UV photochemical and thermochemical reactions of the MnO4- ions doped into single crystals of NH4ClO4 and NH4BF4 have been investigated via the method of electron paramagnetic resonance (EPR). An isotropic EPR spectrum displaying a 55Mn hyperfine sextet has been observed in both reactions. The EPR spectra of the Mn(II) species produced by UV irradiation and by thermal treatments are identical and identical to that exhibited by the doped Mn2+ ions. The g-factor is g = 2.004 and the hyperfine constant is A55 = 96.6 G in NH4ClO4 for the Mn2+ ions produced by thermal treatments, by UV irradiation, and by doping. The corresponding values are g = 2.008 and A55 = 94.2 G for NH4BF4. The observed MnVIIO4- to Mn(II) reduction can be regarded as the reduction part of an overall redox reaction between MnO4- and the NH4+ group. We discuss the mechanism of the solid-state redox reaction.
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