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  • Open access
  • 30 Reads
Immobilization on cellulose paper of a chemosensor for CdSe‑Cys QDs

Cadmium-based QDs are one of the most widely used semiconducting QDs, as they have useful properties for biochemical sensors, biomedical imaging, photovoltaic applications, light-emitting diodes (LEDs), laser, thin-film transistors, or solar cells. A clear negative consequence of this extensive use is the discharge into the environment of such noxious material. To prevent their uncontrolled discharge, it is essential to develop simple methods to detect them in waste or even in the environment. The implementation of paper sensors for color analysis provides fast response, simple operation, and low cost in the detection of CdSe QDs.

Here we report the immobilization on cellulose paper of a previously reported [1] chemosensor for CdSe‑Cys QDs. The cellulose paper was first primed with 3-aminopropyl)trimethoxysilane (APTMS) by soaking it in a DMF solution for 2 h. In a second reaction step, N-hydroxysuccinimide (NHS) and N-(3-dimethylaminopropyl)-N´-ethylcarbodiimide hydrochloride (EDC·HCl) were added together with the chemosensor to achieve its immobilization on the amine-modified paper (by forming an amide bond) [2].

The observation of three dominant signals located around 270, 330 and 420 nm in the diffuse reflectance spectrum of the chemosensor-modified paper demonstrated its immobilization. The absorption bands appear around 50-80 nm red-shifted, with respect to the spectrum of an ethanol solution of the chemosensor (220, 250 and 340 nm).

The chemosensor-modified cellulose paper upon soaking in CdSe-Cys QDs water solutions for 2 h exhibits a decrease in the absorbance of each band of the diffuse reflectance spectrum. As the decrease is more pronounced in the band observed at 270 nm, we have chosen this wavelength to carry out the measurements.

To study the interaction between CdSe-Cys QDs and the chemosensor (H2SB), we obtained Cd2(SB)2(H2O)4 in solution and compared its UV-Vis spectrum with that of the reaction product between H2SB and CdSe-Cys QDs. The similarities between these spectra evidenced an interaction via metal-ligand coordination between CdSe-Cys QDs and H2SB.

  • Open access
  • 89 Reads
I2 catalyzed DMSO oxidation of Se-Se bond activated by the use of SynLED Parallel Photoreactor ®

Among different green oxidative protocols, I2 catalyzed DMSO systems have recently received considerable attention being greener, efficient, atom-economical, low-cost, and offering the possibility to perform reactions under safe and mild conditions. Particularly interesting is the application in the chalcogen-chalcogen bond activation that allows the in-situ formation of electrophilic species promoting a number of Se-C bond formation. In these reactions’ iodine acts a catalytic oxidant continuously regenerated by the DMSO that can be used in stoichiometric amount under solvent free conditions. Methoxyselenylation reactions can be performed at room temperature but the reaction takes over 24 hours to reach appreciable conversion yields. In this paper the activation by the use of a SynLED Parallel Photoreactor® is investigated as an alternative energy source and the results are critically compared with with those previously reported in literature.

  • Open access
  • 28 Reads
Cyclopalladated compounds with bulky phosphine : Synthesis, characterization

In recent years, phosphine ligands have received a lot of attention, and are widely employed in transition metal chemistry as chelating and bridging coordination modes ligands. hence several mononuclear phosphine–type compounds have shown interest in homogeneous catalysis. These diphosphines ligands are useful in metal-catalyzed processes, thus imine ligands and bulky phosphines have been successfully described.

  • Open access
  • 30 Reads
Fe-catalyzed synthesis of 2-benzoxazolone - an important fragment of biologically active compounds

2-Benzoxazolone, as well as its derivatives, are valuable structural fragments of a number of important biologically active substances. Benzoxazolone derivatives are promising as antitumor, antimicrobial, antiretroviral, anticonvulsant, tranquilizing and insecticidal agents. 2-Benzoxazolone is usually produced by the condensation of o-aminophenol with urea, phosgene, and other carbonic acid derivatives. There are also methods for the synthesis of 2-benzoxazolone from salicylamide with trichloroisocyanuric acid as a chlorinating agent, from hydroxybenzoic acid using ammonium azide and Vilsmeier complex. The disadvantages of these methods are: the high cost of the initial reagents, the need to use aggressive and
toxic reagents (phosgene, ammonium azide) and complexity of hardware design for reactors. We have developed highly efficient oxidative cyclocarbonylation of 2-aminophenol to oxazolidin-2-one using FeCl3*6H2O and Fe(acac)3 as catalysts under relatively mild conditions (100–120 °C, atmospheric pressure) in the presence of CCl4 and water. We assume that in situ formed carbon dioxide is involved into a cyclization reaction with o-aminophenol to form the target benzoxazole. The reaction takes 3-10 hours to give 2-benzoxazolone in high yield.

  • Open access
  • 32 Reads
Synthesis ethyl 2-(1H1,3-benzodiazol-2-ylsulfanyl)acetate
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Abstract. 1H-benzo[d]imidazole-2-thiol derivatives are structural isomers of natural nucleotides, which allow easy interaction with biopolymers of living organisms. Therefore, it is urgent to synthesize new derivatives of Mercapto benzimidazole and study their chemical properties. As a result of further experiments, a new derivative of benzimidazole was synthesized and its structure was analyzed using physical and chemical research methods.

  • Open access
  • 31 Reads
A Facile Method for Assessing the Change in Detonation Properties during Chemical Functionalization: The Case of NH2→NHNO2 and NH2→=N+=N Conversions

A simple and fast procedure for estimation of the effect of chemical functionalization on the change in detonation properties of energetic materials is reported. The procedure consists of two levels: the first level is the calculation based on atomic increments and can be performed with a pocket calculator. This level indicates a pool of possible chemical structures, which can be significantly improved in detonation properties by the given chemical transformation. At the second level, quantum-chemical calculations provide accurate estimates of the change in detonation properties taking into account exact chemical structures. Quantum-chemical calculations at Level 2 are aimed to obtain crystalline density (dc) and solid-state enthalpy of formation (ΔHf) and include the following sequence of computational tasks: vacuum-isolated molecule relaxation (PBE/DND) → crystal structure prediction (COMPASSII) → crystal cell relaxation (PBE/DND). The method is well-calibrated on the available experimental data providing high regression qualities (R2 > 0.9) and is reliable. Thus, we have analyzed transformation of both aromatic and aliphatic amines into the corresponding nitramines and diazo compounds. The calculations at Level 1 indicate that both dc and ΔHf are always positive and increase detonation properties, while the calculations at Level 2 indicate the specific amines, which are the most sensitive to such chemical transformation, whose detailed description is presented in the full paper.

  • Open access
  • 47 Reads
Electrochemical Synthesis of Imidazopyridine and Benzylidene Malononitrile

One-pot electrochemical synthesis of two medically targeted well-known compounds is presented. 2-phenylimidazo[1,2-a]pyridine and 2-(4-flurobenzylidene)malononitrile were prepared using previously used starting materials. The reaction consists of electrochemical methods without adding further reagent which delivers the products with about 82-90% of yield at 5.0V which leads to a different approach to synthesize important organic moieties with efficient pathways.

  • Open access
  • 31 Reads
An unexpected result of base-promoted rearrangement of 4a-acetyl-8a-hydroxydecahydroquinazoline-2-thione

Treatment of 4a-acetyl-8a-hydroxydecahydroquinazoline-2-thione with NaH in acetonitrile leads to its isomerization into 1-hydroxy-1-methyl-3-thioxo-2,4-diazaspiro[5.5]undecan-7-one followed by the C1-C6 bond cleavage to give N-acetyl-N¢-[(2-oxocyclohexyl)methyl]thiourea. The starting compound as a single diastereomer was prepared by the reaction between the K-enolate of 2-acetylcyclohexanone and N-(tosylmethyl)thiourea or N-(azidomethyl)thiourea.

  • Open access
  • 64 Reads
Parallel synthesis of structurally diverse heterocycle compounds using microwave assisted three component reaction.
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Among the biologically active compounds, heterocyclic macromolecules are considerable importance. They offer a new approach to drug discovery by enabling the development of a simple and efficient method of synthesizing compounds containing diverse heterocyclic structures. In addition, these compounds play an important role in the design of pharmaceutical products. Among them, those containing nitrogen, sulphur and oxygen have attracted the interest of medicinal chemists due to their innumerable biological applications.

Our research group studied the synthesis of heterocycle macromolecules substituted with a protected carbohydrate moiety via microwave assisted three-component reaction. Taking into account our study’s results, we present here a new proposal for the “one pot” generation of new heterocycle compounds such as 4-thiazolidinones (I), 1,4-thioazepan-3-ones (II) and 1,3-oxathiolan-5-ones (III) using ethanol, water or benzene as reaction solvents. All compounds were characterized by GC-MS and NMR techniques, and available crystals by X-Ray diffraction studies.

This study not only extends previous work on the scope of substrates, but also provides further insight into the chemistry of such drug scaffolds.