Prev. Article Next Article Table of Contents

Article

Electron Transfer of Carotenoids Imbedded in MCM-41 and Ti−MCM-41: EPR, ENDOR, and UV−Vis Studies

Yunlong Gao, Tatyana A. Konovalova, Tao Xu, and Lowell D. Kispert*

Department of Chemistry, Box 870336, University of Alabama, Tuscaloosa, Alabama 35487-0336

J. Phys. Chem. B, 2002, 106 (42), pp 10808–10815

DOI: 10.1021/jp025978s

Publication Date (Web): September 28, 2002

To whom correspondence should be addressed. E-mail: likspert@ bama.ua.edu. Fax: (205) 348-9104.

Abstract

Electron transfer (ET) reactions of carotenoids (Car), β-carotene (I), canthaxanthin (II), and 7‘-apo-7‘,7‘-dicyano-β-carotene (III) imbedded in MCM-41 and Ti−MCM-41 were studied as a function of oxidation potential. The ET efficiency in MCM-41 was highest for the carotenoid with the lowest oxidation potential. The presence of Ti⁴⁺ in the framework of MCM-41 enhanced the ET efficiency of all carotenoids, but the enhancement did not depend on oxidation potential. The enhancement depends on whether complexes are formed between carotenoids and Ti⁴⁺. Complexes were formed with I and III but not with II. The presence of Ti⁴⁺ results in a large blue shift of the maximum absorption wavelength due to changes in the carotenoid conformation.

View: Full Text HTML | Hi-Res PDF