Investigation of the structure of photosynthetic reaction centers. Progress report, June 1, 1981-January 5, 1983
In this initial phase of the project we have been concerned primarily with the development of the methodology of the application of ENDOR in the study of the photo-excited triplets in amorphous solids. Over the past year and a half the instrumentation has been vastly improved. First of all, by the incorporation of a computer. Secondly, by the development of a better cavity suitable for optical irradiation studies. And finally, as a result of an improved cryogenic system. Proper conditions for the recording of ENDOR spectra of randomly oriented triplets in a solid matrix were found in a study of a series of ground-state triplets with zero field splittings (D) ranging from less than 100 gauss to more than 400 gauss. The measurements established that to be successful ENDOR measurements on chlorophyll triplets must be performed at temperatures well below 10 K. Furthermore, it could be shown that hyperfine and quadrupole data extracted from spectra will be helpful for the elucidation of electronic as well as geometric structure. Finally, ENDOR measurements on a series of photo-excited triplets were performed. From the point of view of the objective of this research it was particularly encouraging to learn from these measurements that a short triplet lifetime does not preclude ENDOR measurements. In fact, of the molecules investigated those with the shortest tau/sub T/ gave the strongest ENDOR effect. This can be attributed to spin-alignment effects of which we can also take advantage in studies of chlorophyll systems. Measurements performed on the porphyrins give an insight into substituent effects which can be of aid in the elucidation of their electronic structure. Hyperfine data obtained from ZnTPP (CN)/sub 4/ suggest that the structure proposed for this molecule may be incorrect.
- Research Organization:
- Boston Univ., MA (USA)
- DOE Contract Number:
- AC02-81ER10911
- OSTI ID:
- 6576122
- Report Number(s):
- DOE/ER/10911-2; ON: DE83004903
- Country of Publication:
- United States
- Language:
- English
Similar Records
Investigation of the structure of photosynthetic reaction centers. Progress report, June 1, 1981-April 1, 1982
Investigation of the structure of photosynthetic reaction centers. Progress report, January 6, 1983-November 5, 1983
Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
09 BIOMASS FUELS
CHLOROPHYLL
EXCITED STATES
PHOTOSYNTHESIS
PHOTOCHEMISTRY
PORPHYRINS
ZINC COMPLEXES
ELECTRON SPIN RESONANCE
ENDOR
ENERGY CONVERSION
GROUND STATES
HYPERFINE STRUCTURE
RESEARCH PROGRAMS
SOLAR ENERGY
TRIPLETS
ULTRALOW TEMPERATURE
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
CONVERSION
ENERGY
ENERGY LEVELS
ENERGY SOURCES
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
MAGNETIC RESONANCE
MULTIPLETS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHYTOCHROMES
PIGMENTS
RENEWABLE ENERGY SOURCES
RESONANCE
SYNTHESIS
400500* - Photochemistry
140504 - Solar Energy Conversion- Biomass Production & Conversion- (-1989)