Inclusion abilities towards hexyne isomers by co-crystallization with extended V-shaped host molecule

Disubstituted adamantane derivative possessing chloropyrazine (1) was synthesized and used as an extended V-shaped host molecule for the preparation of inclusion crystals containing hexyne isomers. The crystallization of 1 with 3-hexyne or 2-hexyne in chloroform provided co-crystals (1a, 1b) with 1:2 host:guest complexation stoichiometry, whereas guest-free crystals (1c) were produced in the case of 1-hexyne. In the co-crystals, the dimers built from 1 through CH···O interaction were arranged into a molecular network through multiple intermolecular interactions, and the guest molecules were accommodated within the cavity built from four molecules of 1. From the crystallization of equimolar binary mixtures of 3-hexyne or 2-hexyne and 1-hexyne in the presence of 1, co-crystals 1a and 1b were supplied, respectively. Competition experiments revealed that the selectivity order of 1 for the hexyne isomers was 3-hexyne and 2-hexyne ≫ 1-hexyne.