Single Crystal Structure Research Articles

Orbital coupling of Pt single crystal via decoration of hetero-diatomic nickel-cobalt for efficient hydrogen evolution

Loading active metals in forms of single atoms or nanocluster is considered as an effective approach for designing catalysts with high atomic utilization efficiency. However, synthesis single atoms or clusters precisely in large quantities is a challenge. In this work, the isolated diatomic sites (Ni, Co) decorated single crystal Pt cluster were synthesized as efficient catalyst for hydrogen evolution. Adjacent Ni and Co atoms optimize the electronic structure of Pt single crystal, effectively lowering the water dissociation barrier and ensuring optimal binding strength of intermediates throughout the reaction process. As results, the mass activity of 2.087 A mg−1 was achieved under 200 mA cm−2, approximately 3 times than that of Pt/C. Theoretical calculations reveal that diatomic Ni, Co decorated Pt cluster reduces the energy barrier for breaking the OH-H bond, as well as facilitating the preferential adsorption and dissociation of H*. This work provides an opportunity for regulation electronic structure of catalytic via decoration single crystal cluster with diatomic sites and provides guidance for designing high efficiency electrocatalysts for promising applications.

Modularly Precise Construction of B,N-Embedded Large-Sized Polycyclic Aromatic Hydrocarbon Nanographene.

A modular "fjord-stitching" reverse strategy has been disclosed to successfully prepare two large-sized B,N-embedded nanographenes: BN-TBTi and BN-TBTo. These two compounds both exhibit excellent stability, nonzero-bandgap and decent photoluminescence quantum yield. Single crystal structure of BN-TBTo features a large C78B2N4 π-skeleton with length and width of approximately 2.4 and 1.5 nm, respectively.

Synthesis of base-modified fluorescent furo[3,2-c]coumarin nucleosides and their photophysical studies

A small library of fluorescent furo[3,2-c]coumarin nucleoside analogues has been successfully synthesized via a one-pot condensation reaction of 3′,5′-di-O-acetyl-5-formyl-2′-deoxyuridine, alkyl isocyanides, and differently substituted 4-hydroxycoumarins in acetonitrile at 80 °C. Further, the synthesized compounds have been characterized by IR, 1H NMR, 13C NMR, 1H–1H COSY, 1H–13C HETCOR, 2D NOESY NMR experiments, HRMS measurements and single crystal X-ray structure analysis of compound 5-(2′'-N-(cyclohexyl)-amino-4′'H-furo[3,2-c]chromen-4-one-3′'-yl)-2′-deoxyuridine. The electronic structure of these modified nucleosides has been examined by Density Functional Theory (DFT). The synthesized nucleoside analogues exhibited a prominent emission spectrum, featuring a band around 500 nm (with excitation at 380 nm). Photophysical investigations revealed a noteworthy fluorescence intensity, along with excellent Stokes shift values (54–194 nm) and higher quantum yields (0.010–0.515) in comparison to other pyrimidine-based fluorescent nucleosides. The solvatochromic studies of 5-(2′'-N-(cyclohexyl)-amino-8′'‑chloro-4′'H-furo[3,2-c]chromen-4-one-3′'-yl)-2′-deoxyuridine determined the quantum yield (ΦF) to be 0.515 in DMSO (λabs = 388 nm). This emphasizes the potential utility of these modified nucleosides in probing the local structure and dynamics of nucleic acids. Moreover, the scalability of the synthesis protocol was effectively demonstrated by producing one of the compounds on a gram scale, exhibiting its practical viability for large-scale production.

Temperature-induced structure evolution in monocrystalline and polycrystalline cobalt via molecular dynamics simulations

The structure transition of metallic melt strongly depends on temperature and significantly influences the comprehensive properties. However, observing the structure change in experiments is still challenging. Here, molecular dynamics is used to study the melting process and microstructural evolution in single crystal and polycrystal cobalt (Co). The results indicate that the melting process of single crystal structure starts from 1870 K and lasts for a very short period, while the polycrystal melts from about 1760 to 1870 K. In polycrystal Co, the melting initially occurs in grain boundaries, and the melting temperature shows a positive correlation with grain size. An interesting solidification phenomenon occurs on the surface of big grains in the beginning of melting process. The coordination number increasing from 12 to about 13.4 near melting point proves the local expansion of the first coordination shell, indicating the structural evolution from long-range order to short-range order in the continuous heating process. The common neighbor sub-cluster index and Voronoi polyhedron demonstrate the short-range icosahedron structures, while these polyhedrons become polydisperse and isolated in Co liquid. The findings ignite the investigation of the liquid structure origin of crystal materials and extend the understanding of the atomic structure evolution in melting.

Dual-response signal under mechanical stimulation: Alkyl substituent effect on the fine-tuning of molecular packing

Mechanical stimulus-responsive materials are generally considered to be closely related to molecular packing in the solid state, underscoring the significance of regulating molecular packing via precise molecular design. In this study, flexible alkyl substituents were employed to adjust the molecular packing. By modifying alkyl substituents, predictable changes in the molecular packing of their derivatives were observed, resulting in adjustable ML properties. The DPA-PYZ-TB with a tert-butyl-side chain exhibited strong ML and MC stimulus response signals. The enhanced ML and MC performance can be attributed to the effective suppression of non-radiation through the helical crystal arrangement and strong intermolecular interactions. The relationship between molecular arrangement and ML/MC properties was validated through analysis of the single crystal structure and corresponding experimental results. This study offers valuable insights into the enigmatic ML process and the development of efficient luminous materials that utilize both MC and ML.

Crystal structure and biological activity studies of two different types of herbicide safeners

Two heterocyclic compounds, imidazolidine-1,3-diylbis((5-methyl-3-phenylisoxazol-4-yl)methanone) (I) and (5-methylisoxazol-3-yl)(1-oxa-4-azaspiro[4.5]decan-4-yl)methanone (II), were characterized by X-rays. Compound I was crystallized in monoclinic system, space group Cc, a= 9.81000(12) Å, b= 15.21199(16) Å, c= 14.25369(17) Å, β= 90.3862 (12)degree, Z= 4, V= 2127.02(4) Å3, F(000) = 928.0, Dc= 1.382 Mg/m3, crystal size: 0.150 x 0.130 x 0.120 mm. Compound II was crystallized in the monoclinic system, space group P21/n, a = 5.6113(5) Å, b = 11.2280(10) Å, c = 20.675(2) Å, β = 95.543(10)degree, Z = 4, V = 1296.5(2) Å3, F(000) = 536.0, Dc = 1.282 Mg/m3, crystal size: 0.130 x 0.120 X 0.110 mm. Bioactivity assays showed that both compounds have good safety activity against nicosulfuron injury to corn, comparable to the commercial safener isoxadifen-ethyl. The molecular docking model indicated that two types of herbicide safeners competed with nicosulfuron for the acetolactate synthase active site and that this is the protective mechanism of safeners.. KEYWORDS :1,3-Disubstituted imidazolidine, Aryl-substituted formyloxazolidines, Single-crystal structure, Herbicide safener activity.

Potential building blocks for porous organic materials

2,4-Difluoronitrobenzene has been reacted with a linker diamine (ethylenediamine or propylenediamine) and butylamine, in either order, to give new molecular building blocks for porous supramolecular networks. Two structures were established by X-ray single crystal structure determinations. The propylenediamine structure displays small pores, which may be due to the longer and more flexible linker in the structure.

Local aromatic ring cleaves the global aromatic ring in hexaphyrin(2.1.2.1.2.1)

Novel benzo-bridged hexaphyrin(2.1.2.1.2.1) and its copper complex were synthesized. Single-crystal structures showed typical figure-of-eight Hückel topologies. NMR, NICS, HOMA, ACID, and EDDB analysis supported their non-aromatic properties owning to the strong local aromatic benzo rings cutting the global aromatic ring of the benzo-bridged figure-of-eight hexaphyrin(2.1.2.1.2.1). The redox properties and degenerate HOMOs and LUMOs levels indicate multielectron donating and accepting abilities.

A new three-dimensional luminescent MOF for the detection of Fe3+, CrO42−, and Cr2O72− in aqueous solution

A new luminescent MOF were synthesized by solvothermal method based on 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethene (TPPE), with the molecular structure of [Zn2(TPPE)0.5(ndc)2]n (ndc = 1,4-Naphthalenedicarboxylic acid) (LMOF-1). The single crystal structure indicates that LMOF-1 stacks in a three-dimensional structure. The fluorescence test results indicate that LMOF-1 emits blue light with quantum yield at 37.93 %, due to ligand–ligand charge transfer. PXRD and TG analysis confirmed that LMOF-1 has good stability, and PXRD analysis after different solvent exchanges confirmed that LMOF-1 has good stability in water. The results of ion titration experiments show that Fe3+, CrO42−, and Cr2O72− have significant quenching effects on LMOF-1, and the detection limits are 3.83 × 10−6 M, 2.57 × 10−5 M, and 4.33 × 10−6 M, respectively. Indicating that LMOF-1 can serve as a multifunctional ion detector.

An unexpected degradation pathway of N-hydroxy-5-methylfuran-2-sulfonamide (BMS-986231), a pH sensitive prodrug of HNO, in a prototype formulation solution

N-hydroxy-5-methylfuran-2-sulfonamide (BMS-986231, Cimlanod) was being developed as a pH-sensitive prodrug of HNO (nitroxyl) for the treatment of acute decompensated heart failure. During a stressed study of Cimlanod in a prototype formulation solution (pH 4.5) at 40°C, a predominant unknown degradant along with three previously identified degradants were observed. The unknown degradant was isolated from the stressed solution via preparative HPLC but totally decomposed during freeze-drying. LC-HRMS analysis of the isolated unknown degradant, prior to freeze-drying, revealed an empirical formula equivalent to the adduct of Cimlanod with SO2 even though SO2 was not added in the prototype formulation solution. The unknown degradant was synthesized from Cimlanod and DABSO ((1,4-diazabiscyclo[2,2,2]octane bis(sulfur dioxide) adduct) and isolated as a crystalline DABCO (1,4-diazabiscyclo[2,2,2]octane) salt for single crystal X-ray structure elucidation. The degradation of Cimlanod increased when the solution was exposed to air, as compared to N2 atmosphere. A plausible mechanism was postulated for the unexpected degradation pathway of Cimlanod. This study provided in-depth stability knowledge of Cimlanod, which will be beneficial to the subsequent stability indicating method development and validation as well as the registrational applications on the content and qualification of impurities in new drug products.

Low-Frequency Vibrational Spectra of 4-Fluorophenol Studied by THz Spectroscopy and Solid-State Density Functional Theory.

Hydrogen bonds serve as important intermolecular interactions organizing the spatial arrangement of molecular crystals. Determining the hydrogen-bond orientations remains a challenging task. In the previous XRD study, the authors assumed a single crystal structure of 4-fluorophenol in which molecules form hexamer-ring clusters via anticlockwise hydrogen bonding. However, the existence of the other structure, which adopts clockwise hydrogen bonding, remains uncertain and warrants further exploration. We unveil distinctive fingerprint information associated with both structures by using high-resolution terahertz spectroscopy. The distinct structures result in different intramolecular geometries of 4-fluorophenol regarding the O-H bond configurations, which are manifested by a noticeable peak splitting in the 20-200 cm-1 frequency range. This result illustrates the sensitivity of THz spectroscopy to hydrogen-bond conformational polymorphism. Our findings represent a significant advancement in utilizing high-resolution THz spectroscopy to resolve hydrogen-bond orientations in molecular crystals with possible broad applicability across diverse hydrogen-bonded organic and inorganic framework materials.

Design and synthesis of two new thiosemicarbazide based Schiff base metal complexes of nickel (II): DNA binding study and cytotoxicity profile analysis

Two new nickel (II) substituted thiosemicarbazone Schiff base complexes [Ni(meph)2] (1) [where H2meph = (2E)-N-methyl-2-[1-(pyridin-2-yl)ethylidene]hydrazine-1-carbothioamide] and [Ni(hmm)2](NO3)2·2H2O (2) [where H2hmm = (2E)-2-[(2-hydroxyphenyl)methylidene]-N-methylhydrazine-1-carbothioamide] have been designed and synthesized by the condensation of 4-methyl-3-thiosemicarbazide with 2-acetylpyridine and salicylaldehyde respectively. Both the metal complexes 1 and 2 are characterized using different available spectroscopic techniques like FT-IR, UV–Vis spectroscopy, elemental analysis, and single crystal X-ray structure analysis. X-ray crystal structure analysis reveal that complex 1 and 2 are octahedral Ni(II) complexes. The calf-thymus CT-DNA-binding property of 1 and 2 has been evaluated by employing UV–Vis and fluorescence spectral titration. All the results show that CT-DNA binds with both nickel(II) complexes 1 and 2. In vitro cytotoxicity activity of complexes 1 and 2 toward A375 and MDA-MB-231 was evaluated using MTT assay and other methods which confirm that both complexes 1 and 2 behave as promising anti-cancer agents.

A Comparative Study of a High-Pressure Polymorph of I2O5 and its Ambient-Pressure Modification.

A hitherto unknown modification of I2O5 was obtained from high-pressure/high-temperature syntheses in a Walker-type multianvil device at 8 GPa and 250 °C. HP-I2O5 crystallizes in the monoclinic crystal system in the space group P21/c (no. 14) with the unit cell parameters a = 12.0612(3) Å, b = 4.8613(2) Å, c = 6.9585(2) Å, β = 100.10(1)° (at 173 K), and four formula units per cell. The single-crystal structure data are accompanied by powder X-ray diffraction data at ambient and elevated temperatures. Furthermore, DFT calculations were carried out to investigate the phase transition between the ambient-pressure polymorph NP-I2O5 to the newly synthesized high-pressure phase.

Experimental and theoretical studies of pyrazole-4-carbaldehyde derivatives by X-ray crystallography, DFT, molecular docking, and molecular dynamics simulation

Nitrogen-containing heterocycles play a crucial role in drug design and discovery. Pyrazole derivatives have garnered attention due to their unique and intriguing features. This study investigates the structure and properties of two pyrazole-4-carbaldehyde derivatives (3 and 4). We report the single crystal structure of one of the intermediate compounds, 1-(1-(4-bromophenyl)ethylidene)-2-(2-chlorophenyl)hydrazine (2), and a final compound, 1-(2-chlorophenyl)-3-phenyl-1H-pyrazole-4-carbaldehyde (3). We analysed the non-covalent interactions within the crystal using Hirshfeld surface analysis and 2D fingerprint plots. We also used density functional theory (DFT) at the B3LYP/6–311G(d,p) level to optimise the structures and understand electronic properties, transitions and vibrational frequencies. To predict the anti-inflammatory potentials and selectivity of 3 and 4, molecular docking and molecular dynamics (MD) simulation studies against COX1 (PDB ID: 1EQG) and COX2 (PDB ID: 1CX2) receptors were conducted. Overall, this study sheds light on the structural, chemical, and biochemical features of two pyrazole-4-carbaldehyde derivatives.

Improvement of Single-Crystal Structures of Very Heavy Element Compounds by Refining Anomalous Dispersion Parameters.

Refining the anomalous dispersion parameters of the four uranium compounds NaUF5, NaU2F9, Cs2(UO2)TiO4, and Cs2(UO2)Ti2O6 gave insights into the crystallographic model improvement of very heavy atoms. We found that the values for the dispersive and absorptive parts, f' and f″, closely followed the X-ray absorption spectra on their L3, L2, and L1 edges. The obtained values are sensitive to the chemical environment at each crystallographically independent position. An incorrect treatment of the anomalous dispersion correction can lead to a wrong crystallographic model. The above-mentioned, already published structures were improved by this process. General guidelines were given for the crystal structure determination of very heavy compounds. When using Mo Kα radiation with uranium compounds, the proximity of its energy to the uranium L-edges causes a noticeable effect.

Unveiling the Stability Mechanism of Oriented Ni-Rich Layered Oxides.

Single-crystal and polycrystalline structures are the two main structural forms of the Ni-rich layered cathode for lithium-ion batteries. The structural difference is closely related to the electrochemical performance and thermal stability, but its internal mechanism is unclear and is worthy of further exploration. In this study, both polycrystalline and single-crystal LiNi0.83Co0.12Mn0.05O2 cathodes were prepared by adjusting the calcination temperature and mechanical post-treatment, respectively. Systematic comparisons were made to assess the effects of different grain structures on the electrochemical performance and thermal stability. The study revealed the superior thermal stability of monocrystalline cathodes, attributing it to oxygen vacancies and phase transitions. From the perspective of grain boundaries, it was demonstrated that the diffusion of oxygen vacancies and the reduction of Ni in polycrystalline cathodes exhibit anisotropy. This research elucidates the origins of the superior thermal stability of monocrystalline cathodes in lithium-ion batteries, providing valuable insights into battery material design.

Synthesis, the Reversible Isostructural Phase Transition, and the Dielectric Properties of a Functional Material Based on an Aminobenzimidazole-Iron Thiocyanate Complex.

By introducing disordered molecules into a crystal structure, the motion of the disordered molecules easily induces the formation of multidimensional frameworks in functional crystal materials, allowing for structural phase transitions and the realization of various dielectric properties within a certain temperature range. Here, we prepared a novel ionic complex [C7H8N3]3[Fe(NCS)6]·H2O (1) between 2-aminobenzimidazole and ferric isothiocyanate from ferric chloride hexahydrate, ammonium thiocyanate, and 2-aminobenzimidazole using the evaporation of the solvent method. The main components, the single-crystal structure, and the thermal and dielectric properties of the complex were characterized using infrared spectroscopy, elemental analysis, single-crystal X-ray diffraction, powder XRD, thermogravimetric analysis, differential scanning calorimetry, variable-temperature and variable-frequency dielectric constant tests, etc. The analysis results indicated that compound 1 belongs to the P21/n space group. Within the crystal structure, the [Fe(NCS)6]3- anion formed a two-dimensional hydrogen-bonded network with the organic cation through S···S interactions and hydrogen bonding. The disorder-order motion of the anions and cations within the crystal and the deformation of the crystal frameworks lead to a significant reversible isostructural phase transition and multiaxial dielectric anomalies of compound 1 at approximately 240 K.

Synthesis, structure, characterization and one pot catalytic activity of half-sandwich iridium(III) complexes

A series of stable mononuclear half-sandwich iridium(III) complexes of the general formula [(η5-C5Me5)Ir(L)Cl](BPh4) has been synthesized in dry methanol using different imino pyridine ligands (L1–L6) and [(η5-C5Me5)2Ir2(µ-Cl)2Cl2] in a 2:1 molar ratio. All complexes were fully characterized by melting point, CHN analysis, FT-IR, UV–visible, 1H NMR, 13C NMR spectroscopy and mass spectrometry. The structure of complex 3 [(η5-C5Me5)Ir(L3)Cl](BPh4) was determined by single crystal X-ray structure analysis, showing a chelating coordination mode of the imino pyridine L3. One pot organic transformations of aldehyde to amide were carried out by complexes 1–6 in toluene at 110 °C in the presence of hydroxyl amine hydrochloride and sodium bicarbonate. The catalytic activity of complex 3 was found to be excellent, showing high conversion with catalytic turnover frequency up to 500.

In-silico antibacterial activity of piperazinyl-based copper(II) metallo-organic pharmacophores

The piperazinyl-based Cu(II)-Schiff base complex {[Cu(HL1′)(N3)]2∙(ClO4)2·4H2O} (1) [HL1′ is the Zwitter ionic form of (E)-2-((2-piperazin-1-ylethylimino)methyl)phenol] was synthesized and characterized by spectroscopic and single crystal X-ray diffraction studies. The X-ray single crystal structure analysis shows that the asymmetric unit of 1 contains a four-coordinate discrete complex cation, [Cu(HL1′)(N3)]+ (1a), with a perchlorate anion and a lattice water molecule. Two square planar units of 1a are dimerized by weak Cu···N intermolecular interaction, forming [Cu(HL1′)(N3)]2 2+ (1′a). DFT and TD-DFT calculations of the monomeric cationic unit, [Cu(HL1′)(N3)]+ (1a) were performed. In-silico antibacterial activities of HL1 as well as monomeric and dimeric cationic units 1a and 1'a, respectively, were performed and study shows that 1a (EC50 0.30 μM) and 1′a (EC50 0.06 μM) may be treated as antibacterial drugs after in-vivo analysis and clinical testing.

Deciphering the cytotoxic and antioxidant potential of 3,5-disubstituted isoxazole-linked benzimidazolone derivatives

A series of new isoxazole derivatives containing a benzimidazolone has been synthesized by cycloaddition reaction using various nitrile oxides. In all cases, these cycloadditions are completely chemo and regioselective. The structures of the new cycloadducts were characterized by 1H, 13C NMR spectroscopy, HRMS and confirmed in one case by a single crystal structure determination. The isoxazole compounds were evaluated for in vitro antioxidant activity using the DPPH and ABTS methods. As a result, compound 5a showed good antioxidant activity. The results of the acute toxicity study of the heterocycles studied by the oral route showed no deaths and no clinical signs of toxicity. Additionally, the Hirshfeld surface analysis and the molecular electrostatic potential using density functional theory (DFT) modeling at the B3LYP/6–31G(d,p) level. Hirshfeld surface analysis (dnorm surface and 2D-fingerprint plots) revealed the nature of intermolecular contacts. H⋯H interactions make the most significant contribution to crystal packing. The optimized structural parameters obtained through DFT calculations closely matched those determined via X-ray analysis, demonstrating strong agreement between theoretical predictions and experimental observations.