Selectivity Considerations of the Roof-Shaped Host Compound trans-α,α,α′,α′-Tetrakis(4-chlorophenyl)-9,10-dihydro-9,10-ethanoanthracene-11,12-dimethanol in Mixed Anisoles

Abstract

The roof-shaped host compound trans-α,α,α′,α′-tetrakis(4-chlorophenyl)-9,10-dihydro-9,10-ethanoanthracene-11,12-dimethanol H1 was assessed for its selectivity behavior in various anisole (ANI) and ortho-, meta-, and para-methylanisole (oMANI, mMANI, and pMANI) mixtures. Guest/guest competition experiments in equimolar binary mixed guest solvents revealed remarkable host selectivities for ANI or mMANI when oMANI or pMANI was also present (90.7–95.3%). Furthermore, the oMANI/pMANI experiment proved H1 to be nearly completely selective for oMANI (91.8%). In ternary experiments, unexpectedly high selectivities toward ANI (82.6%) and mMANI (89.5%) were noted when the solutions were ANI/oMANI/pMANI and oMANI/mMANI/pMANI. Data obtained from binary competition experiments in which the molar quantity of each guest species was sequentially varied correlated exactly with these equimolar experiments, and high selectivity coefficients were calculated for ANI and mMANI when either oMANI or pMANI was also present. Unfortunately, SCXRD analyses on H1·ANI, 2H1·oMANI, and 2H1·pMANI revealed extreme guest disorder, and these could not be modeled. However, in H1·mMANI, the guest molecules were retained in the crystals by means of a close (host)C–H···π(guest) contact (2.97 Å, 143°). Finally, thermal analyses proved less useful in explaining the observed host selectivity. This work demonstrates that H1 is an extremely selective host compound in very many of the anisole mixtures used in this investigation and, therefore, is a highly suitable candidate to effectively separate and purify such mixtures.