Synthesis, structural characterization, and investigation on photophysical and photochemical features of new metallophthalocyanines

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In this report, the 3,7,11-trimethyl-2,6,10-dodecatrien-1-ol group was substituted to the peripheral positions of the phthalocyanine macrocycle for obtaining copper (II) 4, cobalt (II) 5 and zinc (II) 6 phthalocyanine derivatives starting from the phthalonitrile derivative 3. This group was also axially substituted to the silicon (IV) phthalocyanine for the synthesis of silicon(IV) phthalocyanine 8 starting from silicon(IV) phthalocyanine dichloride 7 (SiPcCl2). The newly synthesized phthalocyanines 4–6 and 8 exhibited good solubility in tetrahydrofuran, ethyl acetate, CH2Cl2, N,N-dimethylformamide, diethyl ether, CHCl3, ethyl alcohol, DMSO, and acetonitrile. The novel compounds were structurally characterized by LC-MS/MS (for the phthalonitrile derivative 3), 1H NMR (for the compounds 3, 6 and 8), 13C NMR (for the compound 3), FT–IR, elemental analysis, UV–Vis spectroscopy (for phthalocyanines) and MALDI–TOF mass spectral data (for phthalocyanines). The aggregation behavior, photophysical and photochemical properties such as fluorescence lifetime and quantum yields, singlet oxygen and photodegradation quantum yields of 6 and 8 were explored in dimethylsulfoxide (DMSO) to the determination of the potential use of these novel phthalocyanines as photosensitizers in photodynamic therapy (PDT) applications. The newly synthesized zinc(II) phthalocyanine (6) showed high singlet oxygen generation in DMSO when compared to unsubstituted zinc(II) phthalocyanine that used the standard. The studied phthalocyanine complexes 6 and 8 exhibited moderate degradation under light irradiation. These results indicate that the studied phthalocyanines 6 and 8 can be a candidate as photosensitizers for PDT.