Comparing the effect of selected substituent changes on host ability and selectivity in four xanthenyl-type host compounds in the presence of cyclohexanone and methylcyclohexanone isomers
- 55 Downloads
Four related xanthenyl and thioxanthenyl host compounds, N,N′-bis(9-phenyl-9-thioxanthenyl)ethylenediamine (H1), N,N′-bis(9-phenyl-9-xanthenyl)ethylenediamine (H2), N,N′-bis(9-cyclohexyl-9-thioxanthenyl)ethylenediamine (H3) and N,N′-bis(9-cyclohexyl-9-xanthenyl)ethylenediamine (H4) were synthesized and compared for their host ability and selectivity in the presence of cyclohexanone and the methylcyclohexanone isomers. Surprisingly, only H1 was an effective host compound in these conditions, clathrating all four potential guest solvents; H2 failed to crystallize from these compounds, while both H3 and H4 included only cyclohexanone, also failing to crystallize from the methylcyclohexanone isomers. H1 was further assessed for any selectivity when presented with mixtures of these guests, and a host selectivity order of 2MeCy (67.6%) > 3MeCy (23.1%) > 4MeCy (9.3%) was observed, while the addition of cyclohexanone to these experiments resulted in an adaptation of this order [Cy (39.2%) = 2MeCy (41.7%) ≫ 3MeCy (13.5%) > 4MeCy (5.6%)]. SCXRD analysis demonstrated that the host packing in H1·Cy, H1·2MeCy and H1·3MeCy was isostructural (monoclinic, P21/n), while H1·4MeCy crystallized in a different crystal system (triclinic, P − 1). All four guests experienced (host)C–H···O–C(guest) interactions, with Cy, a preferred guest, experiencing the shortest of these (2.40 Å, 167°). Thermal analyses showed the preferred guests (cyclohexanone and 2-methylcyclohexanone) to form complexes with enhanced thermal stabilities relative to the other two (3- and 4-methylcyclohexanone) (Tp 129.8 and 99.0 °C vs. 97.9 and 95.3 °C, respectively). This investigation has demonstrated that subtle changes in the structures of these xanthenyl- and thioxanthenyl-type host systems may instigate dramatic host behaviour changes in the presence of these cyclohexanone guest solvents.
KeywordsCyclohexanone Isomers Host–guest chemistry Inclusion Supramolecular chemistry Xanthenyl
Financial support is acknowledged from the Nelson Mandela University and the National Research Foundation (NRF). L. Bolo is thanked for thermogravimetric analyses.
- 3.Steed, J.W., Turner, D.R., Wallace, K.: Core Concepts in Supramolecular Chemistry and Nanochemistry. Wiley, Weinheim (2007)Google Scholar
- 13.Barton, B., de Jager, L., Hosten, E.C.: A comparison of the behaviour of two closely related xanthenyl-derived host compounds in the presence of vaporous dihaloalkanes. J. Incl. Phenom. Macrocycl. Chem. 92(1), 181 (2018)Google Scholar
- 15.Barton, B., McCleland, C.W., Caira, M.R., de Jager, L., Hosten, E.C.: Crystal X-ray diffraction and molecular modelling considerations elucidate the factors responsible for the opposing host behaviour of two isostructural xanthenyl- and thioxanthenyl- derived host compounds. Cryst. Growth Des. 19, 2396 (2019)CrossRefGoogle Scholar
- 17.Barton, B., Senekal, U., Hosten, E.C.: Compounds N,N′-bis(9-cyclohexyl-9-xanthenyl)ethylenediamine and its thio derivative, N,N′-bis(9-cyclohexyl-9-thioxanthenyl)ethylenediamine, as potential hosts in the presence of xylenes and ethylbenzene: conformational analyses and molecular modelling considerations. Tetrahedron 2, 2 (2019). https://doi.org/10.1016/j.tet.2019.04.065 CrossRefGoogle Scholar
- 18.Barton B.: Host-guest chemistry: the synthesis and assessment of host compounds based on the 9-arylxanthenyl and related systems, PhD thesis, University of Port Elizabeth, Port Elizabeth (1997)Google Scholar
- 19.Mercury 3.10.2 (Build 189770), http://www.ccdc.cam.ac.uk/mercury/ [Accessed 2019.]
- 20.Bruker, A.: APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, WI (2007)Google Scholar