Luminescent biscyclometalated arylpyridine iridium(iii) complexes with 4,4′-bi-1,2,3-triazolyl ancillary ligands

Abstract

The synthesis, characterization and photophysical investigation of complexes of the form [Ir(R-ppy)2(btz)]PF6 (1 to 3) are reported (btz = 1,1'-dibenzyl-4,4'-bi-1,2,3-triazolyl, R-ppy = 4-(pyrid-2-yl)benzaldehyde (1), 2-phenylpyridine (2) and 2-(2,4-difluorophenyl)pyridine (3)). Complexes 1, 2 and 3 are luminescent and exhibit structured emission bands with vibronic progressions at 532 & 568 nm (ϕ 0.28%), 476 & 508 nm (ϕ 0.82%) and 454 & 483 nm (ϕ 4.3%) respectively. The structuring of these emission bands is indicative of cyclometalated ligand centred emissive states and is further corroborated by the nearly identical emission spectra for 2 and 3 to previously reported analogous complexes with 4-(pyrid-2-yl)-1,2,3-triazole based ancillary ligands. Computational density functional theory calculations on these complexes show that the LUMOs of 2 and 3 are largely btz-centred but with some cyclometalated pyridine π* character. The LUMO of 1 on the other hand is localized primarily on the cyclometalated ligands. Spin population analysis of the lowest lying triplet excited states for these complexes indicate significant spin population over the iridium centres and the aryl and pyridyl moieties in these complexes with virtually no localization of unpaired electrons over the btz ancillary ligands. This is therefore in agreement with the assignment of the emissive state having largely cyclometalated (3)LC character and being independent of the ancillary ligand.

Supramolecular iridium(III) assemblies

“…The btl ligands formed C-H hydrogen bonds to the anions PF6 in H5 and Clin H6 and a molecule of water, while the dfphtl triazole C-H groups acted as C-H hydrogen bond donors, forming C-N⋯N bonds to one of the nitrogen atom of the btl ligand(Figure 20b). Complexes H5 and H6 were not photostable at room temperature neither in solution nor in the solid state [117,119]. However, at 77 K in 2-MeTHF glass state H6 exhibited a weak emission at l PL = 393, 419 nm.…”

Towards Water Soluble Mitochondria-Targeting Theranostic Osmium(II) Triazole-Based Complexes

“…We, and others, have paid particular attention to the use of copper-catalysed coupling of alkynes and azides to form 1,2,3-triazole-based ligands [7][8][9][10] and have investigated the photophysical properties of their resultant complexes. A significant number of reports have appeared detailing the photophysical and photochemical properties of triazole-based complexes of Re(I), Ru(II) and Ir(III) [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Examples of triazole-containing complexes of osmium(II)…”

Anomalously Long-Lasting Blue PhOLED Featuring Phenyl-Pyrimidine Cyclometalated Iridium Emitter

“…The analysis carried out here is in good agreement with previous reports. 71,72 The 3 LLCT possesses charge-transfer character and hence is relatively forbidden in transition in relation to that of 3 ILCT(pp*). This leads to a significant difference between the excited-state lifetime of MS 19 and those of MS 2 and MS 17; the T 1 / S 1 radiative lifetime of MS 19 is much longer than that of MS 2 or MS 17.…”