Inclusion Ability and Selectivity Behavior of Selected Fused Tricyclic Host Systems in the Presence of the Aromatic Amines Aniline, <i>N</i>-Methylaniline and <i>N,N′</i>-Dimethylaniline

Five host compounds (H1–H5), characterized by two fused tricyclic moieties which are covalently linked by means of diamino linker units, were investigated for their host ability for aniline (ANI), N-methylaniline (NMA) and N,N′-dimethylaniline (DMA). Each of these host species possessed enclathration ability for one or more of the guest solvents. Guest competition experiments were employed in order to assess whether these host compounds have any affinities for a particular guest solvent when presented with guest mixtures. It was demonstrated that the host selectivities were in the order ANI > DMA > NMA (H1), DMA/NMA > ANI (H2), NMA > DMA > ANI (H3), DMA > ANI > NMA (H4) and ANI > NMA > DMA (H5). Binary nonequimolar guest experiments were also conducted. It was shown that the 40:60 ANI/DMA (H1, K, 15.9, in favor of ANI), 60:40 ANI/DMA (H1, K, 9.9, ANI), 80:20 DMA/ANI (H3, K, 9.8, DMA) and 20:80 DMA/NMA (H4, K, 11.6, DMA) solutions may each be purified/separated using host–guest chemistry as an alternative method to the more usual fractional distillations. Thermal analyses revealed that the more preferred guests generally formed the more stable complexes. Of the 13 novel inclusion compounds prepared, only four (H1·DMA, H2·ANI, H2·NMA and H4·DMA) had adequate crystal quality for SCXRD analyses, which demonstrated that the low affinity of H2 for ANI was plausibly as a result of the significant (guest)N–H···C(host) short contact in H2·NMA, which was not present in H2·ANI.