Synthesis, characterization, and DFT study of some transition metal complexes with Schiff base derived from 2-acetylthiophene and L-methionine

New Schiff base; (S)-4-(methylthio)-2-((1-(thiophen-2-yl)ethylidene)amino) butanoic acid (LH); was synthesized by condensation of 2-acetyl thiophene with methionine in a mole ratio of 1:1 and characterized with(1)H-C-13 NMR, UV-Vis, FT-IR and MS methods. The metal complexes of manganese(II), cobalt(II), nickel(II), copper(II), and zinc(II) were prepared by direct reaction of the ligand (LH) and the metal chlorides which structurally characterized with spectroscopic methods, magnetic, and conductivity measurements. The data showed that the Schiff base LH ligand behaves as a bidentate via nitrogen atom of imine group and oxygen atom of carboxylic methionine moiety. The results obtained from magnetic moments, electronic spectra, mass spectra and elemental analyses confirmed the tetrahedral geometry around the central metal ions. The optimization of geometry, vibrational band assignments, frontier molecular orbitals, and absorption spectrum of the compounds were investigated by DFT/B3LYP/6-31 + G(d,p) methods. Natural bond orbital analysis was carried out for the investigation of major stabilizing orbital interactions.