Pseudorotaxanes of β -Cyclodextrin with Diamino End-functionalized Oligo-phenyl and -benzyl Compounds in Solution and in the Solid State

Abstract

β-Cyclodextrin forms a 1:1 host:guest inclusion complex ([2]pseudorotaxane) with 4-[2-(4-aminophenyl)ethyl]-benzenamine (1) in water as determined by 1D and 2D NMRexperiments. In the crystalline state, the structure of the complex has revealed a 2:2 stoichiometry, with two βCD molecules forming head-to-head dimers byH-bonds between the secondary O3 hydroxyl groups and enclosing two molecules of the guest. The packing mode of the present complex is encountered for the first time, since it does not belong to any of the four known packing types of the dimeric βCD inclusion complexes. On the other hand,N 1,N 4-bis(4-aminophenyl)-1,4-benzenedimethanamine 2), which is longer than 1 by a phenylene diamine unit, has not afforded any crystals, at present, however it threads into βCD in aqueous solution forming most probably [2]- and [3]pseudorotaxanes. The solution structures and the equilibria in this system are investigated.