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The tri-component synthesis of novel chiral benzimidazole Mannich bases, by reaction between benzimidazole, aqueous 30% formaldehyde and an amine, the biological evaluation and DFT studies of the new compounds are reported here. The 1 H-NMR, 13 C-NMR, FTIR spectra and elemental analysis confirm the structures of the new compounds. All synthesized compounds were screened by qualitative and quantitative methods for their in vitro antibacterial activity against 4 bacterial strains. DFT studies were accomplished using GAMESS 2012 software and HOMO-LUMO analysis allowed the calculation of electronic and structural parameters of the chiral Mannich bases. The geometry of 1-methylpiperazine, the cumulated Mullikan atomic charges of the two heteroatoms and of the methyl, and the value of the global electrophilicity index (ω = 0.0527) of the M-1 molecule is correlated with its good antimicrobial activity. It was found that the presence of saturated heterocycles from the amine molecule, 1-methyl piperazine and morpholine, respectively, contributes to an increased biological activity, compared to aromatic amino analogs, diphenylamino-, 4-nitroamino-and 4-aminobenzoic acid. The planarity of the molecules, specific bond lengths and localization of HOMO-LUMO orbitals is responsible for the best biological activities of the compounds.

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In this paper, an extended isomerization study of a series of nitro/cyano mono- and disubstituted azo-monomers and related azo-poly­(methacrylate)­s is conducted by UV–vis and 1H NMR spectroscopy. The experiments, carried out in both toluene and dimethylformamide (DMF), reveal an intriguing behavior. The monosubstituted azo-derivatives, thermally relax monotonously via inversion mechanism, in both solvents. Interestingly, the disubstituted azo-derivatives reveal stable Z isomers in DMF, while in toluene they exhibit very fast relaxation, by inversion. The particular stability of Z isomers in DMF is explained in terms of solvent–solute interactions, using quantum chemical calculations and Fourier transform-infrared spectroscopy. In addition, the information–transmission capability with time of one disubstituted azo-monomer is highlighted. The study reveals that the nature and position of substituents on the azo-moiety, and as well as their interaction with the solvent, have a crucial importance for the Z–E thermal relaxation and for the displayed photochromic properties.