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Synthesis, Characterization, Thermodynamic, and Kinetic Studies of Vapochromic Pt(II) Complexes

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Synthesis, Characterization, Thermodynamic, and Kinetic Studies of Vapochromic Pt(II) Complexes Synthesis, Characterization, Thermodynamic, and Kinetic Studies of Vapochromic Pt(II) Complexes. A dissertation submitted to the Division of Research and Advanced Studies of the University of Cincinnati in partial fulfillment of the requirements for the Degree of Doctor of Philosophy (Ph.D.) in the Department of Chemistry of the College of Arts and Sciences 2018 by Mahmood Karimi Abdolmaleki M.S., University of Cincinnati, 2016 M.Sc., Isfahan University of Technology, Iran 2008 B.Sc., Arak University, Iran 2004 Committee Chair: Dr. William B. Connick Abstract Vapochromic materials, undergoes a reversible color change upon exposure to certain volatile organic compounds (VOCs). Since color changes are easily detected by eye, these materials are potentially useful in the detection of specific hazardous volatile compounds (e.g., NH3, pyridine, CO, H2S). Therefore, there is considerable interest in understanding the properties of vapochromic materials and their potential practical uses. The most well-known class of vapochromic materials are solids containing molecular platinum(II) complexes, which have been the focus of numerous studies. The tendency of solids containing square-planar d8-electron platinum metal centers to exhibit vapochromic properties is related in part to the propensity of these complexes to form close non-covalent Pt…Pt contacts, which have a strong influence on the solid-state color (e.g., yellow, orange, red, purple) and spectroscopy of these materials. The color changes upon vapor absorption and desorption typically are not a result of chemical reaction. Instead, they are related to vapor absorption/desorption induced changes in crystal packing and intermolecular interactions. The resulting changes in Pt…Pt distances have a dramatic effect on the color and luminescence properties of these materials. However, despite considerable progress, the discovery of vapochromic platinum(II) systems remains largely serendipitous. Moreover, the vapochromic mechanism, energetics, morphological factors, and the relationship between spectroscopic properties, structure, and the sorption/desorption kinetics and thermodynamics are not fully understood. This lack of understanding is preventing researchers from rationally tailoring the response time, selectivity, and sensitivity, as required for sensing applications. Chapter 2 describes the use of a cell phone camera and the CIELAB method (color space specified by the International Commission on Illumination) to characterize the color change in different vapochromic systems. In this study we have developed a semi-automatic color change analysis software that digitally analyzes images (e.g., video frames) collected while a vapochromic material is absorbing or desorbing vapor. Chapter 3 reports a detailed investigation of [Pt(dcmbpy)Cl2].CH2Cl2, which exhibits the unusual behavior of responding to certain vapors without vapor uptake. Specifically, red, solid [Pt(dcmbpy)Cl2].CH2Cl2 changes to green and finally to a yellow material upon exposure to acetone, THF, and methanol vapors. Chapter 4 reports the first example of the determination of the enthalpy of vaporization (ΔHvap) and activation energy (Ea) for solvate loss for a homologous series of vapochromic materials. In addition to these parameters, we have evaluated parameters describing sensitivity, speed of color change during vapor desorption, speed of color change during vapor absorption, and the volume attributed to the acetonitrile molecule in the solvate structures of nine salts having very similar compositions. Acknowledgements The work detailed in this dissertation would not be possible without the support of some truly wonderful people. First and foremost, I would like to thank my research advisor, Professor Bill Connick., not only for his tremendous academic support, but for his excellent guidance, enthusiasm, motivation, patience, , professionalism, and immense knowledge. I have been incredibly fortunate to have an advisor who gave me the freedom to explore new area in my research. His guidance has helped me to be more independent, both professionally and as a person. I will carry his philosophy and vision throughout my professional career and life. I also would like to thank my dissertation committee members, Prof. Bruce Ault, Prof. Michael J. Baldwin, and Dr. Robert Streicher for their valuable feedback and comments and recommendation letters. My special thanks to Dr. Streicher who gave me the opportunity to work in his group at NIOSH which was a valuable experience during my PhD. I am grateful to Dr. Kaval Necati for always being encouraging and helpful. His comments and feedback were great help to improve the results of this work. I would like to thank Dr. Pablo Rosales and Dr. Melodie Fickenscher for SEM and DSC-TGA training. I also would like to thank our departmental crystallographer Dr. Jeanette Krause for the crystallographic work reported in this dissertation. I would like to thank my dear friend Sadegh Riasi for his contribution in color change analysis. I would also like to thank the past and present members of the Connick Group. Vikas, Amie, Kumudu, and Daoli were very welcoming and great help while I was getting started in the lab. I would also like to thank Angela, Jessie, Nate, Spencer, and Caroline for being great labmates. I would like to thank my undergraduates Mark Bovee, Kelsey Mengle, Xi Lin, Alexander Cassandra, and Rajiv Karani for their valuable contribution in different projects. Finally, I would like to thank my family for their unconditional support, and for believing in me. I owe everything I have to my parents who I admire and love. To my parents, Ali and Farah. Table of Contents Table of Contents i List of Tables iii List of Schemes iv List of Figures v List of Abbreviations and Symbols xi Chapter 1 Introduction 1 References 10 Chapter 2 A Digital Imaging Method for Evaluating the Kinetics of 20 Vapochromic Response Introduction 20 Experimental sections 23 Materials and methods 23 Synthesis and imaging of [Pt(tpy)Cl]ClO4.H2O at different humidity 23 levels. - - - Synthesis and imaging of [Pt(tpy)X ]YF6 (X = Cl , Br and I ; Y = P, 24 As and Sb) salts. Synthesis and imaging of [Pt(dcmbpy)Cl2].CH2Cl2. 25 Color Change Analysis 26 Results and Discussion 30 Determining the influence of vapor pressure on vapochromic 30 response. Simultaneous measurements of vapochromic response for 33 comparative kinetic studies Detection of an intermediate in a vapochromic process. 37 Conclusion 39 References 41 Appendix 51 i Chapter 3 Vapochromic materials that do not incorporate vapors in the 66 crystal lattice and form Nano fibers Introduction 66 Experimental 68 Materials 68 Synthesis of Pt(dcmbpy)Cl2.CH2Cl2 (R1.CH2Cl2 and R1.CH2Cl2), 68 and Pt(dcmbpy)Cl2 (Y). Characterization and Methods 69 Structure Determination 70 Results and discussion 73 Dichloromethane Solvates of Pt(dcmbpy)Cl2 73 Vapochromism 74 Characterization of Materials 76 Vapoluminescence 79 Vapor-Induced Recrystallization 81 Morphological Changes 82 Conclusion 87 References 88 Appendix 90 Chapter 4 Thermodynamics and Kinetics of a Series of Closely Related 92 Vapochromic Platinum(II) Salts Introduction 92 Experimental sections 94 Materials 94 - - - Synthesis of [Pt(tpy)X ]YF6 (X = Cl , Br and I ; Y = P, As and Sb) 94 salts. - - - Kinetics of response of [Pt(tpy)X ]YF6 salts (X = Cl , Br and I ; Y = 94 P, As and Sb) Determination of Enthalpies of vaporization (ΔHvap). 95 Determination of Activation Energies 95 Evaluation of Sensitivities 95 ii Void volume measurement 96 Results and Discussion 96 Correlation between ΔHvap, Ea, 푡1/2 of absorption, 푡1/2 of 101 desorption, limiting vapor pressure of acetonitrile (Vp) (mm Hg), - - and void volume (VV) of the [Pt(tpy)X ]YF6 salts (X = Cl , Br and I-; Y = P, As and Sb). Conclusion 104 References 105 Appendix 109 List of Tables Chapter 2 Table 1 The vapochromic response was monitored over time, and the rate of 36 color change plot was used to determine the onset, end, and duration of the absorption. Table A1 The vapochromic response was monitored over time, and the rate of 63 color change plot was used to determine the onset, end, and duration of the desorption. Table A2 The vapochromic response was monitored over time, and the rate of 63 color change plot was used to determine the Smax, and Area under the S versus time of the absorption and desorption. Chapter 3 Table 1 Crystallographic Data for Pt(dcmbpy)Cl2.CH2Cl2 (R1.CH2Cl2) and 72 Pt(dcmbpy)Cl2 (Y) at (150 K) Chapter 4 iii Table 1 Values of the enthalpy of vaporization (ΔHvap), activation energy 100 (Ea), 푡1/2absorption, 푡1/2 desorption, limiting acetonitrile vapor - pressures (Vp), and solvate void volumes for [Pt(tpy)X]YF6 (X = Cl , - Br- and I ; Y = P, As and Sb) salts, (Note: error bars are ±2σ). Table 2 Table 2. Pearson correlation coefficients (r) for relationships between 102 Ea, ΔHvap, 푡1/2 of absorption, 푡1/2of desorption, limiting acetonitrile vapor pressure (Vp), and void volume (VV). List of Schemes Chapter 1 Scheme 1 Line drawing of Pt(tpy)Cl+. 4 Scheme 2 [Pt(dcmbpy)Cl2].CH2Cl2 9 Chapter 2 Scheme 1 Line drawing of [Pt(tpy)Cl]ClO4.H2O 23 + - - - Scheme 2 Line drawing of [Pt(tpy)X ]YF6 (X = Cl , Br and I ; Y = P, As and Sb) 24 Scheme 3 Line drawing of [Pt(dcmbpy)Cl2].CH2Cl2 25 - - - Scheme 4 Array of [Pt(tpy)X]YF6 ([X]YF6) (where X = Cl , Br and I ; Y = P, As 34 and Sb) salts and their qualitative colors in the absence (upper left of diagonal) and presence (lower right of diagonal) of acetonitrile vapor, which produces the acetonitrile solvate. [Cl]SbF6 and [Br]SbF6 do not absorb acetonitrile vapor, as indicated by the solid diagonal line. Chapter 3 Scheme 1 [Pt(dcmbpy)Cl2].CH2Cl2 68 Scheme 2 Vapochromic properties of the Pt(dcmbpy)Cl2 system. (i): R1CH2Cl2, 74 (ii): R2CH2Cl2 Chapter 4 iv - - - Scheme 1 Line drawing of [Pt(tpy)X]YF6 (X = Cl , Br and I ; Y = P, As and Sb) 94 Scheme 2 Array of [Pt(tpy)X]YF6 complexes and their response to acetonitrile 97 Scheme 3 Schematic showing the thermodynamic and kinetics parameters for the 101 release of acetonitrile from [Pt(tpy)X]YF6.CH3CN.
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