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Structures and Reactivities of Ionized and Metal Cation-Containing Acetylene Clusters”

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Structures and Reactivities of Ionized and Metal Cation-Containing Acetylene Clusters” Virginia Commonwealth University VCU Scholars Compass Theses and Dissertations Graduate School 2007 Structures and Reactivities of Ionized and Metal Cation- Containing Acetylene Clusters Paul O. Momoh Virginia Commonwealth University Follow this and additional works at: https://scholarscompass.vcu.edu/etd Part of the Chemistry Commons © The Author Downloaded from https://scholarscompass.vcu.edu/etd/1000 This Dissertation is brought to you for free and open access by the Graduate School at VCU Scholars Compass. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of VCU Scholars Compass. For more information, please contact [email protected]. © Paul O. Momoh, 2007 All Rights Reserved STRUCTURES AND REACTIVITIES OF IONIZED AND METAL CATION- CONTAINING ACETYLENE CLUSTERS A Dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Virginia Commonwealth University. by PAUL O. MOMOH B.Sc., Fort Valley State University, Georgia, 2002 Director: M. SAMY EL-SHALL PROFESSOR, DEPARTMENT OF CHEMISTRY Virginia Commonwealth University Richmond, Virginia May 2007 ii Acknowledgements This dissertation is dedicated to Veronica Momoh, whose ideals and principles serve as the roadmap guiding my daily journey through life. Your patience, compassion, and selflessness, even at the peril of your own wellbeing cannot be appreciably articulated. Though you are gone, you will remain in my heart forever. I love you mom. Thanks to my wife, Rovianne C. Momoh, for her loving support and encouragement over the past five years and “high-fives” to Branden and Chelsea, my angels. I also want to recognize and thank Prof. M. Samy El-Shall for his scientific aptitude and academic guidance. To Drs. Michael Moet-Ner and Samuel A. Abrash, I will like to say a big thank you. Working with these brilliant yet humble men amplified the joy and raw gratification derived from the scientific process and collaborative work. Also, thanks to Dr. Yehia M. Ibrahim for his tremendous contribution to my understanding of the ion-mobility technique and finally, thanks to Dr. Edreese Alsharaeh who helped with my initial training at the lab. iii Table of Contents Page Acknowledgements............................................................................................................. ii Table of Contents...............................................................................................................iii List of Tables ..................................................................................................................... vi List of Figures..................................................................................................................viii CHAPTER 1 Introduction............................................................................................. 1 CHAPTER 2 Experimental Setup................................................................................. 6 2.1 Ion Generation .................................................................................................... 6 2.1.1 Laser Vaporization Ionization (LVI) .......................................................... 6 2.1.2 Electron Impact (EI) Ionization .................................................................. 8 2.2 Cluster Formation ............................................................................................... 8 2.3 QMS-IM-QMS.................................................................................................... 9 2.3.2 Ion Energy and Injection Energy .............................................................. 19 2.4 Reflectron Time-of-Flight Mass Spectrometer (RTOF-MS)............................ 23 2.5 Static Time-of-Flight Quadrupole Mass Spectrometer (STOF-QMS) ............. 30 CHAPTER 3 Experimental Techniques...................................................................... 37 3.1 Mobility Measurements .................................................................................... 37 3.2 Structure Determination.................................................................................... 41 3.3 Kinetic Measurements ...................................................................................... 46 3.4 Thermochemical Measurements (van’t Hoff Plots).......................................... 48 + CHAPTER 4 Structures of Small Acetylene Cluster Ions (C2H2)n , where n = 1-3... 52 4.1 Introduction....................................................................................................... 52 4.2 Experimental Section........................................................................................ 56 4.3 Theoretical Section ........................................................................................... 56 4.4 Results and Discussion ..................................................................................... 57 iv 4.4.2 Dissociation of the Acetylene Dimer and Trimer Ions ............................. 58 4.4.3 DFT Structures of Neutral Acetylene Dimer and Trimer Clusters........... 63 4.4.4 DFT Structures of the Acetylene Dimer and Trimer Cations................... 67 4.4.4.2 DFT Structures of the Acetylene Dimer Cation ................................... 67 4.4.4.3 DFT Structures of the Acetylene Trimer Cation................................... 69 4.4.5 Mobilities of the Acetylene Dimer and Trimer Cations ........................... 69 4.4.5.2 Mobility of the Acetylene Dimer Cation .............................................. 76 4.4.5.3 Mobility of the Acetylene Trimer Cation ............................................. 80 4.5 Infrared Determination of Cluster Ion Structures ............................................. 82 + CHAPTER 5 Reactivity of Small Acetylene Cluster Ions, (C2H2)1-3 , with Water.... 90 5.1 Introduction....................................................................................................... 90 + + +• 5.2 Ionic Reactions between C2H2 and H2O: The C2H3O and C2H4O Ions ...... 91 5.2.1 Experimental and Computational Method................................................ 91 5.2.2 Results and Discussion ............................................................................. 94 + 5.2.2.1 The C2H2˙ / H2O Reaction System and Proposed Mechanism............. 94 +• 5.2.2.2 Thermochemistry and Structure of the C2H4O Adduct Ion ............. 104 + 5.2.2.3 Formation and Deprotonation of the C2H3O Product Ion ................. 105 5.2.2.4 Interstellar Reaction of the Acetylene-Water System......................... 107 5.2.2.5 Theoretical Calculations ..................................................................... 107 +• C2H4O ........................................................................................................... 109 + C2H3O ............................................................................................................ 110 5.2.2.6 Comparison with Experimental Thermochemistry............................. 112 + 5.2.2.7 Predicted Geometries for the C2HnO ·H2O Complexes (n = 3 and 4).117 +• C2H4O ·H2O................................................................................................... 117 + C2H3O ·H2O.................................................................................................... 121 Conclusion .............................................................................................................. 123 5.3 Stepwise Hydration of Ionized Acetylene Dimer and Trimer Cations........... 128 Experimental and Theoretical section..................................................................... 128 5.4 Results and Discussion ................................................................................... 129 5.4.1 Dimer Ion Hydration............................................................................... 129 5.4.1.1 Binding Energies and Thermochemistry of the Dimer Ion................. 130 ·+ ·+ 5.4.1.2 Calculated C4H4 ·(H2O)1-2 Structures for Select C4H4 Isomers....... 131 ·+ C4H4 ·H2O:..................................................................................................... 131 ·+ C4H4 ·(H2O)2:................................................................................................. 133 5.4.2 Trimer Ion Hydration. Further Evidence for the Formation of Benzene Radical Cation......................................................................................................... 135 5.4.3 Conclusions............................................................................................. 145 v Chapter 6 Interaction of the Fe+, Co+, and Ni+ Cations with Acetylene Clusters ....... 153 6.1 Introduction..................................................................................................... 153 6.2 Experimental and Theoretical Methodology. ................................................. 154 6.3 Results and Discussion ................................................................................... 155 + + + 6.3.2 DFT Predicted Structures and Energies of Fe , Co , and Ni (C2H2)n clusters 161 + + + Fe C2H2, Co C2H2, and Ni C2H2 ........................................................................ 161 + + + Fe (C2H2)2, Co (C2H2)2, and Ni (C2H2)2 ............................................................ 167 + + + Fe (C2H2)3, Co (C2H2)3, and Ni (C2H2)3 ............................................................ 176 + 6.3.3 Investigation of Suspect Co -mediated C2H2 Cyclotrimerization Reaction 181 6.3.4 Conclusion .............................................................................................
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