In this paper, we have synthesized water‐soluble peripherally tetra and octa‐({6‐[3‐(dimethylamino)phenoxy]hexyl}oxy) groups substituted zinc (II) phthalocyanines (DM‐C6‐ZnQ and o‐DM‐C6‐ZnQ). Also, we have investigated ct‐DNA binding, supercoiled plasmid DNA cleavage properties of DM‐C6‐ZnQ and o‐DM‐C6‐ZnQ by using spectrophotometric and electrophoretic methods. On the other hand, cytotoxic and phototoxic effects of DM‐C6‐ZnQ and o‐DM‐C6‐ZnQ were examined using (3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay on human lung adenocarcinoma (A549) cell lines. In UV–Vis absorption studies, hypochromism was observed about 18% for DM‐C6‐ZnQ and 57% for o‐DM‐C6‐ZnQ on addition of increasing concentrations of ct‐DNA. The intrinsic binding constant (Kb) values of DM‐C6‐ZnQ and o‐DM‐C6‐ZnQ were 3.82 (±0.14) × 104 M−1 and 2.34 (±0.05) × 105 M−1, respectively. The supercoiled plasmid DNA cleavage studies showed that DM‐C6‐ZnQ and o‐DM‐C6‐ZnQ had no DNA damage actions in the dark. On the other hand, they caused DNA damage depending on the light dose. In the MTT assay, the compounds had low cytotoxic properties on A549 cell lines, but they showed significant phototoxic actions. These results reveal that the compounds interact with DNA and have phototoxic properties; it has been determined that they have the potential to be photosensitizing agents for photodynamic therapy.

In this work, 3-({6-[3-(dimethylamino)phenoxy]hexyl}oxy)phthalonitrile ( 2) and the target zinc (II) phthalocyanine (3) and its ammonium derivative (3a) are synthesized, and the phototoxic effects of 3a were examined using different methods on A549 lung cancer cells. Then, the toll-like receptor (TLR) signaling pathway was examined to determine the cell death mechanism in the A549 cancer cells. The results showed that 3a did not have noticeable cytotoxic actions on A549 cells at used concentrations. However, the compound markedly reduced the cell viability when irradiated by the red light for 5 and 15 min (LumaCare/LC-122A/LC2020-09-784, Prob: LUM L [700 nm CL] [15 mW cm À2 ]). Additionally, Annexin V/PI staining suggested that the cells were induced apoptosis in the presence of 3a (1 μM) when irradiated with red light for 15 min. Furthermore, the expression of TLR2, TLR4, and caspase-3 significantly increased and phospho-nuclear factor kappa B/total nuclear factor kappa B decreased compared with that of control group (p < 0.05). These results provide strong evidence that 3a is able to induce A549 cell death in a dose and a red-light irradiation time-dependent manner via apoptosis. Therefore, 3a might be an effective photodynamic therapy candidate for lung cancer treatment.