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Electron and Ion Spectroscopy of Metal Hydrocarbon Complexes

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University of Kentucky UKnowledge Theses and Dissertations--Chemistry Chemistry 2014 ELECTRON AND ION SPECTROSCOPY OF METAL HYDROCARBON COMPLEXES Sudesh Kumari University of Kentucky, [email protected] Right click to open a feedback form in a new tab to let us know how this document benefits ou.y Recommended Citation Kumari, Sudesh, "ELECTRON AND ION SPECTROSCOPY OF METAL HYDROCARBON COMPLEXES" (2014). Theses and Dissertations--Chemistry. 30. https://uknowledge.uky.edu/chemistry_etds/30 This Doctoral Dissertation is brought to you for free and open access by the Chemistry at UKnowledge. It has been accepted for inclusion in Theses and Dissertations--Chemistry by an authorized administrator of UKnowledge. For more information, please contact [email protected]. STUDENT AGREEMENT: I represent that my thesis or dissertation and abstract are my original work. Proper attribution has been given to all outside sources. I understand that I am solely responsible for obtaining any needed copyright permissions. I have obtained and attached hereto needed written permission statements(s) from the owner(s) of each third-party copyrighted matter to be included in my work, allowing electronic distribution (if such use is not permitted by the fair use doctrine). I hereby grant to The University of Kentucky and its agents the non-exclusive license to archive and make accessible my work in whole or in part in all forms of media, now or hereafter known. I agree that the document mentioned above may be made available immediately for worldwide access unless a preapproved embargo applies. I retain all other ownership rights to the copyright of my work. I also retain the right to use in future works (such as articles or books) all or part of my work. I understand that I am free to register the copyright to my work. REVIEW, APPROVAL AND ACCEPTANCE The document mentioned above has been reviewed and accepted by the student’s advisor, on behalf of the advisory committee, and by the Director of Graduate Studies (DGS), on behalf of the program; we verify that this is the final, approved version of the student’s dissertation including all changes required by the advisory committee. The undersigned agree to abide by the statements above. Sudesh Kumari, Student Dr. Dong-Sheng Yang, Major Professor Dr. Dong-Sheng Yang, Director of Graduate Studies ELECTRON AND ION SPECTROSCOPY OF METAL HYDROCARBON COMPLEXES DISSERTATION A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College of Arts and Sciences at the University of Kentucky By Sudesh Kumari Lexington, Kentucky Director: Dr. Dong-Sheng Yang, Professor of Chemistry Lexington, Kentucky 2014 Copyright © Sudesh Kumari 2014 ELECTRON AND ION SPECTROSCOPY OF METAL HYDROCARBON COMPLEXES ABSTARCT OF DISSERTATION A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College of Arts and Sciences at the University of Kentucky By Sudesh Kumari Lexington, Kentucky Director: Dr. Dong-Sheng Yang, Professor of Chemistry Lexington, Kentucky 2014 Copyright © Sudesh Kumari 2014 - ABSTRACT OF DISSERTATION ELECTRON AND ION SPECTROSCOPY OF METAL HYDROCARBON COMPLEXES Metal-hydrocarbon complexes were prepared in a laser-vaporization molecular beam source and studied by single-photon zero electron kinetic energy (ZEKE) and mass- analyzed threshold ionization (MATI) spectroscopy. The ionization energies and vibrational frequencies of the metal complexes were measured from the ZEKE and MATI spectra. Metal-ligand bonding and low-lying electronic states of the neutral and ionized complexes were analyzed by combining the spectroscopic measurements with quantum chemical calculations and spectral simulations. In this dissertation, the metal complexes of mesitylene, aniline, cyclooctatetraene, benzene, ethene, and propene were studied. For each complex, different effects from metal coordination have been identified. Although metal-bis(mesitylene) sandwich complexes may adopt eclipsed and staggered conformations, the group VI metal- bis(mesitylene) complexes are determined to be in the eclipsed form. In this form, rotational conformers with the methyl group dihedral angles of 0 and 60° are identified for the Cr complex, whereas the 0° rotamer is observed for the Mo and W species. The unsuccessful observation of the 60° rotamer for the Mo and W complexes is the result of its complete conversion to the 0° rotamer in both He and He/Ar carriers. For group III metal aniline complexes, the ZEKE spectrum of each complex exhibits a strong origin band, a short M+-aniline stretching progression, and several low-frequency ligand based vibrational modes. The intensities of most of the transitions can be explained by the Franck-Condon (FC) principle within the harmonic approximation. However, the intensity of the low frequency out-of-plane ring deformation mode is greatly overestimated by the FC calculations and may be caused by the anharmonic nature of the mode. Although aniline offers two possible binding modes for the metal atoms, a п binding mode is identified with the metal atom over the phenyl ring. For Ce, Pr, and Nd(cyclooctatetraene) complexes multiple band systems are observed. This is assigned to the ionization of several low-lying electronic states of the neutral complex. This observation is different from the Gd(cyclooctatetraene) complex, for which a single band system is observed. The presence of the multiple low-energy electronic states is caused by the splitting of the partially filled lanthanide 4f orbitals in the ligand field. The ZEKE spectrum of the Gd(benzene) complex exhibits a strong origin band, whereas the spectrum of Lu(benzene) displays a weak one. The benzene ring is planar in the Gd complex, but bent in the Lu complex. Dehydrogenation and C-C coupling products are observed in the reaction of La atom and ethene/propene. For the La and ethene reaction, La(C2H2) and La(C4H6) complexes are identified. With propene, C-H bond activation leads to the formation of the La(C3H4) and H-La(C3H5) complexes, whereas the C-C coupling yields the La(trimethylenemethane) complex. In addition, the La(CHCCH3) and La(CHCHCH2) isomers of La(C3H4) are observed, which are produced by the 1,2- and 1,3-hydrogen elimination of propene. KEYWORDS: PFI-ZEKE Spectroscopy, MATI Spectroscopy, Metal-Hydrocarbon Complexes, Ionization Energy, Quantum Chemical Calculations Sudesh Kumari January 2, 2014 ELECTRON AND ION SPECTROSCOPY OF METAL HYDROCARBON COMPLEXES By Sudesh Kumari Dr. Dong-Sheng Yang Director of Dissertation Dr. Dong-Sheng Yang Director of Graduate Studies January 2, 2014 Dedicated to my mentors, family, and friends… ACKNOWLEDGEMENTS I am grateful to my mentor, advisory committee members, lab mates, departmental staff, family, and friends. I appreciate their assistance, time, effort, and patience that they have committed towards my scientific aspirations. I would like to thank my advisor, Dr. Dong-Sheng Yang, for his support and guidance during these years. His dedication and commitment to scientific research is very commendable and exciting. His friendly behavior and compassion created an enjoyable environment to work, study, and learn even in the difficult times. The way he deals with difficult problems have allowed me to achieve what otherwise I would not be able to. His enthusiasm and creativity will always be remembered and continue to inspire me in my future career. I would like to thank my advisory committee for their guidance and attention over the years. I am very grateful to Dr. John P. Selegue and Dr. Dennis J. Clouthier for their generous and much needed discussions about research projects. They taught me many fundamental aspects of inorganic and physical chemistry. The insight they provided over the past six years has served me to advance on my research. Dr. Chang-Guo Zhan provided helpful suggestions about the computations which were essential for my research. His scientific opinions were greatly appreciated and helpful. In addition, I cherish working with a diverse group of people who are very supportive and patient. I acknowledge my previous and current lab mates Dr. Yuxiu Lee, Dr. Sergiy Krasnokutskiy, Dr.Yang Liu, Dr. Mourad Roudjane, Dr. Ruchira Silva, Dr. iii Jung Sup Lee, Mr. Lu Wu, Ms. Dilrukshi Hewage, Mr. Wenjin Cao, Mr. Tao Jin for their helpful discussions and friendship. I am very thankful to Dr. Jung Sup Lee for his teaching me how to do the experiments. I especially want to acknowledge Dr. Shenggang Li who has helped me in computations, even after graduating and leaving UK in 2004. I am very thankful to Lu Wu for all his support over the years. His scientific skills and friendship will always be remembered and treasured. I would like to thank all those who helped to maintain the instrument in good condition: Mr. Art Sebesta (electronics), Mr. J. Babbitt (glassware), Jim Morris, Charles Tipton, Steven Maynard (machine shop). Without their prompt support, my work would not have so smoothly done. I am very thankful to the Department of Chemistry for the teaching assistantship, Graduate Research Award, and Centre for Advanced Material Fellowship. I am also very grateful for the funding of this research by the National Science Foundation and the Petroleum Research Fund. Last but not least, I am very grateful to my loving family. My parents, Darshana and Ram Kishan, and my brother Sandeep who have supported me in all rough times. Without their supervision, I could not be who I am today.
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