Antioxidant Activity of MgSO₄ Ion Pairs by Spin-Electron Stabilization of Hydroxyl Radicals through DFT Calculations:...

Magnesium sulfate has been of great interest as an antioxidant for its ability to decrease the oxidizing capacity of the hydroxyl radical. Previously, it was shown that the contact ion pair of this salt could stabilize ^•OH by coordinating with Mg and delocalizing the unpaired electron over sulfate. The present study explores in detail the MgSO₄ antioxidant properties, considering all its ion pairs with ^•OH in different conformations. The analyses were based on structural, spin, and energetic properties using the DFT approach. As a result, the high antioxidant potential of MgSO₄ is related to the spin-electron transfer from SO₄ ^-2 to ^•OH causing electron spin delocalization and electrostatic stabilization. This transfer occurs for all ion pairs when ^•OH approaches the Mg first solvation shell, without being coordinated to Mg. The direct Mg-^•OH interaction further stabilizes the radical system. These results show that spin-electron transfers are feasible in all hydrated ion pairs MgSO₄-^•OH, even at a ^•OH-sulfate distance greater than 10 Å.