Electron spin resonance study on UV‐irradiated single crystal of (NH3iPr)6[Mo8O28(CHO)2] · 2H2O

EPR study on UV-irradiated single crystal of (NH3iPr)6 [Mo8 O28(CHO)2]·2H2O was carried out at room temperature. Three sets of EPR lines were observed. Spectra I and II are attributed respectively to paramagnetic Mo (V) centre (A) and (B). Line III may be assigned to an unstable-paramagnetic centre. Using the least-squares-fitting method to calculate the Hamiltonian parameters, we got the accurate principal values of g, hyperfine AMO and ligand hyperfine AH tensors, as well as-the direction cosines of their principal axes with respect to experimental coordinate system (xyz). The electron spin density was calculated from A value. The results showed that the unpaired electron occupies 4d orbital of molybdenum which appreciably contributes to the molecular orbital and the mechanism of direct spin coupling between the unpaired spin orbital of molybdenum and hydrogen orbital.