Sl. Mecklenburg et al., SPECTROSCOPIC STUDY OF ELECTRON-TRANSFER IN A TRIFUNCTIONAL LYSINE WITH ANTHRAQUINONE AS THE ELECTRON-ACCEPTOR, Inorganic chemistry, 33(13), 1994, pp. 2974-2983
The transient properties of the redox-active amino acid dyads [Anq-Lys
(RuIIb2m)2+-OCH3](PF6)2 and [Boc-Lys-(RuIIb2m)2+-NH-prPTZ](PF6)2 and t
he trifunctionalized amino acid [Anq-Lys(RuIIb2m)2+-NH-prPTZ](PF6)2, w
here Anq is 9, 10-anthraquinone-2-carbonyl, Lys is L-lysine, b is 2,2'
-bipyridine, m is 4'-methyl-2,2'-bipyridine-4-carbonyl, and prPTZ is 3
-(10H-phenothiazine-10)propyl, were examined in CH3CN after nanosecond
laser excitation. This series of redox-active assemblies was prepared
by attaching derivatives of the ruthenium tris(bipyridyl) chromophore
, the electron donor phenothiazine, and/or the electron acceptor anthr
aquinone to L-lysine with amide bonds. Emission from the chromophore w
as efficiently quenched (>95%) by the attached donors or acceptors in
all three cases. Irradiation of [Anq-Lys(RuIIb2m)2+-NH-prPTZ] with 420
-nm, 4-ns laser pulses resulted in net electron transfer from prPTZ to
Anq, mediated by the metal-to-ligand charge-transfer (MLCT) excited s
tate of the ruthenium chromophore, as observed by nanosecond transient
absorption and time-resolved resonance Raman spectroscopies. The resu
lting redox-separated state, [(Anq.-)-Lys(RuIIb2m)2+-NH-(prPTZ.+)], at
1.54 eV, was formed with a quantum efficiency of 26% at its maximum a
ppearance and persisted for 174 ns in CH3CN at 25-degrees-C.