PART I; PEPTIDE SYNTHESIS UTILIZING THE INORGANIC PROTECTING GROUP PENTAAMMINECOBALT(III). PART II; A STUDY OF COBALT AND RUTHENIUM COMPLEXES WITH BINUCLEAR CHELATING LIGANDS AS INTERMEDIATES FOR WATER OXIDATION.

摘要

In part I the use of the pentaammineaquocobalt(III) ion for the protection of the carboxylate group of an amino acid or peptide in peptide synthesis is described. Techniques are developed for the rapid synthesis and purification of polypeptides with special reference to the synthesis of the hexapeptide (Glycylhistidine)(,3). The pentaamminecobalt(III) group was found to be a useful carboxylate protecting group and permitted when used in conjuction with the amine protecting group t-butyloxycarbonyl the rapid step-wise synthesis of polypeptides in solution. The advantages of the pentaamminecobalt(III) group include its charge, color and solubility properties it confers on the protected peptide.;In part II the design and synthesis of binuclear transition metal complexes for the investigation of the oxidation of water to dioxygen is described. The synthesis of the binuclear chelating ligand 1,4bis(1,4,7triazacyclonon-1-ylmethyl)benzene (PXBCN) is presented. This ligand was then used in the synthesis of binuclear complexes with cobalt and ruthenium. The bis cobalt u-peroxo complex of the binuclear ligand showed that a dioxygen bridge could form between the metal ions. The formation of a dioxygen bridege between two metal centers is proposed as an intermediate in a mechanism for the oxidation of water to oxygen. The spectroscopic and electrochemical characterization of the ruthenium complexes with 1,4,7triazacyclononane and PXBCN are presented and the results discussed in light of recent reports on complexes that catalyze the oxidation of water to oxygen. Oxidation of the ruthenium(III) mononuclear and binuclear complexes results in the formation of u-oxo bridged species. These complexes did not mediate the oxidation of water to oxygen.