Tuned structure and DNA binding properties of metal complexes base on a new 4-acylpyrazolone derivative
It is a common knowledge that the spatial structure of substrates is the major influencing factor for DNA binding. To tune the binding affinity of DNA, three complexes based on a new 4-acylpyrazolone derivative ligand, (2-hydroxy-N'-((5-hydroxy-3-methyl-1-(4-nitrophenyl)-4,5-dihydro-1H-pyrazol-4-yl)(phenyl)methylene)benzohydrazide) (H2L), has been prepared and well characteristized. Reaction of H2L with CuCl2 resulted a mononuclear compound with tetra-coordinated quadrilateral plane, [Cu(HL)Cl] (1). When H2L was coordinated to Cu(OAc)2, a dinuclear Cu(II) compound with chemical formula of [Cu2L2(CH3OH)2]∙CH3OH (2) was obtained and the coordination geometry of Cu(II) is a square pyramid. Upon assembled H2L with Mn(OAc)2, a quite different dinuclear compound with chemical compisition of [Mn2L2(CH3OH)2(H2O)2]∙CH3OH (3) were afforded where Mn(III) displayed distorted octahedron configurations. DNA binding studies were performed on H2L and its three complexes by electron absorption titration and EB-DNA competition experiments, and the results indicat they all bind DNA in an intercalation mode and their binding affinity follows 1 > 2 > 3 > H2L. In addition, the Time Dependent Density Functional Theory (TD-DFT) calculation were performed for H2L and its three complexes to better clarifies the electronic transitions in the UV-Vis spectra.