Structural Chemistry最新文献

Modification of materials to achieve specific changes in their physical and chemical properties often involves the substitution of ions. While this process is commonly discussed in structural terms, our recent publication focussed on exploring the thermochemical consequences, including enthalpy, entropy, heat capacity, and formula unit volume, associated with substituting monocharged cations for sodium ions as a reference set. In the current study, we extend our analysis to investigate the consequences of substituting monocharged anions, specifically the halides F⁻, Br⁻, and I⁻, as well as H⁻, OH⁻, and NO₃⁻, for chloride anions. This exploration is conducted through least-squares regression analysis of data obtained from 431 chloride ion-exchanged materials. In the case of cation substitutions, the regression trendlines for different substitutions appear to be roughly parallel to each other but vertically displaced. For anion substitutions, however, the trendlines for enthalpy and formula unit volume exhibit a fan-like spread from their data origin. We delve into the reasons behind this observed difference. A detailed analysis of a few outliers is undertaken to identify potential reasons for the discrepancies. These findings contribute to a better understanding of the implications and variations in ion substitutions, shedding light on the intricacies of material modification processes.

On October 22, 1934, in a fateful experiment, Enrico Fermi and his associates at the University of Rome discovered that neutrons in hydrogen-rich media slow down and acquire enhanced capability for nuclear reactions. The utilization of this phenomenon had far-reaching implications in science and world events.

The cellular antioxidant defense mechanism against reactive oxygen species (ROS) depends on selenium, a vital trace element. Numerous selenium-containing compounds have recently displayed a wide range of biological characteristics that make them intriguing scaffolds in medicinal chemistry. Among the several categories of phytoestrogens, Imidazole-Based Selenium N-heterocyclic carbene Compounds (IM-SeNHC) have drawn the most scientific attention. Several IM-SeNHC compounds were chosen for this theoretical study analysis. The goal of this study was to govern the binding capacity of each of the selected IM-SeNHC that have been identified as inhibitors of the proteins responsible for cancer EGFR, hTrkA, HER2, and cMet (PDB codes: 5GTY, 6PL2, 7JXH, and 3RHK, respectively). DFT and molecular docking investigations were carried out employing in silico software for their virtual screening. Conferring to the docking study, ligand 6 formed hydrogen bonds with protein 7JXH’s active pocket, followed by ligand 8 with protein 3RHK and 5GTY, and ligand 9 with protein 6PL2. Conferring to trends in polarizability and dipole moment, the energy difference values (0.299 eV and 0.277 eV) of IM-SeNHC compounds (3 and 8) show the rise in chemical potential, reactivity, and bioactivity brought on by the most stable structural configurations. Additionally, ADME was investigated to discover the pharmacokinetic characteristics of the targeted moieties. The cardiotoxicity analysis was performed, and confidence percentages accompanying these predictions vary across the dataset, ranging from around 57 to 99.9%, indicating differing levels of certainty in the predictions. This research showed that these ligands have a promising future in cancer therapy medications.

The year 1874 is considered to be the birth of stereochemistry when the third dimension in describing and discussing structures in chemistry was first introduced. Stereochemistry and structural chemistry are closely related though they are not each other’s synonyms. Structural chemistry implies greater emphasis on metrical aspects and stereochemistry on shape, symmetry, and chirality. We review some of the nodal points in the early development of stereochemistry.

Para-tert-butylthiacalix[4]arenimines with mono- and distally substituted functional groups have been examined in terms of their structure and spectra. The structure and H-bonds of these compounds can be studied by comparing their vibrational and NMR spectra. The spectra of several conformations of the molecules TCA1-4 were calculated. For the molecules TCA3 and TCA4, the most stable conformation is a distorted cone (DC2) with the same imine or phthalimide group orientation, consequently. The least stable conformation is pinched cone (PC). The conformations of molecules TCA2, TCA3, and TCA4 are DC1 and DC2, respectively. H-bonds in the molecules TCA1-4 alter their supramolecular properties. Ionization energy and dipole moment decrease as monosubstituted thiacalixarene (TCA1) transforms into disubstituted TCA2. In this instance, there is an increase in softness, electrophilicity, chemical potential, and electron affinity. An increase in the number of methylene groups in disubstituted thiacalixarenes from TCA4 to TCA2 is accompanied by an increase in ionization energy, electron affinity, and electrophilicity.

Novel nickel(II) ethylenediamine compound, [Ni(en)₃](2-chlorophenylacetate)₂, has been synthesized and characterized by spectroscopic techniques (UV-vis, FT-IR), thermogravimetric analysis, magnetic moment, molar conductivity measurement, and single-crystal X-ray diffraction analysis. The complex crystallizes in a triclinic crystal system with P (overline{1}) space group with cell dimensions of a = 8.9050(2), b = 12.5620(4), c = 14.0590(4) Å, α = 102.259(2)°, β = 107.172(2)°, and γ = 106.914(2)°. The complex consists of [Ni(en)₃]²⁺ as the cationic part and two discrete 2-chlorophenylacetate ions as anionic counterparts divulging the existence of a second sphere complex with distorted octahedral geometry. Besides electrostatic forces of attraction, non-covalent interactions (hydrogen bonding and C-H…π) sew the second sphere in extended three-dimensional supramolecular architecture and provide robustness to the crystal lattice. Field electron scanning microscope (FESEM) and energy dispersive X-ray spectra (EDX) were employed to study the surface morphology of the structure. To explore the structural insights and bonding in the complex theoretical studies, i.e., density functional theory (DFT) and Hirshfeld surface analysis have also been employed.

In recent years, there has been a growing interest in cocrystals as potential materials for nonlinear optical (NLO) applications due to their enhanced optical properties compared to their individual components. Understanding the influence of solvent interactions on the NLO responses of cocrystals is crucial for the development of efficient optoelectronic devices. In this study, we investigate the solvent-assisted fast-switching behavior and the enhanced NLO responses of a cocrystal formed by 3,5-dihydroxybenzoic acid and pyrazine-2-carboxamide. The NLO responses vary across solvents, with linear polarizability < α₀ > ranging from 4.36 electrostatic units (esu) in methanol to 11.98 in chloroform, and first hyperpolarizability (β₀) from 0.21 esu in methanol to 7.44 esu in chloroform. The second hyperpolarizability γ_tot values range from 1.21 esu in toluene, dichloromethane (DCM), and methanol to 2.34 esu in the gaseous phase. Our research aims to elucidate the influence of solvent interactions on the NLO properties of this cocrystal, providing insights for potential applications in optoelectronic devices. We found that the cocrystal produced the steeper NLO response upon changing the solvent polarity. The comparison of the values in different solvents shows that chloroform has the highest < α₀ > β₀ values, indicating a strong response to the applied electric field. Meanwhile, methanol has the lowest < α₀ > and β₀ values, indicating a weaker response. The γ_tot values for all solvents are relatively close, with the gaseous phase having the highest value at 2.34 and chloroform having the lowest value at 1.37.

The growing interest in a material composed of Cu single atoms and/or their sub-nanometric clusters deposited on titania prompted us to perform systematic theoretical studies on the system comprising the anatase phase of titania, modelled by a (TiO₂)₃₄ cluster with copper particles of 1–7 atoms on top of it. The ground-state geometric structures were proposed and compared with the available literature data derived from EXAFS experiments done for Cu-TiO₂ materials. Copper atoms prefer to aggregate and form larger clusters on TiO₂, as seen from the computed nucleation energies. The models were characterised by the following electronic properties: electronic band structure, natural population charges, and frontier orbitals (HOMO, LUMO, and SOMO). The copper phase becomes oxidised once it is deposited on titania. The charge distribution in the resulting structures indicates that the atoms that are the closest to the Cu-TiO₂ interface would become the active sites for catalytic processes; copper atoms would act as electrophilic, while oxygen atoms would act as nucleophilic. The calculated binding energies between the two phases show that the formation of the composite system is favourable from the thermodynamic point of view, and the interaction between the small copper clusters and the titania surface is mostly of electrostatic nature.

A novel coordination CuCl₂(L)₂ complex was synthesized by complexation of the 2-thiophenimidazoline ligand with CuCl₂.2H₂O in less than 10 min. The synthesis was done using ultrasound irradiation in an ethanol solvent. The complexation was confirmed using CHN and FT-IR analysis and linked to the theoretical IR and DFT calculations. The single-crystal X-ray diffraction approach was employed to figure out the arrangement of atoms in the crystal structure of the CuCl₂(L)₂ complex. The copper ion is coordinated by two symmetry-related non-chelating 2-thiophenimidazoline ligands and two symmetry-related chlorine atoms. 2-Thiophenimidazoline ligands coordinate with the metal center by N-atom, whereas S-atom does not coordinate with the metal center. The X-ray results revealed a square planar coordination geometry, as evident from the respective bond angles around the Cu(II) ion. Hirshfeld surface analysis was done to learn more about intermolecular contacts. Theoretical calculations were carried out using DFT employing the B3LYP/Def2-TZVP level of theory, which showed that theoretical conclusions were reliable with experimental data.

This study presents a theoretical investigation of the [3 + 2] cycloaddition (32CA) reaction between cyclic nitrone a1 and substituted alkene b1. The mechanism, regioselectivity, and stereoselectivity of this 32CA reaction were analyzed using transition state theory and reactivity indices obtained from conceptual density functional theory (DFT) at the B3LYP/6-311G(d) level of theory. The results indicate that this cycloaddition reaction proceeds via an asynchronous one-step mechanism, exhibiting a non-polar nature and significant activation energies. These theoretical results are in agreement with the experimental observations. The study also employs topological analyses such as ESP, RDG-NCI, and ELF to determine active sites; distinguish hydrogen bonds, van der Waals interactions, and steric repulsive interactions; and predict electron localization, respectively.