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 C60 to preferentially form solvate crystals with molecules of a specific geometry. Subsequently, these molecules are released upon mild heating to regenerate pure C60 . 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 C60 -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 °C, a separation efficiency of more than 10 weight % of C60 per cycle, and reagent recyclability makes this a promising molecular shape-sorting approach.