SEMICONDUCTING BEHAVIOR OF SUBSTITUTED TETRA-AZAPORPHYRIN THIN-FILMS IN PHOTOELECTROCHEMICAL CELLS

Photoelectrochemical properties of zinc(II) and copper(II) complexes o f (1) phthalocyanine, (2) tetrapyrido[2,3-b;2', ,3''-1;2''',3'''-q]-5, 10,15,20-tetra-azaporphyrin, and (3) rapyrazino[b;g;l;q]-5,10,15,20-te tra-azaporphyrin, were investigated in thin-film electrodes prepared b y vacuum deposition (VD), drop-casting (DC) and in situ synthesis (IS) . The opposing behavior, photoreduction at electrodes of 1 and photo-o xidation at electrodes of 2 and 3, are discussed in terms of a band-en ergy shift of tetra-azaporphyrin macrocycles caused by substitution wi th heterocyclic pyrido and pyrazino groups. The photoelectrochemical e fficiency of the electrodes is strongly affected by the film morpholog y which is dependent on the preparation methods, and increased in orde r of DC < VD < IS.