Long-lived states involving a manifold of fluorine-19 spins in fluorinated aliphatic chains

Long-lived states (LLSs) have lifetimes TLLS that exceed longitudinal spin-lattice relaxation times T1. In this study, lifetimes TLLS(19F) have been measured in three different achiral per- and polyfluoroalkyl substances (PFAS) containing two or three consecutive CF2 groups. In a static magnetic field B0=11.7 T, the lifetimes TLLS(19F) exceed the longitudinal relaxation times T1(19F) by about a factor of 2. The lifetimes TLLS(19F) can be strongly affected by binding to macromolecules, a feature that can be exploited for the screening of fluorinated drugs. Both TLLS(19F) and T1(19F) should be longer at lower fields where relaxation due to the chemical shift anisotropy (CSA) of 19F is less effective, which is demonstrated here by running experiments at two fields of 11.7 and 7 T.