Synthesis of green and blue fluorescent ladder-type conjugated imidazolium compounds

The synthetic route to ladder-type conjugated imidazolium compounds consisting of Suzuki coupling, chlorination, and intramolecular cyclization reactions was developed. The optical properties of materials and theoretical calculations were investigated to demonstrate that methylene- and ethylene-bridged imidazolium compounds show green and blue fluorescence, respectively. The coordination ability of the counter anion had an influence on the solubility and fluorescence quantum yield of the compounds.