Automated Template C: Created by James Nail 2013V2.1 Design, synthesis, and testing of bis-corannulene receptors for fullerenes based on Klärner’s tethers By Peumie Luckshika Abeyratne Kuragama A Dissertation Submitted to the Faculty of Mississippi State University in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Chemistry in the Department of Chemistry Mississippi State, Mississippi December 2015 Copyright by Peumie Luckshika Abeyratne Kuragama 2015 Design, synthesis, and testing of bis-corannulene receptors for fullerenes based on Klärner’s tethers By Peumie Luckshika Abeyratne Kuragama Approved: ____________________________________ Andrzej Sygula (Major Professor) ____________________________________ Keith T. Mead (Committee Member) ____________________________________ Todd E. Mlsna (Committee Member) ____________________________________ Dongmao Zhang (Committee Member) ____________________________________ Stephen C. Foster (Graduate Coordinator/Committee Member) ____________________________________ R. Gregory Dunaway Dean College of Arts & Sciences Name: Peumie Luckshika Abeyratne Kuragama Date of Degree: December 11, 2015 Institution: Mississippi State University Major Field: Chemistry Major Professor: Andrzej Sygula Title of Study: Design, synthesis, and testing of bis-corannulene receptors for fullerenes based on Klärner’s tethers Pages in Study: 141 Candidate for Degree of Doctor of Philosophy The discovery of the new allotropic forms of elemental carbon (e.g. fullerenes and carbon nanotubes) introduced a novel motif in supramolecular chemistry based on dispersion interactions of curved networks of sp2 hybridized carbon atoms. Buckybowls, the curve-shaped polycyclic aromatic hydrocarbons, appear to be ideal candidates for molecular receptors to recognize fullerenes. Corannulene, the smallest and the best studied buckybowl, has been recognized as one of the important pincers in developing molecular receptors for fullerenes. The main goal of our research is to synthesize corannulene-based molecular receptors for fullerenes with high binding affinities with the use of the pincers preorganized on tailor made tethers of proper topology. This dissertation describes the design, synthesis, and testing of two bis- corannulene receptors with Klärner’s tethers. First, molecular mechanics (MM) was employed for the assessment of the binding potential of the receptors with fullerenes. Next, the receptors were synthesized by Diels-Alder cycloaddition reactions with isocorannulenofuran and Klärner’s dienophiles followed by dehydration. Finally, 1H NMR titrations of both molecular tweezers with fullerenes C60 and C70 were performed. While the first receptor exhibits the affinity for fullerenes comparable to the previously reported corannulene based receptors, the other with longer, naphthalene based tether, exceeds the performance of the former systems by ca. two orders of magnitude and, in addition, shows an enhanced preference for C70 over C60. These results are in line with the predictions based on MM modeling. The x-ray crystal structure of the 1:1 complex of the larger receptor with C60 indicates that the tether not only preorganizes the pincers into a proper topology to accept the host, but also contributes to the dispersion based binding with the fullerene guests. Fullerenes and their derivatives are frequently used as electron acceptors in polymer based solar cells. By amalgamation of fullerenes with organic receptors, like the ones reported here, the novel surface bound structures can be constructed with potential applications in nanotechnology and material sciences. DEDICATION This dissertation is dedicated to my husband (Saranga Kuragama), parents (Mr D. A. Abeyratne, Mrs P.G.P. Abeyratne, Mr Sunil Kuragama and Mrs Chandani Kuragama) and Siblings (Harsha Abeyratne, Gayani Abeyratne, Venuka Jayasundara, Chamath Perera, Dulip Kuragama and Bimali Senanayake) ii ACKNOWLEDGEMENTS First I wish to express my profound appreciation to my advisor Dr Andrzej Sygula for all his guidance, support and patience through my years at Mississippi State University. Your mentorship was paramount in providing a well-rounded experience in laboratory and I will always be grateful for that. I would especially like to thank Mrs Renata Sygula for all her help in the laboratory and her support through these years. A special thanks to Dr Michael Yanney for the encouragement and help given in the laboratory work throughout my PhD. To my committee members (Dr Stephen C Foster, Dr Keith T. Mead, Dr Todd Mlsna and Dr Dongmao Zhang) I say thank you for all your support and advice through my PhD program. I would like to thank my husband for the continuous support and encouragement provided all this time. Finally to all my friends and lab mates who were always there for me and I cherish your friendship throughout my life. iii TABLE OF CONTENTS DEDICATION .................................................................................................................... ii ACKNOWLEDGEMENTS ............................................................................................... iii LIST OF TABLES ............................................................................................................. vi LIST OF FIGURES ......................................................................................................... viii LIST OF SCHEMES........................................................................................................ xiii LIST OF ABBREVIATIONS AND CHEMICALS ........................................................ xiv CHAPTER I. INTRODUCTION .............................................................................................1 1.1 Fullerene as the Guest Molecule ............................................................3 1.2 Receptors for Fullerenes ........................................................................4 1.3 Molecular Receptors Based on Corannulene Pincers ..........................10 1.4 Thesis Aims .........................................................................................16 II. DESIGN OF BIS-CORANNULENE RECEPTORS BASED ON KLÄRNER’S TETHERS.................................................................................18 2.2 Molecular Receptors with Klärner’s Tethers .......................................22 2.3 Molecular Mechanics Studies as a Screening Tool .............................23 2.3.1 Conformational Preferences of 33 and 34 and their Binding Energies with Fullerenes ................................................................27 III. SYNTHESIS AND CHARACTERIZATION OF BIS- CORANNULENE RECEPTORS BASED ON KLÄRNER’S TETHERS ........................................................................................................32 3.1 Synthesis of Molecular Receptor 33 ....................................................32 3.1.1 Model Study: Optimization of the Reaction Conditions................33 3.1.2 Synthesis of Receptor 33 ...............................................................36 3.2 Synthesis of Molecular Receptor 34 ....................................................41 3.3 Synthesis of Molecular Receptor 34 ....................................................43 iv IV. BINDING STUDIES USING NMR SPECTROSCOPY ................................51 4.1 Introduction to NMR Spectroscopic Method .......................................51 4.2 Evaluation of the Binding Stoichiometry ............................................54 4.3 Fullerene Binding Studies with Clip 33 ...............................................55 4.3.1 Estimation of the Binding Constants of 33 with Fullerene in Toluene-d8 ......................................................................................59 4.4 Fullerene Binding Studies with Clip 34 ...............................................61 4.4.1 Binding Studies of Clip 34 with C60 ..............................................61 4.4.2 Binding Studies of Clip 34 with C70 ..............................................64 4.4.3 Binding Studies of Clip 34 with PCBM ........................................66 4.4.4 Estimations of the Binding Constants of 34 with Fullerenes in Chlorobenzene-d5.......................................................................67 4.5 Crystal Structure Determination for the Inclusion Complex Formation .............................................................................................72 4.6 Potential Applications of Molecular Receptors ...................................76 V. EXPERIMENTAL SECTION .........................................................................78 5.1 Synthesis of 38 .....................................................................................78 5.2 Synthesis of 33 .....................................................................................81 5.3 Synthesis of Dione 45 ..........................................................................83 5.4 Synthesis of 31 .....................................................................................86 5.5 Synthesis of Molecular Receptor 34 ....................................................88 5.6 Synthesis of Starting Materials ............................................................91 5.7 1H NMR Titration Experiments for clip 33 .........................................92 5.7.1 Titration of 33 with C60 in toluene-d8 ............................................92 5.7.1.1 Job’s plot for clip 33 with C60 ..................................................95 5.7.2