Calixarenes calix resorcinarenes

Among more complex macrocycles, Li et al. [47-52] reported the preparation and characterization of stationary phases incorporating calixarenes or calix-crowns bonded to silica. With individual columns, high selectivity was observed in the separation of alkylated aromatics, aromatic carboxylic acids, sulfonamides, nucleosides, and water-soluble vitamins. In other work, Sokoliess et al. [53] have characterized calixarene- and resorcinarene-bonded stationary phases similar to those described in the previous section of this chapter. And Huai et al. [54] used an end-capped p-tert-butyl-calix[4]arene-bonded silica phase for HPLC separation of a number of organic compounds. Resorcinarenes have also found application in GC. [55-57] Recently, exotic macrocycles have been used in capillary electrochromatography, as reported by Gong et al. [58]... 

Chirality in calixarenes and resorcinarenes can be essentially of two different types, depending on the method used for generating it. The first type, called chirality by attachment, consists of the introduction of a chiral, nonracemic, moiety onto the calixarene or resorcinarene framework. The second type, often referred to as inherent chirality, has been particularly studied for calix[4]arenes, and it is usually observed when three (AABC) or four different phenolic units are present in the macrocycles (Figure 24). As this type of chirality is linked to the nonplanar shape of calix[4]arenes, the well-known ring inversion of these compounds must be avoided through functionalization at the lower rim to obtain stable enantiomers. 

Several recent and comprehensive review articles have been published on calixarenes and resorcinarenes, lich cover both the chemistry and the host-guest properties of these macrocycles. The conformational properties of calix[4]arenes and resorcinarenes are particularly well studied and exploited. They can exist in four different conformations (Figure 2) named cone, partial cone, 1,3-alternate, 1,2-alternate which strongly influence their complexation properties. 

In addition to crown-ethers, calix[4]resorcinarenes 19 have also been used as head groups to obtain azobenzene amphipbiles with sufficient photo-isomerization in LBK films. For this purpose, azobenzene moieties have been tethered to the lower rim of the crown conformer of the calixarene. O-octacarboxymethoxylated calix[4]resorcinarenes 19 (X = CH2-COOH) display efficient trans to cis photoisomerizability in densely packed mono-layers on a water surface, in LBK films, and in surface-adsorbed monolayers, whereas the noncarboxymetylated 19 (X = H) derivative gives films that are too densely packed. However, the aggregation is already suppressed efficiently compared to the azobenzene derivative without calixaren. ... 

Analysis of CP kinetics and the parameters obtained are a source of important information about host-guest interactions. From the classic I-S model of cross polarization, it was found that the values of T pH relaxation times for guest and host molecules are considerably different. This suggests that DMF carbons cross-polarize from the DMF protons, not from the remote protons, of calixarene. Moreover, such a result proves that the DMF is located outside the calices and between the calixarene molecules. The simple I-S model is not sufficient to describe the cross-polarization of the complex of tetra (C-undecyl)calix[4]resorcinarene with DMA. The best fit of experimental data was seen when the more advanced I-F-S model of cross polarization was adopted [57]. Analysis of CP kinetic parameters provides important information on molecular mobility (Fig. 19, Table 5). 

Early reports on AFM studies on calix[4]resorcinarene and calix[4]arene sulfide molecules [150, 151], suggested, that the calixarenes self-organize in monolayers on Au(lll) surfaces, however, they did not identify a molecular ordering. 

It was shown by in situ STM that highly ordered SAMs of the porphyrin compound 217 in face-on disposition were formed on iodine-modified Au(lll) surfaces, whereas disordered adlayers were formed on bare Au(lll) surfaces314. Two periodicities were found by AFM for the SAM on Au(lll) of a thioether derivative of calix[4]resorcinarene (218), one with lattice constant of ca 0.42 nm, attributed to the alkyl chain packing of the four thioether anchors on the metal surface, and the second one with lattice constant of ca 1.16 nm, attributed to the calixarene macrocycles315,316. 

FIGURE 27. Spontaneous multilayering of alkane-derivatized calix[4]resorcinarene on the surface of a calixarene-terminated monolayer. Adapted with permission from Reference 411. Copyright (1995) American Chemical Society... 

The higher energy of the triplet states in calixarenes 39a-f (fig. 37), 20600-23 500 cm , allows sizeable sensitization of Eu and Tb° luminescence. Compared with calix[4]resorcin-arenes, better quantum yields are also obtained for the Nd and Yb 1 1 complexes (table 7), 0.06-0.24%, and 0.09-0.61%, respectively. However, the solvent is not the same, dmf as compared to ethanol, which may explain the difference. As for the calix[4]resorcinarene complexes, the speciation in solution has not been established, but in this case, the 1 1 complexes have been isolated and gave satisfactory elemental analyses (Korovin and Rusakova, 2001 Shevchuk et al., 1998a). The best quantum yields are obtained with H239f which bears two phenylamide chromophores on the narrower rim and these substituents are directly coordinated onto the lanthanide ion, which understandably increases the efficiency of the energy transfer process. 

The cavity of these calixarenes is usually too small to accommodate fullerenes, and is confirmed by solution, unless they have extended cavity walls as in calix[4]-naphthalenes. Nevertheless, some calix[4]arenes were shown to form stable crystalline complexes with C60 with the fullerene eno- to the calixarene cavity, and they include p-Ph-calix[4]arene, which has a toluene molecule in the cavity, the overall structure dominated by fullerene-fullerene and eso-calixarene fullerene interactions p-Br-calix[4]arene propyl ether, the structure showing very close interfullerene contacts in a columnar structure (Fig. 2d), which most likely results in opposing induced dipoles from the unidirectionally aligned calix-arenes " and /7-I-calix[4]arene benzyl ether, where the fullerenes are ordered without appreciable interfullerene interactions. There is also a calix[4]resorcinarene, R = CH2CH2Ph, 3, which has a molecular capsule derived from head-to-head hydrogen bonding of two resorcinar-enes and propan-2-01 molecules, with the fullerenes also... 

Calix[4]resorcinarenes, a subclass of calixarenes, are large cyclic tetramers that have found applications as macrocyclic receptors, host molecules, host-guest complexes, and so on (Botta et al, 2005 Martinez et al., 2000 Leyton et al., 2005 Yonetake et al, 2001). It shonld be noted that the synthesis of calix[4]resorcinarenes was first reported in the late nineteenth century by Bayer based on the concentrated sulfuric acid-catalyzed cyclocondensation of benzaldehyde and resorcinol (Bayer, 1872). These cyclic compounds were synthesized by TSA (Scheme 3.8) (Karami etal.,2012f). 

Calixarene An oligomeric molecule originally obtained from the condensation of a / -alkyl phenols and formaldehyde. The term now applies to a variety of derivatives of cyclo oligo[(l,3-phenylene) methylene] In the name calix[n]arene, the [n] refers to the number of phenol and aldehyde units per molecule. The name is derived from the cup shaped cone conformation of calix[4]arene. See also resorcinarene. 

In contrast to the well developed calixarene sensors of the potentiometric type, chemical sensors based on membrane permeability changes are still in its initial stage. In the present study the permeability of LB calix[4]resorcinarene was found to be controlled by the presence... 

Synthesis of Calixarenes (1)-(4) Compounds p-5,ll,17,23-tetranitro-25,26,27,28-tetrahydroxy-calix[4]arene, (1), and 4,6,10,12,16,18,22,24-octahydroxy-2,8,14,20-tetraethyl-calix[4]resorcinarene, (2), were prepared in-house following procednres described elsewhere [37]. Compoimd 5,ll,17,23-tetra-A /s-(Af-methylmor-pholine)-25,26,27,28-tetrahydroxy-calix[4]arene, (3), was prepared by adapting the procednre described by Pandey [51]. Compoimd 5,ll,17,23-tetranitro-25,26,27,28-tetra(Af-(5-dimethylaminonaphthalene-l-sulfonyl))-cahx[4]arene, (4), was synthesized according to the reported literatnre procedure [52]. 

Calix[4]resorcinarenes 76 are tetrameric cavity compounds produced by the reaction of an aldehyde and resorcinol (Figure 50.24). Calixarenes 77 are produced by the reaction of phenol and formaldehyde. Chirality in calixarenes and calix[4]resorcinarenes is usually achieved by the addition of enantiomeric ally pure moieties. Although several calLx-arenes and calix[4]resorcinarenes have been examined as chiral NMR shift reagents, only one particular family of water-soluble calix[4]resorcinarenes 78-82 has been widely studied. " ... 

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