Temperature-Dependent Isotropic Shifts in Some Paramagnetic Transition Metal Acetylacetonates

Abstract

A detailed analysis of the temperature dependence of the CH₃ and CH isotropic shifts in V(acac)₃ (Hacac = pentane-2,4-dione) and the CH₃ isotropic shift in Ru(acac)₃ is given. The temperature dependence of the CH₃ isotropic shifts in Mn(acac)₃ and Fe(acac)₃ are also reported. The pseudo-contact shifts are negligible for them all except in Ru(acac)₃. The contact shifts cannot be explained with a single value of the Fermi coupling constant and it is suggested that either vibrational effects or Fermi contact contributions from excited states are responsible.