Fluorous solvents have been widely used as reaction media in organic synthesis for more than 40 years. Among the fluorous solvents, perfluorinated solvents are the most well-known for being used in organic synthesis, because they form a clear phase interface with organic molecules at room temperature as a result of special interactions, and this phase interface disappears as the temperature rises. Moreover, there is another type of fluorous solvent as a reaction medium in organic synthesis that has recently attracted a great deal of attention, which involves polar fluorinated arenes, such as trifluorotoluene (BTF), fluorobenzene (PhF), 1,2-difluorobenzene (DFB), and the like (Figure 1B). Due to their special physical and chemical properties, these polar fluorinated arenes are highly important not only as reaction media but also as essential and fundamental building blocks for the synthesis of some special fluorine-containing materials, agrochemicals, and medicines. Therefore, they are of great interest and in high demand for the chemical industry. The molecular structures of polar fluorinated arenes are partially fluorinated, which make them amphipathic to both fluorocarbons and organics. It is also considered to be more environmentally friendly due to the fact that it contains less fluorine. Besides being miscible with perfluorinated solvents and organic solvents, they are also capable of excellently dissolving organic compounds. Therefore, they are also referred to as “amphiphilic” or “hybrid” fluorous solvents, and it is traditionally believed that organic solutes in them distribute as a homogeneous solution.

These polar fluorinated arenes not only have unique physical and chemical properties, such as considerable polarity and special coordinating ability, but also enhance their metabolic stability with the introduction of C–F bonds, which encourage people to utilize some of them in organic synthesis for safety purposes. In electrochemistry, redox reactions, Lewis acid-catalyzed reactions, phase transfer reactions, transition metal-catalyzed reactions, and many other applications, these solvents are widely used. Recently, the important role that these polar fluorinated arenes play in free radical reactions has gradually attracted the attention of researchers, such as the diversification of C–H bonds through radical chain transfer in BTF. C–F bonds in these solvents exhibit high bond dissociation energies (can be up to 130 kcal/mol), which might make them difficult to react with organic free radicals. However, it has not yet been determined how these solvents promote free radical reactions through weak interactions; and to the best of our knowledge, the aggregation of organic radicals in them has not been reported. The aggregation of organic molecules in the aqueous phase has been demonstrated to accelerate organic radical reactions and other electron transfer-involved catalytic reactions. However, the molecular structure and properties of polar fluorinated arenes and water are very different, so the rules summarized in the field of lipophilic and hydrophobic interactions of organic molecules cannot be directly applied to the system of polar fluorinated arenes, which are fluorocarbon/hydrocarbon-amphiphilic fluorous solvents. It is therefore of significant scientific interest to determine whether organic radicals have special aggregation behaviors in amphiphilic fluorous solvents such as polar fluorinated arenes. Further, understanding and revealing the behavior and rules of organic free radical aggregates in amphiphilic polar fluorinated arenes is very important for designing and developing new free radical reactions with these solvents in the future.

Recently, Tianfei Liu’s group have presented organic radical molecules aggregate in polar fluorinated arenes which exhibit fluorocarbon–hydrocarbon amphiphilicity. There was a significant effect of the intermolecular hydrogen bonding substituent (class II) and long-chain saturated hydrocarbon substituents (class III) on the aggregation of organic free radicals in the environments of polar fluorinated arenes. Concentration-dependent UV–vis measurements were performed to determine the CAgCs of both class II and class III organic radicals in these fluorinated arenes. TEM examination demonstrated that the aggregate particles were spherical in shape. Based on EPR studies, it has been demonstrated that the rotational speed of organic free radical molecules of class III is slower than that of class II molecules in their respective aggregates, and their aggregation is tighter than that of class II molecules. Further electrochemical studies determined how the particle size of the aggregates in polar fluorinated arenes changes with the radical's concentration, as well as showing in polar fluorinated arenes the aggregation behaviors of organic free radical molecules with intermolecular hydrogen bonding substituents can significantly increase the rate constant of their catalytic electro-oxidation of benzyl alcohol. The above elucidated SAgR can therefore be used as guidelines to adjust the performance of organic radical reactions in polar fluorinated arenes through the control of the aggregation of the corresponding radical molecules in these reaction media. Relevant achievements were published in Aggregate, 2024, DOI: 10.1002/agt2.543.