Resorcinarene molecules

Solvent molecules within the hexameric capsule can be displaced by sizable quaternary ammonium salts, and dissociation of at least one resorcinarene molecule from the hexamer is required for guest exchange. More details about the dynamic process of this assembly at nano- and micromolar concentrations were acquired using... 

Complementing our work on pure A-alkyl ammonium resorcinarene salts, Szumna and coworkers have prepared a series of zwitter-ionic resorcinarene molecules from amino acids through Mannich condensation reactions [63, 64, 65, 66]. These... 

Fig. 12 Brick-wall 2D network of complex (C-methylcalix[4]resorcinarene).2(4,4 -bipyri-dine).0.5(decamethylruthenocene).2(ethanol).The 24host molecule is in aflattened cone conformation. Disordered guest molecules are not shown and occupy the apparent cavities [58]... 

NMR spectroscopic data in CD2C12 solution verified the encapsulation of cobaltocenium inside a capsule composed of six molecules of resorcinarene 4. From NMR diffusion coefficient measurements, we concluded that the resorcinarene molecular capsules were preformed in CD2CI2 solution51 in the absence of cobaltocenium or any other cationic species. Similar results in CDC13 solution have been reported by Cohen and coworkers.52 53 It is now clear that cationic species are not required to seed the self-assembly of the capsules. 

Molecular cavities have been intensively studied over the last decades by supramolecular chemists, since they can be used for molecular recognition, catalysis, or transport processes across membranes. Bowl-shaped molecules such as calixarenes (28), res-orcinarenes (29), or cyclotriveratrylene (CTV, 30) derivatives constitute useful building blocks for cavities since their shapes and sizes can be controlled by covalent synthesis to a remarkable degree (Figure 3.15). The inherent flexibility of calixarenes and resorcinarenes can be limited either by substitution or by bridging, respectively. 

Crystal structures for several of the corresponding pyrogallol[4]arenes 50 (Figure 3.23) have been solved. These also form hexameric capsules, which now contain an array of 72 hydrogen bonds (48 are intramolecular and 24 intermolecular, HB/ (N— 1) =4) and have no structural water molecules [64]. The increase in the ITm HB/(N— 1) value agrees very well with the fact that nanocapsules based on pyrogallol 50a are more stable in polar media than those derived from resorcinarene 49a. 

Fig. 39a, b Crystal structures of the capsule 52 between two tetracarboxylic acid resorcinarenes and four 2-aminopyrimidine molecules showing a the composition b the packing of the guests within the cavity (one aminopyrimidine is omitted to show interior)... 

Fig. 40 Two resorcinarene cavitands held together by 16 hydrogen bonds with 8 bridging isopropanol molecules...

---