Photoelectron and Photoionization Spectroscopy of Metal-Organic Complexes

Intellectual Merit The proposed work will 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 photo ionization 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 lowfrequency 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. Broader Impacts The structural and thermochemical information obtained from this work will advance our fundamental knowledge of metal-ligand bonding important in organometallic or bioinorganic chemistry, chemical catalysis, and materials synthesis. Moreover, this work will promote the training of undergraduates, graduate students, and postdoctoral fellows. These students will learn a wide range of methods, techniques, and instrumentation of modern physical chemistry. The PI's research group consists of domestic and international students of both genders and has ongoing collaborations with international scientists and the faculty and students in Kentucky undergraduate institutions. This environment further enriches student experience for future employment. The PI is active in the development of undergraduate curricula and in the mentoring programs for local K-] 2 students.