Radical cation generation from singlet and triplet excited states of all-trans-lycopene in chloroform
Related Experiment Video
Updated: Aug 22, 2026

Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development
Published on: April 15, 2013
Rui-Min Han1, Yi-Shi Wu, Juan Feng
1State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, People's Republic of China.
Abstract:
On direct photoexcitation, subpicosecond time-resolved absorption spectroscopy revealed that the 1B(u)-type singlet excited state of all-trans-lycopene in chloroform was about seven times more efficient than all-trans-beta-carotene in generating the radical cation. The time constant of radical cation generation from the 1B(u)-type state was found to be approximately 0.14 ps, a value that was comparable for the two carotenoids. On anthracene-sensitized triplet excitation, radical cation generation was found to be much less efficient for lycopene than for beta-carotene. A slow rising phase (20-30 micros) in the bleaching of ground-state absorption was common for both lycopene and beta-carotene in chloroform and was ascribed to an efficient secondary reaction with a solvent radical leading to the formation of carotenoid radical cations. The reverse ordering in the tendency of the excited states of different multiplicities for the two carotenoids to generate radical cations is discussed in relation to the two carotenoids as scavengers of free radicals.
Related Concept Videos
Photochemical Electrocyclic Reactions: Stereochemistry
Selection Rules: Photochemical Activation
Radicals: Electronic Structure and Geometry
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
Radical Reactivity: Overview
Radical Formation: Addition
Similar to charge conservation in chemical reactions, spin conservation is implicit for radical reactions. Accordingly, the product formed must possess an unpaired...
Radical Reactivity: Nucleophilic Radicals
Radical Reactivity: Electrophilic Radicals
![[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F59739.jpg&w=3840&q=50)
