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Microwave assisted condensation of 3-acetyl-2,5-dimethylthiophene (1) and 9-ethyl-9H-carbazole-3-carbaldehyde (2) gave 1-(2,5-Dimethylthiophen-3-yl)-3-(9-ethyl-9H-carbazol-3-yl)prop-2-en-1-one (chalcone) (1.1) which was cyclized to pyrazoline (1.2, 1.3), and pyrimidine (1.4, 1.5) derivatives. All the synthesized compounds were subjected to antibacterial activity evaluation using two Gram + ve and two Gram-ve bacterial strains and were tested for any possible toxic effect to the mammalian cells. Density functional theory was used to understand the electronic structure of the studied molecules. All the molecules were modeled and optimized using B3LYP/6-311 + G** level of theory. The relationship between activities and Frontier Molecular orbital (HOMO and LUMO orbitals) of the compounds is also discussed. Docking studies were also performed. The observed results revealed that the pyrazoline skeleton is a promising lead structure, which displays higher in vitro antibacterial efficacy, probably by interacting and inhibiting the glucosamine-6-phosphate synthetase enzyme (GlmS). Theoretical calculations are in good agreement with the in vitro and in silico findings.

1,1′-Bis (1-methyl pyridinium-2-yl)-4,4′-dipyridinium dichloride di-iodide (TPy) and 1,1′-dimethyl-4,4′-dipyridinium di-iodide (DPy) have been synthesized and used as corrosion inhibitors for ferritic type 430 stainless steel in 0.5 M H 2 SO 4 solution. Polarization, weight loss and scanning electron microscopic measurements confirm the inhibitive action of these compounds and the increase in inhibition efficiency with an increase in concentration and temperature. The compounds enhance the passivation of the steel by increasing suppression of the critical current. The quantum chemical calculations explain the good adsorption of these compounds on the steel surface and the greater inhibition efficiency for TPy compared with that of DPy inhibitor.

The electronic structure of salicylideneaniline (SA) and some of its derivatives are investigated both experimentally and theoretically. The equilibrium geometric structures of the studied compounds are determined at the B3LYP/6-311++G** level of theory. A set of 12 substituted SA derivatives is considered in the present work. The choice of these substituents aims to create a push-pull system on the SA basic structure which would shade light onto its photo physics. The electronic absorption spectra of SA are recorded in the UV-VIS region, in both polar and nonpolar solvents. Assignments of the observed electronic transitions are facilitated via time-dependent density functional theory (TDDFT) computations at the same level of theory. Electronic configurations contributing to each excited state are identified and the relevant MOs are characterized. The extent of delocalization and intramolecular charge transfer are estimated and discussed in terms of natural bond orbitals (NBO) analysis and second order perturbation interactions between donor and acceptor MOs. Solvent effects on the electronic absorption spectra are discussed in terms of the difference in polarizabilities of the ground and excited states. FTIR spectra of SA and its derivatives are measured in KBr platelets. Detailed vibrational assignments are given based on the calculated potential energy distributions. “IR marker bands” that characterize the SA framework are identified. The effect of substituents, the nature of the characteristic “marker bands”, and intensity quenching of some bands are discussed.