Quenching Reaction Investigation On The Photoinduced Excited Triplet States Of Vitamin K₃

Biologic quinones such as vitamin K3are derivatives of1-4Naphthoquinone. Investigation on the quenching mechanism and dynamics of the excited triplets of VK3(3VK3*) is significant for comprehension of the biologic antioxidation reaction and antioxidation mechanism. In this dissertation, based on the brief introduction of chemically induced dynamic electron polarization (CIDEP) mechanism, time resolved-ESR and transient absorptive spectrum, the quenching reaction of3VK3*by TEMPO and antioxidant vitamin C in ethylene glycol (EG-H2O, v:v=9:1) homogeneous and its TX-100(AOT、CTAB、 SDS) micelle solutions have been investigated. The main works are:(1) The quenching reaction of3VK3*with TEMPO in ethylene glycol homogeneous has been investigated. The CIDEP spectrum and transient absorptive spectrum recorded in photolysis of VK3/EG solution both indicate that3VK3*abstracts hydrogen atom from EG and neutral Vitamin K3radical VK3H*and EG alkyl radical Egl[-H]· are produced. Triplet mechanism is the main mechanism to generate CIDEP, with a little contribution from RPM. When TEMPO was added into the system, the emissive CIDEP spectrum of TEMPO was observed. The spin polarization transfers effectively from3VK3*to TEMPO. Here, the quenching rate constant for3VK3*by TEMPO is calculated as1.18×107L·mol-1·s-1based on the measurements of Stern-Volmer curve and the lifetime of3VK3(2) The quenching mechanism and dynamics of3VK3*by Vitamin C (VC) have been investigated in EG-H2O homogeneous and its TX-100(AOT、CTAB、SDS) micelle solutions. Micelles are used as a simulation of physiological environment of biological cell. During photolysis of VK3/VC/EG-H2O homogeneous solution,3VK3*abstracts hydrogen atom not only from EG, but also from VC. VC is an effective quencher of3VK3*and the quenching rate constant for3VK3*by VC is0.51×107L·mol-1The quenching reaction is nearly controlled by diffusion. In the anionic SDS(AOT) micelle systems, the coulomb repulsion between negative charges of the micelle surface and AsH-make the quenching rate for3VK3*by VC lower. In the cationic CTAB micelle systems, the coulomb attraction between negative charges of the micelle surface and AsH-make the quenching rate for3VK3*by VC higher. In TX-100micelle solution, because VK3and VC are solubilized inside the same area of the polyethylene glycol chain of TX-100micelle, the quenching rate for3VK3*by VC in TX-100micelle solution is much higher.