New tricks and emerging applications from contemporary azobenzene research

Abstract

Azobenzenes have many faces. They are well-known as dyes, but most of all, azobenzenes are versatile photoswitchable molecules with powerful photochemical properties. Azobenzene photochemistry has been extensively studied for decades, but only relatively recently research has taken a steer towards applications, ranging from photonics and robotics to photobiology. In this perspective, after an overview of the recent trends in the molecular design of azobenzenes, we highlight three research areas where the azobenzene photoswitches may bring about promising technological innovations: chemical sensing, organic transistors, and cell signaling. Ingenious molecular designs have enabled versatile control of azobenzene photochemical properties, which has in turn facilitated the development of chemical sensors and photoswitchable organic transistors. Finally, the power of azobenzenes in biology is exemplified by vision restoration and photactivation of neural signaling. Although the selected examples reveal only some of the faces of azobenzenes, we expect the fields presented to develop rapidly in the near future, and that azobenzenes will play a central role in this development.

Red-shifted and pH-responsive imidazole-based azo dyes with potent antimicrobial activity

“…Moreover, the ammonium ion might increase the push-pull effects and turn the absorption towards longer wavelengths. Interestingly, the unique 6-amino and 5-imino substituents compare with the ortho-amino and methoxy groups of the known red-shifted azobenzenes 2,3 in relative position and H-bonding pattern. The antifungal and antibacterial activity of the new compounds was evaluated (Table 1 and SI-Table 3).…”

“…The most explored classes of halochromic dyes are the phthalides, triarylmethanes and fluorans, whereas azobenzenes have been more extensively studied as photochromic dyes. 1 Despite the impressive advances in the development of photoswitch applications, 2,3 azo dyes are still one of the most popular groups of pH-indicators. 1 Hydroxyazo or aminoazo dyes have been usually used as pH indicators, as significant spectral differences can be found between their acid and base forms.…”

“…Recently, azonium ions derived from amino-substituted azo dyes with ortho-groups exhibited unusual far-red/near-infrared absorptions. 2,3 However, the use of this new generation of aminoazo dyes has been hampered by laborious and demanding syntheses, as diazotization is often unsuitable due to the steric congestion around the azo bond.…”

Investigating the interaction of azobenzene moiety on the amino acid tryptophan

“…Azobenzene and several of its derivatives undergo reversible changes from the typically more stable trans-form to the less stable cis-form upon exposure to Ultraviolet light, resulting in a wavelengthdependent photostationary structure (Dokić et al, 2009;Fedele et al, 2022). Red-shifted azobenzenes tend to undergo rapid cis-to-trans conversions.…”

Red-light photoswitching of indigos in polymer thin films

“…1,2 Light is arguably the most attractive external stimulus for this purpose as it is non-invasive, waste-free, and can be applied in a highly controllable fashion with superior temporal, spatial and spectral resolution. Thus, systems responding to light are increasingly investigated, 3,4 with applications emerging in a wide range of research elds from optics 5,6 and (opto)electronics 7,8 to photobiology [9][10][11][12][13] and photomechanics. 14,15 Among other strategies, photoresponsive materials can be designed by incorporating photochromic molecules (photoswitches) onto the surface of a metal particle 16 or into the bulk of a macroscopic material.…”