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Title: Magnetic resonance studies of irradiated 1,3-dimethylxanthine

Abstract

ESR and ENDOR techniques were used to study the x-ray induced damage in single crystals of the organic molecule theophylline (1,3 dimethylxanthine). A K-band spectrometer operating at 25GHz was used for ESR and ENDOR measurements. X-irradiation was carried out at 25K, 80K, and at room temperature, and spectra were observed as the temperature was varied. The low temperature experiments were achieved by using a closed cycle helium refrigeration system. A detailed analysis was made of the spectra, and four different radicals (R1, R2, R3, and R4) were identified after irradiation. Radical R1 was identified as a hydrogen atom radical, stable from 20 to 6OK; radical R2 was identified as an anion radical stable from 20 to 8OK; radical R3 was formed by hydrogen abstraction from the methyl group at C(10); and radical R4 was found to be a hydrogen-adduct species. Radical R3 was characterized by the following parameters: (1) Methylene hydrogen hyperfine tensor values of 28.8, 17.8, 13.2 G, and 27.7, 18.9, 8.8 G; (2) g-tensor values of 2.0012, 2.0019, and 2.0036; (3) Isotropic methyl group coupling of 4 G; (4) A spin density of 0.68 on C(10). Radical R4 was characterized by (1) an isotropic methelene hydrogen coupling ofmore » 37.1 G; (2) a maximum nitrogen coupling at N(9) of 21 G; (3) hydrogen coupling tensor values, due to protonation at N(g), of 12.0, 8.5, and 3.0 G; (4) rotating methyl group tensor values, at N(l), of 2.38, 2.71, and 5.19 MHz; (5) g-tensor values of 2.0012, 2.0033, and 2.0049; (6) spin density of 0.38 on N(9). A kinetics study indicated that radical R3 converts to radical R4 at about 160 K.« less

Authors:
Publication Date:
Research Org.:
Alabama Univ., Huntsville, AL (United States)
OSTI Identifier:
7038852
Resource Type:
Miscellaneous
Resource Relation:
Other Information: Thesis (Ph.D.)
Country of Publication:
United States
Language:
English
Subject:
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; 74 ATOMIC AND MOLECULAR PHYSICS; RADICALS; ELECTRON SPIN RESONANCE; ENDOR; THEOPHYLLINE; RADIATION CHEMISTRY; ANIONS; CHEMICAL REACTION KINETICS; EXPERIMENTAL DATA; MONOCRYSTALS; TEMPERATURE DEPENDENCE; TEMPERATURE EFFECTS; TEMPERATURE RANGE 0013-0065 K; TEMPERATURE RANGE 0065-0273 K; TEMPERATURE RANGE 0273-0400 K; X RADIATION; AROMATICS; AZAARENES; CARDIOVASCULAR AGENTS; CHARGED PARTICLES; CHEMISTRY; CRYSTALS; DATA; DRUGS; ELECTROMAGNETIC RADIATION; HETEROCYCLIC COMPOUNDS; INFORMATION; IONIZING RADIATIONS; IONS; KINETICS; MAGNETIC RESONANCE; NUMERICAL DATA; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; ORGANIC OXYGEN COMPOUNDS; PURINES; RADIATIONS; REACTION KINETICS; RESONANCE; TEMPERATURE RANGE; VASODILATORS; XANTHINES; 400600* - Radiation Chemistry; 664200 - Spectra of Atoms & Molecules & their Interactions with Photons- (1992-)

Citation Formats

Majid, E. Magnetic resonance studies of irradiated 1,3-dimethylxanthine. United States: N. p., 1989. Web.
Majid, E. Magnetic resonance studies of irradiated 1,3-dimethylxanthine. United States.
Majid, E. Sun . "Magnetic resonance studies of irradiated 1,3-dimethylxanthine". United States.
@article{osti_7038852,
title = {Magnetic resonance studies of irradiated 1,3-dimethylxanthine},
author = {Majid, E},
abstractNote = {ESR and ENDOR techniques were used to study the x-ray induced damage in single crystals of the organic molecule theophylline (1,3 dimethylxanthine). A K-band spectrometer operating at 25GHz was used for ESR and ENDOR measurements. X-irradiation was carried out at 25K, 80K, and at room temperature, and spectra were observed as the temperature was varied. The low temperature experiments were achieved by using a closed cycle helium refrigeration system. A detailed analysis was made of the spectra, and four different radicals (R1, R2, R3, and R4) were identified after irradiation. Radical R1 was identified as a hydrogen atom radical, stable from 20 to 6OK; radical R2 was identified as an anion radical stable from 20 to 8OK; radical R3 was formed by hydrogen abstraction from the methyl group at C(10); and radical R4 was found to be a hydrogen-adduct species. Radical R3 was characterized by the following parameters: (1) Methylene hydrogen hyperfine tensor values of 28.8, 17.8, 13.2 G, and 27.7, 18.9, 8.8 G; (2) g-tensor values of 2.0012, 2.0019, and 2.0036; (3) Isotropic methyl group coupling of 4 G; (4) A spin density of 0.68 on C(10). Radical R4 was characterized by (1) an isotropic methelene hydrogen coupling of 37.1 G; (2) a maximum nitrogen coupling at N(9) of 21 G; (3) hydrogen coupling tensor values, due to protonation at N(g), of 12.0, 8.5, and 3.0 G; (4) rotating methyl group tensor values, at N(l), of 2.38, 2.71, and 5.19 MHz; (5) g-tensor values of 2.0012, 2.0033, and 2.0049; (6) spin density of 0.38 on N(9). A kinetics study indicated that radical R3 converts to radical R4 at about 160 K.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1989},
month = {1}
}

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