Electron-transfer reactions of ruthenium trisbipyridyl-viologen donor-acceptor molecules. Comparison of the distance dependence of electron-transfer rates in the normal and Marcus inverted regions

Journal Article · Wed Jun 01 00:00:00 EDT 1994 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00090a026· OSTI ID:7267160

Yonemoto, E H; Saupe, G B; Hubig, S M; Riley, R L; Iverson, B L; Mallouk, T E ^[1]; Schmehl, R H ^[2]

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1. Univ. of Texas, Austin, TX (United States)
2. Tulane Univ., New Orleans, LA (United States)

The rates of photoinduced forward and thermal back electron transfer (ET) in a series of donor-acceptor molecules (2,2[prime]-bipyridine)[sub 2]Ru(4-CH[sub 3]-2,2[prime]-bipyridine-4[prime]) (CH[sub 2])[sub n](4,4[prime]-bipyridinium-CH[sub 3])[sup 4+] (n = 1-5,7,8) were studied by flash photolysis/transient absorbance techniques. The rate of intramolecular forward ET (MLCT quenching) in acetonitrile varies exponentially with the number of carbon atoms in the spacer chain up to n = 5 and is roughly constant for n = 5, 7, 8, consistent with a predominantly [open quotes]through bond[close quotes] electron transfer pathway for short chains and a [open quotes]through solvent[close quotes] pathway for longer chains. Encapsulation of the spacer chain by [beta]-cyclodextrin molecules slows the rate of forward ET for n = 7, 8, consistent with a [open quotes]through bond[open quotes] ET pathway. The rate of back ET, which occurs in the Marcus inverted region, also varies exponentially with n, but more weakly than the forward ET rates. Apparent [beta] values (defined by k[sub et] = A exp(-[beta]r[sub DA]), where r[sub DA] is the donor-acceptor distance) are 1.38 and 0.66 [angstrom][sup [minus]1] for forward and back ET, respectively. However, correction of k[sub ET] for the distance dependence of the solvent reorganization energy gives similar values (1.0-1.2 [angstrom][sup [minus]1]) of [beta] for the two ET reactions. In this case, [beta] describes the distance dependence of [vert bar]V[vert bar][sup 2] (V = electronic coupling matrix element) rather than that of k[sub ET]. 44 refs., 9 figs., 3 tabs.

• DOE Contract Number: FG05-87ER13789
• OSTI ID: 7267160
• Journal Information: Journal of the American Chemical Society; (United States), Vol. 116:11; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
ELECTRON TRANSFER
CHEMICAL REACTION KINETICS
RUTHENIUM COMPLEXES
PHOTOLYSIS
ACETONITRILE
COMPILED DATA
DEXTRIN
MATHEMATICAL MODELS
NUCLEAR MAGNETIC RESONANCE
PHOTOSYNTHESIS
SPECTROSCOPY
VOLTAMETRY
CARBOHYDRATES
CHEMICAL REACTIONS
COMPLEXES
DATA
DECOMPOSITION
INFORMATION
KINETICS
MAGNETIC RESONANCE
NITRILES
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
POLYSACCHARIDES
REACTION KINETICS
RESONANCE
SACCHARIDES
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
400500* - Photochemistry
400102 - Chemical & Spectral Procedures
990200 - Mathematics & Computers