Monolayers calixarene

In a study of mixed monolayers of C60 and p-iert-butylcalix[8]arene, different isotherm behavior was obtained [256]. The surface pressure was observed to rise at a lower molecular area (1.00 nm molecule vs. 2.30 mn molecule in the prior study). Similar isotherms were observed whether a 1 1 mixture or a solution prepared by dissolving the preformed 1 1 complex was spread. The UV spectra of the transferred LB films appeared different than that of bulk C60. It was concluded that a stable 1 1 complex could be formed by spreading the solution either of the mixture or of the complex. This was confirmed in a later study by the same group that included separate spreading of the calixarene and the C60... 

This is clearly a complex system, for it is pointed out that the calixarene-limiting area depends on the spreading solvent and is subject to a memory effect. In another study, mixed monolayers and the resulting LB films of C60 with two derivatized calix[4]resorci-nolarenes and with p-tert-butylcalix[6]arene and p-tcrt-butylcalix[8]arene were examined... 

Cuest-Induced Changes in Membrane Permeability. Calixarene derivatives are also used for sensing systems other than ISEs or optodes. Recently, a systematic investigation on the control of membrane permeability by use of oriented monolayers composed of calixarene esters was carried out. The hosts used were short alkyl chain esters of calix[6]arene [28 (R = Bu )] and calix[4]arene [26 (R = Bu ), 30 both cone conformers]. The permeabilities through the intermo-lecular voids of these monolayers were evaluated by cyclic voltammetry, as described earlier for oriented membranes of nucleobase derivatives. Cationic, anionic, and neutral electroactive compounds were used as the permeability markers. The voltammetric measurements were carried out either for a monolayer... 

Figure 7.6.3. The scheme of the calixarene-based monolayer mimicking the recognition at...

Access to compounds of the calixresorcinarene class [63] can be achieved by an acid-catalyzed reaction between resorcinol and various aldehydes. The ease of synthesis of many calixarenes and calixresorcinarenes. along with the ready availability of the starting materials, renders them of great potential for studying both academically and industrially motivated problems. These span many areas [58] from adhesives to the selective metal ion response of calixarene monolayers [64]. 

Instead of cyclodextrin, calixarene has also been used as the monolayerforming component in sensor preparation. In the example shown in Fig. 4.41, a self-assembled monolayer of calixarene was immobilized on an electrode of a quartz crystal microbalance. The quartz crystal microbalance is a masssensing device capable of nanogram-level precision (see Chap. 5). When the monolayer-covered microbalance was exposed to guest gas, the guest bonding... 

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. ... 

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. 

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 above listed examples illustrate that calixarene adsorption and organization in monolayers not only depends on the type of surface, but also on the preparation and measurement conditions. The cyclodextrins discussed below even form nanotube-like chains. 

FIGURE 18. Structure of a calixarene thioether (a), and a model for the arrangement of substituted cyclodextrins in a monolayer (b). Reprinted respectively with permission from References 225 and 227 Copyright (1997, 1996) American Chemical Society... 

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... 

A different approach to construction of calixarene-terminated surfaces was adopted by Crooks and coworkers who synthesized them by in situ conversion CO2H COC1 of the acid-terminated monolayer by treatment with vapours of SOCI2 followed by reaction... 

Specific interactions between calixarene and ferrocene groups were exploited by Kaifer and coworkers, who demonstrated that mixed monolayers containing ferrocenyl groups protruding above the surface of the film bind calix[6]arene host from aqueous solution at extremely low concentration (0.05-2 pM)442. 

Cgo and C q have been tentatively interpreted in terms of endo-ca ix complexes, but the possibility is not dismissed that the fullerenes simply lie on top of the calixarene monolayer. ... 

The adsorption of calixarenes on metal surfaces has received recent study. The Me(CH2)iiS(CH2)i2 ethers of 4 and 4 , for example, form a well-packed monolayer on a gold substrate, verified by IR spectroscopy and wetability... 

Figure 4.6.1 Amphiphilic calixarenes form monolayers on tin oxide electrodes, which then differentiate between water-dissolved monosaccharides (from left to right ribose, galactose, glucose).

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