Complementary host behaviour of trans-cyclohexane-1,4-diamine derivatives during recrystallization processes from mixed anilines

Abstract

trans-N,N′-Bis(9-phenyl-9-xanthenyl)cyclohexane-1,4-diamine (1,4-DAX) and trans-N,N′-bis(9-phenyl-9-thioxanthenyl)cyclohexane-1,4-diamine (1,4-DAT) proved to be highly effective host compounds for the enclathration of aniline (ANI), N-methylaniline (NMA) and N,N-dimethylaniline (DMA) guest solvents: only DMA was not included and only when using 1,4-DAT. When the host compounds were recrystallized from mixtures of these guests, it was revealed that host selectivities were in the order NMA > ANI > DMA and NMA > DMA > ANI for 1,4-DAX and 1,4-DAT, respectively. Single crystal diffraction experiments were employed to identify the host⋯guest interactions responsible for guest retention in these complexes, while thermal analyses proved futile for the determination of their relative thermal stabilities since most of them displayed poor stability even at room temperature. The selectivity data presented here complement the results obtained when the host compounds employed were 1,2-DAX and 1,2-DAT, as per a previous submission, where DMA was significantly preferred. Since NMA and DMA may be prepared from ANI, the resultant products often have one or more of these anilines present as impurities. This work therefore demonstrates that by utilizing the appropriate host compound, these solvents may be purified through host‒guest chemistry principles.