The synthesis of a 1,1'-bi-2-naphthol-based bis(ether anhydride) and aromatic polyimides derived therefrom

2,2'-Bis(3,4-dicarboxyphenoxy)-1,1'-binaphthyl dianhydride was used as a new monomer with various aromatic diamines to obtain polyimides by the usual two-step method. The bis(ether anhydride) was prepared by a nucleophilic substitution of I,1'-bi-2-naphthol with N-phenyl-4-chlorophthalimide, N-methyl-4-nitrophthalimide or 4-nitrophthalonitrile in aprotic polar solvent, and subsequent hydrolysis of the resulting bis(ether imide)s or bis(ether dinitrile), and then dehydration of the corresponding tetracarboxylic acid to afford the dianhydride. Most of the obtained polyimides were soluble in chloroform, pyridine, DMF, etc. The polyimide prepared from p-phenylene diamine was partial crystalline, whereas the others showed amorphous patterns in a WAXD study. These polymers have glass transition temperatures between 255-294 degrees C and 5% weight loss temperatures in the range of 502-541 degrees C in nitrogen and 473-537 degrees C in air. (C) 1997 Elsevier Science Ltd.

Analysis of carbohydrates in a tibetan medicine using new labeling reagent, 1-(2-naphthyl)-3-methyl-5-pyrazolone, by HPLC with DAD detection and ESI-MS identification

A new labeling reagent, 1-(2-naphthyl)-3-methyl-5-pyrazolone (NMP), coupling with liquid chromatography (LC) with electrospray ionization mass spectrometry (ESI-MS) for the detection of carbohydrates from a famous Tibetan medicine is reported. Carbohydrates were derivatized to their bis-NMP-labeled derivatives. The method, in conjunction with a gradient elution, offered a baseline resolution of carbohydrate derivatives on a reversed phase Hypersil ODS-2 column. The carbohydrates such as mannose, galacturonic acid, glucuronic acid, rhamnose, glucose, galactose, xylose, arabinose, and fucose could be successfully detected by UV and ESI-MS. Derivatives showed intense protonated molecular ion at m/z [M+H]+ in positive ion mode. The mass to charge ratios of characteristic fragment ions at m/z 473.0 could be used for the accurately qualitative identification of carbohydrates; this characteristic fragment ion was from the cleavage of C2-C3 bond in the carbohydrate chain giving the specific fragment ions at m/z [MH-CmH2m+1Om-H2O](+) for pentose, hexose, and glyceraldehydes, and at m/z [MH-CmH2m-1Om+1-H2O](+) for alduronic acids, such as galacturonic acid and glucuronic acid (m=n-2, n is carbon atom number of carbohydrate). Compared with the traditional 1-phenyl-3-methyl-5-pyrazolone (PMP) reagent, currently synthesized NMP show the advantage of higher sensitivity to carbohydrate compounds with UV and ESI-MS detection.

Solid and liquid charge-transfer complex formation between 1-methylnaphthalene and 1-alkyl-cyanopyridinium bis{(trifluoromethyl)sulfonyl}imide ionic liquids

Liquid charge-transfer (CT) complexes were observed to form on contacting electron-rich aromatics with electron withdrawing group appended 1-alkyl-4-cyanopyridinium ionic liquids (ILs). Cooling below the melting point of the ionic liquid resulted in crystallisation of ionic liquid from the complex for 2-cyano and 3-cyano pyridinium isomers and in the formation of a 1 : 1 IL : aromatic crystalline CT-complex with the 4-cyanopyridinium isomer. The liquid structure of a 1 : 1 mixture of 1-methyl-4-cyanopyridinium bis{(trifluoromethyl)sulfonyl} imide with 1-methylnaphthalene has been probed by neutron diffraction experiments and molecular dynamics simulations. A high degree of correlation between the experimental data and the simulations was found with a significant displacement of the anions from around the cation by the aromatic species and the resulting structure having pi-pi stacks between the cations and the aromatic.

Are Alkyl Sulfate-Based Protic and Aprotic Ionic Liquids Stable with Water and Alcohols? A Thermodynamic Approach

<p>The knowledge of the chemical stability as a function of the temperature of ionic liquids (ILs) in the presence of other molecules such as water is crucial prior to developing any no GO industrial application and process involving these novel materials. Fluid phase equilibria and density over a large range of temperature and composition can give basic information on IL purity and chemical stability. The IL scientific community requires accurate measurements accessed from reference data. In this work, the stability of different alkyl sulfate-based ILs in the presence of water and various alcohols (methanol, ethanol, 1-butanol, and 1-octanol) was investigated to understand their stability as a function of temperature up to 423.15 K over the hydrolysis and transesterification reactions, respectively. From this investigation, it was clear that methyl sulfate- and ethyl sulfate-based ILs are not stable in the presence of water, since hydrolysis of the methyl sulfate or ethyl sulfate anions to methanol or ethanol and hydrogenate anion is undoubtedly observed. Such observations could help to explain the differences observed for the physical properties published in the literature by various groups. Furthermore, it appears that a thermodynamic equilibrium process drives these hydrolysis reactions. In other words, these hydrolysis reactions are in fact reversible, providing the possibility to re-form the desired alkyl sulfate anions by a simple transesterification reaction between hydrogen sulfate-based ILs and the corresponding alcohol (methanol or ethanol). Additionally, butyl sulfate- and octyl sulfate-based ILs appear to follow this pattern but under more drastic conditions. In these systems, hydrolysis is observed in both cases after several months for temperatures up to 423 K in the presence of water. Therein, the partial miscibility of hydrogen sulfate-based ILs with long chain alcohols (1-butanol and 1-octanol) can help to explain the enhanced hydrolytic stability of the butyl sulfate- and octyl sulfate-based ILs compared with the methyl or ethyl sulfate systems. Additionally, rapid transesterification reactions are observed during liquid-liquid equilibrium studies as a function of temperature for binary systems of (hydrogen sulfate-based ionic liquids + 1-butanol) and of (hydrogen sulfate-based ionic liquids + 1-octanol). Finally, this atom-efficient catalyst-free transesterification reaction between hydrogen sulfate-based ILs and alcohol was then tested to provide a novel way to synthesize new ILs with various anion structures containing the alkyl sulfate group.</p>

On the Performances of Ionic Liquid-Based Electrolytes for Li-NMC Batteries

Herein, the N-butyl-N-methylpyrrolidinium bis(fluorosulfonyl)amide and the N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)amide room temperature ionic liquids, combined with the lithium bis(trifluoromethanesulfonyl)amide salt, are investigated as electrolytes for Li/LiNi1/3Mn1/3Co1/3O2 (Li/NMC) batteries. To conduct this study, volumetric properties, ionic conductivity and viscosity of the pure ionic liquids and selected electrolytes were firstly determined as a function of temperature and composition in solution. These data were then compared with those measured in the case of the standard alkyl carbonate-based electrolyte: e.g. the EC/PC/3DMC + 1 mol·L−1 LiPF6. The compatibility of the selected electrolytes with the lithium electrode was then investigated by following the evolution of Li/electrolyte interfaces through impedance measurements. Interestingly, the impedances of the investigated Li/electrolyte interfaces were found to be more than three times lower than that measured using the standard electrolyte. Finally, electrochemical performances of the ionic liquid-based electrolytes were investigated using galvanostatic charge and discharge and cyclic voltammetry of each Li/NMC cell. Using these electrolytes, each tested Li cell reaches up to 145 mA·h·g−1 at C/10 and 110 mA·h·g−1 at C with a coulombic efficiency close to 100 %.

High temperature vapour-liquid equilibria of water-polyalcohol mixtures

Tese de doutoramento, Química (Química Tecnológica), Universidade de Lisboa, Faculdade de Ciências, 2014

Development of new technologies for the selective removal of volatile compounds with applications in forensic science and natural aromas

Tese de doutoramento, Farmácia (Química Farmacêutica e Terapêutica), Universidade de Lisboa, Faculdade de Farmácia, 2015

Raman spectra of a pseudo-oxocarbon anion in ionic liquids

Raman and electronic spectra of the [3,5-bis(dicyanomethylene)cyclopentane-1,2,4-trionate] dianion, the croconate violet (CV), are reported in solutions of ionic liquids based on imidazolium cations. Different normal modes of the CV anion, nu (C=O), nu (CO) + nu (CC) + nu (CCN), and nu(C N), were used as probes of solvation characteristics of ionic liquids, and were compared with spectra of CV in common solvents. The spectra of CV in ionic liquids are similar to those in dichloromethane solution, but distinct from those in protic solvents such as ethanol or water. The UV-vis spectra of CV in ionic liquids strongly suggest pi-pi interactions between the CV anion and the imidazolium cation. Copyright (C) 2009 John Wiley & Sons, Ltd.

Cobalt catalysts derived from hydrotalcite-type precursors applied to steam reforming of ethanol

Catalysts derived from Co/Mg/Al hydrotalcite-type precursors modified with La and Ce were characterized by XANES and tested in ethanol steam reforming. The reaction data showed that, with a molar ratio of water: ethanol = 3:1 in the feed, addition of Ce and La favored acetaldehyde production. Increasing the water content (water:ethanol = 5:1) decreased the acetaldehyde formation by favoring the adsorption of water molecules on these samples, enhancing the acetaldehyde conversion. (C) 2011 Elsevier B.V. All rights reserved.

Hydrolysis of bis((trimethylsilyl)methyl)tin dihalides. Crystallographic and spectroscopic study of the hydrolysis pathway

The synthesis and characterization by multinuclear NMR spectroscopy of the diorganotin dihalides (Me₃SiCH₂)₂SnX₂ (<b>1</b>, X = Cl; <b>2</b>, X = Br), the diorganotin dichloride water adduct (Me₃SiCH₂)₂SnCl₂&middot;H₂O (<b>1a</b>), the dimeric tetraorganodistannoxanes [(Me₃SiCH₂)₂(X)SnOSn(Y)(CH₂SiMe₃)₂]₂ (<b>3</b>, X = Y = Cl; <b>4</b>, X = Br, Y = OH; <b>5</b>, X = Br, Y = F; <b>6</b>, X = Y = OH; <b>8</b>, X = Cl, Y = OH), and the molecular diorganotin oxide <i>cyclo</i>-[(Me₃SiCH₂)₂SnO]₃ (<b>7</b>) are reported. The structures in the solid state of compounds <b>1a, 3, 6,</b> and <b>7</b> were determined by single-crystal X-ray analysis. In toluene solution, the hydroxy-substituted tetraorganodistannoxane <b>6</b> is in equilibrium with the diorganotin oxide <b>7</b> and water. The eight-membered diorganotin oxide <i>cyclo</i>-[(Me₃SiCH₂)₂SnO]₄ (<b>7a</b>) is proposed to be involved in this equilibrium. On the basis of the results of this and previous works, a general hydrolysis pathway is developed for diorganotin dichlorides containing reasonably bulky substituents.<br />

Lithium doped N-methyl-N-ethylpyrrolidiniumbis(trifluoromethanesulfonyl)amide fast-ion conducting plastic crystals

The incorporation of dopant levels of lithium ions (0.5 to 9.3% by mole) in the <i>N</i>-methyl-<i>N</i>-ethylpyrrolidinium bis(trifluoromethanesulfonyl)amide (P₁₂TFSA) plastic crystalline phase results in increases in the solid state ionic conductivity of more than 3 orders of magnitude at 298 K. Conductivities as high as 10^&minus;-4 S cm^&minus;1 at 323 K have been measured in these doped plastic crystal phases. These materials can therefore be classified as fast-ion conductors. Higher levels of Li only marginally increase the conductivity, up to around 33 mol%, followed by a slight decrease to 50 mol%. Thermal analysis behaviour has allowed the partial development of the binary phase diagram for the LiTFSA&ndash;P₁₂TFSA system between 0&ndash;50 mol% LiTFSA, which suggests the presence of a solid solution single phase at concentrations less than 9.3 mol% LiTFSA. There is also strong evidence of eutectic behaviour in this system with a eutectic transition temperature around 308 K at 33 mol% LiTFSA. A model relating ionic conduction to phase behaviour in this system is presented. The increased conductivity upon doping has been associated with lithium ion motion <i>via</i>⁷Li solid state NMR linewidth measurements.<br />

Novel Lewis-base ionic liquids replacing typical anions

We have synthesized two kinds of new Lewis-base ionic liquids (ILs); one is based on the relatively strong Lewis basic acetate anion, and the other is a salt composed of a mono-alkylated diamine such that the Lewis base site is incorporated in the cation. 1-Octyl-4-aza-1-azonia-bicyclo[2.2.2]octane bis(trifluoromethanesulfonyl)amide, [C₈dabco]TFSA, and <i>N</i>-butyl-<i>N</i>-methylpyrrolidinium acetate, [p_1,4]OAc, melted into fluid liquids at 26 and 81 &deg;C, respectively. The thermal decomposition of [p_1,4]OAc started at around 150 &deg;C, whereas the thermal stability of [C₈dabco]TFSA was almost equal to that of typical TFSA-based ILs in spite of the Lewis base site. This suggests that if the Lewis base site is incorporated into the cation the IL can maintain higher thermal stability. In addition, as a further result of the presence of the basic nitrogen, [C₈dabco]TFSA can dissolve hydrated Cu(NO₃)₂ whereas the other TFSA-based ILs cannot.<br />

Rare earth 3-(4′-hydroxyphenyl)propionate complexes

The reaction of lanthanoid chlorides or nitrates with sodium 3-(4&prime;-hydroxyphenyl)propionate (Na4hpp) in methanol or water has yielded complexes [La4(4hpp)12(H2O)6]&middot;4H2O&middot;MeOH (1), [Ce2(4hpp)6(H2O)3]&middot;(H2O)&middot;2.5(EtOH) (2a) (after crystallization from ethanol), [Ho(4hpp)3(H2O)2] (5), [Er(4hpp)3(H2O)2]&middot;1.5(H2O) (6), and [Lu(4hpp)3]&middot;H2O crystal composition (7), as well as heterobimetallics [NaCe2(4hpp)7(H2O)2]&middot;3(H2O) (2b), [NaPr2(4hpp)7(H2O)2]&middot;3(H2O) (3), and [NaNd2(4hpp)7(H2O)(MeOH)]&middot;(H2O)&middot;3(MeOH) (4). The structures of homometallic complexes 1, 2a, 6, and 7 reveal one-dimensional coordination polymers and vividly illustrate the effect of lanthanoid contraction with a decline in coordination numbers in the series from 9-11 (1), 9,10 (2a), 8 (6) to 7 (7) through variations in carboxylate coordination and ligation of water. Bimetallic complexes 2a and 4 each exhibit five different carboxylate binding modes as well as coordination of the 4-OH substituent of 4hpp to sodium thereby linking 1D polymer chains into a 2D network with both 9 and 10 coordinate Ln atoms and 6 coordinate sodium. Bulk products after drying lose solvent of crystallization in some cases (2a, 6), or exchange MeOH for water (4). X-ray powder diffraction indicates that bulk 2b and 3 are isotypic, as are bulk 5 and 6. In contrast to the excellent corrosion protection of lanthanum 4-hydroxycinnamate, compound 1 is ineffective in preventing the corrosion of mild steel, thereby establishing the importance of the -CHCH- structural unit of the former in its anti-corrosion properties. However the flexible -CH2-CH2- chain of the 4hpp ligand enables the crystal engineering of its lanthanoid complexes in a wide variety of structures as well as effective crystallization for structure determination, whereas the analogous 4-hydroxycinnamates have so far evaded structural characterization except for Ln = La, Ce owing to crystallization problems.

Complexos derivados de 1,1-bis(difenilfosfina)ferroceno : sintese, caracterizacao e propriedades cataliticas

Uma parte importante da química de orgametálicos atual centra-se no estudo de compostos heterobimetálicos com o propósito de avaliar de que modo as possíveis interações entre os metais podem alterar a reatividade dos centros metálicos presentes na molécula. Os ligantes ferrocenilas tem sido bastante utilizados para obter-se compostos desta natureza. Dentro desta classe de ligantes destaca-se o 1,1'-bis(difenilfosfina)ferroceno(dppf). Muitos trabalhos surgiram na literatura nos últimos dez anos descrevendo a síntese, caracterização estrutural, no estado sólido ou em solução, de novos complexos metálicos derivados deste metaloligante, bem como o estudo de suas propriedades catalíticas. O objetivo deste trabalho foi sintetizar novos compostos derivados do 1,1'-bis(difenilfosfina) ferroceno (dppf) e estudá-los no estado sólido ou em solução. Desta forma, foram pela primeira vez sintetizados os compostos dppfFe(NO)2(1), [dppfCo(NO)2][SBf6](2) e dppfNicod(3) e [dppfNi(MeCN)4]2 (4) os quais foram caracterizados por espectroscopia na região do infravermelho, ressonância magnética nuclear de ¹H e ³¹P{¹H}, análise elementar de C,H e N, condutividade molar no caso do composto catiônico(2) e difração de Raios-X de monocristal, no caso do composto(1). A espectroscopia Mössbauer de 57Fe constitui-se uma técnica adequada para a análise deste metaligante, que contém um átomo de Fe na sua molécula, pois pode fornecer informações estruturais e evidenciar eventuais efeitos interativos que ocorram entre os centros metálicos quando o ligante encontra-se complexado a outros metais. Foram, então, estudados por espectroscopia Mössbauer, à baixa temperatura, os compostos (1),(2),(3),(4) e dppfFe(CO)3 (5) e os resultados obtidos comparados com os apresentados na literatura para compostos análogos contendo o ligante dppf. Os complexos derivados do dppf exibem um processo de oxidação centrado no ferroceno além dos processos de oxiredução presentes nos outros centros metálicos da molécula. O estudo das alterações que podem ocorrer neste processo devido à presença de um segundo metal de transição ou dos ligantes é importante pois pode fornecer informações sobre como modular o potencial redox centrado no ligante ferrocenila, permitindo assim um controle de sua reatividade. Sendo assim, neste trabalho foi realizado um estudo eletroquímico, por voltametria cíclica, dos compostos (1),(2) e (5). Compostos de Ni(0) ou Ni(II) são conhecidos catalisadores em reações de oligomerização e polimerização de olefinas e dienos. Compostos ferrodinitrosilas e cobaltodinitrosilas, na presença de redutores, apresentam alta seletividade em reações de ciclomerização de dienos. Nestes sistemas catalíticos a atividade e seletividade doscompostos está intimamente relacionada com a natureza dos ligantes unidos ao metal de transição do percussor catalítico. Devido às características dos compostos sintetizados e estudados neste trabalho, decidiu-se verificar a possível influência do ligante ddpf, na atividade e seletividade das reações com dienos, escolhendo-se o butadieno como substrato modelo. Estudou-se, então, a atividade catalítica dos compostos (1),(2),(3),(4),(5) e dppfNiCl2 (6) frente ao butadieno, na ausência e presença do cocatalisador, AlEt2Cl.

Voltammetric determination of total iron in fuel ethanol using a 1,10 fenantroline/nafion carbon paste-modified electrode

This work presents a methodology for iron determination in fuel ethanol using a modified carbon paste electrode with 1.10 fenantroline/nafion. The electrochemical parameters were optimized for the proposed system and the voltammetric technique of square wave was employed for iron determination. An accumulation time of 5 minutes, such as a 100 mV of pulse magnitude (E(sw)) and frequency (f) of 25 Hz were used as optimized experimental conditions. The modified carbon paste electrode presented linear dependence of amperometric signal with iron concentration in a work range from 6.0x10(-6) until 2.0x10(-5) mol L(-1) of iron, exhibiting a linear correlation coefficient of 0.9884, a detection limit of 2.4 x10(-6) mol L(-1) (n = 3) and amperometric sensibility of 4.5x10(5) mu A/mol L(-1). Analytical curve method was used for iron determination at a commercial fuel sample. Flame atomic absorption spectroscopy was employed as comparative technique.