Conformational Dynamics and Thermosensory Properties of [Ln(H2O)n(EDTA)]– (Ln = Pr, Eu, Tb, Ho, Er, Tm) Complexes in Aqueous Solutions according to NMR Data

The paramagnetic, thermosensory, and molecular dynamic properties of the [Ln(H 2 O) n (EDTA)] – (Ln = Pr, Eu, Tb, Ho, Er, Tm) complexes were studied by 1 H NMR. The maximum temperature sensitivity of paramagnetic chemical shifts d (δ exp )/ dT turned out to be 0.48 ppm/K for the Tb complex. It was found that the intramolecular dynamics is due to the inversion of the ethylene cycle and the concerted reorientation of the acetate groups. The value of the activation barrier found for the europium complex turned out to be = 49 ± 3 kJ/mol. The [Ln(H 2 O) n (EDTA)] – complexes can be considered as promising compounds for the design of thermosensitive NMR probes aimed at determining the local temperature in aqueous media.