Spectroscopic (FT–IR and UV–Vis) and theoretical (HF and DFT) investigation of 2-Ethyl-N-[(5-nitrothiophene-2-yl)methylidene]aniline

Molecular structure determination, spectroscopic, quantum computational studies and molecular docking of 4-(E)-[2-(benzylamino)phenylimino) methyl-2]ethoxy phenol

A Schiff base compound 4-(E)-[2-(benzylamino)phenylimino)methyl-2]ethoxy phenol (4BPM2EP) was synthesized and spectroscopic characterization was performed using experimental methods such as FT-IR, FT-Raman and UV-Vis spectroscopy. Density functional theory (DFT/B3LYP/6-311++G(d,p)) computation was used to investigate the optimized molecular geometry, harmonic vibrational wavenumber, NMR chemical shifts, natural bond orbital (NBO) analysis, non-linear optical (NLO) properties, molecular electrostatic potential (MEP) map and Mulliken atomic charges of 4BPM2EP molecule. TD-DFT calculations have been carried out on the optimized geometry at gaseous phase, DMSO and ethanol to further understand the electronic transitions and solvents effect on the UV-Vis spectra of the compound. The assignments of vibrational modes were performed on the basis of total energy distribution (TED) using VEDA 4 program and were compared with experimental data. Molecular docking study was performed using Glide program to establish the information about the interactions between the topoisomerase DNA gyrase enzymes and the novel compound in order to explore the biological behaviour of the examined compound. The compound screened against four pathogens two gram positive, two gram negative and two fungal strains had shown good anti-bacterial and antifungal behaviour. Furthermore the compound was subjected to in-silico ADMET studies.Communicated by Ramaswamy H. Sarma.

Facile Synthesis of 5-Aryl-N-(pyrazin-2-yl)thiophene-2-carboxamides via Suzuki Cross-Coupling Reactions, Their Electronic and Nonlinear Optical Properties through DFT Calculations

Synthesis of 5-aryl-N-(pyrazin-2-yl)thiophene-2-carboxamides (4a–4n) by a Suzuki cross-coupling reaction of 5-bromo-N-(pyrazin-2-yl)thiophene-2-carboxamide (3) with various aryl/heteroaryl boronic acids/pinacol esters was observed in this article. The intermediate compound 3 was prepared by condensation of pyrazin-2-amine (1) with 5-bromothiophene-2-carboxylic acid (2) mediated by TiCl₄. The target pyrazine analogs (4a–4n) were confirmed by NMR and mass spectrometry. In DFT calculation of target molecules, several reactivity parameters like FMOs (E_HOMO, E_LUMO), HOMO–LUMO energy gap, electron affinity (A), ionization energy (I), electrophilicity index (ω), chemical softness (σ) and chemical hardness (η) were considered and discussed. Effect of various substituents was observed on values of the HOMO–LUMO energy gap and hyperpolarizability. The p-electronic delocalization extended over pyrazine, benzene and thiophene was examined in studying the NLO behavior. The chemical shifts of ¹H NMR of all the synthesized compounds 4a–4n were calculated and compared with the experimental values.

A mononuclear cobalt(II) salophen-type complex: Synthesis, theoretical and experimental electronic absorption and infrared spectra, crystal structure, and predicting of second- and third-order nonlinear optical properties

A tetradentate Schiff base ligand, (4-nitro-N,N'-o-phenylene-bis(5-methoxysalicylideneimine)) (H₂L), and its cobalt(II) complex (CoL•DMF) were synthesized. Elemental analysis, and FT-IR and ¹H NMR spectra were used to confirm the molecular structure of H₂L ligand. In addition, elemental analysis, molar conductance measurement, infrared and electronic absorption spectroscopies as well as single crystal X-ray diffraction were employed to distinguish the molecular structure of the complex that has a slightly distorted square-planar geometry around the cobalt(II) ion. The geometries of H₂L and CoL were optimized by means of the DFT/(U)PBE0/Def2-TZVP level of theory. Good agreement of the optimized geometric parameters of the complex with the corresponding experimental ones and successfully reproduction of the FT-IR spectra of the ligand and complex validated the applied method. Based on the optimized structure of CoL, its electronic absorption spectrum was reproduced by using time-dependent density functional theory (TDDFT) at the same level. Its analysis was carried out to assign the observed electronic transitions and determine their characters. The computed nonlinear optical (NLO) parameters (β, γ and < γ > values) of H₂L and CoL by using TDDFT at the same level combined with the sum-over-states (SOS) method are considerable larger values than reference compound i.e. urea. The ligand and the complex in the absence of nitro and methoxy moieties referred to as H₂L' and CoL' respectively were optimized to elucidate the effect of these moieties on hyperpolarizabilities values.

2,2′-[(Disulfanediyl)bis{5-[(1E)-(2-hydroxybenzylidene)amino]-1,3-thiazole-4,2-diyl}]diphenol: synthesis, crystal structure and calculation of molecular hyperpolarizability

The title Schiff base compound {systematic name: 2-[5-[(E)-(2-hydroxybenzylidene)amino]-4-(2-{5-[(E)-(2-hydroxybenzylidene)amino]-2-(2-hydroxyphenyl)-1,3-thiazol-4-yl}disulfanyl)-1,3-thiazol-2-yl]phenol}, C32H22N4O4S4, incorporating a disulfanediyl (dithio) linkage, was obtained from the condensation reaction between two equivalents of salicylaldehyde and one equivalent of dithiooxamide in dimethylformamide, and was characterized by elemental analysis, IR spectroscopic analysis and single-crystal X-ray diffraction. A one-dimensional chain is formed along the b axis via double intermolecular C—H...S hydrogen bonds. The HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energies and some related molecular parameters were calculated at the B3LYP/6-311G(d,p) level of theory. The molecular hyperpolarizability was also calculated.

Experimental (FT-IR, Laser-Raman and NMR) and theoretical spectroscopic analysis of 3-[(N-methylanilino)methyl]-5-(thiophen-2-yl)-1,3,4-oxadiazole-2(3H)-thione

The structure of a potential bioactive agent namely, 3-[([Formula: see text]-methylanilino)methyl]-5-(thiophen-2-yl)-1,3,4-oxadiazole-2(3[Formula: see text]-thione was characterized by proton and carbon-13 nuclear magnetic resonance (NMR) chemical shifts, Fourier transform infrared (FT-IR) and Laser-Raman spectroscopic techniques. The quantum chemical computations of molecular structures (disorder I and disorder II forms), vibrational wavenumbers, carbon-13 and proton chemical shifts and UV-Vis spectroscopic parameters have been performed with DFT/B3LYP method at 6-311[Formula: see text]G(d,p) basis set. The highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), nonlinear optical (NLO) properties and natural bond orbital (NBO) analyses have been theoretically examined with the mentioned calculation level. The calculated values have been compared with the recorded experimental data. The computed molecular geometric parameters, vibrational wavenumbers, NMR chemical shifts, and UV-Vis wavelengths have been found to be in a good harmony with the experimental values and spectral results of similar structures in the literature. We believe that the work will be of considerable interest to anyone working in the area of theoretical chemistry, whether in industry or academics.