Charge separation in carotenoporphyin-quinone triads: synthetic, conformational, and fluorescence lifetime studies

Conference · Tue Feb 03 23:00:00 EST 1987 · J. Am. Chem. Soc.; (United States)

OSTI ID:6870834

Gust, D; Moore, T A; Liddell, P A; Nemeth, G A; Makings, L R; Moore, A L; Barrett, D; Pessiki, P J; Bensasson, R V; Rougee, M; Chachaty, C

Carotenoid-porphyrin-quinone triad molecules undergo a photodriven two-step electron-transfer reaction which results in the generation of a high-energy charge-separated state with a lifetime on the microsecond time scale at ambient temperatures in fluid solution. These systems mimic the initial charge separation steps of photosynthesis. A series of these tripartite molecules which differ systematically in the nature of the linkages joining the porphyrin to the quinone and carotenoid moieties has been synthesized in order to investigate the effect of structure on the yield and lifetime of the charge-separated state. The time-averaged solution conformations of these molecules have been determined from porphyrin ring current induced shifts in the /sup 1/H NMR resonances of the carotenoid and quinone moieties. Studies of the triads and related molecules in dichloromethane solution using time-correlated single photon counting fluorescence lifetime techniques have yielded the rate constant for the first of the photoinitiated electron-transfer steps as a function of the linkage joining the porphyrin and the quinone. The rate constants range from 1.5 x 10/sup 8/ to 9.7 x 10/sup 9/ s/sup -1/. For most members of the series, the results are consistent with an exponential dependence of the electron-transfer rate on the experimentally determined donor-acceptor separation, with the exponential factor ..cap alpha.. = 0.6 A/sup -1/.

• Research Organization: Arizona State Univ., Tempe
• OSTI ID: 6870834
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:3; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505 -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
500500* -- Environment
Atmospheric-- Site Resource & Use Studies-- (-1989)
54 ENVIRONMENTAL SCIENCES
ABSORPTION SPECTROSCOPY
AROMATICS
BENZOQUINONES
CARBOXYLIC ACIDS
CAROTENOIDS
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMICAL SHIFT
CHEMISTRY
CONFORMATIONAL CHANGES
DATA
ELECTRON TRANSFER
EXPERIMENTAL DATA
FLUORESCENCE
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
INFORMATION
KINETICS
LIFETIME
LUMINESCENCE
MAGNETIC RESONANCE
NUCLEAR MAGNETIC RESONANCE
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOCHEMISTRY
PIGMENTS
PORPHYRINS
QUINONES
REACTION KINETICS
RESONANCE
SPECTROSCOPY
SYNTHESIS
TERPENES