Selectivity behaviour of two roof-shaped host compounds in the presence of xylene and ethylbenzene guest mixtures

Abstract

In the present investigation, we compare the host and selectivity behaviour of two compounds, namely α,α-diphenyl-9,10-dihydro-9,10-ethanoanthracene-11-methanol H1 and α,α-bis(p-chlorophenyl)-9,10-dihydro-9,10-ethanoanthracene-11-methanol H2, when recrystallized from both singular and mixed isomers comprising the xylenes (o-Xy, m-Xy and p-Xy) and ethylbenzene (EB) as potential guest solvents. H1 formed a complex with o-Xy alone in the single solvent experiments, while H2 included all four of these aromatic compounds. In equimolar guest competition experiments, H1 only crystallized from binary mixtures where o-Xy was present, and high selectivities for this guest were observed in these instances (84.5–93.7%). The other binary mixtures ultimately presented as gels, and H1 therefore failed to crystallize from these. In fact, this was true also for all ternary and quaternary experiments with H1, even when o-Xy was present. H2, on the other hand, consistently formed mixed complexes from all of the solutions employed. However, its selectivity for any particular guest was unremarkable. Guest/guest competition experiments using both equimolar and non-equimolar mixtures revealed that H1 may be employed to purify o-Xy/m-Xy, o-Xy/p-Xy and o-Xy/EB binary mixtures, especially when these solutions comprised 50% or more o-Xy (these experiments all favoured o-Xy). SCXRD analyses were employed to understand the moderate preference of H2 for o-Xy: only this guest was involved in contacts with the host compound, two in number, that measured significantly less than the sum of the van der Waals radii of the atoms involved. Additionally, Hirshfeld surface investigations showed that H2, through its chlorine atoms, was involved in the greater number of contacts with the preferred o-Xy guest compound. Thermal analyses, however, proved less useful in understanding these selectivity data.