Cobalt(II), Nickel(II) and Copper(II) complexes of a tetradentate Schiff base as photosensitizers: Quantum yield of 1O2 generation and its promising role in anti-tumor activity

In the present investigation, a Schiff base N′1,N′3-bis[(E)-(5-bromo-2-hydroxyphenyl)methylidene]benzene-1,3-dicarbohydrazide and its metal complexes have been synthesized and characterized. The DNA-binding studies were performed using absorption spectroscopy, emission spectra, viscosity measurements and thermal denatuaration studies. The experimental evidence indicated that, the Co(II), Ni(II) and Cu(II) complexes interact with calf thymus DNA through intercalation with an intrinsic binding constant Kb of 2.6 × 104 M−1, 5.7 × 104 M−1 and 4.5 × 104 M−1, respectively and they exhibited potent photodamage abilities on pUC19 DNA, through singlet oxygen generation with quantum yields of 0.32, 0.27 and 0.30 respectively. The cytotoxic activity of the complexes resulted that they act as a potent photosensitizers for photochemical reactions.

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► We have synthesized biologically active M(II) (where MCo, Ni, Cu) complexes.
► The DNA-binding modes of M(II) complexes were studied by different techniques.
► The DNA-photocleavage abilities of M(II) complexes were studied on pUC 19 DNA.
► The quantum yields of 1O2 generation of M(II) complexes were determined.
► The cytotoxicity of M(II) complexes were performed on A549 lung cancer cell lines.