Inclusion crystals of V-shaped host molecules having trialkoxybenzene moieties with a carborane or benzoquinone derivative

Abstract

Disubstituted adamantanes having pyrogallol derivatives as V-shaped host molecules were synthesized to prepare complexes with carboranes, which are representative spherical guest molecules for macrocyclic compounds, including calixarenes and cyclotriveratrylenes. The crystallization of o-carborane (a) and 1,3-bis(3,4,5-trimethoxyphenyl)adamantane (1) in toluene resulted in the formation of inclusion crystals (1a) in a 1 : 1 ratio. X-ray crystallographic analysis revealed that two oxygen atoms in 1 interact with two hydrogen atoms of a through CH⋯O interactions to afford the complexes. In the case of 1,3-bis(3,4,5-triethoxyphenyl)adamantane (2), no inclusion crystal was obtained due to steric hindrance of the ethyl groups. Furthermore, the crystallization of 1 and a benzoquinone derivative (b) provided reddish crystals (1b) with a 1 : 2 host : guest complexation stoichiometry, where lone pair⋯π interactions in the complexes were observed in addition to donor–acceptor interactions.