水合及配位在双酮光还原六价铬中的作用机制研究

有机配体通过光化学调控重金属铬(Cr)的价态来影响Cr的毒性及迁移性，因而Cr-有机物复合体系中的光化学反应备受关注。双酮类化合物在自然界中广泛存在且具有水合特性，双酮的水合作用及配体效应在其光还原Cr(VI)过程中的规律鲜有研究。本项目拟选取配位能力强且光化学活性突出的乙酰丙酮及其不同官能团取代的衍生物(简称AAs)为研究对象，从构效关系角度入手，依据不同AAs的水合特点，解析双酮水合作用与转化Cr(VI)的关系。结合瞬态、稳态检测技术，探究AAs光还原Cr(VI)的基元反应规律及关键中间物种。在此基础上，通过理论计算定量分析AAs-Cr配合物的电子结构及激发态性质，并利用数理统计手段解析AAs光还原Cr(VI)的取代基效应及配体效应，揭示双酮高效光还原Cr(VI)的电子转移机制，为阐明双酮类物质作为有机配体对Cr价态转化的途径及其环境影响提供理论依据。

The photochemistry of organic ligands profoundly influences the toxicity and migration of chromium and has been extensively studied in recent years. Diketones are naturally abundant and could form the hydrated gem-diols. The effects of hydration and coordination of diketones on the photo-reduction of hexavalent chromium (Cr(VI)) are rarely studied. In this proposal, acetylacetone and its derivatives (AAs), with strong coordination ability and photo-activity, are selected as the representative organic ligands. The photochemical interactions between Cr(VI) and AAs will be systematically investigated from the perspective of structure-activity relationship. By comparing the hydration characteristics of AAs, the relationship between the hydration of diketones and the performance of the photo-reduction of Cr(VI) will be analyzed. Combined with transient and steady-state detection techniques, the speciation/structure of the intermediates will be identified. Then the molecular structure parameters and the properties of the excited states of AAs-Cr complexes will be simulated with the quantum chemical calculations and the ligand effect in the photo-reduction of Cr(VI) will be clarified. The findings will disclose the molecular mechanism of the photo-reduction of Cr(VI) by diketones and enhance the fundamental understanding on the photochemical behavior of the Cr-organic ligands complexes as well as the associated environmental impacts.