Structural elucidation of liquid cyclooctatetraene and cyclooctadienes in inclusion crystals

Abstract

A disubstituted adamantane derivative having chloropyrimidine units (1) was utilized as a V-shaped host molecule to create inclusion crystals and to elucidate the molecular structures of the guests by X-ray crystallographic analysis. The crystallization of 1 and 1,3,5,7-cyclooctatetraene (a) in chloroform resulted in the formation of co-crystal (1a) with 2:3 host:guest complexation stoichiometry. Host 1 was assembled into a molecular network composed of double layer structures bearing channels where guest molecules (a) were accommodated. Co-crystals (1b, 1c) containing 1,3-cyclooctadiene (b) and 1,5-cyclooctadiene (c) were obtained at identical stoichiometry under similar conditions. The host molecules arrangement in both 1b and 1c was similar to that of 1a. In each case, guest molecules b and c were accommodated in the channels formed between the layers of the host molecules. In all co-crystals, the molecular structures of the guests a‒c, along with the host frameworks, were determined by crystallographic analysis.