Aza-bicyclodiene based photoswitches for molecular solar thermal energy storage

Abstract

The effect of N-substitution on the properties of bicyclodienes with different bridge lengths is analysed for energy storage application. The improvement in the properties with N-substitution is more prominent for bicyclodienes with longer bridge.

Bispericyclic Ambimodal Dimerization of Pentafulvene: The Origin of Asynchronicity and Kinetic Selectivity of the Endo Transition State

“…A previous report demonstrates high asynchronicity in the ambimodal reactions owing to the formation of singlet biradicals in bispericyclic TS, thus exhibiting a multireference character. The single-reference density functional theory (DFT)-based methods may be inappropriate to describe the multiconfigurational behavior, while the multireference methods are suitable for proper description of the singlet biradicals in the bispericyclic TSs. , Therefore, the relative energy profiles for all of the studied reactions were also generated using the multireference (12,12)-CASPT2/6-311++G** method and compared with those calculated with DLPNO-CCSD(T)/Def2-TZVP. The profiles were generated by estimating the electronic energies of the point structures using (12,12)-CASPT2/6-311++G**, and zero-point corrections were included at the ωB97XD/6-311++G** level.…”

Novel route to enhance the thermo-optical performance of bicyclic diene photoswitches for solar thermal batteries

“…The storage energies calculated using the DLPNO-CCSD(T) level are in the range of 141.15 to 158.38 kJ/mol for the type-I switches and 138.28 to 165.74 kJ/mol for the type-II photoswitches. It is worth to mention that the storage energy of the studied BBD-based switches is significantly higher than that of the prototype NBD/QC pair (96.06 kJ/mol) [ 36 ]. It is also apparent from Figure 2 that type-II photoswitches which are based on the BOD/TCO pair have a higher storage energy than the type-I systems which are based on the NBD/QC couple.…”

“…Moreover, the energy storage density ranges from 1.21 to 1.48 MJ/kg for type-I switches and 1.13 to 1.37 MJ/kg for type-II switches. The gravimetric energy densities of the studied photoswitches is higher than that of the NBD/QC pair (1.04 MJ/kg) [ 36 ]. Therefore, the elongation of the unsaturated bridge results in a higher energy storage capacity compared to the unsubstituted NBD/QC photoswitch.…”

“…The TBR barrier plays a decisive role in determining the energy storage time of the photoswitching system. The singlet biradicaloid TS involved during the thermal back isomerization of photoproduct to the parent bicyclic diene were initially predicted with the PBE functional employing CI-NEB method analogous to the previous studies [ 33 , 36 ]. The obtained TSs were re-optimized with PBE/6-311++G** level utilizing the Gaussian16 and vibrational analysis was performed at the same level of theory.…”

“…More importantly, the differences between the first important excitation wavelength of the diene and photoproduct are 52 and 72 nm for the type-Ib and Ic photoswitches and are larger than that of the NBD/QC pair (30 nm) [ 36 ]. This implies that the spectral overlap between the diene and the photoproduct is slightly reduced for the type-I photoswitches whose unsaturated bridge were extended using –(CO)– and –NH– units.…”