Reduction of aryl halides by consecutive visible light-induced electron transfer processes

Area of Science:

• Organic Chemistry
• Photocatalysis
• Sustainable Synthesis

Background:

• Biological photosynthesis efficiently uses visible light for challenging reactions like water oxidation.
• Conventional chemical photocatalysis typically relies on single-photon excitation, limiting its energetic capacity.
• Perylene bisimide can be reduced to a stable radical anion via photoinduced electron transfer (PET) using visible light.

Purpose of the Study:

• To develop a novel photocatalytic method for activating less reactive chemical bonds.
• To overcome the energetic limitations of single-photon excitation in visible light photoredox catalysis.
• To enable the reduction of stable aryl chlorides using visible light.

Main Methods:

• Utilizing perylene bisimide as a photocatalyst.
• Employing visible light for photoinduced electron transfer (PET).
• Implementing a consecutive PET (conPET) strategy involving excitation of the radical anion.

Main Results:

• The radical anion of perylene bisimide was successfully generated and subsequently excited.
• This double excitation accumulated sufficient energy to reduce stable aryl chlorides.
• Generated aryl radicals were effectively trapped by hydrogen atom donors or used in C-C bond formation.
• Demonstrated the photocatalytic conversion of previously unreactive chemical bonds.

Conclusions:

• Consecutive PET (conPET) is a viable strategy to enhance the energy available from visible light.
• This method expands the scope of visible light photoredox catalysis for organic synthesis.
• conPET offers a sustainable pathway for activating challenging substrates like aryl chlorides.