Anion binding in (arene)ruthenium(II)-based hosts?

Asymmetric ruthenium(II) complexes of a flexible aminomethylpyridine derivative exhibit diastereotopic ligand methylene protons, as measured by NMR spectroscopy; binding of external anions renders these protons equivalent possibly by increasing dynamically averaged symmetry; the amount of anion needed to raise average symmetry correlates to the anion binding constant.     

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…     

Synthesis, Structure and Alkali Metal Ion Binding Properties of a Podand Polyether Derived from Calix[4]arene, 5,11,17,23-tetra-tert-butyl-25,27-di(phenylmethoxy)-26,28-di(2‘-methoxyethoxy)-calix[4]arene

The ligand 5,11,17,23-tetra-t-butyl-25,27-di(phenylmethoxy)-26,28-di(2-methoxy-ethoxy)calix[4]arene,designed as an analogue of some calixcrown speciesin order to evaluate possible origins of their selectivity in alkali metal ion binding, has been synthesised and structurally characterised by X-ray crystallography. The crystals are monoclinic, P21/n, a = 15.940(6), b = 19.388(5), c = 20.020(5) Å, = 109.10(2) deg., Z = 4, conventional R on |F| being 0.073 for 3454 independent, observed (I > 3(I)) reflections. 1H-NMR studies in 1:1 CD3CN/CDCl3solvent have shown that the ligand exerts a strong preference for the lighteralkali metal ions (Li+ and Na+) contrary to the binding behaviour of knowncalixcrowns. This may reflect interactions restricted to the lower rim donor atoms without concomitant interaction with the calixarene -electrons, perhaps because the latter interactions are substituted by those with the benzyl group -electrons.     

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.     

Regioselective alkylation of the lower rim of p-tert-butylthiacalix[4]arene with N-(p-nitrophenyl)-α-bromoacetamide

The preparation of partially substituted thiacalix[4]arenes 2–6 has been accomplished by conducting the reaction of the thiacalixarene 1 with N-(p-nitrophenyl)-α-bromoacetamide in acetone or acetonitrile in the presence of M₂CO₃ (M = Na, K and Cs). The influence of the reaction conditions (temperature, time, solvent, ratio of the reagents and the nature of the alkali metal carbonate) on regio- and stereoselectivity of this reaction is described.     

Anodic Stripping Voltammetric Determination of Lead(II) Using Glassy Carbon Electrode Modified with Novel Calix[4]arene

Owingtothegrowingawarenessofleadpollutionandtoxicity,manytechniquesarecurrentlyemployedforthedeterminationoftracePbioninenvironmentalsamples .1Amongthem ,thedevelopmentofchemicallymodifiedelectrodes (CMEs)andapplicationsofanodicstrippingvoltammetry (ASV)havereceivedconsiderableattention .CMEsarecharacterizedbypurposefullyalteringtheirsur facecharacteristicstodisplaynewqualitiesthatcouldbeexploitedforanalyticalapplications .Thesekindsofelec trodesareinexpensiveandpossessmanyadvantagessuchas…     

Reactions of (arene)tricarbonylchromium stabilized carbocations with aromatics and β-dicarbonyl compounds

Primary and secondary benzylic carbocations, stabilized by a tricarbonyl-chromium group, gave coupling products with several aromatics or β-dicarbonyl compounds in good yield and this reaction presents a new synthetic method for carbon-carbon bond formation. The chromium complexes of tertiary benzyl alcohols gave dehydrated products without carbon-carbon coupling products under similar conditions.     

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.     

Controllable self-assemblies of β-cyclodextrin-calix[4]arene couples

Amphiphilic cyclodextrin-calixarene conjugates 1 and 2 were synthesized from "click chemistry", and their self-assembly behaviors were investigated by transmission electron microscopy, and atomic force microscopy. The results obtained show that 1 and 2 can self-assemble to form distinctly different aggregations, and the morphology of aggregations critically relies on the polarity and hydrophilicity of the solvent.     

Bis(arene)metal compounds: I. Nucleophilic substitution of bis(η6-chlorobenzo-trifluoride)chromium(0) with thiophenoxide

The ortho, meta and para complexes of bis(η⁶-chlorobenzotrifluoride)chromium(0) were made by metal-vapor synthesis. Nucleophilic substitutions by thiophenoxide of these complexes are compared to nucleophilic substitutions by thiophenoxide on the uncoordinated arenes. It was found that substitution at the chloro position is more facile on the complexes than on the free arenes. Substitution of the chloro on the meta-isomer sandwich was more facile than substitution of the chloro on the ortho-isomer sandwich, contrary to the observed reactivity pattern in the free arenes.     

Inherently chiral biscalixarene cone–cone conformers consisting of calix[4]arene and calix[5]arene subunits

Inherently chiral biscalixarenes with hetero-cavities were synthesized by a covalent assembly of p-tert-butylcalix[5]arene with a 1,3-substituted calix[4]arene via 1,3-alkylation reaction and subsequent desymmetrization. The racemates were resolved by chiral HPLC method. ¹H NMR spectra, VT-NMR spectra, and theoretical calculations support that the calix[5]arene subunit of the inherently chiral calix[4][5]arene ester adopts a cone-in conformation, with the aromatic ring bearing the CH₂CO₂Et group tilting inward the calix[5]arene cavity. By contrast, such a cone-in structural feature of the calix[5]arene subunit disappears for the corresponding inherently chiral calix[4][5]arene carboxylic acid, due to the intramolecular hydrogen bonding between the carboxyl group and an ethereal oxygen of the glycolic chain.     

Metal-organic supramolecular nanoarchitectures by Ru(Ⅱ)bis-(terpyridine)-bridged pillar[5]arene dimers with triphenylamine

A metal-organic photoinduced electron transfer(PET) supramolecular nanoarchitecture comprised of Ru(Ⅱ) bis(terpyridine)-modified pillar[5]arene(electron acceptor) and triazole triphenylamine amyl cyanide(electron donor) has been designed and constructed.Through the comparison of diverse solvents and acceptors,the two conditions,i.e.,modification of pillar[5]arene to donor and weak polar solvent are benefit for the occurrence of "efficient PET" because of shorter D-A distance in the presence of pillar[5]arene.Crucially,the fluorescence and PET process of the supramolecular assembly could be further modulated by solvent conversion and another competitive guest.The study provides a supramolecular method to design and construct tunable PET systems and PET-based smart materials.     

Accessing highly electron-rich calix[n]arene (n = 4 and 8) derivatives from acid-catalyzed condensation of 1,3,5-tripropoxybenzene

Synthesizing novel electron-rich calix[n]arene derivatives to alter the electronic properties of calixarene-based materials has been one of the long-standing interests. Herein, two new electron-rich calix[n]arenes (n = 4 and 8) with different sizes were synthesized by acid-catalyzed condensation reaction of 1,3,5-tripropoxybenzene and paraformaldehyde. Both derivatives were fully characterized with ¹H and ¹³C NMR, mass spectrometry and X-ray crystallography. Furthermore, their electrochemical properties and oxidized product (cation radicals) have also been investigated.     

Synthesis of Calix[4]arene Derivatives with NLO Properties

The new chromophore compounds with NLO properties were prepared by Knoevenagel condensation from forrnyl or diformyl calix[4/arene and isophorone derivatives in the presence of piperidine and acetic acid, respectively. In these chromophore calix[4]arenes, the ring locked trienes were employed as the conjugation bridge and electron acceptor in D-π-A units. The NMR spectra demonstrated that they existed in a cone conformation and consequently non-conjugated D-π-A units could be oriented at nearly the same direction.     

SYNTHESES AND CRYSTAL STRUCTURES OF (Et_4N)_2(Fe_2Se_2(SPh)_4) AND (Et_4N)_2(Fe_4Se_4Cl_4)

<正> Since the discovery of iron-sulfur proteins , a number of analogous compounds of the active sites of iron-sulfur proteins has been synthesized and characterized . Due to the similarity between sulfur and selenium, some selenoproteins with similar active site as iron-sulfur proteins were found . We have synthesized a series of iron-selenium compounds in correlative study with the iron-sulfur compounds. In this paper, we will discuss the syntheses and crystal stuctures of the title compounds. The spectroscopic properties of these compounds have been under investigation.