| Abstract: | Hemin (H) (ferri–protoporphyrin IX chloride) was complexed in aqueous media with the following polymer ligands; poly(L -lysine), poly(L -histidine), branched polyethyleneimine, and two copolymers of 1-vinyl-2-pyrrolidone with 1-vinylimidazole and with 1 -vinyl-2-methylimidazole. The resulting water-soluble complexes were either the five- or six-coordinate hemichromes, respectively, which coordinated one or two ligand units in polymer to ferri—protoporphyrin IX (FP). The coordination behavior of cyanide ion to the hemichromes and also to H was investigated by means of spectroscopic titration method. It was found that one cyanide ion binds not only to the five-coordinate hemichromes, but also to the six-coordinate ones by the ligand exchange reaction with the cyanide ion, whereas two cyanide ions coordinate to H, which is free from polymer ligand able to occupy the coordination site(s) of FP. Morever, the degree of saturation of the iron(III) in FP with cyanide ion for all the hemichromes was found to be much larger than that for H. These results indicate that the ability of FP to coordinate cyanide ion is closely associated with whether one coordination site of FP is occupied by polymer ligand or not. |
