Theoretical studies on the related properties of Co(III) polypyridyl complexes interacting with DNA.

Theoretical studies on the related properties of Co(III) polypyridyl complexes [Co(phen)(2)L](3+) (L: dppz = dipyrido[3,2-a:2',3'-c]phenazine; phen = 1,10-phenanthroline; dione = 1,10-phenanthroline-5,6-diketone) 1-3 interacting with DNA, including the DNA-binding, DNA-photocleavage and spectral properties, have been carried out. First, the full geometry-optimizations of these three complexes in their ground states were carried out in aqueous solution. The optimized structures of these three complexes were docked into DNA-base-pairs using the Dock6.0 program. Secondly, the binding modes of complexes 1-3 were revealed in detail and the trend in DNA-binding affinities was reasonably explained. Thirdly, the electronic absorption and emission spectra of docking model of the optimal complex 1 were calculated and simulated. The experimental intense absorption and emission bands of Co(Ш) complex 1 in the presence of DNA were explained in detail, in particular, the reason why the emission spectra of complex 1 in the presence of DNA are greatly stronger than those in the absence of DNA was theoretically elucidated. Finally, the DNA-photocleavage essential of complexes was explored and the DNA photocleavage efficiencies (φ), i.e., φ(1)>φ(2)>φ(3), was also reasonably explained.
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