H2O2 ACTIVATION AND FREE RADICALS PRODUCTION USING NOVEL NON-SOLUBLE COMPLEXES WITH Co(II) AND Cu(II)

L. V. LOMBARDO LUPANO; J. M. LÁZARO MARTÍNEZ; L. L. PIEHL; E. RUBIN DE CELIS; V. CAMPO DALL' ORTO

Rosario

Taller; Taller fronteras en resonancia magnética: de los materiales a los sistemas biológicos.; 2013

IBR - CONICET

Chemically stable Co(II) and Cu(II) coordination complexes were prepared with a non-soluble polyampholyte Poly(EGDE-MAA-2MI) and a non-soluble polyelectrolyte Poly(EGDE-DA). These polymers were synthesized from ethyleneglycol diglycidyl ether (EGDE), combined with methacrylic acid (MAA), 2-methylimidazole (2MI) [1], and 1,8-diamino-3,6-dioxaoctane (DA). The catalytic activity of these materials on H2O2 activation was studied by Electron Spin Resonance (ESR). The Co(II)-Poly(EGDE-MAA-2MI) / H2O2 and the Co(II)-Poly(EGDE-DA) / H2O2 heterogeneous systems produced free radicals that diffused into the solution and were detected by spin trapping experiments with DMPO. The simulation and fits of the experimental spectra allowed establishing the presence of two species: DMPO/OOH and DMPO/OH adducts from anion superoxide and hydroxyl radical, respectively. The addition of the enzyme superoxide dismutase (SOD) to each medium of reaction gave rise to spectra with the characteristic shape of DMPO/OH. On the other hand, the formation of O2 in parallel was confirmed with an electrochemical sensor, and a decrease of pH was detected. Based on this experimental evidence, we propose a reaction of H2O2 activation catalyzed by immobilized Co(II), with the production of O2, anion superoxide and H+. In the same way, the Cu(II)-Poly(EGDE-MAA-2MI) / H2O2 and the Cu(II)-Poly(EGDE-DA) / H2O2 heterogeneous systems produced O2 and free radicals detected by spin trapping experiments with DMPO. The pH did not suffer significant variation at the time that the partial pressure of O2 increased together with the concentration of free radicals. The simulation and fits of the experimental spectra allowed establishing the presence of the DMPO/OH adduct from hydroxyl radical. Based on this evidence, a possible reaction was postulated. The necessary presence of a certain amount of Cu(I) to support this mechanism was detected in Cu(II)-Poly(EGDE-MAA-2MI) by X-ray photoelectron spectroscopy.