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  • 65 Reads
Thermal behaviour of ionogels based on ionic liquid- lithium salt mixtures

The need for efficient batteries for transport, power and industrial applications is growing fast during last years. In this field, ionic liquids (ILs) and inorganic salts mixtures are behind a new generation of active media for energy storage devices, as for example as electrolytes in lithium batteries, and the possibility to confine these mixtures in nano-scaffolds achieving the optimal mechanical properties without loss the ILs particular properties is a major issue.

The thermal behaviour of the mixtures of two protic ionic liquids (ethylammonium nitrate (EAN) and ethylimidazolium nitrate (EIm NO3)) with lithium nitrate salt and one aprotic ionic liquid (butylmethylpyrrolidinium bis(trifluoromethylsulfonyl)imide (C4C1pyrr TFSI)) with lithium bis(trifluoromethylsulfonyl)imide salt at different concentrations was studied in this work using a Differential Scanning Calorimeter (DSC- Q2000-TA Instruments). Comparisons with the thermal behaviour of silica based ionogels of these mixtures were also performed.

Results show that the addition of the salt enlarges the amorphous phase of the fluid especially for both protic ionic liquids with lithium nitrate mixtures which no evidence of crystalline behaviour has been found in saturated mixtures. With regards to the confinement of the mixture on the silica network, one of the most remarkable effects is that thermal behaviour of ionogel does not show the first-order transitions, due to the small available space for the IL crystallization, although as it happens in EIm NO3+Li NO3 mixtures, gel sample also show similar peaks than liquid samples but widened and shifted to lower temperatures. These differences are related with the volume of the pore wall of the ionogel.

  • Open access
  • 79 Reads
Antiradical activity of N'-(1-(2,4-dioxochroman-3-yl)ethyl)-4-hydroxybenzohydrazide-thermodynamic DFT study

In the plant world, coumarins are highly represented heterocyclic compounds. This large class of compounds have found use in the treatment of numerous diseases due to one of its the most important property, and that is a strong antioxidative activity. In this paper, the antioxidative properties of newly synthesized N'-(1-(2,4-dioxochroman-3-yl)ethyl)-4-hydroxybenzohydrazide against the six selected reactive oxygen species (ROS) were investigated. To estimate antioxidative activity, DFT calculations are performed at M06-2X/6-311++G(d,p) level of theory. All calculations are accomplished in the gas phase, and the Gaussian09 software package was utilized. Analysis of the obtained thermodynamic parameters indicate single electron transfer - proton transfer (SET-PT) as not operative mechanism of free radical scavenging. On the other hand, the operative mechanistic pathways for free radical scavenging of all investigated radical species are HAT (hydrogen atom transfer) and SPLET (sequential proton loss electron transfer). One fact is interesting to note, and that is that inactivation of investigated radical species are more favourable when –NH group participates inactivating of mentioned radicals, in regard to –OH group. The difference in ΔGBDE values between the –NH and –OH group is around 40 kJ, and the difference in ΔGPA values is around 15 kJ in favour of –NH group, regardless of radical that is being inactivated. The radical scavenging capacity of N'-(1-(2,4-dioxochroman-3-yl)ethyl)-4-hydroxybenzohydrazide decreases in the following order OH > O(CH3)3 > OCH3 > OOH > OOCH3 > OOCH3CH2.

  • Open access
  • 57 Reads
Determination of thermophysical properties of the protic ionic liquid EIM NO3, pure and doped with lithium nitrate salt

High conductivity and low viscosity are required properties of a material to be considered as a potential electrolyte. The “degree of ionicity” phenomenon in ionic liquids can be quantified and understood in terms of the Walden plot.

In this work, viscosity, density, and electrical conductivity of a protic ionic liquid, Ethylimidazolium nitrate ([EIm][NO3]) pure and doped with lithium nitrate salt were determined or in order to check the possible improvement of the properties of the IL with the salt addition to consider these mixtures as a potential electrolyte, being

Measurements were performed with the following techniques, a TA Instruments AR2000 stress control with a Peltier cooling device and a cone geometry was used for viscosity measurements in a temperature range between (5 and 65) °C and under air atmosphere, density values have been obtained using a vibrating densimeter Anton Paar DSA 5000 and Electrical conductivity has been measured using a conductimeter from CRISON, model GLP31.

As it was expected, viscosity decreases exponentially as temperature increases, and increases with salt content. Similarly, density values decrease linearly as temperature increases, and increases with salt content. From electrical studies an increase of conductivity with temperature and a decrease with salt concentration were observed.

The “degree of ionicity” phenomenon in ionic liquids can be quantified and understood in terms of the Walden plot. From these results, the relationship between the molar ionic conductivity and the reciprocal shear viscosity was analysed through Walden plots in order to determine the utility of these mixtures as potential electrolytes. No significant differences between pure and doped sample Walden plots were observed, being all the analysed samples in the poor ionic liquid region.

  • Open access
  • 163 Reads
Alkynyl N-BODIPYs as reactive intermediates for the development of dyes for biophotonics

BODIPYs are outstanding modern dyes for many photonic applications due to their excellent photophysical properties, which can be adjusted by appropriate chemical modifications of the chromophore structure. To apply them in biophotonics, it is necessary to introduce additional functional groups for bio-recognition or for increasing water solubility, likely the main drawback in BODIPYs. Unfortunately, this is not an easy step in monochromophoric BODIPYs, because the introduction of additional functional groups can severely affect the optimized photophysical properties of the chromophore. In this sense, functionalization at boron should be a useful tool to endow BODIPY dyes with key properties, without affecting the ground photophysical properties of the involved chromophore. In this context, we have recently reported the straightforward preparation of N-BODIPYs, this is, BODIPYs having N-groups at boron, making it possible to introduce up to four different groups at boron through the pending nitrogen atoms. Thus, N-BODIPYs could be an attractive scaffold to engineer smart BODIPYs with multiple functions, which is especially interesting when developing BODIPYs for biophotonics. In this communication, we report a new approach for the rapid multifunctionalization of BODIPY dyes towards biophotonics, based on N-BODIPYs, through reactive intermediates based on alkynyl groups, which can be easily derivatized using click chemistry. This approach has been exemplified by the development of new dyes for cell bio-imaging, which have proven to successfully internalize into pancreatic cancer cells and accumulate in the mitochondria. The in vitro suitability for photodynamic therapy (PDT) was also analyzed and confirmed our compounds to be promising candidates for pancreatic cancer PDT.

  • Open access
  • 102 Reads
ANALYSIS OF THE RELATIONSHIP BETWEEN THE COMPOSITION OF A BRONSTED ACIDIC TASK-SPECIFIC IONIC LIQUID: 1- (4-SULFONIC ACID)-BUTYL-3-METHYLIMIDAZOLIUM HYDROGEN SULFATE ([BSMIM] [HSO4]), AND ITS BEHAVIOR ON REACTIVE SYSTEMS

Ionic liquids (LI) are proposed as an alternative to conventional organic solvents. Among them, there is a subgroup called “task specific ionic liquid” (TSIL), in which a functional group is covalently attached to the cation or to the anion. This is allows to “direct” towards a specific action its chemical properties in a reactive system. In recent years, the 1- (4-sulfonic acid) -3-methyl butylimidazolium [bsmim] with bisulfate counterion [HSO4] is one of the most studied TSIL. This work aims to contribute to a better comprehension of the relationship between the structure of this TSIL and their catalytic behavior. The objective is to identify which part of the structure of the TSIL is responsible for the catalytic action observed in specific reactive systems and to understand how the addition of a functional group such as -SO3H influences on the structure and therefore its behavior. The 1-butyl-3-methylimidazolium [bmim] was also synthesized with the same counterion. Both LIs were tested in two reactive systems: esterification reactions and synthesis of benzoxanthones. The yields obtained were compared with respect to the action of sulfuric acid. Furthermore, cyclic voltammetry was used to identify the species present in the ILs. The results indicate that TSIL show an improved catalytic activity in both types of reactions in comparison with bmim HSO4. The relationship between the voltammetric results and the final performance allowed to interpret the behavior of these LIs. The IL's synthesis and purification method influence on the species present which condition the results on the reactive system.

  • Open access
  • 87 Reads
Does soil organic matter affect the impact of the ionic liquid ethylammonium nitrate in the pure state and as mixture with lithium salt on soil basal respiration?

The exceptional thermophysical properties of ionic liquids (ILs) make these compounds very attractive solvents for different applications, e.g. as the electrolyte in high-voltage batteries, advanced supercapacitors and next-generation fuel cells (owing to the wide electrochemical window and high levels of ionic conductivity and chemical and thermal stability). Thus, research on the electrochemical response of mixtures of ILs with relevant inorganic salts (such as Li, Mg, Ca and Al salts) is currently under way. The negligible vapour pressure of ILs constitutes a further advantage as it means that these materials do not contaminate the atmosphere. Nevertheless, this does not imply that they are not toxic to aquatic or terrestrial environments, and this possibility must be investigated in depth.

This study aimed to assess the toxicity of the IL ethylammonium nitrate (EAN) and of the mixture of EAN and lithium nitrate salt (EAN-LiNO3) by evaluating the impact of different amounts of these materials on soil basal respiration, in two soils of similar texture and pH, but differing in organic matter content. The impact of both EAN and EAN-LiNO3 mixture was more intense in the soil with the low organic matter content than in the soil rich in organic matter. The effects of EAN and EAN-LiNO3 on soil respiration kinetics also differed between both soils. The presence of lithium intensified the toxicity of EAN, especially in the organic matter-poor soil. In addition, soil respiration decreased in a dose-dependent manner in the organic matter poor soil spiked with the highest amounts of EAN-LiNO3.

  • Open access
  • 56 Reads
Synthesis of (2S,3S)-3-aroyl pyroglutamic acid amides

A new methodology for the asymmetric synthesis of enantiomerically enriched 3-aroyl pyroglutamic acid derivatives has been developed through an effective 5-exo-tet cyclization of N-chloroacetyl aroylalanines. The three-step sequence starts with the N-substituted (S,S)-2-amino-4-aryl-4-oxobutanoic acids synthesis via the highly diastereoselective tandem of aza-Michael addition and crystallization-induced diastereomer transformation (CIDT). Their N-chloroacetylation followed by base-catalyzed cyclization and ultimate acid-catalyzed removal of chiral auxiliary without a loss of stereochemical integrity furnishes the target substituted pyroglutamic acids. Finally, several series of their benzyl amides were prepared as 3-aroyl analogues of known P2X7 antagonists.

  • Open access
  • 54 Reads
Synthesis Of polyaromatic heterocycles pyrrolo [1,2-a] indoles by Gold(I)-Catalyzed tandem Cyclization/C-H Activation/Cyclization.

The initial results on a novel procedure for the synthesis of pyrrolo[1,2-a]indoles via gold(I)-catalyzed tandem cyclization/C-H activation/cyclization is described. The procedure allowed access to a highly functionalized pyrrolo[1,2-a]indoles in a one-pot process starting from anilinodiynes.

The mechanism of this reaction by using gold(I) catalysis, interestingly proceeded via 5-endo-dig cyclization at only one of the alkyne of the diyne fragment, leading to the formation of 2-alkynylindole derivative. We are purposing a Csp3-H bond activation and generating gold(I)-carbene species with [1,5]-H migration and cyclization following by [1,2]-H shift.

The synthesis of starting material alkynes was developed. Initially, we started with the addition of Br2 to 2 methylbut-3-yn-2-ol leading to the formation of the corresponding 4-bromo-2-methylbut-3-2-ol. In the next step we were used 4-bromo-2-methylbut-3-2-ol with phenylacetylene gave rise to 2-methyl-6-phenylhexa-3,5-diyn-2-ol. Among we used 2-methyl- 6-phenylhexa-3,5-diyn-2-ol reacted with KOH for evolving acetone and we obtained buta-1-3-diyn-1-ylbenzeze. Further, we treated 2-iodoaniline with benzhydryl bromide we get N-benzhydryl 2-iodoanilne. Then move to the final step for the formation of starting material by taking buta-1-3 -diyn-1-ylbenzeze with N-benzhydryl 2-iodoaniline and we get N-benzhydryl-2-(phenylbuta-1,3-diyn-1-yl).

Initial tandem gold(I)-catalyzed screening was carried out by using highly reactive cationic gold(I)-complex (Echavarren catalyst). Initially, we use between 5-20 mol% then we decided to 5 mol% gold(I) catalyst in DCM at room temperature.

The result we obtained 1-benzhydryl-2-(phenylethynyl)-1-H-indole moiety first cyclization was confirmed by using 1H, 13C NMR spectroscopy, and X-ray. Interestingly we have developed intramolecular cyclization of indole moiety with high yield, short reaction time, and room temperature.

  • Open access
  • 67 Reads
Green synthesis of symmetric dimaleamic acids from dianilines and maleic anhydride: behind new bidentate ligands for MOFs

we herein report the synthesis and spectroscopic characterization of six a,b-unsaturated dicarboxylic acid ligands with different phenyl spacers and two more new ligands with a biphenyl and anthraquinone spacers. All these dimaleamic acids were synthesized in 16 to 99% yields via a base-catalyzed maleimide ring opening in water (ligand 1) or by a di-N-acylation from the corresponding diamines and maleic anhydride in acetic acid (ligands 2 to 8). These reactions were performed using green solvents while requiring minimal work up procedures, making them green alternatives to access quickly to these types of bi-dentate ligands, which can be used to fabricate new MOFs.

  • Open access
  • 65 Reads
Cycloaddition of thiourea- and guanidine- substituted furans to dienophiles. A Comparison of the environment friendly methods

Cycloaddition reaction represent an excellent tool for constructing cyclic systems in a highly regioselective and stereoselective manner. Many biologically and technologically important systems were built upon rigid scaffolds made form one or more norbornene and/or its oxa and aza analogues to mention only the beta-turn mimics and bisporphyrine tweezer -like receptors. It has been claimed that cycloaddition could be a good approach toward chiral diamines. Indeed, one or more superbasic groups attached to such skeleton would be an interesting target molecules.

In this work, we employed cycloaddition strategy to obtain oxanorbornene framework substituted with guanidine moiety or its precursor functional group: protected amine or thiourea. To optimize condition for the cycloaddition, several environmentally friendly methods: microwave assisted organic synthesis (MAOS), high pressure synthesis (HP), high speed vibrational milling (HSVM) and ultrasound assisted (US) synthesis were employed.

In general, our results indicate HP and HSVM approaches as the methods of choice giving good yields and conversions.

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