Calixarene dimers

Figure 3. Capsules based on other hydrogen-bonding atoms omitted) Tetraurea calixarene dimer 16-16,...

Hydrogen bonded capsule consisting of calixarene dimers will be briefly presented in Section 8.3.2. 

Fig. 60a, b A generic calixarene dimer and a schematic picture of the manner in which the two monomers form a joining seam... 

Bai and co-workes reported a series of STM studies on various types of calixarenes on graphite and Au(lll) surfaces. Initially, they included p-tert-butylcalix[8]-arene in between domains of octa-alkoxyl-substituted phthalocyanine (PcOCg) monolayers on graphite [152]. The adsorption" of calix[4]arene (lower rim OH) on (111) facets of Au-beads lead to an "edge-on geometry of calixarene dimers with the lower rim pointing towards lower rim (Fig. 10.26a) [153]. 

The 1992 attempt to create a calixarene dimer from 285b vide supra) resulted primarily in the formation of a polymeric assembly in CDCI3 solution which... 

Various other examples have been provided in the literature involving the formation of molecular capsules. However, guest binding by these capsules may not have been studied, or evidence of a template requirement for formation may not have been present. These include urea-based calixarene dimers [50], deep-cavity resorcinarenes [51],... 

Figure 18 (A) Fukazawa s calixarene dimer—fullerene complex (the grey sphere is Ceo) and (B) the calixarene monomer—fullerene complex used as the reference system.

In addition to the preceding main-chain polymers, Rebek and coworkers have described the assembly of ditopic caUxarene units into polymeric capsules, polycaps, in chloroform, as a result of homo- and heterodimerization of urea and sulfonyl-urea groups on the upper rim of the calixarenes [73-75]. Each calixarene dimer along the polymer chain encapsulates solvent or other small molecule guests (e.g., 4-fluorodibenzene and o-dichlorobenzene). A schematic representation of a calixarene dimer and homopolymer is shown in Figure 20. ... 

Ring-chain equilibria are briefly introduced herein. Readers are referred to Ref. 5g fa- a more thorough discussion of this phenomenon. Ditopic monomers that are preorganized to form cyclic aggregates are described in Section IV.D of this chapter. l For a report of the foanation of a calixarene dimer through multiple hydrc en-bonding interactions as in 5 see Ref. 76. 

Figure 20 Calixarene dimer (left) and homopolymer (right) (adapted from R.K. Castellano, D.M. Rudkerich, and J. Rebek Jr. Proc. Natl. Acad. Sci. USA. 94 7132-7137, 1997 and R.K. Castellano and J. Rebek, Jr. J. Am. Chem. Soc. 120 3657-3663, 1998. With permission).

Complexation by Calixarene Dimers Towards Complete Inclusion of Fullerenes... 

Figure 18 Calixarene dimer (left) and homopolymer (right). (Adapted from Refs. 53, 54.)...

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