Holmium complex with DOTA as NMR super-sensitive temperature sensor reagent for spectroscopic and tomography monitoring of aqueous systems

Previously the NMR signals were assigned and molecular dynamics of the holmium complexes with DOTA was studied using ¹H NMR [Babailov S.P., Dubovskii P.V., Zapolotsky E.N. Polyhedron 2014, 79, 277-283 (DOI: 10.1016/j. poly.2014.04.067)]. It is known that lanthanide chelates with this ligand are very thermostable. The gadolinium complex with DOTA is used in clinic as relaxation contrast agent. Nevertheless, temperature dependence of paramagnetic properties of holmium complex with DOTA was not investigated in detail. In the paper the ¹H NMR method is used to study the temperature dependence of the lanthanide-induced shifts (LISs) for complex [Ho(H₂O)(DOTA)]^-. It was found that the LISs have a linear dependence on 1/T. The studied coordination compound may serve as the most sensitive ¹H NMR lanthanide paramagnetic probes (as compared with other complexes of 4f- and d-elements both in organic and aqueous solutions) for in situ temperature control in solutions. The coordination compound studied may also have a medical use for determining the local temperature of the body using MRI.