Hydrogen-bonded chains of α,ω-diaminoalkane and α,ω-dihydroxyalkane guest molecules lead to disrupted tunnel structures in urea inclusion compounds

Abstract

Structural features of the urea inclusion compounds containing 1 ∶ 1 mixtures of α,ω-diaminoalkane and α,ω-dihydroxyalkane guest molecules, reported in this paper, provide interesting contrasts to those of conventional urea inclusion compounds. All the α,ω-diaminoalkane/α,ω-dihydroxyalkane/urea inclusion compounds reported have a hydrogen-bonded chain of alternating α,ω-diaminoalkane and α,ω-dihydroxyalkane guest molecules, which is surrounded by urea molecules in a manner that bears some resemblance to the conventional urea tunnel structure, but with the urea–urea hydrogen bonding scheme disrupted by the formation of N–H⋯O hydrogen bonds between NH2 groups of the urea molecules and OH groups of the α,ω-dihydroxyalkane molecules. As a consequence, the guest and host components have the same periodicity, and these inclusion compounds are commensurate, in contrast to conventional urea inclusion compounds. So far, attempts to prepare α,ω-diaminoalkane/α,ω-dihydroxyalkane/urea inclusion compounds for α,ω-dihydroxyalkanes longer than 1,3-dihydroxypropane have been unsuccessful, suggesting that there may be an upper limit to the length of the α,ω-dihydroxyalkane component in this family of structures.