Absorption of Hydrogen Bond Donors by Pyridyl Bis-Urea Crystals

Abstract

A one-dimensional crystalline solid built from pillars of self-assembled bis-urea pyridyl macrocycles affords a close packed structure with no pores. These organic pillars contain unsatisfied urea oxygen lone pairs that can be used to drive the absorption of alcohols including trifluoroethanol, phenol, pentafluorophenol, and ethylene glycol to give well-ordered host:guest complexes with repeatable stoichiometry. The driving force for reversible solid transitions appears to be the formation of hydrogen bonds between the guest and an unsatisfied hydrogen bond acceptor, which is a lone pair of the urea oxygen. Halogen bonding with the electrophilic iodide in pentafluoroiodobenzene can also drive absorption by the host to give a well-ordered host:guest complex. These results suggest that the organic solid-state is surprisingly dynamic and may have potential applications for sorbents.