Parahydrogen-Induced Polarization Transfer to 19F in Perfluorocarbons for 19FNMR Spectroscopy and MRI

Fluorinated substances are important in chemistry, industry, and the life sciences. In a new approach, parahydrogen-induced polarization (PHIP) is applied to enhance 19FMR signals of (perfluoro-n-hexyl)ethene and (perfluoro-n-hexyl)ethane. Unexpectedly, the end-standing CF3 group exhibits the highest amount of polarization despite the negligible coupling to the added protons. To clarify this non-intuitive distribution of polarization, signal enhancements in deuterated chloroform and acetone were compared and 19F-19FNOESY spectra, as well as 19F T1 values were measured by NMR spectroscopy. By using the well separated and enhanced signal of the CF3 group, first 19FMR images of hyperpolarized linear semifluorinated alkenes were recorded. [PUBLICATION ABSTRACT]