NOVEL METHOD FOR DETERMINATIONS OF THE SUCCESSIVE FORMATION-CONSTANTSFOR COMPLEXATION OF TRANSITION-METAL IONS WITH POLYMER LIGANDS

The successive formation constants for the complexation of copper(II) with poly(N-vinylimidazole) (PVIm) have been determined by means of sp ectral deconvolution. Based on these results, definitions of the succe ssive formation constants for the complexation of transition metal ion s with multidentate polymer ligands are proposed. These are K-1 = [CuL ()]/[Cu][L(*)], K-2 = [CuL(2)(*)]/[CuL(*)], K-3 = [CuL(3)(*)]/[CuL(2) ()], and K-4 = [CuL(4)(*)]/[CuL(3)(*)] (L(*) is ligand residue on the polymer, charge omitted). The definitions of K-2, K-3, and K-4 are qu ite unlike the generally used definition, and the difference is ascrib ed to the nature of a polymer chain, which makes a microheterogeneous region in the solution. The results indicate that the concentration ra tio [CuL()]:[CuL(2)(*)]: [CuL(3)(*)]:[CuL(4)(*)] is constant when [L( )] is varied. Present results seem to strongly suggest that the commo nly used definitions of the successive formation constants for the com plexation of transition metal ions with multidentate polymer ligands w ould be replaced by those proposed here, and re-examinations of the co mplexation of transition metal ions with multidentate polymer ligands may be necessary.