The radicals CH2COO- (I) and CH3CHCOO- (II) produced by gamma irradiation at room temperature of a single crystal of zinc acetate dihydrate are studied by ENDOR spectroscopy. The signal intensity of radical I is found to be strongly temperature dependent in the range 130-200 K. The ENDOR enhancement has a maximum at T 170 K. It is shown that this behaviour is a consequence of the hindered rotation of the -CH2 group, which is very slow in this temperature range with respect to the EPR time scale. The enhancements are calculated by taking into account the nuclear relaxation rate due to the exchange motion and the dynamical parameters of the motion are obtained.
An ENDOR study of the slow intramolecular motion in the CH2COO- radical.
BRUSTOLON, MARINA ROSA;MANIERO, ANNA LISA;
1988
Abstract
The radicals CH2COO- (I) and CH3CHCOO- (II) produced by gamma irradiation at room temperature of a single crystal of zinc acetate dihydrate are studied by ENDOR spectroscopy. The signal intensity of radical I is found to be strongly temperature dependent in the range 130-200 K. The ENDOR enhancement has a maximum at T 170 K. It is shown that this behaviour is a consequence of the hindered rotation of the -CH2 group, which is very slow in this temperature range with respect to the EPR time scale. The enhancements are calculated by taking into account the nuclear relaxation rate due to the exchange motion and the dynamical parameters of the motion are obtained.Pubblicazioni consigliate
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