Carotenoid cation radical electrochemical properties

The electrochemical properties of carotenoids has been reviewed [102,103]. Electrochemical data for several naturally occurring carotenoids including oxidation potentials, reaction rate constants and kinetic equilibrium constants were discussed. Conventional electrochemical techniques such as cyclic voltammetry (CV) were treated. The oxidation potential of neutral carotenoids, corresponding to the formation of cation radicals were 0.50 - 0.72 V versus SCE, and that of carotenoid cation radicals, corresponding to the formation of dications were 0.52 - 0.95 V versus SCE. Further details are available [104,105],... 

Spectroscopic and electrochemical properties of carotenoid cation radicals are already referred to. 

Deng, Y. (1999). Carotenoid radical cations and dications studied by electrochemical, optical, and flow injection analysis Lifetime, extended chain conjugation, and isomerization properties. Ph.D dissertation, The University of Alabama, Tuscaloosa, AL. 

Miscellaneous Physical Chemistry. A kinetic study has been made of the electrochemical reduction of /8-carotene. The photoelectron quantum yield spectrum and photoelectron microscopy of /3-carotene have been described. Second-order rate constants for electron-transfer reactions of radical cations and anions of six carotenoids have been determined. Electronic energy transfer from O2 to carotenoids, e.g. canthaxanthin [/8,/3-carotene-4,4 -dione (192)], has been demonstrated. Several aspects of the physical chemistry of retinal and related compounds have been reported, including studies of electrochemical reduction, the properties of symmetric and asymmetric retinal bilayers, retinal as a source of 02, and the fluorescence lifetimes of retinal. Calculations have been made of photoisomerization quantum yields for 11-cis-retinal and analogues and of the conversion of even-7r-orbital into odd-TT-orbital systems related to retinylidene Schiff bases. ... 

---