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Matrix-Isolation and Computational Studies of Transient Polyhalogenated Intermediates and Weakly-Bound Complexes

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Matrix-Isolation and Computational Studies of Transient Polyhalogenated Intermediates and Weakly-Bound Complexes Marquette University e-Publications@Marquette Dissertations (2009 -) Dissertations, Theses, and Professional Projects MATRIX-ISOLATION AND COMPUTATIONAL STUDIES OF TRANSIENT POLYHALOGENATED INTERMEDIATES AND WEAKLY-BOUND COMPLEXES. AIMABLE KALUME Marquette University Recommended Citation KALUME, AIMABLE, "MATRIX-ISOLATION AND COMPUTATIONAL STUDIES OF TRANSIENT POLYHALOGENATED INTERMEDIATES AND WEAKLY-BOUND COMPLEXES." (2013). Dissertations (2009 -). Paper 274. http://epublications.marquette.edu/dissertations_mu/274 MATRIX-ISOLATION AND COMPUTATIONAL STUDIES OF TRANSIENT POLYHALOGENATED INTERMEDIATES AND WEAKLY-BOUND COMPLEXES. by Aimable KALUME A Dissertation submitted to the Faculty of the Graduate School, Marquette University, in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy. Milwaukee, Wisconsin May 2013 ABSTRACT MATRIX-ISOLATION AND COMPUTATIONAL STUDIES OF TRANSIENT POLYHALOGENATED INTERMEDIATES AND WEAKLY-BOUND COMPLEXES. Aimable KALUME Marquette University, 2013 As time goes by and new innovations are brought up to improve living conditions, the human impact on the environment becomes more significant. It has been shown that man-made halogenated compounds play a key role in many real-world chemical processes. For example, in combustion, these compounds are used as fire retardant agents, and in atmospheric chemistry, they initiate ozone depletion reactions.[1-4] However little is known about the mechanisms governing these processes and many intermediates involved in these processes have been elusive to researchers for diverse reasons such as short lifetime and difficulty in distinguishing products from parents molecules. The studies compiled in this work are focused on exploring the photochemical behavior of various intermediates derived from polyhalogenated compounds. These intermediates are trapped in inert rigid matrix and characterized by using IR, UV/Vis spectroscopy supported by computational methods. The photochemistry is explored using selected wavelength appropriate to each species. In this work, the photolysis products of CF2I2, CF2Br2, CXBr3 (X=H, D, F), C2H4Br2, C2F4Br2 have been generated and trapped in Argon or Neon matrices and most of them were characterized for the first time. We have also studied weakly bound complexes (C2H4···Br2, C2H4···I2), formed in matrix by co-deposition of monomers or by trapping fragments resulting from high voltage discharge (H2CXBr···Br; X=H, Cl, Br). We hope that our results will contribute to better understand the photochemical behavior of polyhalogenated species, and to some extent help to understand mechanism in different phenomena involving these species. iii ACKNOWLEDGMENTS Aimable KALUME Marquette University, 2013 I am and will always be grateful to the Almighty God, for having led me on this path, protected and surrounded me with wonderful people. I couldn’t ask more. It is my honor to express my deepest gratitude to my advisor and committee chair, Professor Scott A. Reid, who has the attitude and substance of a genius. You gave me the unique opportunity to join your lab, introduced me to molecular spectroscopy and guided me through this challenging project. But most of all you set me a role model in every sense of the word: whether scientific analysis, practical and technical skills. I extend my sincere gratitude, to my committee members, Dr. Rajendra Rathore and Dr. Qadir Timerghazin; I am really thankful for your time in reading, correcting and guiding my work. My appreciation also goes to Professor Yuan-Pern Lee at the National Chiao Tung University in Taiwan: inviting and hosting me in your lab was such a great and enriching technical experience. I share the credit of my work with people that I had the chance to work with. Special thanks to Dr. Lisa George for guiding my first steps in Matrix-solation field, and providing your experience and skills. Special thanks to my colleague students, Lloyd Muzangwa, Silver Nyambo, Brandon Uhler, for providing the exciting, pleasant and funniest workplace. iv My great pleasure to acknowledge the most important people in my life: my family and friends. It was your omnipresent support and encouragements that kept me moving in the right direction. Thanks for believing in me and understanding when I was physically and/or mentally absent. I am sincerely indebted to Marquette University, for the scholarship, financial support and Fellowship awards (ACS, Bournique and Eisch fellowships). Finally, I don’t have words to thank my best friend and sister, Solange, for this lifetime opportunity of being where I stand today. v DEDICATION To the loving memory of my Mother, Salomé M. To my Father, Henri T. For their immeasurable sacrifices and courage I, humbly, dedicate this work. vi PUBLICATIONS 1. Lisa George, Aimable Kalume and Scott A. Reid, Pulsed Jet Discharge and + Computational Study of CX2Br (X=H, F), Chemical Physics Letters (2010) 484 214- 218 2. Patrick Z. El-Khoury, Lisa George, Aimable Kalume ,Scott A. Reid, Bruce S. Ault, Alexander Tarnovsky, Characterization of iso-CF2I2 in frequency and ultrafast time domains, The Journal of Chemical Physics, (2010) 132, 124501 3. Patrick Z. El-Khoury, Lisa George, Aimable Kalume, Igor Schapiro, Massimo Olivucci Alexander N. Tarnovsky, Scott A. Reid, Matrix Isolation and Computational Study of CF2I radical, Chemical Physics Letters, (2010) 496, 68-73 4. Lisa George, Aimable Kalume, Patrick El-Khoury, Alexander Tarnovsky and Scott A. Reid, Matrix isolation and computational study of isodifluorodibromomethane, F2CBr–Br…: A route to Br2 formation in CF2Br2 photolysis, The Journal of Chemical Physics, (2010) 132, 084503 5. Lisa George, Aimable Kalume, Brian Esselman, James Wagner and Scott A. Reid, Spectroscopic and Computational Studies of matrix isolated iso-CHBr3: Structures, properties and photochemistry of iso-bromoform, The Journal of Chemical Physics, (2011) 135, 124503 6. Thomas J. Preston, Maitreya Dutta, Brian Esselman, Aimable Kalume, Lisa George, Robert J. McMahon, Scott A. Reid and Fleming Crim, Formation and relaxation dynamics of iso-CH2Cl-I in cryogenic matrices, The Journal of Chemical Physics, (2011) 135, 114503 7. Aimable Kalume, Lisa George and Scott A. Reid, Isomerization as a key path to molecular products in the gas-phase decomposition of halons, The Journal of Physical Chemistry Letters, (2010) 1 ,3090-3095 8. Aimable Kalume, Lisa George, Patrick El-Khoury, Alexander N. Tarnovsky and Scott A. Reid, Spectroscopic and Computational Studies of the Laser Photolysis of Matrix Isolated 1,2-Dibromoethanes: Formation and Fate of the Bromoethyl radicals, The Journal of Physical Chemistry A., (2010) 114, 9919-9926 9. Lisa George, Laura Wittmann, Aimable Kalume, and Scott A. Reid, Photoinduced Electron Transfer in a Prototypical Mulliken Donor-Acceptor Complex: C2H4···Br2, Journal of Physical Chemistry Letters, (2010), 1, 2618-2621 10. Lisa George, Aimable Kalume, Brian Esselman, Robert J. McMahon and Scott A. Reid, Pulsed-Jet Discharge and Computational Study of Bromine Atom Complexes: vii Br•••BrCH2X (X=H, Cl, Br), The Journal of Physical Chemistry A., (2011) 115, 9820- 9827. 11. L. George, A. Kalume, B. Esselman, J. Wagner, R. J. McMahon, and S. A. Reid, “Spectroscopic and computational studies of matrix-isolated iso-CHBr3: Structure, properties, and photochemistry of iso-bromoform”, J. Chem. Phys., 2011, Vol. 135, 124503/1-124503/8. 12. Lisa George, Aimable Kalume, Scott A. Reid, Brian Esselman, Robert J. McMahon, Spectroscopic and Computational Studies of Matrix-Isolated of iso-CXBr3 (X = F, Cl, Br): Structure, properties, and photochemistry of substituted iso-tribromomethanes, The Journal of Molecular structure, (2012), 1025, 61-68. 13. Aimable Kalume, Lisa George, Scott A. Reid, On the Electronic Spectroscopy of the iso-polyhalomethanes, Chemical Physics Letters, (2012), 551, 64-67. 14. Lisa George, Aimable Kalume, Scott A. Reid, Probing Radical Pathways in Electrophilic Addition of Halogens: Classical vs. Bridged Intermediates, Chemical Physics Letters (2012), 554, 86-89. 15. Aimable Kalume, Lisa George, Nicole Cunningham, Scott A. Reid, A New View of proton-Coupled Electron Transfer: Concerted vs. Sequential Pathways in Hydrogen Halide Elimination, Chemical Physics Letters (2013), 556, 35-38 viii LIST OF CONTENTS ABSTRACT ....................................................................................................................... ii ACKNOWLEDGMENTS ................................................................................................ iii DEDICATION ................................................................................................................... v PUBLICATIONS .............................................................................................................. vi LIST OF CONTENTS .................................................................................................... viii LIST OF TABLES ........................................................................................................... xii LIST OF FIGURES ........................................................................................................ xiv LIST OF SYMBOLS AND ACRONYMS ..................................................................... xxi Chapter 1. INTRODUCTION ............................................................................................ 1 Chapter 2. EXPERIMENTAL AND COMPUTATIONAL METHODS .......................... 7 2.1 Experimental methods ..............................................................................................
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