Structure-Property Relationships in Benzofurazan Derivatives: A Combined Experimental and DFT/TD-DFT Investigation

In this work we seek to understand and to quantify the reactivity of benzofurazan derivatives toward secondary cyclic amines, like pyrrolidine, piperidine and morpholine, acting as nucleophile groups in SNAr reactions. For this aim, physico-chemical and structural descriptors were determined experimentally and theoretically using the DFT/B3LYP/6-31+ g (d,p) methodology. Thus, different 4-X-7-nitrobenzofurazans (X = OCH3, OC6H5 and Cl) and products corresponding to the electrophilic aromatic substitution by pyrrolidine, piperidine and morpholine, were investigated. Particularly, the HOMO and LUMO energy levels of the studied compounds, determined by Cyclic Voltammetry (CV) and DFT calculations, were used to evaluate the electrophilicity index (ω). The latter was exploited, according to Parr’s approach, to develop a relationship which rationalizes the kinetic data previously reported for the reactions of the 4-X-7-nitrobenzofurazans with nucleophiles cited above. Moreover, the Parr’s electrophilicity index (ω) of these benzofurazans determined in this work were combined with their electrophilicity parameters (E), reported in preceding papers, was found to predict the unknown electrophilicity parameters E of 4-piperidino, 4-morpholino and 4-pyrrolidino-7-nitrobenzofurazan. In addition, the relationship between the Parr’s electrophilicity index (ω) and Hammett constants σ, has been used as a good model to predict the electronic effect of the nucleophile groups. Finally, we will subsequently compare the electrophilicity index (ω) and the electrophilicity parameters (E) of these series of 7-X-4-nitrobenzofurazans with the calculated dipole moment (μ) in order to elucidate general relationships between E, ω and μ

Chimie mixte des ions N-acyliminiums, électrochimie organique et de la réaction de métathèse cyclisante : Application à la synthèse de nouvelles structure azapolycycliques hautement fonctionnalisées

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An in Situ Crystal Growth of Metal Organic Frameworks-5 on Electrospun PVA Nanofibers

In this study, a simple, general and straightforward method for growing metal-organic frameworks (MOFs) crystals directly on nanofibers is presented. A chelating polymer was first blent with metal cation and then electrospun. The obtained nanofibers were immersed in a linker solution. Metal cations were released and the metal-organic frameworks crystals were grown on the fibers’ surface. In this work, this method was tested with polyvinyl alcohol as chelating polymer, Zn2+ as metal cation and Terephthalic acid as linker. The pair cation/linker corresponds to the MOF-5. The latter is a robust metal organic framework formed from Zn4O nodes with 1,4-benzodicarboxylic acid struts between the nodes. SEM images revealed that the MOF-5 nanocrystals have grown along the PVA/Zn2+ nanofibers that served as the crystals’ growth template by providing the Zn2+ ions. This result was also confirmed by infrared spectroscopy, which indicates the presence of characteristic bands of MOF-5 in the modified nanofibers spectrum. Moreover, the X-ray diffraction showed that MOF-5 material was well crystallized on the nanofibers surface according to a cubic symmetry with a space group Fm-3m and a lattice constant a = 25.8849 Å

Direct E-DNA sensor of Mycobacterium tuberculosis mutant strain based on new nanocomposite transducer (Fc-ac-OMPA/MWCNTs)

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Effect of Copper on the Oxidation Mechanisms of Tertiary and Secondary Amines of Methyl-naphthyl-cyclen-Modified Gold Electrodes

International audienceTetraazamacrocycle such as 1,4,7,10-tetraazacyclododecane “cyclen” are known for efficient complexation of metallic ions and were used as an ionic recognition agents in chemical sensors in aqueous medium.The aim of this paper is to examine in more detail the oxidation mechanism of amines in cyclen before copper complexation and after copper complexation. Gold electrodes modified with mono-N-MNCyclen(mono methyl-naphtyl-cyclen) and tetra-N-MNCyclen thin films were obtained by deposition of mono-N-MNCyclen and the tetra-N-MNCyclensynthesized respectively by bisaminal route in three steps (protection, N-mono-alkylation and deprotection) and direct route. The comparative study of the electrochemical oxidation of amines in both cyclens allowed the identification of the tertiary and of the secondary amines. From the potential-pH relation and the variation of the intensities of the oxidation peaks, the redox mechanisms of both types of amines was proposed. The electrochemical redox behaviour of the amines in the copper-mono-N-MNCyclen complex was studied. From the potential-pH relation and the variation of the intensities of the oxidation peaks, the redox mechanisms of amines and the structure of the copper-mono-N-MNCyclen complex were proposed. The intensities of the oxidation peaks of the amines vary linearly with the copper concentration, in the range 10−12 M to 10–6 M, leading to a detection limit of of 1 pM of Cu2+

Nanocomposite Based on Poly (para-phenylene)/Chemical Reduced Graphene Oxide as a Platform for Simultaneous Detection of Ascorbic Acid, Dopamine and Uric Acid

In this study, an efficient and simple designed nanohybrid created for individual and simultaneous detection of ascorbic acid (AA), dopamine (DA) and uric acid (UA). This nanohybrid is a combination of chemical reduced graphene oxide (CRGO) and redox poly(para-phenylene) (Fc-ac-PP) modified in a lateral position with ferrrocenyl group CRGO/Fc-ac-PPP. The CRGO/Fc-ac-PPP nanohybrid demonstrated a synergistic effect resulting in a large conductivity, surface area and catalytic properties provided by the redox attached ferrocene. Moreover, this nanocomposite is able to detect individually as well as simultaneously AA, DA and UA in a co-existence system with defined and separated redox peaks oxidation. The linear response ranges for AA, DA and UA, when detected simultaneously, are 0.1–10000 μM, 0.0001–1000 μM and 0.1–10000 μM, respectively, and the detection limits (S/N = 3) are 0.046 μM, 0.2 nM and 0.013 μM, respectively. The proposed sensor shown satisfactory results when applied to real spiked urine samples for measuring the abnormal high or lowconcentration of AA, DA and UA in vivo

Desenvolvimento de um processo tecnológico para a reciclagem de descartes de cabos de fibra óptica

Orientador: Haroldo Araújo PontesDissertação (mestrado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Meio Ambiente Urbano e Industrial, SENAI PR e Universität Stuttgart. Defesa : Curitiba, 05/11/2019Inclui referências: p. 99-105Resumo: O desenvolvimento socioeconômico, os atuais padrões de industrialização e consumo ocasionaram um aumento na geração de diversos tipos de resíduos e, consequentemente, um aumento no descarte destes na natureza, contribuindo para o processo de degradação ambiental. No setor de telecomunicações, com o aumento das instalações em fibra óptica, visando ampliar o acesso à banda larga, são geradas toneladas de sucatas e resíduos anualmente. Neste trabalho é descrito e analisado o desenvolvimento de um processo tecnológico para reciclagem de descartes de cabos de fibra ópticas, o projeto se mostrou complexo, pois não existem na literatura ou no mercado nacional, parâmetros de comparação que abordem o tema da reciclagem dos descartes na sua essência, ou seja, transformar os elementos constituintes dos cabos ópticos em coisas completamente novas. Foram analisadas e descritas às características intrínsecas do material, os volumes de geração, a legislação vigente para os vários tipos de destinação legal, além da descrição destes processos. Também foram pesquisadas e analisadas as opções de máquinas e equipamentos existentes no mercado nacional, que permitiriam o desenvolvimento do processo de reciclagem. A partir destas análises, foi possível iniciar um piloto do processo de reciclagem, que forneceu os parâmetros necessários para análise, e permitiu o avanço no desenvolvimento de um processo eficiente e economicamente viável para reciclagem deste importante resíduo. Atualmente o processo se encontra consolidado e este projeto apresenta as etapas e premissas da operação, mostrando que o mesmo é uma alternativa viável com forte apelo sustentável para tratamento dos descartes de fibra óptica. Palavras-chave: Telecomunicações. Descartes de cabos ópticos. Reciclagem. Desenvolvimento de processo sustentável.Abstract: Socioeconomic development, current patterns of industrialization and consumption have led to an increase in the generation of various types of waste and, consequently, an increase in their disposal in nature, contributing to the process of environmental degradation. In the telecommunications sector, with the increase in optical fiber installations, in order to expand broadband access, tons of waste are created annually. In this work, the development of a technological process for the recycling of scrap from optical fiber cables is described and analyzed. The project was complex because there are no comparative parameters in the literature or in the national market that address the topic of scrap recycling in its essence, that is, transform the constituent elements of optical cables into completely new things. The intrinsic characteristics of the material, the generation volumes, the legislation in force for the various types of legal destination, and the description of these processes were analyzed and described. We also researched and analyzed the options of machines and equipment available in the domestic Market were researched and analyzed, which would allow the development of the recycling process. From these analyzes, it was possible to start a pilot of the recycling process, which provided the necessary parameters for analysis, and allowed progress in the development of an efficient and economically feasible process for recycling this important waste. Currently the process is consolidated and this project presents the steps and premises of the operation, showing that it is a viable alternative with a strong sustainable appeal for the treatment of fiber optic scrap. Keywords: Telecommunications. Scrap optical cables. Recycling. Sustainable process development

A theoretical and electrochemical impedance spectroscopy study of the adsorption and sensing of selected metal ions by 4-morpholino-7-nitrobenzofuran

The selectivity of a novel chemosensor, based on a modified nitrobenzofurazan referred to as NBD-Morph, has been investigated for the detection of heavy metal cations (Co2+, Pb2+, Mg2+, Ag+, Cu2+, Hg2+, Ni2+, and Zn2+). The ligand, 4-morpholino-7-nitrobenzofurazan (NBD-Morph), was characterized using spectroscopic techniques including FT-IR and 1H NMR. Vibrational frequencies obtained from FT-IR and proton NMR (1H) chemical shifts were accurately predicted employing the density functional theory (DFT) at the B3LYP level of theory. Furthermore, an examination of the structural, electronic, and quantum chemical properties was conducted and discussed. DFT calculations were employed to explore the complex formation ability of the NBD-Morph ligand with Co2+, Pb2+, Mg2+, Ag+, Cu2+, Hg2+, Ni2+, and Zn2+ metal cations. The comparison of adsorption energies for all possible conformations reveals that NBD-Morph exhibits sensitivity and selectivity towards metal ions, including Pb2+, Cu2+, Ag+, and Ni2+. However, an assessment of their reactivity using QTAIM topological parameters demonstrated the ligand's greater complexation ability toward Cu2+ or Ni2+ than those formed by Pb2+ or Ag+. Additionally, molecular electrostatic potential (MEP), Hirshfeld surfaces, and their associated 2D-fingerprint plots were applied to a detailed study of the inter-molecular interactions in NBD-Morph-X (X = Pb2+, Cu2+, Ag+, Ni2+) complexes. The electron localization function (ELF) and the localized-orbital locator (LOL) were generated to investigate the charge transfer and donor-acceptor interactions within the complexes. Electrochemical analysis further corroborates the theoretical findings, supporting the prediction of NBD-Morph's sensory ability towards Ni2+ metal cations. In conclusion, NBD-Morph stands out as a promising sensor for Ni2+