The reactive oxygen species (ROS) scavenging capacities of ginkgolides and bilobalide, which are the peculiar constituents of the extract of Ginkgo biloba, are investigated in silico (level of theory: (SMD)-M06-2X/6-311+G(d,p)//M06-2X/6-31G(d)). Unlike other popular antioxidant natural substances, the carbon backbones of these compounds are entirely aliphatic and exclusively single C–C bonds are present. The selectivity for alkoxyl radicals via hydrogen-atom transfer (HAT) is assessed; importantly, the scavenging of peroxyl radicals is also possible from a peculiar site, here labeled C10 both for ginkgolides and bilobalide. The energetics are described in detail, and the analysis discloses that the studied compounds are powerful scavengers, with thermodynamic and kinetic properties similar to those of Trolox and melatonin, and that, in addition, they display selectivity for peroxyl radicals. These are all chemical-reactivity features contributing to the therapeutic action of the extract of G. biloba.

The combination of intrinsic bond orbital and activation strain analysis allows the correct identification and rationalization of the operative mechanism between HAT and CPET, while the singly occupied molecular orbital does not fit in this picture.

Recent advancements in electro-photoredox catalysis (e-PRC) and consecutive photoinduced electron transfer (conPET) have pushed the energy limits of conventional photocatalysis. Both methods produce open-shell intermediate catalysts that, upon light absorption, become highly reducing or oxidizing, enabling challenging reactions. Despite their widespread use, the mechanisms of e-PRC and conPET reactions remain debated, in part due to a lack of quantitative data in most studiesparticularly single-electron transfer rate constants (k _SET) between excited-state catalysts and substrates. We present a straightforward electrochemical method for determining k _SET using cyclic voltammetry (CV) under light irradiation, paired with electrochemical simulation. Using inexpensive LEDs and standard potentiostats, we investigated the reactivity of excited-state anions of a perylene diimide dye (PDI), the seminal catalyst of conPET reactions. CV was used to study the photochemical reactivity of both reduced species of PDI, *PDI^•– and *PDI^2–, in the reductive cleavage of carbon–halogen bonds in alkyl and aryl halides. The extreme reactivity of these excited-state anions is confirmed, with quenching rate constants of 10⁷ and 10¹⁰ M^–1 s^–1 for *PDI^•– and *PDI^2–, respectively, consistent with theoretical and experimental data. The voltammetric approach presented here provides a rapid and reliable tool for studying the excited-state reactivity of labile intermediates utilized in e-PRC and conPET systems, including both radical anions and dianions.

PhSeZnCl, which is also known as Santi's reagent, can catalyze the reduction of hydrogen peroxide by thiols with a GPx-like mechanism. In this work, the first step of this catalytic cycle, i.e., the reduction of H₂O₂ by PhSeZnCl, is investigated in silico using state-of-the-art density functional theory calculations. Then, the role of the metal is evaluated by replacing Zn with its group 12 siblings (Cd and Hg). The thermodynamic and kinetic factors favoring Zn are elucidated. Furthermore, the role of the halogen is considered by replacing Cl with Br in all three metal compounds, and this turns out to be negligible. Finally, the overall GPx-like mechanism of PhSeZnCl and PhSeZnBr is discussed by evaluating the energetics of the mechanistic path leading to the disulfide product.

Phenolic compounds are important antioxidants with great ROS scavenging potential and the presence of the hydroxyl groups is fundamental for this chemical activity. Therefore, changing the chalcogen atom (oxygen) with any of its siblings of group 16 (sulfur, selenium and tellurium) may affect the reactivity of these compounds. In this work, the ROS scavenging activity and mechanism of phenyl chalcogenols was evaluated in silico, unravelling better performance with heavier chalcogens, both thermodynamically and kinetically. Furthermore, a scavenging mechanism switch is reported, moving from Concerted Proton Electron Transfer (CPET) in phenols to Hydrogen Atom Transfer (HAT) in the other phenyl chalcogenols. Both kinetic trends and mechanistic features are rationalized in the framework of Activation Strain Analysis (ASA). Lastly, the role of aromaticity is evidenced by analyzing the differences between the phenol/phenoxyl and methanol/methoxyl self-exchange reactions, as well as between the corresponding processes with the other chalcogens.