Synthesis and characterization of cobalt(II), nickel(II) and copper(II)-based potential photosensitizers: Evaluation of their DNA binding profile, cleavage and photocytotoxicity

•We have synthesized Co(II), Ni(II) and Cu(II)-based novel Schiff-base photosensitizers.•The complexes interacted with CT-DNA via intercalative mode.•The complexes act as efficient photocleavers of SC pUC19 DNA in UV-A light.•The ΦΔ of 1O2 generation of complexes 1–3 was found to be 0.35, 0.31 and 0.30, respectively.•Photocytotoxicity of the complexes 1–3 against MCF7 cells was studied in UV-A light.

Metal-based photosensitizers of the type [Co(L)Cl2] (1), [Ni(L)Cl2] (2) and [Cu(L)]Cl2 (3), where L = N′1,N′3-bis[(E)-thiophen-2-ylmethylidene]benzene-1,3-dicarbohydrazide have been synthesized and characterized by advanced spectroscopic and analytical techniques. The interactions of the complexes with CT DNA were investigated by viscosity analysis, thermal denaturation and absorption spectroscopic techniques. Absorption spectral (Kb = 5.57 × 104 M−1 (1), 4.45 × 104 M−1 (2), 2.8 × 104 M−1 (3)), thermal denaturation and viscosity measurements reveal that 1, 2 and 3 interact with DNA through intercalation. The complexes are photocleavers of SC pUC19 DNA in UV-A light forming 1O2 as the reactive oxygen species. The in-vitro cytotoxicity of 1, 2 and 3 towards MCF-7 tumor cell lines has been evaluated by MTT method, and show an enhancement of cytotoxicity in UV-A light. The results revealed that complex 1 has superior prospectus to act as cancer chemotherapeutic candidate than that of complex 2 and complex 3.

Graphical abstractA Schiff base N′1,N′3-bis[(E)-thiophen-2-ylmethylidene]benzene-1,3-dicarbohydrazide (L) and it’s Co(II), Ni(II) and Cu(II) complexes have been synthesized and characterized. The DNA-binding properties, DNA-photocleavage efficiency, Quantum yield of singlet oxygen generation and photocytotoxic activity by bivalent metal complexes were demonstrated. The results revealed that the complexes interact with DNA through intercalation, cleave pUC19 DNA in UV-A light forming 1O2 as the reactive oxygen species and show an enhancement of cytotoxicity in UV-A light.Figure optionsDownload full-size imageDownload as PowerPoint slide