Search

We report the photocatalytic dehydrogenation of alcohols with a Rh catalyst and I− in an acidic medium. The catalyst screening of a structurally diverse family of Rh complexes found [RhIII(dtbbpy)2(OSO2CF3)2](CF3SO3) ( Rh7; dtbbpy=4,4′-di- tert-butyl-2,2′-bipyridine) to be the best catalyst. All components ( Rh7, HI, alcohol, and light) were found to be essential for the dehydrogenation to occur. Under optimal conditions, generation of both H2 and acetone (for isopropyl alcohol) was observed, which increased linearly for 4 days with no significant decrease in activity. The proposed mechanism involves the formation of [RhIII(dtbbpy)2(I)2]+ [ Rh7( a)] followed by the generation of photoinduced I3− via a ligand (I−) to metal (RhIII) charge transfer. The resulting RhI species reduces H+ and I3− oxidizes the alcohol, which completes the catalytic cycle. Supporting evidence for the catalytic mechanism was obtained by using UV/Vis spectroscopy, electrospray ionization mass spectrometry, cyclic voltammetry and time-dependent DFT calculations. [ABSTRACT FROM AUTHOR]