Synthesis and photophysical properties of silicon phthalocyanines with axial siloxy ligands bearing alkylamine termini.

Eleven silicon phthalocyanines which can be grouped into two homologous series [SiPc[OSi(CH3)2(CH2)nN(CH3)2]2, n = 1−6 (series 1), and SiPc[OSi(CH3)2(CH2)3N((CH2)nH)2]2, n = 1−6 (series 2)] as well as an analogous phthalocyanine, SiPc[OSi(CH3)2(CH2)3NH2]2, were synthesized. The ground state absorption spectra, the triplet state dynamics, and singlet oxygen quantum yields of 10 of these phthalocyanines were measured. All compounds displayed similar ground state absorption spectral properties in dimethylformamide solution with single Q band maxima at 668 ± 2 nm and B band maxima at 352 ± 1 nm. Photoexcitation of all compounds in the B bands generated the optical absorptions of the triplet states which decayed with lifetimes in the hundreds of microseconds region. Oxygen quenching bimolecular rate constants near 2 × 109 M-1 s-1 were measured, indicating that energy transfer to oxygen was exergonic. Singlet oxygen quantum yields, ΦΔ, were measured, and those phthalocyanines in which the axial ligands are term...