Synthesis, characterization and computational evaluation of bicyclooctadienes towards molecular solar thermal energy storage

Abstract

Molecular solar-thermal energy storage (MOST) systems are based on photoswitches that reversibly convert solar energy into chemical energy. In this context, bicyclooctadienes (BOD) undergo a photoinduced transformation to the corresponding...

Prospects of Improving Molecular Solar Energy Storage of the Norbornadiene/Quadricyclane System through Bridgehead Modifications

“…Furthermore, the systems have relatively long thermal back reaction times. However, we have recently reported that the storage energy can be significantly increased by altering the bridging unit of the NBD/QC system, a line of thought, which we will expand upon here. , …”

“…More specifically, we focus on scrutinizing the effects by elongating the bridging unit and on introducing heteroatoms. Our recent theoretical and experimental investigations have shown that elongating the bridge by a single carbon atom to obtain bicyclooctadiene (BOD) resulted in a 2–3-fold increase in the energy storage density of the system. , This increase in storage energy is likely to be caused by increased strain in the ring systems of the tetracyclooctane (TCO) photoproduct for which the bridging unit, contrary to the BOD, adopts a staggered conformation. The increased storage energy comes without compromising the linear optical properties, yet the thermal back reaction barriers were significantly reduced relative to the NBD/QC analogues.…”

“…However, we have recently reported that the storage energy can be significantly increased by altering the bridging unit of the NBD/QC system, a line of thought, which we will expand upon here. 45,46 In the current investigation, we report the theoretical prospects of modifying the bridging unit in the NBD/QC system in order to possibly improve on three crucial parameters of MOST systems: storage energy density, thermal back reaction barrier, and UV−vis absorption properties. More specifically, we focus on scrutinizing the effects by elongating the bridging unit and on introducing heteroatoms.…”

A rechargeable molecular solar thermal system below 0 °C

“…Molecular solar thermal (MOST) systems have been recognized as a promising avenue to harvest and store thermal energy. [10][11][12][13][14][15] In the charging process, a stable isomer of a photochromic molecule absorbs photon energy and is converted into a high-energy metastable isomer, thereby storing solar energy in chemical bonds. The MOST system is discharged when the metastable isomer switches back to the stable isomer by external stimuli, with the release of stored energy in the form of heat.…”

Multiconfigurational calculations and photodynamics describe norbornadiene photochemistry

“…MOST materials isomerize from a thermodynamically stable structure to a metastable structure, storing the absorbed energy in strained chemical bonds. Many organic molecules have been investigated for MOST applications, such as azobenzene, 16,[22][23][24] anthracene, 25,26 tetracarbonyl-fulvalene-diruthenium, [27][28][29][30] dihydroazulene/vinylheptafulvene (DHA/VHF), [31][32][33][34] bicyclooctadiene/tetracyclooctane (BOD/TCO) 35,36 and norbornadiene/quadricyclane (NBD/QC). [37][38][39][40][41][42][43] The NBD/QC system is one of the top candidates, where the NBD undergoes a [2+2]-photocycloaddition to the photoisomer QC (Figure 1).…”