DFT investigation of the intermolecular interactions of a thieno-separated tricyclic guanine analog with gold nanoclusters

摘要

The interactions between a thieno-separated tricyclic guanine analog (ttG) and gold nanoclusters Au. _n (n=2, 4, 6, and 8) were studied theoretically at the DFT level. Geometries of neutral complexes were optimized using the B3LYP functional with the 6-31+G(d,p) basis set for ttG and the LANL2DZ basis set for gold clusters. The binding modes, interacting strength, and the charge transfer properties of different Au. _n-ttG complexes were investigated. Natural population analysis was performed for NBO charges. It was found that gold nanoclusters form stable complexes with ttG and the complexation results in a substantial amount of electronic charge being transferred from ttG to the gold clusters. Furthermore, binding of Au. _n is the most strong at N3 site, followed by the N7 site, and the binding at O6 site is relatively weaker. In addition, binding of Au. _n at N3 site will increase the planarity of ttG moiety. The vertical first ionization potential, electron affinity, fermi level, and the HOMO-LUMO gap of ttG and Au. _n-ttG complexes were also analyzed.