Complexes of vitamin B 6—XXI. The affinity of the binary complexes of the 2,2′-bipyridyl copper(II) system to the vitamin B 6 compounds

Abstract

The interaction of the vitamin B 6 (VB 6) compounds, pyridoxol (P), pyridoxal (PL) and pyridoxamine (PM), with the binary species 2,2′-bipyridyl (BP) of copper(II) has been studied potentiometrically and polarographically at an ionic strength of 0.15 M Cl −. The potentiometric data at 37°C were assessed by the SUPERQUAD program. The results indicated that BP enhances ternary complex formation with vitamin B 6 compounds, especially with P and PL. The differential pulse polarographic technique further confirmed the formation of ternary species, especially at pHs greater than 5.5. The ternary complex enhancement was discussed in terms of log K 1 (log β 111 i -log β 1010-log β 011 i ) and log K 2 (2 log β 111 i -log β 2010-log β 0211 i ).