Polymorphism and Structure in a Pentamorphic Guest−Host Material:  The Tris(5-acetyl-3-thienyl) Methane (TATM) Inclusion Compound with 1,3-Dichloropropane

In this work, we describe the preparation and structural properties of five polymorphs of the 1G:2H, 1,3-dichloropropane/tris (5-acetyl-3-thienyl) methane (TATM) inclusion compound. A number of different preparative methods were used to give products whose structures were solved by single-crystal X-ray diffraction. In addition, solid-state ¹³C NMR spectroscopy and powder X-ray diffraction (PXRD) were used for bulk phase identification. On the basis of the unit cell parameters determined from single crystal X-ray diffraction experiments, the PXRD results were used to resolve the products as being from either pure or mixed phases. In four of the five forms, the host TATM molecules have similar torsional conformations and share a common layered motif. The guest molecules are disordered and reside in cages or channels that are formed from the stacking of these layers. In the fifth form, the conformation of the TATM host molecules differ significantly, and the disordered guests reside in a pronounced zigzag channel. Apparently, slightly different conformations for the host and the flexile guest give structures that differ little in energy. The results suggest that minor changes in synthetic procedures can have a profound effect on the structure of the resulting crystalline product. Some of the structures presented here are closely related to other structures previously reported for TATM inclusion compounds with a variety of guests, suggesting that this may be a particularly rich area for studying polymorphism.