CrystEngComm最新文献

Cytidine 5′-monophosphate (CMP), despite its highly important biological function (as a basic component of nucleic acids), is one of the least studied nucleotides in terms of structural nature. In this work we present crystallographic studies of a series of CMP crystals in acidic form (the crystal structure of which has not been described in the literature). In addition to the determination of new polymorphs and varieties of hydrates and anhydrates of CMP, we describe structural changes caused by its temperature-, vacuum- and humidity-induced dehydration and rehydration. We complement the variable-temperature SC-XRD and 3D electron diffraction (3D ED) studies with thermal analysis (TGA/DTA) and variable-temperature micro-PXRD experiments. In the field of the described research results, we indicate and describe the most important types of intermolecular interactions, including hydrogen bonds and lone pair (lp)⋯π interactions. This, especially in light of dehydration, can be particularly valuable in the pharmaceutical field, and not only with regard to the nucleotide-based drugs.

A new class of hybrid MOFs were prepared based on γ-cyclodextrin (γ-CD) and food-origin organic acids via crystal growth utilizing γ-CD as a primary building block and food-origin organic acids as a secondary building block; this was done as part of an organic counteranion co-assembly strategy. Three food-origin organic acids, cinnamic acid, coumaric acid, and ferulic acids, were converted into respective potassium salts. Subsequently, by applying a co-assembly strategy with γ-CD via crystal growth, hybrid MOFs were prepared. These organic counteranions, cinnamate, coumarate, and ferulate, were selected to build the hybrid γ-CD MOF to unravel the substituent effect of functional groups in the backbone of organic counteranion on the properties of the hybrid CD MOFs. The effect of changing the crystallization solvent on the overall charge balance of these hybrid γ-CD MOFs during organic counteranion co-assembly was evaluated through ¹H and ¹³C inverse-gated ¹H decoupled spectra. In addition, we also report the use of the formation reaction of silver nanoparticles to test the effect of substituents on the stability of hybrid CD MOFs derived from γ-CD and food-origin organic acids.

Three new positional isomeric 1,2-bis(diphenylphosphino)ethane (dppe) appended nickel(II) dithiolates, namely, [Ni(dppe)2-cyano-2-(o-methoxyphenyl)ethene-1,1-dithiolate] (Ni-L1), [Ni(dppe)2-cyano-2-(m-methoxyphenyl)ethene-1,1-dithiolate] (Ni-L2) and [Ni(dppe)2-cyano-2-(p-methoxyphenyl)ethene-1,1-dithiolate] (Ni-L3), were synthesized and characterized using spectroscopic and single crystal X-ray analyses. Single crystal X-ray diffraction studies suggested that in all the three complexes, the immediate geometry around the nickel(II) was distorted square planar, which was defined by two sulfur and two phosphorus centres of dithiolate and dppe ligands, respectively, in a bidentate chelating manner. The supramolecular architectures of these complexes were sustained by intermolecular π⋯π, C–H⋯π, N⋯H, O⋯H and S⋯H interactions, and the nature of these interactions was studied with the aid of Hirshfeld surface analysis. The positional isomeric methoxy group engendered trimeric and dimeric motifs for Ni-L1 and Ni-L2, respectively, while it led to the chain formation in Ni-L3, thereby highlighting the influence of the position of the methoxy group on supramolecular frameworks. The heterogeneous electrocatalytic properties of these complexes in the oxygen evolution reaction (OER) were studied using modified glassy carbon electrodes. Results indicated that the Ni-L3 is a superior electrocatalyst for the OER amongst all three complexes, which exhibited an onset potential of 1.56 V and a TOF of 0.05 s⁻¹. Thus, this study unveiled the influence of factors such as the position of the isomeric –OMe group, thedihedral angle between the NiS₂C₂ and –(C₆H₄-OMe) planes and natural charges on nickel center on the electrocatalytic properties of these complexes towards OER.

A multi-level memristor, implemented with inexpensive precursors and well-defined mechanisms, will be significant for the development of high-density memory in the coming big data era. Sulfur, a cheap element extracted from petroleum and natural gas, holds fascinating potential for use in information memory. In this work, a three-component hybrid, [Cu(Phen)₂I]₂·Cu₂I₄·S₈ (Phen = 1,10-phenanthroline), was synthesized. In this structure, strong π–π stacking interactions among Phen ligands, cuprophilic interactions in (Cu₂I₄)²⁻ anions, and C–H⋯I/S hydrogen bonds contributed to the formation of a quasi-3D network. A FTO/hybrid/Ag memristor was fabricated, exhibiting ternary memory performance with a high ON2/ON1/OFF current ratio (10^4.50/10^1.47/1) and a ternary yield of 68%. The memristor could operate at a high temperature of 185 °C. Based on the structural characteristics of the hybrid, FIB-SEM measurements on the Ag/hybrid/Ag model device, double logarithm analysis of the I–V curve, memory performance of the three individual precursors, and external voltage-dependent PXRD, its ternary resistive switching performance could be explained as follows: upon continuous external voltages, the transition OFF → ON1 was driven by enhanced π–π stacking interactions among the Phen ligands, and the current jump ON1 → ON2 resulted from the formation of a conductive S₈/(Cu₂I₄)²⁻ layer bearing cuprophilic interactions via S₈ relaxation. This works extends the strategy of sulfur relaxation in multi-level memories from coordinated polysulfides to uncoordinated ones. The use of inexpensive precursors, combined with the distinct structure–property correlation, provides a promising avenue for implementing novel high-density memristors.

In Czochralski (CZ)-Si, crystal-originated particles (COPs) and bulk micro-defects (BMDs), which are primarily composed of voids and O-precipitates (OPs), respectively, have profound influences on the properties of wafers and resultant electronic devices. Impurity doping can be an effective approach to adjusting the concentrations of COPs and BMDs as desired. To study the effect of N-doping on the defect behaviour, we carry out first-principles investigations into a series of defects at different scales containing N, vacancies (V), and/or O. Density-functional theory (DFT) calculations are performed with an advanced exchange-correlation functional to ensure the quantitative accuracy of our results. According to the optimised atomic structures and electron localisation functions, we identify several stable complexes, including V–O complexes, N₂, and N₂V₂, as there are no dangling bonds. We find that the voids favour octahedral shapes to minimise the number of dangling bonds on the surface. N atoms can reduce the surface energy of voids by annihilating such dangling bonds, and also the concentration of free V by forming stable N₂V₂ complexes. Therefore, the size of voids is likely to decrease in N-doped CZ (NCZ)-Si. For OPs, both homogeneous and heterogeneous nucleation processes are likely to take place. Our calculations indicate that V and N₂V₂ can serve as heterogeneous nucleation centres for OPs. Hence, N-doping is expected to enhance the formation of OPs. This work not only provides useful insights into the interaction among various defects in NCZ-Si, but also elucidates the microscopic mechanism of the N-doping effects on the behaviour of voids and OPs.

Correction for ‘Multinuclear coordination polymers based on Ag⋯Ag interaction: syntheses, structures, and luminescence properties’ by Hua-Yu Shi et al., CrystEngComm, 2014, 16, 5110–5120, https://doi.org/10.1039/C4CE00236A.

Aminoglutethimide (AG), a Biopharmaceutical Classification System II (BCSII) drug, is approved for treating certain patients with Cushing's syndrome and breast cancer. However, it is technically limited to clinical application due to poor aqueous solubility. The water solubility of AG can be enhanced through the utilization of the co-crystal method. To screen AG co-crystals, this work employed liquid-assisted grinding and slow solvent evaporation methods. Three novel co-crystals of AG were successfully synthesized based on NH₂–COOH supramolecular synthon theory. All co-crystals exhibited higher apparent solubility than pure AG in the dissolution experiments. The intermolecular interactions of the co-crystals were examined using single crystal X-ray diffraction along with other analytical methods to determine their crystal structures. The formation of co-crystals was dominated by N–H⋯O hydrogen bonds in molecular electrostatic potential (MEP) analysis. To further explore and visualize the intermolecular interactions that form co-crystals, Hirshfeld surface (HS) analyses and independent gradient model based on Hirshfeld partition (IGMH) analysis were applied. It was found that the van der Waals (vdW) force is another main driving force, working in conjunction with hydrogen bonds to form basic units of AG co-crystals. In addition, toxicity tests on liver and kidney organoids showed that three new co-crystals did not cause more serious toxicity than pure AG. Overall, this work has provided the structural analysis of three newly formed AG co-crystals, offering an insight into intermolecular interactions of co-crystals at the molecular level.

Quantum chemical calculations compare the ability of σ and π-holes on the same atom to engage in a noncovalent bond. The first series of Lewis acids are the hypervalent XR₃ series where X refers to a central halogen atom. These molecules adopt a T-shape with a π-hole above the molecular plane and a σ-hole along the extension of the vertical of the T. A similar T-shape is characteristic of the AeX₂Y series where Ae is an aerogen/noble gas atom and Y is a chalcogen O or S. In all of these cases the σ-hole is deeper and forms a stronger bond with a NH₃ base. Also studied is a set of MX₂ and MX₃ units where M refers to a transition metal atom. Despite a variety of molecular shapes, encompassing planar trigonal, T-shape, bent, and linear, there is only one sort of hole present on each M atom, either σ or π. Other sorts of molecules also contain only a π-hole although the shape allows the possibility in principle of a σ-hole as well.

Two-dimensional (2D) materials have recently gained increased attention owing to their potential applications in catalysis and as luminescent materials in optoelectronics. Herein, we report the synthesis of two distinct blue- and white-light emitting crystalline 2D-metal organic frameworks (MOFs) using cis-5-norbornene-endo-2,3-dicarboxylic acid (NDA) as a ligand with Pb(NO₃)₂ [Pb(NDA)] (1) and Zn(OAc)₂·2H₂O [Zn(NDA)] (2), respectively. Compound 1 forms hepta-coordinated Pb(II) geometry with greater distortion, resulting in a 2D MOF with a (4,4) network topology. In contrast, in 2, Zn(II) centers are linked through NDA ligands to furnish a 2D MOF. The final structural characteristics of the synthesized compounds were significantly impacted by the carboxylic acid ligand. Upon excitation at 365 nm, compound 2 displayed blue-light emission, while compound 1 demonstrated near-white-light emission of solid-state photoluminescence (PL). The differing emissions of the two 2D sheets were associated with the bridging NDA ligand and the relative structural differences between the 2D structures. The shortest non-bonded metal-to-metal distance is lower in 1 than that in 2. Compound 1 exhibits a higher packing efficiency of bridging-metal centered clusters of layers; such packing is less pronounced in compound 2 because of the differences in coordination geometries. These differences profoundly affect the luminescent characteristics of 1 and 2.