Pre-association enables visible-light induced proton-coupled electron-transfer in a titanium-functionalized...

Area of Science:

• * Inorganic Chemistry
• * Photochemistry
• * Catalysis

Background:

• * Proton-coupled electron transfer (PCET) is crucial for chemical transformations and catalysis.
• * Heterometal-doped polyoxometalates (POMs) serve as model systems for metal oxides, aiding the study of PCET.
• * Selective oxidation of alcohols is a key process in organic synthesis.

Purpose of the Study:

• * To investigate the mechanism of selective photochemical oxidation of benzyl alcohol to benzaldehyde using a titanium-doped Keggin polyoxotungstate.
• * To elucidate the formation and properties of a visible-light photoactive intermediate.
• * To understand the role of PCET in this photo-oxidation process.

Main Methods:

• * Experimental studies including photochemical reactions in aqueous solution.
• * Theoretical calculations to probe reaction mechanisms and properties.
• * Non-aqueous Pourbaix analysis to understand PCET reactivity.

Main Results:

• * Formation of a visible-light photoactive intermediate, [(TiOBn)PW11O39]4-, from the reaction of {TiOH} with benzyl alcohol.
• * Demonstration of photoinduced PCET by the intermediate, leading to benzyl alcohol oxidation and POM reduction/protonation.
• * Comprehensive mechanistic insights into the photo-oxidation process and the properties of involved species.

Conclusions:

• * The titanium-doped POM facilitates selective benzyl alcohol photo-oxidation via a novel photoactive intermediate.
• * The study provides a deep understanding of the PCET mechanism in this system.
• * Offers insights for designing noble metal-free, visible-light photoactive molecular metal oxides for organic photooxidation.