On the proton spin diffusion in powdered fumaric acid

Abstract

Spin diffusion is a well-established phenomenon in solid-state NMR, providing means to probe the molecular structure and transfer magnetization over extended intramolecular distances. Recently, we demonstrated that highly polarized 13C nuclei in 1-13C-fumaric acid can relay magnetization across crystallite boundaries to other 13C-labelled powders. To explore the possibility of using the abundant 1H network, in the present study, dry powdered fumaric acid was examined using conventional solid-state NMR techniques characterizing local order, relaxation and dynamical properties. The results reveal that, although 1H spin diffusion is intrinsically slow, both the diffusion rate and polarization lifetime increase with temperature. This offers new practical insights into the proton-mediated spin diffusion and may aid in designing more efficient polarization-relay strategies.