Structural Chemistry最新文献

This study investigates the molecular changes in triphenylguanidine and triphenylguanidinium trifluoroacetate as temperature decreases, utilizing variable-temperature single-crystal X-ray diffractometry (VT-SCXRD). The Hansen-Coppens multipole formalism is employed for aspherical atom refinement, enabling the retrieval of solid-state polarizability and hyperpolarizability tensorial coefficients ((varvec{alpha }) and (varvec{beta })). Furthermore, the research examines the molecular basis for variations in the thermal expansivity of the crystalline solid forms, namely, in the polymorphic forms of triphenylguanidine. The aromaticity of the central core and the phenyl rings of triphenylguanidine is monitored as temperature changes, using the HOMA and NICS indices. The results indicate a clear increase in the aromaticity of the phenyl rings. Topological analysis of charge density is used to identify regions of high and low electron density. Evidence is provided for weak attractive interactions between the trifluoro groups of neighboring anions.

Structures of a family of new hydrated and anhydrous perrhenates of lead and strontium have been determined. Sr(ReO₄)₂·H₂O is isostructural to Ce(CrO₄)₂·H₂O and Th(CrO₄)₂·H₂O; Pb(ReO₄)₂·2H₂O is analogous to Sr(ReO₄)₂·2H₂O and Pb(TcO₄)₂·2H₂O. The compounds Sr(ReO₄)₂·6H₂O, Pb(ReO₄)Cl·2H₂O, and {Pb₄(OH)₄}(ReO₄)₄·H₂O correspond to new structural architectures. We discuss the similarities and differences in the crystal structures of relatively simple inorganic salts containing tetrahedral oxoanions based on d-elements (MnO₄⁻, TcO₄⁻, ReO₄⁻, CrO₄²⁻, and MoO₄²⁻); the analogies to tetrahedral p-based hydrido- or fluoroanions (BF₄⁻ and AlH₄⁻) exist but are as yet rare.

First principle calculation reveals that recently synthesized phosphine and chloride ligand substituted pentacoordinate Si species i.e., [SiCl₃(PMe₃)₂]⁺ not only behaves like an alkali but also exhibits cationic superalkali characteristics after suitable ligands substitution. A series of hypercoordinated Si based superalkali complexes have been designed based on phosphine and N-heterocylcic carbene (NHC) ligand. The electron donating group substituted phosphine and NHC ligand based pentacoordinate Si systems exibits very low ionization energy within the range of 3.5 to 4.5 eV. Frontier molecular orbitals (FMOs) analysis gives the idea about the variation of the ionization energy with HOMO energy. The significant first and second order hyperpolarizability values of these systems corresponds to high non-linear optical (NLO) properties. AdNDP and AIM analysis gives a clear idea about the covalent bonding nature of Si-P and Si-Cl bond in these systems.

Isoeugenol is a fragrance material and possesses extensive pharmacological activities. However, its application is restricted because of poor water solubility, low bioavailability, instability, irritation, and volatility. Although encapsulation of isoeugenol in the cavity of β-cyclodextrin (β-CD) is a way to solve these similar problems, the formation mechanism and the interaction of isoeugenol and β-CD remain unclear. In this work, isoeugenol was encapsulated in β-CD to produce isoeugenol-β-cyclodextrin (IE-β-CD) inclusion complex. The product was characterized by thermogravimetric analysis and Fourier transform infrared spectroscopy. Molecular simulation was used to investigate the interaction between isoeugenol and β-CD and to reveal the formation mechanism. The results showed that IE-β-CD was successfully prepared. The molar ratio of isoeugenol to β-CD in the product is about 1:1. The negative chemical potentials indicate that the formation process of IE-β-CD is spontaneous. Isoeugenol lasted long, and its stability was improved. The isoeugenol release reaction order, activation energy, and pre-exponential factor were obtained as 0.5, 121.4 kJ/mol, and 5.3 × 10¹¹, respectively. The structure of IE-β-CD was optimized. The binding energies were − 119.0 and − 114.2 kJ/mol for orientations A and B, respectively. The binding energy and energy gap indicate that IE-β-CD formed by orientation A is relatively more stable than that formed by orientation B. Deformation and charge-transfer interaction occurring in the complexation process were driving factors to form stable IE-β-CD. Isoeugenol donates electrons to β-CD and as a whole carries positive charges. The energy gaps indicate that IE-β-CD has a relatively high activity compared with the free isoeugenol and β-CD.

Using density functional theory (DFT) in combination with particle swarm optimization (PSO) algorithm, we have investigated the role of group III and 4d/5d series of transition metal dopants on the structure and electronic properties of the icosahedral anionic Al₁₃⁻ cluster. Our results reveal that doping significantly modifies the structural characteristics of the Al₁₃⁻ cluster leading to geometries with the dopant occupying both endohedral and apical sites. This geometric transformation leads to notable alterations in the electronic properties, as evident from the computed binding energy per atom, HOMO–LUMO gap, vertical detachment energy, and vertical electron affinity. The findings indicate that doping enhances the stability of the anionic Al₁₃⁻ cluster. BAl₁₂⁻ cluster and 4d- and 5d-doped Al₁₃⁻ clusters generally depict enhanced binding energy per atom as compared to pristine Al₁₃⁻ cluster. Oxygen adsorption studies show that O₂ binds strongly in both atop and bridged modes on all the clusters, except for NbAl₁₂⁻, RuAl₁₂⁻, and ReAl₁₂⁻ clusters, where oxygen binding occurs only in the bridged mode. Additionally, the closed-shell clusters doped with Tc, Ta, Rh, and Ir exhibited exceptionally low spin excitation energy (SPE) values of 0.01, 0.20, 0.26, and 0.37 eV, respectively, as compared to the pristine Al cluster which showed a significantly higher SPE of 1.27 eV. The low SPE values suggest that these doped clusters will be effective for O₂ binding and activation. These findings provide fundamental insights into the structure and reactivity of doped Al₁₃⁻ clusters.

Curcumin derivatives are bioactive compounds with a linear structure and an α,β-unsaturated β-diketone moiety. The chemical reaction of 3-hydroxy-4-methoxybenzaldehyde and cinnamaldehyde in DMF in the presence of acetylacetone and boric oxide mixture resulted in the synthesis of a curcumin derivative named as (1E,4Z,6E,8E)-5-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-9-phenylnona-1,4,6,8-tetraen-3-one (HPTO). The compound was characterized by FT-IR, MS, 1H-, and 13C-NMR. Moreover, crystal structure was determined by single crystal XRD analysis, which displayed the presence of a solvent molecule along with the main molecule (HPTO). The geometry of the main molecule was stabilized by intramolecular O–H···O bonding. The molecule adopted a non-planar conformation with a dihedral angle between phenyl rings of 35.1 (1)°. The supramolecular assembly was stabilized by numerous intermolecular interactions that were explored by Hirshfeld surface analysis. Interaction energy calculations were carried out at B3LYP/6-31 g(d,p) electron density level to support the experimental findings. Void analysis was performed in order to predict the response of the crystal to the applied stress. The compound was studied using the DFT method, employing the 6-311 g(d,p) basis set, to evaluate its electronic and quantum chemical properties. Frontier molecular orbitals and density of states analyses revealed an energy gap of 3.08 eV. This finding indicates the compound’s significant chemical reactivity and potential for notable biological activity. Molecular docking studies were performed to evaluate the compound’s potential as a cancer treatment medication candidate. By employing a multidisciplinary methodology, this research provides a thorough understanding of the compound’s structural features, chemical properties, and prospective pharmaceutical applications, paving the way for its development in cancer treatment.

Two-dimensional materials have the potential to be utilized as gas sensors, thereby facilitating the enhanced adsorption of toxic and hazardous gases. The adsorption properties of NO₂, N₂O, SO₂, and H₂S by WS₂ and Cu/WS₂ were investigated using first-principles calculations. In the doped system, the gases exhibit a tendency to adsorb above the Cu atoms, that is, above the S atoms that correspond to the intrinsic WS₂. The results demonstrate that during the adsorption process of Cu/WS₂, the gas molecules form chemical bonds with the Cu atom, thereby changing from physical adsorption to chemical adsorption. The doping of Cu atoms was observed to increase the adsorption energy, decrease the adsorption distance, increase the transferred charge, and decrease the band gap for the four gases. The dopant atoms facilitate the hybridization of the substrate with the orbitals of the gas molecules, resulting in a redistribution of charge within the adsorption system. This phenomenon is the underlying cause of the enhanced adsorption capacity observed in the doped system. The recovery times for Cu/WS₂-N₂O and Cu/WS₂-SO₂ are relatively short, which is suboptimal for a robust response to the detected signal. Compared with room temperature, the adsorption of NO₂ and H₂S by Cu/WS₂ can be effectively desorbed within a short time after heating. This study provides a theoretical basis for the design of WS₂-type high-performance gas sensing materials for NO₂ and H₂S.

A theoretical study of a set of unsubstituted and fluorinated small aromatic monocyclic and arene-type condensed molecules is presented. The quantum chemical calculations were performed at the density functional theory level. The fluorination effect on the Wibberg bond order and structural HOMA indices is discussed for monocyclic and bicyclic molecules with arene units. Changes in the electronic structure in the vicinity of the atoms forming the aromatic ring were analyzed using the sum of negative and positive partial atomic charges. The global electron-rich or electron-deficient character of investigated small molecules was also quantified using vertical ionization potentials and vertical electron affinities. For selected tricyclic and pentacyclic condensed molecules, the synergy of central ring modification and fluorination was investigated for the electrochemical and lowest energy optical band gaps. The geometric pattern of these compounds is either linear or angular, and it is based on possible combinations of benzene moieties with a six- or five-membered central aromatic ring. Theoretical results were compared with experimental data. The obtained data indicate that the fluorinated angular pentacyclic molecules with a central thiophene and pyridazine moiety are expected to be promising candidates for the construction of organic n-type semiconductors with respect to the setting of electronic structure as well as internal reorganization energies.

Ammonium perchlorate (AP) serves as an important component in solid propellants. Adding catalysts to facilitate its thermal decomposition can enhance the combustion performance of solid propellants. Inspiring by the remarkable thermal stability and resistance to mechanical stimuli of the 3-cyano-1,5-(5-nitro-1,2,4-triazolyl) formazan, four energetic metal salts with 3-cyano-1,5-(5-nitro-1,2,4-triazolyl) formazan as energy storage units were synthesized and well characterized. The molecular structures of the compounds 1–2 were confirmed by single-crystal X-ray diffraction. The thermal behaviors and sensitivities of these new four energetic metal salts were determined by the differential scanning calorimetry (DSC) and BAM methods. These new four energetic metal salts possess excellent thermal stability with decomposition peak temperatures over 259 °C and low impact and friction sensitivity (IS > 40 J, FS > 360 N). Additionally, the four energetic metal salts exhibited outstanding performance in accelerating the thermal decomposition of AP, the high-temperature peak decreased by 30 to 120 ℃, and the heat release increased significantly, which was 1.1 to 2.8 times of pure AP. The decomposition activation energy (({E}_{a})) of pure AP and AP with 10 wt% compounds 1–4 were calculated using the Kissinger equations, respectively. The AP decomposition activation energy decreased by 9.41 to 18.45 kJ·mol⁻¹. These experimental results indicate that the four energetic metal salts are expected to be the alternative additives to accelerate the catalytic decomposition of AP in composite solid propellants.