X-Panding Halogen Bonding Interactions: Hybrid Cocrystals Composed of Ionic Halides, Iodine and Organoiodines
Total Page:16
File Type:pdf, Size:1020Kb
Clemson University TigerPrints All Dissertations Dissertations 5-2020 X-Panding Halogen Bonding Interactions: Hybrid Cocrystals Composed of Ionic Halides, Iodine and Organoiodines Khadijatul Kobra Clemson University Follow this and additional works at: https://tigerprints.clemson.edu/all_dissertations Part of the Chemistry Commons Recommended Citation Kobra, Khadijatul, "X-Panding Halogen Bonding Interactions: Hybrid Cocrystals Composed of Ionic Halides, Iodine and Organoiodines" (2020). All Dissertations. 2572. https://tigerprints.clemson.edu/all_dissertations/2572 This Dissertation is brought to you for free and open access by the Dissertations at TigerPrints. It has been accepted for inclusion in All Dissertations by an authorized administrator of TigerPrints. For more information, please contact [email protected]. X-PANDING HALOGEN BONDING INTERACTIONS: HYBRID COCRYSTALS COMPOSED OF IONIC HALIDES, IODINE AND ORGANOIODINES A Dissertation Presented to the Graduate School of Clemson University In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Chemistry by Khadijatul Kobra May 2020 Accepted by: William T. Pennington, Committee Chair Colin D. McMillen, Committee Co-chair Joseph S. Thrasher Stephen E. Creager Rakesh Sachdeva i ABSTRACT Halogen bonding referred to as an attractive, noncovalent interaction between an electrophilic region of a halogen atom X (acts as Lewis acid) and a nucleophilic region of a molecule Y (acts as Lewis base). Such interactions and the resulting polymeric networks play an important role in many fields related to crystal engineering, including for example, the fabrication of liquid crystals and novel drug design. The application of halogen bonding has particular promise in biological systems by increasing the lipophilicity of drugs to improve penetration through lipid membranes and tissues, enabling better intracellular delivery. Based on this concept, my research at Clemson University included the synthesis and characterization of many cocrystals derived from different alkyl/aryl ammonium/phosphonium iodides, an additional iodine source and neutral organohalogen compounds to establish versatile halogen bonding networks. Iodide salts such as PPh3MeI, NMe3PhI, (Me)4NI, (Et)4NI, 2- chloro-1- methylpyridinium iodide, 3-methylbenzothiazolium iodide, trimethylbenzylammonium iodide, tributylbenzylammonium iodide etc., an additional iodine source such as I2, iodoform etc., and several neutral organoiodines such as 1,2- or 1,4-diiodotetraflurobenzene, tetraiodoethylene, etc. have been used to synthesize salt-solvate cocrystals, where iodide or triiodide anions couple with the organic cation to form the salt component, and the neutral organiodine molecule can act as a “solvating” species. The anions and ii organoiodine molecules then form robust and varied halogen bonding networks, while the cations can also influence the structure based on their size, and their participation in complementary intermolecular interactions such as phenyl embraces, pi-pi interactions, and CH-pi interactions. For example, triphenylmethyl phosphonium iodide reacts with iodine and tetraiodoethylene to form triphenylmethylphosphonium triiodide cocrystal with tetraiodoethylene both by a simple mechanochemical synthesis (grinding the components together) and by solution chemistry (slow evaporation) in a variety of solvents. By varying the reaction stoichiometry, temperature, and solvent type, a robust crystal chemistry has been revealed. The resulting halogen bonding networks exhibit different chains, layers, or three-dimensional networks and broadened the scope and potential applications of halide crystal engineering. Additionally, several polyiodide salts have been synthesized by varying the reaction stoichiometry of iodide salts and the source of iodine used. The resulting polyiodide networks also exhibit different chains, layers, or three-dimensional networks based on the halogen bonding interactions formed. This study helps to understand the structural nature of higher polyiodides on a fundamental level and provides new insights into the classification of such polyiodides within the continuum of covalent and halogen bonding interactions. Moreover, some iodide cocrystals with organoiodine compounds have also been synthesized and their halogen bonding networks have been investigated and further compared with that in triiodide cocrystals having the same cation. This study helps to better iii understand the directional (or, non-directional) nature of the anions in establishing the halogen bonding motifs and provides an additional tool to apply to problems in crystal engineering. Finally, presence of other intermolecular noncovalent interactions such as phenyl embracing, pi-pi stacking, CH-pi interactions, F-pi interactions and hydrogen bonding have been studied for all the cocrystals. iv DEDICATION I would like to dedicate this work to my lovely family Md. Arifuzzaman (spouse), Shahela Begum (mother), and Manha Zunaira (daughter) for their continuous support and encouragement. Without their support, love and prayer it would not be possible for me to accomplish my degree. v ACKNOWLEDGMENTS I would like to express my heartfelt gratitude to my principal advisor Dr. William T. Pennington who gave me the opportunity to work on this wonderful project. His encouragements, supports and proper guidance throughout my graduate research helped me to achieve this accomplishment. I am expressing my thankfulness to my co-advisor Dr. Colin McMillen for his continuous support on getting numerous crystallographic data and discussions related to this research throughout the journey. I am also thankful to all my committee members, Dr. Joseph Thrasher, Dr. Stephen Creager, and Dr. Rakesh Sachdeva for their supportive contribution in my research and dissertation. Besides that, I would like to mention Dr. Julia Brumaghim who gave me mental support and valuable suggestions during the first year of study. I also would like to express thanks to Clemson University, especially the Chemistry Department, for providing me excellent technological support and several research facilities during my journey to accomplish the degree. Finally, I would like to thank all the undergraduates who worked on similar projects and supported me in developing a library of halogen-bonded cocrystals over the years. I would like to mention few names such as Shaun, Andrew, Brad, and Yuxuan for their wonderful contributions in my research. vi TABLE OF CONTENTS Page TITLE PAGE ...................................................................................................... i ABSTRACT ...................................................................................................... iii DEDICATION ................................................................................................... vi ACKNOWLEDGMENTS .................................................................................. vii LIST OF FIGURES ......................................................................................... xiv LIST OF SCHEMES ..................................................................................... xxvii LIST OF TABLES ........................................................................................ xxviii CHAPTER 1. INTRODUCTION .................................................................................1 1.1. Halogen bonding ...........................................................................1 1.2. History of halogen bonding............................................................3 1.3. Mechanism of halogen bond formation .........................................6 1.4. Geometry of halogen bond ............................................................7 1.5. Halogen bond donors and acceptors ............................................9 1.6. Triiodide as a halogen bond acceptor .........................................13 1.7. Ionic halides used in this study ....................................................17 1.8. Previous studies ..........................................................................19 1.9. Halogen bonding applications .....................................................20 vii Table of Contents (Continued) Page 1.10. Dissertation scope ....................................................................22 1.11. References ...............................................................................23 2. EXPERIMENTAL ...............................................................................37 2.1. Synthesis of cocrystals and salts ................................................37 2.1.1. Materials and chemicals used ...........................................37 2.1.2. General procedure of solutionsynthesis and crystal growth ....................................................................39 2.1.3. Mechanochemical synthesis ..............................................42 2.2. Characterization ..........................................................................43 2.2.1. Single crystal X-ray diffraction ...........................................43 2.2.2. Powder X-ray diffraction ....................................................44 2.2.3. Thermal analysis ...............................................................44 2.3. List of van der Waals radii for selected atoms .............................45 2.4. References ..................................................................................45 3. NEW POLYMORPHISM AND STRUCTURAL SENSITIVITY IN TRIPHENYLMETHYL-PHOSPHONIUM