Starazo triple switches – synthesis of unsymmetrical 1,3,5-tris(arylazo)benzenes

Abstract

Multistate switches allow to drastically increase the information storage capacity and complexity of smart materials. In this context, unsymmetrical 1,3,5-tris(arylazo)benzenes – ‘starazos’ – which merge three photoswitches on one benzene ring, were successfully prepared. Two different synthetic strategies, one based on Baeyer–Mills reactions and the other based on Pd-catalyzed coupling reactions of arylhydrazides and aryl halides, followed by oxidation, were investigated. The Pd-catalyzed route efficiently led to the target compounds, unsymmetrical tris(arylazo)benzenes. These triple switches were preliminarily characterized in terms of their isomerization behavior using UV–vis and 1H NMR spectroscopy. The efficient synthesis of this new class of unsymmetrical tris(arylazo)benzenes opened new avenues to novel multistate switching materials.

Photoswitches with different numbers of azo chromophores for molecular solar thermal storage

“…S1 and S6, ESI †). 34,38,39 Compounds 2, 3 and their intermediates were fully characterized using nuclear magnetic resonance (NMR) spectroscopy (Fig. S2-S5 and S7-S10, ESI †).…”

Multiple Azoarenes Based Systems – Photoswitching, Supramolecular Chemistry and Application Prospects

“…Furthermore, in 2020, Wegner and co‐workers synthesized an unsymmetrical triad system C3‐13 a by connecting three different photoswitches for wavelength selective photoswitching (Figure 19). [97a] Prior to that, they have computationally investigated such design using C3‐13 b – d for controlling the switching to gain multistate photoswitching [97b] . However, due to overlapping of absorption bands in UV‐Vis spectroscopy and complex spectral data in 1 H‐NMR spectroscopy, no selective photoswitching was achieved.…”

Modification of Azobenzenes by Cross-Coupling Reactions

“…In 2020, the coupling of 3,5-dibromoazobenzene with N-Boc-N-(4-methoxyphenyl)hydrazide to give 3,5bis[N′-Boc-N′-(4-methoxyphenyl)hydrazino]azobenzene in 58% yield was reported (Scheme 4). 22 The obtained product was then oxidized to yield a C 2 -symmetric 3,5-bis(4-methoxyphenylazo)azobenzene. Unsymmetric tris(arylazo)benzenes were accessible by sequential coupling.…”

“…Unsymmetric tris(arylazo)benzenes were accessible by sequential coupling. 22 Scheme 4 Pd-catalyzed Buchwald-Hartwig cross-coupling reaction of 3,5-dibromoazobenzene 22…”