Low Molecular Weight Norbornadiene Derivatives for Molecular Solar-Thermal Energy Storage

M. Quant, A. Lennartson, A. Dreos, M. Kuisma, P. Erhart, K. Börjesson, and K. Moth-Poulsen
Chemistry - A European Journal 22, 13265 (2016)
doi: 10.1002/chem.201602530

Molecular solar-thermal energy storage systems are based on molecular switches that reversibly convert solar energy into chemical energy. Herein, we report the synthesis, characterization, and computational evaluation of a series of low molecular weight (193-260 g/mol) norbornadiene-quadricyclane systems. The molecules feature cyano acceptor and ethynyl-substituted aromatic donor groups, leading to a good match with solar irradiation, quantitative photo-thermal conversion between the norbornadiene and quadricyclane, as well as high energy storage densities (396-629 J/kg). The spectroscopic properties and energy storage capability have been further evaluated through density functional theory calculations, which indicate that the ethynyl moiety plays a critical role in obtaining the high oscillator strengths seen for these molecules.