Abstract:

The geometries, electronic absorption spectra and charge transfer properties of five novel star-shaped compounds with different core(electron-rich core: nitrogen, triazatruxene and triindole; electron-deficient core: 1,3,5-triazine and triquinoxaline), styrene as bridge and tetrathiafulvalene(TTF) as a terminal group, were studied with density functional theory(DFT) method. The results show that LUMO levels and energy gaps can be adjusted effectively via altering the cores. The time-dependent DFT calculation indicates that there are two absorption bands in 300-450 nm. The results of the transition density matrix and charge difference density reveal that high energy excitation mainly arises from charge transfer from TTF donor moiety to core and bridge moiety. The low-lying excitations in electron-deficient core compounds are predominantly TTF donor-bridge and core charge transfer transition from two intra-branch. This differs from electron-rich compounds, whose low-energy transitions are assigned to prominently intra-branch localized excitation from TTF moiety. The reorganization calculations show that the hole and electronic reorganization energy are nearly equal except NST, and CST shows the lowest reorganization energy.

Key words: Star-shaped molecule, Tetrathiafulvalene, Core, Charge transfer, Density functional theory