Efficient Dipyrrin-Centered Phosphorescence at Room Temperature from Bis-Cyclometalated Iridium(III) Dipyrrinato Complexes

Abstract

A series of seven dipyrrin-based bis-cyclometalated Ir(III) complexes have been synthesized and characterized. All complexes display a single, irreversible oxidation wave and at least one reversible reduction wave. The electrochemical properties were found to be dominated by dipyrrin centered processes. The complexes were found to display room temperature luminescence with emission maxima ranging from 658 to 685 nm. Through systematic variation of the cyclometalating ligand and the meso substituent of the dipyrrin moiety, it was found that the observed room temperature emission was due to phosphorescence from a dipyrrin-centered triplet state with quantum efficiencies up to 11.5%. Bis-cyclometalated Ir(III) dipyrrin based organic light emitting diodes (OLEDs) display emission at 682 nm with maximum external quantum efficiencies up to 1.0%.

Long‐Lived Room‐Temperature Near‐IR Phosphorescence of BODIPY in a Visible‐Light‐Harvesting N^C^N PtII–Acetylide Complex with a Directly Metalated BODIPY Chromophore

“…Thus, the lowest lying triplet state of complex Pt-1 is the 3 IL state. [13,14,19] This theoretical prediction is consistent with the experimental results for the near-IR BODPY phosphorescence and with the long-lived triplet excited state of complex Pt-1. Typically, the 3 IL state has a longer lifetime than the 3 MLCT state.…”

“…Observation of RT phosphorescence usually requires a strong heavy-atom effect to facilitate the radiative 3 IL!S 0 intersystem crossing (ISC), that is, the phosphorescence. [19] To this end, herein we report the synthesis of complex Pt-1 (Scheme 1), in which two N^C^N Pt II -coordinated units are connected to the p-core of BODIPY to maximize the heavy-atom effect of the Pt atom. Thus, we expected that the RT phosphorescence of BODIPY could be observed.…”

“…The previous values for BODIPY-localized 3 IL states were 8-30 ms. [18,22,25,30] DFT calculations for assignment of the T 1 excited state: To confirm the 3 IL nature of the T 1 state of complex Pt-1, the spin-density surfaces of complexes Pt-1 and Pt-2 were analyzed ( Figure 5). [19] For complex Pt-2, the spin density was distributed on the Pt II center and on the N^C^N ligand; thus, the T 1 state of complex Pt-2 could be safely assigned as a 3 MLCT. However, the spin density for complex Pt-1 was located on the BODIPY chromophore, whilst the N^C^N ligand and the Pt II center made very small contributions.…”

Visible‐Light Harvesting with Cyclometalated Iridium(III) Complexes Having Long‐Lived 3IL Excited States and Their Application in Triplet–Triplet‐Annihilation Based Upconversion

“…[28] Superimposable excitation and UV/Vis absorption spectra for the dyads are shown in the Supporting Information, indicating that the intense absorption at 466 nm is efficient enough to produce the emissive triplet excited state. [29] Assignment of the 3 …”

“…[28] The isosurface of the spin density of Ir-1 is localized on the ppy and phen ligands and the Ir III ion. A similar result was found for Ir-2.…”