Theoretical Bio-Inorganic Chemistry and Coordination Chemistry
Transition metal complexes enable the most interesting chemical transformations. These capabilities are intimately connected to delicate electronic structures, which represent a profound challenge to theoretical chemistry. A paradigm in this field is the reliable despription of spin-state energetics to which we have contributed the insight that the admixture of exact exchange is the most crucial part in approximate density functionals. Apart from the search for reliable electronic structure methods, we also work on conceptual tools to interpret the first-principles data obtained.
For reviews see:
M. Reiher, A Theoretical Challenge: Transition-Metal Compounds (PDF, 151 KB), Chimia, 2009, 63, 140-145.
M. Podewitz, M. Reiher, Spin Interactions in Cluster Chemistry, Adv. Inorg. Chem., 2010, 62, 177-230
As an important example of our research in the field of coordination-chemistry, we refer to our studies on nitrogen fixation. Solving the problem of nitrogen fixation under ambient conditions by a synthetic catalyst is still a major challenge in chemistry. Accomplished in nature by the enzyme nitrogenase, the best industrial solution is the Haber-Bosch process working at elevated temperature and pressure. Our efforts concentrate on determining the theoretical requirements for the development of synthetic homogeneous catalysis under ambient conditions. A milestone achieved in our group was the complete theoretical characterization of the nitrogen-fixation mechanism at the catalyst discovered by Schrock.
For reviews see:
M. Reiher, B. A. Hess, Quantum chemical investigations into the problem of biological nitrogen fixation: Sellmann-type metal-sulfur model complexes, Adv. Inorg. Chem., 2004, 56, 55-100
H.-J. Himmel, M. Reiher, Intrinsic dinitrogen activation at bare metal atoms, Angew. Chem. Int. Ed. Engl., 2006, 45, 6264-6288
The intricate coordination environments of metalloenzymes are a particular challenge to us. One example investigated by us are hydrogenases. These are enzymes that transform molecular hydrogen. Three different classes are known. We have proposed the concept of swapped ligand spheres to highlight the structural and electronic similarity of Hmd and [FeFe] hydrogenases which, at first glance, seemed to be structurally very different enzymes. If these enzymes are to be used for the production of clean energy, their sensitivity towards molecular oxygen will be a major obstacle that must be overcome. Our contribution to the solution of this problem was to investigate oxygen inhibition at the active site. We contributed to the mechanistic understanding of the regular mechanism and of oxgen interference with multiscale modeling.
M. T. Stiebritz, M. Reiher, Hydrogenases and Oxygen (PDF, 599 KB), Chem. Sci., 2012, 3, 1739-1751.
M. Podewitz, M. T. Stiebritz, M. Reiher, An enquiry into theoretical bioinorganic chemistry: How heuristic is the character of present-day quantum chemical methods? (PDF, 491 KB), Faraday Discus. 148 2011, 119-135.
See also the talk on Theoretical Insights into Mechanistic Aspects of Hydrogenases (PDF, 18.2 MB) by Markus Reiher from August 2015