Behaviour of host compounds 1,2-DAX and 1,2-DAT in the presence of mixed xylene and ethylbenzene guest solvents, and comparisons with their 1,4 host derivatives

Abstract

trans-N,N′-Bis(9-phenyl-9-xanthenyl)cyclohexane-1,2-diamine (1,2-DAX) and trans-N,N′-bis(9-phenyl-9-thioxanthenyl)cyclohexane-1,2-diamine (1,2-DAT) were recrystallized independently from each of the xylene isomers (o-Xy, m-Xy and p-Xy) and ethylbenzene (EB) to ascertain their host ability for these guest solvents. It was thus shown that both compounds were capable of forming complexes with each guest species. The hosts were then recrystallized from various mixtures of these solvents in order to establish if they possessed any preference for a particular guest species from the series, with the view to possibly offering an alternative separation strategy for such mixtures using host‒guest chemistry principles and 1,2-DAX and/or 1,2-DAT. In so doing, each host compound was revealed to have comparable selectivities, favouring o-Xy and discriminating against p-Xy. This contrasted markedly with earlier findings reported for related host compounds 1,4-DAX and 1,4-DAT, which both preferred p-Xy whilst displaying a bias against o-Xy. We subsequently calculated the void volumes that remained after removal of each of the guest species from the packing calculation and found that the preferred guests always occupied the smallest volumes compared with guests that were less favoured (for complexes of 1,2-DAX, 1,2-DAT, 1,4-DAX and 1,4-DAT). This finding implied that the favoured guest species, here, experienced a tighter packing than any of the other solvents from the series. Additional to this information, data from single crystal diffraction and thermal analyses for each complex are also provided here.