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Published on: July 17, 2020
To Photoredox or Not in Neutral Aqueous Solutions for Selected Benzophenone and Anthraquinone Derivatives
Xiting Zhang1,2, Jiani Ma1, David Lee Phillips2
1Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University , Xi'an 710127, P. R. China.
Abstract:
The experimental and theoretical results in neutral aqueous solutions reported here indicate that a proton-coupled electron transfer (PCET) from an alcohol C-H bond to the para-carbonyl is the initial and crucial process for the photoredox reaction of 2-(1-hydroxyethyl)-anthraquinone (HEAQ) to occur while the counterpart 3-(hydroxymethyl)-benzophenone (3-BPOH) compound displays a different PCET from an alcohol O-H bond to the carbonyl as the first step, followed by an intersystem crossing process that does not lead to the analogous photoredox, which is caused by a subtle charge-radical coupled effect between HEAQ and 3-BPOH. This can account for experimental results in the literature that HEAQ can undergo efficient photoredox but 3-BPOH does not under neutral aqueous conditions. These results have implications for the pH-dependent photochemical behavior of aromatic carbonyl compounds in aqueous media.
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