Electronic pyroelectricity: the interplay of valence tautomerism and spin transition

Abstract

The rational design of multifunctional molecular components serves as the basis for designing materials with practical applications. “Electronic pyroelectricity,” i.e., transient voltage or current generated by the temperature-dependent spontaneous polarization induced by electrons, plays a pivotal role in modern sensor and energy conversion devices. Entropically favorable dynamic electron transfer processes such as valence tautomerism (VT) or spin transition have recently been proven to modulate the degree of co-alignment of permanent dipoles, i.e., the polarization in a molecular crystal. Two recent studies by Sato and co-workers have outlined the fruitful ways to achieve electronic pyroelectricity at the macroscopic level incorporating an electronic redistribution strategy by combining a labile electronic structure with the crystal engineering of the molecular orientation in the crystal lattice. These breakthroughs, hard on the heels of each other, opened up a new route to overcome the formidable challenge of obtaining materials with significant and nearly constant pyroelectric coefficients over a wide temperature range.