4-(4,5-Diphenyl-4H-1,2,4-triazol-3-ylthio)phthalonitrile ( 3) and its non-peripherally tetra substituted zinc(II) phthalocyanine (4) and magnesium(II) phthalocyanine (5) derivatives were prepared. The novel compounds 3-5 were characterized spectroscopically. To determine the photodynamic therapy potential of 4 and 5, their photophysical and photochemical properties were investigated. The magnesium(II) phthalocyanine (5) showed the highest fluorescence quantum yield. In addition, non-peripheral substitution of the 4-(4,5-diphenyl-4H-1,2,4-triazol-3-ylthio) groups on the phthalocyanine ring did not affect the fluorescence properties of the phthalocyanines. The zinc(II) phthalocyanine (4) exhibited the highest singlet oxygen quantum yield value. The 4 and 5 exhibited lower photostability than Std-ZnPc. These results show that the zinc(II) phthalocyanine (4) can be used in photodynamic therapy applications with its singlet oxygen production and photostability. (C) 2020 Elsevier Ltd. All rights reserved.