Inclusion property of (R,R)-(-)-trans-2,3,-bis(hydroxydiphenylmethyl)-1,4-dioxaspiro[4,4]nonane for aromatic components

An optically active host molecule, (R,R)-(-)-trans-2,3-bis(hydroxydiphenylmethyl)-1,4- dioxaspiro4,4]nonane (1), is able to form inclusion complexes with nonpolar aromatic components such as benzene, toluene, p-xylene, mesitylene, and ethylbenzene. The host 1 crystallizes in the monoclinic space group C2 with a = 15.694(2), b = 9.326(2), c = 18.457(1) Å, = 10.34(1)°, and Z = 4. An inclusion complex (1-B) of 1 with benzene crystallizes in the orthorhombic space group P2₁2₁2 with a = 17.007(4), b = 19.670(5), c = 8.634(4) Å, and Z = 4. An inclusion complex (1-X) involving both 1 and p-xylene has the monoclinic space group P2₁ with a = 17.211(3), b = 20.143(3), c = 8.603(3) Å, = 92.64(2)°, and Z = 2. In the inclusion complexes, molecules of 1 are dimerized by intramolecular and intermolecular hydrogen bonds forming eight-membered (OH)₄ rings. The benzene and p-xylene molecules fit into the voids of the crystal packing of 1. In addition, the inclusion complexes are stabilized by van der Waals contacts between the hydrophobic sites. Thermal analysis of the inclusion complexes indicated that the number and the size of the alkyl group of the aromatic components affects the stability of the inclusion complexes.