Excited State Processes in Ruthenium(Ii) Polypyridyl Complexes

EXCITED STATE PROCESSES IN RUTHENIUM(II) POLYPYRIDYL COMPLEXES AND CERIUM OXIDE NANOPARTICLES by Charles William Stark A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry MONTANA STATE UNIVERSITY Bozeman, Montana November 2016 ©COPYRIGHT by Charles William Stark 2016 All Rights Reserved ii DEDICATION To Dolly, who taught me knowing what’s important is the most important thing to know. iii ACKNOWLEDGEMENTS I would first like to thank my advisor Professor Bern Kohler for his patience and persistent support throughout my Ph.D studies. His guidance helped in many ways make my research more respectable, and his vast knowledge illuminated deeper meanings to my findings that I would have not noticed on my own. I simply could not have gotten where I am now without his help. Besides my advisor, I would also like to thank the rest of my committee: Professor Aleks Rebane, Professor Pat Callis, Professor Erik Grumstrup, as well as Professor Rob Walker. The meetings that we had helped me develop the ability to set clear research goals and meet them in a (somewhat) timely manner. Moreover, I am extremely grateful to have had such people available as resources when I was confronted with a bewildering problem. I would also like to express my gratitude towards my research collaborators: Professor Trevor Douglas, Dr. Wolfgang Schreier, Dr. Janice Lucon, Dr. Ethan Edwards, Natasha Pettinger and Arianna Celis, without whom I would have been unable to perform the majority of my research. In particular, I would like to thank Dr. Wolfgang Schreier, who taught me much of the artistry that is data collection, and that electronic manipulation can be just as important as the optics in spectroscopy. Finally, I thank my fellow lab mates: Tom Zhang, Jinquan Chen, Jacob Remington, Ashley Beckstead, David Skowron, Jordan Dood, Rebecca Danforth and Ben Smith. Although science can sometimes be painfully unforgiving, it helps to know that I am not alone. iv TABLE OF CONTENTS 1. INTRODUCTION ...........................................................................................................1 References ........................................................................................................................8 2. GENERAL METHODS.................................................................................................15 Preface............................................................................................................................15 2.1 Transient Absorption ...............................................................................................15 2.1.1 Transient Absorption Spectrometers .................................................................15 2.1.2 Visible Pump/Probe Transient Absorption: General Methods ..........................16 2.1.3 Visible Pump/Probe Transient Absorption: Single Wavelength Signals ..........18 2.1.4 Visible Pump/Probe Transient Absorption: Anisotropic Signals ......................18 2.1.5 Visible Pump/Probe Transient Absorption: Broadband Spectra .......................19 2.1.6 Visible Pump/Infrared Probe Transient Absorption Spectra .............................20 2.2 Emission Lifetimes ..................................................................................................22 2.2.1 Emission Lifetime Single Wavelength Signals .................................................22 2.2.2 Time Resolved Emission Spectra ......................................................................23 2.3 Steady-State Measurements .....................................................................................24 2.3.1 UV/Vis/NIR Absorption Measurements ...........................................................24 2.3.2 Visible/NIR Emission Measurements ...............................................................24 2.3.3 Fourier Transform Infrared Spectroscopy .........................................................25 2.3.4 Transmission Electron Microscopy ...................................................................26 2.3.5 Acid-Base titration ............................................................................................26 2.4 Sample Handling ......................................................................................................26 2.4.1 Materials ............................................................................................................26 2.4.2 Spectroscopic Cuvettes .....................................................................................28 2.4.3 Nitrogen Purging ...............................................................................................28 2.4.4 High-Performance Liquid Chromatography Purification..................................29 2.4.5 Cerium Oxide Nanoparticle Preparation ...........................................................29 2.4.6 UV Photoreactor ................................................................................................30 2.5 Data Treatment.........................................................................................................31 2.5.1 Modeling Transient Absorption Signals ...........................................................31 2.5.2 Modeling Emission Lifetimes ...........................................................................31 2.5.3 Emission Spectral Corrections ..........................................................................32 References ......................................................................................................................42 v TABLE OF CONTENTS – CONTINUED 3. INTERLIGAND ELECTRON TRANSFER IN HETEROLEPTIC RUTHENIUM(II) COMPLEXES OCCURS ON MULTIPLE TIME SCALES .................................................................43 Contribution of Authors and Co-Authors ......................................................................43 Manuscript Information Page ........................................................................................44 Abstract ..........................................................................................................................45 3.1 Introduction ..............................................................................................................46 3.2 Experimental Methods .............................................................................................49 3.2.1 Ruthenium Complex Synthesis .........................................................................49 3.2.2 Spectroscopic Measurements ............................................................................51 3.3 Results ......................................................................................................................55 3.3.1. Steady-State Measurements .............................................................................55 3.3.2 Emission Lifetimes ............................................................................................56 3.3.3 Transient Anisotropy Measurements ................................................................56 3.3.4 Magic Angle TA Experiments ..........................................................................57 3.4 Discussion ................................................................................................................61 3.4.1. Steady-State Absorption Spectra ......................................................................61 3.4.2 Emission Lifetimes ............................................................................................61 3.4.3 Excited-State Dynamics: Time-Resolved Anisotropy ......................................63 3.4.4 Excited-State Dynamics: Magic Angle TA Experiments..................................64 3.4.5 Time-Dependent Localization on bpy ...............................................................68 3.4.6 ILET Rates are Time-Dependent ......................................................................71 3.5 Conclusions ..............................................................................................................74 Associated Content ........................................................................................................76 Author Information ........................................................................................................76 Acknowledgements ........................................................................................................76 References ......................................................................................................................86 4. PHOTOINDUCED ELECTRON TRANSFER OBSERVED IN A CLICK-FUNCTIONALIZED RUTHENIUM(II)-COBALT(II) SUPRAMOLECULAR COMPLEX ..............................................................................91 4.1 Introduction ..............................................................................................................91 4.2 Results ......................................................................................................................95 4.2.1 Steady-State UV/Visible/NIR Absorption Spectra ...........................................95 4.2.2 Steady-State Emission Spectra ..........................................................................96 4.2.3 Emission Quantum Yields and Stern-Volmer Quenching ................................97 4.2.4 Time-Resolved Emission Signals ......................................................................98 vi TABLE OF CONTENTS – CONTINUED 4.2.5 Broadband and Single

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