[Co(DTPA)]3− complex in gelatin gel as a highly sensitive shifting NMR/MRI temperature probe

The temperature sensitivity of paramagnetic chemical shifts in ¹H NMR spectra for the [Co(DTPA)]³⁻ complex in 10% gelatin gel (as a model substrate of human or animal tissues) was studied in detail. The maximum temperature sensitivity of the chemical shifts d(δ_exp)/dT studied in the gelatin gel of the complex was found to be 0.73 ppm/K (which is about 7% higher than in the previously studied D₂O solution of the compound). It turned out that the studied complex is characterized by the highest temperature sensitivity of chemical shifts in the NMR spectra among the complexes of paramagnetic d-elements. Moreover, this complex also shows the highest temperature sensitivity of chemical shifts taking into consideration the half-width of the signal itself (|CT|/W = 0.8 K⁻¹). The [Co(DTPA)]³⁻ complex can be considered as a promising compound for the design of temperature-sensitive NMR probes aimed at determining the local temperature in aqueous media and prospective MRI-assisted disease diagnosis.