Polymorphism, selectivity and reactivity of inclusion compounds

Abstract

The inclusion ability of two host compounds H1, 9-(1-naphthyl)-9H-xanthen-9-ol, and H2, 9-(1-naphthyl)-9H-thioxanthen-9-ol was studied. We have previously shown that H1 successfully forms inclusion compounds with 1,4-dioxane[1] and acetone [2]. Here we report on the structures of H1•DMF and H1•DMA where DMF = N,Ndimethylformamide and DMA = N,N-dimethylacetamide. Numerous attempts at forming inclusion compounds between H2 and selected small organic guests including DMF and DMA were unsuccessful and yielded powders of the host alone. Both H1•DMF and H1•DMA successfully solved in P(-1), the host: guest ratios were 1:1 and their structures were stabilized by hydrogen bonding of the typeSulphur is less electronegative than oxygen and is less likely to be involved in hydrogen bonding. Interestingly even though the hydrogen bonding in the inclusion compounds of H1 does not involve the ether oxygen of the host, still no inclusion is found for H2. The kinetics of desolvation for H1•DMF and H1•DMA were analysed as well as competition experiments. MS18 P02 Clathrates with Mixed Guests Keywords: clathrates, molecular recognition, crystal structuresInvestigation of the selectivities of two diol organic hosts for pairs of small organic guests gave very interesting results which could be correlated with the crystal structures of the inclusion compounds containing mixtures of the two guests. This study comprises two separate investigations and in the first investigation the selectivity of the host 9,9'-(biphenyl-4,4'-diyl)difluoren-9-ol (H1) for a pair of guests with very similar chemical compositions but significantly different boiling points was examined. The second investigation involved a pair of guests with very similar boiling points and which form inclusion compounds with a particular host which have different host:guest ratios when crystallised at different temperatures. We thus investigated the selectivity of the host 9,9'-(ethyne-1,2-diyl)difluoren-9-ol (H2) for these guests and carried out the competition experiments at two different temperatures in order to see whether the selectivity would change with changing temperature.Clathrate compounds are an important aspect of supramolecular chemistry and this study displays some novel results showing interesting selectivity profiles, and more importantly giving new insight into clathrates with mixed guests through crystal structure analysis, which in each case could be correlated with the selectivity profiles. -(1,4)-linked D-glucopyranosyl residues have a hydrophobic, relatively rigid cavity able to host a plethora of molecules. Being chiral compounds, CDs can, in principle, discriminate between enantiomers (guests) forming preferentially with one of the two a more stable inclusion complex [1,2]. X-ray crystallography can provide details of the factors that lead to chiral recognition. Structures of CD inclusion complexes with each enantiomer separately suggest that not only the cavity, which undergoes "induced fit" by the presence of the guest, but the guest's H-bondin...