In present work, the photochemical effects (singlet oxygen quantum yield (Phi(Delta)) and photodegradation quantum yield (Phi(d))) of the peripherally tetra 4-(3-(piperidinium-1-ylmethyl)phenoxy substituted zinc(II) phthalocyanine (Zn6a) were investigated spectrophotometrically. Afterwards, the cytotoxic and phototoxic properties of Zn6a were investigated on human lung adenocarcinoma (A549), colorectal carcinoma (HCT-116) and human keratinocytes (HaCaT) healthy cell lines using (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) to determine the PDT potential of the compound. The Phi(Delta) and Phi(d) of Zn6a were determined as 0.69 and 3.62 x 10(-5) in DMSO. The results of cytotoxicity showed that Zn6a had low cytotoxic effects on A549, HCT-116 and HaCaT cell lines after 24 h. In the presence of light irradiation, the viabilities of A549 were 36 +/- 5.50% and 17 +/- 1.40%, respectively at 5 and 10 mu M. In addition, the cell viabilities were 43 +/- 4.40% and 28 +/- 1.70%, respectively at same concentrations of Zn6a against HCT-116 cells. The results showed that the difference in cell viabilities between irradiation and non-irradiation cells were statistically significant aganist A549 and HCT-116 cell lines. The results showed that Zn6a had low phototoxic properties on healthy cells whilst it had high phototoxicity on A549 and HCT-116 carcinoma cell lines, showing that the compound had a promising photosensitizer agent for PDT. (C) 2020 Elsevier B.V. All rights reserved.