Complexation Equilibria and Coordination Aspects of Zn(II) Complexes Contain 2 Aminobenzamide and some Bioactive Amino acid Mixed Ligands: pH-metric, Spectroscopic and Thermodynamic Studies

摘要

Mixed ligand complexation of 2 aminobenzamide (2AB) as ligand [L] with Zn(I1) in the presence of some bio relevant amino acid constituents like glycine (gly), L alanine (ala), L valine (val) and L phenylalanine (phe) as ligand [B] have been investigated using pH metric measurements with a combined pH electrode at different temperatures (300, 310, 320 and 330 +/- 0.1 K) in 50% (v/v) ethanol water mixture containing I = 0.15 M NaClO4 as supporting electrolyte. Computer assisted analysis of the experimental titration data showed the presence of ZnLB and ZnLB2 species as mixed ligand complexes in addition to various binary species. In ZnLB/ZnLB2 species, both primary and secondary ligands act as bidentate to form a stable six, five membered chelate ring. The calculated stabilization parameter Alog K, log X, log X' and % R.S. values clearly show the mixed ligand complexes have higher stabilities than their binary. Thermodynamic parameters Delta G, AH and AS have been derived from the temperature dependence of the stability constants. The complexation behavior of ZnLB species has been studied by means of electronic spectra. The percentage distribution of various binary and mixed ligand species of each type of the complexes in solution depending on pH and the ratio of Zn(1) to 2 aminobenzamide/amino acid of the systems.