetricarboxylate), with a biomass-derived solid monomer, 5-hydroxymethylfurfural (HMF), and subsequently heating the solids; the latter promotes both solid-state diffusion of HMF into the MOF and the formation of polymeric humin species with a high density of accessible hydroxyl functionality within the MOF pore. The resulting composite, Fe-BTC/humin, was found to selectively extract Ag + ions from laundry wastewater. Subsequent reduction of the Ag + species yields a novel catalyst, Fe-BTC/humin/Ag, that is able to drive the organic transformation of cinnamaldehyde in a highly selective manner. Moreover, the catalyst exhibited recyclability up to five cycles, which is in contrast to the Fe-BTC/Ag catalyst without the humin-based polymer. It is envisioned that MOF/polymer composites that are able to selectively extract precious metals from liquid waste streams can be used for the future production of sustainable catalysts; this work was aimed at demonstrating a proof of concept in this regard. Moreover, this study brings more understanding of the impact that MOFs can have on polymer functionalities. Understanding the polymer structure and how it can be manipulated will help us realize the high degree of future potential of this distinct class of composite materials.

A quasi-one-dimensional organic semiconductor, hepta(p-phenylene vinylene) (HPV), was incorporated into a DNA tensegrity triangle motif using a covalent strategy. 3D arrays were self-assembled from an HPV-DNA pseudo-rhombohedron edge by rational design and characterized by X-ray diffraction. Templated by the DNA motif, HPV molecules exist as single-molecule fluorescence emitters at the concentration of 8 mM within the crystal lattice. The anisotropic fluorescence emission from HPV-DNA crystals indicates HPV molecules are well aligned in the macroscopic 3D DNA lattices. Sophisticated nanodevices and functional materials constructed from DNA can be developed from this strategy by addressing functional components with molecular accuracy.

Imidacloprid, the world’s leading insecticide, has been approved recently for controlling infectious disease vectors; yet, in agricultural settings, it has been implicated in the frightening decline of pollinators. This argues for strategies that sharply reduce the environmental impact of imidacloprid. When used as a contact insecticide, the effectiveness of imidacloprid relies on physical contact between its crystal surfaces and insect tarsi. Herein, seven new imidacloprid crystal polymorphs are reported, adding to two known forms. Anticipating that insect uptake of imidacloprid molecules would depend on the respective free energies of crystal polymorph surfaces, measurements of insect knockdown times for the metastable crystal forms were as much as nine times faster acting than the commercial form against Aedes, Anopheles, and Culex mosquitoes as well as Drosophila (fruit flies). These results suggest that replacement of commercially available imidacloprid crystals (a.k.a. Form I) in space-spraying with any one of three new polymorphs, Forms IV, VI, IX, would suppress vector-borne disease transmission while reducing environmental exposure and harm to nontarget organisms.