Dihydrogen Bond Interaction Induced Separation of Hexane Isomers by Self-Assembled Carborane Metallacycles

Herein, we describe how to utilize dihydrogen bond interactions to achieve alkane recognition and hexane isomer separation. A series of metallacycles based on carborane backbones are presented herein, revealing interdependent B–Hδ−···Hδ+–C proton–hydride interactions. The metallacycles take advantage of these dihydrogen bond interactions for the separation of hexane isomers. We show that the metallacycle 3a, bearing 1,4-di­(4-pyridyl)­benzene (DPB), can produce n-hexane with a purity of >99% in a single adsorption–desorption cycle from an equimolar mixture of all five isomers of hexane. The isomers 2-methylpentane and 3-methylpentane can be selectively absorbed by metallacycle 4a, which bears 1,2-di­(4-pyridyl)­ethylene (DPE). The size of the metallacycle, C–H···π interactions, and particularly B–Hδ−···Hδ+–C interactions are the main forces governing the extent of hexane recognition. This work provides a promising principle for the design of supramolecular coordination complexes (SCCs) for the separation of alkanes.