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

Depicted inthe TOC are the experimental transient spectradepicting the different excited states, the Jablonski diagram summarizingthe excited state reactivity difference, and natural transition orbitalsdepicting the electronic changes leading to the transient spectra. A series of four lanthanide thenoyltrifluoroacetone (TTA)complexesconsisting of two f(0) (La3+ and Ce4+) and two f(1) (Ce3+) complexes was examinedusing steady-state and time-resolved spectroscopic techniques. Thewide range of spectroscopic techniques presented herein have enabledus to discern the nature of the excited states (charge transfer, CTvs ligand localized, LL) as well as construct a Jablonski diagramfor detailing the excited state reactivity within the series of molecules.The wavelength and excitation power dependence for these series ofcomplexes are the first direct verification for the presence of simultaneouscompeting, noninteracting CT and LL excited states. Additionally,a computational framework is described that can be used to supportspectroscopic assignments as a guide for future studies. Finally,the relationship between the obtained photophysics and possible photochemicalseparation mechanisms is described.