Glycoluril-based hosts

Cucurbit[6]uril and increasingly its higher homolognes have been nsed extensively in a variety of host-guest chemistry and nanostructure assemblies. Of particular appeal are rotaxanes and molecnlar necklaces, mechanically interlocked assemblies of molecnles based on CB[6]. Efficient synthesis of ID, 2D and 3D polyrotaxanes and molecular necklaces (cncnrbitnril beads linked by a macrocyclic molecnle string ) has been achieved by a combination of self-assembly and coordination chemistry. We discnss rotaxanes and molecular necklaces in Section 10.7, and cncnrbil-based systems are snmmarised in a recent review.  

---

Figure 6.14 X-ray structure of glycoluril-based host 6.36 showing the intrinsic curvature.17...

Fig. I (a) Glycoluril-based host molecules, (b) Dimeric arrangement of molecules in the crystal structure of 3b. (c) Computer-modeled representation of the binding of resorcinol in Host 3b. (d) The three conformations of Host 6 (from left to right) anti-anti, anti-syn, and syn-syn. View this art in color at www.dekker.com.)...

Glycoluril-based host molecules were used as components of substrate-selective catalysts. Using nature as a guide, catalytically active metal centers were linked to the receptor cavities. These supramolecular systems were synthesized to mimic well-known processes in natural... 

In another approach to introduce liquid crystallinity, aliphatic tails were connected to the convex side of a glycoluril-based host (23. Fig. 6a).It was reasoned that in the solid state, this host would form dimers, in a similar way as the parent compound 3b. As can be seen in Fig. 6c. such a dimer resembles the structure of a typical rod-like mesogen. Although the material formed by 23 exhibited the typical features of a liquid crystal, i.e., birefringent optical textures and a high degree of malleability, calorimetric and powder diffraction measurements showed that it was a plastic crystal composed of lamellae of dimers (Fig. 6c). Strong Ti-n interactions between the aromatic surfaces of adjacent molecules are the reason the material is not liquid crystalline. The... 

Biological Ligands, p. 88 Chiral Guest Recognition, p. 236 Complexation of Fullerenes, p. 302 Concave Reagents, p. 5 i 1 Cyclophanes Definition aiTd Scope, p. 414 Drug Delivery, p. 484 Glycoluril-Based Hosts, p. 597 Podands, p. 1106... 

Carcerands and Hemicarcerands, p. 189 Cryptophanes, p. 340 Glycoluril-Based Hosts, p. 597 Hydrogen Bonding, p. 658 Micelles and Vesicles, p. 861 Molecular Squares, Boxes, and Cubes, p. 909 Platonic and Archimedean Solids, p. 1100 Self-Assembly Definition and Kinetic and Thermodynamic Considerations, p. 1248 Self-Assembly Terminology, p. 1263 Soft and Smart Materials, p. 1302... 

Enzymes Clzaracteristics and Mechanisms, p. 554 Glycoluril-Based Hosts, p. 597 Homo calixarenes, p. 649 Hydrogen Bonding, p. 658 Hydrophobic Effects, p. 673... 

---