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Ultrafast Time Resolved and Computational Studies of Diazo and Diazirine Excited States, and of Carbenes DISSERTATION Presented

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Ultrafast Time Resolved and Computational Studies of Diazo and Diazirine Excited States, and of Carbenes DISSERTATION Presented Ultrafast Time Resolved and Computational Studies of Diazo and Diazirine Excited States, and of Carbenes DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Yunlong Zhang, M.S. Graduate Program in Chemistry The Ohio State University 2010 Dissertation Committee: Professor Matthew S. Platz, Advisor Professor Christopher M. Hadad Professor T. V. RajanBabu Copyright by Yunlong Zhang 2010 ABSTRACT Ab initio quantum calculations and ultrafast time-resolved laser flash photolysis techniques have been used to study singlet carbenes and the photochemistry of diazirines and diazo compounds. After a brief introduction of carbene chemistry in Chapter 1, the photophysics and photochemistry of aryldiazirines are investigated in Chapters 2 through 6. Detailed theoretical calculations begin with parent phenyldiazirine and its isomer phenyldiazomethane. The structures of the ground and electronic excited states (S 1, S 2, and S 3) of both compounds are optimized with RI-CC2 and DFT methods. The denitrogenation of both phenyldiazirine and phenyldiazomethane to produce singlet phenylcarbene, and the isomerization between both compounds, are investigated mechanistically on their potential energy surfaces. These predictions support the spectroscopic assignment in ultrafast studies of arylalkyldiazirines in chapters 3 – 6 and the accuracy of these theoretical methods are calibrated by the excellent agreement with experimental data. In Chapter 3 we present the first direct observation of singlet phenylcarbene and measurement of its lifetime in solution using ultrafast time-resolved infrared spectroscopy. In Chapter 4 we provide the first direct observation of the S 1 excited state of para -methoxy-3-phenyl-3-methyl diazirine ( p-CH 3OC 6H4CN 2CH 3) with both IR and UV–vis detection techniques. The S1 state of the diazirine decays into the ii diazo compound directly. The S 2 excited state is populated with 270 nm light and decays directly into singlet arylcarbene and diazo compound, as well as the S 1 state, via internal conversion. A Hammett study of the S 1 excited states is discussed in Chapter 5. An excellent linear correlation is obtained between the S 1 lifetimes of arylchlorodiazirines + and their para - substituent σp parameters. The effect of substitution of β-hydrogens on the S 1 state lifetimes is examined in Chapter 6 and is consistent with the RIES mechanism. The wavelength dependence effect on the photochemistry of aryldiazirines was discussed. In Chapter 7 we present the first direct observation of a singlet vinylcarbene and study its cyclization to a cyclopropene product in solution. Calculations predict that singlet vinylcarbene is highly delocalized over the C=C double bond. The photochemistry of N,N-diethyldiazoacetamide is detailed in Chapter 8. We concluded that the excited state of the diazoamide precursor undergoes direct intramolecular C−H insertions in forming both β- and γ -lactams, as well as denitrogenation to produce singlet carbene. The relaxed singlet carbene decays by isomerizing into γ-lactam in chloroform, and in methanol, this path is suppressed by intermolecular OH insertion reactions. iii DEDICATION Dedicated to my parents and my wife Na iv ACKNOWLEDGMENTS I would like to express my sincerest gratitude to my advisor, Dr. Matthew S. Platz. I am very lucky to be his student. His dedication, vision, and enthusiasm in research inspired me during my study at The Ohio State University. His guidance and encouragement has been instrumental in my studies, and his mentoring of both my research and personal development has been invaluable. I would like to thank Dr. Christopher M. Hadad and Dr. T.V. RajanBabu for serving on my dissertation committee and their insights and suggestions and endless help with my research through the years. I also enjoy the collaboration with Dr. Robert A. Moss at Rutgers and Dr. Guy Buntinx at Lille and thank them for their stimulating discussions. It has been a great honor and pleasure to work with the members in the Platz group. Special thanks go to the two gifted physicists Dr. Jacek Kubicki and Dr. Gotard Burdzinski. Both have given me tremendous assistance. I am also grateful to Dr. Jin Wang who has offered me endless advice and help on my initial days in the lab. I also thank Dr. Arthur Winter and Mr. Shubham Vyas for their help on the calculations. Furthermore, I would like to thank the help and friendship from in and out of the Platz v group, particularly Drs. Peter Selvaraj, Biswajit Saha, Huolei Peng, Jiadan Xue, Ozlem Dogan Ekici, Chris Middleton, Muthukrishnan Siva, Michel.Sliwa, and Mr. Calvin Luk Beyond my fellow co-workers, I would like to acknowledge my best friends in Columbus, Yujie Sun, Wenlan Chen, Siyu Tu, Xiaozhao Wang and Chuang Tan. I am extremely grateful for their friendship, help, encouragement, and the time we spent together. Finally, I must thank my parents and my wife Na. They have been extremely supportive and considerate for my work and in my life. I thank for their endless love and sacrifices. vi VITA March 15, 1980 ………………………………….……… Born – Shangqiu, Henan, China July, 2002 ………….……………………………………………………… B.S. Pharmacy Tianjin Medical University, Tianjin, China July, 2005 ……………………………………….......................... M.S. Organic Chemistry Shanghai Institute of Materia Medica Chinese Academy of Sciences, Shanghai, China 2005 – 2007 ………………………… Graduate Teaching Assistant, College of Pharmacy The Ohio State University 2007 – 2008 …………………… Graduate Teaching Assistant, Department of Chemistry The Ohio State University 2008 – 2010 …………………… Graduate Research Assistant, Department of Chemistry The Ohio State University 2010 ……………………………………………………. Gerhard L. Closs Student Award Inter-American Photochemistry Society 2010 ………………………… Henne Research Award Finalist, Department of Chemistry The Ohio State University vii PUBLICATIONS 1. Burdzinski, G.; Zhang, Y.; Selvaraj, P.; Sliwa, M.; Platz, M. S. "Direct Observation of 1,2-Hydrogen Migration in the Excited States of Alkyl Diazo Esters by Ultrafast Time Resolved IR Spectroscopy," J. Am. Chem. Soc , 2010 , ASAP . 2. Zhang, Y.; Wang, L.; Moss, R. A; Platz, M. S. "Ultrafast Spectroscopy of Arylchlorodiazirines: Hammett Correlations of Excited State Lifetimes," J. Am. Chem. Soc, 2009 , 131 , 16652-16653. 3. Zhang, Y.; Burdzinski, G.; Kubicki, J.; Vyas, S; Hadad, C. M; Sliva, M; Buntinx, G; Platz, M. S. "A Study of the S 1 Excited State of para -Methoxy 3-Phenyl-3- Methyl Diazirine by Ultrafast Time Resolved UV-Vis and IR Spectroscopies and Theory," J. Am. Chem. Soc. 2009 , 131 , 13784-13790. 4. Zhang, Y.; Kubicki, J.; Platz, M. S. "Ultrafast UV –vis and Infrared Spectroscopic Observation of a Singlet Vinylcarbene and the Intramolecular Cyclopropenation Reaction," J. Am. Chem. Soc. 2009 , 131 , 13602-13603 . 5. Zhang, Y.; Burdzinski, G.; Kubicki, J.; Platz, M. S. "Ultrafast Time Resolved Infrared Spectroscopy Study on the Photochemistry of N,N- Diethyldiazoacetamide. Rearrangement in the Excited State (RIES)," J. Am. Chem. Soc. 2009 , 131 , 9646-9647. 6. Kubicki, J.; Zhang, Y.; Wang, J.; Luk, H. L.; Peng, H.-L.; Vyas, S.; Platz, M. S. "Direct Observation of Acyl Azide Excited States and Their Decay Processes by Ultrafast Time Resolved Infrared Spectroscopy," J. Am. Chem. Soc. 2009 , 131 , 4212-4213. 7. Zhang, Y.; Burdzinski, G.; Kubicki, J.; Platz, M. S. "Direct Observation of Carbene and Diazo Formation from Aryldiazirines by Ultrafast Infrared Spectroscopy," J. Am. Chem. Soc. 2008 , 130, 16134-16135. viii 8. Zhang, Y.; Kubicki, J.; Wang, J.; Platz, M. S. "2-Naphthyl(carbomethoxy)carbene Revisited: Combination of Ultrafast UV –vis and Infrared Spectroscopic Study," J. Phys. Chem. A 2008 , 112 , 11093-11098. 9. Wang, J.; Zhang, Y.; Kubicki, J.; Platz, M. S. “Ultrafast studies of Some Diarylcarbenes” Photochem. Photobiol. Sci. 2008 , 7, 552-557. 10. Porchia, L. M.; Guerra, M.; Wang, Y.-C.; Zhang, Y.; Espinosa, A. V.; Shinohara, M.; Kulp, S. K.; Kirschner, L. S.; Saji, M.; Chen, C.-S.; Ringel, M. D. "2-Amino- N-{4-[5-(2-phenanthrenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]-phenyl} Acetamide (OSU-03012), a Celecoxib Derivative, Directly Targets p21-Activated Kinase," Mol. Pharmacol. 2007 , 72 , 1124-1131. 11. Zhang, Y.; He, Q.; Ding, H.; Wu, X.; Xie, Y. "Improved Synthesis of Tadalafil," Org. Prep. Proc. Int. 2005 , 37 , 99-102. FIELDS OF STUDY Major Field: Chemistry Physical Organic Chemistry ix TABLE OF CONTENTS Page Abstract............................................................................................................................... ii Dedication.......................................................................................................................... iv Acknowledgements............................................................................................................. v Vita.................................................................................................................................... vii Puplications......................................................................................................................viii List of Schemes................................................................................................................ xvi List of Tables .................................................................................................................xviii List of Figures................................................................................................................
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