Calixarene, hosts

Arena, G., Casnati, A., Contino, A., Lombardo, G. G., Sciotto, D., and Ungaro, R. (1999) Water-soluble calixarene hosts that specifically recognize the trimethylammonium group or the benzene ring of aromatic... 

A further example of steric control on electron transfer processes involving calixarene hosts has been provided by Ziessel and coworkers who appended one (56) or two [Ru (bpy)3] moieties and a/ac-[Re Cl(CO)3(bpy)] (57) to a calix[4]diquinone [95]. For all the complexes the luminescence quantum yield is very low because of... 

Single molecule force spectroscopy was used to measure the inclusion of a guest into a calixarene host molecule, which served as example in the paragraph on single molecule force spectroscopy in this chapter (see Fig. 10.23) [96]. 

The binding of iminium ions by neutral calixarene hosts in the gas phase has also been detected with the help of SIMS-mass spectroscopy, and even binding constants have been estimated. The peak intensities observed in mass spectrometry reflect the association in a matrix and the stability of the complexes in the gas phase. Thus, mass spectrometry is a suitable tool to detect charged complexes based on cation- r interaction. Because of... 

Scheme 12.19 Extended calixarene hosts which form complexes with ammonium ions...

Fig. 4 Positive heterotropic allosteric regulation of complexation with calixarene hosts. Entry 12 Reprinted from Ref. [23]. Copyright 1998. with permission from Elsevier Entry 13 Reprinted with permission from Ref. [5]. Copyright 2001 by American Chemical Society Entry 14 Reprinted from Ref. [24]. Copyright 2000, with permission from Elsevier.

Many calixarenes form complexes in the solid state, this property having been observed even before the structure of compounds was established. Among the simple ca-lix[n]arenes, for example, / >-rer/-butylcalix[4]arene forms complexes with chloroform, benzene, toluene, xylene, nitrobenzene, nitromethane, acetonitrile, and many others, while /r-rer/-butylcalix[5]arene complexes were studied with lower alcohols, ethyl acetate, toluene, and tetraline. More flexible / -terr-butylcalix[6]arene was found to form complexes with acetonitrile and / -rerr-butylcalix[8]arene with chloroform. The tenacity with which the guest molecule is held by the calixarene hosts varies widely with the size of macrocycle. Whereas tetramers to hex-... 

A.E. Molecular recognition at an interface Binding of 129. monolayer-anchored ferrocenyl groups by an amphiphilic calixarene host. Angew. Chem. Int. Ed. Engl. 1995, 34. 

Photoresponsive psewdorotaxanes, were also obtained from heteromacrocycle combination of CD, cucurbituril and calixarene hosts, to achieve multiple functions. ... 

In an effort to produce selective anion spectroelectrochemical reagents the Lewis acidic redox-active cobalticinium unit and the redox- and photo-active ruthenium(II) bipyridyl moiety have recently been incorporated into calixarene host structural frameworks to produce novel calix[4]arene anion receptors which are extremely rare. The calix[4]arene ditopic anion receptor (22) containing two cobalticinium moieties was prepared as shown in Scheme 4 and its crystal structure is illustrated in (Fig 7). Proton NMR titration experiments suggested (22) acts as a ditopic anion receptor forming (22) 2X"(X = Cl",Br",N03, HS04") stoichiometric solution complexes. Analogous titration... 

The peak-to-peak potential splittings (A p values) observed in the presence of the calixarene host clearly depart from the theoretical 57-mV value that would be expected for a reversible redox couple. This finding clearly indicates that the complexation reactions interfere with the heterogeneous electron transfer process. We are currently carrying out further electrochemical experiments to improve our understanding of the mechanism for the oxidation of the calixarene-bound ferrocene guests. 

Although the substantial calixarene-induced shifts observed in the half-wave potential for the oxidation of all the guests strongly suggest that the main interaction site with the calixarene host is the ferrocene subunit, we used NMR spectroscopy to address this point in a more detailed fashion[18]. Our results can be summarized by the data in Figure 2 which... 

Lynam C, Diamond D (2005) Varying solvent polarity to tune the enantioselective quenching of a calixarene host J Mater Chem 15 307-314... 

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