Ab initio calculations of chiroptical properties for lanthanide complexes

Overview & Synopsis

Lanthanide ions have a very specific spectroscopy. Their absorption and luminescence narrow bands are due to electric dipole forbidden but magnetic dipole allowed transitions. When placed in a chiral environment, trivalent lanthanide ions show strong circular dichroism and circularly polarised luminescence signals. The aim of this thesis was to develop a methodology able to simulate these properties and thus gain insight into the photophysics of the phenomena. Nevertheless, lanthanide-based systems are challenging for computational chemistry due to the presence of degenerate electronic states with multi-configurational character and the importance of spin-orbit coupling. CASSCF and related approaches have been used with self-developed post-processing programs to generate the physical parameters and spectra. The key influence of temperature and the geometry of the complexes is highlighted, while the sensitisation effect and static and dynamic coupling mechanisms are explored. The computational protocols have been thoroughly investigated, including a look at the gauge dependence present in this type of simulation. Lastly, a third chiroptical phenomenon called magneto-chiral dichroism has also been studied, leading to a focus on the magnetic properties of such complexes as well.