Photoelectron and Photoionization Spectroscopy of Metal-Organic Complexes

肯塔基州大学的杨东升受实验物理化学计划的支持，研究配位不饱和气态金属有机络合物的电子光谱、金属-配体结合、电子态和分子结构。金属有机体系包括DNA和RNA核碱基的锂、铝、钪和铜络合物、多环芳烃和聚苯。这些配合物的制备在激光蒸发分子束，鉴定与光电离质谱，并研究了使用紫外（UV）和红外（IR）-紫外脉冲场电离-零电子动能（ZEKE）光电子和光电离光谱。UV ZEKE实验测量精确的电离能和低频金属配体拉伸和弯曲，而IR-UV ZEKE和光电离实验确定这些系统的高频配体振动模式。电离能是分子的关键热化学性质之一，用于通过结合金属原子的电离能和阳离子的键能来获得金属-配体中性键能。金属-配体的拉伸和弯曲给出了关于金属-配体结合的直接证据，而高频配体振动探测由金属配位引起的配体几何形状的变化。结合光谱数据和理论预测确定电子状态和分子结构。 该研究项目将导致有关金属原子与分子结合组成的络合物的结构和能量学的新知识。 结果将感兴趣的从业者在有机金属化学，生物化学，催化和材料合成。该项目为学生和博士后提供了技术上具有挑战性的研究培训机会，使他们为未来的就业做好有效的准备。

Dong-Sheng Yang of the University of Kentucky is supported by the Experimental Physical Chemistry Program to investigate the electronic spectra, metal-ligand binding, electronic states, and molecular structures of coordinatively unsaturated gaseous metal-organic complexes. The metal-organic systems include lithium, aluminum, scandium, and copper complexes of DNA and RNA nucleobases, polycyclic aromatic hydrocarbons, and polyphenyls. These complexes are prepared in laser-vaporization molecular beams, identified with photoionization mass spectrometry, and studied using ultraviolet (UV) and infrared (IR)-UV pulsed field ionization-zero electron kinetic energy (ZEKE) photoelectron and photoionization spectroscopy. The UV ZEKE experiments measure precise ionization energies and low frequency metal-ligand stretches and bends, whereas the IR-UV ZEKE and photoionization experiments determine the high-frequency ligand vibrational modes of these systems. The ionization energy is one of the key thermochemical properties of a molecule and is used to obtain the metal-ligand neutral bond energy by combining the ionization energy of the metal atom and the bond energy of the cation. The metal-ligand stretches and bends give direct evidence about the metal-ligand binding, whereas the high-frequency ligand vibrations probe changes in the ligand geometry induced by metal coordination. Combining the spectroscopic data and theoretical predictions determines electronic states and molecular structures. This research project will lead to new knowledge about the structure and energetics of complexes made up of metal atoms binding to molecules. The results will be of interest to practitioners in organometallic chemistry, biochemistry, catalysis, and materials synthesis. This project provides technologically challenging research training opportunities for students and postdoctoral associates to prepare them effectively for future employment.