Chemical reactivity of radicals:
In order to study properties and reactivity of radicals and polyradicals we use various theoretical methods like molecular dynamics, DFT and CASSCF. In collaboration with SREP team (ICR), molecular dynamics is used to design new polarizing agents in Dynamic Nuclear Polarization (DNP) and to study host-guest interactions in bis-nitroxide@cucurbituril complexes. We apply quantum methods in the field of radical polymer chemistry: design of new safe polymerization initiators, of new functionalization agents of polycondensates, etc… Collaborations with CROPS and CRAB teams of ICR, E. Beyou (University Lyon 1), J.J. Robin (University Montpellier 2), Arkema.
The computation and analysis of magnetic properties (g-tensor, hyperfine couplings, magnetic exchange) characterizing organic and inorganic radical molecules is one of our main research lines. To match the gap between experiment and theory, we have developed a model based on QM calculations coupled to MD simulations able to accurately calculate the magnetic properties of nitroxide spin adducts. Improved nitroxide hyperfine coupling constants have been calculated by applying the First Order Breathing Orbital SCF approach. Using the Local SCF approach which allows to freeze orbitals selectively, we have recently developed a decomposition analysis of the magnetic exchange interaction in biradicals. Collaborations with N. Guihéry, J.-P. Malrieu (Université Toulouse III, France), B. Le Guennic (Université Rennes 1, France), C. Angeli (Università di Ferrara, Italy).
Excited state reactivity:
We develop and apply theoretical models to understand the spectroscopic and photochemical properties of small molecules, molecular aggregates, molecules in condensed phase, proteins, etc. Our methodology development is varied, and ranges from electronic structure (time-dependent density functional theory and quantum mechanics/molecular mechanics approaches), the development of model Hamiltonians and vibrational analysis of excited states, and quantum dynamical methods (both semi-classical surface hopping dynamics and full quantum wavepacket dynamics). These developments are distributed in available packages like Molcas and Newton-X. We apply our newly developed methodology to study all sorts of excited state processes in various systems such as internal conversion, intersystem crossing, electron energy transfer, internal vibrational reorganization. Some representative collaborations are with M. Olivucci (University of Siena, Italy and Bowling Green State University, USA), I. Burghardt (Goethe University Frankfurt, Germany) and Hans Lischka (Tianjin University, China).
- Macromolecules:We develop and use various methods (from QM to Coarse-Grain MD) to simulate macromolecules and large-size systems. The properties of these systems characteristically span large time and length scales that are difficult to catch with only one simulation technique. Efforts are made on the numerical treatment of classical molecular dynamics in order to increase its efficiency without loosing acuracy. This allows us to treat larger system or perform longer runs for the same computational cost than mainstream techniques. Applications primarily focus on polymers obtained through radical processes, or on large systems containing radicals, but also extend to proteins. Collaborations with V. Monteil (CPE Lyon, France) and I. Fukuda (Osaka University, Japan).