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Elucidating the Non-Radiative Deactivation Pathways in a Cationic Iridium Complex with 2,4-di(1 <i>H</i> -pyrazol-1-yl)Pyridine as the Ancillary Ligand
摘要： Deep insight into the non-radiative deactivation pathways in phosphorescent cationic iridium complexes is critically important for developing efficient blue-emitting complexes toward advanced applications. Here, we report the synthesis, photophysical and electrochemical characterizations of a blue-green-emitting cationic iridium complex [Ir(ppy)2(bipzpy)]PF6 (Hppy is 2-phenylpyridine and bipzpy is 2,4-di(1H-pyrazol-1-yl)pyridine). The non-radiative deactivation pathways in [Ir(ppy)2(bipzpy)]PF6 have been elucidated through extensive density functional theory calculations. The calculations reveal that the higher-lying charge-transfer (CT) state in [Ir(ppy)2(bipzpy)]PF6, which arises from Ir/ppy→bipzpy transitions, favors non-radiative deactivation because of its large structural distortion compared to the ground state. Both the CT state and the dark metal-centered (3MC) state can be thermally accessed by the lowest-lying emitting triplet state at room temperature, with the former being much more easily accessible, which causes additional non-radiative deactivations for the emitting triplet state. The active roles of the CT and 3MC states in the non-radiative deactivation pathways are, for the first time, confirmed in such blue-emitting complexes with pzpy-type ancillary ligands (pzpy is 2-(1H-pyrazol-1-yl)pyridine).
关键词： charge-transfer state,metal-centered state,density functional theory,blue-emitting complexes,phosphorescent cationic iridium complexes,non-radiative deactivation
更新于2025-09-10 09:29:36
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[Springer Theses] The Electronic Transitions of Molecular Oxygen || Temperature Effects on the Lifetime of O2(a1Δg)
摘要： The non-radiative deactivation of O2(a1(cid:2)g) and O2(b1(cid:3) + g) by solvent molecules has been a topic of intense and extensive research for almost half a century. The seminal interest derived in part from an unusually large effect of solvent and solvent deuteration on the lifetime of O2(a1(cid:2)g). The lifetime of O2(a1(cid:2)g), τ (cid:2), varies by 5 orders of magnitude in different solvents, and differences between H/D-isotopologues of the same solvent often exceed a factor of 20. The early reports on the subject were based on indirect probe-based measurements of τ (cid:2). Therefore, the interpretations were often misguided and afforded considerable controversy. With the advent of fast near-IR sensitive detectors in the late 1970s, it became possible to detect O2(a1(cid:2)g) phosphorescence with time-resolution. This facilitated the recording of an increasingly accurate set of data, which in turn, led to the development of ever more sophisticated theories. This effort culminated in the 1990’s with the development of an empirical model of electronic-to-vibrational (e-to-v) energy transfer. This model, which by now is widely accepted, focusses on the solvent as a “vibrational energy sink” that accept the excitation energy of O2(a1(cid:2)g) and O2(b1(cid:3) + g). In particular, the model accounts nicely for H/D solvent isotope effects on τ (cid:2) that are signi?cantly different from those observed on τ (cid:3). Nevertheless, as we shall see in the present chapter, it still has some important limitations.
关键词： electronic-to-vibrational energy transfer,solvent molecules,temperature effects,O2(a1(cid:2)g),non-radiative deactivation
更新于2025-09-04 15:30:14