EXCITED STATE DYNAMICS OF TRANSITION METAL PORPHYRINS

这项资助的长期目标是阐明 四吡咯的结构、电子性质和动力学之间的关系。 这些关系对于卟啉的功能至关重要， 在许多生物系统中的相关分子，但很难 在体内探索。 然而， 四吡咯及其诊断光谱特征 可以通过时间系统地检查相关的瞬态- 简单四吡咯的分辨和稳态光谱研究 体外系统 该提案侧重于三个基本领域 对血红素蛋白和细菌的研究具有重要意义 光合反应中心 一、电子的组成 态和相关的光学性质和弛豫动力学 由两个四吡咯组成的超分子保持在货车范德华力中 接触将被探索。 强耦合的特殊性质 卟啉二聚体，例如反应的细菌叶绿素二聚体 中心将使用一系列对称和不对称的 卟啉夹心复合物， 大环之间。 二、过剩的表现形式 振动能和振动弛豫的速率和机制 在卟啉系统将解决通过超快和稳定 一系列四吡咯配合物的状态光学研究 冷凝和气相。 越来越清楚的是， 振动激发和动力学广泛影响时间分辨 血红素蛋白和反应中心的光谱测量， 对于后者也可能是功能上重要的。 最后，建议 研究将解决激发态光学性质和弛豫 四吡咯π阳离子和π阴离子自由基的动力学。 这是一 基本上未开发的领域，值得认真关注，考虑到 卟啉离子中间体是密切的功能， 许多四吡咯-蛋白质复合物。 这些重要问题将是 使用飞秒和更慢的瞬态吸收光谱解决 和稳态光学技术。 总的来说，这项工作将有助于 阐明了四吡咯的性质，这些性质支撑了它们的多样性， 生物功能。

the long-term objective of this grant is to elucidate the relationships between structure, electronic properties, and dynamics of tetrapyrroles. These relationships are crucial for the functioning of porphyrins and related molecules in numerous biological systems but are difficult to explore in vivo. However, the functionally-important properties of tetrapyrroles and the diagnostic spectroscopic characteristics of the associated transient states can be systematically examined through time- resolved and steady state spectroscopic studies of simple tetrapyrrole systems in vitro. This proposal focuses on three areas of fundamental importance to the study of the heme proteins and the bacterial photosynthetic reaction center. First, the composition of the electronic states and the associated optical properties and relaxation dynamics of supermolecules consisting of two tetra-pyrroles held in van der Waals contact will be explored. The special properties of strongly-coupled porphyrin dimers such as the bacteriochlorophyll dimer of the reaction center will be investigated using a series of symmetric and asymmetric porphyrin sandwich complexes that differ incrementally in the distance between the macrocycles. Second, the manifestations of excess vibrational energy and the rates and mechanisms of vibrational relaxation in porphyrinic systems will be addressed through ultrafast and steady state optical studies of a series of tetrapyrrole complexes in the condensed and gas phase. It is becoming increasingly clear that vibrational excitation and dynamics widely affect time-resolved spectroscopic measurements of heme proteins and the reaction center and also may be functionally important for the latter. Finally, the proposed research will address the excited state optical properties and relaxation dynamics of tetrapyrrole pi-cation and pi-anion radicals. This is an essentially unexplored area that warrants serious attention considering that porphyrin ionic intermediates are intimate to the function of numerous tetrapyrrole-protein complexes. These important issues will be addressed using femtosecond and slower transient absorption spectroscopy and steady state optical techniques. Collectively, the work will help elucidate the properties of tetrapyrroles that underpin their diverse biological functions.