A Supramolecular Ferroelectric Realized by Collective Proton Transfer

Abstract

Cooperative crystals: In ferroelectric cocrystals of iodanilic acid (see picture, orange) and 5,5′-dimethyl-2,2′-bipyridine (green), the molecules are linked into polar chains by OH⋅⋅⋅N and N+H⋅⋅⋅O− hydrogen bonds. The application of a small electric field (E) effects a cooperative proton transfer across the hydrogen bonds, which is accompanied by a reversal of the polarity (P).