Strategy for the Construction of Diverse Poly‐NHC‐Derived Assemblies and Their Photoinduced Transformations

A series of supramolecular assemblies of types [Ag8(L)4](PF6)8 and [Ag4(L)2](PF6)4, obtained from the tetraphenylethylene (TPE) bridged tetrakis(1,2,4‐triazolium) salts H4‐L(PF6)4 and AgI ions, is described. The assembly type obtained dependends on the N‐wingtip substituents of H4‐L(PF6)4. Changes in the lengths of the N4‐wingtip substituents enables controlled formation of assemblies with either [Ag4(L)2](PF6)4 or [Ag8(L)4](PF6)8 stoichiometry. The molecular structures of selected [Ag8(L)4](PF6)8 and [Ag4(L)2](PF6)4 assemblies were determined by X‐ray diffraction analyses. While H4‐L(PF6)4 does not exhibit fluorescence in solution, their tetra‐NHC (NHC=N‐heterocyclic carbene) assemblies do upon NHC–metal coordination. Upon irradiation, all assemblies undergo a light‐induced, supramolecule‐to‐supramolecule structural transformation by an oxidative photocyclization involving phenyl groups of the TPE core, resulting in a significant change of the luminescence properties. Silver links: Tetrakis(1,2,4‐triazolium) salts H4‐L(PF6)4, featuring different N4 substituents, react with Ag2O to give, depending on the length of the N4 alkyl substituent, tetranuclear metallo‐supramolecular assemblies of type [Ag4(L)2](PF6)4 or octanuclear assemblies of type [Ag8(L)4](PF6)8. Both types of assemblies, upon irradiation, undergo oxidative photocyclization of the central tetrakisarylethylene unit to yield the complexes with a 9,10‐phenyl‐substituted phenanthrene bridge.