ELECTRONIC SPECTROSCOPY OF SIMPLE PORPHYRINS

简单卟啉的电子光谱

• 批准号: 6452771
• 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
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-06-01 至 2002-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6452771
• 关键词: alkanes; bacteriorhodopsins; chemical synthesis; chlorin; chromophore; dipole moment; electronic spectra; laser spectrometry; metal complex; metalloporphyrins; photochemistry; porphyrin structure

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MBRS资助下正在进行的工作的延续和延伸。这主要是一个简单的，未取代的卟啉在固体状态在5 K相对于其电子基态和激发态蛋白质使用网站激发，光学烧孔和斯塔克效应的研究。这项研究的基本假设是，卟啉的激发态比目前公认的更复杂。卟啉已经被积极研究多年，但大多数光谱数据来自室温溶液，其产生宽带。我们的方法是将分子放置在正烷烃基质晶体或液氦温度下的低温玻璃中。高分辨率（约2cm/-1）光谱可以使用单点激发或光学烧孔来获得。当单点光谱或光学空穴的窄谱带与斯塔克效应耦合时，它们提供了分子电子状态的灵敏探针。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、异菌二氢卟酚）;它们是生物医学上重要部分（例如血红素、叶绿素）的母体化合物。现在特别感兴趣的简单卟啉的电子结构，是我们已经发现的第一和第二激发态之间的电子振动耦合和低能量π *- n跃迁的存在的证据。这两个观测结果将进一步研究斯塔克效应实验。然而，现在我们也将开始使用我们在获得高分辨率电子光谱方面的专业知识，以及我们先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状态。由于我们在异菌绿素方面的丰富经验，我们将从亚硫酸盐还原酶开始这项工作;这种酶的特点是存在铁siroheme（铁异菌绿素）交换偶联到Fe 4S 4簇。该项目的主要长期目标是提取详细的基态和激发态信息（例如振动能、偶极矩、π/π * 和npi* 原始能量、耦合等）。从生物医学上重要的卟啉发色团和了解他们的电子结构。