Holmium-DOTA as a responsive relaxation paramagnetic probe for NMR/MRI control of local temperature at high magnetic fields

In this work, the temperature dependence of Curie-spin (CS) contribution to the relaxation rate was studied by 1H NMR under magnetic fields of 7.05 and 18.79 T using the Ho complex with DOTA as an example. This is the first example of the detailed study of the temperature dependence of Curie-spin contribution to the paramagnetic transverse relaxation rate enhancements (CS-PTRRE) in lanthanide complexes other than dysprosium, taking into account the magnetic field strength and change of viscosity with temperature. It was found that due to the substantial temperature dependence of CS-PTRRE the Ho complex with DOTA is the first example of a temperature sensitive relaxation paramagnetic lanthanide probe for in situ temperature control by NMR/MRI in water environment at high magnetic fields.