Comparative spectroscopic and electrochemical study of N-1 or N-2-alkylated 4-nitro and 7-nitroindazoles

Abstract Our research groups are by long time involved in the study of the reactivity and the pharmacological activity of nitrogen-containing heterocyclic compounds: in this line we have now examined the behaviour of some substituted 4- and 7-nitroindazoles. Considering the fact that nitroreduction processes are often essential steps for the biological activity of nitro compounds and remembering that some nitroindazoles show interesting biological activities, we have collected nuclear magnetic resonance, electron spin resonance, and cyclic voltammetry data and carried out density functional theory computations on the above compounds thus obtaining an accurate picture of electronic distribution and reduction processes of the examined substrates as a function of their chemical structure. Looking also to our previous results obtained examining the behaviour of 5- and 6-nitroindazoles, we have confirmed the different general behaviour of 1- and 2-alkyl substituted nitroindazoles strictly related to the known different electronic distribution in these two classes of compounds. Interestingly, cyclic voltammetry data have confirmed the ability of N-1 H nitroindazoles to give rise to the formation of dimers, already observed by us studying 5- and 6-nitroindazoles

LUCE DAI VETRI INFRANTI: GLI ESPERIMENTI DI FILIPPO SCHIASSI (1763-1844)

Il rinnovato interesse dei fisici per l’insieme dei fenomeni che rientrano nel campo della “meccanoluminescenza”, e di cui si hanno notizie fin dal sec. XVII, risale agli anni Ottanta del Novecento e, da quel momento, ha fruttato applicazioni tecnologiche d’avanguardia. Questo articolo illustra un contributo ottocentesco all’interpretazione della “fractoluminescenza”

Carbon electrodes unmodified and decorated with silver nanoparticles for the determination of nitrite, nitrate and iodate

The determination of nitrate and iodate was carried out in samples of mineral water and iodized salt by electrochemical reduction at silver nanoparticles (AgNPs)-modified electrodes. AgNPs were deposited by conventional potentiostatic reduction of a AgNO3solution on flexible pure graphite sheets (PGS) and glassy carbon (GC). The analytical performances of the electrodes based on PGS were comparable to those of modified GC. The novel material can be considered an alternative to the more common glassy carbon. By adding ammonia to the electrodeposition solution it was possible to overcome the problem of Ag+ adsorption on the electrode surface which caused high background currents and prevented measurements in samples with high concentration of Cl-anions. Nitrite determination by oxidation was not feasible on the AgNPs-modified supports, thus this analyte was detected at bare PGS and GC

Pure copper vs. mixed copper and palladium hexacyanoferrates for glucose biosensing applications

A glucose amperometric biosensor was developed. Glucose oxidase enzyme was immobilized by means of a Nafion membrane on glassy carbon modified with an electrochemically deposited mixed Cu and Pd hexacyanoferrate (CuPdHCF). According to the data provided by X-ray atomic spectroscopy measurements, this Cu- and Pd-based hexacyanoferrate is likely to be a mixture of single CuHCF and PdHCF pure phases. The biosensor performances were evaluated by recording the steady-state currents due to submillimolar additions of glucose to a potassium buffer solution (pH 5.5) and exploiting the electrocatalytic reduction of the enzymatically produced hydrogen peroxide. The CuPdHCF-based biosensor exhibited a sensitivity of 8.1\ub10.6 A M 121 m 122, a limit of detection of 1.4 710 125 M, and a linear response range extending between 5 710 125 and 4 710 124 M, with a dynamic response range up to 4 710 123Mglucose. Electrode sensitivity and signal stability resulted more satisfactory as compared to those of a CuHCF-based biosensor fabricated according to the same procedure. The selectivity was investigated through an interference study. The response to easily oxidizable species was found to be low enough to allow glucose determination in biological samples

A Polypyrrole Based Sensor for the Electrochemical Detection of OH Radicals

Polypyrrole was used as sensitive material in the development of a new device employed for the indirect detection of OH radicals. The polypyrrole film was electrosynthesized on glassy carbon. The modified electrode was exposed to the OH radicals generated by Fenton reaction. As a result of the overoxidation the conductivity of the polymer diminished very much. The overoxidation (%) was directly proportional to the .OH amount that reached the electrode surface. ABTS.+, superoxide and alkylperoxy radicals did not interfere in the determination. The applicability of the device was demonstrated by estimating the .OH scavenging ability of ascorbic acid

Electrocatalytic determination of thiols using hybrid Copper Cobalt Hexacyanoferrate modified glassy carbon electrode

An electrochemical sensor based on a glassy carbon electrode (GCE) modified by a thin film of hybrid copper cobalt hexacyanoferrate (Cu-CoHCF) was prepared and tested for the determination of three thiols: l-cysteine (CySH), l-glutathione (GSH) and 1,4-butanedithiol (BdSH). Cyclic voltammetry (CV) measurements were carried out with the as prepared and thermally treated chemically modified electrode (CME) in phosphate buffer solution from pH 2 to 7. From the CV measurements, it was concluded that at pH higher than 5, the Cu-CoHCF layer was unstable and underwent significant fouling when biased at a potential at which the three thiols were electrocatalically oxidized. Following the preliminary CVs chronoamperometric measurements were carried out to determine the optimum conditions to develop an analytical method for the determination of thiols. Cysteine showed the lowest limit of detection (7.5 7 10-7 M), but very low values were displayed also by GSH (2.5 7 10-6 M) and BdSH (2.0 7 10-6 M). The range of linearity extended up to 6.0 7 10-5 M for CySH, 9.0 7 10-5 M for GSH and 1.2 7 10-4 M for BdSH without significant fouling of the CME. The analytical method was applied to the determination of GSH in a nutraceutical purchased from the local market. \ua9 2015 Elsevier B.V. All rights reserved

Copper-cobalt hexacyanoferrate modified glassy carbon electrode for an indirect electrochemical determination of mercury

An electrochemical sensor based on a glassy carbon electrode modified with a hybrid film of copper cobalt hexacyanoferrate was prepared for the indirect electrochemical determination of Hg2+. It exploits the formation of a redox inactive complex with thiols. l-cysteine and 1,4-butanedithiol were used, with the former giving more sensitive results. Interference studies were carried out which led to Cu2+ being the major interferent. Exploiting the fact that the response of l-cysteine to Hg2+ is much more rapid compared to Cu2+, the interference from Cu2+ was avoided or minimized by quick measurement of the amperometric current after the addition of the analyte. The modified electrode showed promising results in detecting Hg2+ in spiked mineral water samples