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Title: Magnetic resonance and optical spectroscopic studies of carotenoids

Abstract

It is our goal to study the role of a host lattice in the formation of radicals and excited singlet and triplet states that are relevant to photosynthesis. Particular emphasis is being placed on determining what is special about carotenoids that natural photosynthetic systems require them as antennae as well as for protection. We are thus manipulating the host matrix so as to understand the carotenoid function (protection, quenching, energy transfer and antenna) and the structure of carotenoid cations. To characterize their properties, we have carried out EPR, ENDOR, optical, molecular orbital and electrochemical studies of carotenoids and carotenoid cations produced chemically, electrochemically, radiolytically (x-ray irradiated freon matrices) and photolytically (solution photolysis by excimer radiation) as a function of the host matrix. 36 refs.

Authors:
Publication Date:
Research Org.:
Alabama Univ., University, AL (USA). Dept. of Chemistry
Sponsoring Org.:
USDOE; USDOE, Washington, DC (USA)
OSTI Identifier:
5618929
Report Number(s):
DOE/ER/13465-6
ON: DE91014361
DOE Contract Number:
FG05-86ER13465
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CAROTENOIDS; OXIDATION; EXCITED STATES; TEMPERATURE DEPENDENCE; POLYMERS; ELECTRIC CONDUCTIVITY; RADICALS; CHEMICAL PREPARATION; ELECTROLYSIS; ELECTRON SPIN RESONANCE; ELECTRON TRANSFER; EXCIMER LASERS; MOLECULAR ORBITAL METHOD; NONLINEAR OPTICS; PHOTOLYSIS; PHOTOSYNTHESIS; PROGRESS REPORT; RADIOLYSIS; VOLTAMETRY; CHEMICAL RADIATION EFFECTS; CHEMICAL REACTIONS; CHEMISTRY; DECOMPOSITION; DOCUMENT TYPES; ELECTRICAL PROPERTIES; ENERGY LEVELS; GAS LASERS; HYDROCARBONS; LASERS; LYSIS; MAGNETIC RESONANCE; OPTICS; ORGANIC COMPOUNDS; PHOTOCHEMICAL REACTIONS; PHYSICAL PROPERTIES; PIGMENTS; RADIATION CHEMISTRY; RADIATION EFFECTS; RESONANCE; SYNTHESIS; TERPENES; 400500* - Photochemistry

Citation Formats

Kispert, L.D.. Magnetic resonance and optical spectroscopic studies of carotenoids. United States: N. p., 1991. Web.
Kispert, L.D.. Magnetic resonance and optical spectroscopic studies of carotenoids. United States.
Kispert, L.D.. 1991. "Magnetic resonance and optical spectroscopic studies of carotenoids". United States. doi:.
@article{osti_5618929,
title = {Magnetic resonance and optical spectroscopic studies of carotenoids},
author = {Kispert, L.D.},
abstractNote = {It is our goal to study the role of a host lattice in the formation of radicals and excited singlet and triplet states that are relevant to photosynthesis. Particular emphasis is being placed on determining what is special about carotenoids that natural photosynthetic systems require them as antennae as well as for protection. We are thus manipulating the host matrix so as to understand the carotenoid function (protection, quenching, energy transfer and antenna) and the structure of carotenoid cations. To characterize their properties, we have carried out EPR, ENDOR, optical, molecular orbital and electrochemical studies of carotenoids and carotenoid cations produced chemically, electrochemically, radiolytically (x-ray irradiated freon matrices) and photolytically (solution photolysis by excimer radiation) as a function of the host matrix. 36 refs.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1991,
month = 5
}

Technical Report:
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  • The fundamental goals of this project are (1) to understand the role of a host matrix in the formation and decay mechanisms of carotenoid cation radical and dication and (2) to determine the special properties of carotenoids that enable them to serve as photoprotective agents in photosynthesis and as possible components in electron transfer processes. Results to date are discussed briefly. Work will continue as outlined in the original proposal with emphasis on using simultaneous electrochemistry EPR, and optical methods, variable temperature electrochemistry using microelectrodes and fast scans to examine the more unstable intermediates formed upon electrochemical oxidation of syntheticallymore » prepared carotenoids.« less
  • The role of a host lattice of carotenoids were studied in the formation of radicals and excited singlet and triplet states that are relevant to photosynthesis. Particular emphasis is being placed on determining what is special about carotenoids that natural photosynthetic systems require them as antennae as well as for protection. The host matrix was manipulated so as to understand the carotenoid function of protection, quenching, energy transfer and antenna and also the structure of carotenoid cations. To characterize their properties, we have carried out EPR, optical, molecular orbital and electrochemical studies of carotenoid cations produced chemically, electrochemically, radiolytically (x-raymore » irradiated freon matrices) and photolytically (solution photolysis by excimer radiation) as a function of the host matrix. 42 refs.« less
  • It is our goal to study the role of a host lattice in the formation of radicals and excited singlet and triplet states that are relevant to various aspects of photosynthesis. During the first year, we had papers published or accepted for publication on: (a) the picosecond optical absorption lifetime measurements of carotenoids (the antenna and photoprotect device in plants); (b) EPR and ESE studies of porphyrins in the presence of carotenoids; (c) radicals formed in x-ray irradiated ..beta..-carotene; and (d) EPR and ESE studies of model systems that exhibit exchanged-narrowed EPR lines. Exchanged-narrowed EPR lines are observed in oxidizedmore » preparations of chlorophyll or bacteriochlorophyll and extensive study on other systems are needed to deduce the intermolecular interactions as a function of host lattice from the exchanged-narrowed lines. Studies along these lines are continuing. We have also began an extensive study into why the excited singlet lifetimes of the carotenoids are so short (10 ps), and are dependent on chain length. This requires extensive 4 K optical work on deuterated and protonated ..beta..-carotene, a study that we are carrying out at Argonne National Lab with M. Wasielewski. A continuing study is also being carried out on the preparation and structural identification of radical cations and polyenes. A list of the papers published or accepted in various journals and the papers presented at various meetings this reporting period is given. In addition, studies soon to be submitted for publication are summarized.« less