A new approach to determining the structure of lanthanide complexes in solution according to the Curie-spin contribution to the paramagnetic spin-spin relaxation rate enhancements: Ho-DOTA

Abstract

In this work, we propose for the first time a new type of NMR method for obtaining structural information on Ln complexes in solutions based on the analysis of the Curie-spin contribution to the paramagnetic spin-spin relaxation rate enhancements on the ligand nuclei. The application of the proposed methodology was carried out in this work by the example of studying the structure of the complex anion [Ho(DOTA)(H2O)]− (I) in D2O. Earlier we carried out the assignment of signals [S.P. Babailov, P.V. Dubovskii, E.N. Zapolotsky, Polyhedron 79 (2014) 277], investigated the molecular conformational dynamics and the dependence of the spin-spin relaxation rate on the magnetic field of complex I. Actually, the Curie spin contribution to the paramagnetic spin-spin relaxation rate enhancements on the ligand nuclei of this complex was determined by varying the constant magnetic field and temperature. As a result, it was found that the structure of the complex in solution is identical to its structure in the crystalline phase (found by the X-ray diffraction).