Insights into the effect of the spacer on the properties of imidazolium based AIE luminogens

With the aim to obtain organic salts with potential applications in high performance molecular electronics, we combined properties of π-conjugated spacers, like 1,4-diethynylbenzene and 1,6-diethynylpyrene, with the ones of both imidazole and imidazolium units. Physico-chemical properties of obtained fluorescent organic salts were investigated performing thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC) and cyclic voltammetry measurements (CV). Photophysical behavior of the salts was analyzed in conventional solvents and ionic liquids, by UV–vis and fluorescence investigation. Solution phase aggregation study revealed that these salts self-assemble in conventional solvents and ionic liquids, leading to aggregation induced emission processes. Notably, emission was maintained also in the solid state, with higher or lower intensity compared with the solution, depending on which spacer is present. This latter, also impacts on the morphology of the aggregates, allowing fine tuning the properties of the supramolecular materials formed.