An Iridium Complex as Bidentate Halogen Bond-Based Anion Receptor Featuring an IncreasedOptical Response.

Area of Science:

• Coordination Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Development of highly sensitive chemo-sensors for anion detection is crucial.
• Iridium(III) complexes are promising luminescent materials but often lack efficient anion binding sites.
• Halogen bonding offers a powerful non-covalent interaction for molecular recognition.

Purpose of the Study:

• To design and synthesize a novel luminescent Iridium(III) complex incorporating a bidentate halogen bond donor.
• To investigate the anion binding properties and sensing capabilities of the new complex.
• To enhance the emission quantum yield for improved sensing performance.

Main Methods:

• Synthesis of a tailor-made Iridium(III) complex, denoted as Ir(III)(L)2.
• Emission titration experiments to study the binding of anions (chloride, bromide, acetate).
• Quantum chemical simulations to support experimental observations.

Main Results:

• The synthesized Ir(III)(L)2 complex exhibits a significantly higher emission quantum yield (8.4%) compared to previous Ir(III) sensors (2.5%).
• Successful demonstration of binding for chloride, bromide, and acetate ions.
• Determination of association constants up to 1.6×10^5 M^-1, with a novel method utilizing emission shifts.

Conclusions:

• The developed Ir(III) complex effectively binds anions through its halogen bond donor site.
• The complex shows superior luminescent properties, making it a promising candidate for anion sensing.
• The study introduces a new method for evaluating association constants in luminescent sensing systems.