Synthesis, photophysical and preliminary investigation of the dye-sensitized solar cells properties of functionalized anthracenyl-based bipyridyl and phenanthrolyl Ru(II) complexes

Four new amphiphilic ligands: 4-(2,3-dimethylacrylic acid)-2,2′-bipyridine (L1), 4-(9-anthracenyl-10-(2,3-dimethylacrylic acid)-2,2′-bipyridine (L2), 5-(2,3-dimethylacrylic acid)-1,10-phenanthroline (L3) and 5-(9-anthracenyl-10-(2,3-dimethylacrylic acid)-1,10-phenanthroline (L4), with their corresponding homonuclear ruthenium(II) complexes formulated as cis-[Ru-(L1)3(PF6)2] (C1), cis-[Ru-(L2)3(PF6)2] (C2), cis-[Ru-(L3)3(PF6)2] (C3) and cis-[Ru-(L4)3(PF6)2] (C4), have been synthesized and characterized by elemental analysis, 1H- and 13C- NMR, FT-IR, UV-Vis and photoluminescence spectroscopy. The complexes exhibit broad and intense metal-to-ligand charge transfer (MLCT) transition bands in the visible region (400–700 nm), and red light emitting properties at room temperature. By comparison however, complexes C1 and C2 bipyridine moiety gave lower molar absorptivity coefficient at relatively similar wavelength characteristics (410–520 nm) when compared to C3 and C4 with phenanthroline based molecules. Cyclic voltammograms of the complexes revealed complex C4 with most reduction potential which might be due to increase in the conjugation of the anthracene functionalized units. Preliminary investigation of the solar cell efficiency of the complexes on TiO2 nanocrystalline films gave the best result with efficiency of 0.103% for C1 under illumination at 1000 W/m2 AM 1.5. Electrochemical impedance spectroscopy (EIS) technique however, revealed the charge transfer resistances (Rct) of the electrons on the TiO2 semiconductor.