Ditopic Calixcrowns with Inequivalent Crown Loops: Synthesis and Structural Characterisation of an Unsymmetrical Calix[4]arene biscrown-6

Consecutive base-catalysed reactions of calix[4]arene with the ditosylates of two different polyetherdiols result in the relatively efficient production of an unsymmetrical calix biscrown-6 which, after reduction of an ethoxycarbonyl substituent to an hydroxymethyl group, has been characterised structurally by a room-temperature, single crystal X-ray study of its chloroform solvate. Crystals of ( 4), C53H62O13... 0.57CHCl3, are triclinic, P¯1, a 18.95(3), b 12.394(9), c 11.756(7) Å 106.93(5), 101.77(8), 94.63(8)°, Z = 2; R was 0.088 for 2231 observed' (I > 3(I)) diffractometer data.     

Structural study of the 1:1 clathrate of an asymmetric calix[4]arene and acetone

The crystal and molecular structure of the 1:1 clathrate of the asymmetric calix[4]arene,1, and acetone has been determined by X-ray analysis. The crystal data are: tetragonal, space groupP4/n,a=b=12.574(6),c=12.572(6) Å,V=1988(2) ų,Z=2,D _x =1.111 g cm^–3,D _m =1.108 g cm^–3. Least-squares refinement based on 1131 observed reflections withF ₀>3(F ₀) and anisotropic temperature factors led toR=0.096. In spite of the molecular asymmetric calixarene1 the crystal structure has high symmetry, because a part of the host and guest molecules are in disordered states.     

A Schiff basep-tent-butylcalix[4]arene. Synthesis and metal ion complexation

This communication describes the synthesis of Schiff base calix[4]arene (1) in which the Schiff base unit bridges two opposite hydroxy groups ofp-tert-butylcalix[4]arene. The synthesis of (1) has been achieved by refluxing in acetonitrile-methanol the appropriate 1,3-dicarbaldehyde-p-tert-butyl-calix[4]arene (4) with 1,3-diaminopropane. The yield of the reaction is 19%. Ligand (1) possesses a compartment containing two nitrogen atoms, four ether-type oxygen atoms, and two ionizable hydroxy groups likely to complex metal cations.     

Synthesis and metal ion complexation studies of proton-ionizable calix

A series of novel N-chromogenic calix[4]arene azacrown ethers were synthesized as selective extractants of potassium ion. 1,3-Alternate calix[4]arene azacrown ethers were prepared by reacting 25,27-dipropyloxy-26,28-bis(5-chloro-3-oxapentyloxy) calix[4]arenes with p-toluenesulfonamide in the presence of potassium carbonate. The coupling reaction of calix[4]arene azacrown ether with 2-hydroxy-5-nitrobenzyl bromide in the presence of triethylamine in THF gave the chromogenic calix[4]arene azacrown ether in moderate yield. These compounds show high potassium selectivity over other metal ions as shown by two-phase extraction, bulk liquid membrane, and 1H NMR studies on a ligand-metal complex. It is assumed that the OH of the chromogenic group attached on nitrogen can assist the complexation by encapsulation of the metal.     

Two triethylammonium ion complexes of monoanionic calix[4]arene

Two complexes between mono‐deprotonated calix­[4]­arene and Et₃HN⁺ are reported. The first, triethylammonium 26,27,28‐tri­hydroxy­penta­cyclo­[19.3.1.1^3,7.1^9,13.1^15,19]­octacosa‐1(25),3,5,7(28),9,11,13(27),15,17,19(26),21,23‐dodecaen‐25‐olate, C₆H₁₆N⁺·C₂₈H₂₃O₄^?, comprises only the cationic and anionic species, whereas the second, tris­(triethyl­ammonium) tris[26,27,28‐tri­hydroxy­penta­cyclo­[19.3.1.1^3,7.1^9,13.1^15,19]­octacosa‐1(25),3,5,7(28),9,11,13(27),15,17,19(26),21,23‐dodecaen‐25‐olate] aceto­nitrile solvate, 3C₆H₁₆N⁺·3C₂₈H₂₃O₄^?·C₂H₃N, comprises one aceto­nitrile solvent mol­ecule for three such units. In both cases, the units are stacked in columns so that the ammonium cation is hydrogen bonded to a phenolic or phenolate O atom of one mol­ecule and included in the hydro­phobic cavity of another neighbouring calixarene. The short contacts present indicate that cation?π and C—H?π interactions are likely to be involved in the inclusion phenomena.     

Complexation Studies of a Calix[4](aza)crown and Crystal Structure of its Magnesium Complex

A systematic study of extraction properties and complexation behaviour of the calix[4](aza)crown 1 towards alkaline earth (Mg²⁺, Ca²⁺,Sr²⁺, Ba²⁺) and transition metal (Co²⁺, Ni²⁺, Cu²⁺,Zn²⁺) cations is presented. The binding behaviour of 1 was also investigated by ¹H-NMR and the crystal structure of the 1:1 complex with Mg²⁺ isdescribed.     

Properties of a Tetrahomodioxacalix[6]arene Derivative

The synthesis and X-ray crystalstructure of a novel tetrahomodioxacalix[6]arenehexamethylester 2 arepresented. Preliminary investigations of alkali metal ioncomplexation showed that 2 is apoor extractant with selectivity for lithium.     

Complexes of ytterbium(III) nitrate and triflate with homoazacalix[n]arenes (n=3, 4)

The synthesis and crystal structures of three ytterbium(III) complexes of homoazacalixarenes are reported. In all cases, the complexes are obtained without addition of a base, the protons of the complexing phenolic moieties being transferred to the amine groups upon complexation. The 1:1 complex between p-chloro-N-benzylhexahomotriazacalix[3]arene (1) and Yb(NO₃)₃ is analogous to the neodymium(III) complex reported previously, with the metal ion bound to three phenoxide groups and three nitrate ions. A second 1:1 complex is obtained with Yb(NO₃)₃ and p-methyl-N-benzyltetrahomodiazacalix[4]arene (2), in which the metal ion is bound to two phenoxide groups only. The replacement of nitrate by triflate counter-ions results in the formation of a 1:2 ‘sandwich’ complex with 1, in which two divergent calixarene molecules are bridged by the metal ion, the counter-ions being non-bonding.