Hydrogen-bond molecular capsules of resorcinarenes (1) and pyrogallolarenes (2) attracted much interest in the last decade. It was found, for example, that resorcinarenes form hexameric capsules in non-polar organic solvents that can accommodate both trialkylamines and tetraalkylammonium salts. In search for the bulkiest guest that can be accommodated in the cavity of such capsules we found, with the aid of diffusion NMR, that such guests can interact also with the external surface of the hexameric capsules. Interestingly, monitoring the effect of CD3OD titration on the diffusion coefficients of the different components in such host-guest systems indicates that the interaction of such guests with the external surface of the hexameric capsule is significant and can be found also in case where guest's encapsulation occurs as in the case of trioctylamine (3) and tetraoctylammonium bromide (6). These CD3OD titrations showed also that these interactions are disrupted before the hexamer is disrupted and that before observing the free guests one can observe apparently the formation of a 1:1 complex between 1 and the guests.
- diffusion NMR
- supramolecular chemistry