In this study; phthalonitrile compounds 4-((5-methyl-1,3,4-thiadiazol-2-yl)thio)phthalonitrile (4) and 3-((5-methyl-1,3,4-thiadiazol-2-yl)thio)phthalonitrile (5) were synthesized. These compounds were converted to their respective peripherally and non-peripherally tetra-substituted zinc(II) (6 and 7) and lead(II) (8 and 9) phthalocyanine derivatives. The novel phthalocyanine complexes were characterized by using different spectroscopic techniques including FT-IR, UV-Vis, H-1 NMR and mass. The spectroscopic, photochemical and photophysical properties of the phthalocyanines were investigated for determination of their potential as photosensitizers for photodynamic therapy. In addition, the effects of the substituent, binding position and the variety of central metal ions in phthalocyanine core on photochemical and photophysical properties were determined. (C) 2019 Elsevier B.V. All rights reserved.