The extraction of environmentally polluting cations from aqueous media with novel polyamides containing cation‐ and anion‐selective host units

This work describes the synthesis and characterization of polyamides, copolyamides, and polyamide blends containing cation‐ and anion‐selective host units in the pendant structure and their application to the extraction of environmentally polluting cations from aqueous media. The cation host unit consists of a crown ether subunit and the anion receptor is a urea group. The preparation of the copolymers involves the copolymerization of two isophthalic acid derivatives—one containing a lateral urea group and the other a crown ether moiety—with m‐phenylenediamine. The molar ratio of crown ether to urea subunits is varied from 1/1 to 1/2 and 1/3 to fit the ion and counterion ratio of metals with valences I, II, and III. The extraction effectiveness and selectivity is related to the composition of the copolymer or the polymer blend, and thus formally to the cation to anion host units ratio, which therefore permits the á la carte design of materials to be used in the decontamination and elimination of polluting cations. With regard to the cation extraction from aqueous media with polyamide solid phases, the polymer structure design leads to the extraction of high percentages of Hg^II (almost 100%) and moderate extraction of Pb^II and Cr^III. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 670–681, 2009     

Determination of nicotine and N-nitrosamines in house dust by pressurized liquid extraction and comprehensive gas chromatography—Nitrogen chemiluminiscence detection

A novel, highly selective method for the determination of nicotine, N-nitrosamines and tobacco-specific nitrosamines (TSNAs) in indoor dust samples is presented in this study. Samples were extracted by in-cell clean-up pressurized liquid extraction (PLE) that allows high extraction efficiency with moderate consumption of organic solvents. The extracts were analyzed by comprehensive gas chromatography and detected with a nitrogen chemiluminiscence detector (GC × GC-NCD) that provided enhanced selectivity and sensitivity for organic nitrogen containing compounds. Method validation showed good linearity, repeatability and reproducibility (%RSD < 8%). Recovery was higher than 80% for most target compounds and limits of detection lower than 16 ng g^?1. The method was used for the determination of the nitrosamine target compounds in house dust samples from both smoking and non-smoking households. All the analytes were found in the samples, nicotine being the most abundant compound in smokers’ dust and one of the most abundant in non-smokers’ dust. To our knowledge this is the first time that volatile N-nitrosamines and TSNAs have been determined in indoor dust samples. The results demonstrate the presence of these highly carcinogenic compounds in house dust, with inherent human exposure through inhalation and/or involuntary ingestion of house dust.     

Rational Design of a Nonbasic Molecular Receptor for Selective NH4+/K+ Complexation in the Gas Phase

A new molecular receptor ( 1 ) for ammonium recognition has been designed and constructed by using only carbon atoms. This molecular receptor can co‐exist in two different isoenergetic conformations but, upon complexation, the conformers are no longer isoenergetic, and a basket‐shaped conformation becomes clearly more stable. The pre‐organised tetrahedral structure of this basket‐shaped molecule favours the complexation of ammonium ions by N? H???π interactions with the four phenyl groups of the host. A similar behaviour is not observed in a similar, but less pre‐organised, reference molecule. ESI‐MS competition experiments show that 1 is able to bind NH₄⁺ over K⁺ selectively. This is the first example of a neutral molecular receptor that shows a remarkable NH₄⁺/K⁺ selectivity. DFT‐calculations provide insight into the nature of host–guest interactions of both 1? NH₄⁺ and 1? K⁺ complexes as well as in the mechanism involved in multiple cation–π interactions and the influence of these interactions on the conformational stability and the selective binding of the host.     

(Liquid + liquid) equilibria for ternary mixtures of (alkane + benzene + [EMpy] [ESO4]) at several temperatures and atmospheric pressure

In this work, the separation of benzene from aliphatic hydrocarbons (hexane, or heptane) is investigated by extraction with 1-ethyl-3-methylpyridinium ethylsulphate ionic liquid, [EMpy][ESO₄]. (Liquid + liquid) equilibria (LLE) data are determined for the ternary systems: {hexane (1) + benzene (2) + [EMpy][ESO₄] (3)} at T = (283.15, 293.15, 298.15, and 303.15) K and {heptane (1) + benzene (2) + [EMpy][ESO₄] (3)} at T = (283.15 and 298.15) K and atmospheric pressure. The selectivity and distribution coefficient, derived from the tie line data, were used to determine whether the ionic liquid is a good solvent for the extraction of aromatic from aliphatic compounds. The consistency of the tie line data was ascertained by applying the Othmer–Tobias and Hand equations. The experimental results for the ternary systems were well correlated with the NRTL equation. A study of the temperature effect and the influence of the chain length of the alkanes were realized. The results obtained were compared with other ionic liquids. There are no literature data for the mixtures discussed in this paper.     

Vapour pressures and osmotic coefficients of binary mixtures of 1-ethyl-3-methylimidazolium ethylsulfate and 1-ethyl-3-methylpyridinium ethylsulfate with alcohols at T = 323.15 K

Osmotic coefficients of binary mixtures containing alcohols (ethanol, 1-propanol, and 2-propanol) and the ionic liquids 1-ethyl-3-methylimidazolium ethylsulfate and 1-ethyl-3-methylpyridinium ethylsulfate were determined at T = 323.15 K. Vapour pressure and activity coefficients of the studied systems were calculated from experimental data. The extended Pitzer model modified by Archer, and the modified NRTL model (MNRTL) were used to correlate the experimental data, obtaining standard deviations lower than 0.012 and 0.031, respectively. The mean molal activity coefficients and the excess Gibbs free energy of the studied binary mixtures were calculated from the parameters obtained with the extended Pitzer model of Archer.     

Solid-phase micro-extraction procedure for the determination of 1,3-dichloro-2-propanol in water by on-fibre derivatisation with bis(trimethylsilyl)trifluoroacetamide

The headspace solid-phase micro-extraction technique with on-fibre derivatisation followed by gas chromatography-tandem mass spectrometry has been evaluated for the analysis of 1,3-dichloro-2-propanol in water. An asymmetric factorial design has been performed to study the influence of five experimental factors: extraction time and temperature, derivatisation time and temperature and pH. The best extraction performance is achieved in the headspace mode, with 5 mL stirred water samples (pH 4) containing 1.3 g of NaCl, equilibrated for 30 min at 25 °C, using divinylbenzene-carboxen-polydimethylsiloxane as the fibre coating. On-fibre derivatisation has been used for the first time with 50 μL of bis(trimethylsilyl)trifluoroacetamide at 25 °C during 15 min, leading to effective yields. The proposed method provides high sensitivity, good linearity and repeatability (relative standard deviation of 5.1% for 10 ng mL⁻¹ and n = 5). The limits of detection and quantification were 0.4 and 1.4 ng mL⁻¹, respectively. Analytical recoveries obtained for different water samples were approx. 100%.     

Encapsulated ionic liquids (ENILs): from continuous to discrete liquid phase

Encapsulated ionic liquid (ENIL) material was developed, consisting of ionic liquid (IL) introduced into carbon submicrocapsules. ENILs contain >85% w/w of IL but discretized in submicroscopic encapsulated drops, drastically increasing the surface contact area with respect to the neat fluid. ENIL materials were here tested for gas separation processes, obtaining a drastic increase in mass transfer rate.     

Thermally Driven Nanofuses Based on Organometallic Rotors

Molecular design of chromium arenes are theoretically studied as a model for the development of novel thermally‐driven molecular fuses. This study correlates the switching event with a partial disconnection of the molecule from the metallic electrode mediated by changes in the conformational states of the molecule directed by external stimuli. Moreover, the reversibility of the process (the reconnection to the metallic electrode) is also considered for these systems when a reversal voltage pulse (reset) is applied. The energetic requirements of the on and off states are correlated with temperature through the Arrhenius equation. To carry out this study we performed density functional theory (DFT) calculations.     

Cube-type nitrido complexes containing titanium and zinc/copper

Several azaheterometallocubane complexes containing [MTi3N4] cores have been prepared by the reaction of [{Ti(eta5-C5Me5)(mu-NH)}3(mu3-N)] (1) with zinc(II) and copper(I) derivatives. The treatment of 1 with zinc dichloride in toluene at room temperature produces the adduct [Cl2Zn{(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)}] (2). Attempts to crystallize 2 in dichloromethane gave yellow crystals of the ammonia adduct [(H3N)Cl2Zn{(mu3-NH)Ti3(eta5-C5Me5)3(mu-NH)2(mu3-N)}] (3). The analogous reaction of 1 with alkyl, (trimethylsilyl)cyclopentadienyl, or amido zinc complexes [ZnR2] leads to the cube-type derivatives [RZn{(mu3-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N)}] (R = CH2SiMe3 (5), CH2Ph (6), Me (7), C5H4SiMe3 (8), N(SiMe3)2 (9)) via RH elimination. The amido complex 9 decomposes in the presence of ambient light to generate the alkyl derivative [{Me3Si(H)N(Me)2SiCH2}Zn{(mu3-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N)}] (10). The chloride complex 2 reacts with lithium cyclopentadienyl or lithium indenyl reagents to give the cyclopentadienyl or indenyl zinc derivatives [RZn{(mu3-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N)}] (R = C5H5 (11), C9H7 (12)). Treatment of 1 with copper(I) halides in toluene at room temperature leads to the adducts [XCu{(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)}] (X = Cl (13), I (14)). Complex 13 reacts with lithium bis(trimethylsilyl)amido in toluene to give the precipitation of [{Cu(mu4-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N)}2] (15). Complex 15 is prepared in a higher yield through the reaction of 1 with [{CuN(SiMe3)2}4] in toluene at 150 degrees C. The addition of triphenylphosphane to 15 in toluene produces the single-cube compound [(Ph3P)Cu{(mu3-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N)}] (16). The X-ray crystal structures of 3, 8, 9, and 15 have been determined.     

Fluorescent aromatic polyamides with urea binding sites and fluorene or dansyl signaling units

This work describes six novel fluorescent aromatic polyamides with bulky dansyl or fluorene pendant groups or with the fluorene moiety in the main chain. The fluorescent signaling dansyl or fluorene moieties are chemically connected to, or within, the main polymer chains through a urea group, a well-known binding site in supramolecular chemistry. These polyamides are amorphous and soluble in polar aprotic solvents and demonstrate a film-forming capability. They also show yellowish-green or blue fluorescence in solution and in the solid state depending on the signaling unit, with the former corresponding to the dansyl and the latter to the fluorene residue. The water uptake and the thermal behavior have also been evaluated and related to the chemical structure. The polar amide, urea, and sulfonamide groups give rise to a high water sorption of up to 3.8 water molecules per repeating unit. The thermal behavior has been investigated by means of DSC and TGA. The glass transition temperatures of the polymers are high (up to 331 °C) and the decomposition temperatures (around 300 °C) are due to the moderate thermal stability of the urea group.