Synthesis, spectral and thermal studies on cobalt(II), copper(II), nickel(II) and zinc(II) chelates with p-tolylsalicylaldimine and some amino acids

New cobalt(ll), copper(II), nickel(II) and zinc(II) complexes of the p-tolylsalicylaldimine Schiff base (sal-TH) and some amino acids have been prepared. The complexes have the general formula [M(sal-T)(aa)]. nH(2)O where M = Co(II), Cu(II), Ni(II) and Zn(II); sal-T = monoanion of the Schiff base p-tolylsalicylaldimine; aa = monoanion of the amino acids phenylalanine (Phala), tyrosine (tyr) or methionine (met); n = 0 for M = Co(II), Cu(II) or Ni(II) and n = 2 for M = Zn(II). The complexes have been characterized and studied by elemental analyses, conductivity, IR and UV-VIS spectroscopy as well as thermogravimetry. The Cu(II) complexes have been proposed to possess a square-planar structure while the Co(II), NI(II) and Zn(II) complexes have an octahedral structure attained by mutual intermolecular interactions among the adjacent mixed amino acid-Schiff base molecules. The thermal decomposition reaction order and activation energy have been computed by means of the Coats-Redfern and Horowitz-Metzger methods. The biological activity of selected complexes against some bacteria and fungi have been tested.