Unveiling the Dual Emission Photo‐Deactivation Mechanism of a Neutral Heteroleptic Iridium (III) Complex

Abstract

In this article, the photo-deactivation mechanism of dual emission of a neutral iridium (III) complex is explored by using density function theory (DFT) and time-dependent density function theory (TD-DFT) calculations. To explore the phosphorescence quantum yield of the iridium (III) complex, the radiative decay constant of each emission excited state was computed by TD-DFT calculations, including spin-orbit coupling (SOC). In these calculations, factors such as the transition dipole moments, energy gaps, and SOC elements between the emission states and singlet excited states are taken into account in the evaluation of the radiative decay constants. Additionally, the non-radiative decay is revealed by considering the temperature-independent and the temperature-dependent non-radiative processes. The computational results indicate that the order of the two emission excited states can exert a significant effect on the phosphorescence quantum yield, which is beneficial for understanding the properties of photo-deactivation of phosphorescent emitters.

Elucidating the Nonradiative Deactivation Pathways in a Cationic Iridium Complex with 2,4-di(1H-pyrazol-1-yl)Pyridine as the Ancillary Ligand

“…In principle, the k nr of an iridium complex is a sum of temperature-independent and -dependent ones. ,− According to previous studies, − the temperature-independent k nr is correlated with the degree of distortion and the energy difference between the emitting triplet state and the S 0 state, which can be expressed as where Δ E denotes the adiabatic energy difference between the two states and the parameter β is related to the displacement of the potential energy surfaces minima (i.e., the structural distortion) for the two states, which decreases with increasing the structural distortion. From the above relationship, it can be seen that a larger structural distortion between the emitting triplet state and the S 0 state results in a larger temperature-independent k nr .…”

“…It is known that once the 3 MC state is populated, it will either go back to T 1 or reach the MECP between 3 MC and S 0 potential surfaces. 48,55 If the MECP lies close to 3 MC, the 3 MC state will undergo rapid decay back to the S 0 state through passing the MECP. The MECP of [Ir(ppy) 2 (bipzpy)]PF 6 was thus calculated, and its geometry and spin-density distribution are shown in Figure 6c.…”

Towards deep‐blue phosphorescence: molecular design and property prediction of iridium complexes with pyridinylphosphinate ancillary ligand

“…Quantum chemical calculations are becoming a powerful tool to study the electronic structures and predict the photophysical properties of the luminescent metal complexes . In this work, we performed a comparative investigation on both the recently reported complexes 1 and 2 and our designed complexes 3 – 5 .…”