PHTHALOCYANINES OF A NOVEL STRUCTURE - DINAPHTHOTETRAAZAPORPHYRINS WITH D(2H) SYMMETRY

Two naphthalene molecule-fused tetraazaporphyrins (TAPs) with D2h symmetry have been synthesized, and some of their spectroscopic and electrochemical properties are reported. These compounds are structural isomers of phthalocyanines (Pcs) in the sense that four benzene units are fused to the TAP skeleton. In contrast to MPcs (M = metal) with D4h symmetry, both the Q0-0 and Soret bands split into two as a result of the lowering of the molecular symmetry. Magnetic circular dichroism (MCD) shows Faraday B terms corresponding to the peaks and shoulders of the electronic absorption spectra, indicating that no degenerate state is included. The fluorescence quantum yield of the zinc complex is much smaller than in ZnPc with D4h symmetry. The electronic absorption and electrochemical redox data of these complexes are reproduced by molecular orbital (MO) calculations within the framework of the Pariser-Parr-Pople (PPP) approximation. The results are compared with those of Pcs and mononaphtho-TAPs.