Characterization, Crystal Structure and Initial DNA Binding Mechanism Research of Multi-nuclear Homometallic Complexes of 4,5-Diazafluoren-9-one with Copper(II) and Cobalt(II)

Two new multi-nuclear homometallic complexes, [Cu2(OAc)4(H2O)2]·2dafo (1) and [(µ2-O)2-Co3(dafo)6]-(ClO3)2·H2O (2) (dafo=4,5-diazafluoren-9-one), were synthesized. The two complexes have been fully characterized by elemental analysis, IR, absorption spectra, emission spectra, and single-crystal X-ray diffraction analysis. The initial DNA binding mechanisms of the two complexes have been investigated by absorption spectra, emission spectra and cyclic voltammograms. Both complexes show similar perturbations on addition of calf thymus DNA in the UV region, their luminescence intensities in aqueous buffer are all enhanced in the presence of increasing amounts of DNA, and their electrochemical behavior is both completely different in the absence and presence of DNA. The results of the three methods indicate that the spectral characters and the electrochemical behavior of the two complexes are very similar to those of the known metallointercalators. So it can be concluded that the action mode of the two complexes with DNA is mainly intercalative.