| Ruthenium polypyridyl complexes [Ru(L-L)3]2+, (L-L = 1,10-phenanthroline or 2,2'-bipyridine) which covalently linked to electron donor or acceptor units are frequently used in artificial photosystems because of their high emission quantum yields, long excited-state lifetimes, favorable redox properties and excellent chemical stability. The ruthenium dimer P, [(phen)2Ru(tatpp)Ru(phen)2][PF 6]4, undergoes multiple photo-reductions in the presence of electron donors such as triethylamine (TEA); however, large amount of donors (0.3 M) are required for efficient reductions. This research explores the use of a anionic donor such as [B(cat)2]- with the hypothesis that ion-pairing will result in lower required concentration of the electron donor. Electrochemical data reveals that [B(cat)2] - is oxidized irreversibly; therefore, it can be used as a sacrificial donor. Stern-Volmer quenching of [Ru(bpy)3]2+ with [B(cat)2]- and the photochemistry of complex P4+ with [B(Cat)2]-1 conducted to examine its usefulness for this application.; Replacement of the bridging ligand of photoactive Ru complex P 4+ (tatpp for 9,11,20,22-Tetraazatetrapyrido[3,2-a: 2', 3'-c:3", 2"- l: 2''', 3'''-n]pentacene) with bdppz (for 1,19-dipyrido[3,2- a:29,39-c]phenazin-1,19-yldipyrido[3,2- a:29,39-c]-phenazine) results in interesting electronic and redox properties. The first and second reduction potentials of the resultant complex ([(phen)2Ru(dppz)-(dppz)Ru(phen)2]4+ , 14+) are reported by De Cola and coworkers. The cyclic voltammetry data revealed two sequential one electron reductions and interestingly both first and second reduction potentials (BD/BD - = -0.683 and BD-/BD2- = -0.873 vs NHE) are more negative than the ruthenium complex P4+ (P4+/P3+ = -0.02 and P3+/P 2+ = -0.513 vs NHE). Thus, the species are more reductive which could be used in another application such as photo-splitting water. |
