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

Abstract

A new method is described for the synthesis of isolatedp-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 groupP2₁/c,a=9.459(2) Å,b=17.286(2) Å,c=30.469(6) Å, β=92.52(2)^o,V=4977(2) ų,Z=4,D _c=1.099 Mg m⁻³, λ=1.54178 Å, μ=5.6 cm⁻¹,R=0.086 for 3590 reflections withF>4σ (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 fourtert-butyl groups are disordered which may induce the disorder of the THF molecule.