Redox and spin-trapping properties of phosphoryldithioacetates

Area of Science:

• Organophosphorus chemistry
• Free radical chemistry
• Computational chemistry

Background:

• Dithioesters are versatile organosulfur compounds with interesting redox properties.
• Understanding the reactivity of dithioesters with free radicals is crucial for synthetic applications.
• Phosphoryldithioacetates represent a class of compounds with potential for unique electronic interactions.

Purpose of the Study:

• To investigate the redox properties of novel ethyl and methyl diethoxyphosphoryldithioacetates.
• To explore the reactivity of these compounds towards free radicals.
• To elucidate the factors governing spin adduct formation and stability.

Main Methods:

• Cyclic voltammetry was employed to measure the redox potentials of the dithioesters.
• Electron Spin Resonance (ESR) spectroscopy was used to detect and analyze spin adducts.
• Density Functional Theory (DFT) calculations were performed to model radical behavior and spectral variations.

Main Results:

• Ethyl diethoxyphosphoryldithioacetate (1), methyl diethoxyphosphorylfluorodithioacetate (2), and methyl diethoxyphosphoryldifluorodithioacetate (3) exhibited distinct redox profiles.
• Free radical addition resulted in detectable ESR spectra of spin adducts only for compounds 2 and 3.
• Reduction potentials correlated with the observed spin adduct formation, suggesting capto-dative stabilization.
• DFT calculations explained temperature-dependent ESR spectral changes by restricted rotation around the Cα-SMe bond.

Conclusions:

• The presence of fluorine atoms significantly influences the redox properties and radical trapping ability of phosphoryl-substituted dithioacetates.
• Capto-dative stabilization plays a key role in the formation and persistence of spin adducts.
• Computational modeling provides valuable insights into the structural and dynamic factors affecting radical stability in these systems.