Conductance stopped-flow study of the complexation reaction of poly(4-vinylpyridine) with nickel(II) ions

Abstract

The equilibrium and kinetic parameters of Ni²⁺ complexation with poly(4-vinylpyridine)(PVP) have been estimated using the conductance stopped-flow (κ-SF) technique in a mixture of methanol + water (55/45 vol%). Coordination of four pyridine ligands of the polymer with Ni²⁺ are assumed in the analysis. Relaxation traces of the κ-SF measurements were obtained by mixing Ni²⁺ and PVP solutions. The complexation and dissociation rate constants of unprotonated ligands of PVP with Ni²⁺ are 4500 dm³ mol^–1 s^–1 and 6.6 s^–1, being close to those of the low-molecular-weight ligands, e.g. imidazole. The complexation rate of monoprotonated polymer ligands is very small (ca. 10 dm³ mol^–1 s^–1).