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21 results on '"Evtuguin, D.V."'

11. Photodegradation of 2-mercaptobenzothiazole and 1,2,3-benzotriazole corrosion inhibitors in aqueous solutions and organic solvents

Author

Serdechnova, M., Ivanov, V.L., Domingues, M.R.M., Evtuguin, D.V., Ferreira, M.G.S., and Zheludkevich, M.L.

Subjects
ddc:620.11
Abstract

The photochemical degradation of 2-mercaptobenzothiazole (MBT) and 1,2,3-benzotriazole (BTA) inhibitors was studied in the present work in aqueous and in organic solutions. The extent of photodegradation was assessed by UV-Vis spectroscopy and the main reaction products were identified by tandem electrospray ionization mass spectrometry (ESI-MS/MS). The analysis of degradation products upon UV irradiation revealed the predominant formation of dimeric compounds from MBT and oligomeric structures from BTA, which were further converted into aniline. The increase of the quantum yield of MBT and BTA photodegradation reactions under aerobic conditions both in aqueous and organic solvents was explained by an increase of the spin–orbit conversion of the singlet radical pairs into the triplet radical pairs in the presence of oxygen. These triplet pairs further dissociate into free radicals, or convert to the parent compounds. At the early stage of UV irradiation, free radical coupling leads essentially to dimer formation in the case of MBT and to the formation of oligomers in the case of BTA irradiation.

Published
2014

21. Synthesis and characterisation of novel ruthenium multi-substituted polyoxometalates: α,β-[SiW9O37Ru4(H2O)3Cl3]7−

Author

Gamelas, J.A.F., Carapuça, H.M., Balula, M.S., Evtuguin, D.V., Schlindwein, W., Figueiras, F.G., Amaral, V.S., and Cavaleiro, A.M.V.

Subjects
*RUTHENIUM compounds, *POLYOXOMETALATES, *ORGANIC compounds, *SOLUTION (Chemistry), *ANTIFERROMAGNETISM, *ELECTROCHEMICAL analysis, *LOW temperatures
Abstract

Abstract: Novel ruthenium multi-substituted polyoxometalate compounds of general formulae K6Na[SiW9O37RuIII 4(H2O)3Cl3]·nH2O (α- and β-SiW9O34 isomers) were synthesised via the reactions of the trilacunary Keggin α- and β-[SiW9O34]10 − anions with RuCl3 in aqueous solution. Characterisation was performed by analytical, spectroscopic, magnetic, and electrochemical techniques. The results are in accordance with the new polyoxometalates having the trivacant Keggin anion (α or β isomer) linked to a cubane-type Ru4O4 cluster. The co-ordination sphere of ruthenium is completed with water molecules and chloride anions. Magnetic measurements showed that the majority of the molecules have the Ru ions cluster in a compensated configuration constrained to an antiferromagnetic alignment at very low temperature and following a Curie-Weiss like behaviour. For both isomers, cyclic voltammetry revealed quasi-reversible redox processes at the ruthenium centres, namely RuIV/III and RuIII/II, which were found to be pH dependent. The novel polyoxotungstates incorporate the highest content of ruthenium (W:Ru=2.25:1) ever reported for Keggin-, Dawson or sandwich-type transition metal-substituted polyoxometalates and may find promising applications as oxidative catalysts. [Copyright &y& Elsevier]

Published
2010
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