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

Abstract

New heteroleptic ruthenium(II) complex was formulated as [Ru(L ₁) ₂(NCS) ₂], where L ₁= 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(L ₂) ₂(NCS) ₂], L ₂= (2-methyl-2-butenoic acid)-1,10-phenanthroline. The two complexes though exhibit very strong molar extinction coefficient values; however, [Ru(L ₁) ₂(NCS) ₂] shows better characteristic broad and intense metal-to-ligand charge transfer (MLCT) absorption band and higher molar absorptivity coefficient at ( ${\lambda }_{\text{m}\text{a}\text{x}}=522$ nm, $\epsilon =6.60\times {10}^4$ M ⁻¹ cm ⁻¹) than that of [Ru(L ₂) ₂(NCS) ₂] complex, ( ${\lambda }_{\text{m}\text{a}\text{x}}=446$ nm, $\epsilon =4.82\times {10}^4$ M ⁻¹ cm ⁻¹). At room temperature, long wavelength emissions with strong intensity ratio centered at 660 nm were recorded for [Ru(L ₁) ₂(NCS) ₂] complex with a bathochromic shift ( ${\lambda }_{\text{e}\text{m}}=700$ nm) for [Ru(L ₂) 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(L ₁) 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.