The Gelling Ability of Some Diimidazolium Salts: Effect ofIsomeric Substitution of the Cation and Anion

The gelling ability of some geminal imidazolium salts was investigatedboth in organic solvents and in water solution. Organicsalts differing either in the cation or anion structurewere taken into account. In particular, the effects on the gelphaseformation of isomeric substitution on the cation oranion as well as of the use of mono- or dianions were evaluated.As far as the cation structure is concerned, isomeric cations,such as 3,3’-di-n-octyl-1,1’-(1,4-phenylenedimethylene)diimidazoliumand 3,3’-di-n-octyl-1,1’-(1,3-phenylenedimethylene)diimidazolium, were used. On the other hand, in additionto the bromide anion, isomeric dianions, such as the 1,5- and2,6-naphthalenedisulfonate anions, were also examined. Afterpreliminary gelation tests, different factors affecting the obtainedgel phases, such as the nature of the solvent, organogelatorconcentrations, and action of external stimuli, were analyzed.The gel-phase formation was also studied as a functionof time, by using resonance light scattering measurements. Gelmorphologies were analyzed by scanning electron microscopy.To further support the understanding of the different behaviorshown by the isomeric cations, some representative ion pairswere analyzed by DFT-based investigations. The collected dataunderline the significant role played by isomeric substitutionof both cation and anion structures in determining the gellingcapability of the investigated salts, as well as the properties ofthe gel phases. Finally, DFT investigations were helpful in theidentification of the structural features affecting the self-assembly.