Benita Barton

Clathrates of TETROL: Further Aspects of the Selective Inclusion of Methylcyclohexanones in Their Energetically Unfavorable Axial Methyl Conformations.

(+)-(2R,3R)-1,1,4,4-Tetraphenylbutane-1,2,3,4-tetraol (TETROL) functions as a highly efficient host for the inclusion of cyclohexanone and 2-, 3-, and 4-methylcyclohexanone, all with 1:1 host/guest ratios. Most extraordinarily, the 3- and 4-methyl isomers are uniquely included in their higher energy axial methyl conformations rather than as their more energetically favorable equatorial analogues. In contrast, 2-methylcyclohexanone is included more conventionally in the equatorial methyl conformation. During recrystallization of TETROL from racemic 2- and 3-methylcyclohexanone, some preference is shown by the host for the (R)-enantiomer. In the latter case, this is attributed to a much stronger H-bond between a hydroxyl group of TETROL and the carbonyl group of the (R)-enantiomer (O···O 2.621(2) Å) compared with a significantly weaker H-bond to the (S)-enantiomer (3.125(8) Å). In the former instance, hydrogen-bond strengths to both enantiomers are similar, but the (R)-enantiomer engages in three (guest)CH···π(host) and three (guest)H···Car(host) contacts, whereas fewer interactions of these types are observed for the (S)-enantiomer. Calculations of geometries of the guest cyclohexanones were determined at the MP2/6-311++G(2df,2p) level and compared with those obtained at the G3(MP2) level. Finally, an interesting correlation between crystal packing indices for the three methylcyclohexanone clathrates and their respective desolvation onset temperatures was identified.

Synthesis and crystal structure of a novel camphor based thioacetal

The synthesis of the very first example of a thioacetal containing two camphor skeleta is described. The acetal was prepared by treating 10-mercapto-iso-borneol with camphorquinone and its stereochemistry confirmed by NMR spectroscopy and X-ray crystallography.

Synthesis of N,N′-bis(9-phenylxanthen-9-yl)ethylenediamine and an investigation of its host–guest inclusion potential

The novel amine, N,N′-bis(9-phenylxanthen-9-yl)ethylenediamine 1, was synthesized by treating 9-phenylxanthen-9-ylium perchlorate with ethylenediamine. Its host potential was assessed by allowing it to crystallise from a range of organic solvents (single and binary mixtures), of which several were found to be included. The stoichiometries of these host–guest complexes were determined through 1H-NMR analysis and their stabilities assessed through thermal analysis. Single crystal X-ray crystallography was used to elucidate the crystal structure of the 1∶1 1·THF inclusion complex. It was found that only one of the two amine moieties of the host functions as a donor, forming a nearly linear hydrogen bond to the oxygen atom of the guest molecule. Each THF molecule is effectively surrounded by host molecules so that the THF molecules are found to occupy discrete “cavities” within the host lattice. The activation energy associated with desolvation of the 1·THF complex was determined through thermal analysis and was found to decrease as desolvation progressed.

14-Hydroxy-14-phenyldibenzo[a,j]xanthene as a lattice host: crystal and molecular structure of its (1:1) complex with diethyl ether

The title compound 14-hydroxy-14-phenyldibenzo[a,j]xanthene 1 formed a (1:1) complex with diethyl ether. 1,4-Dioxane was also enclathrated, but with a variable stoichiometric ratio. Single crystal X-ray crystallography was used to elucidate the crystal structure of the 1·diethyl ether complex. Crystals are orthorhombic with space group P212121, a = 8.532(3), b = 15.040(4), c = 18.491(5) Å, V = 2373(1) Å3, dc = 1.256 g/cm3, and Z = 4. Host and guest molecules were found to associate via hydrogen bonds, with the guest molecules residing in undulating channels lined by host molecules.

A comparison of the behaviour of two closely related xanthenyl-derived host compounds in the presence of vaporous dihaloalkanes

The behaviour of two closely related xanthone-derived host compounds, N,N’-bis(9-phenyl-9-xanthenyl)ethylenediamine and N,N′-bis(9-phenyl-9-thioxanthenyl)ethylenediamine, which formed complexes with CH2Cl2, CH2Br2 and CH2I2 after recrystallization from each of these solvents, was compared when subjected to these guest and guest mixtures in the vapour phase. Surprisingly, these hosts displayed entirely different behaviours under these conditions, with only the thioxanthenyl derivative possessing the ability to clathrate these guests (or guest mixtures) from the gas phase; this ability was entirely absent in the xanthenyl host. All novel complexes were subjected to single crystal diffraction analyses in order to investigate the interactions present, as well as thermal and Hirshfeld surface experiments. The host selectivity and host–guest interactions were correlated with the differences observed in the recrystallization and vapour experiments. Furthermore, data obtained for the novel complexes by employing various analytical techniques were related back to the observed selectivity order.

DMT [(−)-(2R,3R)-2,3-dimethoxy-1,1,4,4-tetraphenylbutane-1,4-diol], a highly efficient host compound for nitroaromatic guests: selectivity, X-ray and thermal analyses

In this work, we reveal that the compound (−)-(2R,3R)-2,3-dimethoxy-1,1,4,4-tetraphenylbutane-1,4-diol (DMT) is a highly efficient host material for nitroaromatics o-nitrotoluene (o-NT), m-nitrotoluene (m-NT), p-nitrotoluene (p-NT) and nitrobenzene (NB). Each of these guests was included with a 2:1 host:guest ratio. The host displayed selectivity for p-NT and NB when these guests were mixed in equimolar proportions with any one of the other guest solvents, and the host recrystallized from this binary mixture. A selectivity order for the host in these conditions was thus noted to be NB ≈ p-NT > o-NT > m-NT. Furthermore, guests were also mixed in non-equimolar proportions and the host behaviour analysed, the results of which were in accordance with observations from the equimolar studies. Additionally, an equimolar quaternary experiment of all four guests provided a somewhat adjusted host selectivity order [p-NT (39.9%) > NB (30.2%) > m-NT (17.1%) > o-NT (12.8%)]. Single crystal diffraction analyses of all four complexes showed the crystals to share the same host packing, and comparable host–guest interactions were observed in each. However, thermal analyses, both DSC and TG, showed that the preferred guests p-NT and NB formed complexes with increased relative thermal stabilities, and this observation correlated with the selective behaviour of the host in competition experiments.

Complexes of TETROL with selected heterocyclics: unconventional host–guest hydrogen bonding and the correlation with host selectivity

Here we investigate and compare the more salient characteristics of host–guest complexes of (+)-(2R,3R)-1,1-4,4-tetraphenylbutane-1,2,3,4-tetraol (TETROL) with four heterocyclic guests, morpholine, piperidine, pyridine and dioxane. These guests each formed inclusion compounds with TETROL, and host:guest ratios were either 1:2 or 1:1. Single crystal diffraction experiments revealed unprecedented host behaviour in the presence of both piperidine and dioxane with respect to the mode of host–guest hydrogen bonding employed. Furthermore, by utilizing 1H-NMR spectroscopy or gas chromatography (as applicable) as methods for analysing complexes obtained from competition experiments, we were able to identify the host selectivity order, and were gratified to discover that this order correlated precisely with host–guest hydrogen bond distance.

Complexes of host compound (−)-(2R,3R)-2,3-dimethoxy-1,1,4,4-tetraphenylbutane-1,4-diol (DMT) with guests anisole and the methyl-substituted anisoles: host selectivity, thermal and single crystal diffraction considerations

Abstract(−)-(2R,3R)-2,3-Dimethoxy-1,1,4,4-tetraphenylbutane-1,4-diol (DMT) was determined to be a highly efficient host compound for anisole and the methyl-substituted anisoles (MA), clathrating each of these organic solvents with 2:1 host:guest ratios. Furthermore, this host displayed selectivity when presented with mixed guests, and guest–guest competition studies involving the methylanisoles revealed a host selectivity order of p-MA > m-MA > o-MA, whilst the addition of unsubstituted anisole to these experiments showed this guest to now be the preferred one (anisole > p-MA > m-MA > o-MA). Single crystal diffraction analyses indicated the absence of hydrogen bonding between host and guest molecules, and that guests were retained within the host crystal only by means of CH–π, π–π stacking and other short interaction types. The latter involved host aromatic carbon or hydrogen atoms and guest methoxyl or methyl hydrogens and aromatic carbons, as well as host and guest methoxyl hydrogens. Results from thermal analyses provided the reason for the observed selectivity order, with complexes comprising preferred guests anisole and p-MA displaying enhanced thermal stabilities relative to those with o- and m-MA.