(4,4'-Di-tert-butyl-2,2'-bipyridine)di[(2-pyridinyl)phenyl]iridium hexafluorophosphate
[CAS# 676525-77-2]

Identification

• Classification: Organic raw materials >> Organometallic compound >> Organic iridium
• Name: (4,4'-Di-tert-butyl-2,2'-bipyridine)di[(2-pyridinyl)phenyl]iridium hexafluorophosphate
• Synonyms: Ir(dtb-bpy)(ppy)2PF6
• Molecular Formula: C₄₀H₄₀IrN₄.PF₆
• Molecular Weight: 913.95
• CAS Registry Number: 676525-77-2
• EC Number: 811-051-0
• SMILES: CC(C)(C)C1=CC(=NC=C1)C2=NC=CC(=C2)C(C)(C)C.C1=CC=C([C-]=C1)C2=CC=CC=N2.C1=CC=C([C-]=C1)C2=CC=CC=N2.F[P-](F)(F)(F)(F)F.[Ir+3]

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H302-H315-H319-H335-H412
• Safety Statements: P261-P264-P264+P265-P270-P271-P273-P280-P301+P317-P302+P352-P304+P340-P305+P351+P338-P319-P321-P330-P332+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319
Specific target organ toxicity - single exposure	STOT SE	3	H335

Discovery and Applications

(4,4'-Di-tert-butyl-2,2'-bipyridine)di[(2-pyridinyl)phenyl]iridium hexafluorophosphate is a luminescent transition metal complex commonly referred to in the field of organometallic chemistry and photophysics. It is an iridium(III) complex in which the central iridium ion is coordinated to one bidentate 4,4'-di-tert-butyl-2,2'-bipyridine (dtb-bpy) ligand and two cyclometalated 2-phenylpyridine (ppy) ligands. The complex carries a single positive charge, balanced by a hexafluorophosphate (PF₆⁻) counterion. Its empirical formula is typically written as [Ir(dtb-bpy)(ppy)₂]PF₆.

This compound is representative of a larger family of cyclometalated iridium(III) complexes that have attracted extensive research interest due to their intense phosphorescence at room temperature, long excited-state lifetimes, and high photostability. The presence of the bulky tert-butyl groups on the bipyridine ligand improves solubility in organic solvents and suppresses intermolecular aggregation, which is beneficial in optoelectronic device fabrication.

The complex was developed as part of the broader effort to optimize light-emitting materials for use in organic light-emitting diodes (OLEDs). Iridium(III) complexes like this one are widely used as phosphorescent dopants in OLED devices, where their triplet-emitting properties enable efficient harvesting of both singlet and triplet excitons, resulting in nearly 100% internal quantum efficiency. The combination of strong metal-to-ligand charge transfer (MLCT) and ligand-centered (LC) transitions allows precise tuning of emission color, quantum yield, and excited-state dynamics through ligand modification.

Synthetically, the complex is typically prepared via a multi-step procedure. First, the dimeric precursor [Ir(ppy)₂Cl]₂ is synthesized by reacting iridium trichloride hydrate with excess 2-phenylpyridine under reflux. This dimer is then reacted with 4,4'-di-tert-butyl-2,2'-bipyridine in the presence of a silver salt such as AgPF₆ or AgNO₃ to yield the monomeric cationic complex. The use of hexafluorophosphate as the counterion is common, as it enhances crystallinity and reduces coordinating interactions that may quench photoluminescence.

The photophysical properties of [Ir(dtb-bpy)(ppy)₂]PF₆ include strong absorption in the ultraviolet-visible (UV-Vis) region and efficient phosphorescent emission typically in the green to orange range, depending on the exact ligand environment. These properties make it useful not only in OLEDs but also in light-emitting electrochemical cells (LEECs), photoredox catalysis, and as luminescent probes in bioimaging and chemical sensing.

Electrochemical characterization of the complex using cyclic voltammetry reveals reversible oxidation and reduction processes, reflecting the redox-active nature of the iridium center and the conjugated ligands. The photoluminescent quantum yield and excited-state lifetime are typically measured using steady-state and time-resolved fluorescence spectroscopy.

In addition to its application in OLEDs, the complex has been studied for use in triplet-triplet annihilation upconversion, photochemical water splitting, and photocatalytic organic transformations. Its ability to absorb light and engage in energy or electron transfer reactions makes it valuable in systems that convert light energy into chemical energy.

In conclusion, (4,4'-Di-tert-butyl-2,2'-bipyridine)di[(2-pyridinyl)phenyl]iridium hexafluorophosphate is a prominent example of a phosphorescent iridium(III) complex, prized for its high luminescence efficiency, robust photostability, and tunable emission properties. Its synthesis, structure, and electronic characteristics have made it a cornerstone material in optoelectronics, catalysis, and luminescent sensing applications.

References

2012. Engaging unactivated alkyl, alkenyl and aryl iodides in visible light-mediated free radical reactions. Nature Chemistry, 4(10).
DOI: 10.1038/nchem.1452