Photophysical Properties of the Seriesfac-andmer-(1-Phenylisoquinolinato-N^∧C^2′)_x(2-phenylpyridinato-N^∧C^2′)_3−xIridium(III) (x= 1−3)

Abstract

The photophysical properties of tris-cyclometalated iridium(III) complexes have been probed by chemical and geometric variation through the series fac- and mer-Ir(piq)(x)(ppy)(3-x) (x = 1-3; piq = 1-phenylisoquinolinato-N(∧)C(2'), ppy = 2-phenylpyridinato-N(∧)C(2')). The phosphorescent decays were recorded in solution at 295 K and in polymer films from 2 to 295 K. In the heteroleptic complexes, emission occurs based solely on the piq ligand(s), at least by the nanosecond time scale, as its excited states are the lowest energy. Because fac-Ir(piq)(3) and fac-Ir(ppy)(3) possess practically the same oxidation potential, comparison of photophysical properties through the series fac-Ir(piq)(x)(ppy)(3-x) (x = 1-3) revealed the effects of having one, two, or three emissive piq ligands with no confounding effects from differences in electron withdrawing or donating properties between the spectator ppy ligands and the piq ligands. Effects of placement of piq ligands in different coordination geometries were elucidated by comparisons to the mer series.

Synthesis, characterization and photophysical properties of two heteroleptic 2-(4,6-difluorophenyl)pyridyl iridium(III) complexes with amidate ancillary ligands

“…Chemical shifts and splittings of signals in 1 H, 13 [26][27][28][29][30] and Ir(III) amidate complexes reported by us [24,25]. The typical chemical shift at 179.19 in 13 C NMR spectrum is characteristic of the amidate carbon atom in the four-membered metallocycle.…”

“…These complexes have been shown to exhibit high quantum efficiencies due to strong spin-orbital coupling of iridium center, which leads to mixing of singlet and triplet excited states and subsequent harvesting of "spin-forbidden" triplet states for photon emission [1][2][3]. Generally, there are two major kinds of iridium(III) emitters: homoleptic Ir(C^N) 3 [9][10][11][12] and heteroleptic (C^N) 2 Ir(LX) [13][14][15][16][17][18][19] complexes (C^N denotes a cyclometalating ligand, such as 2-phenylpyridine etc. ; LX denotes a monoanionic ancillary ligand such as acetylacetonate and picolinate etc.).…”

“…These two complexes have been fully characterized by 1 H, 13 C and 19 F NMR methods, and X-ray crystallography where possible.…”

Organometallic Materials for Electroluminescent and Photovoltaic Devices

“…DFT calculations reveal that the lowest excited state is mainly determined by the C^N ligand but not by β-diketonate when there is large difference between the triplet energy levels of the two parts, providing satisfactory explanation for experimental results. The photophysical properties of facial and meridional tris-cyclometalated iridium(III) complexes containing 2-phenylpyridine and 1-phenylisoquinoline ligands have been reported by Deaton et al (2010). The facial isomers show similar photophysical properties in 2-MeTHF solutions, indicating that the emission occurs based on the piq ligand(s).…”

Mer‐Ir(ppy)3 to Fac‐Ir(ppy)3 Photoisomerization

“…3 MC states are usually highly distorted with respect to the ground state ( 1 GS) and lowest triplet (T 1 ) excited state geometries, [17] the latter typically being of predominant metal-to-ligand charge transfer character, i. e., 3 MLCT. [28][29][30] In a nutshell, it appears evident from this discussion that in order to improve PhOLEDs' efficiencies and stabilities, one should devise tailored phosphor design strategies to prevent the population of 3 MC states. [17,18] Therefore, ligand dissociation is more likely to occur from a 3 MC state than from either 1 GS or T 1 .…”