Tris[1-phenylisoquinoline-C2,N]iridium(III)
[CAS# 435293-93-9]

Identification

• Classification: Catalysts and additives >> Precious metal catalyst
• Name: Tris[1-phenylisoquinoline-C2,N]iridium(III)
• Synonyms: iridium(3+) 1-phenylisoquinoline
• Molecular Formula: C₄₅H₃₀IrN₃
• Molecular Weight: 804.96
• CAS Registry Number: 435293-93-9
• SMILES: C1=CC=C([C-]=C1)C2=NC=CC3=CC=CC=C32.C1=CC=C([C-]=C1)C2=NC=CC3=CC=CC=C32.C1=CC=C([C-]=C1)C2=NC=CC3=CC=CC=C32.[Ir+3]

Properties

• Melting point: 440 °C (Expl.)

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H302-H315-H319-H335
• Safety Statements: P261-P305+P351+P338

Discovery and Applications

Tris[1-phenylisoquinoline-C₂,N]iridium(III) is a cyclometalated iridium(III) complex widely studied and applied in the field of optoelectronic materials, particularly for its role in phosphorescent organic light-emitting diodes (OLEDs). The complex consists of an iridium(III) metal center coordinated by three bidentate ligands derived from 1-phenylisoquinoline. Each ligand binds to the iridium through a carbon atom on the phenyl ring (C₂ position) and a nitrogen atom on the isoquinoline ring (N), forming strong Ir–C and Ir–N bonds that result in a highly stable six-membered chelate.

The discovery and study of tris-cyclometalated iridium complexes like tris[1-phenylisoquinoline-C₂,N]iridium(III) date back to the early 2000s, when research into efficient phosphorescent emitters for OLED technology intensified. Iridium complexes became of particular interest because of their ability to harvest both singlet and triplet excitons through spin–orbit coupling, leading to nearly 100% internal quantum efficiency in electroluminescent devices.

Synthesis of the complex is typically carried out by reacting iridium trichloride hydrate with excess 1-phenylisoquinoline under reflux in a high-boiling solvent such as 2-ethoxyethanol. This step produces a chloro-bridged dimer intermediate, which can be further converted to the tris-homoleptic complex by treatment with a suitable silver or sodium salt to remove chloride, followed by ligand exchange under thermal or microwave-assisted conditions. Purification is often performed using column chromatography or recrystallization from organic solvents such as dichloromethane or acetone.

The complex is best known for its photophysical properties. Tris[1-phenylisoquinoline-C₂,N]iridium(III) typically exhibits deep red to orange-red phosphorescence with high quantum yields and long emission lifetimes in the microsecond range. The emission originates from a metal-to-ligand charge transfer (MLCT) excited state, with contributions from ligand-centered π→π* transitions. These features make it an effective red emitter in OLED devices. Its photoluminescence efficiency and color purity can be tuned by modifying the ligand environment or by co-doping in host matrices such as poly(N-vinylcarbazole) (PVK) or CBP (4,4'-N,N'-dicarbazole-biphenyl).

In practical applications, tris[1-phenylisoquinoline-C₂,N]iridium(III) is used as a dopant in the emissive layer of OLEDs, typically in concentrations of 5–10%. It is dispersed in a host matrix that facilitates charge transport and exciton formation. Devices using this compound have demonstrated excellent electroluminescence performance with high brightness, low drive voltage, and operational stability. It is also of interest in other photonic applications, including light-emitting electrochemical cells (LEECs), sensors, and photocatalysis.

Analytical characterization of the complex includes proton and carbon nuclear magnetic resonance (NMR) spectroscopy, confirming the chelation and ligand symmetry. Ultraviolet-visible (UV-Vis) absorption spectroscopy reveals strong absorption bands in the UV region due to π→π* transitions and weaker MLCT bands extending into the visible range. Photoluminescence spectroscopy is used to evaluate emission wavelength and quantum yield. X-ray crystallography has been employed to determine the octahedral coordination geometry around the iridium center, confirming the facial arrangement of the three bidentate ligands.

Thermogravimetric analysis (TGA) indicates good thermal stability, an important property for vacuum deposition processes in OLED fabrication. The complex is soluble in common organic solvents such as chloroform, toluene, and tetrahydrofuran, which facilitates its processing into thin films via solution-based or vapor deposition methods.

In summary, tris[1-phenylisoquinoline-C₂,N]iridium(III) is a well-characterized phosphorescent iridium(III) complex that has played an important role in the development of red-emitting OLEDs. Its strong luminescence, chemical robustness, and versatile synthesis have made it a valuable material for optoelectronic applications.

References

2019. Sandwich-structure transferable free-form OLEDs for wearable and disposable skin wound photomedicine. Light: Science & Applications, 8(1).
DOI: 10.1038/s41377-019-0221-3

2012. Carbazolyl Benzo[1,2‐b:4,5‐b']difuran: An Ambipolar Host Material for Full‐Color Organic Light‐Emitting Diodes. Chemistry - An Asian Journal, 7(5).
DOI: 10.1002/asia.201200062

2011. New Design Tactics in OLEDs Using Functionalized 2-Phenylpyridine-Type Cyclometalates of Iridium(III) and Platinum(II). Chemistry - An Asian Journal, 6(6).
DOI: 10.1002/asia.201000928