STRUCTURAL INVESTIGATION OF IRON(III) AND COPPER(II) COMPLEXES WITH POLY(VINYL ALCOHOL) BY NMR TECHNIQUES

Structures of the iron(III) and copper(II) complexes with poly(vinyl a lcohol) (PVA) have been investigated in full detail by NMR techniques, especially through analysis of nuclear magnetic relaxation processes due to paramagnetic metal ions. As a result, it appears well establish ed that the complexes are of a kind in which iron(III) or copper(II) h ydroxide-like clusters are included by PVA chains with hydrophobic bac kbones toward the inside clusters and with hydrophilic OH groups towar d the outside bulk water, meaning that the interaction between the clu sters and PVA is of a hydrophobic type. By such an interaction, the co mplexes have certain definite structures, because there is always a li near relationship between the H-1 NMR signal intensity of PVA and the concentration of metal ion in every system of complex formation. In th e case of the PVA of not less than 250 in the degree of polymerization , however, there has also appeared another linear relationship with a more gentle slope over a relatively high concentration range of iron(I II), suggesting that such PVA molecules can form both complexes contai ning only one and two or more clusters.