title: Reactivity of molecular oxygen with ethoxycarbonyl derivatives of tetrathiatriarylmethyl radicals.
abstract: Tetrathiatriarylmethyl (TAM) radicals are commonly used as oximetry probes for electron paramagnetic resonance imaging applications. In this study, the electronic properties and the thermodynamic preferences for O2 addition to various TAM-type triarylmethyl (trityl) radicals were theoretically investigated. The radicals' stability in the presence of O2 and biological milieu was also experimentally assessed using EPR spectroscopy. Results show that H substitution on the aromatic ring affects the trityl radical's stability (tricarboxylate salt 1-CO2Na > triester 1-CO2Et > diester 2-CO2Et > monoester 3-CO2Et) and may lead to substitution reactions in cellular systems. We propose that this degradation process involves an arylperoxyl radical that can further decompose to alcohol or quinone products. This study demonstrates how computational chemistry can be used as a tool to rationalize radical stability in the redox environment of biological systems and aid in the future design of more biostable trityl radicals.
authors.affiliation: Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Shijing
authors.initials: S
authors.lastname: Xia
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Villamena
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Hadad
authors.forename: Periannan
authors.initials: P
authors.lastname: Kuppusamy
authors.forename: Yunbo
authors.initials: Y
authors.lastname: Li
authors.forename: Hong
authors.initials: H
authors.lastname: Zhu
authors.forename: Jay L
authors.initials: JL
authors.lastname: Zweier
mesh_terms: D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D005019:Ethyl Ethers / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry*; D015335:Molecular Probes; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010092:Oximetry / Q000379:methods; D010100:Oxygen / Q000737:chemistry*; D013816:Thermodynamics; D014320:Triphenylmethyl Compounds / Q000737:chemistry*
chemical_list: D005019:Ethyl Ethers; D005609:Free Radicals; D015335:Molecular Probes; D014320:Triphenylmethyl Compounds; D010100:Oxygen