problematic (mAzo, Figure 1B). Therefore, fabrication of an azo-STC that can operate efficiently under full-spectrum solar irradiation remains a challenge.Herein, we demonstrated an integrated azo-STC device that could efficiently store both UV and visible light under fullspectrum solar irradiation. From top to bottom, the device consisted of Coumarin 314, PmAzo, a UV-pass filter, and PAzo ( Figure 1C,D). The four-layer device featured two active cells to store solar energy and two filtering layers to modify the effective incident spectrum. The two active layers were different azopolymers, PAzo and PmAzo which store energy by isomerization of the chromophores on the polymer side chains from the low energy trans isomers to the higher energy cis isomers.The top layer of the device was comprised of 3 drop cast films of Coumarin 314 (≈1-2 μm) in a poly(4-vinyl)phenol (PvPh) matrix which absorbs strongly around 460 nm (blue) while transmitting UV and green wavelengths ( Figure 1E,F). Moreover, Coumarin 314 is also a fluorescent dye and thus actively down-converts absorbed blue wavelengths. Broad fluorescence emission from Coumarin 314 centered at 560 nm can then be stored by the layer of PmAzo immediately following ( Figure 1G; Figure S1, Supporting Information). Thus, the dye which serves as a filter, also actively down converts light that would have caused cis-to-trans isomerization to wavelengths which instead drive trans-to-cis energy storage. The second layer contained PmAzo which efficiently stores visible light. Specifically, irradiation of PmAzo at wavelengths corresponding to the trans π*←π (λ max = 323 nm) and π*←n (λ max = 460 nm) bands induces trans-to-cis isomerization, storing energy. [10] The cis π*←n transition occurs at shorter wavelengths (λ max = 447 nm) and thus the back-isomerization of PmAzo can be prevented by blocking only 400-510 nm (blue) light using the Coumarin 314 layer. Thus, the separation of the trans and cis π*←n transitions enables energy storage from longer (green/orange) wavelengths of visible light. In case PmAzo does not completely absorb all long-wavelengths of light which can induce cis-to-trans backisomerization in PAzo, a UV-pass filter was inserted before the final PAzo layer ( Figure 1H). The PAzo layer was used to efficiently store UV light ( Figure 1I). Other than occurring at longer wavelengths (lower energy) with respect to PmAzo, the π*←π transition (λ max = 351 nm) of PAzo behaves similarly. However, the previous UV-pass filter was necessary to prevent irradiation of the cis π*←n (λ max = 441 nm) transition which causes predominantly cis-to-trans back-isomerization due to the relatively larger absorption coefficient relative to the trans transition which occurs at similar wavelengths.First, to study charging of solution-phase solar thermal cells, solutions of PmAzo and PAzo in tetrahydrofuran (THF) were used as solution-phase solar thermal cells in the integrated device (Figure 2A-C). UV-vis spectra showed that solar As the energy consumption continues its precipitous ...

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The nickel-catalyzed carboxylation of organic halides or pseudohalides using carbon dioxide is an emerging method to prepare synthetically valuable carboxylic acids. Here, we report a detailed mechanistic investigation of these reactions using the carboxylation of aryl halides with (PPh 3) 2 Ni II Cl 2 as a model reaction. Our studies allow us to understand several general features of nickel-catalyzed carboxylation reactions. For example, we demonstrate that both a Lewis acid and halide source are beneficial for catalysis. To this end, we establish that heterogeneous Mn(0) and Zn(0) reductants are multifaceted reagents that generate noninnocent Mn(II) or Zn(II) Lewis acids upon oxidation. In a key result, a rare example of a well-defined nickel(I) aryl complex is isolated, and it is demonstrated that its reaction with carbon dioxide results in the formation of a carboxylic acid in high yield (after workup). The carbon dioxide insertion product undergoes rapid decomposition, which ca These three oxidation states correspond to the onbe circumvented by a ligand metathesis reaction with a halide source. Our studies have led to both a revised mechanism and the development of a broadly applicable strategy to improve reductive carboxylation reactions. A critical component of this strategy is that we have replaced the heterogeneous Mn(0) reductant typically used in catalysis with a well-defined homogeneous organic reductant. Through its use, we have increased the range of ancillary ligands, additives, and substrates that are compatible with the reaction. This has enabled us to perform reductive carboxylations at low catalyst loadings. Additionally, we demonstrate that reductive carboxylations of organic (pseudo)halides can be achieved in high yields in more practically useful, non-amide solvents. Our results describe a mechanistically guided strategy to improve reductive carboxylations through the use of a homogeneous organic reductant, which may be broadly translatable to a wide range of crosselectrophile coupling reactions.

We synthesized a novel green-light-responsive tetra-ortho-isopropoxy-substituted azobenzene (ipAzo). Cis-ipAzo forms a strong host-guest complex with γ-cyclo dextrin (γ-CD) whereas trans-ipAzo binds weakly. This new photoresponsive host-guest interaction is reverse to the well-known azobenzene (Azo)/α-cyclodextrin (α-CD) complex, which is strong only between trans-Azo and α-CD. By combining the UV-light-responsive Azo/α-CD and green-light-responsive ipAzo/γ-CD host-guest complexes, a photoresponsive orthogonal supramolecular system is developed.