ABSTRACT
Efficient solar energy storage is a key challenge in striving toward a sustainable future. For this reason, molecules capable of solar energy storage and release through valence isomerization, for so-called molecular solar thermal energy storage (MOST), have been investigated. Energy storage by photoconversion of the dihydroazulene/vinylheptafulvene (DHA/VHF) photothermal couple has been evaluated. The robust nature of this system is determined through multiple energy storage and release cycles at elevated temperatures in three different solvents. In a nonpolar solvent such as toluene, the DHA/VHF system can be cycled more than 70â times with less than 0.01 % degradation per cycle. Moreover, the [Cu(CH3 CN)4 ]PF6 -catalyzed conversion of VHF into DHA was demonstrated in a flow reactor. The performance of the DHA/VHF couple was also evaluated in prototype photoconversion devices, both in the laboratory by using a flow chip under simulated sunlight and under outdoor conditions by using a parabolic mirror. Device experiments demonstrated a solar energy storage efficiency of up to 0.13 % in the chip device and up to 0.02 % in the parabolic collector. Avenues for future improvements and optimization of the system are also discussed.
Subject(s)
Azulenes/chemistry , Cycloheptanes/chemistry , Lab-On-A-Chip Devices , Photochemical Processes , Solar EnergyABSTRACT
The formation of optically active 3,4-dihydrocoumarins is presented by merging aminocatalysis with an N-heterocyclic carbene-catalyzed internal redox reaction. The products are formed in good to excellent yields and in general with excellent enantioselectivities. Moreover, the developed procedure demonstrates the potential of enantioselective, multicatalytic sequences. By employing an enantiopure aminocatalyst in the enantiodifferentiating step, the challenges related to achieving high stereoinductions by deployment of optically active NHC-catalysts can be circumvented.
ABSTRACT
An organocatalytic iminium ion/N-heterocyclic carbene (NHC) cascade reaction between ß-keto phenyltetrazolesulfones and α,ß-unsaturated aldehydes, providing direct access to optically active 2,4-disubstituted cyclopent-2-enones, has been developed. The products are isolated in good yields with high enantioselectivities.
