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Dissertation Development of Novel Catalysts for the Photocatalytic Hydrogen Formation Dissertation zur Erlangung des akademischen Grades doctor rerum naturalium (Dr. rer. nat.) vorgelegt dem Rat der Chemisch-Geowissenschaftlichen Fakultät der Friedrich-Schiller-Universität Jena von Diplomchemiker Thomas David Pilz geboren am 24. Mai 1982 in Rochlitz, Deutschland Gutachter: 1. Prof. Dr. Sven Rau 2. Prof. Dr. Ulrich S. Schubert 3. Prof. Garry S. Hanan Tag der öffentlichen Verteidigung: 16. 11. 2011 Diese Arbeit entstand auf Anregung und unter Anleitung von Prof. Dr. Sven Rau und Prof. Dr. Matthias Westerhausen im Zeitraum von Januar 2008 bis Juni 2011 am Institut für Anorganische und Analytische Chemie der Friedrich-Schiller-Universität Jena. Den Herren Prof. Dr. Sven Rau und Prof. Dr. M. Westerhausen danke ich ganz herzlich für ihre langjährige und großzügige Unterstützung und Förderung, die interessante und zukunftsrelevante Themenstellung und die damit verbundenen, stets aufschlussreichen und inspirierenden Diskussionen. Der Carl-Zeiss-Stiftung danke ich für die Gewährung und Verlängerung eines großzügigen Promotionsstipendiums. Weiterhin danke ich dem Bayerischen Hochschulzentrum für Mittel-, Ost- und Südosteuropa BAYHOST für ein Reisestipendium nach Lviv (Ukraine). Dem DFG Graduiertenkolleg 1626 Chemical Photocatalysis danke ich für die finanzielle Unterstützung bei der Teilnahme an der ISPPCC Konferenz in Strasbourg (Frankreich) sowie für die vielen Weiterbildungsangebote. Außerdem danke ich meinen Kooperationspartnern, der Arbeitsgruppe von Prof. Dr. D. M. Guldi aus Erlangen, speziell K. Peuntinger, und der Arbeitsguppe Prof. Dr. B. Dick aus Regensburg, speziell R.-J. Kutta, für die photophysikalischen Untersuchungen an den Rutheniumkomplexen. Weiterhin danke ich der Arbeitsgruppe von Herrn Prof. Dr. T. Drewello aus Erlangen, speziell J. Li, für die Durchführung detaillierter massenspektrometrischer Untersuchungen und Prof. Dr. J. G. Vos aus Dublin für das Mitwirken an der Arbeit zu den NHC-Komplexen. Zudem sei meiner gesamten Arbeitsgruppe und den Arbeitsgruppen von Prof. Dr. H. Kisch, Prof. Dr. K. Meyer und von Prof. Dr. M. Westerhausen, speziell Dr. C. Koch, für die angenehme und freundschaftliche Atmosphäre im Laboralltag gedankt. An dieser Stelle möchte ich mich bei allen Mitarbeitern des IAAC in Jena und des IAC in Erlangen bedanken, dich mich bei der Anfertigung dieser Arbeit unterstützt und zu ihrem Gelingen beigetragen haben. Insbesondere bedanke ich mich bei Herrn Dr. M. Friedrich, Frau A. Blayer und Frau B. Rambach für die Aufnahme von NMR-Spektren in Jena sowie bei den Herren Dr. A. Zahl und Dr. M. Moll für Einweisung und Hilfestellungen bei der Bedienung der NMR-Spektrometer in Erlangen. Herrn Dr. W. Poppitz, Frau M. Heineck und Frau S. Schönau aus Jena danke ich für die Durchführung weiterer massenspektrometrischer Untersuchungen. Zudem danke ich Frau R. Suxdorf, Frau H. Schönfeld, Frau B. Lentvogt und Frau C. Wronna für die Anfertigung der Elementaranalysen in Jena und Erlangen. Herrn Dr. H. Görls aus Jena und Dr. F. W. Heinemann aus Erlangen möchte ich für die röntgenstrukturanalytischen Untersuchungen sowie die anregenden Diskussionen danken. Für Mitbenutzung der Glovebox und die Bereitstellung der Geräte zur Cyclovoltammetrie und der Inertlösemittelanlage danke ich dem Erlanger Arbeitskreis von Prof. Dr. K. Meyer und speziell Dr. R. Beranek, Frau C. Vogel und Herrn B. Kosog. Herrn M. Pfeffer und Herrn S. Hansen danke ich für die photokatalytischen Vorversuche und Hilfestellungen bei der Handhabung der GC-Apparatur. Bei Herrn M. Schaub möchte ich mich besonders für die gute Zusammenarbeit bei den DLS-Untersuchungen bedanken. Zudem möchte ich speziell Herrn N. Rockstroh, Frau T. Makarowa sowie K. Peuntinger und K. Tenbrink für das ausführliche Korrekturlesen danken. Den Arbeisgruppen von Prof. Dr. U. S. Schubert bzw. PD. Dr. M. Gottschaldt aus Jena und von Prof. Dr. S. Yano aus Kyoto danke ich für die Ermöglichung des zweimonatigen Japanaufenthalts am Katsura Campus der Kyoto University. Zudem danke ich besonders meinen Kollegen Dr. H. Ohi und K. Babiuch für die erlebnisreiche Zeit dort. Weiterhin gilt mein Dank all meinen Labor- und Teamkollegen, im Einzelnen den Herren Dr. M. Schwalbe, Dr. M. Auth, Dr. M. Karnahl und Dr. S. Losse aus Jena sowie meinen neuen Teamkollegen aus Erlangen, den Damen K. Monczak, E. T. Kastl, S. Zheng, J. Schneider, D. Kramer, E. Kowalska und den Herren Dr. C. Koch, N. Rockstroh, R. Staehle, M. Pfeffer, M. Schaub, C. Pehlken für den stets anregenden fachlichen und nicht-fachlichen Gedankenaustausch. Besonderer Dank gilt meinen Praktikantinnen R. Messerer, L. Mbogo-Wachira und K. Ritter die unterstützende Versuche zum Bisphenanthrolinthema sowie zum Imidazophenanthrolinthema durchgeführt haben. Insbesondere danke ich Michael Bessel und Kevin Stippich sowie allen weiteren Freunden und Kommilitonen, die mich über die Jahre so hilfreich unterstützt haben. Ausdrücklich möchte ich mich bei meinen guten Freunden Kay Neumann, German Klink, Jörg Wiesehügel, Robert Staehle und Raquel Knickenberg bedanken, die mir mit vielen geselligen Stunden und angenehmen Unterhaltungen dabei geholfen haben, den Kopf wieder frei zu bekommen und Probleme von einem anderen Blickpunkt aus betrachten zu können. Zum Schluss möchte ich mich besonders herzlich bei meinen Eltern und meiner Familie und meiner Freundin Katharina für ihre tatkräftige Unterstützung und speziell für ihren Zuspruch und ihre Ermutigungen bedanken, die mir stets ein großer Ansporn waren. »And Lord, we are especially thankful for nuclear power, the cleanest, safest energy source there is. Except for solar, which is just a pipe dream.« -Homer Simpson[1] Contents 1 Introduction 1 1.1 Fossil Fuels and Nuclear Power ................................ 2 1.2 Renewable Fuels ........................................ 5 1.3 Energy Transformation and Storage ............................. 6 1.4 Solar Energy Conversion .................................... 8 1.5 Photosynthesis ......................................... 10 1.6 Photocatalyzed Reactions ................................... 13 1.7 Mimicking Photosynthesis .................................. 17 1.8 Formalisms of Photocatalytic Systems ........................... 19 1.9 Multicomponent Systems from Fundamental Building Blocks ............. 21 1.9.1 Photosensitizers - Light Energy Conversion .................... 23 1.9.2 Redox Systems for Charge Separation ....................... 29 1.9.3 Oxidation Catalysts - Solar Fuels .......................... 34 1.9.4 Reduction Catalysts - Solar Fuels .......................... 37 1.10 Intramolecular Photoredoxcatalysts ............................ 40 1.10.1 Oligonuclear Coordination Compounds ..................... 42 1.10.2 State of the Art Systems ............................... 46 1.10.3 Drawbacks and Starting Points ........................... 49 2 Scope of the Thesis 52 3 General Section 54 3.1 Brominated Phenanthrolines - A Gate to new Bridging Ligands ............ 54 3.1.1 Selective Bromination of Phenanthrolines .................... 57 3.1.2 Ruthenium Complexes with Brominated Phenanthrolines ........... 63 3.1.3 Structural Analysis .................................. 69 3.1.4 Photophysical Behavior ............................... 71 3.1.5 Emission Decay Dynamics .............................. 76 3.1.6 Electrochemical Characterization ......................... 78 |Contents| 3.1.7 Concluding Remarks to phenBr-Ligands ..................... 82 3.2 Bisphenanthroline: A Suitable Molecular Bridge? ..................... 83 3.2.1 Preparation of phenphen and Related Complexes ............... 85 3.2.2 Identification and Characterization ........................ 87 3.2.3 Structural Analysis .................................. 94 3.2.4 Photophysical Behavior ............................... 97 3.2.5 Excited State Dynamics ............................... 99 3.2.6 Electrochemical Characterization ......................... 104 3.2.7 Application in Light Driven Catalysis ....................... 106 3.2.8 Concluding Remarks on phenphen-Bridged Complexes ............ 108 3.3 NN-NHC-Ligand bbip: Toward Second Generation Catalysts .............. 110 3.3.1 NHCs and NHC Complexes ............................. 111 3.3.2 Imidazophenanthrolines: Toward Redox Stable Bridges ............ 115 3.3.3 Structural Characterization of ip-Type Ligands ................. 118 3.3.4 N,N’-Coordinated ip-Type Complexes ....................... 122 3.3.5 NHC-Coordinated ip-Type Complexes ....................... 124 3.3.6 Structural Characterization of Ruthenium ip-Type Complexes ........ 130 3.3.7 Preparation of bbip-Bridged Catalysts ...................... 134 3.3.8 Spectroscopic Characterization .......................... 138 3.3.9 Excited State Dynamics of the bbip-Containing Ruthenium Complexes ... 145 3.3.10 Electrochemical Characterization ......................... 148 3.3.11 Application in Catalysis: Prove of Concept .................... 151 3.4 Outlook, Exploratory Investigations and Perspectives .................. 159 3.4.1 Manipulations, Involving the bbip-System .................... 159 3.4.2 Electron Deficient bbip-Systems .......................... 161 3.4.3 NHC-Ligand edip: Further Development of Improved Catalysts ....... 164 3.4.4 Concluding Remarks ................................. 173 4 Summary 174 5 Zusammenfassung 183 |ii| |Contents| 6 Experimental Section 193 6.1 Synthesis of the Organic Ligands ............................... 197 6.1.1 Bromination of Phenanthrolines - method
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