Origin of isotropic shifts in lanthanide complexes: a study of the temperature dependence of the 1H n.m.r. spectra of the tetrakis-N,N-diethyldithiocarbamatolanthanate(III) anions

Abstract

The 'H n.m.r. spectra of the tetraethylammonium tetrakis-N,N-diethyldithiocarbamatolanthanate-(111), Et4N+ Ln(dtc);, ion pairs in acetonitrile solution, where Ln = Pr, Nd, Tb, Dy, Ho, Er, Tm and Yb, have been measured at various temperatures. The temperature dependences of the paramagnetic shifts of the Ln(dtc), anion are interpreted in terms of both a T-' and a T-2 contribution.It is shown that a treatment due to Bleaney satisfactorily accounts for the T-2 contribution. It is suggested that there is a significant contact contribution which is reflected in the T-' term.* In this paper we will confine our discussion to the resonances of the Ln(dtc); anions. Those