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Abstract:
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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][PF6]4 , undergoes multiple photoreductions in the presence of donors such as triethylamine (TEA ) ; however , large amount of donors (0 .3 M ) are required for efficient reductions . This 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 donor . Electrochemical data reveals that [B (cat )2] - is oxidized irreversibly which suggests its application as a sacrificial donor . Stern - Volmer quenching of [B (cat )2] - with [Ru (bpy )3]2+ and photochemistry with complex P conducted to examine its usefulness for this application .
Replacement of the bridging ligand of photoactive Ru complex P4+ (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 coworkers34 . 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+ /P2+ = -0 .513 vs NHE ) . Thus , the
species are more reductive which could be used in another application such as photosplitting
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