A Liquid Arylazopyrazole Derivative as Molecular Solar Thermal Fuel with Long-term Thermal Stability

Abstract

A liquid arylazopyrazole derivative is newly synthesized as molecular solar thermal fuel. It shows efficient trans-to-cis photoisomerization in the neat liquid state, with the cis-isomer having a significantly longer thermal half-life (t1/2 = 3,069 h, at 25 °C). It overcomes the limited thermal stability of the corresponding liquid cis-azobenzene derivative (t1/2 = 16 h) and marked a gravimetric energy density of 41 kJ¢mol11, which meets the requirement for thermophysical heat storage applications.