Exploring Differences in Lanthanide Excited State Reactivity Using a Simple Example: The Photophysics of La and Ce Thenoyltrifluoroacetone Complexes

A series of four lanthanide thenoyltrifluoroacetone (TTA)
complexes
consisting of two f0 (La3+ and Ce4+) and two f1 (Ce3+) complexes was examined
using steady-state and time-resolved spectroscopic techniques. The
wide range of spectroscopic techniques presented herein have enabled
us to discern the nature of the excited states (charge transfer, CT
vs ligand localized, LL) as well as construct a Jablonski diagram
for detailing the excited state reactivity within the series of molecules.
The wavelength and excitation power dependence for these series of
complexes are the first direct verification for the presence of simultaneous
competing, noninteracting CT and LL excited states. Additionally,
a computational framework is described that can be used to support
spectroscopic assignments as a guide for future studies. Finally,
the relationship between the obtained photophysics and possible photochemical
separation mechanisms is described.