An Interesting Approach to Bis—calix [5] arene Analogue from Caxlix[6] arene

By 1,4-bridgine of p-tert-butylcalix [6] arene with 2,6-bis(bromomethyl)-4-methyl-anisole,a new type of bis-calix [5] arene analogue was obtained in high yield.     

A bisphosphonite calix[5]arene ligand that stabilizes η6 arene coordination to palladium

Treatment of a bis(phenylphosphonite)calix[5]arene ligand with either palladium(II) chloride or 1,5-cyclooctadieneplatinum(II) chloride yields square planar metal complexes in which the two phosphorus atoms bind cis to the MCl(2) moiety (M = Pd, Pt). Chloride was removed from the palladium complex to open a coordination site at the metal for catalysis. The chloride removal resulted in a rare and unexpected η(6) coordination of an arene to the metal. The reaction is reversible upon addition of tetra-n-butyl ammonium chloride.     

Host-guest assembly of pyridinium-conjugated calix[4]arene via cation-π interaction

25-(4-Pyridiniumbutoxy)-26,27,28-trihydroxycalix[4]arene bromide 1 was designed to have both host and guest units in one molecule, and was assembled to become an oligomer via a cation-π interaction. X-ray diffraction (XRD) crystallographic study of 1 revealed that it oriented in a one-dimensional structure. Titrimetric ¹H NMR analysis and electrospray ionization mass spectrometry (ESI-MS) analysis indicated that 1 formed an oligomer in solution, and the restraint of the segmental motion would lead to the stabilization of the cation-π interaction compared with a bi-molecular complex composed of 25,26,27,28-tetrahydroxycalix[4]arene and N-butylpyridinium bromide.     

Synthesis and Conformational Properties of Bis（calix [4] arene）

The bis(calix [4] arene)3 was synthesized in moderate yield by the reaction of p-tert-butylcalix [4] arene (1) with 1,4-bis(chloromethyl) benzene (2). The conformation of all alkylated product 4 was investigated by the variable-temperature ^1H-NMR.     

Chemical resolution and chiral recognition of an inherently chiral biscalix[4]arene cone–partial cone conformer

An inherently chiral biscalix[4]arene carboxylic acid cone–partial cone conformer was optically resolved into individual enantiomers by chemical resolution method using (S)-BINOL as a chiral auxiliary. The partial cone calix[4]arene component plays a crucial role in optical resolution. The title compound may interact enantiodiscriminantly with chiral aminoalcohols, especially 2-phenylglycinol.     

An Interesting Approach to Bis-calix[5]arene Analogue from Calix[6]arene

Calix [n] arenas {n = 4, 6 or 8} are easily prepared from formaldehyde and para-substituted phenols via cyclic condensation under alkaline conditions in one step. It is not surprising that the calyx [n] arene (n = 4, 6, 8) chemistry has been developing very rapidly during the latest 20 years1. However, it is not the case for calixarenes with odd benzene rings (for example, n = 5). The yield of p-tert-butylcalix [5] arene synthesized in one-step from p-tert-butylphenol and formaldehyde was a…     

A sinapic acid–calix[4]arene hybrid selectively binds Pb over Hg and Cd

The binding affinity for Pb²⁺, Cd²⁺ and Hg²⁺ of the sinapic acid–calix[4]arene hybrid 2, having four sinapyl pendants at the upper rim, has been investigated via an UV–Vis study. Compound 2 has better complexing ability than the monomeric p-phenetidine derivative 1. This highlights that the clustering of sinapyl units in a basket-like structure, dictated by the calixarene scaffold, greatly enhances the complexing properties. Ligand 2 forms complexes even with Hg²⁺, which is not complexed by 1 at all; the complexes formed by 2 with Pb²⁺ and Cd²⁺ are much stronger than the analogous complexes formed by 1. The UV–Vis investigation shows that the hybrid 2 markedly favors Pb²⁺ over Cd²⁺ and Hg²⁺. Information on the structural properties of the complex species was obtained by ¹H NMR spectroscopy. NMR data show that all three metal ions are placed into the cavity consisting of the calixarene scaffold and the sinapyl pendants, though their binding affects the coordinating regions to a different extent.     

Synthesis, structure and anion binding properties of lower rim α-hydroxyamide calix[4]arene derivatives

A new family of p-tert-butylcalix[4]arenes functionalized at the lower rim with α-ketoamide or α-hydroxyamide functions has been prepared. The ¹H and ¹³C NMR spectra indicate that the macrocycles preferably adopt a cone conformation. X-ray crystal study of the α-ketoamide derivative 4a shows the flattened cone conformation in the solid state. Reduction of α-ketoamide 4ab has produced the α-hydroxyamide derivatives 6ab. The introduction of chiral moieties on the lower rim position of the calix[4]arene allowed the synthesis of the chiral derivatives 7 and 8. Host-guest complexation properties towards various anions of the chiral α-hydroxyamide 8 have been examined by ¹H NMR spectroscopy. This new receptor has shown promising selectivity for and N-tosyl-(L)-alaninate.     

Phosphate Doubly Capped Tetrahomodioxacalix[6] arene

A bisphosphate-bridged tetrahomodioxacalix[6] arene with a C2v symmetry at the ambient temperature was obtained by the reaction of tetrahomodioxacalix[6] arene with POCl3。     

Fabrication and characterization of calix[4]arene Langmuir–Blodgett thin film for gas sensing applications

Microwave irradiation has been found to be a highly efficient method for etherification of p-tert-butylcalix[4]arene with alkyl bromides or ditosylate. The corresponding products were obtained as a pure form in modest yield within short reaction time when the reactions were performed under microwave irradiation.     

Synthesis and cationic selectivity studies of novel calix[4]arene derivatives containing heteroatom at the lower rim

A series of calixarene derivatives 2―5 containing heteroatom at the lower rim have been synthesized. 1H NMR studies and crystallographic structures demonstrated that the calix[4]arene derivatives adopted cone conformations. Their cationic binding abilities and selectivities towards heavy and tran- sition metal ions have been evaluated by solvent extraction of aqueous metal picrates. The obtained results indicated that the introduction of nitrogen, sulfur, and/or phosphor atoms to the calix[4]arene framework could effectively enhance their binding ability and selectivity for heavy and transition metal ions, such as Pb2 or Ag .     

Kinetics and mechanism studies on scandium calix[6]arene complex initiating ring-opening polymerization of 2,2-dimethyltrimethylene carbonate

Scandium p-tert-butylcalix[6]arene complex has been synthesized from scandium isopropoxide and p-tert-butylcalix[6]arene and used as a single component initiator for the first time. The polymerization of 2,2-dimethyltrimethylene carbonate (DTC) using this complex can proceed under mild conditions. Poly (2,2-dimethyltrimethylene carbonate) (PolyDTC) with weight-average molecular weight of 33700 and molecular weight distribution of 1.21 can be prepared. Kinetics study indicates that the polymeri- zation rate is first order with respect to both monomer and initiator concentrations, and the apparent activation energy of the polymerization is 22.7 kJ/mol. 1H NMR spectrum of the polymer reveals that the monomer ring opens via acyl-oxygen bond cleavage leading to an active center of Sc-O.     

Liquid–liquid extraction and transport through membrane of amino acid methylesters by calix[n]arene derivatives

The extractability together with the transport through liquid membrane of some amino acid methylesters by using p-tert-butylcalix[4]arene as extractant or carrier was studied. In this context, p-tert-butylcalix[n]arenes (n = 6, 8) were found to act as useful carriers or extractant reagents for l-tryptophan methylester and l-tyrosine methylester. The calix[n]arene derivatives used in experiments extracted amino acids methylesters from the aqueous phase into chloroformic phase in the presence of tropaeolin 00 ([4(4′-anilinophenylazo)benzenesulphonic acid]) as counterion at . The extraction and the transport depend on the structure of calixarenes, the structure of amino acids, the pH, and the nature of anion used as ion pair for cation-receptor complexes. The properties of solvent involved in liquid membrane play an important role in membrane stability and also in selecting membrane systems. The results demonstrated that the inclusion properties of the investigated hosts are correlated with their structural properties and also they suggest further possibilities for optimal separation of amino acids derivatives.     

A doubly deprotonated form of calix[6]arene: Crystal and molecular structure of (calix[6]arene-2H)2−·(HNEt 3 + )2

The doubly deprotonated form of calix[6]arene, with two protonated triethylamines as counter-ions, crystallizes in the monoclinic system: space groupP2₁/n,a=8.465(4),b=17.822(8),c=15.182(6) Å,=90.18(4)°,V=2291(2) ų,Z=2. Refinement led to a final conventionalR value of 0.063 for 1046 reflections. The macrocycle conformation is not apinched cone, usual for freeR-calix[6]arene, but a distorted 1,2,3-alternate cone, since the molecule lies on a symmetry center. Furthermore, one of the torsion angles defined by the methylene bridges is near to zero, which is unusual in calixarene structures. Supplementary Data relating to this article (atomic coordinates for hydrogen atoms, anisotropic displacement parameters for oxygen and nitrogen atoms, and observed and calculated structure factors) are deposited with the British Library as Supplementary Publication No. SUP 82182 (7 pages).     

Synthesis and Complexation Properties of Novel Biscalixarene Composed of Calix[4]arene and Thiacalix[4]arene Subunits

Biscalixarenes, as examples of higher order molecular architectures than normal calixarene derivatives, were studied extensively in the recent years due to they possess two calixarene cavities which have the potential for complexing with two guests in two…     

A novel turn-on fluorometric “reporter-spacer-receptor” chemosensor based on calix[4]arene scaffold for detection of cyanate anion

Herein, a novel calix[4]arene compound, which was modified by the 2-(2-aminophenyl)benzothiazole fragment with cyanate recognition function was designed based on the reporter-spacer-receptor sensing system. The construction was done via two-step reaction, and the desired sensor 4 was characterized by FT-IR, ¹H-, ¹³C-NMR, and fluorescence spectroscopy along with HRMS data. The sensor candidate showed distinct fluorometric cyanate detection by means of reporter feature of selected benzothiazole constituent. In the presence of cyanate, the sensor gave a turn-on-type fluorescence at 482 nm with a large stokes' shift. Furthermore, it was observed that our fluoroionophore 4 is highly selective toward cyanate over remaining anions such as sulfate, phosphate, fluoride, chloride, bromide, iodide, chlorate, and nitrate in 10% aqueous solution of DMSO. The 1:2 stoichiometric ratio of the 4 -cyanate complex was given the best fit with Job's plot based on the titration data. The association constant (K_a) of sensor 4 with cyanate is determined to be 1.64 × 10⁵ M⁻². The obtained limit of detection (LOD) value for cyanate anion, 312 nM, clearly revealed the remarkable sensitivity of the chemosensor 4 . This supramolecular method provides a highly adaptive technique for the detection of cyanate and so cyanide ions by current international standard methods.     

A novel triazine‒bearing calix[4]arene: Design,synthesis and gas sensing affinity for volatile organic compounds

A novel triazine-calix[4]arene conjugate was designed and synthesized with the aim to study gas sensing against volatile organic compounds (VOCs) such as dichloromethane, chloroform and carbon tetrachloride. This novel compound was fully characterized by spectroscopic techniques such as FTIR, ¹H and ¹³C NMR along with HRMS and BET analysis. The triazine based calix[4]arene organic materials were fabricated onto quartz glasses and quartz crystal substrates to form a thin film chemical sensor element by using Langmuir-Blodgett (LB) technique. Quartz Crystal Microbalance, UV–Visible Spectroscopy, Atomic Force Microscopy and Scanning Electron Microscopy techniques were employed to characterize all these LB thin film layers. Fick's Equations were used for analyzing the swelling process of LB thin film sensor and diffusion coefficient values of organic vapours for swelling were obtained. The initial experiments have revealed that new triazine appended calix[4]arene derivative exhibited an effective chemical gas sensor characteristic with a large response to dichloromethane vapour.     

Synthesis of Schiff Base Calix [4] arene Crowns

This letter reports the synthesis of Schiff base calix [4] arene crowns containing m-xylylene phenol subunit, in which calix [4] arene Schiff base crowns 2a,2b and 2c were formed by 1:1 condensation of calix [4] arene diamine 1 with dialdehydes (2,6-diformyl-4-chlorophenol 3a,2,6-diformyl-4-methylphenol 3b,2,6-diformyl-4-tert-butylphenol 3c)under high dilute condition in refluxing anhydrous ethanol in 65-70% yield.     

A New Efficient Synthesis of p-Nitrocalix[4]arene

A new efficient synthesis of p-nitrocalix[4]arene from calix[4]arene by using nitrogen dioxide is described.The compound is an useful intermediates for the introduction of other functional groups to obtain N containing substituted calix[4]arene.The reaction mechanism is briefly discussed.