Structural Chemistry最新文献

Density functional theoretical calculations are used to investigate the nature of the metal–ligand bonding in the η³-propargyl complexes of Pt(II) and related species. Of particular interest are the interactions between the central propargyl C atom and the Pt centre. Experimental data has shown that the distance between Pt and the central C atom is the shortest Pt-C bond in the η³-propargyl complex [(η³-PhCCCH₂)Pt(PPh₃)₂]⁺, suggesting a strong bonding interaction. However, approximate molecular orbital calculations have suggested that bonding between Pt and the propargyl ligand occurs primarily through the terminal propargyl C atoms. In this contribution, Pt-C interactions are analysed using molecular orbital theory, natural bonding orbital analysis, and the quantum theory of atoms in molecules (QTAIM). Calculated bond orders and delocalization indices suggest that there is a significant bonding interaction between the Pt centre and central carbon atom, but that this interaction is much weaker than the short bond distance would suggest. Energy decomposition using the interacting quantum atoms (IQA) approach further supports this conclusion. A comparison is made to the bonding in related model metallacyclobutene and η³-allyl complexes.

Ephedrine is an ancient Chinese medicine drug used on patients with asthma, bronchitis and hay fever. In more recent times, it is used to prevent low blood pressure during anesthesia and to treat narcolepsy and obesity. It seemed important to understand the interaction of this drug with as large a variety of substrates as possible to get hints as to its modus operandi. It was, therefore, of interest that it appeared to crystallize as a Racemic Mimic in the form of its 4-nitrobenzoate derivative as determined by the cell parameters of that salt when it crystallized in both racemic and Sohncke space groups. Below, we describe the procedure used to prove that ephedrine belongs in that class and to illustrate the nature of the intra- and inter-molecular interactions between the constituent moieties in that monoclinic (P2₁ and P2₁/c) pair. Both crystal structures, obtained from the literature, were determined at 123 K and refined, respectively, to R-factors of 3.73 and 5.51%.

Peroxosolvates are commonly employed as solid-state sources for hydrogen peroxide in various scientific and industrial applications. However, among the hydrogen peroxide adducts, nitrate peroxosolvates remain poorly studied. This study reports the synthesis and characterization of two crystalline peroxosolvates of triethylenediamine (DABCO) derivatives: H₂DABCO dinitrate (C₆H₁₄N₂)(NO₃)₂·H₂O₂ (1) and DABCO N,N′-dioxide mononitrate (C₆H₁₃N₂O₂)(NO₃)·2H₂O₂ (2). The peroxosolvates were synthesized using 50 wt% aqueous hydrogen peroxide and characterized by permanganometry, CHN elemental analysis, powder X-ray diffraction, and differential thermal and thermogravimetric analyses. The crystal structure of peroxosolvates was determined by single-crystal X-ray diffraction analysis. Hydrogen peroxide acts only as a hydrogen bond donor to O atoms of nitrate anions and the N-O moiety. One of H₂O₂ hydrogen bonds in compound 1 is bifurcated, which is quite rare for peroxosolvates. The crystal structures of both compounds are stabilized by a rich network of hydrogen bonds.

In this research, optical and nonlinear optical (NLO) properties of benzocryptand doped with alkaline earth metals (Be, Mg, Ca) both exohedrally and endohedrally were studied using DFT. Nine combinations of doped metals BzC, i.e., A-BzC-A* (A, A* = Be, Mg, Ca), were analyzed. Excess electron doping effects on optical and electronic properties for NLO response were also explored. Frontier molecular orbitals (FMOs), density of states (DOS), absorption maxima (λ_max), and transition density matrix (TDM) analyses were conducted to investigate charge transfer phenomena. Parameters like dipole moment (μ), binding energy (E_b), interaction energy (E_int), electron affinity, excitation energy (ΔE), and natural bonding orbitals (NBO) were examined. Non-covalent interaction (NCI) and infrared (IR) analysis revealed weak interactions and vibrational frequencies. Enhanced λ_max (536-3200 nm) and reduced band gap (0.34-2.71 eV) were observed. Among all, the Ca-Ca*-doped BzC complex demonstrated the highest NLO response, with endohedral and exohedral Ca doping resulting in the most remarkable enhancement in hyperpolarizability, confirming the effectiveness of bimetallic positioning in enhancing NLO properties. Bimetallic doping notably improved linear polarizability (α_iso) and hyperpolarizability (β_tl), indicating potential for novel NLO materials. DFT and TD-DFT for all compounds’ quantum chemical simulations were conducted using Gaussian 09 with molecular geometries and orbitals visualized in Gauss View 6.0. Furthermore, physical and chemical parameters, including bond lengths, dihedral angles, dipole moments, and charge densities, were analyzed. All the newly designed complexes were optimized at the B3LYP/6-31G (d′, p′) level of theory.

In this work, the excited state intramolecular proton transfer (ESIPT) mechanism of BBS-OH (2-(Benzothiazol-2-yl)-5-bromophenol) and the influence of atomic electronegativity on the ESIPT behavior of BBS-OH molecules and its derivatives have been theoretically explored. By analyzing infrared vibrational spectra, bond lengths and bond angles, the hydrogen bond is strengthened in the S₁ state, as the atom electronegativity decreases, which is further confirmed by the density gradient function (RDG) isosurfaces and scatterplots. The decrease in electronegativity reduces the energy gap, leading to a slight redshift in both absorption and fluorescence spectra. Additionally, potential energy curves (PECs) analysis confirms the ESIPT process can be effectively modulated by tuning atomic electronegativity.

Two carbendazim (CBDZ) salts, (C₉H₁₀N₃O₂)₂SO₄·2H₂O (compound 1) and (C₉H₁₀N₃O₃)·NO₃ (compound 2), have been prepared and characterized using spectroscopic techniques. The crystal structures of both compounds have been solved by single-crystal X-ray diffraction. In both salts, the protonation of CBDZ occurs at the nitrogen atom of the imidazole ring. Hirshfeld surface analysis was conducted to evaluate the nature of the intermolecular interactions in each compound, revealing that O···H/H···O interactions are the dominant components of the resulting 2D fingerprint plots for both compounds. Molecular docking and molecular dynamic studies demonstrated that the protonated form of CBDZ (CBDZH) binds strongly to amino acid residues through hydrogen bonds, van der Waals interactions, and cation (anion)-π interactions, in contrast to neutral CBDZ. The binding affinity for CBDZH (− 29.03/ − 22.52) was found to be approximately three times higher than that of CBDZ (− 11.88/ − 7.19) according to the MMGBSA and MMPBSA methods. Total decomposition analysis indicates a higher contribution of van der Waals and electrostatic energies to the ligand–protein interaction energies with certain amino acid residues for both complexes.

A series of hydrazone derivatives of diazatricyclo[4.3.1.1³,⁸]undecane (3a–3d) were synthesized and characterized spectroscopically. DFT calculations at the B3LYP/6-311G(d,p) level showed that compound 3c had the smallest HOMO–LUMO gap (0.027 eV), indicating high electronic reactivity and suitability for optoelectronic applications, while 3d exhibited the largest gap (0.134 eV), suggesting high chemical stability. MEP and Mulliken analyses confirmed strong nucleophilic sites in 3a and 3c, with 3d displaying a balanced charge distribution. UV–Vis spectra revealed extended conjugation in 3c with absorption near 1100 nm. Thermodynamic analysis ranked 3b as the most stable and energy-efficient compound. These findings support the potential of these molecules in optical and electronic materials development.

The molecular structure and spectral characteristics (FT-IR and UV–Vis) of the new spiro compound, 3-(2-(2-hydroxyphenyl)hydrazono)-1,5-dioxaspiro[5.5]undecane-2,4-dione (HD), were computed using DFT/B3LYP/6-31G(d, p) and compared to experimental spectra. A single-crystal XRD study revealed that the HD molecule was linked by O5 − H5A··O1 intermolecular interactions. The band gap of HOMO–LUMO energy estimates ranged between − 5.936 and − 2.222 eV. The large gap energy (3.714 eV) of HD implied that the molecule had higher stability. MEP surface analysis gave its nucleophilic and electrophilic attack sites. Natural bond orbital (NBO) study revealed the kind and direction of charge transfer, as well as the stabilization energies of HD. Hirshfeld surface analysis was utilized to explain that H···H interaction makes up the majority (45.8%) in HD. Finally, the HD molecule was confirmed to be stable up to 154 ℃ using TG/DSC.

This study explores the potential of C₃N₂ nanosheets as a gas sensor for detecting harmful industrial gases like NH₃, NCl₃, NF₃, COCl₂, and SOCl₂ using DFT computations. The interaction and adsorption of these gases on the C₃N₂ surface were analyzed using methods such as frontier molecular orbitals (FMO), natural bond orbital (NBO), quantum theory of atoms in molecules (QTAIM), and electron density difference (EDD). The interaction energies ranged from − 17.37 to − 9.04 kcal/mole, with SOCl₂ showing the highest interaction energy. The charge transfer and (E_HOMO-E_LUMO) energy gaps were slightly reduced for NH₃ and COCl₂, suggesting effective sensing capability. The QTAIM analysis confirmed non-covalent interactions between the gases and the C₃N₂ surface. Overall, the results demonstrate that C₃N₂ nanosheet is more sensitive for detecting and trapping NH₃ and COCl₂.

The presence of chemical nerve agents (CNAs) poses significant threats to both living beings and the environment, making their rapid detection and elimination crucial. In this study, the potential of boron carbide (B₁₆C₁₆) nanocage (BCN) as an electrochemical sensor material for A-series chemical nerve agents (CNAs) was investigated using density functional theory (DFT). The adsorption studies reveal the chemisorption nature of interactions between CNAs and BCN, characterized by high negative adsorption energies for A230@SiteC (-95.136 kcal/mol), A232@SiteA (-31.792 kcal/mol), and A234@SiteB (-92.963 kcal/mol). FMO studies reveal that the energy gaps of 1.40 eV for A230@SiteC, 1.61 eV for A232@SiteC, and 1.46 eV for A234@SiteB decreased from 1.80 eV of pristine BCN. The Fermi level energy (E_FL) undergoes significant shifts in all systems, depending on the density of states (DOS). Topological analyses, including QTAIM and NCI, indicate that the interactions are predominantly of weak covalent or van der Waals nature. The adsorption of CNAs significantly enhances the electrical properties, with electrical conductivity (σ) increasing to 5.98 × 10¹² S/m (A-230@SiteC), 5.73 × 10¹² S/m (A-232@SiteC), and 5.92 × 10¹² S/m (A-234@SiteB). The decrease of work function ((phi)) and short recovery times (τ) in these configurations increases the sensing response (S) 0.0823 for A-230@SiteC, 0.0376 for A-232@SiteC, and 0.0705 for A-234@SiteB. These results highlight the efficiency of BCN as a robust sensor for CNAs, making it a promising candidate for future advancements in chemical sensing technologies.

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