NEGATIVE ION PHOTOELECTRON SPECTROSCOPY: ELECTRONIC STRUCTURES, CHEMICAL BONDING, MOLECULAR ACTIVATION, AND ELECTRON-MOLECULE INTERACTIONS by Gaoxiang Liu A dissertation submitted to Johns Hopkins University in conformity with the requirements for the degree of Doctor of Philosophy Baltimore, Maryland October 2019 © 2019 Gaoxiang Liu All rights reserved Abstract Negative ion photoelectron spectroscopy has been applied to address a broad range of fundamental problems in chemistry. Major topics that have been studied are related to electronic structures, chemical bonding, molecular activation, and electron-molecule interactions. New phenomena have been discovered, including but not limited to, the fine- tunability of the electronic spectra in superatoms, realization of Lewis basic sodium anion, halogen-bond stabilized anions, selective methane activation by single atomic anions, and excess electrons tethered by weak attractive interactions. The insight acquired from negative ion photoelectron spectroscopy has provided understanding into the above- mentioned topics at a molecular level. Dissertation readers: Prof. Kit H. Bowen (Committee Chair) Prof. Lan Cheng Prof. Joel R. Tolman ii Acknowledgement I would first like to thank my thesis advisor, Prof. Kit Bowen. Kit has been offering me his consistent support at a level that is beyond my imagination. He is always there when I am in need. He is willing to drop his urgent tasks to help me turn things around. I have also received invaluable guidance from Kit. This guidance is not only about science and academy, but also about the multifaceted reality of being the principal investigator of a lab. Such knowledge would make me more prepared if I were to establish my own lab. I want to thank my parents, who have been providing me their unconditional support for every decision I make. It is their selfless support that ensures me a decent life which exceeds most of my peers, helping me concentrate on my career without too much financial concern. I want to thank my colleagues whom I have the honor to work with. For those who have graduated from the group, I am grateful to Dr. Xinxing Zhang and Dr. Jacob Graham, who taught me a great deal on science and instrument when I was new to this group, and to Dr. Evan Collins, who was helpful under all kinds of situations. I feel blessed to work with a great team of researchers, Dr. Zachary Hicks, Sandy Ciborowski, Nic Blondo, Mary Marshall, Linjie Wang, Zhaoguo Zhu, Mike Denchy, Rachel Harris, Moritz Blankenhorn, Marica Dipalo, Lucas Hansen, and many visiting scholars. There is no way I can iii accomplish this much without the great teamwork. I am also very grateful to other professors and scientists whom we have collaborated with. I am thankful for Prof. Joel Tolman and Prof. Lan Cheng to be on my thesis committee. I would also like to thank Prof. Robert Compton, Prof. Shiv Khanna, and Prof. Vincent Ortiz for their support during my postdoc search. I want to thank my friends, who have helped keep me sane when I face up and down. Lastly, and most importantly, I want to thank my wife, Shuiqing Liu, who has been, and will always be, the greatest discovery of my life. You are all my reasons. iv Table of Contents ABSTRACT ................................................................................................................................................. II ACKNOWLEDGEMENT ......................................................................................................................... III LIST OF TABLES ................................................................................................................................... VIII LIST OF FIGURES ...................................................................................................................................... X I. INTRODUCTION............................................................................................................................... 1 II. ELECTRONIC STRUCTURES ........................................................................................................ 3 II.1 TUNING THE ELECTRONIC PROPERTIES OF HEXANUCLEAR COBALT SULFIDE SUPERATOMS VIA LIGAND SUBSTITUTION .............................................................................................................................. 4 II.2 LIGAND EFFECT ON THE ELECTRONIC STRUCTURE OF COBALT SULFIDE CLUSTERS: A COMBINED EXPERIMENTAL AND THEORETICAL STUDY .........................................................................25 III. CHEMICAL BONDING ...................................................................................................................47 III.1 PHOTOELECTRON SPECTROSCOPIC AND COMPUTATIONAL STUDY OF PYRIDINE-LIGATED GOLD CLUSTER ANIONS ......................................................................................................................................48 III.2 STABILIZING OTHERWISE UNSTABLE ANIONS WITH HALOGEN BONDING ....................................67 III.3 MYSTERY OF THREE BORIDES: DIFFERENTIAL METAL–BORON BONDING GOVERNING SUPERHARD STRUCTURES .........................................................................................................................79 III.4 SPECTROSCOPIC MEASUREMENT OF A HALOGEN BOND ENERGY ................................................94 – III.5 REALIZATION OF LEWIS BASIC SODIUM ANION IN THE NABH3 CLUSTER ................................108 v IV. MOLECULAR ACTIVATION .......................................................................................................124 − IV.1 CO2 ACTIVATION AND HYDROGENATION BY PTHN CLUSTER ANIONS ......................................125 IV.2 COMMUNICATION: WATER ACTIVATION AND SPLITTING BY SINGLE METAL-ATOM ANIONS .....139 IV.3 ACTIVATION OF HYDROXYLAMINE BY SINGLE GOLD ATOMIC ANIONS .....................................159 − IV.4 THE METALLO-FORMATE ANIONS, M(CO2) , M = NI, PD, PT, FORMED BY ELECTRON-INDUCED CO2 ACTIVATION .....................................................................................................................................171 IV.5 SELECTIVE ACTIVATION OF THE C−H BOND IN METHANE BY SINGLE PLATINUM ATOMIC ANIONS 188 V. ELECTRON-MOLECULE INTERACTIONS .............................................................................202 V.1 DIPOLE-BOUND ANIONS OF INTRAMOLECULAR COMPLEXES ....................................................203 V.2 DIPOLE-BOUND ANIONS: FORMED BY RYDBERG ELECTRON TRANSFER (RET) AND STUDIED BY VELOCITY MAP IMAGING–ANION PHOTOELECTRON SPECTROSCOPY (VMI–APES) ................................221 V.3 THE GROUND STATE, QUADRUPOLE-BOUND ANION OF SUCCINONITRILE REVISITED ...............235 V.4 THE CORRELATION-BOUND ANION OF P-CHLOROANILINE ........................................................249 V.5 OBSERVATION OF THE DIPOLE- AND QUADRUPOLE-BOUND ANIONS OF 1,4- DICYANOCYCLOHEXANE .........................................................................................................................259 VI. APPENDIX .......................................................................................................................................276 VI.1 HMOO AND H2MOO: MOLECULAR MIMICS FOR RHODIUM AND PLATINUM .............................276 VI.2 CO2 HYDROGENATION BY THE HYDRIDE OF PLATINUM MIMIC .................................................278 - VI.3 LIGATED LOW OXIDATION STATE ALUMINUM CLUSTER ANIONS ALNL (N = 1-14, L = N[SI(ME)3]2) vi 281 - VI.4 TWO NEW DOUBLE-RYDBERG ANIONS: LI(OH2)1,2 ....................................................................289 VI.5 ON THE EXISTENCE OF TRIPLE RYDBERG ANIONS ....................................................................312 VI.6 SUPERATOMIC CLUSTERS WITH FOUR DIFFUSE RYDBERG ELECTRONS .....................................315 VI.7 DIRECT MAPPING OF THE ELECTRONIC STRUCTURES OF HEXAVALENT URANIUM COMPLEX ....319 VI.8 CO2 HYDROGENATION TO FORMATE AND FORMIC ACID BY BIMETALLIC PALLADIUM-COPPER HYDRIDE CLUSTERS ................................................................................................................................322 VI.9 CO2 HYDROGENATION TO FORMATE BY PALLADIUM HYDRIDE CLUSTERS ...............................329 VI.10 TERTIARY SYSTEMS: TANDEM MOLECULAR ACTIVATION BY SINGLE ATOMIC ANIONS ............333 VI.11 DECOMPOSITION OF HYDROXYLAMINE BY IRIDIUM CLUSTER ANIONS .....................................345 VI.12 PHOTOELECTRON SPECTROSCOPIC STUDY OF DIPOLE-BOUND AND VALENCE-BOUND NITROMETHANE ANIONS FORMED BY RYDBERG ELECTRON TRANSFER .................................................348 VI.13 EXCESS ELECTRONS BOUND TO H2S TRIMER AND TETRAMER CLUSTERS .................................359 VI.14 SOLVATED ELECTRONS IN FORMIC ACID TRIMER AND TETRAMER ............................................380 VI.15 METHANE SOLVATED CYANIDE: THE TITAN CLUSTERS .............................................................381 VI.16 ELECTRON INDUCED PROTON TRANSFER ..................................................................................383 VI.17 XENON CLUSTER ANIONS .........................................................................................................389 VI.18 VMI IMAGING DATA ANALYSIS SOFTWARE UPDATE .................................................................395 VII. CURRICULUM VITAE .............................................................................................................402 vii List of Tables TABLE II.1.2 THEORETICAL AND EXPERIMENTAL ADIABATIC AND VERTICAL DETACHMENT ST ND − ENERGIES (1 AND