Comparing Molecular Gelators and Nongelators Based on Solubilities and Solid-State Interactions

The relationship between molecular structure and gelation ability was investigated for a series of pyridine-based compounds. Nineteen compounds were synthesized and screened for gelation. Of these, eight were discovered to be gelators for a variety of organic solvent/water combinations. Solubility studies on the bulk powders revealed that gelators and nongelators are indistinguishable based on their room temperature solubilities. Likewise, X-ray diffraction experiments indicated that the presence (or absence) of ID intermolecular interactions does not correlate with gelation ability. van't Hoff analyses of the temperature-dependent solubilities revealed that the majority of gelators have higher dissolution enthalpies and entropies than nongelators. In combination, these data suggest a complex relationship between molecular structure and gelation ability.