Photon Energy Storage in Strained Cyclic Hydrazones: Emerging Molecular Solar Thermal Energy Storage Compounds
Qian‐Feng Qiu, Sirun Yang, Mihael A. Gerkman, Heyifei Fu, Ivan Aprahamian, Grace G. D. Han
Abstract
The generally small Gibbs free energy difference between the Z and E isomers of hydrazone photoswitches has so far precluded their use in photon energy storing applications. Here, we report on a series of cyclic and acyclic hydrazones, which possess varied degrees of ring strain and, hence, stability of E isomers. The photoinduced isomerization and concurrent phase transition of the cyclic hydrazones from a crystalline to a liquid phase result in the storage of a large quantity of energy, comparable to that of azobenzene derivatives. We demonstrate that the macrocyclic photochrome design in combination with phase transition is a promising strategy for molecular solar thermal energy storage applications.