Synthesis, spectral and quantum chemical studies and use of (E)-3-[(3,5-bis(trifluoromethyl)phenylimino)methyl]benzene-1,2-diol and its Ni(II) and Cu(II) complexes as an anion sensor, DNA binding, DNA cleavage, anti-microbial, anti-mutagenic and anti-canc

• A new Schiff base and its Ni(II) and Cu(II) complexes were prepared and characterized.
• Experimental and theoretical studies on a new Schiff base have been reported.
• The potential binding ability of Schiff base and its complexes to CT-DNA was characterized by means of UV–Vis spectroscopy.
• DNA cleavage and cytotoxicity were investigated of compounds by agarose gel electrophoresis and MTT method.
• The colorimetric response of the Schiff base receptors in DMSO has been investigated.

We report the synthesis of a novel Schiff base (E)-3-[(3,5-bis(trifluoromethyl) phenylimino)methyl] benzene-1,2-diol from the reaction of 2,3-dihydroxybenzaldehyde with 3,5-bis(trifluoromethyl)aniline, and its Ni(II) and Cu(II) complexes. The molecular structure of the Schiff base was experimentally determined using X-ray single-crystal data and was compared to the structure predicted by theoretical calculations using density functional theory (DFT), Hartree-Fock (HF) and Möller–Plesset second-order perturbation (MP2). In addition, nonlinear optical (NLO) effects of the compound was predicted using DFT. The antimicrobial activities of the compounds were investigated for their minimum inhibitory concentration. UV–Vis spectroscopy studies of the interactions between the compounds and calf thymus DNA (CT-DNA) showed that the compounds interacts with CT-DNA via intercalative binding. A DNA cleavage study showed that the Cu(II) complex cleaved DNA without any external agents. The compounds inhibited the base pair mutation in the absence of S9 with high inhibition rate. In addition, in vitro cytotoxicity of the Ni(II) complex towards HepG2 cell line was assayed by the MTT method. Also, the colorimetric response of the Schiff base in DMSO to the addition of equivalent amount of anions (F−, Br−, I−, CN−, SCN−, ClO4−, HSO4−, AcO−, H2PO4−, N3− and OH−) was investigated. In this regard, while the addition of F−, CN−, AcO− and OH− anions into the solution containing Schiff base resulted in a significant color change, the addition of Br−, I−, SCN−, ClO4−, HSO4−, H2PO4− and N3− anions resulted in no color change. The most discernable color change in the Schiff base was caused by CN−, which demonstrated that the ligand can be used to selectively detect CN−.

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