X RAY AND CHEMICAL STUDIES OF METALLOPORHYRINS

介绍了多种新型金属卟啉化合物的合成与表征。这项工作将强调，但不限于，铁卟啉衍生物。大多数拟研究的化合物类别都与对血红蛋白衍生物的理解有关，这些衍生物具有广泛的生物学功能，包括氧利用和运输、一氧化氮信号传导、电子传递、药物代谢和各种其他酶促过程。另一类衍生物与光合作用中重要的物种有关。三维x射线晶体结构测定方法将应用于确定金属卟啉立体化学的分子结构和各个细节方面。其他适当应用的方法包括通过体温度相关磁化率和电子顺磁共振（EPR）测量来表征磁性。M斯堡尔光谱，振动和紫外-可见-近红外光谱，电化学性质，和分子力学计算。从最广泛的角度来看，研究目标是实现金属卟啉的结构和物理性质的合成，特别是因为这些关系与理解基于血红蛋白的生物过程有关。在某种程度上，这将通过建立金属卟啉基团在其生物环境中的可能的立体化学特征和模拟选定的血红蛋白的特定假基行为来完成。这些研究有望提供蛋白质结构如何调节金属卟啉几何结构的理解，以及如何利用相同的基本铁原卟啉IX单元进行各种生物过程。拟研究的卟啉酸铁包括组氨酸连接细胞色素b和c的合成类似物，以研究轴向配体取向等特征如何影响它们的电子结构和氧化还原性能。另一个重要的研究目标是探索金属卟啉中的电子相互作用；详细的研究将检查耦合系统与潜在的内部和/或分子间途径。这类研究包括具有氧化或还原卟啉核的物种，其中π自由基自旋耦合是重要的。

The synthesis and characterization of a variety of new metalloporphyrin compounds is proposed. The work will emphasize, but will not be limited to, iron porphyrinate derivatives. Most classes of compounds proposed for study are related to developing an understanding of hemoprotein derivatives, which carry out a wide range of biological functions including oxygen utilization and transport, NO-based signaling, electron transport, drug metabolism and a variety of other enzymatic processes. Another class of derivatives is related to species important to photosynthetic reactions. The methods of three-dimensional X-ray crystal structure determination will be applied to define molecular structures and various detailed aspects of metalloporphyrin stereochemistry. Other methodologies to be applied, as appropriate, include characterization of magnetic properties by bulk temperature-dependent susceptibility and electron paramagnetic resonance (EPR) measurements. Mssbauer spectroscopy, vibrational and UV-vis-near-IR spectroscopy, electrochemical properties, and molecular mechanics calculations. The research objectives, stated in the broadest terms, are to achieve a synthesis of the structural and physical properties of metalloporphyrins, particularly as these relationships pertain to an understanding of hemoprotein-based biological processes. In part, this will be accomplished by establishing possible stereochemical features of a metalloporphyrin group in its biological environment and to model specific prosthetic group behavior of selected hemoproteins. Such studies are expected to provide understanding of how protein structures could modulate metalloporphyrin geometry and how a wide variety of biological processes can be carried out with the same fundamental iron protoporphyrin IX unit. Iron porphyrinates to be studied include synthetic analogues of bis(histidine)-ligated cytochromes b and c to examine how features such as axial ligand orientation affect their electronic structure and oxidation-reduction properties. Another significant research objective is the exploration of electronic interactions in metalloporphyrins; detailed studies will examine coupling in systems with potential intra- and/or intermolecular pathways. Included in such studies are species with oxidized or reduced porphyrin cores in which pi-radical spin coupling is significant.