The Study On Photochemical Behavior Of The Quinones Photosensitizer In Ionic Liquids And Conventional Organic Solvents

Protein is not only a constituent of biological film, it plays important roles in organismsuch as catalytic role, transport role, regulating action,immune function, the protectiveeffect, but the protein is more easily affected by the environment impact, and easily becomethe main target of the photosensitizer damage attacking in the nature.Quinonesphotosensitizers widely exist in nature, DNA and proteins are the major target forphoto-damaged in biological systems. Photo-damaged of DNA and proteins have a crucialinfluence in ageing and the development of many diseases. Searching and investigating theQuinones photosensitizer play an increasingly important part in fast repair the photo-damagedDNA and proteins. ILs have many advantages over conventional organic solventsowing to their desirable properties, most of them have good miscibility with organicsolvents. This paper mainly studied photo-sensitive oxidation of quinones photosensitizer toaromatic amino acids and to photochemical behavior particularity in ionic liquids.（1）The transient photo-sensitive oxidation between2-Methylanthraquinone （MAQ） andaromatic amino acids （namely Tryptophan, Tyrosine and Phenylalanine） in acetonitrile/water（1:1, V/V） solution as investigated by laser photolysis techniques with the excitationwavelength of355nm. The triplet state absorption of2-Methylanthraquinone was attributedto390,450and590nm and the anion radical absorption of MAQ was due to390nm and490nm identified by the electron transfer reactions from4-Diazabicyclo [2.2.2] octane（DABCO） or Diphenylamine （DPA） to³MAQ*. With the decay of³MAQ*, the MAQ-at490nm appeared, which indicated the electron transfer reactions between³MAQ*and aminoacids occurred. Moreover, the rate constants were deduced to be3.0×10⁹，1.1×10⁹and1.8×10⁸L·mol^-1·s^-1for TrpH, TyrOH, PHE, respectively. On the other hand, the free energy changes（ΔG） of the reactions showed that the proposed electron transfer steps are thermodynamicallyfeasible.（2）The transient absorption spectrum of Anthraquinone-2-sulfonic acid （AQS） in H2Oand mixture of H2O and two kinds of tetrafluoroborate ionic liquids （[Bmim][BF₄]、[BuPy][BF₄]） and reaction kinetics of hydrated electron were investigated by nanosecondpulse radiolysis technique. The formation rate constants of anthraquinone-2-sulfonic acidanion radical at380nm in mixed solvent by H2O and [BuPy][BF₄] were deduced. The resultsshowed that with the increasing of ionic liquid concentrations,the formation rate constants ofanthraquinone-2-sulfonic acid anion radical decreased. Meanwhile, with comparison of thereaction of anthraquinone-2-sulfonate with hydrated electron and hydroxyl radical in different ionic liquids, the buildup can be observed in [BuPy][BF₄], while the formation cannot be observed in [Bmim][BF₄]. The results further disclosed that the physical andchemical properties of the ionic liquid are different from the common solvents. And thedifferent cations of ionic liquid may affect the reactivity.（3）The phohotochemical propenies of2-Methyl^-1,4-naphthoquinone in the system ofacetonitrile and ionic liquid [Bmim][PF₆]/acetonitrile binary mixed solutions wereinvestigated by nanosecond laser photolysis. The decay of the triplet excited state of2-Methyl^-1,4-naphthoquinone was faster in the presence of [Bmim][PF₆]. The rate constantsof photochemical reaction of2-Methyl^-1,4-naphthoquinone with N，N–Dimethylaniline werealso determined to be8.7×10⁹dm³mol^-1s^-1and1.0×10¹0dm³mol^-1s^-1in N2-saturatedacetonitrile and acetonitrile/[Bmim][PF₆]（9:1, v/v） solution，respectively.