A Comprehensive Survey of Cationic Iridium(III) Complexes Bearing Nontraditional Ligand Chelation Motifs

Abstract

The useful optoelectronic properties of cationic iridium(III) complexes have been exploited in diverse applications, from visual displays to biological probes to analytical sensors. It is thus not surprising to note the increased recent efforts to document, understand, and ultimately control the photophysical and electrochemical properties of the archetypal cationic iridium(III) complex [(ppy) 2 Ir(bpy)] + , in which ppyH = 2phenylpyridine and bpy = 2,2Ј-bipyridine, and decorated versions thereof. Of the ligand architectures explored, the [a] Département 2986with N-heterocyclic carbenes (NHCs) are also included within the survey. We also wish to direct the reader to other recent review articles on other facets of Ir III chemistry, property evaluation, and applications. [1] This Review commences with a historical overview of iridium(III) chemistry, an account of the properties of iridium, and a comprehensive description of the photophysical properties of [(ppy) 2 Ir(bpy)] + (1), supported by a detailed DFT study. Following this perspective, the survey is then organized by type of heterocycle. The properties of these complexes are compared and contrasted with the archetype complex 1 and fluorinated congener [(dFppy) 2 Ir(bpy)] + (2), which in this Review act as benchmarks. Finally, optoelectronic data from complexes with structurally similar ligands are collated together to elucidate more clearly the salient structure-property relationships.

Synthesis, Properties, and Light-Emitting Electrochemical Cell (LEEC) Device Fabrication of Cationic Ir(III) Complexes Bearing Electron-Withdrawing Groups on the Cyclometallating Ligands

“…Thus, and also following literature data of structurally similar cationic Ir(III) complexes, 4,56 the oxidation potentials of complexes 1 – 4 are assigned to the removal of an electron from an admixture of the (metal + C^N)-based orbitals. The lower energies calculated for the HOMOs of 1 ( E HOMO = −5.87 eV), 2 ( E HOMO = −5.76 eV), 3 ( E HOMO = −5.83 eV), and 4 ( E HOMO = −6.13 eV) compared to that of R1 ( E HOMO = −5.56 eV) are in good agreement with the higher anodic potentials measured for complexes 1 – 4 in comparison to that of R1 (Table 1).…”

“…These predictions are consistent with the presence of vibronic structure in both the phosphorescence and low-energy absorbance spectra and relatively long radiative lifetimes present in 1 , 3 , and 4 ; calculations likewise predict the mixed CT character of the excited state found in 2 . 2,4,60,65 …”

“…1−4 Due to facile color tuning, high photoluminescence quantum yield (Φ PL ) and short emission lifetimes (τ e ), iridium complexes are ideal emissive materials for electroluminescent (EL) devices and remain the most popular materials for use in organic light-emitting diodes (OLEDs) and in light-emitting electrochemical cells (LEECs). For lighting and display applications, bright and stable red, green, and blue emitters are all required.…”

Protonation‐Dependent Luminescence of an Iridium(III) Bibenzimidazole Chromophore

“…However, on the basis of investigations on the related complex [(ppy) 2 Ir(bpy)] + (bpy = 2,2Ј-bipyridine; R6), the major contribution to the absorption band at λ = 380 nm should be a mixed dπ Ǟ π* ppy 1 MLCT and a ligand-centered π Ǟ π* (LC) transition of the ppy ligand. [42] The lower-energy band at λ = 450-550 nm can be associated with direct excitation into the 3 MLCT, which is, however, mixed with the 3 π-π* transition. This assignment is based on the observation of similar absorptions for corresponding iridium complexes.…”

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)…”