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Research into phosphorescent Ir(III) complexes has grown immensely since their first report. Talented chemists have successfully synthesized complexes capable of emitting from the ultraviolet to the near-infrared regions of the electromagnetic spectrum. Tuning the emission energy in a selective manner requires knowledge of how ligand substitution affects not only energy levels such as the highest occupied molecular orbital and lowest unoccupied molecular orbital, but also the emissive triplet energy level. This review describes fundamental principles involved in energy-level engineering and substituent selection as well as fundamental methods of device characterization. [ABSTRACT FROM AUTHOR]

Following our recent work on theuse of Co(III) complexes as p-typedopants for triarylamine-based organic hole-conductors, we hereinreport on two new Co(III) complexes for doping applications. Withthe aim of ameliorating the dopant’s suitability for its usein solid-state dye-sensitized solar cells, we show how the propertiesof the dopant can be easily adjusted by a slight modification of themolecular structure. We prove the eligibility of the two new dopantsby characterizing their optical and electrochemical properties andgive evidence that both of them can be used to oxidize the molecularhole-transporter spiro-MeOTAD. Finally, we fabricate high-performancesolid-state dye-sensitized solar cells using a state-of-the-art metal-freeorganic sensitizer in order to elucidate the influence of the typeof dopant on device performance. [ABSTRACT FROM AUTHOR]

Highlights: [•] Five new bidentate and tridentate azole-pyridine ligands. [•] Nine new homoleptic octahedral cobalt(II) complexes with azole-pyridines. [•] How to control redox and optical properties of cobalt(II) complexes. [ABSTRACT FROM AUTHOR]

Highlights: [•] Synthesis and characterization of a [Co(Cl-phenyl-terpy)2]2+/3+ redox couple. [•] Good agreement between experimental and calculated redox potentials. [•] Photovoltaic efficiency compared to the [Co(bpy)3]2+/3+ electrolyte with different counterions. [•] Improvement of the photovoltaic performances by using the CDCA additive. [Copyright &y& Elsevier]

Highlights: [•] Four new alkyl-substituted 1-(2′-pyridyl)-pyrazole ligands. [•] Five new green-phosphorescent cationic cyclometalated iridium(III) complexes. [•] Phosphorescence is quenched by alkyl groups that hinder iridium(III)–ligand bonding. [Copyright &y& Elsevier]

Abstract: We achieve a 20–58nm (610–1890cm−1) blue-shift of the phosphorescence maximum of iridium(III) complexes [(C^N)2Ir(N^N)](PF6) of 1,10-phenanthrolines (N^N) by modifying the cyclometalating 2-phenylpyridine ligand (C^N = ppy) with an electron-withdrawing 4′-fluoro or 4′-trifluoromethyl group or by replacing the pyridine in ppy with a pyrazole. New complexes exhibit green or yellow phosphorescence in argon-saturated 10−5 M dichloromethane solution at room temperature with a maximum at 525–563nm, quantum yield of 54–68%, and excited-state lifetime of 1.1–2.7μs. [Copyright &y& Elsevier]

We report seven heteroleptic cationic iridium(III) complexeswithcyclometalating N-arylazoles and alkyl/aryl isocyanides, [(C∧N)2Ir(CNR)2](CF3SO3),and characterize two of them by crystal structure analysis. The complexesare air- and moisture-stable white solids that have electronic transitionsat very high energy with absorption onset at 320–380 nm. Thecomplexes are difficult to reduce and oxidize; they exhibit irreversibleelectrochemical processes with peak potentials (against ferrocene)at −2.74 to −2.37 V (reduction) and 0.99–1.56V (oxidation) and have a large redox gap of 3.49–4.26 V. Thereduction potential of the complex is determined by the azole heterocycle(pyrazole or indazole) and by the isocyanide (tert-butyl or 2,6-dimethylphenyl) and the oxidation potential by theIr–aryl fragment [aryl = 2′,4′-R2-phenyl(R = H/F), 9′,9′-dihexyl-2′-fluorenyl]. Threeof the complexes exhibit phosphorescence in argon-saturated dichloromethaneand acetonitrile solutions at room temperature with 0–0 transitionsat 473–478 nm (green color; the emission spectra are solvent-independent),quantum yields of 3–25%, and long excited-state lifetimes of62–350 μs. All of the complexes are phosphorescent at77 K with 0–0 transitions at 387–474 nm (blue to greencolor). The extremely long calculated radiative lifetimes, 0.5–3.5ms, confirm that the complexes emit from a cyclometalating-ligand-centeredexcited state. [ABSTRACT FROM AUTHOR]

Abstract: Cationic bis-cyclometalated iridium(III) complexes [(C^N)2Ir(N^N)](PF6) with 2-(2′-pyridyl)-5-R-1,3,4-oxadiazoles (N^N; R=1-adamantyl, mesityl, N-diphenylamino) have a redox gap of 2.58–2.68V and exhibit orange–red phosphorescence in argon-saturated dichloromethane solution with a maximum, quantum yield, and excited-state lifetime of 613–644nm, 2–6%, and 90–280ns. [Copyright &y& Elsevier]

We report the first comprehensive comparative synthetic,structural,electrochemical, and spectroscopic study of an extended series offluorocarbon-modified iridium(III) complexes. We prepared seven newcationic Ir(III) complexes with tert-butyl isocyanideand trifluoromethyl- or trifluoromethoxy-substituted cyclometalating2-phenylpyridines, [(C∧N)2Ir(CNtBu)2](CF3SO3), and characterizedfive of them by crystal structure analysis. The redox potentials andphotophysical properties of Ir(III) complexes are determined by thetype, position, and number of fluorocarbon groups in the cyclometalatingligand. The complexes exhibit pale blue to yellow-green phosphorescenceat room temperature with quantum yields and excited-state lifetimesup to 73% and 84 μs in solution (under argon) and 7.5% and 4.3μs in neat solid (under air). The structured and solvent-independentphosphorescence spectra, with 0–0 emission transition at 445–467nm, and the long calculated radiative lifetimes, 43–160 μs,indicate that the complexes emit from a cyclometalating-ligand-centeredtriplet excited state. Bulky fluorocarbon groups prevent intermolecularinteraction (aggregation) of the complexes, thereby minimizing red-shiftof phosphorescence color in going from solution to neat solid. [ABSTRACT FROM AUTHOR]

Abstract: Two new cationic iridium(III) complexes with cyclometalating 1-phenylindazole or 2-phenyl-1,2,3-triazole ligands, [(C^N)2Ir(4,4′-di-tert-butyl-2,2′-dipyridyl)](PF6), exhibit yellow or green phosphorescence with quantum yields and excited state lifetimes of up to 45% and 840ns in argon-saturated dichloromethane solution at room temperature. [Copyright &y& Elsevier]