Complementary host behaviour of three anthracenyl-derived roof-shaped compounds in mixed pyridines

Abstract

Dimethyl trans-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylate (H1), trans-α,α,α′,α′-tetraphenyl-9,10-dihydro-9,10-ethanoanthracene-11,12-dimethanol (H2) and trans-α,α,α′,α′-tetra(p-chlorophenyl)-9,10-dihydro-9,10-ethanoanthracene-11,12-dimethanol (H3) were investigated for their host ability for pyridine and 2-, 3- and 4-methylpyridine (Py, 2MePy, 3MePy and 4MePy) by means of recrystallization experiments from these organic solvents. Each one was enclathrated with the exception of H2 in 4MePy where a gel resulted in the experiment. Subsequently, guest/guest competition experiments were conducted, and it was noted that each of the three host compounds possessed complementary selectivities: H1 preferred Py, H2·3MePy and H3·2MePy in such conditions. H1 was also observed to extract large amounts of Py from a 70.1% Py/29.9% 4MePy mixture and the selectivity coefficient, K, was 11.9 (in favour of Py), ensuring that such mixtures may be separated by means of host–guest chemistry strategies. Single crystal X-ray diffraction experiments and thermal analyses were employed, where possible, in order to explain these selectivity observations by investigating both the host⋯guest interactions present in the complexes and their relative thermal stabilities, respectively.