Multiplicity of Histidine-Cu(II) Complexes

Abstract

THE stability constants of the histidine complexes of several metals have been determined by several workers^1–4. Satisfactory values of the stability constants can be calculated from titration data for all the metals investigated except Cu(II). Albert³ suggested that the anomalies in the histidine – Cu(II) system are due to the planar configuration of cupric complexes in solution, which makes it impossible for all the three sites available for co-ordination (amino, imidazole and carboxyl) to be bound simultaneously to the metal ion. It has been shown⁵ that other anomalies also occur in the co-ordination of Cu(II) by histidine.