Host Compound DED: Guest Accommodation Type, Noncovalent Host···Guest Interactions, Crystal Densities, and Thermal Stabilities Ensure High Host Selectivities for 4-Methylanisole in Anisole and Methylanisole Mixtures

Abstract

trans-9,10-Dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid (DED), dimethyl trans-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylate (H1), and trans-α,α,α′,α′-tetraphenyl-9,10-dihydro-9,10-ethanoanthracene-11,12-dimethanol (H2) formed complexes with anisole (ANI) and 2-, 3-, and 4-methylanisole (2-, 3-, and 4-MA) in single-solvent recrystallization experiments. DED was observed to possess an overwhelming selectivity for 4-MA when recrystallized from equimolar binary, ternary, and quaternary mixtures (82.2–99.3%) and nonequimolar binary solutions where this guest species was present. It was therefore demonstrated that DED may serve as an efficient host compound for the separation and purification of many of the mixtures employed in this investigation; extremely high K values (K is a measure of the selectivity of the host compound) were calculated in many instances (137.9, 190.7). However, the selectivity behavior of H1 and H2 in analogous experimental conditions could not be established owing to the extremely slow (months) crystal growth process from these mixtures. Single-crystal X-ray diffraction (SCXRD) experiments revealed that 4-MA interacted with DED via two short stabilizing (host)­C–O···π­(guest) contacts (3.2782(17), 3.3780(17) Å, 145, 138°). This interaction type was absent in 2­(DED)·3-MA and weaker in 2­(DED)·2-MA (and only one interaction of this kind was present in the latter complex). Additionally, the crystal density of 2­(DED)·4-MA (1.335 g·cm–1) was greater than those of 2­(DED)·3­(ANI) (1.277 g·cm–1), 2­(DED)·2-MA (1.257 g·cm–1), and 2­(DED)·3-MA (1.283 g·cm–1), alluding to a tighter packing in the complex with the preferred guest species owing to the shorter contacts in this crystal. The higher density was also explained by a significantly shorter intermolecular (host)­π···π­(host) interaction in the 4-MA-containing complex. Furthermore, 4-MA experienced more constricted channel accommodation compared with ANI, 2- and 3-MA. Finally, 2­(DED)·4-MA possessed the greater thermal stability (the onset of the guest release process, T on = 101.8 °C) compared with 2­(DED)·3­(ANI) (unstable at room temperature), 2­(DED)·2-MA (T on = 90.4 °C), and 2­(DED)·3-MA (T on = 85.3 °C).

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

“…13,14 The roof-shaped compounds derived from anthracene and fumaric acid were designed by Edwin Weber in 1996 and were shown to be highly effective host compounds for the complexation of a large variety of guest species. 15 In subsequent investigations in our own laboratories, these types of host compounds were demonstrated to possess enhanced selectivities in aromatic positional isomeric mixtures such as the xylenes (and ethylbenzene), [16][17][18] dichlorobenzenes, 19 the MePys (and Py), 20 methylanisoles (and anisole), 21,22 and bromoanisoles (and anisole). 23 In many of these recrystallization experiments that employed guest mixtures, host selectivity coefficients (K) were significant (greater than 10), alluding to the feasibility of separating such mixtures on a practical platform, as reported by Nassimbeni and co-workers.…”

Host behaviour of two tricyclic fused systems in mixed anisole guest solvents

“…In our own laboratories, trans-9,10dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid and (R,R)-(−)-2,3-dimethoxy-1,1,4,4-tetraphenylbutane-1,4-diol were presented with the mixed anisole guest compounds and were revealed to possess enhanced selectivities for 4MA and ANI, respectively. 15,16 Host-guest chemistry is that field of science that falls into the broader supramolecular chemistry area, and successful separations of isomers rely upon the appointed host compound displaying selectivity for one particular guest when presented with isomeric mixtures. This, in turn, is more usually reliant on noncovalent interactions between the host and guest species to furnish stable complexes (also known as inclusion compounds) with optimal host-guest packing modes.…”

“…In our own laboratories, trans -9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid and ( R , R )-(−)-2,3-dimethoxy-1,1,4,4-tetraphenylbutane-1,4-diol were presented with the mixed anisole guest compounds and were revealed to possess enhanced selectivities for 4MA and ANI, respectively. 15,16…”

Exploring the host compound dynamics of 1,4-phenylene-bis(di-p-fluorophenylmethanol) in mixed pyridines

“…The focus in our laboratories has been on the latter application type. It has been demonstrated that this field of science may be employed to separate, for example, the C8 aromatic fraction of crude oil, the methylpyridines, the dichlorobenzenes, the methylanisoles, various anilines, and the toluidines, from one another [17][18][19][20][21][22][23]. Successful host compounds were derived from xanthone, thioxanthone, anthracene and tartaric acid.…”