Saturday, 7 October 2006 - 9:05 AM
South Ballroom (Binghamton Regency Hotel and Conference Center)
497
Photochemical Production of a Functionalized Polypyridylruthenium Hydride Donor
NAD+/NADH is one of the most important redox mediators in biological systems and acts as a reservoir/source of two electrons and a proton. We prepared a polypyridylruthenium complex with an NAD+/NADH model ligand, [Ru(bpy)2(pbn)](PF6)2 (bpy = 2,2L-bipyridine, pbn = 2-(2-pyridyl)-benzo[b]-1,5-naphthyridine), the structure of which is shown in the figure. [Ru(bpy)2(pbn)](PF6)2 catalyzes the reduction of acetone to isopropanol when a potential of -1.14 V vs a Fc/Fc+ couple is applied to an aqueous acetone solution.1 While many stoichiometric reactions involving NADH models have been reported, this is the first example of the electrochemical catalytic reduction of organic molecules by NADH model complexes. When acetonitrile solutions containing [Ru(bpy)2(pbn)](PF6)2 and triethylamine are irradiated with visible light (< 590 nm), [Ru(bpy)2(pbnH2)](PF6)2 is produced cleanly (F355nm = 0.21). The photochemical and electrochemical properties including the acid-base properties of the ground state, excited state and one-electron-reduced species of [Ru(bpy)2(pbn)](PF6)2s will be presented together with the kinetic and mechanistic investigation of the [Ru(bpy)2(pbnH2)](PF6)2 formation using pulse radiolysis. These experimental results are consistent with DFT calculations of the energetics and UV-vis spectra of the species involved in the proposed mechanism. The research carried out at Brookhaven National Laboratory was supported under contract DE-AC02-98CH10886 with the U.S. Department of Energy. 
1 Koizumi, T.; Tanaka, K. Angew. Chem. Int. Ed. 2005, 44, 5891
Figure 1 ORTEP view of the cation
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