Visible and near-IR spectroscopic and photochemical characterization of substituted metallophthalocyanines

M. GABRIELA LAGORIO, LELIA E. DICELIO AND ENRIQUE SAN ROMÁN

Journal of Photochemistry and Photobiology A: Chemistry

Elsevier Sequoia

Año: 1993 vol. 72 p. 153 - 161

The UV-visible spectra of copper(II) tetracarboxyphthalocyanine (CuTCPc), copper(II) tetrapentyloxycarbonylphthalocyanine (CuTPOCPc) and hydroxoaluminium tricarboximonoamidephthalocyanine (AlTCPc) were studied as a function of concentration in various solvents. Dye aggregation equilibria were investigated and pure monomer and dimer spectra were obtained. Near-IR absorption maxima for the above compounds and for cobalt(II) dicarboxydiamidephthalocyanine (Co(II)TCPc) and dicyanocobalt(III) dicarboxydiamidephthalocyanine (Co(III)TCPc) were also obtained and their assignment to triplet-multiplet transitions is discussed. The analysis of the monomer and dimer spectra on the basis of exciton theory and results obtained from molecular mechanics computational calculations allows conclusions to be drawn on the monomer and dimer structures and observed differences in aggregation ability to be interpreted. Quantum yield of singlet molecular oxygen photoproduction by monomers and dimers were determined for aluminium and copper dyes by steady state irradiation using diphenylisobenzofuran as singlet oxygen quencher. The lack of activity in dimers, in accordance with the literature available, is interpreted in terms of the vibronic coupling between monomeric units in the dimer (exciton theory).