Excited-State Electron Transfer in a Chromophore-Quencher Complex. Spectroscopic Identification of a Redox-Separated State.
In the chromophore-quencher complex fac-[Re(Aqphen)(CO)(3)(py-PTZ)](+) (Aqphen is 12,17-dihydronaphtho[2,3-h]dipyrido[3,2-a:2',3'-c]-phenazine-12,17-dione; py-PTZ is 10-(4-picolyl)phenothiazine), Aqphen is a dppz derivative, containing a pendant quinone acceptor at the terminus of a rigid ligand framework. This introduces a third, low-lying, ligand-based pi acceptor level localized largely on the quinone fragment. Laser flash excitation of fac-[Re(Aqphen)(CO)(3)(py-PTZ)](+) (354.7 nm; in 1,2-dichloroethane) results in the appearance of a relatively long-lived transient that decays with tau(298K) = 300 ns (k = 3.3 x 10(6) s(-)(1)). Application of transient absorption, time-resolved resonance Raman, and time-resolved infrared spectroscopies proves that this transient is the redox-separated state fac-[Re(I)(Aqphen(*)(-)())(CO)(3)(py-PTZ(*)(+)())](+) in which the excited electron is localized largely on the quinone portion of the Aqphen ligand.
López
Rosa
R
Department of Chemistry, CB#3290, University of North Carolina, Chapel Hill, North Carolina 27599-3290.
Leiva
Ana M.
AM
Zuloaga
Fernando
F
Loeb
Bárbara
B
Norambuena
Ester
E
Omberg
Kristin M.
KM
Schoonover
Jon R.
JR
Striplin
Durwin
D
Devenney
Martin
M
Meyer
Thomas J.
TJ