EXCITED STATED DYNAMICS OF TRANSITION METAL PORPHYRINS

金属卟啉是多种蛋白质中的活性中心。 它们具有重要的生物功能。这些例子包括 系统包括血红蛋白(配体结合和释放)。 细胞色素(电子传递)、光合作用反应中心 (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)。一个关键的长期问题是 卟啉及其化合物的分子结构是如何 蛋白质环境影响功能。两者之间的关键环节 一方面，化学成分和物理结构，以及 另一方面，反应动力学和函数是 金属卟啉的电子结构。人际关系 在物理结构、电子结构和瞬变之间 状态行为很难在活体内研究。我们的一个主要目标是 研究是通过时间来研究这些关系-- 金属卟啉激发态和金属卟啉的分辨吸收研究 体外暂态动力学研究。为此，飞秒和 较慢的时间尺度瞬变吸收研究在四个方面被提出。 主要领域：1)无辐射失活的机制 不发光的卟啉，2)光解离机理和 过渡金属卟啉配体的光缔合，3) 卟啉二聚体夹心络合物的光物理，4)激发态 卟啉阳离子和阴离子的态动力学。潜在的 每个领域的目标都包括阐明 电子和振动因素的重要贡献者 它们控制着能量、形成和衰变的速度， 环(Pe，PI*)激发态、金属环的反应通道 (d，PI*)和(PI，d)电荷转移(CT)激发态和金属 (d，d)激发态。光物理和光化学 我们将研究简单系统的行为，这些系统包括 选择的金属离子及其氧化态的变化，轴向 配体、大环、溶剂和温度。这个 拟议的研究不仅将增加我们对 金属卟啉在体内和体外的暂态动力学，但 还处理化学和其他领域中的重要问题 分子物理学，如激发态弛豫过程和 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.