Nuclear magnetic resonance study of the temperature dependence of paramagnetic chemical shifts of [Co(EDTA)]2- complexes in gelatin gel

NMR spectroscopy was applied to study the temperature dependences of paramagnetic chemical shifts of the [Co(EDTA)](2-) complex (1) in D2O solution and in 10% gelatin gel (as a model medium for human or animal tissues). The maximum temperature sensitivity of the chemical shifts d(delta(exp))/dT was found to be 0.64 ppm K-1 (in 10% gelatin gel). The half-width of the signals of the complex essentially depends on the solution viscosity and temperature, owing to the dipole contribution to the paramagnetic increase in the spin-spin relaxation rate. Complex 1 can be considered as a promising compound for the design of temperature-sensitive NMR probes for determining the local temperature in aqueous media and for advanced diagnosis of diseases using MRI technologies.