Designing Chiral, Pro-Polar Structures for Observing Ferroelectricity: Molecular Analogue of KNO3

Abstract

Observation and creation of a pro-chiral center is a prerequisite in chemical synthesis for generating chiral structures. On the other hand, temporary and reversible generation of chiral or polar structures using physical forces such as electricity is a need of present technology for observing nonlinear behavior. Thus, one can synthesize a pro-polar structure, akin to a pro-chiral center using chemical interactions, for facilitating physical forces in generating chiral/polar structures, a novel way for designing molecular materials. At room temperature, the structure of KNO3 and anilinium nitrate (AnHNO3) is centrosymmetric, although the latter showed molecular properties in the form of distinct helical NH···O hydrogen bonding to generate a dipole moment, which in turn gets canceled due to the formation of antiparallel double helical chains. We could separate these helical chains of NH···O hydrogen bonding, by chemical design, synthesis of analogues molecules (para-ethyl anilinium nitrate), and crystallization through a gel as well slow evaporation technique, to obtain a pro-polar and chiral structure with molecular ferroelectric behavior. Thus, creation of a pro-polar structure, presented here by modifying the cation in KNO3 to observe room temperature ferroelectric behavior, will help in designing novel molecular ferroelectric materials.