Host Behavior of N,N′-Bis(9-phenyl-9-thioxanthenyl)ethylenediamine in the Presence of Aromatic and Aliphatic Five-Membered Heterocyclic Guests: Selectivity Correlations with Hirshfeld Surface Analyses

The crystalline compound N,N′-bis(9-phenyl-9-thioxanthenyl)ethylenediamine (1) was assessed for its host ability in the presence of eight five-membered ring heterocyclics, namely, saturated tetrahydrofuran, tetrahydrothiophene, and pyrrolidine, and aromatic equivalents furan, thiophene, and pyrrole and, additionally, imidazole and pyrazole. Host 1 clathrated all six mono-heteroatomic guests, while complexes were not formed with imidazole and pyrazole. Specifically designed guest/guest competition experiments revealed that 1 preferred both the saturated heterocyclics (relative to the aromatics) and the sulfur-containing guests (in both saturated and aromatic series) followed by oxygen and nitrogen (S > O > N). The affinity of the host for the saturated guests was explained by means of a consideration of the applicable host···guest interactions, obtained from single crystal diffraction analyses, where these guests were observed to experience a greater variety and number of these interaction types relative to the aromatic guests. The host selectivity order for the various heteroatoms (S > O > N) was clarified unfailingly when investigating, quantitatively, the percentage of the guest heteroatom···host interactions in each complex by means of Hirshfeld surface analyses. Thermal experiments carried out on all six inclusion compounds provided further illumination for some of the observations made from the competition experiments.