Long-range photoinduced through-bond electron transfer and radiative recombination via rigid nonconjugated bridges: distance and solvent dependence
A series of molecules 1 was synthesized containing a 1,4-dimethoxynaphthalene donor (D) an a 1,1-dicyanoethylene acceptor (a) interconnected by five different, rigid, nonconjugated bridges. The length of the bridges varies with increments of two sigma-bonds from four in 1(4) to 12 sigma-bonds in 1(12), to provide donor-acceptor center-to-center separations (R/sub c/) ranging from 7.0-14.9 A. In solvents of medium and high polarity, excitation of the donor D is followed by rapid intramolecular electron transfer. The rate constant (k/sub et/) shows only small dependence upon the solvent polarity (a factor of 2-3 between benzene and acetonitrile, for example) but decreases with increasing separation ranging from >10/sup 11/ s/sup -1/ for a four-bond separation to approx. =4 x 10/sup 8/ s/sup -1/ for a 12-bond separation. In saturated hydrocarbon solvents photoinduced electron transfer is not observed for 10 and 12-bond separations, while it is not significantly decreased for the shorter homologues. Therefore the absence of electron transfer at 10- and 12-bond separations in saturated hydrocarbon solvents is attributed to a thermodynamic rather than to a kinetic effect. In solvents where electron transfer is thermodynamically feasible, its rate is considerably greater than that found from various other experimental studies where either different bridges were used or intermolecular electron transfer was studied. Through-bond interaction involving sigma/..pi.. interaction between the bridge and the donor-acceptor pair is proposed to explain the very high electron transfer rates observed in 1; this is qualitatively correlated with independent information about this coupling derived from both theory and experiment (photoelectron spectroscopy).
- Research Organization:
- Univ. of Amsterdam, Netherlands
- OSTI ID:
- 6365834
- Journal Information:
- J. Am. Chem. Soc.; (United States), Vol. 109:11
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ACETATES
SOLVENT PROPERTIES
ACETONITRILE
ALKENES
CHEMICAL PREPARATION
MOLECULAR STRUCTURE
PHOTOCHEMICAL REACTIONS
BENZENE
CYCLOHEXANE
ETHERS
NAPHTHALENE
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
TETRAHYDROFURAN
ABSORPTION SPECTROSCOPY
ACTIVATION ENERGY
CHEMICAL REACTION KINETICS
ELECTRON TRANSFER
EMISSION SPECTROSCOPY
EXCITED STATES
EXPERIMENTAL DATA
ORGANIC SOLVENTS
PHOTOCHEMISTRY
PHOTOELECTRON SPECTROSCOPY
THERMODYNAMICS
ALKANES
AROMATICS
CARBOXYLIC ACID SALTS
CHEMICAL REACTIONS
CHEMISTRY
CONDENSED AROMATICS
CYCLOALKANES
DATA
ELECTRON SPECTROSCOPY
ENERGY
ENERGY LEVELS
FURANS
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
INFORMATION
KINETICS
NITRILES
NUMERICAL DATA
ORGANIC COMPOUNDS
REACTION KINETICS
SOLVENTS
SPECTROSCOPY
SYNTHESIS
400500* - Photochemistry