Putting variable-sized alkanes into fixed-size hydrogen-bonded molecular flasks

Abstract

Confined alkanes within molecular capsules are an intriguing research area which were studied until now only by spectroscopic techniques, but never by single-crystal X-ray techniques [1-2]. We report here an extremely simple molecular flask made up by hydrogen-bonded tectons, which is used as a container for diammonium alkane chains of variable sizes. It was obtained in aqueous solution as well as in the crystalline state by mixing commercially available components: 1,3,5,8-pyrenetetrasulfonate (PTS), guanidinium (G) and 1,ω-diammonium-alkanes (Figure A). 1,10-diammoniumdecane 1 fits perfectly inside the capsule, while the 1,11-diammonium-undecane 2 and 1,12-diammonium-dodecane 3 chains are progressively compressed. Furthermore, it was observed that the compressed conformers may be stabilized by short dihydrogen contacts (Figure B).