Formation Constants of Poly(vinyl alcohol)-Bivalent Transition Metal Complexes

Abstract

Formation constants for the complexes of poly(vinyl alcohol) (PVA) with bivalent transition metal ions, i. e. Co(II), Ni(II), Cu(II) and Zn(II) were measured by using the modified Bjerrum's method proposed by Gregor and co-workers in an aqueous solution of ion strength 0.1 at 25° C. The formation curves for Cu(II) and Zn(II) complexes showed that the each metal ion was coordinated by four hydroxyl groups involved PVA, while Co(II) and Ni(II)ion were coordi- nated by four above hydroxy groups (Fig.2). The stability constants, log k1, log k2 and log K increase in the order of Co(II)<Ni(II)<Zn(II)<Cu(II) in agreement with the Irving-Williams series for stability constants (Table 1). Thermodynamic parameters for the above reaction were determined by the Ringbom's method.