Unexpected temperature dependence of 1H paramagnetic shift in MAS NMR of nickelocene

Abstract

This work revisits the temperature dependence of ¹H paramagnetic shift in nickelocene as a potential nuclear magnetic resonance (NMR) thermometer under fast magic angle spinning (MAS) rate. Surprisingly, an abnormal temperature dependence of ¹H paramagnetic shift has been observed. In addition to a 1/T dependence term, a 1/T² dependence term must be included to correctly describe the curvature behavior of the δ_¹H-T correlation under fast MAS rate.