Vanadium-51 nuclear magnetic resonance (51V NMR spectroscopy) is a method for the characterization of vanadium-containing compounds and materials. 51V comprises 99.75% of naturally occurring vanadium. The nucleus is quadrupolar with I = 7/2, which is not favorable for NMR spectroscopy, although its quadrupole moment and thus the linewidths are unusually small, while its magnetogyric ratio is relatively high (+7.0492 rad T−1s−1), so that 51V has 38% receptivity vs 1H. Its resonance frequency is close to that of 13C (gyromagnetic ratio = 6.728284 rad T−1s−1).
The chemical shift dispersion is great as illustrated by this series: 0 for VOCl3 (chemical shift standard), −309 for VOCl2(O-i-Pr), −506 VOCl(O-i-Pr)2, and −629 VO(O-i-Pr)3. For vanadates, the parent orthovanadate and its conjugate acid absorb at −541 ([VO4]3-) and 534 ([HVO4]2-). For decavanadate, three shifts are observed in accord with the number of nonequivalent sites: −422, −502, −519.[1][2]