【作者】 夏鸣；

【导师】 刘建辉；

【作者基本信息】 大连理工大学 ， 应用化学， 2007， 硕士

【摘要】 光合作用是自然界中最基础的化学过程，光合生物中水的四电子氧化就是通过光系统Ⅱ（PSⅡ）中的释氧活性中心（OEC）来完成的。一系列关于PSⅡ的X-射线结构分析显示光合OEC蛋白的活性位点包括一个锰簇（Mn₄Ca）以及连接P₆₈₀和OEC的酪氨酸（Tyr_z）。由叶绿素α分子组成的P₆₈₀吸收光变为激发的P₆₈₀^*后，将一个电子先转移到脱镁叶绿素再转移到两个醌，而自身失电子变为一个P₆₈₀⁺。同时光氧化的P₆₈₀⁺从释氧中心（OEC）中得到一个电子（通过Tyr_z氧化Mn₄Ca簇）回到基态，经过四次光诱导电子转移，两分子水最终被氧化生成一分子氧气。Tyr_z对稳定最初的电荷分离至关重要。作为电子供体的锰簇在水氧化过程中经历了五个步骤六个状态（S₀-S₄）。虽然氧化水的机理到现在还不十分清楚，但人们普遍认为含高价锰金属的化合物存在于水氧化的过程中。如何得到高价稳定的锰金属仍是一个急待解决的课题。Corrole化合物是一种与卟啉类似的四吡咯芳香大环化合物，在稳定高价金属方面优于卟啉，它能将过渡态金属稳定到三价或者是更高价态。因此，本文设计了Corrole与酪氨酸通过酰胺键相连的配体4，及其锰金属络合物4b来模拟水氧化过程。本文从二吡咯甲烷化合物1出发，经过Corrole成环、硝基还原和DCC缩合反应得到Tyr-Corrole配体化合物4，分别与铜锰络合得到金属络合物4a、4b，并利用核磁、质谱、紫外可见光谱、元素分析、电化学等多种手段对大部分化合物的结构和性质进行了研究。为了便于比较铜Corrole化合物的性质，也合成并表征了中间体2、3的铜络合物2a、3a。通过质谱、紫外可见光谱等方面的研究，确定了锰络合物4b金属中心的价态为Mn（Ⅳ）。通过发射光谱研究发现自由的Corrole化合物具有明显的荧光，而金属铜、锰化合物由于金属核的淬灭无荧光。在二氯甲烷中的电化学循环伏安研究发现，铜Corrole化合物2a，3a在电化学氧化中无二聚现象出现，而4a在电化学驱动第一氧化过程中二聚为π-π二聚物，并实现二聚物的两个单环依次失去一个电子的分步氧化。虽然金属络合物4a、4b在电化学、化学和光化学条件下的催化水氧化研究均没有发现氧气产生，但所设计的目标化合物仍为人工模拟OEC提供了一个结构模型。更多还原

【Abstract】 The four-electron oxidation of water in photosynthetic organisms is achieved by anoxygen-evolving complex （OEC） in photosynthesis, which is one of the most fundamentalchemical processes in nature. A series of X-ray structure analysis of photosystemⅡ（PSⅡ）indicated that the active site in a photosynthetic OEC protein contains a Mn₄Ca cluster and aneighboring tyrosine （Tyr_z） is linked between P₆₈₀ and OEC. By light absorption of theprimary electron donor P₆₈₀ consisting of chlorophyllαmolecules, electron transfer occursfrom the excited P₆₈₀^* to a primary electron acceptor pheophytin and subsequently to twoquinines, forming P₆₈₀ radical cation. The photo-oxidized P₆₈₀ retrieves the electron from aMn₄Ca cluster via Tyr_z. After four photo-processes, two molecular water are oxidized to amolecular oxygen. Tyr_Z is crucial for stabilization of the primary charge separation. As toelectron donor, oxidation of water at the Mn₄Ca cluster occurs in five steps and involves sixoxidation states （S₀-S₄）. Though the mechanism of dioxygen evolution has not beendetermined completely, the stage of oxygen evolution would involve a high valent manganesespecies. How to obtain a stable ligand to stable high valent manganese is still a urgentproblem. Corroles are aromatic tetrapyrrole macrocycles as a ring-contracted analogue ofporphyrins, which have been proved to stabilize higher oxidation states for coordinated metalscompare to the more famous porphyrins. Therefore, the ligand 4 which contains a corrole anda tyrosine connected through an amide bond was designed, as well as its Mn complex 4b forthe study of water oxidation.The synthesis starts from a dipyrromethane compound 1 prepared according to theliterature. After three steps of corrole formation, reduction of the nitro group in 2 andformation of amido bond by DCC, the armed corrole compound 4 is synthesized. Asubsequent metal ions complexation gives corresponding complexes 4a and 4b. The coppercomplexes 2a and 3a of the intermediates 2 and 3 were also prepared for comparison. Most ofseven new complexes are characterized by ¹H NMR, MS, UV-vis, mass-spectrometry,elemental analysis. Through the measurements of MS, UV-vis, the valence state for thecentral metal ion of manganese complexes 4b is confirmed to be Mn（Ⅳ）. The emissionproperty indicates that the emission of ligands 2 and 3 is strong, but no emission is observedfor their metal complex due to the extermination of metal center. A remarkable dimerizationis found for 4a in contrast of no dimerization is observed for 2a and 3a in electrochemical oxidations in CH₂Cl₂. The first two oxidations of 4a occur via two stepwise abstractions ofone electron from each macrocycle in the electrogenerated corroleπ-πdimer. Though nooxygen was detected in the catalyzing water oxidation of metal complexes 4a and 4b byelectrochemical, chemical, photochemical processes, the target tyrosine modified metalcorrole complexes can be also seemed as a model in simulating the structure of OEC.更多还原