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Studies of Oriented Aromatic Hydrocarbons in the Phos­ Phorescent State at Low Magnetic Fields

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Studies of Oriented Aromatic Hydrocarbons in the Phos­ Phorescent State at Low Magnetic Fields WINER, Arthur Melvyn, 1942- ELECTRON PARAMAGNETIC RESONANCE STUDIES OF ORIENTED AROMATIC HYDROCARBONS IN THE PHOS­ PHORESCENT STATE AT LOW MAGNETIC FIELDS. The Ohio State University, Ph.D., 1969 Chemistry, physical University Microfilms, Inc., Ann Arbor, Michigan THIS DISSERTATION HAS BEEN MICROFILMED EXACTLY AS RECEIVED ELECTRON PARAMAGNETIC RESONANCE STUDIES OF ORIENTED AROMATIC HYDROCARBONS IN THE PHOSPHORESCENT STATE AT LOW MAGNETIC FIELDS DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Arthur Melvyn Winer, B.S, ***** The Ohio State University 1969 Approved by Adviser Department of Chemistry To My Father ii ACKNOWLEDGMENTS It is a pleasure to acknowledge the contribution to this work of Professor Roger E. Gerkin, who not only pro­ vided direction and encouragement throughout the research, for which I am grateful, but who also established an atmos­ phere of conviviality which made my tenure as his student most enjoyable. Valuable discussions with Mr. William J. Rogers, Mr. Peter Szerenyi and Mr. David L. Thorsell of this labora­ tory and with Professor Clyde A. Hutchison of the Univer­ sity of Chicago are gratefully acknowledged. I wish to thank Mr. Thorsell also for taking the photographs of research equipment which appear in the dissertation. The work of Mr. Terence Ireland in maintaining and improving the electronic equipment was essential to the completion of this research and was greatly appreciated. I wish to thank Professor Jack G. Calvert, Dr. Susan Collier and Dr. T. Navaneeth Rao for use of the Turner spectrophotometer, and Professor Peter W. R. Corfield for iii iv use of an x-ray diffractometer and for his consultation concerning the crystal structure analysis of p-terphenyl. Fellowships from the Gulf Oil Corporation and the Continental Oil Company provided helpful financial assis­ tance during the final two years of research. Computer facilities were provided by The Ohio State University Computer Center. I am deeply grateful to ray parents for their con­ tinuous support and encouragement throughout the years of ray education. Finally, I would like to express my sincere gratitude to ray wife, Jane, who stood by me through the many and sometimes difficult years of study and research, and who therefore deserves to share fully in this accomplishment. ip VITA 1942, Hay 5 Born - New York City, New York 1962-1964 Laboratory Assistant, Korad Corporation, Santa Monica, California 1964 National Science Foundation Undergraduate Research Participant, Department of Chemistry, University of California at Los Angeles, Los Angeles, California 1964 B.S. Chemistry, University of California at Los Angeles, Los Angeles, California 1964-1966 Teaching Assistant, Department of Chemistry, The Ohio State University, Columbus, Ohio 1966-1967 Research Assistant, Department of Chemistry, The Ohio State University, Columbus, Ohio 1967-1968 Gulf Fellow, Department of Chemistry, The Ohio State University, Columbus, Ohio 1968-1969 Continental Oil Fellow, Department of Chemistry, The Ohio State University, Columbus, Ohio PUBLICATIONS "The Decay of 0£ (a ) in Flow Experiments^' J. Phys. Chem. 70, 302 (1966). Co-authored with Dr. Kyle D. Bayes, Department of Chemistry, University of California at Los Angeles, Los Angeles, California v vi "Observation of Multiplet Structure in Low-Field Magnetic Resonance Spectra of Triplet States of Oriented Aromatic Hydrocarbons." J. Chera. Phys. 47, 2504 (1967). Co-authored with Dr. Roger E. GerkinTHDepartment of Chemistry, The Ohio State University, Columbus, Ohio "Deuterium Isotope Effect in Zero-Field Splittings of Phosphorescent Fhenanthrene Oriented in Biphenyl." J. Chem. Phys. 50, 3114 (1969). Co-authored with Dr. Roger E. Gerkin7"~bepartment of Chemistry, The Ohio State University, Columbus, Ohio "Proton Hyperfine Structure at Magnetic Fields Below — 100 G in Electron Magnetic Resonance Absorptions by Triplet States of Aromatic Molecules." J. Chera. Phys. 51, 1664 (1969). Co-authored with Dr. Roger E. Gerkin7*~bepartraent of Chemistry, The Ohio State University, Columbus, Ohio FIELDS OF STUDY Major Field: Physical Chemistry Studies in Kinetics. Professor Frank Verhoek Studies in Thermodynamics. Professors George E. MacWood and David White Studies in Quantum Mechanics. Professor William J. Taylor TABLE OF CONTENTS DEDICATION................................... ii ACKNOWLEDGMENTS .............................. iii VITA ......................................... v LIST OF TABLES ............................... xi LIST OF FIGURES .............................. xiv Chapter I. INTRODUCTION AND HISTORICAL BACKGROUND .. 1 Introduction Historical Background II. THEORY............................... 9 Introduction The Spin Hamiltonian Solution of the Fine-Structure Spin Hamiltonian The Low-Field Eigenvalues III. EXPERIMENTAL APPARATUS AND METHODS ..... 18 The Low Field Spectrometer Static Magnetic Fields The Helmholtz Magnet Static-Field Measurements Cancellation of the Laboratory Field Calibration of the Helmholtz Magnet Homogeneity of the Resultant Field Microwave Fields Frequency Counting Signal Detection Optical System Crystal Temperature The High Field Spectrometer vii viii Chapter Page IV. PREPARATION OF SAMPLES.................. 42 Purification of Materials Guest Materials Chrysene-h^ 2 2,3-Benzocarbazole Chrysene-di2 1,2; 5,6-Dibenzanthracene-h^4 1,2; 5,6-Dibenzanthracene-d^4 Naphthalene-hg Naphthalene-dg Phenanthrene-nxo Phenanthrene-d^Q Dibenzothiophene 1,2,3,4-Tetrahydroanthracene Picene Host Materials p-Terphenyl-hi4 p-Terphenyl-dj* Symmetric Octanydroanthracene Biphenyl Durene 2,2'-Binaphthyl p-Quaterphenyl 2,6-Dimethylnaphthalene Growth of Single Crystals Host Crystal Structures p-Terphenyl Symmetric Octahydroanthracene 2,2*-Binaphthyl EXPERIMENTAL RESULTS AND DISCUSSION FOR ORIENTED CHRYSENE IN ITS PHOSPHORESCENT S T A T E .............................. 68 Introduction Multiple Resonance Absorption in Low-Field Fine-Structure Spectra of Triplet Chrysene Oriented in p-Terphenyl Zero-Field Splittings and Spin Hamiltonian Parameters for Chrysene Basic Relations Triplet Chrysene-d^ in Single Crystals of p-Terphenyl-h^ 4 Triplet Chrysene-d^ 2 in Single Crystals of p-Terphenyl-di4 Triplet Chrysene-d^ in Single Crystals of s-Octahydroanthracene Triplet Chrysene-dio in Single Crystals of Biphenyl ix Chapter Page Multiple Orientation of Chrysene Triplets in Single-Crystal Hosts Lifetime of the Triplet State of Chrysene-d^ Chrysene-d^ 2 1° Single-Crystal Hosts p-Terphenyl-hi4 Host s-Octahydroanthracene Host Chrysene-di2 1° EPA Glasses Temperature Dependence of the Zero-Field Splittings of Chrysene-di2 in p- Terphenyl-hi4 and s-Octanydroanthracene Deuteration Effects Deuteration of Chrysene Deuteration of p-Terphenyl Conclusion VI. EXPERIMENTAL RESULTS AND DISCUSSION FOR OTHER MIXED CRYSTAL SYSTEMS.............. 160 1,2; 5,6-Dibenzanthracene Oriented in p- Terphenyl and in 2,2*-Binaphthyl 2,3-Benzocarbazole Oriented in p-Terphenyl and in Chrysene Impurity in s-Octahydroanthracene VII. DEUTERIUM ISOTOPE EFFECTS IN ZERO-FIELD SPLITTINGS OF PHOSPHORESCENT PHENANTHRENE ORIENTED IN BIPHENYL.................... 170 Introduction Results for Phenanthrene Oriented in Biphenyl Discussion VIII. PROTON HYPERFINE STRUCTURE AT MAGNETIC FIELDS BELOW -100 GAUSS IN MAGNETIC RESONANCE AB­ SORPTIONS BY TRIPLET STATES OF AROMATIC HYDROCARBONS ............................ 192 Introduction Results and Discussion Reasons for Previous Failures to Observe Hyperfine Structure at Low Fields Comparisons of High-Field and Low-Field Hyperfine 'Patterns Low Fields Between — 75 and — 100 G Zero Field and Fields Below — 50 G Effects of Resolved Proton Hyperfine Structure on Precision Determinations of Zero- Field Splittings at Low Fields Chapter Page IX. SUGGESTIONS FOR FURTHER RESEARCH ......... 213 Introduction Mixed Crystal Systems to be Investigated Picene in p-Terphenyl p-Terphenyl-h^ and p-Terphenyl-d^ In 4,> Dimethylbiphenyl p-Quaterphenyl Investigation of Multiplet Structure in Optical Spectra of Organic Mixed Crystals APPENDIX A. Formulas for g-Tensor Diagonal Elements ... 220 B. Computer Program Listings ................ 222 Calculation of g-Tensor Diagonal Elements Least-Squares Calculations Calculation of Limiting Phosphorescent Lifetime REFERENCES CITED .................................. 230 LIST OF TABLES Table Page 1. Emission spectrum of chrysene-d^2 EPA glass at 77K.................................. 46 2. Magnetic resonance data for chrysene-d^2 oriented in p-terphenyl: Transitions near - 0.116 cm"1................................. 89 3. Magnetic resonance data for chrysene-di2 oriented in p-terphenyl: Transitions near - 0.063 cra~l................................. 90 4. Magnetic resonance data for chrysene-d^2 oriented in p-terphenyl: Transitions near - 0.053 cm"1................................. 91 5. Triples of best values of zero-field splittings for chrysene"di2 in p-terphenyl 97 6. Predicted and experimental values of lD + E[/hc for chrysene-d^2 p-terphenyl..... 99 7. Magnetic resonance data for chrysene-d^o oriented in s-octahydroanthracene and in biphenyl...... 102 8. Zero-field splittings and spin Hamiltonian parameters of chrysene-d^2 *n s-octahydro- anthracene................................... 104 9. Angles between the projection of H in the BC plane and B]_ and B2 for chrysene'triplet states in p-terphenyl......................... 117 10. Angles between H and the B fine structure axes of the two translationally
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