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As a promising candidate to replace lithium-ion batteries, rechargeable aqueous zinc ion batteries (AZIB) are receiving increasing attention due their high energy density, high safety, low cost and environmental friendliness. In this study, metal ions may be introduced into the interlayer gap of layered vanadium oxide nanobelts through a one-step hydrothermal process, without changing their original structure. Moreover, we have demonstrated by density functional theory computations that Mn metal ions not only serve as structural pillars but also enhance the conductivity of MnxVO2·0.2H2O, facilitating the migration of Zn ions. As a result, the electrochemical performance of MnxVO2·0.2H2O as an AZIB cathode has significantly improved; after 100 cycles at 0.5 A g−1, it exhibits a high reversible capacity of 350 mA h g−1. With a high current density of 5 A g−1, the initial capacity can still reach 295 mA h g−1. This paper suggests an effective method to maximize the efficiency of AZIB electrode materials. [ABSTRACT FROM AUTHOR]

In this paper, the geometric structures and electron-optical properties of AlAs/GaS heterojunctions and Se-doped AlAs/GaS heterojunctions are calculated based on first-principles of density functional theory (DFT). At the same time, the influence of the AlAs layer's 5° rotation stacking method on the AlAs/GaS heterojunction is discussed. The results show that the AlAs/GaS heterojunction is a type-II van der Waals heterojunction (vdWH) with a direct bandgap of 0.974 eV, and the Z-scheme electron transfer mechanism is more conducive to the separation of photogenerated electrons and holes. Both semiconductor-to-metal transitions can be achieved by applying an external electric field and strain. Under the action of an external electric field and uniaxial strain, AlAs/GaS maintains the type-II energy band alignment throughout the process. When biaxial strain is applied, the heterojunction is accompanied by a direct–indirect bandgap transition. It is worth mentioning that the optical absorption of the AlAs/GaS heterojunction is significantly higher than that of the two monolayers, and the absorption range is wider. The above characteristics indicate that the AlAs/GaS heterojunction has wider applications in fields such as photodetectors. [ABSTRACT FROM AUTHOR]

Efficient hydrogen evolution reaction (HER) electrocatalysts are crucial for renewable energy storage and conversion. Pt remains the most efficient HER catalyst, but its widespread application is hindered by cost and resource constraints. In this study, we investigate the HER electrocatalytic activities of free-metal SiC monolayers through doping and strain engineering. Through density functional theory (DFT) calculations, we explore the effects of B, N, S, and P doping on the HER performance of SiC. Our results reveal that B and P doping enhance the catalytic activity, with P doping showing the most promising activity due to its smaller ΔGH* values. Furthermore, we apply tensile strain to modulate the HER activity of P-doped SiC, achieving further improvements. We also construct composite structures of P-doped SiC with graphene, enhancing conductivity and catalytic performance. Our findings provide valuable insights into tailoring the HER catalytic properties of SiC monolayers, offering a pathway towards sustainable hydrogen production. [ABSTRACT FROM AUTHOR]

We describe a new quadrupolar NMR crystallography guided crystal structure prediction (QNMRX-CSP) protocol for the prediction and refinement of crystal structures, including its design, benchmarking, and application to seven organic HCl salts. Five HCl salts with a limited number of low-energy conformations were chosen as model systems for benchmarking: betaine HCl, glycine HCl, D -alanine HCl, guanidine HCl, and aminoguanidine HCl; two were chosen for blind tests: N,N′-dimethylglycine HCl and metformin HCl. The QNMRX-CSP protocol uses experimental 35Cl solid-state NMR (SSNMR) spectra and X-ray diffraction (XRD) data in tandem with Monte Carlo simulated annealing and dispersion-corrected plane-wave density functional theory (DFT-D2*) calculations. The protocol comprises three modules: (i) the assignment of motion groups, (ii) a Monte Carlo simulated annealing algorithm for generating tens of thousands of candidate structures, and (iii) DFT-D2* geometry optimizations of structural models and concomitant computation of 35Cl EFG tensors. Key benchmarked metrics are used for retaining the best candidate structures, including unit cell parameters, static lattice energies, and EFG distances (ΓEFG). The protocol is shown to generate structural models that are excellent matches with experimental crystal structures that have been DFT-D2* geometry optimized, as validated by crystallographic R-factors (R) and root-mean squared distances (RMSDs) of atomic positions that are well below 10% and 0.2 Å, respectively. Finally, consideration is given to the use of the QNMRX-CSP protocol as a standalone technique or in concert with other NMRX methods and Rietveld refinements, and possible applications employing other quadrupolar nuclei (i.e., 14N and 17O). [ABSTRACT FROM AUTHOR]

Zeolites have been proposed as carrier materials for the encapsulation and controlled release of the anticancer drug 5-fluorouracil (5-FU). Besides, they could also find use in the adsorption-based removal of 5-FU from water, for example in the treatment of hospital effluents. In the present work, dispersion-corrected density functional theory (DFT) calculations and DFT-based ab initio molecular dynamics (AIMD) simulations are employed to study the interaction of 5-FU with faujasite-type zeolites having different Si/Al ratios. Comparing distinct local arrangements of Al atoms and charge-balancing protons, it is evaluated to what extent "multi-site" interactions, i.e., interactions of 5-FU with more than one proton, affect the adsorption energy. While the most pronounced increase in interaction strength occurs when moving from an all-silica zeolite to a protonic zeolite having a single proton in one twelve-membered ring, a significant additional stabilisation arises if a second framework proton is present in the same ring. Typically, several hydrogen bonds are formed between 5-FU and protonic zeolite frameworks, with 5-FU simultaneously acting as donor and acceptor. AIMD simulations confirm the stability of these hydrogen bonds at room temperature in the absence of water. Additionally, infrared spectra are predicted for selected low-energy configurations in order to facilitate an experimental identification of different bonding environments. AIMD simulations probing the competitive adsorption of 5-FU and water show that the high affinity of water to the framework protons causes a breaking of hydrogen bonds, framework deprotonation, and a displacement of 5-FU from its initial position. Exposure of dehydrated 5-FU@FAU composites to water might thus be a useful approach to trigger 5-FU release in drug delivery applications. [ABSTRACT FROM AUTHOR]

A series of 21 sulfoester and sulfonamide derivatives comprising two aromatic rings was synthesized to investigate the effect of the presence of either electron-donating (ED) or electron-withdrawing (EW) groups on the intramolecular π-stacking assembly. The positioning of ED or EW moieties was carried out directly on one of the aromatic rings linked to the sulfonyl or sulfonamide moieties. In contrast, the other aromatic ring (phenyl or pyridine) was connected by a –CH2–CH2– spacer with the sulfonyl or sulfonamide moiety. The purpose of having an ethyl spacer between the two aromatic rings was to achieve conformational flexibility, facilitating the intramolecular π-stacking assembly between the two aromatic rings. The use of sulfoester/sulfonamide groups allowed more conformational flexibility to attain desired orientations in solids with the interplay of the hydrogen-bonding interactions. Between the two functional groups, sulfonamides offered a more hydrogen-rich environment due to the amine moiety and may exhibit higher H-bonding propensity than the sulfoester moiety. The central idea here was to study the interplay between the hydrogen-bonding and π⋯π interactions. The substituent groups chosen were categorized as strong electron-withdrawing (–CF3 and –CN), weak electron-withdrawing (–Cl and –Br), neutral (–H), and good electron-donating (–CH3 and –OCH3) groups. Crystal structure analysis revealed the syn conformation for all the derivatives, enabling intramolecular π⋯π interactions between the two aromatic rings, whereas in the sulfonamide derivatives, the molecule takes either midway or anti conformations, except for one pyridine sulfonamide derivative, which showed the syn orientation but lacked intramolecular π-stacking interactions. The absence of any conventional H-bond forming functional groups in the sulfoester derivatives may have resulted in the syn geometry facilitated by intramolecular π-stacking interactions. Conversely, H-bond-forming functional groups in the sulfonamide derivatives could have prevented the syn conformation. The conformational analysis carried out employing density functional theory (DFT) calculations confirmed the higher stability of the syn conformation over the midway and anti orientations. [ABSTRACT FROM AUTHOR]

Mechanical properties and structure–property relationship of the Ti–45Nb (mass%) alloy with potential applications in biomedicine were investigated using a multidisciplinary approach. Because the biomechanical compatibility of metallic implant materials can be significantly improved by microstructural refinement and laser surface modification (LSM), the present study concentrates on the investigation of the mechanical properties of the Ti–45Nb alloy subjected to extreme processing conditions to evaluate their impact on the alloy improved applicability in the bio-environment. The alloy was therefore subjected to high-pressure torsion (HPT) and LSM processing to obtain favorable alloy characteristics. Crystal structure prediction was conducted using data mining (DM) and evolutionary algorithms (EA). All the obtained potential structure candidates were submitted to the local optimizations at the level of density functional theory (DFT); subsequently, the phonon lattice dynamics and mechanical properties were systematically investigated. The alloy structure progression and mechanical characteristics were examined under the influence of extremely high temperatures induced during the LSM processing and the extreme pressure achieved during the HPT treatment. XRD characterization was performed using experimental and theoretical methods showing the presence of bcc β-Ti and orthorhombic Cmcm Ti4Nb phase. Mechanical properties such as Young's modulus, Vicker's hardness, and plasticity of the most relevant Ti4Nb modifications predicted after DM-EA-DFT were found to corroborate well with the experimental results of nanoindentation measurements. The present study reveals that the additional processing of the Ti–45Nb alloy under extreme conditions leads to significant improvement in the alloy's bio-mechanical compatibility. [ABSTRACT FROM AUTHOR]

Morphology control is widely acknowledged as an effective method for optimizing the exposed facets and active sites of palladium (Pd) nanocrystals, which enhances their electrocatalytic activity. However, conventional approaches inevitably alter the reaction from both thermodynamic and kinetic perspectives, rendering control intricate. In this investigation, we introduce a specialized strategy to achieve morphology control over PdAuAg nanocrystals, demonstrating their exceptional performance as electrocatalysts for the ethanol oxidation reaction (EOR). Specifically, three metallic precursor solutions were individually introduced into a one-pot reaction system at controlled rates using syringe pumps, allowing for separate manipulation of each metal atom's concentration without cross-reaction. Consequently, a variety of products with unique morphologies and structures were produced, all adhering to the same protocol except for the rate of metal atom introduction. When catalyzing the EOR, the optimized PdAuAg nanocrystals supported on carbon black exhibited a sevenfold increase in mass activity compared to Pt/C, as well as enhanced reaction kinetics and long-term stability. Density functional theory (DFT) calculations confirmed that crystal facets can influence the ethanol oxidation reaction pathway, rationalizing the improved catalytic performance. Our study presents a viable approach for modulating the morphology of trimetallic nanocrystals by varying the feed rate of metal atoms in a one-pot reduction, illuminating the rational design of high-performance fuel cell catalysts. [ABSTRACT FROM AUTHOR]

Four lead(II) complexes featuring pyrazoylisonicotinoylhydrazone ligand paired with various anionic co-ligands (azido, thiocyanato, nitrito, and nitrato) were synthesized and thoroughly examined using structural, analytical, and spectroscopic techniques. These ligands, in their mono-deprotonated state, bind to the lead(II) ion in a tridentate manner through two nitrogen atoms and one oxygen atom. Single-crystal X-ray crystallography revealed the capacity of these molecular complexes to form larger aggregates influenced by the nature of the anion attached to the metal center. In every complex, the lead atom adopts a hemidirectional coordination environment, making it geometrically suited for tetrel bond formation. The crystal structures demonstrate that lead atoms engage in notably short interactions with nitrogen atoms, distances that are shorter than the sum of their van der Waals radii yet exceed the sum of their covalent radii. These tetrel bonds play a pivotal role in weaving the monomeric into self-assembled dimers or extended supramolecular 1D polymers. The formation and characteristics of these intriguing supramolecular structures observed in the solid state of each complex were further explored and validated through density functional theory (DFT) calculations and several computational tools like MEP, NCIPlot, QTAIM, and ELF methods. [ABSTRACT FROM AUTHOR]

Because of their unique physicochemical integration mode, energetic host–guest solvates provide a balanced method to expand CL-20 high explosives. CL-20/hydrogen peroxide (H2O2) energetic solvates maintain their detonation performance by combining H2O2 molecules into a lattice akin to hydrate CL-20/H2O solvate (α-CL-20). Herein, using periodic density functional theory (DFT) calculation and molecular dynamics simulation, the structural evolution and intermolecular interaction mechanism of orthorhombic CL-20/H2O2 (o-CL-20/H2O2), monoclinic CL-20/H2O2 (m-CL-20/H2O2) and CL-20/H2O solvates were monitored by the vibrational spectrum and vibrational density of states (VDOS) in the THz region when the temperature was increased from 298 K to 558 K. There was greater similarity in the vibrational characteristics of THz spectra for o-CL-20/H2O2 and CL-20/H2O solvates that was supported by the thermal expansion anisotropy of lattice parameters and that of difference for the m-CL-20/H2O2 solvate. With increased temperature, spectral signals in the power spectrum of VDOS reflected the conformational evolution of CL-20 molecules in o-CL-20/H2O2 solvate and structural insensitivity of m-CL-20/H2O2 solvate. THz peaks of CL-20/H2O revealed the weakening of intermolecular interactions of CL-20 and H2O molecules, which were in agreement with the fact that H2O molecules more easily escape from host–guest solvates, whereas the H2O2 molecule was restricted in a cage of CL-20 molecules for the m-CL-20/H2O2 solvate. RDF and hydrogen bond (H-bond) interaction analyses were performed to further clarify stronger intermolecular H-bond interactions in the o-CL-20/H2O2 solvate as compared to that of the other two combined with H2O2 or H2O solvates. This finding introduces new insights into clarifying the formation mechanism of hydroxide with CL-20-based energetic host–guest solvates. [ABSTRACT FROM AUTHOR]

A series of charge transfer cocrystals with fluorescence properties involving 1,2,4,5-tetracyanobenzene (TCNB, C10H2N4) as acceptor, fluorene (FR, C13H10) and its bromide 2-bromofluorene (2-BrFR, C13H9Br), carbazole (CZ, C12H9N) and its bromide 2-bromocarbazole (2-BrCZ, C12H8BrN) as donor were synthesized via cocrystal design strategies. The formation mechanism of the crystal structure was explored by density functional theory at the molecular level. The stacking structure of the cocrystal was formed by the combination of charge transfer interactions, π–π interactions and hydrogen bonding. The N atom of donors in TCNB–CZ and TCNB–2-BrCZ could enhance the charge transfer, appearing as a red shift of the fluorescence emission wavelength. Conversely, the Br atom in TCNB–2-BrFR and TCNB–2-BrCZ weakens the charge transfer, giving a blue shift in the fluorescence emission spectrum. The four new cocrystals exhibit tunable luminescence from green (529 nm) to yellow (552 nm) and to red (604 nm and 614 nm). It was found that the introduction of N and Br atoms in the assembly units can not only regulate the luminescence range of the cocrystals, but also adjust the luminescence efficiency, which provides a strategy for the development of promising organic luminescent materials. [ABSTRACT FROM AUTHOR]

In this paper, we synthesized layered crystals of bis(μ2-chlor)-tris(triphenylphosphine)-di-copper(I) (CTC) and bis(μ2-bromo)-tris(triphenylphosphine)-di-copper(I) (BTC) via electrochemical synthesis in an ambient environment. The crystal stands edge-on to the copper substrate in the electrochemical synthesis, which would enhance the charge transfer between the crystal and the substrate, promoting its photoelectric properties. Combined with density functional theory calculations, the optical absorption and emission are the crystals were studied to obtain a clarified mechanism. Using a chemical etching strategy, we can obtain BTC microtubes with tunable cavities, which can be used as microscopic containers. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis and photoluminescence properties of a new 1,3-dioxo-2-(1H-tetrazol-5-yl)-2,3-dihydro-1H-benzo[de]isoquinoline-6,7-dicarboxylic (H3L) ligand and three coordination polymers (CPs). Compound [Zn(ntca)DMF]n·DMF (1) (ntca2− = 1,4,5,8-naphthalenetetracarboxylate 1,8-monoanhydride, DMF = N,N-dimethylformamide) formed 1D coordination polymer chains packed by hydrogen bonding interactions. On its part, compounds namely [(CH3)2NH2](Zn2(μ-OH)(L)(5-NH2-tetrazolate)n·2H2O (2) and [(CH3)2NH2](ZnL)n (3) (where H3L stands for 1,3-dioxo-2-(1H-tetrazol-5-yl)-2,3-dihydro-1H-benzo[de]isoquinoline-6,7-dicarboxylic acid) crystallize as 2D-layered and 3D anionic frameworks containing dimethylammonium cations occupying the voids. Photoluminescence (PL) measurements have been performed in the solid state on all CPs and ligands to characterize their emission properties, including variable-temperature spectra, lifetime and efficiency. Moreover, the photophysical properties have been studied from the theoretical viewpoint by means of time dependent density functional theory (TD-DFT) in order to elucidate the mechanisms and electronic transitions governing the process. Compounds 1 and 3 present an intense blue luminescence which was originated in the electronic transitions of the ntca2− and the L3− ligands. Compound 2 displays a lower quantum yield which could be tentatively attributed to the weak π–π interactions of the aromatic clouds of L3− or the molecular vibrations and/or possible rotational motions of the 5-amino-tetrazolate co-ligand. [ABSTRACT FROM AUTHOR]

This study describes the discovery of a unique ionic cocrystal of the active pharmaceutical ingredient (API) ponatinib hydrochloride (pon·HCl), and characterization using single-crystal X-ray diffraction (SCXRD) and solid-state NMR (SSNMR) spectroscopy. Pon·HCl is a multicomponent crystal that features an unusual stoichiometry, with an asymmetric unit containing both monocations and dications of the ponatinib molecule, three water molecules, and three chloride ions. Structural features include (i) a charged imidazopyridazine moiety that forms a hydrogen bond between the ponatinib monocations and dications and (ii) a chloride ion that does not feature hydrogen bonds involving any organic moiety, instead being situated in a "square" arrangement with three water molecules. Multinuclear SSNMR, featuring high and ultra-high fields up to 35.2 T, provides the groundwork for structural interpretation of complex multicomponent crystals in the absence of diffraction data. A 13C CP/MAS spectrum confirms the presence of two crystallographically distinct ponatinib molecules, whereas 1D 1H and 2D 1H–1H DQ–SQ spectra identify and assign the unusually deshielded imidazopyridazine proton. 1D 35Cl spectra obtained at multiple fields confirm the presence of three distinct chloride ions, with density functional theory calculations providing key relationships between the SSNMR spectra and H⋯Cl− hydrogen bonding arrangements. A 2D 35Cl → 1H D-RINEPT spectrum confirms the spatial proximities between the chloride ions, water molecules, and amine moieties. This all suggests future application of multinuclear SSNMR at high and ultra-high fields to the study of complex API solid forms for which SCXRD data are unavailable, with potential application to heterogeneous mixtures or amorphous solid dispersions. [ABSTRACT FROM AUTHOR]

The crystal structures and crystallisation behaviours of MII–TbIII–MII heterotrinuclear complexes, [(L)MTbM(L)]NO3 (M = Mn and Zn; L3− stands for a conjugated base of H3L = 1,1,1-tris[(3-methoxysalicylideneamino)methyl]ethane), obtained from various organic solvents (MeOH, EtOH, CH2Cl2 and CHCl3) were investigated. The trinuclear complex cation has two asymmetric centres (Δ or Λ) at two MII sites as a result of the twisted tripodal arms of L3−. Single-crystal X-ray diffraction analysis revealed that all the analysed Zn–Tb–Zn complexes had homochiral structures (Δ,Δ- or Λ,Λ-enantiomers) in each single crystal; however, the type of crystallisation behaviour showed clear differences depending on the type of solvent molecule. Specifically, crystallisation from MeOH or CH2Cl2 resulted in the exclusive formation of the Λ-conglomerates with the Λ,Λ-enantiomers—a phenomenon we recently termed 'absolute spontaneous resolution'. The analogous Mn–Tb–Mn complex crystallised from MeOH also resulted in the same phenomenon as that of Zn–Tb–Zn. In contrast, the meso-type (Δ,Λ) achiral isomer of the Mn–Tb–Mn complex was deposited for the first time in a series of MII–LnIII–MII trinuclear complexes from a CH2Cl2 or EtOH solution. Density functional theory calculations were performed to compare the thermodynamic stability of homochiral (Λ,Λ) and meso-type (Δ,Λ) complex cations of [(L)MnTbMn(L)]+ in MeOH and EtOH. Results were consistent with the molecular structures observed in the crystallographic analysis of the compounds deposited from these solvents. [ABSTRACT FROM AUTHOR]

High-pressure single-crystal X-ray diffraction, intermolecular interaction energy calculations, and density functional theory are used to examine the structure and emission properties of the classical organic rotor hexaphenylbenzene (C6Ph6) during hydrostatic compression to 4.14 GPa. Under applied pressure, the inter-phenyl distance in intermolecular dimers with displaced-stacked conformations gradually shortens, indicating the likelihood for hexaphenylbenzene to undergo mechanofluorochromism, while the stability of the crystal is governed by T-shaped intermolecular phenyl dimers. The theoretical band gaps and UV absorption spectra of hexaphenylbenzene at ambient pressure and 1.05 GPa predict an absorption red-shift by about 50 nm, in agreement with shortening of the intermolecular displaced-stacked interactions in the crystal under pressure. Compression of the intermolecular interactions in hexaphenylbenzene prompts a non-centrosymmetric to centrosymmetric phase transition from orthorhombic Pna21 to monoclinic P21/c at 1.05 GPa, as the approximately hexagonally-packed layers of hexaphenylbenzene molecules adopt a perfect hexagonal arrangement. This pressure-stimulated phase transition involving gain of centrosymmetry is an interesting structural phenomenon that is previously unreported in organic crystals. [ABSTRACT FROM AUTHOR]

Laser induced damage sites on the surface of a KDP crystal component tend to grow with subsequent laser irradiation, which substantially decrease the lifetime of these optics. The structural investigation suggests that this may be related to the surface damage products of the crystals. In this work, the differences in the crystal structures, electronic properties and optical absorption between the KDP crystal and its surface laser-induced decomposition products K2H2P2O7 and KPO3 are investigated by using first-principles calculations. The theoretical results show that the nonlinear optical active units of KDP crystals are disrupted after irradiation dehydration to K2H2P2O7 and KPO3, which leads to the optical properties at the surface damage being deteriorated. In terms of the electronic structure, the dehydration products K2H2P2O7 and KPO3 have a shorter band gap compared with the KDP crystal. In addition, K2H2P2O7 and KPO3 have a wider optical absorption band than that of the KDP crystal and introduce more ultraviolet absorption in the optical elements. Compared to polycrystalline KDP at the bulk damage sites, the dehydration products at the surface damage increase the ultraviolet absorption of the crystals and cause the surface damage to continually grow under subsequent irradiation, whereas the bulk damage does not continue to increase in subsequent laser irradiation. [ABSTRACT FROM AUTHOR]

Patterns of N–H⋯O and N–H⋯N hydrogen bonds are described in a set of 101 crystal structures containing sulfathiazole (SLFZ). The structure set comprises five SLFZ polymorphs, 63 co-crystals, 30 salts and three other structures, standardised by application of dispersion-corrected density functional theory (DFT-D) calculations. The hydrogen bonds between SLFZ molecules define a broad range of motifs, from 3-D to 0-D. The topologies of the higher-dimensional motifs are dominated by the 3-D bnn and 2-D sql nets, each of which account for roughly one quarter of the structure set. The bnn net is principally seen in co-crystals where SLFZ generally does not form any hydrogen bond to the partner molecules. The sql net is seen in both co-crystals and salts where hydrogen bonds are formed between SLFZ and the partner molecules. Both the bnn and sql nets occur with a variety of specific donor/acceptor connectivity patterns, so the defined topological similarity does not immediately indicate structural similarity. Some isolated examples are identified of topological similarity between multi-component structures and the SLFZ polymorphs, but in general similarity between the polymorphs and multi-component structures is limited. The topological analysis is augmented by comparison of the shapes of the nodes extracted from each net, which represent the local geometry of each SLFZ molecule using only the centroids of connected SLFZ molecules. This reductive method is found to be effective to highlight fully isostructural groups and also to indicate sub-structure similarity and relationships between structures that may not emerge from a full geometrical comparison. This method may be a useful filter when seeking similarity within a large structure set. One new instance of 3-D isostructurality is identified, which was not evident from a previous geometrical analysis. Cases are also described where structures show close geometrical similarity but it is reasonable to assign different hydrogen-bond schemes. These examples illustrate the uncertainties and ambiguities inherent in tolerance-based methods to compare molecular crystal structures. [ABSTRACT FROM AUTHOR]

In this study, two new heteroleptic complexes with compositions [Ni(mtsq)1.85Cl0.15(dppe)](CH2Cl2)0.06(CH3OH)0.09 (Ni-mtsq) and [Cu(mtsq)(PPh3)2] (Cu-mtsq) (dppe = 1,2-bis-(diphenylphosphino)ethane; PPh3 = triphenylphosphane and mtsq = 3-ethoxycyclobutenedione-4-thiolate) have been synthesized and characterized by spectroscopy analyses as well as by single crystal X-ray diffraction technique. X-ray analyses reveal square planar geometry around Ni(II) in Ni-mtsq, where Ni(II) coordinates with two sulfur centres of two mtsq ligands with monodentate coordination and two phosphorus centres of the dppe ligand in chelating mode. Unlike Ni-mtsq, Cu(I) in Cu-mtsq adopts a tetrahedral geometry, which is satisfied by sulfur and oxygen centres of one mtsq ligand with a bidentate coordination mode and two phosphorus centres of two PPh3 ligands. The supramolecular architecture of both Ni-mtsq and Cu-mtsq is sustained by intermolecular C–H⋯π and O⋯H interactions. Also, Ni-mtsq exhibits intriguing intramolecular semicoordination Ni⋯O and π⋯π non-covalent interactions. The nature of these interactions has been addressed with the aid of Hirshfeld surface analysis, density functional theory and quantum theory of atoms in molecules (QTAIM) analyses and has been visualized with the help of non-covalent interactions reduced density gradient (NCI-RDG). Further, the emissive nature of Cu-mtsq in a solution and solid phase suggests aggregation-induced emission with a bathochromic shift in the solid phase as compared to the solution phase. Both complexes have been used as electrocatalysts for oxygen and hydrogen evolution reactions, which suggests that Cu-mtsq offers better catalysis due to the presence of a redox active, less hindered Cu(I) centre with an η10 of 600 mV and a Tafel slope of 228 mV dec−1 in the OER, while in HER too, Cu-mtsq exhibited the best onset potential of −0.36 V with an η10 of 647 mV. Also, homogeneous electrocatalysis for the HER for both complexes was investigated using trifluoroacetic acid as the hydrogen source, which suggests a better electrocatalytic performance of Cu-mtsq. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) capable of post-synthetic metalation (PSMet) have garnered significant interest as supports for catalytic metals. The Mn-based MOF, MnMOF-1 ([Mn3(L2Me)3] where L2Me = bis-(4-carboxyphenyl-3,5-dimethylpyrazolyl)methane), has been an exemplar for studying PSMet. Herein we investigate the synthesis of Mn-based MOFs from related flexible ditopic pyrazole carboxylate links, along with the formation of MOFs with similar tetratopic hinged linkers. We show for the first time that MnMOF-1 is likely a kinetic or metastable phase and a newly identified 2D layered material (MnMOF-2D) is the thermodynamically favoured product for this metal–linker combination. Formation of a MnMOF-1 structure with shorter linkers is thwarted by steric clashes that preclude the formation of the Mn3 cluster. This observation prompted the use of density functional theory (DFT) simulations that showed the target material to be very dense, highly strained and thereby energetically unfavourable, but potentially, a hypothetical MnMOF-1 structure with a longer phenylethynyl spacer would be energetically feasible. Finally, the predominance of 2D MOFs formed with shorter flexible links encouraged us to use tetratopic hinged linkers to form 3D frameworks, which was vindicated by the successful synthesis of two new porous 3D Mn-based MOFs, MnMOF-L4 and MnMOF-L5. These results highlight that reticular synthesis of MOFs formed with flexible, non-linear linkers is challenging. [ABSTRACT FROM AUTHOR]

Discovering novel magnetic materials is essential for advancing the spintronic technology with significant applications in data communication, data storage, quantum computing, etc. While density functional theory (DFT) has been widely used for designing materials, its high computational demand for estimating the magnetic ground states of even a single material limits its ability to explore the vast chemical design space to find the right materials for spintronic applications. In this work, we developed a computational framework combining generative adversarial networks (GANs), machine learning (ML) classifiers, and DFT for de novo magnetic material discovery. We used the CubicGAN generative crystal structure design model for creating new ternary cubic structures. Machine learning classifiers were developed with around 90% accuracy to screen candidate ternary magnetic materials, which were then subjected to DFT based stability validation. Our calculations discovered and confirmed that Na6TcO6, K6TcO6, and BaCuF6 are stable ferromagnetic compounds, while Rb6IrO6 is a stable antiferromagnetic material. All these materials have zero energy above hull. Moreover, Na6TcO6 and BaCuF6 are found to be half metals that are highly favorable for spintronic applications. Due to the structural differences, the A6MO6 materials have a higher thermal capacity (Cv) compared to BaCuF6. At 300 K temperature, the Cv of the A6MO6 materials is around 1100 J K−1 mol−1 and that of BaCuF6 is about 176 J K−1 mol−1. This work demonstrates the promising potential of deep generative design for discovering novel functional materials. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) simulations were performed to study the effects of structure, interaction and mechanical properties of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/benzotrifuroxan (CL-20/BTF) under a hydrostatic pressure in the range of 0–100 GPa. The calculated structure agrees well with the experimental data at ambient pressure and 293 K. The CL-20/BTF cocrystal exhibits an anisotropic compression behavior, as shown by the change in lattice constants with pressure, because it is more difficult to compress along the b-axis. In addition, the band gap values decrease rapidly from 0 GPa to 40 Gpa and then decrease slowly with pressure increasing from 50 GPa to 100 GPa. Furthermore, the analysis of the active bond reveals that two types of O–N bonds in the furoxan group and four types of N–N bonds in CL-20 have significant responses to pressure. The Hirshfeld surface gives an insight into intermolecular interaction, and combining the analysis of the Hirshfeld surface and two-dimensional fingerprint plots shows that intermolecular interaction mainly comes from hydrogen bonding interactions and NO2–π interaction in CL-20/BTF cocrystal. According to the stronger intermolecular interaction (sum of O⋯H/H⋯O, N⋯H/H⋯N, O⋯N/N⋯O and O⋯O) decreasing with increasing pressure, it can be speculated that the impact sensitivity of CL-20/BTF increases as the pressure increases. The mechanical properties reveal that this cocrystal shows an increase in ductility, deformation resistance and stiffness with increasing pressure. The elastic anisotropy indicates that the CL-20/BTF varies anisotropically under pressure in the range of 0–100 GPa but is near isotropy level under 20 GPa. [ABSTRACT FROM AUTHOR]

The slow kinetics of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in air cathodes severely limit the development of reversible zinc–air batteries. Thus, bifunctional oxygen catalysts with excellent electrocatalytic activity and durability for both the oxygen reduction and oxygen evolution reactions (ORR/OER) are keys to achieving long-term rechargeable zinc–air batteries. However, it remains challenging to further improve the performance by adding more active sites. To address this, a series of nitrogen-doped carbon (CN) with NiCo alloys has been synthesized by pyrolyzing a simple bimetal zeolitic-imidazolate framework (ZIF) and then evenly loaded with metallic Ru nanoparticles, resulting in Ru–NiCo/NC samples. Benefiting from the large pore volume and high activities, the Ru–NiCo/NC electrocatalysts exhibit higher ORR (E1/2 = 0.84 V) and OER performance with an overpotential of 342 mV at 10 mA cm−2, along with superior cycle stability. More significantly, when employed in rechargeable zinc–air batteries, Ru–NiCo/NC catalysts demonstrate a high power density of 132.3 mW cm−2, significantly outperforming Pt and Ru-based zinc–air batteries. Additionally, DFT (density functional theory) results indicate that the addition of Ru leads to a downshift of the d-band center from the Fermi level, which benefits the reduction of energy barriers and enhances the desorption of O-containing intermediates. This work provides a feasible strategy for developing efficient and high-performance bifunctional electrocatalysts. [ABSTRACT FROM AUTHOR]

Gold–silver (Au–Ag) nanocrystals with a combination of concave surface and hollow interior are of great interest due to their distinctive structural merits. Herein, we introduce a facile strategy based on seed surface doping to create concave Au@AuAg yolk–shell nanocubes with surface concavity (Au@AuAg YSCNCs), and examine their intriguing properties in optics and catalysis. In particular, the Au@Ag core–shell nanocubes are generated and reacted with sodium thiosulfate, followed by the addition of HAuCl4 to remove Ag atoms on the side walls and deposit Au/Ag atoms on the corners/edges via the galvanic replacement reaction. UV-vis extinction spectra show that compared to Au@Ag core–shell nanocubes, the current Au@AuAg YSCNCs enable a redshift in the major absorption peak, which should be attributed to the increase in charge polarization regions. Meanwhile, the structural advantage is validated using the reduction of 4-nitrophenol as the model reaction. In particular, the current Au@AuAg YSCNCs exhibit an enhanced catalytic efficiency compared to the Au@Ag core–shell nanocubes. Mechanism study using density functional theory reveals that the structural advantage boosts the catalytic activity by upshifting the d-band center and thus lowering the activation barrier. The current study provides a feasible strategy to integrate two structural features (e.g., concave surface and hollow interior) into one AuAg nano-entity, which could be potentially extended to other metals and/or alloys. [ABSTRACT FROM AUTHOR]

The document titled "Front cover" is from the journal CrystEngComm, published on July 28, 2024. The document discusses the adsorption of 5-fluorouracil, an anticancer drug, in faujasite-type zeolites. The study aims to understand the storage and release of the drug using density functional theory calculations. The document also mentions professional recognition and career advancement opportunities in the field of science. [Extracted from the article]

Oxygen vacancies, hydrogen vacancies and potassium vacancies are common intrinsic point defects in potassium dihydrogen phosphate (KDP) crystals and can combine to form cluster defects. In this work, the stability of VO2+ + 2VK−, VO2+ + VK− + VH− and VO2+ + 2VH− cluster defects, as well as the defect-induced structural and electronic properties and optical absorption in KDP crystals, is investigated by hybrid density functional theory. Cluster defects composed of oxygen vacancies and their nearest hydrogen vacancies or potassium vacancies can be stable in KDP crystals. VO2+ + 2VK−, VO2+ + VK− + VH− and VO2+ + 2VH− cluster defects introduce large relaxation to the O–H bonds linking to the PO4 group in KDP crystals, and the structural instability of the crystal could be quickly enhanced with the increase of these cluster defects. This structural instability is detrimental to the laser induced damage thresholds of KDP crystals. The band gaps of KDP crystals are shortened to 6.6 eV, 6.4 eV, and 6.4 eV by VO2+ + 2VK− cluster defects, VO2+ + VK− + VH− cluster defects and VO2+ + 2VH− cluster defects, respectively. Under a 355 nm laser, this shortening may cause two-photon absorption, resulting in the reduction of the laser induced damage threshold of the KDP crystal. The electron transition between oxygen vacancies and hydrogen vacancies introduces an extra absorption peak at 6.4 eV. This work provides a good basis for deeply understanding the structural and electronic properties and optical absorption of oxygen vacancy cluster defects in the KDP crystal. [ABSTRACT FROM AUTHOR]

Two polytypic heterolayered salt-inclusion chalcogenides, o-[Na2Cl]GaQ2 and t-[Na2Cl]GaQ2, were obtained via a NaCl/NaI flux-assisted synthesis, as part of an investigation of the Na–Ga–Q (Q = S and Se) system. The use of a different flux, NaBr/NaI, in the Na–Ga–Se system did not lead to the formation of salt-inclusion phases, but instead the novel Na2GaSe3 and Na4Ga2Se5 phases were obtained. Thermal and electronic properties of [Na2Cl]GaS2 materials were investigated with differential scanning calorimetry, post-quenching ex situ powder X-ray diffraction (PXRD), high-temperature PXRD, and enthalpy and electronic structure calculations via density functional theory. Those studies determined the absence of any temperature-induced phase transition between the o-[Na2Cl]GaS2 and t-[Na2Cl]GaS2 polytypic compounds. Moreover, we probed the suitability of the heterolayered [Na2Cl]GaS2 single crystals as a sorbent for UO22+ uptake and monitored this process by energy-dispersive and infrared spectroscopies and PXRD, which revealed that the [Na2Cl]+ insert could be exchanged with UO22+ on the surface while the UO22+ intercalation decomposes the [Na2Cl]GaS2 structure. [ABSTRACT FROM AUTHOR]

To explore the effects of lattice vibration and molecular interaction on their formation and structure, as well as their mechanical properties, vanillin cocrystals with nicotinamide and isonicotinamide were synthesized and characterized by time-domain Terahertz spectroscopy. The lattice vibrations of these cocrystals, as well as their individual components, were investigated using the dispersion-corrected density functional theory. The simulated terahertz spectra successfully were highly consistent with their experimental spectra. Typical intensive modes of vanillin and the cocrystals were discussed in terms of the motions of hydrogen bonds. The effect of lattice vibration on cocrystal structures was further studied to gain insights into their thermodynamic stability. Geometrical values of the computationally optimized structure were calculated using density functional theory at B3LYP/6-31(d,p) to obtain the highest occupied molecular orbitals and lowest unoccupied molecular orbitals of the cocrystal. The Hirshfeld surface and the molecular electrostatic potential were explored to study the interactions between the individual component of the cocrystals. The mechanical properties of the cocrystals were also calculated using modern quantum chemical methods. This study further highlights the consistency of computational results with crystallographic values, ensuring that the computational modeling of the cocrystals is equally important for predicting their stable geometries and applications. [ABSTRACT FROM AUTHOR]

Two new multicomponent crystalline phases of fenbendazole (FNB), a benzimidazole anthelmintic agent, with maleic and oxalic acids have been prepared, and their structural and physicochemical properties carefully investigated. The crystal structures of the solid forms have been determined from powder X-ray diffraction data. The positions of dynamic hydrogen atoms have been further refined via dispersion-corrected density functional theory calculations, which validated the salt nature of the resulting solid forms by demonstrating proton transport from the corresponding acids to the FNB molecule. The in vitro dissolution performance of the solid forms in aqueous media at different pH values, as well as the in vivo anthelmintic efficacy of fenbendazole on the laboratory model of Trichinella spiralis infection in mice have been evaluated and compared to that of the previously reported salt of FNB with p-toluenesulfonic acid. A relationship between the in vitro dissolution characteristics and the in vivo therapeutic action has been revealed and discussed. [ABSTRACT FROM AUTHOR]

Active pharmaceutical ingredients (APIs) and selected coformers were studied in crystalline self-environment, in selected co-crystal structures, and gas phase. To obtain comparable geometries from experimental crystal structures, we rely on fast quantum mechanical GFN2-XTB molecule-in-cluster optimizations. Optimized crystal structures are first analysed in terms of molecule-pair interaction energies, by subdividing a cluster generated from asymmetric unit content through space-group symmetry into pairs of molecules. Accurate energies are then obtained by single-point molecular orbital (MO/MO) two layer "ONIOM" energy partitioning, comparing the same molecules in different crystal environments. Clusters approximate the local environment of a crystal structure for ONIOM. The pre-processor program BAERLAUCH (Acta. Cryst. A 2012) was used to set up all cluster computations. Solid-state computations using dispersion-corrected density functional theory provide reference results. ONIOM partitioned energies shed light on the driving force of co-crystal formation, with the energy gain from the complementarity of molecule-pair wavefunctions in such structures being the main driving force. It follows that improving prediction of co-crystal structure formation beyond current approaches, e.g. COSMO-RS excess enthalpies, statistics from structural databases or full crystal structure prediction is possible by finding complementary molecule-pairs through conformational sampling, as ultimately exemplified. [ABSTRACT FROM AUTHOR]

Two new dinuclear cobalt(II) complexes, [(H2O)CoIIL1(μ-O2CR1)CoII(NCS)] (1) and [(DMSO)CoIIL2(μ-O2CR2)CoII(NCS)] (2) (H2L1 = (2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)bis(6-methoxyphenol), H2L2 = (2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)bis(6-ethoxyphenol), R1CO2H = 3-methyl-4-nitrobenzoic acid, and R2CO2H = 4-methyl-3-nitrobenzoic acid), were synthesized using multidentate N,O-donor ligands with two pockets. Each complex was characterized using single crystal X-ray diffraction and spectral analysis. The noncovalent interactions were analyzed using density functional theory (DFT) calculations. In addition, the optical properties of the complexes were studied with a focus on the band gaps. Both complexes were utilized for the fabrication of semiconducting Schottky devices. [ABSTRACT FROM AUTHOR]

A Cu(II)-based metal–organic framework (MOF) [Cu(muco)(3,5-DCP)]n (1) has been synthesized by using linear rigid aliphatic dicarboxylic acid, trans,trans-muconic acid (H2muco) and 3,5-dichloropyridine (3,5-DCP) as an auxiliary ligand. The MOF adopts a square-grid two-dimensional (2D) structure with paddle-wheel [Cu2(OOC)4] robust secondary building units (SBUs). The 3,5-DCP ligands are perpendicularly projected from the SBUs at both sides and undergo interdigitation via antiparallel π⋯π stacking interactions among 3,5-DCP ligands to fabricate three-dimensional (3D) supramolecular architecture. The π⋯π interactions favour the formation of Cl⋯Cl stacking contacts. These non-covalent interactions are further validated by density functional theory (DFT) calculation. In addition, the synthesized MOF is tested for conductivity measurements via current density–voltage characteristics, as well as impedance spectroscopy, which reveal that the MOF is semiconducting in nature and can be used as a Schottky diode. [ABSTRACT FROM AUTHOR]

The combination of 3-nitro-1,2,4-triazol-5-one (NTO) and ammonium perchlorate (AP) can effectively utilize the advantages of both materials. The interaction mechanism between NTO and AP is important for the feasibility of combining these materials and can provide theoretical guidance for the design of such a combination. Thus, in order to figure out the interaction mechanism between NTO and AP on multiple scales, density functional theory (DFT) and ab initio molecular dynamic (AIMD) studies have been carried out. Several possible configurations are obtained from a large number of randomly generated NTO and AP dimers using DFT. To understand the interaction mechanism, binding energies, energy decomposition, electrostatic potential (ESP), electron density topology, and independent gradient model based on the Hirshfeld partition (IGMH) analyses were carried out. To have further insights into the combination of NTO and AP, the AIMD method was used to predict the co-crystal structure of NTO and AP, and the electron structure, thermal decomposition, and shock Hugoniot curves were calculated. All the calculation results show the high feasibility of the combination of NTO and AP to form NTO/AP co-crystal with excellent performance. [ABSTRACT FROM AUTHOR]

Five new charge-transfer (CT) complexes of structurally varied 1,2,5-chalcogenadiazoles (monocyclic, 6-5 bicyclic and 6-6-5 tricyclic; chalcogen = S, Se and Te) with tetrathiafulvalenes (TTF and its bis(ethylenedithio) derivative BEDT-TTF) were obtained by co-crystallization of donor and acceptor components and characterized by X-ray diffraction and UV-vis spectroscopy in combination with density functional theory calculations. Bonding analyses were carried out with the quantum theory of atoms in molecules and Hirshfeld surface and non-covalent interaction analyses, accompanied by calculations of model energies of molecular pairs. According to these calculations, the complexes are rather weakly bonded by predominantly electrostatic interactions with significant contributions from dispersion interactions. The main structural motifs are assigned to π-stacking interactions and σ-hole driven hydrogen and chalcogen bonding. CT magnitudes vary between 0.09 and 0.37 e, and the CT bands in the UV-vis spectra of the complexes lie in the range of 550–750 nm. [ABSTRACT FROM AUTHOR]

The Fe3+ ion is the most common impurity ion in potassium dihydrogen phosphate (KDP) and can combine with hydrogen vacancies to form cluster defects, which can lead to optical damage of the KDP crystal. In this study, the effect of the FeK2+ + 2VH− cluster on the crystal structure, electronic, and optical properties of KDP crystals were investigated using hybrid density functional theory, and the mechanism of Fe3+ ions lowering the laser-induced damage threshold of the KDP crystal was analyzed. The damage from the FeK2+ + 2VH− cluster defect to the crystal structure of the KDP crystal was found to be greater than that from hydrogen vacancies due to the large lattice relaxation introduced by FeK2+ defects. The FeK2+ defect introduces two defect states (at 2.4 eV and 6.6 eV) into the bandgap of the KDP crystal as well as absorption peaks at around 278 nm in the xy plane. When FeK2+ + 2VH− cluster defects form, hydrogen vacancies induce an increase in charge density around the O atoms bonded to FeK2+, which slightly alters the interaction of the electronic states of the FeK2+ and O atoms. These cluster defects have an influence on the electronic and optical properties via charge transfer in the xy plane in the KDP crystal. This work provides a good suggestion to improve the laser-induced damage threshold of KDP crystals by decreasing the concentration of cluster defects in KDP crystals. [ABSTRACT FROM AUTHOR]

Single crystals of formamidinium (FA)–lead–chloride–dimethyl sulfoxide (DMSO) solvate, [CH(NH2)2]Pb(C2H6OS)Cl3, were synthesized from a DMSO ((CH3)2SO) solution in which FA–chloride (CH(NH2)2Cl) and lead(II) chloride (PbCl2) were dissolved. Single-crystal X-ray diffraction studies revealed that [CH(NH2)2]Pb(C2H6OS)Cl3 exhibited a monoclinic (P21/c) symmetry in the temperature range of 113–293 K. Interestingly, the oxygen atom of DMSO was involved in the distorted [PbOCl5] octahedra, which form a [Pb2O2Cl9] dimer unit by edge-sharing. These dimer units form a pseudo-2D zigzag layer elongated parallel to the (100) plane via corner sharing. The FA+ cation was structurally ordered and aligned between the pseudo-2D zigzag layers at the voids surrounded by the [Pb2O2Cl9] dimer units. The formation enthalpy of the DMSO solvate calculated using the density functional theory method explains the phase stability of the FAPbCl3–DMSO solvate. [ABSTRACT FROM AUTHOR]

LiFePO4 (LFP) microparticles with a faceted crystal habit have been fabricated by hydrothermal synthesis. Three different surfactants were employed to control the crystal habits of the particles, which ranged from cubes over different diamond-shaped platelets to pyramids. Crystallographic models of the particles with the lowest matching Miller indices were determined based on the data acquired by atomic force microscopy (AFM) and gave insight into the synthesis process. The analysis of the crystal facets of the observed particles implied the importance of the (2 1 0) facet, which was previously neglected. First-principles investigations based on density functional theory revealed a surface energy for (2 1 0) of 0.83 J m−2, contributing 2.5% of the surface area of the equilibrium shape of LFP crystals. [ABSTRACT FROM AUTHOR]

With an increasing need to make preparative chemistry more sustainable, mechanochemistry receives much attention. It is attractive for synthesizing open coordination or covalent frameworks, offering an unprecedented level of synthetic control while reducing solvent usage and frequently accessing products not available by conventional synthetic methods. Here, we present a sustainable solid form screening of 2,6-diaminopurine (DAP) nucleobase, an important hydrogen-bonded framework building block. DAP is well known for treating genetic diseases and occurring as a nucleobase in viral DNA, yet its solid-state chemistry is unknown. With a total solvent consumption of 0.6 mL, we discovered five new DAP solid forms by mechanochemical and thermal routines, including a polymorphic pair of DAP hydrogen-bonded organic frameworks (HOFs). Two DAP-HOF polymorphs formed selectively by choosing the liquid additive in liquid-assisted grinding (LAG). Monitoring by in situ Raman spectroscopy revealed different formation profiles for each DAP-HOF polymorph, and nitrogen adsorption isotherms confirmed their permanent porosities. The density functional theory (DFT) analysis established the relative thermodynamic stability of crystallographically characterized DAP solid forms. Our results demonstrate the ability of mechanochemistry to control HOF polymorphism, which might be critical for their properties and subsequent applications. In a broader perspective, this work opens the door for sustainable studies on nucleobase-inspired HOF materials. [ABSTRACT FROM AUTHOR]

For energy conversion and storage, the electrochemical oxygen evolution process (OER) is the crucial half-reaction process. The amphiprotic characteristics of sulfamic acid are due to its amine and sulphonic acid functional groups. Metal-based catalysts can be utilized to fabricate bimetallic and dual-ligand linked FeCo–SA/DABCO nanosheets with improved catalytic performance. The crystal structure of bimetallic FeCo–SA/DABCO consisted of alternating organic hydrocarbons SA and DABCO and inorganic metal–oxygen layers. FeCo–SA/DABCO provided an overpotential (η10) of 290 mV to achieve a current density of 10 mA cm−2 together with a small Tafel slope of 112.79 mV dec−1 and also exhibited long-term durability. Electrochemical results showed that FeCo–SA/DABCO was superior to FeCo–SA and Co–SA/DABCO. Density functional theory calculations indicated that the theoretical overpotential of FeCo–SA/DABCO is 0.62 eV, which was lower than that of FeCo–SA. The introduction of composite SA/DABCO ligands can change the rate-determining step, which can improve the conductivity and reduce the reaction barrier for the formation of intermediates, thereby affecting the catalytic activity and changing the overall electron transfer capacity. [ABSTRACT FROM AUTHOR]

Unusual intermolecular π-stacking in a new charge transfer salt of pyrene (Py), (Py)2+(Ga2Cl7)−, has been observed. The structure obtained by single crystal X-ray crystallography indicates π-stacks of pyrene which were analyzed using a combination of density functional theory and the analysis of the bond length alternation patterns in the pyrene molecules in different charge states. There are relatively few crystal structures of charge transfer salts of pyrene in the literature, and this structure shows a unique charge separation in which half of the pyrenes are nearly neutral while the other half carry approximately +1 charge in an alternating fashion along the 1D stacks balancing one electron charge transfer to each (Ga2Cl7)− anion. The charge localization is attributed to the incomplete inter-pyrene overlap of the singly occupied molecular orbitals. [ABSTRACT FROM AUTHOR]

The appearance of different polymorphs at surfaces is a well-known phenomenon for organic molecules. Here the phenoxazine molecule, a small molecule with a rather rigid conformation whose bulk crystal structure (form 1) could be solved recently, is studied. The molecule was crystallized on silicon oxide surfaces from solution by drop casting and spin coating using five different solvents. Besides the concentration ranging from 0.8 g l−1 to 50 g l−1, the evaporation rate of the solvent was also controlled. By this process a new polymorph (form 2) was found which preferably forms at high solvent evaporation rates (e.g. by spin coating). The crystal structure was solved by combining grazing incidence X-ray diffraction with theoretical methods of packing determination based on molecular dynamics and density functional theory. Severe disorder is found within the structure of the new polymorph, similar to those known for form 1. Comparing the phases of phenoxazine with the results of the surface crystallization studies here reveals that the new phase is a kinetically driven phase of metastable character. This work shows that surface crystallization is a valuable tool to search for new polymorphs of organic molecules and to characterise them in terms of their kinetic appearance and thermodynamic stability. [ABSTRACT FROM AUTHOR]

Charge transfer cocrystals offer an opportunity to construct high performance organic photothermal materials. However, it is still challenging to modulate the degree of charge transfer of cocrystals to achieve rationally designed photothermal functional materials. Herein three charge transfer cocrystals composed of carbazole (CZ)/3,6-dichlorocarbazole (ClCZ)/3,6-dibromocarbazole (BrCZ) as π-donors (D) and 7,7′,8,8′-tetracyanoquinodimethane (TCNQ) as a π-acceptor (A), namely CZ/TCNQ, ClCZ/TCNQ and BrCZ/TCNQ, were obtained and subjected to spectroscopic and photothermal conversion studies as well as density functional theory calculations. The crystal structures reveal that the donor and acceptor molecules of each cocrystal adopt a ⋯DADADA⋯ mixed stack structure. With steric hindrance and electron withdrawing effects of chlorine/bromine atoms on carbazole, the charge transfer degree of CZ/TCNQ is reduced from 0.25 to 0.07 for ClCZ/TCNQ and 0.03 for BrCZ/TCNQ. The three cocrystals display broad absorption over the 300 to 900 nm range without significant photon emission. The near-infrared photothermal conversion efficiency reaches 53.7% (CZ/TCNQ), 48.5% (ClCZ/TCNQ) and 32.0% (BrCZ/TCNQ), respectively. These cocrystals have narrowed HOMO–LUMO gaps, which is attributed to the strong charge transfer transition and agrees with the photophysical and photothermal conversion properties of the cocrystals. This study demonstrates that the modulation of the charge transfer degree by intelligent design of donor–acceptor pairs can be an effective means to regulate the photothermal conversion efficiency of charge transfer cocrystals. Finally, CZ/TCNQ was successfully applied as an appealing photothermal material in photothermal imaging and functional electrical device control. [ABSTRACT FROM AUTHOR]

Regular detection of blood glucose levels is a critical indicator for effective diabetes management. Owing to the intrinsic highly sensitive nature of enzymes, the performance of enzymatic glucose sensors is typically impacted by unwanted dependencies on pH, temperature and humidity. Correspondingly, the development of robust enzyme-free glucose sensors is desired due to their potential to improve upon the operational flexibility of traditional systems. In this study, a new coordination polymer (CP) incorporating melamine (Mel), biphenyl-4,4′-dicarboxylate (BPDC2−) co-ligands and Zn(II) metal nodes, [Zn2(BPDC)1Mel0.5–Mel0.5]·(DMF0.6) {denoted CP1}, was synthesised and characterized for non-enzymatic glucose sensing. Here, the 2D layers are connected by hydrogen bond (H-bond) interactions between the interstitial melamine molecules. In addition to conventional characterization methods, we also used density functional theory (DFT) calculations and variable temperature Raman spectroscopy to computationally and experimentally explore the H-bond interactions in CP1. CP1 was deposited onto a glassy carbon (GC) electrode to facilitate its incorporation into an electrochemical sensing device. When used as an electrochemical glucose sensor, the CP1/GC electrode exhibited accurate clinical performance characteristics, with a wide linear sensing range extending from 5.6 μM to 5.56 mM (R2 = 0.9852) and with a high sensitivity of 517.36 μA mM−1 cm−2. Low sample loadings are a further important advantage associated with this CP-based non-enzymatic glucose sensor. [ABSTRACT FROM AUTHOR]

Two new 2,6-diacetylpyridine bis(nicotinoylhydrazone) coordination polymers with the general formula {[MIIL]·xsolvent}n, in which MII = Fe, Co, were prepared solvothermally and characterized by various methods. Both compounds exhibit isostructurality with different solvents with our previously reported homo- and heteronuclear coordination layers (MII = Mn, Zn, Cd, MnZn, Zn0.75Cd1.25). A comprehensive investigation of the isometricity revealed the existence of a high degree of similarity for five pairs, medium similarity for six pairs, and low similarity for ten pairs. Despite the fact that the Mn(II) and Zn(II) coordination polymers are isostructural to each other, they are enantiomers of other compounds. The photoluminescence study was performed on all seven compounds and some of them were found to exhibit high photoluminescence intensities. Density functional theory has been used to estimate the nonlinear optical and thermoelectric properties of the given series of coordination polymers. It has been shown that, regardless of the different degrees of isostructurality of the studied coordination polymers, their properties significantly depend on the nature of the metal ions. [ABSTRACT FROM AUTHOR]

The reaction between di-n-butyltin(IV) chloride with the dinegative dithiolate ligand 2-(cyanobenzo)nitrile-dithiolate in two different alcoholic media viz. methyl alcohol and ethyl alcohol fortuitously yielded di-n-butyltin(IV)-bis-(1-methoxy-isoquinoline-4-nitrile thiolate) (Sn-Me) and di-n-butyltin(IV)-bis-(1-ethoxy-isoquinoline-4-nitrile thiolate) (Sn-Et). Similarly the reaction of di-n-butyltin(IV) chloride with 2-methoxy phenyl acetonitrile dithiolate yielded di-n-butyltin(IV)-2-methoxy phenyl acetonitrile dithiolate (2-MeCN-Sn). These compounds have been characterized by micro analyses, IR, UV-vis, 1H, 13C and 119Sn NMR spectroscopy as well as by single crystal X-ray diffraction technique in case of Sn-Et, Sn-Me. The X-ray analyses revealed that in both Sn-Me and Sn-Et, the Sn(IV) center adopts a skew trapezoidal bipyramidal geometry with Sn at the centre and two sulfur and two ring nitrogen atoms of 1-alkoxy-isoquinoline-4-nitrile thiolates are at the corners of a trapezoid with two n-butyl groups adopting axial positions resembling the cis–trans pathway. Both Sn-Me and Sn-Et display varied types of non-covalent interactions. The nature of these interactions has been addressed with the aid of Hirshfeld surface analysis, density functional theory and quantum theory of atoms-in-molecules (QTAIM) analyses. [ABSTRACT FROM AUTHOR]

By annealing/sulfuring of coordination compound (CC) precursors, [LaxFe1−x(H2O)8Fe(CN)6]·2hmt (x = 0, 0.33 and 0.5) (hmt = hexamethylenetetramine), FeS2/N-doped carbon (NC), La-doped FeS2/NC-0.33 and La-doped FeS2/NC-0.5 were synthesized. All of them can electrolyze the oxygen evolution reaction (OER). Among them, the optimum sample La-doped FeS2/NC-0.33 shows a low overpotential (η) of 217/239 mV at 30/50 mA cm−2, which is comparable and even superior to commercial RuO2 and many iron sulfide-based catalysts reported previously. Furthermore, La-doped FeS2/NC-0.33 exhibits long-term OER activity with the transformation of FeS2 → FeOOH over 60 h electrolysis at 20 mA cm−2. In addition, density functional theory (DFT) simulations reveal that the rate-determining steps on La-doped FeS2 and FeS2 (200) surfaces are the formation of O2 and Fe*–OH, respectively, and La-doped FeS2 exhibits a less ΔGmax value of 1.585 eV with a smaller η value of 0.355 V, which is attributed to their different d-band centers before and after La-doping. [ABSTRACT FROM AUTHOR]

The polymorphic Pd(II)–nitrite complex [Pd(bpy4dca)(NO2)2] (1) (bpy4dca = 2,2′-bipyridine-4,4′-dicarboxylic acid methyl ester) is shown to undergo photoinduced nitro → nitrito linkage isomer switching in two crystal forms, to varying excited state population levels. Detailed photocrystallographic kinetic studies, structural analyses of the ground and photoexcited states and density functional theory calculations all combine to explain the unusually high maximum excited state population of 80% in 1, where other linkage isomer complexes containing strong chromophore co-ligands have traditionally been challenging to excite. Comparison of the photo-response in crystals for forms I and II reveals that, while the local crystal packing environment has a role in controlling the maximum photostationary population that can be achieved, the rate of isomerisation is comparable across different nitrite ligand environments. Our results reinforce the hypothesis that a complex combination of steric, electronic and kinetic factors govern the progress of linkage isomer switching in the solid-state and highlight the need for better understanding of the structural dynamics involved in isomer switching at the molecular level. [ABSTRACT FROM AUTHOR]

This work reports a combined computational and experimental analysis of the crystal structure of the cancer drug tipiracil hydrochloride in the form of a methanol solvate–hydrate (4 : 1 : 3, molar ratio). The crystal structure shows a complex network of H-bonds with static discrete disorder in two out of the three symmetry-independent solvent molecules, which has been studied by means of DVS and TGA techniques. MEP surface calculations shows a region of positive potential (σ-hole) along the C–Cl bond, which induces the formation of Cl⋯O contacts that are relevant in the crystal packing. The hydrogen and halogen bonding assemblies were further analyzed using density functional theory (DFT), the quantum theory of "atom-in-molecules" (QTAIM) and the noncovalent interaction plot (NCIplot). [ABSTRACT FROM AUTHOR]

Pd-based nanocatalysts are critical to the commercialization of direct ethanol fuel cells (DEFCs); however, the synthesis of Pd-based binary alloy nanocrystals with well-defined branches is still a great challenge. Here we report a facile seed-mediated approach for the synthesis of PdSn alloy octopods with precisely controlled branches and tunable compositions through the Stranski–Krastanov growth mode. The PdSn octopod-like catalysts exhibited prominently enhanced catalytic activity and stability towards the ethanol oxidation reaction (EOR) with respect to commercial Pd/C in alkaline solution. Specifically, Pd72Sn28 octopods exhibited the highest mass and specific activities (2701 mA mg−1 and 11.27 mA cm−2), which were 2.1 and 6.7 times higher than those of commercial Pd/C, respectively. Density functional theory (DFT) calculations reveal that the lowest d-band center of the (100) surface of Pd72Sn28 weakens the adsorption of the acetate-evolution key intermediate *CH3CO, leading to the best catalytic activity towards the EOR. [ABSTRACT FROM AUTHOR]

Mechanochemical synthesis provides new pathways for the rational design of multi-component crystals (MCCs) involving anionic or cationic components that offer molecular-level architectures unavailable to MCCs comprising strictly neutral components. Structural characterization of the products of mechanochemical syntheses is essential for divining clear relationships between the nature of coformers, milling conditions, reaction mechanisms, and intermolecular bonding. Notably, when powder X-ray diffraction and solid-state NMR (SSNMR) are combined with plane-wave density functional theory (DFT) calculations, they offer opportunities for NMR crystallographic solutions and structural refinements. Herein, we report mechanochemical syntheses of five urea-containing MCCs of the form NR4Cl:xUrea·yH2O (R = H, Et, n-Pr; x = 1, 2, 3; y = 0, 2), which can be made in high yields (> ca. 99%) and great rapidity (<40 minutes). We demonstrate the utility of 35Cl SSNMR for providing distinct fingerprints for each urea MCC and detecting chlorine-containing impurities. Dispersion-corrected plane-wave DFT-D2* calculations are used for structural refinement and relating 35Cl electric field gradient (EFG) tensors and chloride ion hydrogen bonding environments. Finally, ab initio molecular dynamics calculations are used to study the impact of molecular motions on 35Cl EFG tensors, and their concomitant use for site assignment and NMR crystallography. Together, these techniques show great promise for future development of crystal structure prediction protocols using NMR of quadrupolar nuclei. [ABSTRACT FROM AUTHOR]