STM and STS Studies of the Structures and Energetics of Axial Ligand Coordination to Metal Porphyrins at the Liquid-Solid Interface

化学系的化学结构、动力学和机理计划支持华盛顿州立大学的Ursula Mazur教授研究液-固界面上金属卟啉(MPS)的轴向配体配位。将对MPS与轴向配位配体的反应进行系统的研究，并将使用扫描隧道显微镜(STM)绘制这些体系中的电子轨道结构和能量图。这些研究将测量配体结合引起的MP平面性偏差，识别和绘制MP络合物中的金属和配体轨道，比较MP系统的观察到的态密度以模拟电子计算，并在几分钟的时间尺度上测量MP配体缔合/解离的动力学。这项研究将有助于提供与平面和非平面金属卟啉在不同的金属3D轨道上的配位相关的结构和电子态变化的信息。关于卟啉构象柔性与轴向连接络合物结构/电子特性之间关系的研究通常适用于扭曲的金属四吡咯，因此涉及到许多生物和生物仿生的重要过程。金属卟啉具有多种功能，包括捕光、电子和能量转移、催化以及在分子识别中作为受体。其中许多功能依赖于某些物种(称为轴向配体)与MP相互作用。将轴向配体连接到MP上会导致卟啉和配体的电子结构发生变化。识别MP在连接/去连接过程中的结构和电子行为对于理解MPS的催化和识别功能至关重要。这个项目将不同的研究生和本科生在表面科学，表面显微镜和光谱学，以及配位化学的基本概念。这项拟议的研究将被用作一种教育工具，向代表不足的美国原住民和西班牙裔高中生进行推广工作。与校外科学和工程领导者的指导关系将提供培训、指导，并促进合作研究努力的形成。

The Chemical Structure, Dynamics and Mechanisms Program of the Chemistry Division supports Professor Ursula Mazur at the Washington State University for studies of axial ligand coordination to metal porphyrins (MPs) at the liquid-solid interface. Systematic studies will be performed on the reactions of MPs with an axially coordinated ligand and the electronic orbital structures and energies in these systems will be mapped using scanning tunneling microscopy (STM). These studies will measure deviations from planarity of the MP induced by ligand attachment, identify and map both the metal and the ligand orbitals in the MP complexes, compare the observed density of states for the MP systems to model electronic calculations, and measure kinetics in cases where MP ligand association/dissociation occurs on the time scale of minutes. This research will contribute information about the structure and electronic state changes associated with the ligation of planar and non-planar metal porphyrins with varying occupation of the metal 3d orbitals. Investigations of the connection between porphyrin conformational flexibility and the structural/electronic characteristics of an axially ligated complex are generally applicable to distorted metallo-tetrapyrroles and therefore, relevant to a variety of biologically and biomimetically important processes.Metalloporphyrins perform many versatile functions including light harvesting, electron and energy transfer, catalysis, and act as receptors in molecular recognition. Many of these functions depend on some species (called an axial ligand) interacting with the MP. The attachment of an axial ligand to the MP induces changes in the electronic structure of both the porphyrin and the ligand. Identifying the structural and electronic behavior of the MP during ligation/de-ligation processes is crucial for the understanding of the catalytic and recognition functions of MPs. This project will diverse graduate and undergraduate students in surface science, surface microscopy and spectroscopy, and the basic concepts of coordination chemistry. The proposed research will be used as an educational vehicle for an outreach effort to underrepresented Native American and Hispanic high school students. Mentoring relationships with off-campus science and engineering leaders will provide training, mentorship, and facilitate the formation of collaborative research efforts.