Selective Inclusion of Cyclohexanone from a Mixture with Cyclohexanol Using 1,3-Diaminocalix[4]arene Crystals

Abstract

1,3-Diaminocalix[4]arene 3 crystals selectively include cyclohexanone over cyclohexanol, which is one of the hard-to-separate organic molecules, from their decane solution. X-ray structural analysis of 3·Cy=O and 3·Cy–OH revealed that a guest molecule is included in the cavity of the host molecule to form the same 1:1 (host/guest) inclusion complexes. 3·Cy=O is observed to be slightly more stable than 3·Cy–OH through thermogravimetric analysis of inclusion crystals. A noncompetitive inclusion experiment from decane solution revealed that the inclusion of cyclohexanone into the crystals of 3 is kinetically and thermodynamically more favorable than that of cyclohexanol. A comparison of the inclusion behavior of each guest molecule from decane and water revealed that the preferential inclusion of cyclohexanone seems to be amplified by the inhibition of the inclusion of cyclohexanol by the formation of aggregates with intermolecular hydrogen bonds in a non-polar solvent.