Trityl Group as an Crystal Engineering Tool for Construction of Inclusion Compounds and for Suppression of Amide NH···O═C Hydrogen Bonds

It has been found that ditrityl derivatives of (R,R)-N,N'-cyclohexane-1,2-diyldiacetamide and their analogues invariably form crystals that possess inclusion properties. Enantiopurity of crystals is not a prerequisite for inclusion properties. The molecules form either two- or three-component inclusion compounds, in which hosts and guests are connected by hydrogen bonds specific for the included guest molecules but always involving the carbonyl groups of the host as acceptors. The association mode of the host molecules undergoes certain changes depending on the chemical modification of the host molecule, the type of included solvent molecule (protic/nonprotic), and whether the crystals are two- or three-component. Despite the potential for hydrogen bonding of the amide groups, no direct hydrogen bonding between the amide units of the host was observed in any of the reported structures allowing classification of a trityl group as a protection group of the amide NH functionality in crystal engineering. X-ray diffraction combined with electronic circular dichroism measurements supported by theoretical calculations provide full information about structural dynamics of the chiral trityl derivatives in both the solid state and solution.