Thermodynamic considerations in co-ordination. Part X. A potentiometric and calorimetric investigation of copper(II) histidine complexes in solution

Abstract

The copper(II)–histidine (histH) system has been investigated at 25·0 °C, l= 3·00M(Na⁺)ClO₄-(a) potentiometrically, by use of normalised curve analysis of copper amalgam data and least-squares analyses of glass electrode data, and (b) calorimetrically. If (p,q,r) represents the general complex (hist^–_p Cu²⁺_q. H⁺_r), the complexes found between pH 3·0 and 10·4 were (1,1,0), (2,1,0), (1,1,1), (2,1,1), (2,1,2), and (1,1,–1). Enthalpies of formation were measured for the first five complexes and structures are suggested for all six.