Complexation with diol host compounds. Part 10. Synthesis and solid state inclusion properties of bis(diarylhydroxymethyl)-substituted benzenes and biphenyls; X-ray crystal structures of two host polymorphs and of a non-functional host analogue

Abstract

A new family of host molecules where the molecular axis of usual ‘wheel-and-axle’ compounds is replaced by aromatic units is described. These diol hosts form crystalline inclusions with a variety of uncharged organic molecules mainly of a polar nature (53 different copecies). The formation and stoichimetry depend in a systematic manner on structural parameters of the host allowing these hosts to be more selective than the parent compounds. Non-hydroxylic analogues do not function as host molecules. The crystal structures of two polymorphs of host compound 2 and of the inefficient compound 9 have been studied. Crystal data: 2(polymorph α₁), monoclinic, C2/c, a= 16.827(2), b= 15.212(3), c= 10.708 Å, β= 97.01(1)°, V= 2721 ų, Z= 4; 2(polymorph α₂), triclinic, P, a= 8.807(2), b= 10.687(6), c= 16.263(3)Å, α= 100.97(3)°, β= 91.47(2)°, γ= 113.02(3)°, V= 1375 ų, Z= 2; 9, monoclinic, P2₁/n, a= 12.781(3), b= 7.773(2), c= 28.405(17)Å, β= 103.01°, V= 2749 ų, Z= 4. Alignment of the axis of the molecular backbones was observed in all structures. Formation of host-host hydrogen bonds in the case of the α₂-polymorph of 2 resulted in a gauche conformation of the hydroxy moieties unlike the α₁-polymorph of 2 which is anti. The packing factors are 17.00, 17.18 and 18.09 ų per non-hydrogen atom for 2(α₁), 2(α₂) and 9, respectively.