Molecular solar thermal systems – control of light harvesting and energy storage by protonation/deprotonation

Abstract

The optical properties of pyridyl-substituted dihydroazulene (DHA) photoswitches can be tuned by protonation/deprotonation as well as the thermal back-reaction rate and amount of heat release from the vinylheptafulvene (VHF) photoisomers.

Recent Implementations of Molecular Photoswitches into Smart Materials and Biological Systems

“…Due to its one‐way (DHA→VHF) photochromism (VHF←DHA isomerization can only be induced thermally), it is also a promising switch for solar thermal energy storage and solar heat batteries, particularly upon replacing the phenyl ring with pyridine (which allows for reversible protonation that influences the VHF lifetime), or by design of a multimode switch combining DHA/VHF with DAEs …”

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

“…Unlike traditional photochemical energy storage in plants, the MOST systems operate in a closed cycle with light as the input and heat on demand as the output. Examples of promising molecular systems (Figure 1) are the azobenzene [3][4][5] system (AZO) (1) that upon irradiation undergoes a E-Z isomerization, the dihydroazulene [6][7][8][9] (DHA) system (2) that is converted to the photoisomer vinylheptafulvene (VHF) (3) and the norbornadiene 10-14 NBD) system (4) that undergoes a [2+2] cycloaddition to the photoisomer quadricyclane (QC) (5). A structurally very similar compound to the norbornadiene is the bicyclooctadiene (BOD) (6), also a cyclic compound that contains two double bonds in a ring structure.…”

Investigation of the Structural and Thermochemical Properties of [2.2.2]-Bicyclooctadiene Photoswitches

“… In these systems, the energy is stored in the photoisomer, and when triggered, the energy is released and the parent compound is recovered, ready to be recharged by light (Figure ). Several molecular systems, including azobenzene, − anthracene, tetracarbonyl-fulvalene-diruthenium, , dihydroazulene/vinylheptafulvene (DHA/VHF), − and norbornadiene/quadricyclane, − have been studied for MOST applications. Among these, one of the top candidates is the norbornadiene/quadricyclane (NBD/QC) system, where the NBD undergoes a photoinduced [2 + 2] cycloaddition to the photoisomer QC.…”

“…Molecular photoswitches that can absorb sunlight and convert it into a metastable photoisomer are attractive compounds for molecular solar thermal energy storage (MOST) applications. 12 In these systems, the energy is stored in the photoisomer, and when triggered, the energy is released and the parent compound is recovered, ready to be recharged by light (Figure 1). Several molecular systems, including azobenzene, 3−5 anthracene, 6 tetracarbonyl-fulvalene-diruthe-nium, 7,8 dihydroazulene/vinylheptafulvene (DHA/VHF), 9−12 and norbornadiene/quadricyclane, 13−17 have been studied for MOST applications.…”