Redox Control over Acyl Hydrazone Photoswitches

Abstract

Photoisomerization provides a clean and efficient way of reversibly altering physical properties of chemical systems and injecting energy into them. These effects have been applied in development of systems such as photoresponsive materials, molecular motors, and photoactivated drugs. Typically, switching from more to less stable isomer(s) is performed by irradiation with UV or visible light, while the reverse process proceeds thermally or by irradiation using another wavelength. In this work we developed a method of rapid and tunable Z→E isomerization of C=N bond in acyl hydrazones, using aromatic thiols as nucleophilic catalysts. As thiols can be oxidized into catalytically inactive disulfides, the isomerization rates can be controlled via the oxidation state of the catalyst, which, together with the UV irradiation, provides orthogonal means to control the E/Z state of the system. As a proof of this concept, we have applied this method to control the diversity of acyl hydrazone based dynamic combinatorial libraries.

Photoswitchable double bonds: Synthetic strategies for tunability and versatility

“…Switching about C═N bonds is frequently explored in hydrazones. Otto and co‐workers have recently developed acyl hydrazone switches that respond to both photochemical and redox control . The Aprahamian group has worked extensively with this responsive moiety, determining how to greatly increase the thermal half‐lives of hydrazone‐based switches .…”

Straightforward synthesis of gold nanoparticles by adding water to an engineered small dendrimer

“…When D 2 O was used as the solvent, only the expected set of doublets was observed (21.3 (P=N) ppm and 50.6 (P=S) ppm, J PP = 29 Hz, Figure S5, Supporting Information File 1 ). However, when DMSO was the solvent used, several sets of doublets were observed within the same region ( Supporting Information File 1 , Figure S6) presumably due to the presence of both the Z and E- isomers of the hydrazones [ 51 ]. These isomers were also detected in the 1 H NMR spectra as two signals corresponding to the CH=N groups (8.13 ppm and 8.42 ppm) when DMSO was used as the solvent.…”

Multiple adaptation of constitutional dynamic networks and information storage in constitutional distributions of acylhydrazones

“…Acylhydrazones have been proven to be widely tunable photoswitches6,13 based on E / Z isomerization through photoinduced out-of-plane rotation about the CN bond and thermally activated in-plane nitrogen inversion, with their attractive features including facile preparation, high stability, efficiency of absorption, addressable and high fatigue resistance 13 a…”