Structural Chemistry最新文献

Herein, we report the preparation and characterization of four new ionic complexes with the ligand 2-aminomethylbenzimidazole (L), namely [Ni(L)₃](ClO₃)₂∙H₂O∙0.7MeOH (1), [Ni(L)₃](ClO₄)₂∙1.5H₂O (2), [Ni(L)₃](NO₃)₂ (3), [Ni(L)₃](SO₃NH₂)₂∙H₂O (4). The structures were refined with Hirshfeld Atom Refinement (HAR), and various Hirshfeld surfaces were analysed. In all cases, three molecules of L are coordinated to the central atom in a bidentate-chelating manner, and every nickel atom adopts a pseudo-octahedral coordination geometry. The most significant contacts typically involve hydrogen bonds between the hydrogen atom of the imidazole ring and the inorganic anion or water molecules.

A dimethyl[(1H-1,2,4-triazol-1-yl) methyl]amine was synthesized for the first time without catalyst with a high yield and selectivity. Its structure was elucidated spectroscopically in the liquid state and with X-ray single-crystal analysis in the solid state. A distinctive feature of this compound is that C(sp²)–N bonds in 1,2,4-triazole unit are shorter than conventional C(sp²)–N one, which is probably due to stereoelectronic interactions. NBO and AIM approaches showed that there are interactions between lone pair of nitrogen atoms and π-antibonding orbitals of neighboring C = N bonds. This finding can be used to explain and to predict the chelation ability of 1,2,4-triazole derivatives to form complexes (for example, with metal ions). The Hirshfeld method made it possible to find that H…H, H…N/N…H, and H…O/O…H contacts play an important role to form the supramolecular assembly of the 1,2,4-triazole derivative in its single-crystal.

In this theoretical study, we systematically designed and analyzed a series of anthracene-based donor–π–acceptor (D-π-A) sensitizers for dye-sensitized solar cells (DSSCs) using Density Functional Theory (DFT). Four dyes (Mn-1 to Mn-4) featured diverse substituents on the acceptor moiety, including carboxylic acid, chloro, and nitro groups. The structural, electronic, and optical properties of the sensitizers were investigated to elucidate their intramolecular charge transfer (ICT) efficiencies and impacts on photovoltaic performance. Computational analyses revealed that Mn-2 and Mn-4, which feature carboxylic acid and nitro groups, respectively, exhibited superior electronic properties, including optimal HOMO–LUMO energy alignment, reduced energy band gaps, and enhanced charge transfer characteristics. Mn-2 has emerged as the best candidate, demonstrating efficient electron injections and minimized recombination losses, supported by its favorable light-harvesting efficiency and open circuit voltage. These findings highlight the importance of molecular engineering in optimizing the sensitizer performance of high-efficiency DSSCs. This study provides valuable theoretical insights into the design of next-generation photovoltaic devices.

In this study, we report the solvent-controlled synthesis of two novel Cd-MOFs using 4,4′-(hydroxyphosphoryl) dibenzoic acid (H₂hpda) as a multifunctional phosphorus-containing ligand. By modulating the solvent polarity—using either DMF or DMA/H₂O mixtures—we successfully obtained two distinct architectures: a 2D layered structure (CJLU-L4) and a 3D porous framework (CJLU-L5).Single-crystal X-ray diffraction analysis revealed that CJLU-L4 adopts a 2D layered structure with a porosity of 37.6%, whereas CJLU-L5 exhibits a 3D network structure with a significantly higher porosity of 57.7%. The phase purity of both cadmium-based MOFs was confirmed by powder X-ray diffraction (PXRD) and infraredspectroscopy (IR). Photoluminescence studies showed that the PL intensity of CJLU-L5 was lower, indicating that the framework dimension has an important influence on adjusting the optoelectronic properties of MOF.

The combined method of genetic algorithm and density functional theory (GA-DFT) has been used to study the size evolution and property of PdAg_n (n = 1–17) clusters. Benchmark calculations reveal that the TPSSH/def2-TZVP method is suitable. The structures of the clusters are planar or quasi-planar when n = 1–4, whereas they are three-dimensional when n = 5–17. The Pd atom favors to locate at the position with the highest coordination number. Moreover, the Pd atom likes to locate at the central position for PdAg_n clusters. Average bond lengths of Pd–Ag and Ag–Ag of PdAg_n (n = 1–17) clusters are recorded, which reveals that r_Ag-Ag and r_Pd-Ag increases as cluster size. The charge of Pd atom increases as cluster size. The average bond orders of Pd–Ag and Ag–Ag bonds decrease as cluster size increases. The peaks of the ultraviolet–visible spectra of the clusters increase as cluster size, and the peaks present odd–even oscillations as cluster size. The stability of PdAg_n clusters displays odd–even oscillation based on harness analysis and second-order energy difference analysis. According to thermodynamic analysis, the formation reactions of PdAg_n are spontaneous when the Ag atom adds to PdAg_n-1 clusters.

2-((1-Phenyl-1H-1,2,3-triazol-4-yl)methoxy)benzonitrile (3), was synthesized by scaffold Schiff base condensation reaction of 1,2,3-triazole (1) and then followed by its dehydration. The title compound was characterized by typical spectroscopic techniques such as ¹H-NMR, ¹³C-NMR and FTIR. The structure of the title compound 3 was also determined by single crystal X-ray diffraction analysis. The compound co-crystallizes with water molecules, which occupy a twofold axis special position, in the orthorhombic system with space group Pnna and a = 13.606(3) Å, b = 23.442(5) Å, c = 8.2412(16) Å. The crystal structure is stabilized by strong hydrogen bonds between the water molecules and the compound, along with weaker secondary interactions, including π-π stacking and C-H···N interactions. The geometry of 3 was optimized by the DFT method and the results were compared with the single crystal X-ray diffraction data. Frontier molecular orbitals of the title compound 3 were calculated by using the B3LYP/6–31 + g(d,p) method. MEP analysis and Mulliken charge density, Global reactivity and thermodynamic properties were also performed.

A new coumarin-derived compound, featuring a 1,2-pyrazole ring with a morpholine substitution, was synthesized from N(4)-pyrrolidine thiosemicarbazide and 4-hydroxy-2-oxo-2H-1-benzopyran-3-carboxaldehyde in ethanol by using glacial acetic acid as a catalyst. Single crystal XRD analysis revealed the crystalline structure of the compound, identifying it as triclinic with a space group of P-1, with unit cell dimensions a = 7.6945(2) Å, b = 7.9693(2) Å, c = 12.2466(3) Å, and α = 108.6230(10)°, β = 93.3450(10)°, ϒ = 97.8130(10)°. The compound exhibited a rare cyclisation at very normal reaction conditions and that was quite unexpected. To the best of our knowledge, this is an uncommon cyclisation (formation of a pyrazole ring) rather than a coumarin-based thiosemicarbazone and the first one containing morpholine.

The current work reports the facile synthesis and characterization of half-sandwich compounds [Ti(η⁵-C₉H₇)(Cl)₂(OR)] (3) (R = ⁱPr (3a); R = ^tBu (3b); R = 2,6-Ph₂C₆H₃ (3c); CH₂CH₂(^CC₄H₃S) (3d) (prepared via treatment of Ti(η⁵-C₉H₇)Cl₃ (1) with LiOR (2a, R = ⁱC₃H₇; 2b, R = ^tC₄H₉; 2c, R = 2,6-Ph₂C₆H₃; 2d, R = CH₂CH₂(^CC₄H₃S)) in a 1:1 molar ratio. Additionally, compounds 3a, 3b, and 3d were also obtained when compound 1 was reacted with HOR (2a, R = ⁱC₃H₇; 2b, R = ^tC₄H₉; 2d, R = CH₂CH₂(^CC₄H₃S)) under reflux in benzene. The half-sandwich titanium compounds 3a–d were characterized by elemental analyses, FT-IR, and ¹H and ¹³C{¹H}-NMR spectroscopy. Density functional theory (DFT) calculations at the B3LYP/6-31G(d) + LANL2DZ level of theory were carried out for 1 and 3a–d in order to better understand and rationalize the nature of bonding and thus demonstrate the effect of different substituents on the structural and electronic properties. The studies confirm a similar complexation pattern despite the different chemical nature of the substituents. However, the HOMO–LUMO frontier molecular orbitals analysis revealed ligand–metal charge transfer, and the calculations predicted smaller HOMO–LUMO energy gaps for 3c.

We investigate the glycolysis of poly(ethylene terephthalate) or PET catalyzed by cyanamide using density functional theory. A PET dimer with C−O linkages is modeled as a representative active region. The reaction can proceed via two mechanisms based on the role of cyanamide: one involves forming a hydrogen bond with the PET dimer, while the other facilitates hydrogen transfer to promote C–O bond cleavage and O–H bond dissociation in ethylene glycol. Cyanamide stabilizes all species in the glycolysis reaction pathways by reducing their relative energies compared to the bare system. The intrinsic activation barriers for both mechanisms in the cyanamide-catalyzed system are found to be 40.6 and 36.3 kcal/mol, respectively, both lower than the barrier observed in the bare system (42.0 kcal/mol). We further investigate a mechanism in which cyanamide plays a dual role, simultaneously facilitating hydrogen transfer and forming hydrogen bonds with the dimer. The activation barrier is significantly reduced to 33.6 kcal/mol compared to the single cyanamide-catalyzed systems. Hence, we suggest that cyanamide serves a dual function, promoting both hydrogen transfer for C–O bond cleavage and hydrogen bond formation with the dimer. Moreover, the electron-donating substitution on the amino group of cyanamide further enhances catalytic activity by reducing the energy barrier compared to the unsubstituted form. Finally, in the presence of a water molecule, the barrier for the dual-role mechanism is reduced to 24.8 kcal/mol. Therefore, explicit water enhances the catalytic activity of cyanamide for PET glycolysis by acting as a medium to facilitate hydrogen transfer.

Contemporary quantum chemistry methods are the legacy of pioneers like John A. Pople, a Nobel Prize winner in 1998. Using such methods, we investigate the open-cage hydrocarbon derived from cubane upon removal of one of its CH moieties located at the vertex of the carbon skeleton. This hydrocarbon has C_3v symmetry and, following a geometric analogy, is termed vertexane (VA). The halogen derivatives of VA, obtained by replacing the apical hydrogen atom with a halogen, and their organotin congeners with a tin-halogen bond are polar molecules which represent novel building blocks in the design of tomorrow’s materials. The covalently-bonded dimers of VA are also explored, one is dumbbell-shaped while the other is a caged hydrocarbon of intermediate composition between those of cubane and dodecahedrane.