Syntheses, structure, DNA docking and antimicrobial studies of copper(II) complexes with diethylenetriamine and N-bidentate ligands

A series of mononuclear heteroleptic copper(II) complexes with diethylenetriamine (DETA) and bidentate N-donor ligands, [Cu(DETA)(5,6-DMPhen)](ClO4)2 1, [Cu(DETA)(4,7-DMPhen)](ClO4)2, 2, [Cu(DETA)(3,4,7,8-TMPhen)](BPh4)2, 3, [Cu(DETA)(8-AQ)](ClO4)2, 4, [Cu(DETA)(2-AMP)](ClO4)2, 5, [Cu(DETA)(2-AEP)](ClO4)2, 6, [Cu(DETA)(1,2-DACH)](ClO4)2, 7 and [Cu(DETA)(1,3-DAP)](ClO4)2, 8, with biologically relevant N-donor ligands 5,6-dimethyl-1,10-phenanthroline (5,6-DMPhen), 4,7-dimethyl-1,10-phenanthroline (4,7-DMPhen), 3,4,7,8-tetramethyl-1,10-phenanthroline (3,4,7,8-TMPhen), 8-aminoquinoline (8-AQ), 2-aminomethylpyridine (2-AMP), 2-aminoethylpyridine (2-AEP), 1,2-diaminocyclohexane (1,2-DACH) and 1,3-diaminopropane (DAP) respectively. All the complexes (1–8) were structurally determined by a single-crystal X-ray diffraction technique and characterized by CHN, UV–Vis, FT-IR, and ESI-MS. X-ray analysis revealed that the geometry around the copper center in all complexes (1–8) is distorted trigonal bipyramidal. All complexes strongly bind with ct-DNA via groove/electrostatic interactions. Their binding with DNA was supported by UV–Vis and CD spectral studies. Docking studies revealed that copper(II) complexes containing aromatic N-donor ligands (5,6-DMPhen, 4,7-DMPhen, 3,4,7,8-TMPhen & 8-AQ) have a stronger binding affinity than complexes with aliphatic N-donor ligands (2-AMP, 2-AEP, 1,2-DACH & DAP) towards DNA. All complexes exhibited good antibacterial activity against American standard ATCC Escherichia coli (ATCC 25922) and clinically isolated Escherichia coli (E1) bacterial strains.