Molecular Solar Thermal Energy Storage Systems with Long Discharge Times Based on the Dihydroazulene/Vinylheptafulvene Couple

TY - JOUR

T1 - Molecular Solar Thermal Energy Storage Systems with Long Discharge Times Based on the Dihydroazulene/Vinylheptafulvene Couple

AU - Mogensen, Josefine

AU - Christensen, Oliver

AU - Kilde, Martin Drøhse

AU - Abildgaard, Martin

AU - Metz, Lotte

AU - Kadziola, Anders

AU - Jevric, Martyn

AU - Mikkelsen, Kurt V.

AU - Nielsen, Mogens Brøndsted

PY - 2019/3/14

Y1 - 2019/3/14

N2 - Molecular solar thermal energy storage (MOST) systems based on photochromic molecules that undergo photoisomerization to high-energy isomers are attractive for storage of solar energy in a closed-energy cycle. One challenge is to control the discharge time of the high-energy isomer. Here we show that incorporation of a strong acceptor substituent in the seven-membered ring of the dihydroazulene/vinylheptafulvene (DHA/VHF) couple increases the half-life of the energy-releasing VHF-to-DHA back-reaction from hours to more than a day in a polar solvent. For some derivatives, the absorption maximum of the photo-active DHA is also significantly redshifted, thereby better matching the solar spectrum. Synthetic protocols and kinetics studies are presented together with a computational study of the energy densities of the systems and excitation spectra. The computations show that the increased lifetime of the high-energy isomer is counter-balanced by a lower energy storage capacity in vacuo than for the parent system, but a slightly higher energy density than for the parent system in a polar solvent.

AB - Molecular solar thermal energy storage (MOST) systems based on photochromic molecules that undergo photoisomerization to high-energy isomers are attractive for storage of solar energy in a closed-energy cycle. One challenge is to control the discharge time of the high-energy isomer. Here we show that incorporation of a strong acceptor substituent in the seven-membered ring of the dihydroazulene/vinylheptafulvene (DHA/VHF) couple increases the half-life of the energy-releasing VHF-to-DHA back-reaction from hours to more than a day in a polar solvent. For some derivatives, the absorption maximum of the photo-active DHA is also significantly redshifted, thereby better matching the solar spectrum. Synthetic protocols and kinetics studies are presented together with a computational study of the energy densities of the systems and excitation spectra. The computations show that the increased lifetime of the high-energy isomer is counter-balanced by a lower energy storage capacity in vacuo than for the parent system, but a slightly higher energy density than for the parent system in a polar solvent.

U2 - 10.1002/ejoc.201801776

DO - 10.1002/ejoc.201801776

M3 - Journal article

SN - 1434-193X

VL - 2019

SP - 1986

EP - 1993

JO - European Journal of Organic Chemistry

JF - European Journal of Organic Chemistry

IS - 10

ER -