Mechanism of Visible-Light Photooxidative Demethylation of Toluidine Blue O
| Autor: | Alexander Greer, Denis Fuentealba, Germán Günther, Ana María Edwards, Nory Mariño-Ocampo, Pablo Barrias, Daniel Zúñiga-Núñez, José Robinson-Duggon |
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| Rok vydání: | 2019 |
| Předmět: |
010304 chemical physics
Methylamine Photodissociation Kinetics Formaldehyde 010402 general chemistry Photochemistry 01 natural sciences Dissociation (chemistry) 0104 chemical sciences chemistry.chemical_compound chemistry 0103 physical sciences Density functional theory Physical and Theoretical Chemistry Demethylation Visible spectrum |
| Zdroj: | The journal of physical chemistry. A. 123(23) |
| ISSN: | 1520-5215 |
| Popis: | Experiments and theoretical calculations by density functional theory (DFT) have been carried out to examine a self-sensitized type I photooxidation of toluidine blue O (TBO+). This study attempts to build a connection between visible-light photolysis and demethylation processes of methylamine compounds, such as TBO+. We show that controlled photoinduced mono- and double-demethylation of TBO+ can be achieved. The kinetics for the appearance rate of the mono-demethylated TBO+ and the double-demethylated TBO+ were found to fit pseudo-first-order kinetics. DFT calculations have been used to examine the demethylation of TBO+ and included N, N-dimethylaniline as a model compound for TBO+. The results show an oxygen-dependent demethylation process. The mechanism for the sequential methyl loss is proposed to be due to H• or e-/H+ transfer to 3TBO+* followed by a reaction of TBO+• with O2, yielding a C-peroxyTBO+• intermediate. Instead of aminyl radical peroxyl formation, i.e., N-peroxyTBO+•, the C-centered peroxyTBO+• is favored, that upon dimerization (Russell mechanism) leads to dissociation of formaldehyde from the methylamine site. |
| Databáze: | OpenAIRE |
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