Multifunctional Photocatalysts Based on Half-Sandwich Cyclometalated Ir(III) Complexes with π-Extended Ligands

Area of Science:

• Organometallic Chemistry
• Photocatalysis
• Synthetic Organic Chemistry

Background:

• Photocatalysis offers a sustainable alternative to traditional synthetic methods, reducing reliance on harsh reagents.
• Half-sandwich Iridium(III) complexes are increasingly explored for their catalytic potential.

Purpose of the Study:

• To investigate the photocatalytic applications of half-sandwich Iridium(III) complexes in diverse organic transformations.
• To establish Cp*Ir(III) complexes as efficient and versatile photocatalysts.

Main Methods:

• Employing Cp*Ir(III) complexes as photocatalysts in photooxidative coupling of amines, thioether photooxidation, and N-heterocyclic photodehydrogenation.
• Conducting reactions under mild conditions (room temperature, air/oxygen atmosphere) with low catalyst loadings.
• Utilizing mechanistic studies involving reactive oxygen species (singlet oxygen, superoxide radical) and electron/energy transfer pathways.

Main Results:

• Achieved quantitative imine formation in amine coupling and high chemoselectivity for sulfoxide in thioether oxidation without additives.
• Demonstrated exceptional activity in photodehydrogenation of N-heterocyclic substrates.
• Complex 1 showed activity in aqueous media and under sunlight, achieving full conversion rapidly with low catalyst loadings (0.005-0.25 mol %).

Conclusions:

• Cp*Ir(III) complexes are efficient, versatile, and sustainable photocatalysts for various photooxidative reactions.
• This work presents one of the first uses of half-sandwich Iridium complexes in diverse photooxidative transformations.
• The findings highlight the potential of these complexes in green chemistry applications.