Synthesis and photoproperties of diamagnetic octabutoxyphthalocyanines with deep red optical absorbance

Article abstract of DOI:10.1021/ja00178a032

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 AIPc(OBu)₈OSiEt₃, GaPc(OBu)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 × 10⁵ and 2.2 × 10⁵ M^-1cm^-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 lifetime 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 (¹Δ_g) 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.