Interaction of magnesium ions with semiquinone radicals of tiron used as an indicator of reactive oxygen species

Electron paramagnetic resonance spectroscopy (EPR) and quantum chemical calculations based on density functional theory were used to demonstrate that the earlier observed changes in the EPR spectra of Tiron semiquinone radical dissolved in sea water solution occur due to interaction of Mg²⁺ ions with Tiron radical. This interaction is caused by electrostatic attraction between Mg²⁺ ions and Tiron radicals, which bears great charges of opposite sign (+2 and -3), on the one hand, and due to the ability of Mg²⁺ ion to bind to bidentate oxygen-containing ligands efficiently, on the other hand. The formation of tight contact ion pairs leads to electron and spin density redistribution in the Tiron radical, as can been seen by the observed changes in the EPR spectra of the radical.

Free Radicals, reactive oxygen species, Tiron, water, magnesium chloride, semiquinone, Epr, density functional theory