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Titolo:
95-670 GHz EPR studies of canthaxanthin radical cation stabilized on a silica-alumina surface
Autore:
Konovalova, TA; Krzystek, J; Bratt, PJ; van Tol, J; Brunel, LC; Kispert, LD;
Indirizzi:
Univ Alabama, Dept Chem, Tuscaloosa, AL 35487 USA Univ Alabama TuscaloosaAL USA 35487 Dept Chem, Tuscaloosa, AL 35487 USA Florida State Univ, Natl High Magnet Field Lab, Ctr Interdisciplinary Magnet Resonance, Tallahassee, FL 32310 USA Florida State Univ Tallahassee FL USA 32310 ce, Tallahassee, FL 32310 USA Univ Florida, Dept Chem, Gainesville, FL 32611 USA Univ Florida Gainesville FL USA 32611 ept Chem, Gainesville, FL 32611 USA Univ Coll London, Dept Biol, London WC1H 9EW, England Univ Coll London London England WC1H 9EW Biol, London WC1H 9EW, England
Titolo Testata:
JOURNAL OF PHYSICAL CHEMISTRY B
fascicolo: 28, volume: 103, anno: 1999,
pagine: 5782 - 5786
SICI:
1520-6106(19990715)103:28<5782:9GESOC>2.0.ZU;2-W
Fonte:
ISI
Lingua:
ENG
Soggetto:
HIGH-FIELD EPR; BACTERIUM RHODOPSEUDOMONAS-VIRIDIS; ELECTRON-PARAMAGNETIC RESONANCE; R-26 REACTION CENTERS; PLANT PHOTOSYSTEM-I; PRIMARY DONOR; CAROTENOID CATION; SINGLE-CRYSTALS; ENDOR; COMPLEX;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
41
Recensione:
Indirizzi per estratti:
Indirizzo: Kispert, LD Univ Alabama, Dept Chem, POB 870336, Tuscaloosa, AL 35487 USA Univ Alabama POB 870336 Tuscaloosa AL USA 35487 , AL 35487 USA
Citazione:
T.A. Konovalova et al., "95-670 GHz EPR studies of canthaxanthin radical cation stabilized on a silica-alumina surface", J PHYS CH B, 103(28), 1999, pp. 5782-5786

Abstract

The 95-670 GHz EPR measurements at 5 K were performed on canthaxanthin radical cation chemically generated on silica-alumina. The 327 GHz and higher frequency EPR spectra were resolved into two principal components of the g tensor. Spectral simulation indicated this to be the result of 8 anisotropywhere g(parallel to) 2.0032 and g(perpendicular to) = 2.0023. This type ofg tensor is consistent with the theory for polyacene pi-radical cations, which states that the g tensor becomes cylindrically symmetric with increasing chain length. This also demonstrates that the symmetrical unresolved EPRline at 9 GHz is due to a carotenoid pi-radical cation with electron density distributed throughout the whole chain as predicted by RHF-INDO/SP molecular orbital calculations. The lack of temperature dependence of the EPR line widths over the range of 5-80 K at 327 GHz suggests rapid rotation of methyl groups even at 5 K that averages out the proton couplings from three oriented beta-protons. In fact, similar line widths at 5 K were observed at 670 GHz. Simulation of EPR spectra at 95-250 GHz gives only symmetrical unresolved lines. The present work shows that the 327-670 GHz EPR measurementsare sufficient to resolve the individual g tensors of C-H containing pi-radicals in powder and frozen glasses. Symmetry differences can be deduced from which radical identification can be made.

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Documento generato il 01/10/20 alle ore 07:43:41