Design,structure and anion recognition of larger-rim functionalized oxacalix[2]arene[2]triazine hosts

Larger-rim functionalized tetraoxacalix[2]arene[2]triazine host molecules were efficiently synthesized through a fragment coupling followed by AlCl₃-mediated deprotection/arylation protocol. Substituent effects, functions of counter cations on anion recognition in solution were systematically studied by means of fluorescence and NMR titrations.     

Perrhenate and pertechnetate anion recognition properties of cyclo[8]pyrrole

Cyclo[8]pyrrole, an octapyrrolic expanded porphyrin with no meso-linking atoms, was found to interact with a series of anions in the solid state and in a chloroform solution. The anion selectivities have been determined relative to a structurally characterised salt, H₂cyclo[8]pyrrole²⁺·I^? ·I^3 ? , via counter anion exchange. Although cyclo[8]pyrrole demonstrates a general selectivity for sulfate, it interacts well with both the pertechnetate and perrhenate anions. Moreover, it has been shown to act as a phase-transfer catalyst facilitating the extraction of pertechnetate from an aqueous to an organic phase in the presence of sulfate.     

Pyrrolamidocalix[4]arenes: new receptors for anion recognition

Pyrrolamidocalix[4]arenes 1-4, members of a new class of anion receptors bearing pyrrolic units at the upper rim of calix[4]arene macrocycle, have been readily synthesized in good yields. Derivatives 1 and 3, with unsubstituted pyrrole units, show a good selectivity for over F⁻ and AcO⁻, while the presence of electron-withdrawing NO₂ substituents in 2 and 4 inverts the selectivity favoring more basic AcO⁻ and F⁻. In addition, it is demonstrated that the flexibility of calix[4]arene skeleton, present in 1 but absent in 3, is very important in the fitting process that leads the amidopyrrole moieties to wrap the tetrahedral guest.     

Preparation, structure, and anion sensing properties of 1,n-diaza[n]ferrocenophanes

The synthesis of structurally new types of azaferrocenophanes is reported in this note: 4, which comprises a 1,2-fused azaheterocycle to a 1,3-diaza[3]ferrocenophane framework; 1,3-diaza[3]ferrocenophanes 5 and 7, which can be considered as a 1,1'-ferrocenylene N,N'-guanidine or urea, respectively; and 1,3,6,8-tetraza[8]ferrocenophanes 9 and 10, bearing two ureido moieties in the ansa-bridge. These compounds were prepared directly from 1,1'-bis(isocyanato)ferrocene 1 and thoroughly characterized by spectroscopic means. Tetraza[8]ferrocenophanes 9 and 10 show spectral and electrochemical anion-sensing action: they display a selective downfield shift of the urea protons and a cathodic shift of the ferrocene/ferrocinium redox couple with dihydrogenphosphate and fluoride anions. The crystal structure of compound 4 has been determined by single-crystal X-ray methods.     

A [2]catenane containing an upper-rim functionalized calix[4]arene for anion recognition

A novel [2]catenane is synthesized in good yield from an upper-rim functionalized calix[4]arene macrobicycle and a nitro-substituted isophthalamide threading component in the presence of a chloride anion template via a ring-closing metathesis (RCM) reaction. After halide anion template removal the resulting catenane host exhibits a high degree of selectivity for chloride in competitive organic solvent mixtures.     

Self-assembly of 5,11,17,23-tetranitro-25,26,27,28-tetramethoxythiacalix[4]arene with neutral molecules and its use for anion recognition

Methylation of 5,11,17,23-tetranitrothiacalix[4]arene with diazomethane leads to the tetramethoxy derivative, which was studied using single-crystal X-ray crystallography. It revealed that this compound, albeit in the 1,3-alternate conformation, can form the inclusion complexes with various solvent molecules possessing acidic methyl groups (ethyl acetate, nitromethane, acetone, acetonitrile) and creates interesting infinite channels filled with solvent molecules. The subsequent transformation of nitro groups into the ureido moieties gave receptors capable of anion recognition even in a highly HB-competitive solvent like DMSO.     

Synthesis,Characterization, and Crystal Structures of [N(CH3)4]2[B12H12] and [N(CH3)4]2[B12H12] · CH3CN

Bis(tetramethylammonium) dodecahydrododecaborate, [(CH₃)₄N]₂[B₁₂H₁₂], and bis(tetramethylammonium) dodecahydrododecaborate acetonitrile, [(CH₃)₄N]₂[B₁₂H₁₂] · CH₃CN, were synthesized and characterized via Infrared, ¹H and ¹¹B NMR spectroscopy. [(CH₃)₄N]₂[B₁₂H₁₂] crystallizes isopunctual to the alkali metal dodecaborates. The crystal structure of [(CH₃)₄N]₂[B₁₂H₁₂] · CH₃CN was determined from single crystal data and refined in the orthorhombic crystal system (Pcmn, no. 62, a = 898.68(8), b = 1312.85(9) c = 1994.5(1) pm, R(|F| , 4σ) = 5.9%, wR(F²) = 18.3%). Here, the geometry of the dodecaborate anion is that of an almost ideal icosahedron, less distorted than most other dodecaborates known. By low‐temperature Guinier‐Simon diffractometry phase transitions were detected for [(CH₃)₄N]₂[B₁₂H₁₂] and [(CH₃)₄N]₂[B₁₂H₁₂] · CH₃CN at –70 and –15 °C, respectively.     

MCD and absorption spectra of the monovalent anion of tribenzo [12] annulene

The magnetic circular dichroism (MCD) and absorption spectra of the monovalent anion of tribenzo [12] annulene have been measured in the visible and the near-infrared region. The absence of a temperature dependence of the MCD proves a non-degenerate ground state. An assignment of the spectra has been given with the aid of a semi-empirical π-electron calculation (PPP approximation). Influence of the counter ion on optical and ESR spectra was tested by the use of different solvents. No divalent anions could be obtained.     

A novel calix[4]arene-based neutral semicarbazone receptor for anion recognition

A series of novel calix[4]arene-based neutral semicarbazone and thiosemicarbazone receptors have been synthesized and characterized. The molecular receptor 4a recognizes in preference to other anions (Cl⁻, Br⁻, I⁻, , and ) through a 1:1 binding-stoichiometry.     

Synthesis and anion recognition of neutral receptors based on multiamide calyx[4]arene

~~Synthesis and anion recognition of neutral receptors based on multiamide calyx[4]arene~~     

Synthesis and anion recognition of neutral receptors based on multiamide calix[4]arene

Two multiamide calix[4]arenes (5, 6) were synthesized and characterized by NMR, MS and elemental analysis. The binding properties of receptors with some anions (π-O₂NPhOPO₃²⁻, π-O₂NPhO⁻, H₂PO₄⁻, Ac⁻, Cl⁻, Br⁻ and I⁻) were studied by UV-Vis spectra. The results indicate that the tetraamide calix[4]arenes (5, 6) have a good selectivity to the anions containing aromatic ring (π-O₂NPhOPO₃ ²⁻, π-O₂NPhO⁻). The 1 : 1 complexes between host and guest were formed through multiple hydrogen bonding and π-π interactions. The hosts 5 and 6 also show a definite binding ability for the anions (H₂PO₄⁻, Ac⁻, Cl⁻) that have no ultraviolet absorption, which provides a simple method of spectrum detection for these anions.     

双电荷离子[C12H12N2O]2+和[C12H12N2S]2+的气相单分子分解反应研究

The unimolecular dissociation reactions of doubly charged ions were reported,which resulted from a tandem mass spectrometer and a reversed geometry double focusing mass spectrometer by electron impact.Mass analyzed ion kinetic energy spectrometry(MIKES) was used to obtain the kinetic energy releases in charge separation reactions of doubly charged ions.The intercharge distances between the two charges at transition states can be calculated from the kinetic energy releases.Transition structures of unimolecular dissociation reactions were infered from MIKES and MS/MS.     

Hexnut[12]arene and its derivatives: Synthesis,host-guest properties,and application as nonporous adaptive crystals

Hexnut[12]arene(HN[12])and its derivatives,a new class of sixfold macrocyclic arenes,were designed and synthesized in reasonable yield by a one-pot reaction at room temperature using dimethoxymethane as a methylene source.HN[12],which bears a large,symmetric,and rigid cavity,was easily functionalized at both the methylene bridges and the hydroquinone units.A water-soluble fluorescent HN[12]was synthesized and used as a host to encapsulate benzyl viologen dichloride in water with a high binding affinity of(3.4±0.2)×10⁶M^-1.The nonporous adaptive crystal(NAC)of HN[12]was found to capture not only inorganic molecules(iodine)but also trace amounts of large organic molecules(basic fuchsine)from water,which greatly expands the scope of NACs for adsorption.     

氯甲基苯乙烯包夹硅基单柱强阴离子固定相的制备及应用

用氯甲基苯乙烯包夹硅胶基质制备出一种新型强阴离子色谱柱填料,该填料具有良好的色谱性能,可以较好地分离常见的一些无机阴离子;另外,该填料可以对油田中用作驱油剂的单、双石油磺酸盐进行较好的分离。     

A new calix[4]pyrrole derivative and its anion (fluoride)/cation (mercury and silver) recognition

A new calix[4]pyrrole-based macrocycle, meso-tetramethyl-tetrakis{4-[2-(ethylthio)ethoxy]phenyl}calix[4]pyrrole, 7, has been synthesized and fully characterized. Unlike other calixpyrrole derivatives that show selective interaction with anions, calixpyrrole 7 described in the present work forms stable complexes with both metal cations and anions. The thermodynamics of complexation of this ditopic calixpyrrole derivative with metal cations (Hg2+ and Ag+) and the fluoride anion in nonaqueous solutions have been determined by titration calorimetry, and the host-guest composition has been investigated by using conductance measurements at 298.15 K. 1H NMR studies provide clear evidence about the sites of complexation of 7 with the ionic species, which show that the NH groups are taking part in the complexation of this ligand with the fluoride anion while the sulfur donor atoms are responsible for the interaction with metal cations. Using the present data on 7 and structurally related analogues (1-6), the complexation behavior is discussed comparatively from the thermodynamic point of view. Possessing four sulfur-containing pendent arms, 7 displays an enhanced hosting ability for Hg2+ in acetonitrile. As compared with 1, the calixpyrrole derivative, 7, shows a unique interaction with fluoride among the anions investigated in acetonitrile and dimethyl sulfoxide. As far as the fluoride complex is concerned, the medium effect is assessed in terms of the thermodynamics of the transfer of reactants and product from acetonitrile (reference solvent) to dimethyl sulfoxide.     

Spectroscopic and spectrometric studies of anion recognition with calix[4]pyrroles in different reaction conditions

The binding studies of calix[4]pyrroles (1–6) with fluoro, chloro, bromo, iodo and sulphato anions generated from normal-tetrabutylammoniumfluoride, normal-tetrabutylammoniumchloride, normal-tetrabutylammoniumbromide, normal-tetrabutylammoniumiodide, and normal-tetrabutylammoniumsulphate respectively were investigated by electrospray ionization mass spectrometry (ESI-MS) in dichloromethane–acetonitrile in negative ion mode. The efficacy of a particular calix[4]pyrrole to bind with anions was found maximum at low cone voltage of the instrument, at high cone voltage the binding was suppressed due to removal of anion from the cavity of the macrocycles. The binding strength was found inversely proportional to the size of anion for a particular calix[4]pyrrole. The fragmentation pattern of calix[4]pyrrole was observed at higher cone voltage of ESI-MS and was interpreted. The association constants of calix[4]pyrroles and anions obtained from electronic transition studies were in good agreement with that observed from ¹H NMR titration studies.