trans-N,N′-Bis(9-phenyl-9-xanthenyl)cyclohexane-1,2-diamine and its thioxanthenyl derivative as potential host compounds for the separation of anilines through host‒guest chemistry principles

In this work, we investigate the potential of separating mixtures of the guest solvents aniline (ANI), N -methylaniline (NMA) and N , N -dimethylaniline (DMA) by means of host‒guest chemistry principles employing two novel host compounds, namely 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). These aniline solvents may exist in such mixtures since NMA and DMA are often prepared from ANI by alkylation methods, and reaction yields are seldom quantitative. Owing to their similar boiling points, ranging from 184 to 196 ºC, the more usual distillation techniques for their separation are challenging. After recrystallization experiments of the two host compounds from various combinations of these anilines, it was revealed that host‒guest chemistry certainly has the potential to serve as an alternative separation strategy for such mixtures. Equimolar ANI/DMA solutions proved most successful, where both 1,2-DAX and 1,2-DAT showed near-quantitative selectivity for DMA (90%). Both single crystal diffraction and thermal analyses were employed in order to understand the preferential behaviour displayed by each host compound.