Arylazobenzimidazoles: versatile visible-light photoswitches with tuneable Z-isomer stability.

Benzimidazole heterocycles are of great importance in medicinal chemistry due to their applicability to a wide range of pharmacological targets, therefore representing a prototypical "privileged structure". In photopharmacology, azoheteroarene photoswitches have emerged as valuable tools for a variety of applications due to the high tuneability of their photophysical properties. Benzimidazole-based photoswitches could therefore enable the optically-controlled investigation of many pharmacological targets and find application in materials science. Here we report a combined experimental and computational investigation of such arylazobenzimidazoles, which allowed us to identify derivatives with near-quantitative bidirectional photoswitching using visible light and highly tuneable Z-isomer stability. We further demonstrate that arylazobenzimidazoles bearing a free benzimidazole N-H group not only exhibit efficient bidirectional photoswitching, but also excellent thermal Z-isomer stability, contrary to previously reported fast-relaxing Z-isomers of N-H azoheteroarenes. Finally, we describe derivatives which can be reversibly isomerized with cyan and red light, thereby enabling significantly "red-shifted" photocontrol over prior azoheteroarenes. The understanding gained in this study should enable future photopharmacological efforts by employing photoswitches based on the privileged benzimidazole structure.

Disequilibrating azobenzenes by visible-light sensitization under confinement.

Photoisomerization of azobenzenes from their stable E isomer to the metastable Z state is the basis of numerous applications of these molecules. However, this reaction typically requires ultraviolet light, which limits applicability. In this study, we introduce disequilibration by sensitization under confinement (DESC), a supramolecular approach to induce the E-to-Z isomerization by using light of a desired color, including red. DESC relies on a combination of a macrocyclic host and a photosensitizer, which act together to selectively bind and sensitize E-azobenzenes for isomerization. The Z isomer lacks strong affinity for and is expelled from the host, which can then convert additional E-azobenzenes to the Z state. In this way, the host-photosensitizer complex converts photon energy into chemical energy in the form of out-of-equilibrium photostationary states, including ones that cannot be accessed through direct photoexcitation.

A Study in Scaffold Hopping: Discovery and Optimization of Thiazolopyridines as Potent Herbicides That Inhibit Acyl-ACP Thioesterase.

In the search for new chemical entities that can control resistant weeds by addressing novel modes of action (MoAs), we were interested in further exploring a compound class that contained a 1,8-naphthyridine core. By leveraging scaffold hopping methodologies, we were able to discover the new thiazolopyridine compound class that act as potent herbicidal molecules. Further biochemical investigations allowed us to identify that the thiazolopyridines inhibit acyl-acyl carrier protein (ACP) thioesterase (FAT), with this being further confirmed via an X-ray cocrystal structure. Greenhouse trials revealed that the thiazolopyridines display excellent control of grass weed species in pre-emergence application coupled with dose response windows that enable partial selectivity in certain crops.

Photocontrolled Energy Storage in Azobispyrazoles with Exceptionally Large Light Penetration Depths.

Azobispyrazole, 4pzMe-5pzH, derivatives with small terminal substituents (Me, Et, i-Pr, and n-Pr) are reported to undergo facile reversible photoswitching in condensed phases at room temperature, exhibiting unprecedentedly large effective light penetration depths (1400 µm of UV at 365 nm and 1400 µm of visible light at 530 nm). These small photoswitches exhibit crystal-to-liquid phase transitions upon UV irradiation, which increases the overall energy storage density of this material beyond 300 J/g that is similar to the specific energy of commercial Na-ion batteries. The impact of heteroarene design, the presence of ortho methyl substituents, and the terminal functional groups is explored for both condensed-phase switching and energy storage. The design principles elucidated in this work will help to develop a wide variety of molecular solar thermal energy storage materials that operate in condensed phases.