Interaction of hydroquinone and substituted derivatives with two cyclophane-like hosts: X-ray, molecular modelling and NMR studies

• Published in: Journal of Inclusion Phenomena and Macrocyclic Chemistry 2009-10, Vol.65 (1-2), p.31-38
• Main Authors: Lindoy, Leonard F., Matthews, Owen A., McCool, Brian J., Meehan, George V., Perkins, David F., Skelton, Brian W., White, Allan H.
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Crystallography and Scattering Methods; Food Science; Organic Chemistry; Original Article
• ISSN: 0923-0750; 1573-1111
• DOI: 10.1007/s10847-009-9617-7

An investigation of the interaction of hydroquinone and selected substituted derivatives with the 28-membered tetrabenzo-cyclophane-type receptor 1 and a tetramethoxy-substituted variant, 2 , each incorporating an O 4 N 2 -heteroatom set, is reported. In a preliminary solution study, aromatic solvent introduced shift (ASIS) experiments had indicated that deuterated benzene is intercalated between the two xylyl bridges of cyclophane 1 . In parallel with this result, a further NMR study was consistent with the inclusion of hydroquinone between the xylyl groups of 1 to produce a face-to-face π-stacked arrangement, with additional host–guest stability being provided by a pair of simultaneous hydrogen bonds between host and guest. Owing to limited CHCl 3 or CH 2 Cl 2 solubilities no association constant ( K ) for this host–guest system could be determined. However, use of the more soluble substituted guests 2,5-di- tert -butylquinone and 2,3-dimethylquinone enabled K values for 1 and 2 (ranging from 54 to 162 dm 3  mol −1 ) to be determined. Single crystal X-ray structure determinations of (solvated) 1 and 2 are reported, their highly different conformations reflecting their change in substitution pattern.