Spectroscopic and photophysicochemical behaviour of novel cadmium phthalocyanine derivatives tetra-substituted at the alpha and beta positions

The syntheses of three cadmium phthalocyanine derivatives tetrakis{1,(4)-(4-benzyloxy)phenoxyphthalocyaninato} (5a), tetrakis{1,(4)-(2-pyridyloxy)phthalocyaninato} (5b) and tetrakis{2,(3)-(4-benzyloxy)phenoxyphthalocyaninato} (6a) are reported here for the first time. Spectroscopic and photophysical properties have also been determined and the results are discussed here paying particular attention to the influence of various organic solvents in relation to the position and type of substitution. Singlet oxygen quantum yields (ΦΔ) and photodegradation quantum yields (ΦPd) have also been discussed. The triplet quantum yields have been determined and ranged from ΦT = 0.36 to 0.85, where the peripherally (β) substituted derivatives generally give higher values than those substituted at the non-peripheral (α) positions. The triplet lifetimes ranged from τT = 5 to 40 μs. In all cases (except toluene, due to the lack of data), the highest singlet oxygen quantum yields obtained were for the pyridyloxy-substituted derivatives 5b (ΦΔ = 0.60 in DMF) and 6b (ΦΔ = 0.74 in DMSO).