Singlet Oxygen Generation, Quenching and Reactivity with Metal Thiolates

Area of Science:

• Inorganic Chemistry
• Photochemistry
• Organic Chemistry

Background:

• Metal thiolate complexes exhibit diverse roles in singlet oxygen chemistry, acting as photosensitizers, quenchers, or reactants.
• Understanding these reactions is crucial for developing new photosensitizers and catalysts.

Purpose of the Study:

• To review the chemical reactions between thiolate ligands in metal complexes and singlet oxygen.
• To discuss singlet oxygen generation by metal complexes, including self-sensitized photooxidations.
• To analyze mechanistic aspects, such as the influence of protic versus aprotic conditions.

Main Methods:

• Comprehensive literature review of metal thiolate complex reactions with singlet oxygen up to early 2021.
• Comparison of reaction mechanisms with photooxidation of organic sulfides.
• Analysis of reactivity patterns based on thiolate ligand structure (aryl vs. alkyl).

Main Results:

• The rate of singlet oxygen removal generally correlates with the nucleophilicity of the thiolate ligand, modulated by the metal center.
• Metal arylthiolate complexes exclusively yield sulfinate products (metal-bound sulfones).
• Metal alkylthiolate complexes can produce either sulfinate or sulfenate (metal-bound sulfoxides) products.

Conclusions:

• The reaction of metal thiolate complexes with singlet oxygen shows distinct product distributions based on ligand type.
• While mechanistic pathways are proposed, the precise nature of reaction intermediates remains elusive.
• Further research is needed to elucidate the exact intermediates and reaction mechanisms.