π-Conjugated diimidazolium salts: rigid structure to obtain organized materials

Phenylene ethynylene based diimidazolium salts differing in the alkyl chain length borne on the imidazolium ion and anion nature were synthesized. Their properties were studied both in solution and in the solid state. Salts obtained were able to aggregate in organic solvent solution. Aggregate formation was studied by performing concentration dependent measurements using UV-vis, fluorescence and Resonance Light Scattering. Furthermore, features of the aggregates were also investigated in the solid state by means of fluorescence and Scanning Electron Microscopy measurements. Finally, Density Functional Theory calculations were performed to obtain insights into the interaction geometry in the salts investigated. Data collected evidence that aggregation processes are affected by a combined action of different factors derived from the nature of the salt and solvent. The above features also influence the morphology of the aggregates as well as the ability of their thin films to give blue emission. On the whole, information gained could represent a useful starting point for applications of these salts in the optoelectronic field among others.