Crystal structures of mono-, di-, and tri(p-tert-butyl)-thiacalix[4]arenes: Dimeric self-inclusion behavior

X-Ray crystal structures of the mono-, di-, and tri(p-tert-butyl)-substituted thiacalix[4]arenes (TC4As; 1, 2, and 3, respectively) have been determined. TC4As 1-3 adopt a cone conformation and form dimeric self-inclusion units in such a manner that phenol moieties are inserted into the cavity of each molecule. In all the crystal structures of 1-3, lateral face-to-face interactions exist between the phenol rings that do not bear a tert-butyl substituent, and seemingly, this molecular assembly stabilizes the formation of self-inclusion. TC4As 1 and 2 adopt a cone conformation with C₂ symmetry, leading to the formation of rim-to-rim intermolecular hydrogen bonds so as to link the dimeric units up and down. On the other hand, 3 adopts a regular cone conformation with C ₄ symmetry to form cyclic hydrogen bonds within the rim part of TC4A.