Synthesis, Photophysical and Biological Properties of New Phthalocyanines Bearing Peripherally 4-(Trifluoromethoxy)phenoxy Groups

In this study, a novel phthalonitrile derivative namely 4-(4-(trifluoromethoxy)phenoxy) phthalonitrile (2) was introduced and characterized. A number of peripherally tetra-substituted phthalocyanines (H₂Pc, CuPc and PdPc) were obtained by cyclotetramerization of 2 in suitable high-boiling solvents. Characterization of the resulting phthalocyanines has been performed by diverse techniques such as NMR, FTIR and UV/Vis spectroscopy. Organic solvents like acetone, N,N-Dimethylformamide (DMF) and dichloromethane (DCM) were utilized to investigate the influence of solvent nature on aggregation behavior of CuPc. In addition, the aggregation properties of the CuPc were studied in tetrahydrofuran (THF) and DCM at different concentrations ranging from 4×10 ⁻⁶ to 14×10 ⁻⁶ m. Fluorescence quantum yields of H₂Pc and PdPc were determined in DMF. Fluorescence lifetime for H₂Pc was calculated 2.07 ns, as well. The fluorescence quenching feature of H₂Pc was explored by adding different concentrations of benzoquinone in DMF. The values of K_sv and k_q for H₂Pc were obtained 59.01 m⁻¹ and 28.51 m⁻¹ns⁻¹, respectively. Moreover, tyrosinase inhibition and antioxidant activities of the phthalocyanines were studied by using TLC dot –blot technique and spectrophotometric assay. CuPc exhibited the highest inhibitory activity on tyrosinase enzyme. All tested molecules showed moderate antioxidant activity.