Study on the Quenching Mechanism of Radicals by Fullerenes (C₆₀ and C₇₀)

Although fullerenes are well-recognized for their exceptional radical-quenching abilities, the molecular-level mechanisms governing their interactions with free radicals remain unclear. Herein, the interactions between C₆₀/C₇₀ and 16 representative radicals were systematically investigated using density functional theory (DFT). The calculated binding energies (-10.21 to -51.26 kcal·mol^-1) indicate strong and thermodynamically favorable radical-fullerene associations. Frontier orbital and spin-density analyses reveal that fullerenes act as electron acceptors, facilitating electron transfer from radicals and stabilizing their electronic states. Ab initio molecular dynamics (AIMD) simulations of five typical radicals (^•OH, ^•OOH, CH₃OO^•, Ph₃C^•, and DPPH) further uncover time-resolved quenching behavior, where spin populations at radical sites rapidly decrease to nearly zero, confirming single-electron transfer as the dominant quenching pathway. Mayer bond-order analysis shows the transient formation of weak covalent bonds enabling reversible radical capture. Complementary electron paramagnetic resonance (EPR) spin-trapping experiments validate these theoretical findings, demonstrating that C₆₀ effectively quenches hydroxyl radicals generated from H₂O₂ photolysis. Moreover, transition-state calculations reveal that C₆₀ catalytically promotes H₂O₂ decomposition by reducing the reaction barrier while maintaining structural integrity. These combined results establish a dual-function mechanism of electron-transfer-driven radical quenching and catalytic ROS decomposition, providing a theoretical foundation for designing fullerene-based antioxidant materials.