Evaluation of the potential effectiveness of ruthenium(II) complexes with 2,3-disubtituted pyrazino[2,3-f][1,10]phenanthroline anchors, R2ppl (R = CN, COOH, COOEt, OH) as sensitizers for solar cells

The ligands of type pyrazino[2,3-f][1,10]phenanthroline, R2ppl, with R=CN, COOH, COOEt or OH, were synthesized and used as precursors for obtaining the corresponding series of complexes of type [Ru(dmbpy)2R2ppl](PF6)2, where dmbpy is 4,4′-dimethyl-2,2′-bipyridine. The compounds were prepared, characterized, and studied by theoretical DFT calculations in order to evaluate their potentiality as dyes in photoelectrochemical cells.The electron acceptor capacity of the R2ppl ligands was evaluated by analyzing parameters such as electrophilicity and charge distribution on the reduced ligand. Additionally, the R substituents on R2ppl were evaluated as anchoring groups, by variables such as highest spin occupied molecular orbital (HSOMO). Finally, the IT parameter was defined and calculated. This is related to the amount of energy that can be delivered to TiO2 from the acceptor anchoring ligand in the thexi state. According to this parameter, the [Ru(dmbpy)2(COOH)2ppl](PF6)2 complex is predicted to have the best response, among the compounds of the series, when used as dye in a solar cell.