ABSTRACT
Abstract .................................................................................................................126 Aim and Background ............................................................................................126 4.1 Introduction .................................................................................................126 4.2 Experimental Part ........................................................................................128 4.3 Results and Discussion ...............................................................................130 4.4 Conclusion ..................................................................................................146 Keywords ..............................................................................................................147 References .............................................................................................................147
As the nitrogen atoms are likely to be key points of the TPC macrocycle structure, there was an intention to conduct a sequential aza-substitution of all four CH groups in the TBP molecule to form phthalocyanine, with a fairly representative group of metal complexes with different degrees of the ligand bond ionicity, and explore changing of the photoelectrochemical characteristics of the films of produced pigments. Thus, the set of considered measurements on films of aza-substituted metal-derivatives of tetrabenzoporphyrin in combination with the data of quantum-chemical calculations of the electron density and energy characteristics of the pigments, leads to several conclusions: sequential substitution of carbon atoms in meso-position by nitrogen increases the electron density in the area under consideration with the corresponding increase of charges in the p-electronic bonds; the obvious consequence of the increase of electron density in the important area of structural conjugation of macrocycle is a ring currents increase and compression of the cycle, which leads to a considerable increase of the intermolecular interaction; consequences of the strengthening of the intermolecular interactions are bathochromic red shift of the absorption maxima, the increase in the extinction coefficients and the broadening of the absorption bands in the visible part of the spectrum, as well as the hypochromic shift of the Soret band; accordingly with the changes in the optical characteristics of the pigments it takes place a reduction of the band gap, lowering of the energy level of the valence band, increasing of the depth of acceptor levels formed by the adsorbed oxygen; from a practical point of view, the redistribution of electron density in the very structurally similar molecules leads to a significant increase in chemo-and light-fastness of pigments and oxidation potentials, to an 8-10 fold increase in the photocurrent, 1.6-1.8 fold increase in photopotentials, 2-5 fold in the quantum yield on a current.
