Exploring ortho-dianthrylbenzenes for Molecular Solar Thermal Energy Storage

Abstract

Photoswitches capable of absorbing light, storing it and releasing it on-demand as heat are known as molecular solar thermal systems. Compared to the commonly investigated photochromes in this field, azobenzenes and norbornadienes, anthracene dimers have been less explored due to challenges such as photooxidation of anthracene monomers and concentration-dependent photodimerization efficiency in solution. Here, this study reports the investigation of five ortho-dianthrylbenzenes designed to overcome these challegnes. Aryl-linking two anthracene moieties resulted in photoswitches with photodimerization quantum yields ranging from 11.5% to 16% in mesitylene. Additionally, the influence of donor or acceptor functional groups on the bridging unit was evaluated in terms of energy storage time (9 – 37 years), energy storage density (0.14 – 0.2 MJ kg-1), and solar energy storage efficiencies (0.38 – 0.66%). The experimental observations were supported by modelling based on density functional theory. These findings pave the way for future developments of anthracene-based photoswitches for molecular solar thermal applications.