“…8,9 Sensitizers of polypyridyl complexes have the formula ML 2 (X) 2 , where M is the metallic center, such as Re(I), Ru(II) or Os(II), L is related to 4,4 0 -dicarboxy-2,2 0 -bipyridine ligands, and X is usually a thiocyanate (SCN À ) ligand. [10][11][12][13] Among all, ruthenium(II) polypyridyl complexes are known to exhibit extraordinary optical and electronic properties; for example, the black dye, 14 N3, 15 and N719 16 represent the best efficiency. The great interest in these complexes corresponds to their additional and anchoring ligands, which are responsible for the attachment to the semiconductor (typically TiO 2 or ZnO) and absorption of light.…”