Synthesis and photophysicochemical properties of novel zinc phthalocyanines mono substituted with carboxyl containing functional groups

This work reports on the synthesis and the physicochemical properties of novel unsymmetrically substituted zinc phthalocyanines (complexes 8, 10 and 11) and their symmetrically substituted counterparts (complexes 9, 12 and 13). The new complexes and their counterparts were successfully structurally characterized by IR, NMR, mass spectral and elemental analyses. Low fluorescence quantum yields (0.032) and lifetimes (0.91 ns) were obtained for the symmetrical ZnOTPc (complex 9) compared to the higher fluorescence quantum yields (0.15, 0.13, 0.10, 0.09 and 0.29) and lifetimes (4.4, 1.69, 1.69, 2.16 and 3.23 ns) obtained for ZnMPCPc (8), ZnTDTPc (12), ZnMCapPc (10), ZnMCafPc (11) and ZnTCPPc (13), respectively. All the complexes showed the ability to produce singlet oxygen with the highest triplet quantum yields obtained for 8 and 10 (0.80 and 0.65 respectively). High triplet lifetimes (109–286 μs) were obtained for all complexes. Complex 8 showed the longest triplet and fluorescence lifetimes as well the largest triplet state and singlet oxygen quantum yields.

► Monocarboxy zinc phthalocyanines have been synthesized.
► The complexes are unsymmetrically substituted.
► The fluorescence quantum yield is higher for the monocarboxy phenoxy complex.
► The monocarboxy phenoxy complex has the longest triplet lifetime.