C60-Mediated Molecular Shape Sorting: Separation and Purification of Geometrical Isomers

A supramolecular crystallization-based approach has been developed for the shape-dependent separation of geometrical isomers under near-ambient conditions. Difficulties to separate such isomers arise because of their very similar physical properties. The present approach relies on the ability of C-60 to preferentially form solvate crystals with molecules of a specific geometry. Subsequently, these molecules are released upon mild heating to regenerate pure C-60. By taking isomers of xylene and trimethylbenzene (TMB) as examples, we show that one of the isomers can be extracted from the rest with very high purity. To separate TMB isomers, a new C-60-1,3,5-TMB solvate was developed, which led to the isolation of isomer purities greater than 99.6%. Versatility, a low operating temperature of approximately 100 degrees C, a separation efficiency of more than 10 weight % of C-60 per cycle, and reagent recyclability makes this a promising molecular shape-sorting approach.