Calixarenes moiety

Calixarenes are widely used platforms in supramolecular chemistry and by ring closing of acyclic thiophene precursors in the final step a thiophene ring can be included into the calixarene moiety <1999H(51)2807>. The isomers 167-169 can be isolated serving as good hosts for T-methylpyridinium iodide. 

The calix[4]arene-based diphosphine (119) (R = Me, Pb, Ph R = Pb) on reaction with [Rh(/r-Cl)(COD)]2 and then TlPFg forms the dinuclear species (120). These were tested as catalysts for hex-l-ene hydroformylation (see Carbonylation Processes by Homogeneous Catalysis) and that with R = Ph was best, but the performance was not better than extant systems and no special role for the calixarene moieties could be discerned. Several papers have used DFT calculations as part of QM/MM studies (see Molecular Orbital Theory) to probe the course of the hydroformylation process (see Carbonylation Processes... 

Because calixarenes have rather low molar absorption coefficients, more efficient chromophores were attached to calixarene moieties in order to obtain strongly absorbing ligands for Eu3+ and Tb3+ com-plexation. Complexes of ligand 61, which contained four pyridine-N-oxide... 

Scheme 42 Diruthenium complexes 69-72 having Iriazenide and calixarene moiety...

Crown ether-functionalized calixarene 2.168 (Chart 1.36) in which two bithiophene units were attached at the termini of a calixarene moiety was prepared by a similar procedure to that described above for 2.167... 

Sannicolb et al. synthesized cyclopentadithiophene (CPDT)-functionalized calixarene moieties 2.170 and... 

A DCL of short polymers has been generated from the condensation of resorcinol and 1,4-butanedial (Scheme 1.11) [41]. Resorcinol and 2,5-dimethoxytetrahydro-furan (3.3 equiv.) were combined in ethanol at 80 C in the presence of HCl. Acid-catalyzed decomposition of the 2,5-dimethoxytetrahydrofuran led to the formation of 1,4-butanedial. Each aldehyde then underwent two condensation reactions with resorcinol to form ladder-like polymers containing calixarene moieties under thermodynamic control. 

Li reported the first synthesis of calixarene-modified chitosan. The adsorption properties of calixarene-modified chitosan were greatly varied compared with that of chitosan, especially with the adsorption capacity towards Ag and Hg, becanse of the presence of calixarene moiety (Li et al., 2003). Pyravic acid modified chitosan had higher adsorption capacities for Cu + Co than chitosan and salicylalde-hyde modified chitosaa Chitosan benzoyl thiourea derivative has been synthesized and used successfully for the removal of the hazardous Co and Eu radio nuclides from aqueous solutions (Metwally et al., 2009). 

The properties of calixarene-based host molecules are strongly influenced by the conformation of the calixarene moiety. Pyridinocalix[4]arenes are conforma-tionally inflexible molecules (the introduction of just one pyridylmethyl group at the lower rim suffices to suppress conformational changes), while the larger calix[6]arene homologues show fluxional properties. 

Fig. 1. Views of one of the two independent calixarene moieties in the unit cell of the salt [(CH3)4N]2l>- -hutylcalix[6]arene - 2H], in which an included cation is ordered and another associated but nonincluded cation is disordered over two configurations. Only the phenolic hydrogen atoms are shown.

The ion binding properties of 11a and 11b were studied by solvent extraction experiments of selected alkali and transition metals such as Li, Na, K, Cs, Cu, Co, Cd and Hg from aqueous into dichloromethane organic phase. The polymers 11a and 11b have exhibited good extraction ability for mercury (II) cations. The low extraction ratio of 11b than 11a results from the number of calixarene moieties in the polymeric backbone. 

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