A High Molar Extinction Coefficient Ru(II) Complex Functionalized with cis-Dithiocyanato-bis-(9-anthracenyl-10-(2-methyl-2-butenoic acid)-1,10-phenanthroline): Potential Sensitizer for Stable Dye-Sensitized Solar Cells

New heteroleptic ruthenium(II) complex was formulated as [Ru(L1)2(NCS)2], where L1 = 9-anthracenyl-10-(2-methyl-2-butenoic acid)-1,10-phenanthroline was synthesized and its photophysical properties were studied and compared to previously reported analogue complex containing no anthracene moiety [Ru(L2)2(NCS)2], L2 = (2-methyl-2-butenoic acid)-1,10-phenanthroline. The two complexes though exhibit very strong molar extinction coefficient values; however, [Ru(L1)2(NCS)2] shows better characteristic broad and intense metal-to-ligand charge transfer (MLCT) absorption band and higher molar absorptivity coefficient at (λmax=522 nm, ε=6.60×104 M−1 cm−1) than that of [Ru(L2)2(NCS)2] complex, (λmax=446 nm, ε=4.82×104 M−1 cm−1). At room temperature, long wavelength emissions with strong intensity ratio centered at 660 nm were recorded for [Ru(L1)2(NCS)2] complex with a bathochromic shift (λem=700 nm) for [Ru(L2)2(NCS)2] complex. It was shown that the luminescence wavelength characteristic of the complexes may be a function relating to the increasing length of π-conjugation and/or molecular weight. A preliminary cyclic voltammetry of [Ru(L1)2(NCS)2] complex also exhibits good electroredox activity with oxidation potential of about 1.04 V, significantly better than other Ru(II) polypyridine complexes containing bidentate ligands