Reaction of Singlet-Excited 2,3-Diazabicyclo[2.2.2]oct-2-ene and tert-Butoxyl Radicals with Aryl-Substituted Benzofuranones

Abstract

5,7-Di-tert-butyl-3-aryl-3H-benzofuran-2-ones are lactones with potential antioxidant activity, owing to their abstractable benzylic C-H hydrogens. The fluorescence quenching of the azoalkane 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO), an established probe for the hydrogen-donor propensity of chain-breaking antioxidants, was investigated for 16 aryl-substituted benzofuranone derivatives [m,m-(CF3)2, p-CN, m-CN, p-CF3, p-COOCH3, m-CF3, p-Cl, p-F, H, m-CH3, p-CH3, m,p-(CH3)2, p-OCH3, o-CH3, o-CF3, o,m-(CH3)2]. Analysis of the rate data in terms of a linear free energy relationship yielded a reaction constant of rho = +0.35. This implies that n,pi*-excited DBO acts as nucleophilic species. In contrast, hydrogen abstraction of tert-butoxyl radicals from the benzofuranones was accelerated by electron-donating substituents (rho = -0.23), in conformity with the electrophilic character of oxygen-centered alkoxyl radicals. Possible implications for the optimization of the hydrogen-donor propensity of antioxidants through structural variation are discussed.

A fluorinated phosphite traps alkoxy radicals photogenerated at the air/solid interface of a nanoparticle

“…However, in a homogeneous experiment, the detection of trace CH 4 and MeCHO point to the intermediacy of CH 3 •, EtO•, and Ph (Me 2 )CO•, and the idea that these radicals undergo H‐atom transfer reactions. [ 19–21 ]…”

A study on the fluorescence quenching of 9-Aminoacridine by certain antioxidants

“…This observed minimum k q value may be due to a weak quenching because of H abstraction from C-H fragments [28]. Chrysin exhibits relatively higher k q than Diadzein and Flavone due to the presence of resorcinol in ring ''A'' contributing more to fluorescence quenching of 9-Aminoacridine.…”

Investigations on Photoinduced Interaction of 9-Aminoacridine with Certain Catechols and Rutin

“…Fluorescence lifetime measurements is a definite method for understanding the interaction between donor and acceptor systems. In general, the measurement of fluorescence lifetime is the useful technique to distinguish static and dynamic quenching [19].…”