Research Topics

Photosynthesis

Photosynthetic organisms capture the energy of sunlight and convert it into chemical energy by synthesizing carbohydrates, a process that sustains all life on Earth. Photosynthesis has been a major research topic in our group since its establishment. We use originally developed methodologies of computational spectroscopy as well as multiscale simulations to uncover the molecular mechanisms of photosynthesis in nature as a fundamental step towards developing artificial photosynthetic systems for sustainable production of solar fuels.

Our work has shaped the development of the field by generating foundational concepts for the description of metallocofactor plasticity and using them to uncover the mechanistic principles of biological water oxidation. Moreover, advanced multilevel simulations are redefining our understanding of the very first steps in the conversion of sunlight to electron flow by photosynthetic pigments and pigment-protein assemblies. Current research projects in our group cover all enzymes involved in light-dependent and light-independent reactions of photosynthesis, ranging from biosynthetic pathways to carbon fixation. Our ultimate goal is the complete description of photosynthesis as a fully resolved network of processes at the quantum mechanical level, forming the basis for control, design, and evolution of new functionality.

Quantum Biochemistry and Quantum Biology

Beyond photosynthesis, we study multiple other enzymes, their properties, and their reactivity using advanced quantum chemical techniques in combination with molecular dynamics simulations. We are especially focusing on various metalloenzymes, which harbor transition metals able to catalyze some of the most challenging and fascinating chemical transformations in nature. An important component of our research in this area involves methods for the prediction of spectroscopic observables such as those derived from magnetic resonance and X-ray spectroscopies. Spin in biology is a topic of particular interest. We have strong expertise in developing and applying methods and protocols for dealing with spin-related problems, while current efforts aim at developing new ways of analyzing and understanding the quantum nature of crucial biological systems and processes.

Transition Metal Chemistry

Unique electronic, magnetic, spectroscopic, and chemical properties arise in molecules with unpaired electrons, particularly when two or more transition metal ions with unpaired electrons interact with each other. Our group has extensive experience in dealing with the electronic structure and spectroscopy of open-shell and exchange-coupled systems using a wide array of theoretical approaches and computational methodologies, from single-reference to various multi-reference approaches. A guiding principle for us is to obtain useful and actionable insights for molecular systems of realistic size and practical relevance. The ability to correctly describe the electronic structure of magnetically coupled systems is essential in the study of not only the biological oxygen-evolving complex and other enzyme metallocofactors, but also of single-molecule magnets, main-group radicals and polyradicals, catalytic metal oxide surfaces, and qubits.

Methodological Developments

Computational Spectroscopy

A major activity in our group is the development and refinement of theoretical methods and protocols for the calculation of spectroscopic parameters, especially for transition metals and the uniquely challenging case of systems that contain several sites with unpaired electrons. These methods are key for interpreting complex experimental data and for devising models that explain the structure and function of inorganic and bioinorganic catalysts. Examples include a spin-projection method developed to calculate hyperfine coupling constants for oligonuclear metal clusters of arbitrary shape and nuclearity, a way to compute local zero-field splitting parameters in polynuclear clusters, protocols for spin-state energetics, EPR and Mössbauer parameters of transition metal complexes, as well as various refinements of methodologies for excited states of pigments and pigment assemblies.

All-Electron Basis Sets

Computational investigations of chemical systems containing heavy elements often employ effective core potentials, but these can have limitations or be inapplicable in combinatino with some theoretical methods or for the calculation of certain molecular properties. For this reason, it is necessary to have reliable all-electron basis sets that allow efficient calculations with the popular scalar relativistic Hamiltonians, such as the exact 2-component (X2C), the Douglas-Kroll-Hess (DKH), and the zeroth order regular approximation (ZORA). We have been developing the family of Segmented All-electron Relativistically Contracted (SARC) basis sets, which are optimized for all of the above Hamiltonians. The SARC basis sets offer a very good balance of size and flexibility, making them a solid choice for routine computational studies of large molecules containing heavy elements, and at the same time sufficiently reliable for direct use in calculations of demanding spectroscopic properties such as EPR parameters. Their performance has been extensively tested and they have been used in thousands of applications, making them one of the most popular choices for all-electron relativistic calculations.