Effect of the phosphoryl substituent in the linear nitrone on the spin trapping of superoxide radical and the stability of the superoxide adduct: combined experimental and theoretical studies.
A new phosphorylated linear nitrone N-(4-hydroxybenzyliene)-1-diethoxyphosphoryl-1-methylethylamine N-oxide (4-HOPPN) was synthesized, and its X-ray structure was determined. The spin trapping ability of various kinds of free radicals by 4-HOPPN was evaluated. Kinetic study of decay of the superoxide spin adduct (4-HOPPN-OOH) shows the half-life time of 8.8 min. On the basis of the X-ray structural coordinates, theoretical analyses using density functional theory (DFT) calculations at the B3LYP/6-31+G(d,p)//B3LYP/6-31G(d) level were performed on spin-trapping reactions of superoxide radical with 4-HOPPN and PBN and three possible decay routes for their corresponding superoxide adducts. The comparative calculations on the spin-trapping reactions with superoxide radical predicted that both spin traps share an identical reaction type and have comparable potency when spin trapping superoxide radical. Analysis of the optimized geometries of 4-HOPPN-OOH and PBN-OOH reveals that an introduction of the phosphoryl group can efficiently stabilize the spin adduct through the intramolecular H-bonds, the intramolecular nonbonding attractive interactions, as well as the bulky steric protection. Examination of the decomposition thermodynamics of 4-HOPPN-OOH and PBN-OOH further supports the stabilizing role of the phosphoryl group to a linear phosphorylated spin adduct.
Liu
Yang-Ping
YP
State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China.
Wang
Lan-Fen
LF
Nie
Zhou
Z
Ji
Yi-Qiong
YQ
Liu
Yang
Y
Liu
Ke-Jian
KJ
Tian
Qiu
Q
D018360:Crystallography, X-Ray; D006207:Half-Life; D006860:Hydrogen Bonding; D007700:Kinetics; D008962:Models, Theoretical; D015394:Molecular Structure; D009589:Nitrogen Oxides / Q000737:chemistry*; D017553:Phosphorus Compounds / Q000737:chemistry*; D019097:Spin Trapping / Q000379:methods*; D013481:Superoxides / Q000737:chemistry*; D013816:Thermodynamics
D009589:Nitrogen Oxides; D017553:Phosphorus Compounds; C015388:nitrones; D013481:Superoxides