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The synthesis and characterization of a novel florescent chemosensor 1 with two different types of cationic binding sites have been reported in this work, which is a calix[4]crown derivative in 1,3-alternate conformation bearing two 2-phenyl-5-(4-dimethylaminopyenyl)-1,3,4-oxadiazole units. The recognition behaviors of 1 in dichloromethane/acetonitrile solution to alkali metal ions (Na+ and K+), alkaline earth metal ions (Mg2+ and Ca2+), and transition metal ions (Co2+, Ni2+, Zn2+, Cd2+, Cu2+, Mn2+, and Ag+) have been investigated by UV-Vis and fluorescence spectra. The fluorescence of 1 might be quenched selectively by Cu2+ due to the photo-induced electron transfer mechanism, and the quenched emission from 1 could be partly revived by the addition of Ca2+ or Mg2+; thus, the receptor 1 might be worked as an on–off switchable fluorescent chemosensor triggered by metal ion exchange.

We demonstrate that Ullman fragment-coupling can be used to synthesise an oxacalix[4]arene monocarboxylic acid, which provides easy access to its water-soluble carboxylato derivatives. Crystallographic and computational data suggest that the new carboxyl-substituted oxacalix[4]arene adopts a 1,3-alternate conformation both in the solid-state and in methanol solution. Its water-soluble tetrabutylammonium derivate can detect the herbicide paraquat at neutral pH in aqueous media (Ka = 111 ± 3 M–1) and in methanol (Ka = 2020 ± 70 M–1). [ABSTRACT FROM AUTHOR]

The title compound, C51H48N2O7, was synthesized by the reaction of 25,27-(3,6,9-trioxaundecane-1,11-dioxy)-26,28-(3-phenyl)-3-azapentane-1,5-dioxy)calix[4]arene with tetracyanoethylene in dry DMF. The compound has a 1,3-alternate conformation with an oxo-crown-5 unit and an aza-crown-3 unit with a nitrogen atom connecting tricyanoethylenephenyl group as a chromophore. Pairs of benzene rings of the calixarene are facing one another. Three of the four oxygen atoms connected to a benzene have endo-conformations while the other is exo. The oxo-crown-5 system has a t–g–g–t conformation. The dichloromethane solvent molecule is linked to the main molecule by a C—H...Cl hydrogen bond. In the crystal, C—H...O, C—H...Cl hydrogen bonds and C—H...π(ring) interactions are observed.

Four new tetrasubstituted [1.1.1.1]metacyclophanes ( 4 – 7 ), that are inherently adopting a 1,3-Alternate conformation, bearing four or eight peripheral carboxylic binding sites, and appended with spacers group (alkyl or phenyl) differing by the flexibility, have been synthesised in high yields. The structures of the obtained compounds have been investigated in solution as well as in the solid state, for three of them, by using single-crystal X-ray analysis. [ABSTRACT FROM AUTHOR]

Novel upper-rim modified tetraphosphinocalix[4]arenes (5a–b) adopting 1,3-alternate conformation have been synthesized. Reaction of 5,11,17,23-tetrachloromethyl-25,26,27,28-tetrahydroxycalix[4]arene (1) with Ph2POEt gave 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrahydroxycalix[4]arene (2). Tetra-O-substitution of 2 with n-propyl iodide or benzyl bromide in the presence of K2CO3 carried out to afford 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrapropoxy-(3a) or -benzyloxycalix[4]arene (3b), whereas di-O-substituted calix[4]arene, 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,27-dipropoxy-26,28-dihydroxycalix[4]arene (4), was obtained exclusively when Na2CO3 was used as base. Reduction of 3a–b with PhSiHCl2 afforded 5,11,17,23-tetrakis(diphosphinomethyl)-25,26,27,28-tetrapropoxy-(5a) and -tetrabenzyloxycalix[4]arene (5b). 1H and 13C NMR analysis reveals that the phosphines (5a–b) and the tetra-O-substituted phosphine oxides (3a–b) adopt 1,3-alternate conformation, while the parent tetrahydroxy-(2) and the di-O-propylated phosphine oxide (4) adopt cone-conformation. The X-ray structure indicates that the calix[4]arene moieties in 4 a pinched-cone conformation in solid state. Complexation of the phosphine ligand (5a) with [RuCl2(p-cymene)]2 affords the tetranuclear complexes, [{RuCl2(p-cymene)}2 · 5a] (6), as 1,3-alternate conformer. [Copyright &y& Elsevier]

A new calix[4]arene derivative [25-(3-bromo-propyloxy)5,11,-17,23-tetrakis(tert-butyl)-26,27,28-tris(1-p ropyloxy) calix[4]arene] (BTC) in the 1,3-alternate conformation was tested as a cesium-selective ionophore plasticized PVC membrane electrode. The resulting electrode showed a Nernstian behavior for Cs[sup +] ion over a wide concentration range (1.0 × 10[sup -6]-1.0 × 10[sup -1]M). The selectivity coefficients for cesium with respect to alkali, alkaline earth, ammonium and some transition metal ions, were determined. A relatively high Cs[sup +]/Rb[sup +] selectivity was observed, the selectivity coefficient (K[sup pot, Cs Rb]) being ca. 10[sup -2]. Effects of membrane composition and pH of test solution on the potential response of the electrode were also discussed. The proposed electrode revealed a lower limit of detection (2.1 × 10[sup -7] M) and improved Cs[sup +]/ Rb[sup +] selectivity in comparison with the previously reported Cs[sup +] ion selective electrodes. [ABSTRACT FROM AUTHOR]

Abstract: Bridge perbromination and oxidation of tetramethoxycalix[4]arene 1 with twofold excess of N-bromosuccinimide in wet CHCl3 gives the respective tetraoxo derivative 2 in high yields. A crystal structure of 2 with CHCl3 reveals the chalice in the rare 1,3-alternate conformation with a channel-like architecture of solvent inclusion. [Copyright &y& Elsevier]