Three mixed ligand copper(II) complexes [Cu(o-vanillin-L-tryptophan Schiff base) (diimine)] (diimine =2,2′-bipyridine (1), 1,10-phenanthroline (2) and 5,6dimethyl-1,10-phenanthroline(3)) were synthesized and characterized using analytical and spectral methods. The molecular structures of 1-3 were optimized using density functional theory (DFT) at B3LYP/LanL2DZ levels in the gas phase. Spectral and DFT studies suggest a distorted square pyramidal geometry around the copper ion. Binding interactions of 1-3 with calf thymus DNA and bovine serum albumin protein were studied using UV-visible and fluorescence spectroscopies, viscometric titrations and cyclic voltammetry and also using molecular docking analysis. Studies of the binding of the complexes with calf thymus DNA reveal intercalation, which is supported by molecular docking simulation. The DNA cleavage nature of 1-3 with pUC19 DNA shows that the complexes can cleave DNA without any external agents, and the efficiency follows the order 1 > 3 > 2. Synchronous and three-dimensional fluorescence spectral studies suggest that the secondary structures of the protein are altered by the complexes. Antioxidant studies reveal that the complexes have significant radical scavenging activity against DPPH. In vitro cytotoxic activity of the complexes was evaluated against breast cancer cells (MCF-7), revealing that complex 2 exhibits higher cytotoxicity than the other complexes. Nuclear chromatin condensation and fragmentation were observed with DAPI staining assay. The mitochondrial membrane potential damage was studied by FITC staining assay. Flow cytometric analysis suggests that all the metal complexes induce cell apoptosis.

Cu(II), Ni(II) and Zn(II) complexes of (E)-2-((2,4-dihydroxybenzylidene) amino)-3-(1H-indol-3-yl)propanoic acid Schiff base (L) were synthesized and characterized by various spectral methods. ESI-MS was used to confirm the structure of synthesized compounds. Molecular geometries of the complexes were predicted by optimizing the structure by DFT/B3LYP method with LANL2DZ basis set in the gas phase. The interaction of the metal complexes with CT-DNA and BSA protein has been examined by UV-vis, fluorescence and viscometer titrations reveal that the complexes bind to DNA through intercalation binding mode. The copper complexes exhibit effective cleavage of pUC19 DNA by the oxidative mechanism. The synthesized compounds screened for their antibacterial activities against various bacteria strains exhibit the L and copper complex show potential activity against Pseudomonas aeruginosa and Escherichia coli, respectively. Subsequently, molecular docking studies were performed on to understand the binding of the compounds with DNA, BSA and bacteria. KEYWORDS amino acid Schiff base, antibacterial activity, DFT calculations, DNA binding and cleaving, metal complexes

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