Structural Chemistry最新文献

A new iron(III) sulfato complex [Fe₂(bpy)₂(H₂O)₂(µ-O)(µ-SO₄)₂]·3H₂O has been prepared from iron(II) chloride by using potassium peroxydisulfate being the oxidation agent and the source of sulfato ligands as well. The compound has been characterized by infrared, Raman and Mössbauer spectroscopies. X-ray structure analysis confirmed the presence of the Fe(III)–O–Fe(III) core in the complex. Both sulfato groups are bonded in the form of bridged bis(monodentate) ligands. The coordination polyhedra about the central atoms are completed by 2,2′-bipyridine and water molecules, forming thus distorted octahedra. A thorough comparison of bonding parameters of all dinuclear oxido-bridged sulfato complexes of iron(III) that have been solved by X-ray structure analysis revealed several strong correlations between these parameters and bonding mode of sulfato ligands. The characteristic vibrational bands of the FeOFe group has been observed at 770 cm⁻¹ (IR) for ν_as(FeOFe) and at 513 cm⁻¹ (IR) and 520 cm⁻¹ (Raman) for ν_s(FeOFe). The assignment of characteristic bands was corroborated by DFT calculation. The isomer shift values obtained in Mössbauer spectra indicate high-spin Fe³⁺, while the large quadrupole splitting is characteristic of oxygen bridged Fe³⁺ ions.

Dioxinodehydroeckol (DOO) is a natural phlorotannin with remarkable potential antioxidant activity. In this study, for the first time, the mechanism and kinetics of its radical scavenging activity specifically targeting hydroperoxyl radicals under physiological conditions (both aqueous and lipid environments) were elucidated. This compound was initially evaluated through its intrinsic thermochemical properties based on mechanisms such as formal hydrogen atom transfer (fHAT), sequential electron proton transfer (SETPT), and sequential proton loss electron transfer (SPLET). The kinetic calculations revealed that the reaction rates (k_overall) of DOO with HOO• radicals in aqueous and less polar phases (pentyl ethanoate) were 3.76 × 10² M⁻¹ s⁻¹ (when considering the influence of the molar fraction of HOO• for the water environment) and 1.54 × 10⁵ M⁻¹ s⁻¹, respectively, with the rate in the pentyl ethanoate phase particularly surpassing that of the reference antioxidant, Trolox. Furthermore, it was demonstrated that in aqueous conditions, the fHAT mechanism dominated over SPLET, as indicated by k_fHAT-total > k_SET-total. These findings highlight DOO as a promising antioxidant with potency to scavenge HOO• radicals in lipid environments.

Two new crystalline salts of l-cystine, [l-cystinium(2+) bis-iodide monohydrate (l-CsnH₂)(I)₂·H₂O (I) and l-cystinium(2+) bis-triiodide (l-CsnH₂)(I₃)₂ (II)], were obtained and characterized structurally, by vibrational spectroscopy and their electronic structure by quantum chemical calculations (CASTEP Package) in the framework of density functional theory (DFT). The bandgap of (II) was also determined experimentally by diffuse reflectance spectroscopy. Both salts crystallize in the orthorhombic space group P2₁2₁2₁. The composition and structure of (I) differ from those previously known chloride and bromide salts. A specific supramolecular anionic substructure was found in the structure of (II).

Exposure to benzaldehyde and benzoic acid poses risks to the environment and human health. The phosphoborane nanotube (PB-NT) has been identified as the primary material for research to detect these toxic and volatile substances. Besides, PB-NT material exhibits geometric stability, underpinned by a negative formation energy. After the adsorption of the benzaldehyde and benzoic acid onto the PB-NT, a reduction in the energy gap at all sites are noticed. Moreover, Density Functional Theory (DFT) calculations substantiate the geometric stability of PB-NT, which exhibits a band gap of 1.282 eV. Upon the adsorption, the band gap reduces significantly, decreasing by up to 60.76% for benzaldehyde and 34.63% for benzoic acid, thereby enhancing conductivity. The computed adsorption energy values, - 0.926 eV for benzaldehyde and - 1.196 eV for benzoic acid indicate that these interactions are characterized as physisorption. This property facilitates rapid desorption and contributes to the reusability of the sensor. Notably, the estimated recovery time for benzaldehyde is in the millisecond range, positioning PB-NT as a promising candidate for real-time monitoring applications. Furthermore, ab initio molecular dynamics (AIMD) simulations conducted at 300 K confirm the thermal stability of PB-NT. The future outcome of the proposed work with these results will lay inroads to the practical applicability of PB-NT in air quality sensors and biosensors warranting assessment for commercial viability, and enhancing its feasibility for practical use in various industries.

3-benzoyl-1,1-dimethyl-thiourea (3BDMT) is an important derivative of thiourea that has potential applications in different fields like medical, coordination and organic chemistry, pharmaceuticals, material science, and agriculture. This potential remains underexplored, leading to a lack of biological activity, electronic properties, or detailed structural characteristics of 3BDMT in the literature. This study discovered a new polymorph of 3BDMT and focuses on providing detailed information of the crystal structure, packing, molecular geometry, chemical stability, electronic properties, Hirshfeld surface (HS), and the interactions unique to both existing Form I and new Form II of 3BDMT. We used both experimental and computational approaches to establish this structural-property relationship. Form I and the new Form II were formed by concomitant crystallization and were characterized and confirmed by X-ray diffraction, differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy techniques. The existing Form I and new Form II of 3BDMT have different morphologies and crystal packing, resulting in different energy of interaction, stability, and structural properties. The geometry of the experimental structures was in excellent agreement with the calculated geometry of the molecules at the B3LYP-D3/def2-TZVP level of theory. The presence of π⋅⋅⋅π stacking energies in the new Form II contributes to its energy of interaction and making the structure more stable than the existing Form I. This correlates with the higher enthalpy of melting observed in the DSC analysis for the new Form II 3BDMT structure. This finding suggests that both structures are chemically stable, but the new Form II is more stable than the existing Form I. The compounds’ chemical stability is essential in the synthesis and formulation of the molecules for applications and the exploration of the compounds’ biological and catalytic activities. The large theoretical energy gap of 3.98 eV in both existing Form I and new Form II of 3BDMT indicates that the molecules are stable and might be chemically reactive, making them useful in organic synthesis, coordination, and chemistry. Since the synthesis of various thiourea groups has shown that there is potential for the thiourea derivatives, the discoveries from this study have shed insight and could help in harnessing the potential applications of 3BDMT.

This study presents the synthesis and characterization of a new dithiocarbazate ligand (2-acetyl-pyridine-S-p-clorobenzyl-dithiocarbazate – HL) and its Cu(II) and Zn(II) complexes, [Cu(L)(Cl)] (1), [Cu(L)(Br)] (2), [Zn(L)(μ-CH₃COO)]₂ (3), and [Zn(L)₂] (4)_. The single-crystal X-ray diffraction analyses revealed that the ligand coordinates through its thiol tautomer by the NNS donor atom system to the metal center. The Cu(II) complexes are monomers with a square geometry. In contrast, complex (3) is presented as an asymmetric dimer with acetate bridges linking two Zn(II) atoms and shows a square base pyramid geometry. Complex (4) is a mononuclear compound with an octahedral geometry. UV–Vis spectra show ligand–metal charge transfer bands in all complexes and the IR spectra confirm the absence of the υ(N–H) and υ(C = S) stretching modes. The mass spectrometry shows the compounds [M + H]⁺ molecular ions, their isotopic distribution, and characteristic fragmentations. The ¹H NMR spectra of the ligand and zinc complex confirmed the thione tautomer of the dithiocarbazate. Hirshfeld surface analysis confirmed the intermolecular interactions in the crystal structures through the d_norm function and shape index functions, and the analysis of the fingerprint plots that quantified all the existing contacts. To explore the details of the electronic and vibrational structure of the synthesized complexes, a theoretical study was carried out using density functional theory (DFT) and its time-dependent variant TD-DFT to elucidate the nature of the main electronic transitions.

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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.