ELECTRONIC SPECTROSCOPY OF SIMPLE PORPHYRINS

简单卟啉的电子光谱

基本信息

批准号：
6318351
负责人：
LAWRENCE William JOHNSON
金额：
$ 3.15万
依托单位：
YORK COLLEGE
依托单位国家：
美国
项目类别：
财政年份：
2000
资助国家：
美国
起止时间：
2000-06-01 至 2001-05-31
项目状态：
已结题

项目摘要

The research described here is a continuation and extension of work being carried out under our current MBRS grant. This is primarily a study of simple, unsubstituted porphyrins in the solid state at 5K with respect to their electronic ground and excited state proteins using site excitation, optical hole-burning and the Stark effect. The fundamental hypothesis of this research is that excited states of porphyrins are more complex than is currently recognized. Porphyrins have been actively studied for years, but most of the spectroscopic data is from room temperature solutions which yield broad bands. Our approach is to place the molecules in n-alkane host crystals or low temperature glasses at liquid helium temperatures. High resolution (approximately 2 cm/-1) spectra can be obtained using single sit excitation or optical hole-burning. When the narrow bands of single site spectra, or optical holes are coupled with the Stark effect, they provide a sensitive probe of molecule's electronic states. We plan to continue to study free base and metal complex forms of these simple molecules (e.g. porphin, chlorin, isobacteriochlorin); they are parent compounds of biomedically important moieties (e.g. hemes, chlorophylls). Of particular interest now in the electronic structure of the simple porphyrins, is that we have found evidence for vibronic coupling between the first and second excited states and for the presence of low energy pi*- n transitions. Both of these observations will be studied further with Stark effect experiments. However, now we will also begin to use our expertise in obtaining high resolution electronic spectra, and the detailed spectral information which we previously obtained on simple prophyrins, to examine the electronic states of biomedically active porphyrin based moieties. Because of our extensive experience with isobacteriochlorin we will start this initiative with sulfite reductase; this enzyme is characterized by the presence of an iron siroheme (iron isobacteriochlorin) exchanged coupled to a Fe4S4 cluster. The primary, long-term objective of this project is to extract detailed ground and excited state information (e.g. vibrational energies, dipole moments, pi/pi* and npi* origin energies, coupling, etc.) from biomedically important porphyrin chromophores and understand their electronic structure.

这里描述的研究是我们目前的 MBRS 资助下正在进行的工作的延续和延伸。这主要是利用位点激发、光学烧孔和斯塔克效应对 5K 下固态的简单、未取代的卟啉及其电子基态和激发态蛋白质进行的研究。这项研究的基本假设是卟啉的激发态比目前认识的更复杂。卟啉已被积极研究多年，但大多数光谱数据来自产生宽带的室温溶液。我们的方法是将分子置于液氦温度下的正烷烃主体晶体或低温玻璃中。使用单点激发或光学烧孔可以获得高分辨率（约 2 cm/-1）光谱。当单点光谱的窄带或光孔与斯塔克效应耦合时，它们提供了分子电子态的灵敏探针。我们计划继续研究这些简单分子的游离碱和金属络合物形式（例如卟啉、二氢卟酚、异细菌二氢卟酚）；它们是生物医学重要部分（例如血红素、叶绿素）的母体化合物。现在对简单卟啉的电子结构特别感兴趣的是，我们发现了第一和第二激发态之间电子振动耦合以及低能 pi*- n 跃迁存在的证据。这两个观察结果将通过斯塔克效应实验进一步研究。然而，现在我们还将开始利用我们在获得高分辨率电子光谱方面的专业知识，以及我们之前在简单卟啉上获得的详细光谱信息，来检查生物医学活性卟啉基部分的电子态。由于我们在异菌绿素方面拥有丰富的经验，我们将从亚硫酸盐还原酶开始这一举措；该酶的特征是存在与 Fe4S4 簇交换耦合的铁西罗血红素（铁异菌二氢卟酚）。该项目的主要长期目标是从生物医学上重要的卟啉发色团中提取详细的基态和激发态信息（例如振动能量、偶极矩、pi/pi* 和 npi* 原能、耦合等）并了解它们电子结构。