维生素C对菲醌三重激发态的淬灭机理及动力学研究

TR-ESR Investigation on Reaction of Vitamin C with Excited Triplet of 9,10-phenanthrenequinone in Reversed Micelle Solutions

Time-resolved electron spin resonance has been used to study quenching reactions between the antioxidant Vitamin C (VC) and the triplet excited states of 9,10-phenanthrenequinone (PAQ) in ethylene glycol-water (EG-H₂O) homogeneous and inhomogeneous reversed micelle solutions. Reversed micelle solutions were used to be the models of physiological environment of biological cell and tissue. In PAQ/EG-H₂O homogeneous solution, the excited triplet of PAQ (³PAQ*) abstracts hydrogen atom from solvent EG. In PAQ/VC/EG-H₂O solution, ³PAQ* abstracts hydrogen atom not only from solvent EG but also from VC. The quenching rate constant of ³PAQ* by VC is close to the diffusion-controlled value of 1.41×10⁸ L/(mol·s). In hexadecyltrimethylammonium bromide (CTAB)/EG-H₂O and aerosol OT (AOT)/EG-H₂O reversed micelle solutions, ³PAQ* and VC react around the water-oil interface of the reversed micelle. Exit of ³PAQ* from the lipid phase slows down the quenching reaction. For Triton X-100 (TX-100)/EG-H₂O reversed micelle solution, PAQ and VC coexist inside the hydrophilic polyethylene glycol core, and the quenching rate constant of ³PAQ* by VC is larger than those in AOT/EG-H₂O and CTAB/EG-H₂O reversed micelle solutions, even a little larger than that in EG-H₂O homogeneous solution. The strong emissive chemically in-duced dynamic electron polarization of As^- resulted from the effective TM spin polarization transfer in hydrogen abstraction of ³PAQ* from VC.