Potentiometric and proton NMR studies on ternary metal (II) complexes containing thiaminepyrophosphate and a series of secondary ligands

Abstract

Ternary metal complexes of the type MLA, where M = Cu (II ),

Zn (II), Ni (II) and Co (II), L = thiaminepyrophosphate (TPP) and

A = glycine, alanine, phenylalanine, tryptophan, tyrosine, pyrocatechol,

oxalic acid, malonic acid, imidazole, benzimidazole, and 5,6- dimethylbenzimidazole have been investigated potentiometrically at

<span style="font-size:14.0pt;font-family:" times="" new="" roman";mso-fareast-font-family:="" "times="" roman";mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="">35°C and μ <span style="font-size:14.0pt; font-family:Arial;mso-fareast-font-family:" times="" new="" roman";mso-ansi-language:="" en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">=0.1<i>M </i><span style="font-size:14.0pt;font-family:" times="" new="" roman";mso-fareast-font-family:="" "times="" roman";mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="">(KNO₃ .The stability constants have been determined using BEST Computer program. The stabilities of ternary complexes increase in the order O¯- O¯ donors <span style="font-size:14.0pt; font-family:Arial;mso-fareast-font-family:" times="" new="" roman";mso-ansi-language:="" en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">< <span style="font-size:14.0pt;font-family:" times="" new="" roman";mso-fareast-font-family:="" "times="" roman";mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="">N - donors. Cu (II) ternary complexes are found to be less stable than the corresponding Co(II), Ni (II) and Zn(II) complexes. Interaction of these ligands, TPP and tryptophan or TPP and imidazole with Zn (II) in deuterium oxide solution are also studied by ¹H NMR.</span></span></span></span></span>