Theoretical studies of COOH group effect on the performance of rhenium (I) tricarbonyl complexes with bispyridine sulfur-rich core ligand as dyes in DSSC

The series of rhenium (I) tricarbonyl mixed-ligand complexes ReCl(CO)3(Hnbpydt) (n = 2, 1; n = 4, 2; bpy = bispyridine, dt = 1,3-dithiole) and ReCl(CO)3(HnbpyTTF) (n = 2, 3; n = 3, 4; TTF = Tetrathiafulvalene) have been investigated theoretically to explore the effect of COOH functional group on their electronic structures, spectroscopic properties and their properties as dye in a solar cell. The calculated geometry structure and absorption spectrum of 1 and 3 are generally consistent with the experimental results. By attaching the COOH groups on both bpy and dt (TTF in 4) moiety in 2, the nature of LUMO is also contributed by both π*(bpy) and π*(dt) (π*(TTF) in 4), and the absorptions have an obvious red shift compared with 1 and 3. In addition, it can be found that the transition terminates at the orbital populated by the COOH-appended moieties, and the performance of 2 and 4 in the dye-sensitized solar cell can be enhanced as compared with 1 and 3.