title: A New Electron-Transfer Donor for Photoinduced Electron Transfer in Polypyridyl Molecular Assemblies.
abstract: A synthetic procedure has been devised for the preparation of the reductive quencher ligand 4-methyl-4'-(N-methyl-p-tolylaminomethyl)-2,2'-bipyridine (dmb-tol), which contains toluidine covalently bound to 2,2'-bipyridine. When bound to Re(I) in [Re(I)(dmb-tol)(CO)(3)Cl], laser flash Re(I) --> dmb metal-to-ligand charge-transfer (MLCT) excitation at 355 nm in CH(3)CN at 298 +/- 2 K is followed by efficient, rapid (<5 ns) appearance of a transient with an absorption feature at 470 nm. The transient spectrum is consistent with formation of the redox-separated state, [Re(I)(dmb(-)-tol(+))(CO)(3)Cl], which returns to the ground state by back electron transfer with k(ET) = (1.05 +/- 0.01) x 10(7) s(-)(1) (tau = 95 +/- 1 ns) at 298 +/- 2 K. Rapid, efficient quenching is also observed in the Ru(II) complex [Ru(4,4'-(C(O)NEt(2))(2)bpy)(2)(dmb-tol)](2+). Based on transient absorption measurements, a rapid equilibrium appears to exist between the initial metal-to-ligand charge-transfer excited state and the redox-separated state, which lies at higher energy. Decay to the ground state is dominated by back electron transfer within the redox-separated state which occurs with k > 4 x 10(8) s(-)(1) at 298 +/- 2 K.
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill, CB# 3290, Chapel Hill, North Carolina 27599-3290.
authors.forename: Colleen M.
authors.initials: CM
authors.lastname: Partigianoni
authors.forename: Sandrine
authors.initials: S
authors.lastname: Chodorowski-Kimmes
authors.forename: Joseph A.
authors.initials: JA
authors.lastname: Treadway
authors.forename: Durwin
authors.initials: D
authors.lastname: Striplin
authors.forename: Scott A.
authors.initials: SA
authors.lastname: Trammell
authors.forename: Thomas J.
authors.initials: TJ
authors.lastname: Meyer