title: Steric effect for proton, hydrogen-atom, and hydride transfer reactions with geometric isomers of NADH-model ruthenium complexes.
abstract: Two isomers, [Ru(1)]2+ (Ru = Ru(bpy)2, bpy = 2,2'-bipyridine, 1 = 2-(pyrid-2'-yl)-1-azaacridine) and [Ru(2)]2+ (2 = 3-(pyrid-2'-yl)-4-azaacridine), are bioinspired model compounds containing the nicotinamide functionality and can serve as precursors for the photogeneration of C-H hydrides for studying reactions pertinent to the photochemical reduction of metal-C1 complexes and/or carbon dioxide. While it has been shown that the structural differences between the azaacridine ligands of [Ru(1)]2+ and [Ru(2)]2+ have a significant effect on the mechanism of formation of the hydride donors, [Ru(1HH)]2+ and [Ru(2HH)]2+, in aqueous solution, we describe the steric implications for proton, net-hydrogen-atom and net-hydride transfer reactions in this work. Protonation of [Ru(2*-)] in aprotic and even protic media is slow compared to that of [Ru(1*-)]+. The net hydrogen-atom transfer between *[Ru(1)]2+ and hydroquinone (H2Q) proceeds by one-step EPT, rather than stepwise electron-proton transfer. Such a reaction was not observed for *[Ru(2)]2+ because the non-coordinated N atom is not easily available for an interaction with H2Q. Finally, the rate of the net hydride ion transfer from [Ru(1HH)]2+ to [Ph3C]+ is significantly slower than that of [Ru (2HH)]2+ owing to steric congestion at the donor site.
authors.affiliation: Chemistry Department, Brookhaven National Laboratory, Upton, New York, 11973-5000, USA.
authors.forename: Brian W
authors.initials: BW
authors.lastname: Cohen
authors.forename: Dmitry E
authors.initials: DE
authors.lastname: Polyansky
authors.forename: Patrick
authors.initials: P
authors.lastname: Achord
authors.forename: Diane
authors.initials: D
authors.lastname: Cabelli
authors.forename: James T
authors.initials: JT
authors.lastname: Muckerman
authors.forename: Koji
authors.initials: K
authors.lastname: Tanaka
authors.forename: Randolph P
authors.initials: RP
authors.lastname: Thummel
authors.forename: Ruifa
authors.initials: R
authors.lastname: Zong
authors.forename: Etsuko
authors.initials: E
authors.lastname: Fujita
mesh_terms: D015082:2,2'-Dipyridyl / Q000737:chemistry; D000166:Acridines / Q000737:chemistry; D056831:Coordination Complexes / Q000737:chemistry; D004579:Electron Transport; D006859:Hydrogen / Q000737:chemistry*; D006873:Hydroquinones / Q000737:chemistry; D008958:Models, Molecular; D009243:NAD / Q000737:chemistry* / Q000378:metabolism; D009584:Nitrogen / Q000737:chemistry; D010777:Photochemistry; D011522:Protons; D012428:Ruthenium / Q000737:chemistry*; D014867:Water / Q000737:chemistry* / Q000378:metabolism
chemical_list: D000166:Acridines; D056831:Coordination Complexes; D006873:Hydroquinones; D011522:Protons; D014867:Water; D009243:NAD; D015082:2,2'-Dipyridyl; D012428:Ruthenium; D006859:Hydrogen; D009584:Nitrogen; C031927:hydroquinone