EXCITED STATED DYNAMICS OF TRANSITION METAL PORPHYRINS

金属卟啉是许多蛋白质的活性中心 执行重要的生物功能。 这些的实例 系统包括血红蛋白（配体结合和释放）。 细胞色素（电子传递），光合反应中心 （电荷分离），过氧化氢酶，过氧化物酶和细胞色素P450 （氧化还原和催化化学）。 一个重要的长期问题是 卟啉的分子结构及其直接的 蛋白质环境影响功能。 之间的关键链接 化学成分和物理结构，一方面， 另一方面，反应动力学和功能是 金属卟啉的电子结构 的关系 物理结构，电子结构， 状态行为很难在体内研究。 我们的一个主要目标 研究是通过时间来调查这些关系- 金属卟啉激发态的分辨吸收研究 体外瞬态动力学。 为此，飞秒和 慢时间尺度瞬态吸收研究提出了四个 主要领域：1）无辐射失活机制， 非发光卟啉，2）光解机制， 来自过渡金属卟啉的配体的光缔合，3） 卟啉二聚体夹心复合物的电子物理学; 卟啉阳离子和阴离子的状态动力学。 底层 每个领域的目标包括阐明最重要的 电子和振动因素的重要贡献者 控制能量，形成和衰变的速率， 环（Pe，Pi*）激发态反应通道，金属环 （d，Pi*）和（Pi，d）电荷转移（CT）激发态，以及金属 （d，d）激发态。 光物理和光化学 行为将被调查的简单系统，包括良好的- 金属离子及其氧化态、轴向 配体、卟啉大环、溶剂和温度。 的 这些研究不仅能让我们更好地了解 在体内和体外金属卟啉瞬态动力学，但 还涉及化学其他领域的重要问题， 分子物理学，如激发态弛豫过程， 电子转移机制

Metalloporphyrins serve as the active sites in numerous proteins that carry out important biological functions. Examples of these systems include hemoglobin (ligand binding and release). cytochromes (electron transport), photosynthetic reaction centers (charge separation), and catalase, peroxidases, and cytochrome P450 (redox and catalytic chemistry). A crucial long-standing issue is how the molecular architecture of the porphyrin and its immediate protein environment influences function. The key link between chemical composition and physical structure, on the one hand, and reaction dynamics and function, on the other hand, is the electronic structure of the metalloporphyrin. The relationships between physical structure, electronic structure, and transient state behavior are difficult to study in vivo. A major goal of our research is to investigate these relationships through time- resolved absorption studies of metalloporphyrin excited state and transient state dynamics in vitro. To this end, femtosecond and slower time scale transient absorption studies are proposed in four major areas: 1) mechanisms of radiationless deactivation of nonluminescent porphyrins, 2) mechanisms of photodissociation and photoassociation of ligands from transition metal porphyrins, 3) photophysics of porphyrin dimer sandwich complexes, and 4) excited state dynamics of porphyrin cations and anions. The underlying objectives in each area include the elucidation of the most important contributors to the electronic and vibrational factors that control the energies, rates of formation and decay, and reaction channels of the ring (Pe, Pi*) excited states, metal ring (d, Pi*) and (Pi, d) charge transfer (CT) excited states, and metal (d,d) excited states. The photophysical and photochemical behavior will be investigated for simple systems encompassing well- chosen variations in the metal ion and its oxidation state, axial ligands, porphyrin macrocycle, solvent, and temperature. The proposed studies will not only increase our understanding of metalloporphyrin transient state dynamics in vivo and in vitro, but also address issues of importance in other areas of chemistry and molecular physics, such as excited state relaxation processes and electron transfer mechanisms.