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 containing 1,3-dihydro-1,1,3,3-tetramethyl-7,8-diazacyclopenta[1]phenanthren-2-one ligand (DTDP) were synthesized.•One-pot reaction of [RuCl2(p-cymene)]2 and DTDP ligand followed by addition of the second ligand (L=dcbpy, dcvbpy, dcphen, or dcvphen) was applied.•Final products were obtained as tetrabutylammonium salt form of ruthenium(II) complexes with reasonable yields.•Dye-sensitized solar cell (DSSC) fabricated with them exhibited reasonable conversion efficiency (η) of between 1.2 and 2.8%.