Self‐Coiling and Aggregation Behaviors of Organic Fluorescent Probes With Saturated Aliphatic Chains in Polar Fluorinated Arenes

ABSTRACT The self‐coiling behaviors of organic molecules in fluorinated solvents haven't been explored previously. As one particular type of fluorous solvent, polar fluorinated arenes are widely used in both academia and industry. In this report, several modern techniques, including visual observation, concentration‐dependent UV‐visible spectroscopy, concentration‐dependent fluorescence spectroscopy and kinetics measurements, dynamic light scattering (DLS) tests, and theoretical calculations, are employed to examine the self‐coiling and aggregation behaviors of two types of organic fluorescent probes with saturated aliphatic chains in three polar fluorinated arenes. In contrast to in aqueous solutions, their behaviors differ significantly: the single‐headed probes in polar fluorinated arenes maintain a stretched hatpin conformation, form aggregates at low concentrations, and form excimers at higher concentrations; most double‐headed probes tend to self‐coil in these solvents, but the optimal conformation depends on the chain length and can form excimers at very low concentrations, while their CAgCs are comparable to those of single‐headed probes. As an exciting discovery, the macrolactonization reaction of 8‐hydroxyoctanoic acid in trifluorotoluene has been obviously improved by molecular self‐coiling. Therefore, our discoveries may provide guidance for the regulation of the synthesis of macrocycles in such solvents in the future.