Electron spin resonance of X-ray irradiated single crystals of ammonium paramolybdate tetrahydrate

Abstract

The paramagnetic species produced by x-ray irradiation of single crystals of ammonium paramolybdate (NH₄)₆Mo₇O₂₄. 4H₂O has been studied by E.S.R. spectroscopy. Only one of the seven Mo nuclei was seen to give rise to hyperfine coupling with the spin of the unpaired electron. The hyperfine coupling tensor and the g tensor were found to have different principle axes and a general method is presented for their determination in this case. The electronic structure of the paramagnetic species has been discussed in terms of molecular orbital theory in a semi-quantitative manner. The bonding coefficient, α, for the odd electron orbital and the contact spin density, χ, were estimated and compared with those of the related molybdenum complex anions.