Synthesis, Characterization, and Conductance of Benzimidazolyl Polyacrylate Cu(II), Co(II), and Fe(II) Complexes

The imidazole and benzimidazole nucleus and its derivatives are known to play crucial roles in the structure and functioning of a number of biologically important molecules, generally by virtue of their being coordinated to metal ions. Thus, dimethyl benzimidazole supplies one of the five nitrogen atoms coordinated to Co(II1) in vitamin B,2 and several of its derivatives. Current evidence indicates that the manganese-oxygen evolving system in green plant photosynthesis contains at least some of the metal, not as the porphyrin complex but as manganese bound directly to a protein. In general, metal ions bind to proteins through functional groups that are substituents on the macro polypeptide backbone [I]. Metal-protein binding also involves multidentate coordination to two, three, or more of the coordination positions of the metal ions. Good models for protein-bound metals would then be complexes with multidentate ligands with phenolic oxygen and imine-like nitrogen donors, e.g., tetradentate Schiff base complexes have appeared [2] and very few systems showing the linear relationship between thermal stability of metal chelates and structure of chelating agents have been reported [3]. The present study examines the coordinating behavior of the benzimidazole nucleus, which is on the polytrichlorophenylacrylate backbone, toward metal ions.