Zn(II), Cd(II), Mn(II), and Cu(II) complexes based on an imidazole derivative and carboxylic acids: synthesis, crystal structures, and DNA-binding properties

In this investigation, six new metal complexes with 2-(pyridin-2-yl)benzo[d]imidazole (bpm) were synthesized and analyzed by single-crystal X-ray diffraction (XRD), including catena-bis[(µ-2,2-bis(4-carobxyphenyl)hexafluoropropane)-(2-(pyidin-2-yl)-1H-benzimidazole)-aqua-zinc] (1), catena-[(µ-2,2-bis(4-carobxyphenyl)hexafluoropropane)-(2-(pyidin-2-yl)-1H-benzimidazole)-aqua-cadmium] (2), aqua-[2,2-bis(4-carobxyphenyl)hexafluoropropane]-bis[2-(pyridin-2-yl)-1H-benzimidazole]-manganese (3), μ-[2-nitrobenzene-1,4-dicarboxylato]-μ-[2-nitrobenzene-1,4-dicarboxylato]-bis[2-(pyridin-2-yl)-1H-benzimidazole]-di-zinc (4), catena-[bis(µ-2-nitrobenzene-1,4-dicarboxylato)-diaqua-bis(2-(pyridin-2-yl)-1H-benzimidazole)-di-cadmium] (5), aqua-[pyridine-2,6-dicarboxylato]-[2-(pyridin-2-yl)-1H-benzimidazole]-copper hydrate (6) (H2hfipbb = 2,2-bis(4-carboxyphenyl)hexafluoropropane, H2nbdc acid = Nitroterephthalic acid, and H2pda = 2,6-pyridinedicarboxylic acid). Complex 1 crystallized in a monoclinic system with space group P21/n; 2 crystallized in a monoclinic system with space group C2/c; 3 crystallized in an orthorhombic system with space group Pna21; 5 crystallized in a monoclinic system with space group P21/c; 4 and 6 crystallized in triclinic systems with space group P-1. The DNA-binding modes of the complexes were investigated by several analysis methods (e.g. viscosity analysis, circular dichroism spectroscopy, fluorescent spectroscopic analysis, as well as UV spectroscopic analysis). Complexes 1-6 bind to calf thymus DNA via an intercalative mode. The results of this study provide insights into the mechanism of DNA binding and provide a basis for rationally designing new powerful reagents for DNA detection and targeting.