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Azobenzenes (ABs) are versatile compounds featured in numerous applications for energy storage systems, such as solar thermal storages or phase change materials. Additionally, the reversible one‐electron reduction of these diazenes to the nitrogen‐based radical anion has been used in battery applications. Although the oxidation of ABs is normally irreversible, 4,4'‐diamino substitution allows a reversible 2e− oxidation, which is attributed to the formation of a stable bis‐quinoidal structure. Herein, we present a system that shows a bipolar redox behaviour. In this way, ABs can serve not only as anolytes, but also as catholytes. The resulting redox potentials can be tailored by suitable amine‐ and ring‐substitution. For the first time, the solid‐state structure of the oxidized form could be characterized by X‐ray diffraction. [ABSTRACT FROM AUTHOR]

The article discusses the use of the inverse-electron-demand Diels-Alder (IEDDA) reaction as a synthetic tool for creating complex molecular structures. The authors focus on the use of bidentate Lewis acid catalysts to facilitate the IEDDA reaction between phthalazines and cyclooctynes. They found that the catalyst significantly increased the reaction rate and yield of the desired products. The authors also explored the scope of the reaction by testing different substituted phthalazines and cyclooctynes. The method presented in the article provides a convenient and efficient way to synthesize polycyclic aromatic hydrocarbons fused to eight-membered carbocycles. [Extracted from the article]

Compounds with multiple photoswitching units are appealing for complex photochemical control of molecular materials and nanostructures. Herein, we synthesized novel meta‐ and para‐ connected (related to the nitrogen of the indoline) azobenzene‐spiropyran dyads, in which the central benzene unit is shared by both switches. We investigated their photochemistry using static and time‐resolved transient absorption spectroscopy as well as quantum chemical calculations. In the meta‐compound, the individual components are photochemically decoupled due to the meta‐pattern. In the para‐compound the spiro‐connectivity leads to a bifunctional photoswitchable system with a red‐shifted absorption. The azobenzene and the spiropyran can thus be addressed and switched independently by light of appropriate wavelength. Through the different connectivity patterns two different orthogonally photoswitchable systems have been obtained which are promising candidates for complex applications of light control. [ABSTRACT FROM AUTHOR]

Reaction monitoring by electrospray (ESI) mass spectrometry (MS) is a valuable technique to investigate reaction mechanisms. It allows a glimpse into the reacting solution and the characterization of transient intermediates by tandem mass spectrometry. Herein we studied an intriguing gold(III)‐catalyzed synthesis of dicoumarins which includes a combination of hydroarylation and homocoupling steps. Reactants and products could be detected in positive mode. In negative mode, some species corroborating proposed transient intermediates could be detected by direct infusion ESI of reacting solutions. The ions were characterized by accurate mass determinations and gas‐phase fragmentation. Thus, indications for the nature and ligand sphere of reaction intermediates in the catalytic cycle could be collected. [ABSTRACT FROM AUTHOR]

Herein we report the synthesis of nonsymmetrically substituted azobenzene derivatives with meta -alkyl substituents on one side and meta -aryl moieties with electron-donating or electron-withdrawing groups on the other side. The half-lives for the thermal (Z)- to (E)-isomerization of these molecules were measured in n -octane, which allows investigation of the strength of the aryl–alkyl interactions between their substituents. It was found that the London dispersion donor strength of the alkyl substrate is the decisive factor in the observed stabilization, whereas the electronic structure of the aryl fragment does not influence the isomerization in a significant way. [ABSTRACT FROM AUTHOR]

The absorption of a positively charge-tagged azobenzene molecule is studied in the gas-phase by measuring photoinduced fragmentation of ions as a function of time. This technique provides information on prompt as well as delayed fragmentation, and a single dissociation channel after one-photon absorption is identified. The spectra in solution, as well as in the gas-phase, show a weak S0 → S1, a strong S0 → S2, and a broad absorption band in the UV regime. The bands are assigned through time dependent density functional theory calculations. The ratio of the various absorption bands depends on the trans to cis isomerization fraction and may be tuned by light irradiation. Gas-phase absorption spectra are presented and discussed in terms of trans and cis isomers. [ABSTRACT FROM AUTHOR]