Experimental and Computational Studies on Heteroaromatic Diimines

Tetradentate Schiff bases (diimines); 1,4-bis[3-(thiophene-2-carboxaldimine)propyl]piperazine (L1) and 1,4-bis[3-(furan-2-carboxaldimine)propyl]piperazine (L2) have been synthesized by the reaction of diamines with thiophene/furan aldehydes. The structure of heteroaromatic diimines have been determined by elemental analysis and spectroscopic methods (1H-NMR, 13C-NMR, UV-vis, FT-IR and LC-MS). 1H and 13C shielding tensors for L1 (furbap) and L2(tkbap) were calculated with GIAO/DFT/B3LYP/6-311++G(d,p) methods in CDCl3. The vibrational band assignments, frontier molecular orbital energies (FMOs), nonlinear optical (NLO) activity, reactivity descriptors, molecular electrostatic potential surfaces (MEPs) and Mulliken atomic charges were studied at B3LYP/6-311++G(d,p) level of theory. Diimine copper(II) complexes have been synthesized and structurally characterized by using UV-vis, FT-IR, and LC-MS spectra, magnetic susceptibility and molar conductivity measurements. Schiff bases and Cu(II) complexes have been screened for their biological activities by microdilution technique (MIC values in mM) using DMSO as solvent on different species of pathogenic bacteria.