New synthesis and complexing properties of p-tert-butyldihomooxacalix[4] arene. Structure of its 1:2 complex with tetrahydrofuran

A new method is described for the synthesis of isolated p-tert-butyldihomooxacalix[4]arene (CALO) with a 24% yield. The ability of CALO to form complexes in the solid state with small neutral molecules has been studied; the potential guests were common solvents bearing various chemical functions. The powder obtained after evaporation of the solvent has been characterized by the X-ray powder diffraction technique. Analysis of the patterns shows the non-complexation of linear alkanes and alcohols, but formation of complexes when the guest is cyclic or when it bears an amine or a ketone function. As illustration of the possible arrangement of molecules in complexes, the structure of the 1 : 2 complex with tetrahydrofuran (THF) is presented: the crystals are monoclinic, space group P2(1)/c, a = 9.459(2) Angstrom, b = 17.286(2) Angstrom, c = 30.469(6) Angstrom, beta = 92.52(2)degrees, V = 4977(2) Angstrom(3), Z = 4, D-c = 1.099 Mg m(-3), lambda = 1.54178 Angstrom, mu = 5.6 cm(-1), R = 0.086 for 3590 reflections with F > 4 sigma (F); one of the THF molecules is inside the cavity of the macrocycle, while the other, in the interhost space, exhibits disorder, In the CALO molecule, three out of the four tert-butyl groups are disordered which may induce the disorder of the THF molecule.