Azobenzene-functionalized N-heterocyclic carbenes as photochromic ligands in silver(i) and gold(i) complexes

Abstract

The reaction of meta- and para-bromomethylene-azobenzenes with 1-methyl-imidazole yields the respective meta-/para-functionalized azobenzenes tagged with an imidazolium group. Similar reactions of ortho- and para-bromo-azobenzene with imidazole and successive quaternation with benzylbromide give the analogues, with an imidazolium group in ortho/para substituted azobenzenes. With the exception of the ortho derivative, all imidazolium salts could be transformed into their respective silver(i) complexes by reaction with Ag2O. Transmetallation of these silver(i) complexes with (Me2S)AuCl gives the azobenzene-containing complexes (NHC)AuCl. Two of these formed crystals suitable for X-ray diffraction, which revealed the typical linear coordination geometry of the NHC-Au-Cl moiety. All gold complexes feature E→Z photo-isomerisation upon irradiation with UV light. The thermal back reaction to the E-isomers is relatively slow and comparable to that of other azobenzene compounds.

Room Temperature Reversible Z→E Photoisomerization of Azobenzene Appended to Anthraquinone‐Benzimidazole Based Photoswitches with Resolved n→π* Absorption Band

“…In recent years, azobenzene‐based photoswitchable compounds have tremendous interest because of light‐triggered isomerization of N=N double bonds, from one state to another state with an acute change in geometry of the molecule, electronic properties, dipole moment, refractive index, and electrochemical properties , . Due to photolabile and photo‐induced peculiar changes of azobenzene derivatives have been employed as photochromic compounds owing to excellent candidates . Derivatives of azobenzene exist in two conformations either in trans or cis , the trans form energetically more stable than cis .…”

Azobenzene-functionalized iridium(iii) triscyclometalated complexes

“…From these, just the most recent ones are intended for the construction of photo-sensitive organometallics. [38][39][40][41][42][43] Cyclometalated phenylpyridine ligands are among the most popular ligands for the construction of organometallic complexes for many applications. Nevertheless, to the best of our knowledge, there are no examples of photochromic phenylpyridine azobenzenes.…”

Using Photoactive N-Heterocyclic Carbenes Monolayers to Identify the Influence of Surface Proximity on Photoswitching Activity

“…Stilbene-NHC adduct was synthesized via a one-step S N 2 reaction, by exploiting the reactivity of the free nitrogen atom in the imidazole ring. 30 The desired adduct, 1-p-methyl-trans-stilbene-3-methyl-1H-imidazolium chloride (stilbeneimidazolium, 1), was prepared at 84% yield by N-substitution of N-methylimidazole with 4-chloromethyl-trans-stilbene (Scheme 2, full synthetic details can be found in the SI, Fig. S1-S6).…”