Bridging ligand lowest unoccupied molecular orbital

The amide-substituted bipyridine ligand is reduced more easily than the normal bipyridine. Ered separates into two peaks in the dimeric derivatives, 47-2a and 47-2b, and into three in the trimeric 47-3b, whereas the Ru(III/II) redox couple is found as only one peak. This indicates that the LUMO (lowest unoccupied molecular orbital) of the current Ru-complexes is localized on the bipyridine ligands interacting with each other through the amide bridges, without detectable delocalization onto the metal atoms. 

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