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

Structural features of the urea inclusion compounds containing 1 : 1 mixtures of alpha,omega-diaminoalkane and alpha,omega-dihydroxyalkane guest molecules, reported in this paper, provide interesting contrasts to those of conventional urea inclusion compounds. All the alpha,omega-diaminoalkane/alpha,omega-dihydroxyalkane/urea inclusion compounds reported have a hydrogen-bonded chain of alternating alpha,omega-diaminoalkane and alpha,omega-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 center dot center dot center dot O hydrogen bonds between NH2 groups of the urea molecules and OH groups of the a,w-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 alpha,omega-diaminoalkane/alpha,omega-dihydroxyalkane/urea inclusion compounds for alpha,omega-dihydroxyalkanes longer than 1,3-dihydroxypropane have been unsuccessful, suggesting that there may be an upper limit to the length of the alpha,omega-dihydroxyalkane component in this family of structures.