EXCITED STATE DYNAMICS OF TRANSITION METAL PORPHYRINS

这笔赠款的长期目标是阐明 四聚吡咯的结构、电子性质和动力学之间的关系。 这些关系对卟啉的功能和功能至关重要 许多生物系统中的相关分子，但很难 在活体内探索。然而，在功能上非常重要的属性 四聚吡咯及其诊断光谱特征 相关的暂态可以随着时间的推移被系统地检查- 简单四吡咯的分辨和稳态光谱研究 体外系统。这项建议侧重于三个基本领域 血红素蛋白与细菌研究的重要性 光合作用反应中心。第一，电子产品的组成 态及其相关的光学性质和驰豫动力学 范德华中含有两个四吡咯的超分子 我们将探讨联系方式。强耦合的特殊性质 卟啉二聚体如细菌叶绿素二聚体的反应 中心将使用一系列对称和不对称来研究 距离递增不同的卟啉夹心络合物 在大循环之间。第二，过度的表现 振动能与振动弛豫的速率和机制 在卟啉系统中将通过超快和稳定的方式解决 一系列四吡咯配合物的状态光学研究 凝聚和气相。越来越清楚的是， 振动激发和动力学对时间分辨有广泛的影响 血红素蛋白和反应中心的光谱测量 对后者来说也可能在功能上很重要。最后，提出了 研究将涉及激发态的光学性质和驰豫 四吡咯阳离子和阴离子自由基的动力学。这是一个 基本未开发的区域，值得认真考虑 卟啉离子中间体与酶的功能密切相关 大量的四吡咯-蛋白质复合体。这些重要问题将是 使用飞秒和较慢的瞬时吸收光谱进行寻址 和稳态光学技术。总的来说，这项工作将有所帮助 阐明支撑其多样性的四聚吡咯的性质 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.