Protonic Conduction in Imidazole: A Solid-State ¹⁵N NMR Study

Abstract

Reports of protonic conductivity in crystalline imidazole describe a pronounced anisotropy in the transport of H+ with respect to crystallographic direction. Since charge is carried mainly along imidazole's hydrogen bonding axis (c), it has long been hypothesized that the phenomenon involves the tunneling of protons through hydrogen bonds. A two-dimensional nitrogen-15 exchange NMR study of 15N-labeled imidazole, however, demonstrates that the conduction mechanism does not involve the reorientation of the imidazole ring invoked in current models.