Synthesis of heteroleptic Ru(II) complexes ligated with 1,3-dihydro-1,1,3,3-tetramethyl-7,8-diazacyclopenta[1]phenanthren-2-one and application in dye-sensitized solar cells

Four heteroleptic ruthenium(II) complexes, HJ1–HJ4 [Ru(L)(DTDP)(NCS)2][TBA], (where DTDP = 1,3-dihydro-1,1,3,3-tetramethyl-7,8-diazacyclopenta[1]phenanthren-2-one, L = 4,4′-dicarboxy-2,2′-bipyridine (dcbpy, HJ1), 4,4′-bis(E-carboxyvinyl)-2,2′-bipyridine (dcvbpy, HJ2), 4,7-dicarboxy-1,10-phenanthroline (dcphen, HJ3), or 4,7-bis(E-carboxyvinyl)-1,10-phenanthroline (dcvphen, HJ4)), were synthesized from one-pot reaction of [RuCl2(p-cymene)]2 and DTDP ligand followed by addition of the second ligand (L = dcbpy, dcvbpy, dcphen, or dcvphen). Final products were obtained as tetrabutylammonium salt form of ruthenium(II) complexes with reasonable yields. We demonstrated that a dye-sensitized solar cell (DSSC) fabricated with HJ1 dye exhibited a conversion efficiency (η) of 2.8%, which is close to that of standard N719 dye, while other cells fabricated with HJ2–HJ4 dye had conversion efficiencies (η) of between 1.2 and 2.0%.