Photoinduced E to Z isomerization of tetraphenylethylene derivatives within organometallic supramolecular assemblies
Xiao‐Xu Liu, Yang Li, Xin Li, F. Ekkehardt Hahn, Ying‐Feng Han
Abstract
Abstract Isolation of E -1,2-bis(4-bromophenyl)-1,2-diphenyl-ethylene from the E/Z isomer mixture obtained by a McMurry coupling reaction and reaction of this isomer with imidazole followed by N -alkylation with n BuBr and anion exchange yielded the bisimidazolium tetraphenylethylene (TPE) derivative H 2 - E - 1 (PF 6 ) 2 . The reaction of H 2 - E - 1 (PF 6 ) 2 with Ag 2 O yielded the di-nuclear metallarectangle [Ag 2 ( E - 1 ) 2 ](PF 6 ) 2 where the two bis-NHC donors E - 1 bridge two silver atoms. Irradiation of [Ag 2 ( E - 1 ) 2 ](PF 6 ) 2 leads to E/Z isomerization of the di-NHC ligand and formation of Z - 1 in the mononuclear complex [Ag( Z - 1 )]PF 6 . Demetallation of the di-NHC ligand with NH 4 Cl/NH 4 PF 6 yielded bisimidazolium salt H 2 - Z - 1 (PF 6 ) 2 . The unique isomerization of the E -TPE derivative into its Z -isomer via metal complex formation/irradiation/demetallation cannot be achieved by irradiation of the individual imidazolium salt. The emissive properties of the TPE complexes [Ag 2 ( E - 1 ) 2 ](PF 6 ) 2 and [Ag( Z - 1 )]PF 6 have been investigated.