ABSTRACT
There were studied photoelectrochemical properties of thin films of 45 tetrapyrrole compounds with extraligands (ETPC), deposited on a platinum substrate by thermal sublimation in vacuum 10-6 Torr. The films have a cluster structure, where generally polycrystalline film (a-form) with a thickness of 50 nm is composed of differently oriented clusters (10-20 nm in size) with a monocrystalline structure. Quantum-chemical calculations of the electron density distribution in molecules of ETPC have been carried out, the results of which became the basis for the interpretation of experimental data. It is shown that, as compared with the complexes of bivalent metals, ETPC have significantly higher photoactivity. This is due to a change of the coordination of electron acceptors in completing the coordination sphere of metals and an increase in intermolecular interaction due to the overlapping of the electron clouds of the extraligands that come out of the plane of pigment molecules. The effect decreases on the formation of dimmers coupled by extraligands, and the photo activity falls to zero at diphthalocyanines of lanthanides, which can be regarded as a limiting form of extra coordination with a second phthalocyanine macrocycle as an extraligand. Most photo activity is observed in ETPC with a high degree of iconicity of the bond of a metal to a ligand and one extraligand having large electron affinity.
