Photoelectron and Photoionization Spectroscopy of Metal-Organic Complexes

肯塔基大学的杨栋生是由实验物理化学项目资助，研究配位不饱和金属-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碱基的锂、铝、钪和铜的络合物、多环芳烃和多苯。在激光蒸发分子束中制备了这些配合物，用光电离质谱进行了鉴定，并用紫外光(UV)和红外(IR)-UV脉冲场电离-零电子动能(ZEKE)光电子和光电离光谱进行了研究。UV Zeke实验测量了精确的电离能和低频金属配体的伸缩和弯曲，而IR-UV Zeke实验和光致电离实验确定了这些体系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，它是金属原子的电离能和阳离子的键能相结合而得到的金属-配体中性键能。金属-配体的伸缩和弯曲直接证明了金属-配体的结合，而高频的配体振动则探测到了金属配位引起的配体几何构型的变化。结合光谱数据和理论预测确定电子态和分子结构。这一研究项目将使人们对金属原子与分子结合形成的络合物的结构和能量学有新的认识。这些结果将对有机金属化学、生物化学、催化和材料合成的从业者感兴趣。该项目为学生和博士后助理提供具有技术挑战性的研究培训机会，为他们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.