Tris-calixarene

Calixarenes, when in their cone-conformation (54), represent versatile host systems for metalated container molecules and many examples have been reported in the literature (55-61). Reinaud and coworkers have carried out extensive work concerned with calix[6]arenes that are functionalized at the small rim by nitrogen arms (62), aiming to reproduce the hydro-phobic binding site of mononuclear zinc and copper metalloen-zymes. A recent example is the calix[6]arene ligand L1 (Fig. 3), in which a tris(2-methylpyridyl)amine unit covalently caps the calixarene small rim (63). The ligand forms copper complexes of... 

The racemization of bis-TB under different conditions has been studied as well as the first example of a sy -bis-TB, the tweezers-like isomer (05MI1). Concerning tris-TBs, the equilibrium between 51a-c (the syn,anti isomer) and 52 (the syn,syn isomer) has been studied (05MI1). Compound 52 has a calixarene-type structure (Figure 9). The one-pot preparation of tris-TB 51c by mixed trogerization , similar to the... 

Scheme 5.12 Selective synthesis of bis-, tris-, and tetraloop tetra-urea calix[4]arenes (a) metathesis and subsequent hydrogenation, (b) decomposition of the heterodimer (a pseudorotaxane) and isolation ofthe multiloop calixarene.

Further oxidation of 43 leads to bis- or tris-spirodienone derivatives of calixarenes. They possess with the directionality of each spirodienone moiety an additional, independent stereogenic element. Thus, for a calix[4]arene derived bis(spirodienone) 45 six isomeric forms are possible, two meso forms and two pairs of C2-symmetric enantiomers, see Figure 8. The number of possible isomers increases with increasing of the number of rings in the macrocycle.92... 

We have tried to give an overview, general, and comprehensive, but not necessarily complete and exhaustive, of chiral structures associated with macrocyclic compounds known in the broadest sense as calixarenes. Necessarily, the picture arising in this way is complex and heterogeneous, perhaps even confusing. We hope, however, that we have at least left the reader with a feeling for the fascination that may be connected with such chiral structures and for the various possibilities that exist for calixarenes. 

FIGURE 31.5 Calixarenes used in the BLM experiments for U(IV) transport studies. I (5,ll,17,23-tetra-fert-butyl-25,26,27,28-tetra hydroxy calix[4]arene) II (5,ll,17,23,29,35-hexa-fert-hutyl-37,38,39,40,4I,42-hexa hydroxy calix[6]arene) III (5,11,17,23,29,35,41,47-octa-terr-butyl-49,50,51,52,53,54,55,56-octa hydroxy calix[8]arene) and LV (5,II,I7,23,29,35-hexa-fert-butyI-37,39,4I-tri methoxy calix [6]arene -38,40,42-triol). (Reproduced from Ramakumar, J., Nayak, S.K., and Maiti, B., J. Membr. Sci., 196, 203, 2002.)... 

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. 

Stabilization and crystallization of [Cr f/x-OI 0/0112)J(3j y>+ cations have been achieved by exploiting the supramolecular interactions with large anionic assemblies initially with mesitylene-2-sulfonate or its adduct with 18-crown-6,837-839 and subsequently with the adducts of calixarene sulfonates with N- or O-macrocycles.840,841 This approach, illustrated in Scheme 27, allowed the crystal structures of di-, tri- and tetrameric Cr111 complexes, (165)-(167),837,839-841 as well as that of a heteropolynuclear complex, [(H20)4Rh(/i-0H)2Cr(0H2)4]4+,838 to be determined. 

Complementarity between different molecules has also been harnessed in the pursuit of capsular complexes. Schrader and Kraft have pioneered the design of complementary systems with three- and fourfold symmetry based on 1,3,5-tris(aminomethyl)benzene derivatives [18] and calix[4]arenes [19], respectively. This approach has also been taken by Reinhoudt whose vast output of calixarene chemistry includes work on calix[4]arene dimers held together by ionic interactions [20]. Other examples show how the presence of encapsulated guests templates the formation of self-complementary capsules [21], how two host molecules may be held together by metal coordination [22-24] or where hydrogen bonding by a second entity holds the assembly together [25,26],... 

The NMR spectra of the oxyanions generated by the action of BuLi on p-allylcalix[4]arene in DM SO suggest that the conformations of the mono- and tetra-anions are cone, while those of the di- and tri-anions are less clear " " (see ref. 1, pp. 124-126). However, X-ray crystal structures of the monosodium and dilithium salts of 4 , generated by the action of NaH or BuLi on the calixarene followed by treatment with MeOH, show both to be in the cone conformation in the solid state. "" ... 

The linear bi- and tri-phenolic oligomers formed in the condensation of p-tert-butylphenol and formaldehyde i.e. the precursors to calixarenes) have been shown to form intermolecular associated dimers even at concentrations lower than 10 These have been called hemicalixarenes (see ref. 1, pp. 53-54) and presumably play a significant role in the proclivity of the linear oligomers to form cyclic oligomers. 

The aqua complex 88, in its X-ray structure showed tetrahedral Zn" within the tris(imidazolyl) environment provided by calixarene-based... 

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