Heterodiazocines: Synthesis and Photochromic Properties, Trans to Cis Switching within the Bio-optical Window

Abstract

Diazocines, bridged azobenzenes, exhibit superior photophysical properties compared to parent azobenzenes such as high switching efficiencies, quantum yields, and particularly switching wavelengths in the visible range. Synthesis, however, proceeds with low yields, and derivatives are difficult to prepare. We now present two heterodiazocines which are easier to synthesize, and the general procedures should also provide facile access to derivatives. Moreover, both compounds can be switched with light in the far-red (650 nm). Accessibility and photophysical properties make them ideal candidates for applications such as photoswitchable drugs and functional materials.

Light‐Switchable Azobenzene‐Containing Macromolecules: From UV to Near Infrared

“…Implementing new small molecule azobenzene compounds into macromolecules is a straightforward way to prepare new visible or NIR‐light‐responsive azo‐macromolecules. Several visible‐ or NIR‐light‐responsive azobenzenes have been reported and not introduced into macromolecule systems yet: (1) For example, heterodiazocines (Compounds 24 and 25 ) are visible light‐responsive azo compounds ( Figure ) . They have high switching efficiencies and quantum yields.…”

Visible-Light Excitation of a Molecular Motor with an Extended Aromatic Core

“…Bridging of azobenzenes also afforded photoswitches operable in the far red region. 7 For diarylethenes, the extension of the π system 8 or the covalent linkage of triplet sensitizers afforded switches with red-shifted absorption spectra. 9 New photoswitches which can be operated with visible light are also being developed.…”

Reversible Photoswitching of Isolated Ionic Hemiindigos with Visible Light

“…Molecular photoswitches constitute the active core of many light‐responsive molecular machines and motors, smart materials, supramolecular systems, and photocontrollable drugs. Many potential applications of photoswitches, particularly in biological contexts require them to respond within the biooptical window, prompting synthetic efforts aimed at shifting their absorptions to longer wavelength . Recently, new classes of photoswitches such as DASAs, hydrazones, and indigoid chromophores have been developed with strong absorptions in the red region of the spectrum, and with high photoisomerization quantum yields.…”