Density functional study on the structural and electronic properties of fullerene-barbituric acid and its dimmer

Abstract

Geometric and electronic properties of fullerene-barbituric acid and its dimmer have been studied using density functional theory (DFT) at BLYP level with DNP basis sets. The calculation results indicate that the only one stable geometry of the fullerene-barbituric acid is that with ［6,6］ close-bond structure, and the effects of the barbituric acid on the cage structure is mainly in the local region neighboring the barbituric acid. Among the three isomers of the fullerene-barbituric acid dimmers, one can come to the conclusion both from the energy gap and from relative energy that the ［6,6］—［6,6］ structure is the most stable one. With respect to the electronic structures, the donor-acceptor system corresponds to C60 fullerene-barbituric acid, ie. electron transfers from the fullerene cage to the barbituric acid. The frontier orbitals and spin population show that C60 fullerene-barbituric acid has similar electromagnetic properties of C60, but its stability is reduced, so that the addition reaction would easily take place to form its dimmer. For the C60 fullerene-barbituric acid dimmer, the Mulliken analysis shows there are 0104e and 0106e charge transfers to the four carbons from their neighboring carbons, and the farther the atoms is, the less charge it loses. Compared with those of the C60 fullerene-barbituric acid, the energy gap is changed from 152eV to 1.45eV, while the distribution of highest occupied molecular orbital (HOMO) is little changed but that of lowest unoccupied molecular orbital (LUMO) is changed a lot.