Structural Chemistry最新文献

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.

Average crystallographic structures may disguise more complex packing modes, such as commensurate modulations that originate from coherent librational distortions of the lattice. These can be easily overlooked, with striking implications on the understanding of intermolecular interactions, provided that the crystal is described in terms of colorless symmetries. As shown in the 1970s by Kołakowski, lattice modulations with strong librational components can be understood in terms of colored group operations applied to pseudovector quantities, like rotation momenta. Here, we employ Kołakowski’s concepts of dynamic symmetry to computationally predict modulated distortions in crystalline acrylic acid. We show that periodic lattice distortions may indeed originate from a low-frequency phonon instability at the (Gamma) point of the first Brillouin zone. The packing of the corresponding molecular libration momenta is analogue to an antiferromagnetic ordering in the I_cbam Shubnikov group, which can be also described as a commensurate modulation emerging from (3 + 1)D Imcb(00γ)0s0 superspace structure with γ = 1. In the reciprocal lattice, the distortions produce exceptions to the systematic extinction rules, due to the scattering at commensurate Bragg points that derive from the reduced colorless symmetry. This evidence offers an easy strategy to look for such phenomena in X-ray experiments, also taking advantage of the sensitivity of modern area detectors. Implications on the onset of phase transitions in organic crystals are also discussed.

In a 1999 article of Structural Chemistry, the recently deceased J. Fraser Stoddart and two associates surveyed the interplay between the synthesis of functioning supramolecular systems and their X-ray crystallographic investigation. Furthermore, they charted the anticipated development and necessary work for creating “intelligent” materials with predetermined functions. This was part of Stoddart’s discoveries in creating molecular machines that brought him a share of the chemistry Nobel Prize in 2016.

Three new nickel-based representatives of the so-called “layered hydroselenite” family have been characterized by single-crystal X-ray diffraction. In addition to the (enH₂)[Ni(HSeO₃)₂Br₂], the last missing member of the ethylenediammonium – transition metal hydroselenite-halide family, we were able to characterize the first members of a new family of compounds based on the N,N′-dimethylethylenediammonium cations, (dmedaH₂)[Ni(HSeO₃)₂X₂], X = Cl and Br. We compare the structural peculiarities of layered hydroselenites “stuffed” by the (enH₂)²⁺ and (dmedaH₂)²⁺ cations and predict existence of new series in this peculiar layered family.