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Sparta M.,Max Planck Institute for Chemical Energy Conversion | Neese F.,Max Planck Institute for Chemical Energy Conversion
Chemical Society Reviews | Year: 2014

The scope of this review is to provide a brief overview of the chemical applications carried out by local pair natural orbital coupled-electron pair and coupled-cluster methods. Benchmark tests reveal that these methods reproduce, with excellent accuracy, their canonical counterparts. At the same time, the speed up achieved by exploiting the locality of the electron correlation permits us to tackle chemical systems that, due to their size, would normally only be addressable with density functional theory. This review covers a broad variety of the chemical applications e.g. simulation of transition metal catalyzed reactions, estimation of weak interactions, and calculation of lattice properties in molecular crystals. This demonstrates that modern implementations of wavefunction-based correlated methods are playing an increasingly important role in applied computational chemistry. This journal is © the Partner Organisations 2014.

Lubitz W.,Max Planck Institute for Chemical Energy Conversion | Ogata H.,Max Planck Institute for Chemical Energy Conversion | Rudiger O.,Max Planck Institute for Chemical Energy Conversion | Reijerse E.,Max Planck Institute for Chemical Energy Conversion
Chemical Reviews | Year: 2014

Hydrogenases are a diverse group of metalloenzymes that catalyze one of the simplest molecular reactions, the conversion of dihydrogen into protons and electrons and the reverse reaction, the generation of dihydrogen. The reaction takes place at a specialized metal center that dramatically increases the acidity of H2 and leads to a heterolytic splitting of the molecule which is strongly accelerated by the presence of a nearby base. Hydrogenases are widespread in nature; they occur in bacteria, archaea, and some eukarya and can be classified according to the metal ion composition of their active sites in [NiFe], [FeFe], and [Fe] hydrogenases. The use of hydrogenase or hydrogenase models as catalysts (to replace Pt) in fuel cells or in electrolytic H 2 production will depend strongly on new concepts how to overcome the O2 sensitivity of many hydrogenases. It is to be hoped that the great progress made in the understanding of O2 tolerance in [NiFe] hydrogenases and in the artificial maturation of the [FeFe] hydrogenases.

Sharma S.,Princeton University | Sivalingam K.,Max Planck Institute for Chemical Energy Conversion | Neese F.,Max Planck Institute for Chemical Energy Conversion | Chan G.K.-L.,Princeton University
Nature Chemistry | Year: 2014

Iron-sulfur clusters are a universal biological motif. They carry out electron transfer, redox chemistry and even oxygen sensing, in diverse processes including nitrogen fixation, respiration and photosynthesis. Their low-lying electronic states are key to their remarkable reactivity, but they cannot be directly observed. Here, we present the first ever quantum calculation of the electronic levels of [2Fe-2S] and [4Fe-4S] clusters free from any model assumptions. Our results highlight the limitations of long-standing models of their electronic structure. In particular, we demonstrate that the widely used Heisenberg double exchange model underestimates the number of states by one to two orders of magnitude, which can conclusively be traced to the absence of Fe dd excitations, thought to be important in these clusters. Furthermore, the electronic energy levels of even the same spin are dense on the scale of vibrational fluctuations and this provides a natural explanation for the ubiquity of these clusters in catalysis in nature. © 2014 Macmillan Publishers Limited. All rights reserved.

Cox N.,Max Planck Institute for Chemical Energy Conversion | Pantazis D.A.,Max Planck Institute for Chemical Energy Conversion | Neese F.,Max Planck Institute for Chemical Energy Conversion | Lubitz W.,Max Planck Institute for Chemical Energy Conversion
Accounts of Chemical Research | Year: 2013

Photosystem II (PSII), a multisubunit pigment-protein supercomplex found in cyanobacteria, algae, and plants, catalyzes a unique reaction in nature: the light-driven oxidation of water. Remarkable recent advances in the structural analysis of PSII now give a detailed picture of the static supercomplex on the molecular level. These data provide a solid foundation for future functional studies, in particular the mechanism of water oxidation and oxygen release.The catalytic core of the PSII is a tetramanganese-calcium cluster (Mn 4O5Ca), commonly referred to as the oxygen-evolving complex (OEC). The function of the OEC rests on its ability to cycle through five metastable states (Si, i = 0-4), transiently storing four oxidizing equivalents, and in so doing, facilitates the four electron water splitting reaction. While the latest crystallographic model of PSII gives an atomic picture of the OEC, the exact connectivity within the inorganic core and the S-state(s) that the X-ray model represents remain uncertain.In this Account, we describe our joint experimental and theoretical efforts to eliminate these ambiguities by combining the X-ray data with spectroscopic constraints and introducing computational modeling. We are developing quantum chemical methods to predict electron paramagnetic resonance (EPR) parameters for transition metal clusters, especially focusing on spin-projection approaches combined with density functional theory (DFT) calculations. We aim to resolve the geometric and electronic structures of all S-states, correlating their structural features with spectroscopic observations to elucidate reactivity. The sequence of manganese oxidations and concomitant charge compensation events via proton transfer allow us to rationalize the multielectron S-state cycle. EPR spectroscopy combined with theoretical calculations provides a unique window into the tetramangenese complex, in particular its protonation states and metal ligand sphere evolution, far beyond the scope of static techniques such as X-ray crystallography. This approach has led, for example, to a detailed understanding of the EPR signals in the S2-state of the OEC in terms of two interconvertible, isoenergetic structures. These two structures differ in their valence distribution and spin multiplicity, which has important consequences for substrate binding and may explain its low barrier exchange with solvent water.New experimental techniques and innovative sample preparations are beginning to unravel the complex sequence of substrate uptake/inclusion, which is coupled to proton release. The introduction of specific site perturbations, such as replacing Ca2+ with Sr2+, provides discrete information about the ligand environment of the individual Mn ions. In this way, we have identified a potential open coordination site for one Mn center, which may serve as a substrate binding site in the higher S-states, such as S3 and S4. In addition, we can now monitor the binding of the substrate water in the lower S-states (S1 and S2) using new EPR-detected NMR spectroscopies. These studies provided the first evidence that one of the substrates is subsumed into the complex itself and forms an oxo-bridge between two Mn ions. This result places important new restrictions on the mechanism of O-O bond formation. These new insights from nature's water splitting catalyst provide important criteria for the rational design of bioinspired synthetic catalysts. © 2013 American Chemical Society.

Schlogl R.,Fritz Haber Institute of the Max Planck Society | Schlogl R.,Max Planck Institute for Chemical Energy Conversion
Angewandte Chemie - International Edition | Year: 2015

A heterogeneous catalyst is a functional material that continually creates active sites with its reactants under reaction conditions. These sites change the rates of chemical reactions of the reactants localized on them without changing the thermodynamic equilibrium between the materials. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA.

Krewald V.,Max Planck Institute for Chemical Energy Conversion | Neese F.,Max Planck Institute for Chemical Energy Conversion | Pantazis D.A.,Max Planck Institute for Chemical Energy Conversion
Journal of the American Chemical Society | Year: 2013

The Mn(IV)3CaO4 cubane is a structural motif present in the oxygen-evolving complex (OEC) of photosystem II and in water-oxidizing Mn/Ca layered oxides. This work investigates the magnetic and spectroscopic properties of two recently synthesized complexes and a series of idealized models that incorporate this structural unit. Magnetic interactions, accessible spin states, and 55Mn isotropic hyperfine couplings are computed with quantum chemical methods and form the basis for structure-property correlations. Additionally, the effects of oxo-bridge protonation and one-electron reduction are examined. The calculated properties are found to be in excellent agreement with available experimental data. It is established that all synthetic and model Mn(IV)3CaO4 cubane complexes have the same high-spin S = 9/2 ground state. The magnetic coupling conditions under which different ground spin states can be accessed are determined. Substitution of Mn(IV) magnetic centers by diamagnetic ions [e.g., Ge(IV)] allows one to "switch off" specific spin sites in order to examine the magnetic orbitals along individual Mn-Mn exchange pathways, which confirms the predominance of ferromagnetic interactions within the cubane framework. The span of the Heisenberg spin ladder is found to correlate inversely with the number of protonated oxo bridges. Energetic comparisons for protonated models show that the tris-μ-oxo bridge connecting only Mn ions in the cubane has the lowest proton affinity and that the average relaxation energy per additional proton is on the order of 18 kcal·mol-1, thus making access to ground states other than the high-spin S = 9/ 2 state in these cubanes unlikely. The relevance of these cubanes for the OEC and synthetic oxides is discussed. © 2013 American Chemical Society.

Schapiro I.,Max Planck Institute for Chemical Energy Conversion | Ruhman S.,Hebrew University of Jerusalem
Biochimica et Biophysica Acta - Bioenergetics | Year: 2014

Light induced isomerization of the retinal chromophore activates biological function in all retinal protein (RP) driving processes such as ion-pumping, vertebrate vision and phototaxis in organisms as primitive as archea, or as complex as mammals. This process and its consecutive reactions have been the focus of experimental and theoretical research for decades. The aim of this review is to demonstrate how the experimental and theoretical research efforts can now be combined to reach a more comprehensive understanding of the excited state process on the molecular level. Using the Anabaena Sensory Rhodopsin as an example we will show how contemporary time-resolved spectroscopy and recently implemented excited state QM/MM methods consistently describe photochemistry in retinal proteins. This article is part of a Special Issue entitled: Retinal Proteins - You can teach an old dog new tricks. © 2013 Published by Elsevier B.V.

Cox N.,Max Planck Institute for Chemical Energy Conversion | Retegan M.,Max Planck Institute for Chemical Energy Conversion | Neese F.,Max Planck Institute for Chemical Energy Conversion | Pantazis D.A.,Max Planck Institute for Chemical Energy Conversion | And 2 more authors.
Science | Year: 2014

The photosynthetic protein complex photosystem II oxidizes water to molecular oxygen at an embedded tetramanganese-calcium cluster. Resolving the geometric and electronic structure of this cluster in its highest metastable catalytic state (designated S3) is a prerequisite for understanding the mechanism of O-O bond formation. Here, multifrequency, multidimensional magnetic resonance spectroscopy reveals that all four manganese ions of the catalyst are structurally and electronically similar immediately before the final oxygen evolution step; they all exhibit a 4+ formal oxidation state and octahedral local geometry. Only one structural model derived fromquantum chemicalmodeling is consistentwith allmagnetic resonance data; its formation requires the binding of an additional water molecule. O-O bond formation would then proceed by the coupling of two proximalmanganese-bound oxygens in the transition state of the cofactor.

Ogata H.,Max Planck Institute for Chemical Energy Conversion | Nishikawa K.,Max Planck Institute for Chemical Energy Conversion | Nishikawa K.,University of Hyogo | Lubitz W.,Max Planck Institute for Chemical Energy Conversion
Nature | Year: 2015

The enzyme hydrogenase reversibly converts dihydrogen to protons and electrons at a metal catalyst. The location of the abundant hydrogens is of key importance for understanding structure and function of the protein. However, in protein X-ray crystallography the detection of hydrogen atoms is one of the major problems, since they display only weak contributions to diffraction and the quality of the single crystals is often insufficient to obtain sub-ångström resolution. Here we report the crystal structure of a standard [NiFe] hydrogenase (∼91.3 kDa molecular mass) at 0.89 Å resolution. The strictly anoxically isolated hydrogenase has been obtained in a specific spectroscopic state, the active reduced Ni-R (subform Ni-R1) state. The high resolution, proper refinement strategy and careful modelling allow the positioning of a large part of the hydrogen atoms in the structure. This has led to the direct detection of the products of the heterolytic splitting of dihydrogen into a hydride (H-) bridging the Ni and Fe and a proton (H+) attached to the sulphur of a cysteine ligand. The Ni-H- and Fe-H- bond lengths are 1.58 Å and 1.78Å, respectively. Furthermore, we can assign the Fe-CO and Fe-CN- ligands at the active site, and can obtain the hydrogen-bond networks and the preferred proton transfer pathway in the hydrogenase. Our results demonstrate the precise comprehensive information available from ultra-high-resolution structures of proteins as an alternative to neutron diffraction and other methods such as NMR structural analysis. ©2015 Macmillan Publishers Limited. All rights reserved.

400 young scientists from 76 countries have been selected to participate in the 67th Lindau Nobel Laureate Meeting. From 25 - 30 June 2017 they will meet with Nobel Laureates at Lake Constance. This year's meeting is dedicated to chemistry. Thus far, 31 Nobel laureates have confirmed their participation. The young scientists are outstanding undergraduate students, graduate students and post-docs under the age of 35, conducting research in the field of chemistry. They have successfully passed a multi-stage international selection process. 155 scientific institutes, universities, foundations and research-oriented companies contributed to the nominations. The selected young scientists originate from big research nations like the US, the UK, Japan, Israel, and Germany, but also from developing countries such as Bangladesh, Myanmar and Benin. The proportion of women among the selected young scientists is 45 percent. "For the field of chemistry, that is a substantial number", says Wolfgang Lubitz, Director of the Max Planck Institute for Chemical Energy Conversion, Vice-President of the Council for the Lindau Nobel Laureate Meetings and scientific co-chairperson of this year's meeting. "The quality of applicants was again extremely high", says Burkhard Fricke, professor emeritus for theoretical physics and coordinator of the selection process. "Some of the young scientists who applied had very impressive CVs. It is highly unfortunate that we can only invite 400 of them." Due to the ongoing modernisation of the local conference venue, the meeting will once again take place in Lindau's city theatre. Accordingly, the usual number of just under 600 participating young scientists had to be reduced to 400. The Lindau Nobel Laureate Meetings take place every year since 1951 and are designed as a forum for exchange, networking and inspiration. In Lindau, excellent young researchers meet the most acclaimed scientists of their field. Bernard Feringa and Jean-Pierre Sauvage, who received the Nobel Prize in Chemistry 2016, together with Sir Fraser Stoddart, for the design of molecular machines, will also participate in this year's meeting. Besides molecular machines, the key topics of the 67th Lindau Nobel Laureate Meeting will include big data, climate change and the role of science in a "post-truth" era. The selected young scientists may expect a six-day programme with numerous lectures and panel discussions. Some of them will also get the opportunity to discuss their own work at one of the master classes or at the poster session. "This is a unique opportunity for the young scientists to present their research in front of an international audience and receive invaluable feedback from Nobel Laureates", says Wolfgang Lubitz. In addition to the scientific programme, the meeting offers many opportunities for the young scientists to socialise with the Nobel Laureates, and of course with each other, in a relaxed atmosphere.

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