Some polymer ligands of N-vinylimidazole-co-N-vinylpyrrolidone (Plm) having different mole fractions of N-vinylpyrrolidone have been prepared. Successive formation constants for the complexation of CuII with these Plms in aqueous solutions have been determined by means of spectrum deconvolution at pH 3.5. The present results demonstrate that the successive formation constants are given by K1 = [CuL]/[Cu][L], K2 = [CuL2]/[CuL], K3 = [CuL3]/[CuL2] and K4 = [CuL4]/[CuL3] (charge omitted, L = imidazole residue on Plm). The results clearly indicate that the concentration ratio, [CuL]:[CuL2]:[CuL3]:[CuL4], is largely constant for a given Plm when the concentration of imidazole residues is varied. The values of K2, K3 and K4 decrease with increasing mole fraction of vinylpyrrolidone residues (VPRo) in the Plms. The successive formation constants increase in the order K2 < K3 < K4 for poly(N-vinylimidazole), whereas the reverse (i.e. K2 > K3 > K4) is found for Plm with a VPRo mole fraction of 0.8. Above this VPRo mole fraction, CuL4 species are rarely formed. These results also suggest that the distributions of CuLn species in CuII-Plm solutions can be controlled by adjusting the content of VPRo in the Plm.
|Number of pages||4|
|Journal||Journal of the Chemical Society, Faraday Transactions|
|Publication status||Published - 1994|
ASJC Scopus subject areas
- Physical and Theoretical Chemistry