NMR investigation of different-ligand complexes of lanthanides. Lanthanide-induced increase in rate of spin-lattice relaxation

It was established by 1H and 19F NMR that different-ligand complexes in a stoichiometric ratio of 2:1, which exist as ion pairs, are formed in the reaction of the trispivaloyltrifluoroacetonates of the lightest lanthanides with the macrocyclic polyether 18-crown-6 in solution. Analysis of the paramagnetic lanthanide-induced shifts in the NMR spectra indicates similarity in the geometric structures of the complexes. From the data from relaxation NMR spectroscopy it is concluded that the molecule of the macrocyclic polyether enters the first coordination sphere of the lanthanide ion in the cations of the ion pairs