SYNTHESIS AND PHOTOPROPERTIES OF DIAMAGNETIC OCTABUTOXYPHTHALOCYANINES WITH DEEP RED OPTICAL ABSORBENCY

The synthesis and photoproperties of six new metal 1,4,8,11,15,18,22,25-octabutoxyphthalocyanines and photoproperties of the known, analogous Zn and metal-free phthalocyanines are described. The new compounds are AlPc(OBu)8OSiEt3, GaPc(0Bu)8OSiEt3, GePc(OBu)8(OSiEt3)2, SnPc(OBu)8(OSiEt3)2, RuPc(OBu)8(py)2, and PdPc(OBu)8 (where Pc(OBu)8 represents the octabutoxyphthalocyanine ligand). Benzene-d6 solutions of all eight of the compounds give NMR spectra showing large ring-current effects. Benzene solutions of the compounds give visible spectra with absorption maxima in the 688-779-nm range having extinction coefficients between 1.0. cross. 105 and 2.2. cross. 105 M-1 cm-1. The triplet-state properties of the phthalocyanines in benzene solutions have been measured by laser flash photolysis. The triplet states have absorption maxima in the 550-640-nm range, quantum yields in the 0.1-0.9 range, and lifetimes when the solutions are deaerated in the 0.5-150-μs range. The rate constants for energy transfer from the triplet states of the compounds to O2 are between 1.3 ⨯ 108 and 2.8 ⨯ 109 M-1 s-1. Analysis of kinetic data pertaining to the photogeneration of O2 (1Δg) by the main-group compounds shows that the energy gap between their singlet (S1) and triplet (T1) states is 14.9 ± 0.3 kcal/mol. Relationships between the photoproperties of the metal complexes and the position in the periodic chart of the metals they contain are apparent. © 1990, American Chemical Society. All rights reserved.