Synthesis, photophysics and photochemistry of tin(IV) phthalocyanine derivatives

Abstract

The synthesis, photophysical and photochemical properties of peripherally (β) and non-peripherally (α) tetra-substituted aryloxy tin(IV) phthalocyanines are reported. The complexes presented are 1,(4)(tetraphenoxyphthalocyaninato) ( 7a); 2,(3)(tetraphenoxyphthalocyaninato) ( 8a); 1,(4)-(tetra tert-butylphenoxyphthalocyaninato) ( 7b); 2,(3)(tetra tert-butylphenoxyphthalocyaninato) ( 8b); 1,(4)-(tetra 4-benzyloxyphenoxyphthalocyaninato) ( 7c) and 2,(3)(tetra 4-benzyloxyphenoxyphthalocyaninato) ( 8c) tin(IV). The trends in triplet, fluorescence, singlet oxygen and photodegradation quantum yields are described for these compounds. The complexes exhibited high triplet quantum yields ( Φ T) ranging from 0.69 to 0.89 due to the spin–orbit coupling induced by Sn, which has a large atomic number, and this resulted in lowering of fluorescence quantum yields. The peripherally substituted derivatives ( 8a, 8b and 8c) showed marginally higher fluorescence quantum yield values ( Φ F = 0.014, 0.010 and 0.011, respectively) compared to non-peripherally substituted derivatives ( 7a, 7b and 7c) which gave Φ F = 0.008, 0.007 and 0.008, respectively). The singlet oxygen quantum yields ( Φ Δ) ranged from 0.58 to 0.75 indicating a potential use of these complexes as photosensitizers. Triplet lifetimes were generally low, ranging from 30 to 50 μs. Photoreduction of the complexes in the absence of oxygen was observed during photolysis due to ring reduction.