Binary and mixed-ligand complexes of creatinine and L-asparagine with first-row transition metal ions: Potentiometric studies

Abstract

Creatinine is a physiological component of blood, brain and muscles and an important bioligand, which is the last product of the nitrogen metabolism in the vertebrates. In this study, the stability constants of binary complexes formed by creatinine with Cu(II), Co(II), Mn(II), Cr(III), and of the mixed-ligand complex Cu(II)-creatinine-l-asparagine were determined by the Calvin-Bjerrum and Irving-Rossotti methods. The protonation constant and dissociation constant of creatinine was found to be 4. 90 at 25 C and for I= 0.1. The conditional formation constants and the formation pH ranges of complexes were determined. Relative abundance was plotted using conditional formation constants of the complexes and the steps of the complexes are shown in graphs. The composition of metal-creatinine complexes was determined as metal/ligand = 1: 1.