Synthesis of an Open‐Cage C₆₀ Derivative with a Double Stopper

Abstract

The construction of a suitable stopper on a C60 orifice is of importance to prevent the release of once‐encapsulated chemical species. However, a single stopper on a large orifice is in usual not sufficient to retain a small molecule within the C60 cavity. In this work, we introduced a double stopper, constituted of two hydroxy groups, on a huge orifice with a ring‐atom count of 18 by a reduction using BH3⋅THF. The resulting double stopper was demonstrated to effectively isolate an argon atom inside the cavity so that the argon was retained even under mass spectrometric conditions at 200 °C. The structure of the open‐cage C60 derivative with the double stopper was confirmed by X‐ray diffraction analysis, showing a dimeric configuration via intermolecular hydrogen‐bondings. The dimerization behavior was also studied in solution.