Electronic structure and UV absorption spectra of metal-mediate DNA: an approach from theoretical chemistry.

We theoretically evaluated the stability, UV-Vis spectra and possibility of stacking of [S-M(II)-S] (M=Ni, Pd, Pt, S: hydroxypyridonethione) by means of the density functional theory (DFT). From the view of the free energy, we assessed formation energy of possible combinations of chalcogen atoms and metal cations. The results confirmed that [H-Ni(II)-H] and [S-Cu(II)-S] would form stable metal-base pairing, on the other hand [H-Pt(II)-H] would not, which have been experimentally proven. Moreover, by use of time-dependent density functional theory (TDDFT), we observed d-pi* transition accompanied with pi-pi* transition in [S-M(II)-S]. These results reveal that metal-to-ligand charge transfer (MLCT) shifts the peak of pi-pi* transition in [S-2H(+)-S] (without metal cations).