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Temperature dependence of the isotropic hyperfine coupling constants in 1,4-hydroquinone and 1,4-dihydroxynaphthalene cation radicals

✍ Scribed by Jussi Eloranta; Mikko Vuolle

Publisher
John Wiley and Sons
Year
1998
Tongue
English
Weight
220 KB
Volume
36
Category
Article
ISSN
0749-1581

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✦ Synopsis

The temperature dependences of hydroxyl group proton and ring proton isotropic hyperÐne coupling constants (IHFC) of 1,4-hydroquinone (HQ) and 1,4-dihydroxynaphthalene (NQ) cation radicals were measured by electron paramagnetic resonance spectroscopy. The spectral parameters were obtained in the temperature range 150È300 K using various solvents. The hydroxyl group proton IHFC data obtained were Ðtted to the theoretical temperature dependence model, yielding the hydroxyl group rotation barrier height and completely planar hydroxyl proton IHFC value. Experimental results are discussed with reference to theoretical density functional calculations. The new experimental rotation barrier heights for HQ and NQ cation radicals are 59 ^4 and 37 ^4 kJ mol~1 in nitromethane, respectively.

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