Potentiometric and NMR studies of ternary metal complexes of thiamine orthophosphate.

Abstract

Ternary metal complexes of the type MLA. (where M=Cu(II) Zn(II), Ni(lI) and Co(ll); L=thiamineorthophosphate (TOP); A=glycine, alanine, phenylalanine. tryptophan, tyrosine, pyrocatechol, oxalic acid, malonic acid, imidazole, benzimidazole and 5,6 dimethyl benzimidazole) have been investigated potentiometrically at 350C and m= 0.1 <em>M</em> (KNO₃). The stability constants have been determined using BEST Computer program. The stabilities of the ternary complexes have been quantitatively compared with the stabilities of the corresponding binary metal complexes (MA) which are determined under identical experimental conditions with respect to ligand 'L'. The stability of ternary complexes increases in the order O-O donors &lt; N- O- &lt; N-donors. Interactions of these Iigands by TOP and tryptophan or TOP and imidazole with Zn(II) is also studied by ¹H NMR spectroscopy.