Template‐Controlled Synthesis of Polyimidazolium Salts by Multiple [2+2] Cycloaddition Reactions

The tetrakisimidazolium salt H(4)‐2(Br)(4), featuring a central benzene linker and 1,2,4,5‐(nBu‐imidazolium‐Ph‐CH=CH‐) substituents reacts with Ag(2)O in the presence of AgBF(4) to yield the tetranuclear, oktakis‐NHC assembly [3](BF(4))(4). Cation [3](4+) features four pairs of olefins from the two tetrakis‐NHC ligands perfectly arranged for a subsequent [2+2] cycloaddition. Irradiation of [3](BF(4))(4) with a high pressure Hg lamp connects the two tetra‐NHC ligands through four cyclobutane linkers to give compound [4](BF(4))(4). Removal of the template metals yields the novel oktakisimidazolium salt H(8)‐5(BF(4))(8). The tetrakisimidazolium salt H(4)‐2(BF(4))(4) and the oktakisimidazolium salt H(8)‐5(BF(4))(8) have been used as multivalent anion receptors and their anion binding properties towards six different anions have been compared.