The Dewar Isomer of 1,2-Dihydro-1,2-azaborinines: Isolation, Fragmentation, and Energy Storage

Electrocatalytic Energy Release of Norbornadiene-Based Molecular Solar Thermal Systems: Tuning the Electrochemical Stability by Molecular Design

Molecular solar thermal (MOST) systems, such as the norbornadiene/quadricyclane (NBD/QC) couple, combine solar energy conversion, storage, and release in a simple one-photon one-molecule process. Triggering the energy release electrochemically enables high control of the process, high selectivity, and reversibility. In this work, the influence of the molecular design of the MOST couple on the electrochemically triggered back-conversion reaction was addressed for the first time. The MOST systems phenyl-ethyl ester-NBD/QC (NBD1/QC1) and p-methoxyphenyl-ethyl ester-NBD/QC (NBD2/QC2) were investigated by in-situ photoelectrochemical infrared spectroscopy, voltammetry, and density functional theory modelling. For QC1, partial decomposition (40 %) was observed upon back-conversion and along with a voltammetric peak at 0.6 V_fc , which was assigned primarily to decomposition. The back-conversion of QC2, however, occurred without detectable side products, and the corresponding peak at 0.45 V_fc was weaker by a factor of 10. It was concluded that the electrochemical stability of a NBD/QC couple is easy tunable by simple structural changes. Furthermore, the charge input and, therefore, the current for the electrochemically triggered energy release is very low, which ensures a high overall efficiency of the MOST system.

Optimization of the thermochemical properties of the norbornadiene/quadricyclane photochromic couple for solar energy storage using nanoparticles

In this paper, we present an investigation concerning the prospects of using nanoparticles to improve solar energy storage properties of three different norbornadiene/quadricyclane derivatives. Computationally, we study how different nanoparticles influence the properties of the systems that relate to the storage of solar energy, namely, the storage energy and the back reaction barrier. Our approach employs hybrid quantum mechanical/molecular mechanical calculations in which the molecular systems are described using density functional theory while the nanoparticles are described using molecular mechanics. The interactions between the two subsystems are determined using polarization dynamics. The results show that the influence of the nanoparticles on the thermochemical properties largely depends on the type of nanoparticle used, the relative orientation with respect to the nanoparticle, and the distance between the the nanoparticle and the molecular system. Additionally, we find indications that copper and/or titanium dioxide nanoparticles can lower the energy barrier of the back reaction for all of the studied systems without significantly lowering the storage capability of the systems. Consequently, the study shows that nanoparticles can potentially be employed in the optimization of molecular photoswitches towards solar energy storage.

The effects of solvation on the back reaction and storage capabilities of solar thermal energy storage systems

Solvent effects on molecular solar thermal energy storage systems have been investigated using density functional theory combined with solvent models describing the effects of viscosities and dielectric constants on chemical reaction rates. We have addressed the following issues concerning how solvents influence both the thermochemical properties and the thermal relaxation kinetics of the studied systems, how the friction of the solvent influences the recrossing of the reactions along with the dynamics and force constants of the transition state. We observe that the rate constants for the chemical reactions of the molecular solar thermal energy storage systems depend strongly on the dielectric solvent properties and the viscosities of the solvents.

Germaborenes: Borylene Transfer Agents for the Synthesis of Iminoboranes

Halide and phenyl substituted germaborenes were shown to react with azides at room temperature and transfer a borylene moiety to give iminoboranes. This iminoborane synthesis based on a borylene transfer route was investigated computationally in the case of the phenyl substituted germaborene.

Accessing 1,2-Substituted Cyclobutanes through 1,2-Azaborine Photoisomerization

We provide a seminal example of the utility of the 1,2-azaborine motif as a 4C+1N+1B synthon in organic synthesis. Specifically, conditions for the practically scalable photoisomerization of 1,2-azaborine in a flow reactor are reported that furnish aminoborylated cyclobutane derivatives. The C-B bonds could also be functionalized to furnish a diverse set of highly substituted cyclobutanes.