Fig. 4. (A) Spectroscopic characterization of the luminescent SMM proposed in this study. Solid state absorption spectrum (cyan), excitation spectrum recorded monitoring the emission at 978 nm (blue) and emission spectra in the visible (green) and NIR (orange) range recorded exciting at 390 nm. In the inset: photoluminescence kinetics (orange) recorded exciting the system at 372 nm and monitoring the emission at 978 nm, along with its mono-exponential fit (dashed black line). The solid black line is the laser signal. (B) Energy level scheme with the main transitions observed in the system (same colour code as (A)) and proposed Yb^III sensitization mechanisms. The Stark sublevels are sketched according to the results of ab initio calculations and are correlated to the transitions observed in the emission spectrum of the complex recorded at 77 K under 375 nm excitation.