Synthesis, Crystal Structures and DNA Interaction of Cu(II), Zn(II), Co(II), and Mn(II) Complexes Derived from Zwitterionic Carboxylate Ligand

摘要

Four new metal complexes, namely [Cu-2(Cbiq)(4)(H2O)(2)]Br-4 center dot 2H(2)O ( 1), [Zn(Cbiq)(2)(H2O)(2)]Br-2 center dot Cbiq center dot H2O (2), and [M-3(Cbiq)(8)(mu-OH)(2)(H2O)(2)](ClO4)(4)center dot 7H(2)O (M=Co ( 3), Mn (4)), were synthesized from the zwitterionic carboxylate ligand N-(4-carboxybenzyl)isoquinolinium bromide ((HCbiq)Br) with the corresponding metal salts. All these metal complexes were characterized by single crystal X-ray diffraction, elemental analyses, and IR. In complex 1, the centrosymmetric binuclear Cu(II) are bridged by four Cbiq molecules and each Cu(II) ion is further coordinated to one water molecule. In complex 2, the center Zn(II) ion is coordinated to two unidentate Cbiq molecules and two water molecules. Complexes 3 and 4 have similar structures in which every two M(II) ions are bridged by two Cbiq molecules and one hydroxo-O atom and the two peripheric M(II) ions are further coordinated to two unidentate Cbiq molecules and one water molecule. Agarose gel electrophoresis (GE) studies on the cleavage of plasmid pBR322 DNA by complexes 1 -4 indicated that complex 1 was capable of efficiently cleaving DNA under physiological conditions, most probably via an oxidative mechanism. Kinetic assay of complex 1 afforded the maximal catalytic rate constant k(max) of 2.80 h(-1) and Michaelis constant K-M of 3.22 mmol center dot L-1. Ethidium bromide (EB) displacement experiments indicated that complex 1 exhibited high DNA binding affinity toward calf-thymus (CT) DNA. The docking method was used to predict the CT DNA binding affinity of complex 1, with the result that the binding free energy was -49.87 kJ center dot mol(-1). CCDC: 2165985, 1; 2165991, 2; 2166081, 3; 2166082, 4.

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