Development of Novel Tetrapyrrole Ligands and Their Metal Complexes with New Functions

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Macrocyclic structure with tetrapyrrole skeleton is great interest because of its unique structure and function. In this study, porphycene and hemiporphycene which are structural isomers of porphyrin have been synthesized. Each structure was-determined by X-ray crystal analyses. These ligands complex with various transition metal, and especially substiution effect with macrocycle skeleton of its iron and cobalt complex was studied. The cobalt(II) complexes of a series of peripheral substituted porphycene ligands with bromine have been synthesized and its various properties have been investigated by means of CV,UV-VIS and NMR spectroscopies. Linear relationships between the number of bromine and various physicochemical properties were observed.Reconstituted myoglobin with iron porphycene as an artificial prosthetic group exhibits an extremely high molecular oxygen affinity and low autooxidation rate. This study showed that the modification of the heme framework will serve as an effective method for the creation of a unique functionalized hemoprotein.Hydrophobic vitamin B12 which is tetrapyrrole pigment was immobilized onto various electrode by a sol-gel reaction. The complex was physically retained in a silica gel film which is formed on an electrode. The immobilized complex exhibits the Co(II)/Co(I) redox couple and retain its electrochemical activity. This electroactive complex shows a high reactivity towards organic halides, and the controlled-potential electrolysis of benzyl bromide using the sol-gel modified electrode at -1.2 V vs. Ag/AgCl in aqueous solution afforded dehalogenated products, bibenzyl and toluene, with a total turnover number over 1000 for 1 hour.