Séminaire LCPQ
Salle de séminaire IRSAMC
Many light-induced molecular processes involve a change in spin state and are formally forbidden in non-relativistic quantum theory. To make them happen, spin–orbit coupling (SOC) has to be invoked. Intersystem crossing (ISC), the nonradiative transition between two electronic states of different multiplicity, plays a key role in photochemistry and photophysics with a broad range of applications including molecular photonics, biological photosensors, photodynamic therapy, and materials science. Quantum chemistry has become a valuable tool for gaining detailed insight into the mechanisms of ISC beyond qualitative rules.[1]
The combined density functional and configuration interaction method (DFT/MRCI)[2] is used to compute high-quality electronic excitation spectra and electronic wave functions. Environment effects are taken into account by explicit solvent molecules and COSMO[3]. ISC rates are determined in the framework of the Fermi Golden Rule approach with electronic SOC matrix elements calculated using SPOCK[4] while vibrational contributions to ISC rates are obtained using time-independent[5] as well as time-dependent approaches[6].
By means of these methods, the electronic spectra and spin-orbit coupling of a variety of organic chromophores have been investigated. In this talk I would like to present our approach and the results on a few typical cases.
Literature :
[1] C. M. Marian, in : WIREs Computational Molecular Science, Computational
Chemistry, Wiley Online Library 2011.
[2] S. Grimme, M. Waletzke, J. Chem. Phys. 1999, 111, 5645.
[3] J. Klamt and G. Schüürmann, J. Chem. Soc., Perkin Trans. 1993, 2, 799.
[4] M. Kleinschmidt, J. Tatchen, C.M. Marian, J. Comp. Chem. 2002, 23, 824.
[5] J. Tatchen, N. Gilka, C. M. Marian, Phys. Chem. Chem. Phys. 2007, 9, 5209.
[6] M. Etinski, J. Tatchen, C. M. Marian, J. Chem. Phys. 2011, 134, 154105.