Investigations of Mixed-Valence and Open-Shell Transition-Metal Complexes Employing Modern Density Functional Methods vorgelegt von Diplom-Chemiker Matthias Parthey aus Bad Soden-Salmünster Von der Fakultät II – Mathematik und Naturwissenschaften der Technischen Universität Berlin zur Erlangung des akademischen Grades Doktor der Naturwissenschaften – Dr. rer. nat. – genehmigte Dissertation Promotionsausschuss: Vorsitzender: Prof. Dr. rer. nat. Arne Thomas Berichter: Prof. Dr. rer. nat. Martin Kaupp Berichter: Prof. Dr. phil. nat. Wolfgang Kaim Tag der wissenschaftlichen Aussprache: 16.04.2014 Berlin 2014 D83 “No one ever achieved greatness by playing it safe“ Harry J. Gray Für Hami “Wir werden selber reich, wenn wir Freude schenken“ Brigitte Theilen ACKNOWLEDGEMENT “It is personalities, not principles, that move the age.” Oscar Wilde First, I want to thank Prof. Martin Kaupp. Martin, words can barely express how grateful I am for the three years of my PhD and the ideas we created and developed together during that time. But not only your support in science but also all the socializing activities like football, skiing, and of course our TV appearance made my PhD an incredibly enjoyable time. I thank Manuel Renz, for introducing me to quantum chemistry, always giving extremely helpful advice, and sticking with me (and my Mac) through more than two years in the office; Anja Greif, my light on gray office days with her dog Sari being my kryptonite, when it comes to working efficiently; Johannes Schraut, amazing football mate, both active and watching; Florian Meier, for being too nice for this world; Hilke Bahmann, coding and social organizing queen; Martin Enke, football and Facebook expert; Toni Maier for filling Manuel’s spot; Kolja Theilacker, Robert Müller, Vladimir Pelmentschikov, Sebastian Gohr, Sascha Klawohn, and the whole Kaupp group for always helping and supporting me. “I left home, but there is one thing that I still know: it’s always summer in my heart and in my soul!” Ryan Key of Yellowcard in “Always Summer” From Durham University, now partly University of Western Australia at Perth, I want to thank the P. J. Low group. Most of all of course Prof. Paul J. Low for all the great work we did together and even more the fun we had while doing it. Sorry for drinking so much coffee and stealing your words for this acknowledgement, Paul! Thanks to my lab mates: Josef Gluyas, the synthetic grandmaster and my English proofreader; Sören Bock, best football and dart partner ever and worst German DJ; “real” thanks to Sam Eaves; Kevin Vincent for the fresh air breaks; Santiago Marquez-Gonzales for his positive attitude; Ross Davidson, the Doughnut provider; Campbell Mackenzie, Marie-Christine Oerthel, and the rest of the group. I also want to thank Prof. Dave J. Tozer and Dr. Mark A. Fox for the quantum-chemical discussions. In this context I also want to thank Prof. D. J. Tozer, Prof. Trygve Helgaker, Dr. Enrico Benassi, and Dr. Christoph Jacob for their excellent lectures, talks, and/or discussion about general concepts and special issues of DFT and quantum-chemistry. Representatively for all people at the TU Berlin, who supported me, I want to thank: Heidi Grauel and Nadine Rechenberger for helping with the enormous amount of formal work, especially the countless forms for business trips, and the organization of group activities and the homepage; Prof. Christian Limberg, my second supervisor; Dr. Jean-Philippe Lonjaret, the head and heart of the BIG-NSE graduate school; Dr. Norbert Paschedag and Sven Grottke for their IT support; the Schoen group, especially Michael Melle, Tillman Stieger, and Marco Mazza, for being valuable targets for scientific slamming. The same holds true for Jean- Christophe Tremblay from the FU Berlin. “They say ‘You don’t grow up, you just grow old’, it seems to say I haven’t done both, I made mistakes, I know, I know, but here I am alive!” Ryan Key of Yellowcard in “Here I Am Alive” I also want to thank my family: My parents, Almuth and Roland, for their endless support, life advice, and that they never pushed me towards any direction; my sister Johanna, my role model when it comes to being persistent, strong, and faithful and thus succeeding in the end; my brother Christian for always helping me with physics, being even more Apple addicted, and for losing the clash of science by working for a chemical company; my grandma Erika “Hami” Goralewski, Godehard and Siegrid Goralewski, my uncle and aunt, and my “uncle” Heinz Löken for their support. I also thank Werner and Christa Parthey, Erika and Josef Jöckel, and Ulrike Selig-Parthey. “That’s what friends are for. They help you to be more of who you are.” Christopher Robin (Disney character) There are a lot of friends I met during different stages of my life, who mainly made my free time enjoyable, every place feel like home, and prevented me from getting to caught up in research, but also gave advice in scientific matters, and thus I want to thank: From Hessen: Augustin Danciu, for broing and awesoming all over the place; Patrick Noll, best wing man (= Goose) ever, proud to be your best man; Sebastian Dietz, oldest friend and like wine our friendship improves with age; Jana Noll, for always being a great observer and of course the famous carnival lasagna; Markus Auhl, hessian philosopher; Natascha Klumpp, forever Troy; Christopher Hämel, doubles partner for life; Andreas Möller, for all the travels and career advice; Theresa and Horst Schmidt, Elke Thesenvitz, Susan Simon, Nina Wallenta, Natalie Alt, Antonia Spielmann, Thomas Hummel, Philipp Roth, Steffen Pfeifer, Till Bergen, and Uta Krammenschneider. From Würzburg: Frank Brunecker, Steffen Kalinna, Marius Silaghi, Klaus Dück, Johannes Landmann, Alexander Mertsch, and Martin Kess, for making even the hard times enjoyable during my studies in Würzburg. I hope, our Christmas market tradition will continue. A special thanks to Jost Henkel for following or inviting me to all different spots like London, Durham, Berlin, Hannover, … (hopefully this list will continue) From Berlin: My BIG-NSE (Berlin International Graduate School of Natural Science and Engineering) mates Fanni Daruny Sypaseuth, Laura Vieweg, Moritz Baar, Daniel Gallego, Patrick Littlewood, Genwen Tan, Hong Nhan Nong, Jiao Linyu, Setareh Sadjadi, Xunhua Zhao, Heiner Schwarz, Swantje Wiebalck, Xenia Erler, Subhamoy Bhattacharya, María Gracia Colmenares, Inéz Monte Pérez, Laura Pardo Pérez, and all the other nice people from the school. Jakub Stejskal, Igor Anatzki, Marcus Beyerlein, Andreas Podlasly, André Zacher, Benjamin Mietling, Sven Vangermain, Kristen Van Dernoot, and the rest from the Grün-Gold Pankow tennis team. From Durham: Matt Perks, César Segura, Charlie Rozier, Ash Routen, James Koranyi, and the Staff football team. Thanks to the team of the New Inn. I want to thank Reinhold Stein, my former chemistry teacher, for introducing me to chemistry and almost more importantly to Top Gun “It takes a lot more than just fancy flying”. For financial support and the opportunity to work in an exceptional research environment I want to thank the “Unifying Concepts of Catalysis” (UniCat) excellence cluster and the German Academic Exchange Service (DAAD). “I hope you live a life you are proud of; if you are not, I hope you find the strength to start all over again” F. Scott Fitzgerald I ABSTRACT ABSTRACT Mixed-valence multinuclear transition-metal complexes have been in the focus of research since the discovery of the Creutz-Taube ion and related systems in the 1960s. The search for functional (opto-) electronic materials on the molecular scale, such as molecular wires and transistors, has added to the momentum of the field. Successful applications of organic mixed-valence systems as charge carriers - for example in organic light-emitting diodes or dye-sensitized solar cells - are known. Mixed-valence transition-metal complexes are even more versatile in their electronic properties due to the availability of d-orbitals. Hence they are appealing targets for the design of functional materials and additionally of central importance in electron transfer processes in nature - e.g. in metalloenzymes - and in catalysis. A central question in all of these fields is that of the localization of charge on a given redox center (end-cap or bridging ligand) versus delocalization over the molecular framework. In the important model case of two redox centers linked by a bridging ligand, the description of electronic structure is usually made within the Robin-Day scheme, which is based on the extent of electronic coupling. The investigation of the electronic structure is complicated by the lack of information directly extractable from experimental data. Especially challenging is the presence of overlapping absorption bands in UV-vis-NIR spectra and the speculated existence of different thermally accessible conformers. Hence a reliable investigation of the extent of electronic coupling is only possible via combined experimental and quantum- chemical studies. The failure of Hartree-Fock and Density Functional Theory - the methods feasible for the system-size of typical mixed-valence systems - in describing the charge localization/delocalization behavior has been overcome in the well balanced global hybrid functional BLYP35, which is employed in combination with solvent models. In this thesis it is shown that the BLYP35/solvent model combination is furthermore capable of describing optoelectronic properties of mixed-valence transition-metal complexes. Even the challenging charge-transfer excitations are reliably reproduced. In addition the long- standing question to which extent the conformation determines the electronic and spectroscopic properties of mixed-valence systems is investigated. Calculations yield rotational motion as explanation for the optical properties of polyynediyl complexes. This prediction is experimentally proven by the Low group. For diethynylphenyl-bridged ruthenium complexes the computations demonstrate that conformational motion may even average to some extent localized and delocalized electronic and molecular structures.