Inclusion complexes calixarenes

Figure 25. AH-TAS plot for inclusion complexation by cyclophanes and calixarenes.

It should be stressed that there is not alwaysjustice in reseach evaluation. The selective formation of inclusion complexes by cyclodextrins (such as 11) was established by Cramer [6] at least 15 years earlier than that by crown ethers. However, cyclodextrin studies forming an independent branch of host-guest chemistry seem underestimated in spite of their considerably greater practical importance at present than that of other host macrocycles (crown ethers 17, calixarenes 18, etc.). Sometimes they are even totally neglected by discussing inclusion phenomena [7]. 

If a highly polarizable group is introduced into a receptor molecule, substrate binding should cause substantial perturbations, so that the recognition event would be converted into a non-linear optical signal. Such recognition-dependent nonlinear optical probes may be derived for instance from polyenes such as those shown in Figure 20, from inclusion complexes [8.94a] or from donor-acceptor calixarenes [8.94b]. 

Chiral recognition by calixarenes in the gas phase is virtually unknown.458-460 To date, only few very recent gas-phase studies on this subject can be retrieved from the literature, i.e., (i) a gas-phase study on the displacement of several amino acids from the chiral amido4resorcinarene 9 (Scheme 9) carried out by Speranza and coworkers using an electrospray-ionization Fourier-transform ion cyclotron resonance (ESI-FT-ICR) mass spectrometer,461 462 and (ii) Lebrilla and coworkers study on the ability of the achiral calix[4]arene 7 and calix[6]arene 8 to form inclusion complexes with natural amino acids under matrix-assisted laser desorption ionization (MALDI) conditions.459... 

Basic calixarenes of the type calix[n]arene have been complexed with with n ranging from 3 to 9, including 12, and can be either inclusion complexes or exclusion complexes (see Table 47). Inclusion complex have three or more phenolic-oxygen bonds with the uranium, essentially enclosing the metal entirely, and the exclusion complexes have three or less, leading to a less than perfect encircling of the metal. " ... 

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. 

Abstract New applications of ID and 2D solid state (SS) NMR spectroscopy in structural studies of inclusion complexes (ICs) formed by organic host lattices (cyclodextrins, calixarenes, cyclophosphazenes, and fullerenes) are described. Each section of the review gives short characteristics of host molecules and recent applications of SS NMR. Less common systems, which are interesting as models for SS NMR studies, (bis[6-0,6-0 -(l,2 3,4-diiso-propylidene-a-D-galactopyranosyl) thiophosphoryl] disulfide (DGTD) and 1,2-dichloro-ethane/tris(5-acetyl-3-thienyl) methane (TATM)), are also discussed. 

The preparation of con< -f-butylcalix[4]arenetetra(AUV-diethylacetamide), 25, using the approach of Ungaro and Ugozzoli [4] as shown in Figure 3.9, is described below. It is a widely versatile calixarene derivative as indicated above and probably has many more possibilities to form inclusion complexes than those listed. 

---