Iridium(III)bis[2-(4,6-difluorophenyl)pyridyl-N,C2′]picolinate (FIrpic) is a widely used light-blue phosphorescent
material
known for its favorable redox activity. However, the operational lifetime
of FIrpic-based phosphorescent organic light-emitting diodes (PhOLEDs)
remains unsatisfactory. To gain a deeper understanding of the chemical
stability of FIrpic in various redox states, we explored its degradation
mechanisms in the ground (S
0), one-electron
oxidized (Ox.), and one-electron reduced (Re.) states using theoretical
methods. Density functional theory (DFT) static calculations, combined
with atomic center density matrix propagation (ADMP) simulations at
temperatures of 500, 600, and 700 K, revealed that the cleavage of
the Ir–N1 bond is a crucial step in the chemical
degradation process of FIrpic in both the ground and redox states.
This bond breakage leads to a nonemissive five-coordinated trigonal
bipyramidal intermediate. The degradation process is notably more
facile in the redox states, particularly in the Re. Charge analysis indicates a decreasing trend in electronic delocalization
between the LPN electron donor natural bond orbital (NBO)
and the d*N–Ir(pic.) electron acceptor NBO, with
the order S0 > Ox. > Re. Our findings provide a deeper
insight into the degradation mechanisms of FIrpic under different
redox conditions. This understanding is crucial for the design of
more stable materials in FIrpic-based PhOLEDs.