Electronic spectra of π ion-radical dimer of porphyrin derivatives

The electronic spectra of pi ion-radical dimer of porphyrin derivatives were studied based on the spectroelectrochemistry of copper(I) meso-tetrakis (4-N-methylpyridyl) porphyrin tetrachloride salt (CuTMPyP) and the fluorescence spectra of partly protonized 5, 10, 15-(4-hydroxy phenyl)-20-(4-hexadecyloxy phenyl) porphyrin (P-31) LB film. The face-to-face dimer formed through the SOMO'-LUMO interaction between the electroreduced CuTMPyP anion-radical and the ground state molecule shows Q band at 480 nm and pi*-pi* band at 820 nm. The face-to-face dimer produced by the SOMO-HOMO interaction between the protonized P-31 cation-radical and the ground state molecule shows the Q band absorption at the range of 470 similar to 515 nm; and the pi-pi band at 710 nm. These Q bands are blue-shifted.