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 Ξ±1), monoclinic, C2/c, a= 16.827(2), b= 15.212(3), c= 10.708 Γ…, Ξ²= 97.01(1)Β°, V= 2721 Γ…3, Z= 4; 2(polymorph Ξ±2), triclinic, P[1 with combining macron], a= 8.807(2), b= 10.687(6), c= 16.263(3)Γ…, Ξ±= 100.97(3)Β°, Ξ²= 91.47(2)Β°, Ξ³= 113.02(3)Β°, V= 1375 Γ…3, Z= 2; 9, monoclinic, P21/n, a= 12.781(3), b= 7.773(2), c= 28.405(17)Γ…, Ξ²= 103.01Β°, V= 2749 Γ…3, 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 Ξ±2-polymorph of 2 resulted in a gauche conformation of the hydroxy moieties unlike the Ξ±1-polymorph of 2 which is anti. The packing factors are 17.00, 17.18 and 18.09 Γ…3 per non-hydrogen atom for 2(Ξ±1), 2(Ξ±2) and 9, respectively.
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