Calixarenes complexation data

A different synthetic access to a 1 -metallacyclopropene, which can be a versatile organometallic synthon, is displayed in Scheme 33. The mono-alkyne derivatives of W(IV)-calix[4]arene are easily accessible through the thermal displacement of cyclohexene from 32 using the appropriate acetylenes. The reaction led to complexes 34 and 172-174. The proposed 3-metallacyclopropene has been confirmed from the spectroscopic and the X-ray data. The H NMR data reveal a cone conformation of the calixarene with a four-fold symmetry, for which the... 

Chloroform solutions of calixarenes (33 38)293,354 show high affinity for Au111 and good selectivity over Fe111 in some cases.293 Spectroscopic data indicate that complex formation with thioethoxy calix[4]arenes involves formation of inner-sphere complexes with Au—S bonds.354... 

Largest quantum yields reported for Eu(III) and Tb(III) complexes with derivatised calix[4]arenes. From data reported by N. Sabbatini et al., in Calixarenes 2001, Z. Asfari, V. Bohmer, J.M. Harrowfield, J. Vicens, eds, Dordrecht Kluwer Academic Publishers, 2001, Ch. 31. 

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). 

Encapsulation of the Eu3 + and Tb3 + ions by cage-like ligands was also achieved using functionalized calixarenes. Metal luminescence properties were studied mostly for complexes of calix[4]arenes, while few results are available for complexes of calix[6]arenes and calix[8]arenes, with the latter being dinuclear complexes. Figure 13 schematically shows the calixarene ligands of the Eu3+ and Tb3+ complexes examined. Some photophysical data and the number of coordinated solvent molecules of these complexes are gathered in Table 4. 

At first, the catalytic effect of the single micellar solutions based on surfactants of different structure was studied. The data covering this period are reviewed in refs. The regularities when generalized made it possible to proceed with the more complicated systems, in particular, the binary surfactant solutions, the polymer-surfactant and polymer-cyclophane (calixarene, pyrimidinophane, and etc.) systems. For these systems, the terms supramolecular systems (ensembles, compositions, complexes) are further used. 

More recently, it has become possible to extract useful information from ab initio studies of calixarenes as is evidenced in a review by Schatz. DFT calculations on tetrapropoxy-4-t-butylcaUx[4]arene with H3O+ helped Kff2 to interpret spectroscopic data related to the structure of the complex, and the conformational equilibria of tetraamino-and tetramercaptosulfonylcaUx[4]arenes were determined by Magalhaes by the same method. ... 

In contrast to the larger calix[n]arenes (n > 4) the cavities of calix[4]arene (7) or p-ferf-butylcalix[4]arene (8), whether in the cone conformation or not, are generally too small to accommodate a Cgo fullerene molecule. Makha et al. [16] however showed that with Cgo, p-benzylcalix[4]arene (9) forms a 2 1 (Cgo)2 9 complex in which the fullerenes are packed into flat sheets with each calixarene nestled exo to the cavity of the calixarene but into a cavity created by a square array of fullerenes (Fig. 33.10) [16]. The X-ray structure determination of this complex which was formed by slow evaporation of an equimolar solution of both components, required synchrotron radiation to provide suitable stmctural data refinement. The authors compared the X-ray data from this (Cgo)2 9 complex with that from the corresponding 1 1 complex formed with the smaller van der Waals diameter ( 8.1 vs 10.0 A) o-carborane which resided endo within the cavity with the... 

It took 8 years to publish another structure. In 1976 K. J. Palmer et al. reported two conformers of another resorcin[4] arene derivative, i.e. cis- and trans-C-para-bromophenyl-4,6,10,12,16,18,22,24-0-octaacetylcalix[4]resorcinarene [3]. Than in next 3 years G. D. Andreetti et al. published the first crystal structure of inclusion compound formed by para-ferf-butylcalix[4] arene with toluene [4]. The calixarene molecule was found in cone conformation and the guest molecule could not be located within the host cavity due to its disorder (the molecular complex was located on a crystallographic fourfold axis). The Authors also noticed that the structure undergoes the order-disorder phase transition at 248 K. In 1996 the disorder high temperature phase was resolved with the aid of solid-state NMR data by E. B. Brouwer et al. [5] (unfortunately, the atoms coordinates are not deposited in CSD) and in 1998 the low temperature ordered phase was reported by A. Arduini et al. [6] (Fig. 38.2). The inclusion complex is stabilized by week interaction. The crystal and molecular structure of this... 

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