Resorcarene complexes

Cavitand 6.29 has a vase-shaped cavity that is large enough to accommodate Me2NCHO in the solid state. In solution, the most effective host is the dimethylsilyl derivative (6.28e), which has a tall, narrow cavity suitable for inclusion of linear guests such as those listed above. Compound 6.28e is prepared readily from the octol [4] resorcarene 6.3 by treatment with SiMe2Cl2. The X-ray crystal structure of the CS2 complex of 6.28e is shown in Figure 6.7, indicating clearly the neat fit of the linear... 

Work by Paul Beer et al. in Oxford on dithiocarbamate-functionalised resorcarenes has resulted in resorcarene trimers termed molecular loops and molecular tetrahedra composed of four resorcarene units. The molecular loops (pyridine-capped Cd(II) and Zn(II) complexes) can bind C60 which fits neatly into the 16.4 A wide central cavity.35 The slightly larger tetrahedral tetramer which has a 19.4 A edge length, compared to 19.1 A for the loop, is bridged by square planar copper(III) ions, a very unusual oxidation state of copper that is obtained from iodine oxidation of an intermediate copper(II) complex. The solid-state structures of examples of the loop and tetrahedron are shown in Figure 10.35. 

Besides these classical aromatics and polyaromatic hydrocarbons, other very important classes or arene molecules are porphyrins [60, 61], phthalocyanins [61, 62], porphycens [63], calixarenes [64], resorcarenes [64], cydophanes [47], dendrimers [65], elementa-arenes [66], organometallic arene (hexahapto) [67], benzyne (dihapto), and aryl- and benzyl (monohapto) complexes [68], inorganic pyridine and polypyridine complexes [69], fullerenes [70, 71], and... 

The signs of the first and second Cotton effects in complexes with diols are opposite to those determined by the classical dibenzoate chirality rule (compare Figure 26).263 This means that the chiral guest induces an opposite chirality in the resorcarene host 129. Thus, 129 can be used as a supramolecular CD probe for the assignment of the absolute configurations of glycols and alcohols. 

The three structures shown at the right of the second line represent important families of receptor molecules that have been extensively studied in their own right. The aromatic spherand grew out of crown ether chemistry while calixarene chemistry developed on a separate evolutionary pathway. Still, their similarity is apparent. The structures of calixarenes and resorcarenes (also resorcinarenes) are included here because they have often been fused to macrocycles to form complex receptor systems. A few examples of fused receptor systems are discussed below. 

The synergistic effect was only found in mixed stationary phases that have a special selectivity. Those stationary phases were CD, crown ether, liquid crystal-hne, resorcarene, calixarene, AgNOs, and others. Crown ether, CD, cahxarene, and resorcarene possess cyclic moieties with cavity-like structures that are able to form inclusion complexes with metal ions and organic molecules. Liquid crystalhne stationary phases have temperature-dependent ordered structures and the retention is governed by the solute s length-to-breadth ratio. AgNOs retards olefins by the formation of loose adducts. Together with the above special selectivity stationary phases, they have already been the focal point of sup-ramolecular chemistry. 

Only few investigations have been published on the gas-phase ion chemistry of host-guest complexes of calixarenes. With the advent of ESI mass spectrometry, especially when combined with ion-trap and FT-ICR mass spectrometry, this field has started to be developed. Binding selectivities of alkali metal ions to cahxarene-based crown ethers and open-chain ethers have been studied , the inclusion of neutral guests into the protonated resorcarene-based cavitand hosts by gas-phase ion-molecule reactions with amines have been studied and the formation of capsules from various calixarene tetraether derivatives and alkylammonium ions as ionic guests (notably enabling their detection by mass spectrometry) have been described recently . ... 

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