Homodiselenacalix[4]arenes: Molecules with Unique Channelled Crystal Structures

Abstract

A synthetic route towards homodiselenacalix[4]arene macrocycles is presented, based on the dynamic covalent chemistry of diselenides. The calixarene inner rim is decorated with either alkoxy or tert-butyl ester groups. Single-crystal X-ray analysis of two THF solvates with methoxy and ethoxy substituents reveals the high similarity of their molecular structures and alterations on the supramolecular level. In both crystal structures, solvent channels are present and differ in both shape and capacity. Furthermore, the methoxy-substituted macrocycle undergoes a single-crystal-to-single-crystal transformation during which the molecular structure changes its conformation from 1,3-alternate (loaded with THF/water) to 1,2-alternate (apohost form). Molecular modelling techniques were applied to explore the conformational and energetic behaviour of the macrocycles.

Keywords: calixarenes; covalent chemistry; crystal engineering; molecular dynamics; selenium.