Chemical speciation and biological activity of bivalent metal complexes of polydentate amide ligands

Abstract

Stability constants of N,N'-bis-(3-carboxy-l-oxopropanyl)-1,2-ethylenediamine(L₁), N,N'-bis-(3-carboxy-l-oxopropanyl)- 1,2-phenylenediamine(L₂), N,N' -bis-(2-carboxy-l-oxophenelenyl)-1,2-phenylenediamine(L₃) have been determined in aqueous medium (for L₁ & L₂) and 75% (v/v) m ethanol-water medium for L₃ <i>p</i>H-metrically. The formation constants

(logβ_n) have been calculated using the Bjerrum half <img src='http://www.niscair.res.in/jinfo/nbar.gif' border=0> integral method and weighted least squares method. Species distribution curves of complexes have been plotted as a function of <i>p</i>H which shows at lower <i>p</i>H values 1: 1 complexes are formed and 1:2 complexes are formed at neutral or higher <i>p</i>H. The biological study indicates that ligands and their complexes are better fungicidal than bactericidal. Copper complexes of all the ligands showed potential antifungal and antibacterial activities. Ligand L₃ and its copper(II) complexes are most effective against <i>A. niger. E. coli </i>and <i>S. aureus.</i>