While organic photochemistry can provide some useful analogues for inorganic photochemistry, many of the typical organic paradigms do not follow leaving much to be discovered.  Exploration of the photophysical properties of various dirhodium paddlewheel complexes with formamidinate bridging ligands yielded unusual and unexpected results.  Further analysis by ultrafast transient absorbance and DFT calculations suggest a new ligand to ligand charge transfer (LLCT) excited state, where the hole and electron are positioned across the metal and are localized on the ligands.  This state was observed in complexes with two formamidinate bridging ligands with two polypyridal ligands, such as [Rh2(form)2(dppz)2]2+ where dppz is dipyrido[3,2-a:2',3'-c]phenazine, [Rh2(form)2(dppn)2]2+ where dppn is benzo<i>dipyrido[3,2-a:2',3'-c]phenazine, and [Rh2(form)2(dpq)2]2+ where dpq is dipyrido-[3,2-d:2',3'-f]-quinoxaline, where the charge transferred from the polypyridal to the formamidinate.  This new state causes a charge separation between two diffent ligands rather than a metal and ligand has many interesting applications.

Ligand to ligand charge transfer observed in dirhodium paddlewheel complexes

244th National Meeting (2012)

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