Structural Chemistry最新文献

A theoretical study of the formation of carbamic acids of pyrazole and indazole has been carried out using DFT computational methods. The effects of the substituents and the solvent (using explicit and implicit solvent models) have been considered. In addition, the deprotonation of the carbamic acid and its influence on the stability of the system has been calculated. In the neutral systems, only the formation of indazole-1-carbamic acid derivatives is favored vs. the non-covalent complexes between pyrazole or indazole with CO₂. The deprotonation of the carbamic acid highly stabilizes the system preventing its dissociation.

In the current work, we report the synthesis and characterization of N-((1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)carbamothioyl)benzamide by reacting 4-aminoantipyrine and benzoylisothiocynate in equimolar ratio. Moreover, the compound was characterized by single crystal XRD analysis. The various intermolecular interactions stabilized the supramolecular assembly, including H-bonding and interaction involving π-ring. Hirshfeld surface analysis was performed in order to probe intermolecular interactions in detail. Interaction energy calculations were conducted to find the type of interaction energy prominent in stabilizing supramolecular assembly. The quantum parameters of the prepared compound were investigated by utilizing the Def2-SVPD basis set in conjunction with the hybrid method of B3LYP. The results revealed quite similarities between the experimental and theoretical calculations. In addition, the HOMO orbitals are located at the hetero atoms, while the LUMO orbitals are located at the benzene ring. In addition, the prepared compound was docked with Ampicillin-CTX-M-15. The results showed good binding interaction between the ligand and the targeted amino acids, with the best binding score of − 5.26 kcal/mol.

Two new salts of l-proline containing triiodide anions were obtained and investigated: (l-ProH···l-Pro)(I₃) (I) and [(l-ProH)₃(l-Pro)](I₃)₃ (II). Both compounds crystallize in the polar monoclinic space group P2₁. Crystal structure determinations showed that (I) contains a dimeric cation formed by an O-H···O hydrogen bond with an O···O distance of 2.458(4) Å, while (II) features a peculiar tetrameric cation [l-ProH···(l-Pro-H-l-Pro)···l-ProH], where (l-Pro-H-l-Pro) is a pseudocentrosymmetric dimer with a very short hydrogen bond with an O···O distance of 2.427 Å. Infrared spectra of both crystals were registered and interpreted based on their structures. Electronic band structures were determined by quantum chemical calculations. The CASTEP code was used to calculate the band structures, total and partial density of states (TDOS, PDOS). Bandgaps were also measured by the diffuse reflectance method.

The adsorption attributes of methyl naphthalene and naphthalene molecules on P-Germanane sheets are explored based on the density functional theory method. The novel P-Germanane stability is established based on formation energy and phonon band spectrum. The stable P-Germanane exhibits a band gap of 3.944 eV. The calculated adsorption energy infers that methyl naphthalene and naphthalene are physisorbed on P-Germanane sheets. The charge transfer reveals that P-Germanane sheets behave as donors of electrons and target molecules behave as acceptors. The electronic attributes of P-Germanane sheets get altered owing to methyl naphthalene and naphthalene adsorption inferred from the band structure, PDOS spectrum, and electron density difference diagrams. We identified global minima position upon adsorption of 1-methylnaphthalene, and naphthalene on P-Germanane, which are named as bridge, octal, and tetra sites and adsorption attributes are explored in these sites. The adsorption energy and relative energy gap variation are noticed to be maximum for tetra site orientation of naphthalene on P-Germanane. The outcome exposes that P-Germanane sheets can be used as adsorption substrates for the detection of methyl naphthalene and naphthalene molecules.

Arno Penzias and Robert Wilson in their Nobel-Prize-winning discovery detected the temperature in the outer space to be 3 kelvins. This provided decisive support for the Big Bang model of the birth of the Universe. Penzias was a refugee from Nazi Germany and his new homeland, the United States, provided an excellent education for him. His fruitful career at Bell Labs and in advising small companies combined with a keen interest in societal matters and contemporary politics.

Derivatives of 1,4-dihydropyridine, 1,4-dihydropyrimidine, and its azolo analogs possess a wide range of biological activity and are involved in cellular bioenergetics. Dihydrocycles can be oxidized up to corresponding aromatic ones due to two one-electron transfers. Mechanism of the oxidation process was modeled as a stepwise change of the 1,4-dihydropyridine, 1,4-dihydropyrimidine, and pyrrolo-1,4-dihydropyrimidine using different levels of theory (Hartree–Fock, MP2, DFT), basis sets, and models of environment (vacuum approximation, PCM model describing a non-specific influence of polarizing environment, or PCM model with an explicit water molecule describing both non-specific and specific influence of neighboring molecules). It is shown that the potential of the first one-electron transfer I₁ depends on the level of theory and the model of an environment used in calculations. The potential of the second one-electron transfer I₂ depends only on the model of an environment. The analysis of their differences calculated using different approaches has revealed the dependence only from the level of theory. Since DFT methods provide the geometric characteristics of 1,4-dihydroheterocycles closest to the experimental data, it seems reasonable to use these relatively cheap calculations to study the oxidation process.

A large data set of over 30 thousand organic compounds containing carbon, nitrogen, oxygen, fluorine, and hydrogen was collected, and the density of each compound was predicted by 1D descriptors derived from its molecular formula and 2D descriptors derived from its constitutional structural features. The 2D structural features are composed of Benson’s groups, corrected groups, and 2D structural features of the whole molecular structures. All the descriptors were extracted by an in-house program in Java with a function to ensure that each atom (or bond) of molecules is represented by Benson’s groups once for atom-based (or bond-based) descriptors. Partial least square (PLS) and random forest (RF) methods were used separately to build models to predict the density. Further, the variable selection of descriptors was performed by variable importance of RF. For partial least square, the combination of the models constructed by descriptors based on the atoms and the bonds achieved the best results in this paper: for the cross-validation of the training set, the Pearson correlation coefficient (R) = 0.9270, mean absolute error (MAE) = 0.0270 g·cm⁻³, and root mean squared error (RMSE) = 0.0426 g·cm⁻³; for the prediction of the test set, R = 0.9454, MAE = 0.0263 g·cm⁻³, and RMSE = 0.0375 g·cm⁻³.

The Nobel Prize of Physiology or Medicine 2023 was awarded jointly to two researchers, Katalin Karikó and Drew Weissman, for their discoveries taking part in the development of effective mRNA vaccines against COVID-19. The accelerated development of the novel mRNA-lipid nanoparticle vaccines provided highly effective protection against severe disease or death, and reduction in symptomatic illness, before a full year had passed from the beginning of the pandemic.

The phenoxyacetic acid and its derivatives have attracted considerable attention as they have proven to be excellent bioactive herbicides. The optimized molecular geometry and the fundamental vibrational frequencies of 4-methyl-phenoxyacetic acid (4MPA), 4-acetyl-phenoxyacetic acid (4APA) and 4-tert-butyl-phenoxyacetic acid (4TBPA) have computed using density functional theory (DFT) method with 6–311++G(d,p) basis set. The theoretically predicted wavenumbers are found to be in close agreement with the experimentally determined one. The band gap energy of HOMO and LUMO depicts the charge transfer interactions occurring within the molecules. Global reactivity descriptors have utilized to assess the chemical reactivity. It has been observed that 4APA exhibits good electrophilic properties with a higher electrophilicity index (ω = 2.993 eV) compared to other compounds such as 4TBPA and 4MPA. The molecular electrostatic potential surface (MESP) has been plotted over the optimized structure to estimate the reactive sites of electrophilic and nucleophilic attacks on the phenoxyacetic acid molecule. Fukui function is also used to analyze their electrophilic and nucleophilic descriptors with Hirshfeld charges. Electron localization function (ELF) and local orbital localizer (LOL) are discussed using the multifunction wavefunction (Multiwfn) analyzer. Using the HerbiPAD tool, the herbicide-likeness parameter has exposed the good herbicide-like behaviour of the title compounds. Additionally, the Tice rule and pK_a are described, providing valuable insights into the herbicidal activity of phenoxyacetic acid compounds. The 4APA compound is highly effective, which exhibits more herbicidal activity when interacting with the auxin receptor TIR1. It demonstrates a strong binding affinity of -8.56 kcal/mol.

Many 1,2,4-triazole derivatives have high biological activity. They are of interest for scientific and practical human activity as potential drugs and pesticides. In this work, we report a synthesis of a series of new 3-amino-1,2,4-triazole derivatives containing an alkylamide moiety. It was found that the amidoalkylation of 3-amino-1,2,4-triazole N-(1,2,2,2-tetrachloroethyl)carboxamides in the presence of triethylamine occurred selectively at the endocyclic nitrogen atom N-1 with the formation of the corresponding N-(1-(5-amino-1H-1,2,4-triazol-1-yl)-2,2,2-trichloroethyl)carboxamides. The reaction products were isolated in 79–85% yields and characterized by ¹H NMR and ¹³C NMR spectroscopy. To unambiguously establish the structure of the obtained compounds, we carried out X-ray diffraction analysis for N-(1-(5-amino-1H-1,2,4-triazol-1-yl)-2,2,2-trichloroethyl)-3-methylbutanamide.