6274-79-9Relevant academic research and scientific papers
Photolysis of endoperoxides in the presence of nitroxides: A laser flash photolysis study with optical and ESR detection
Moscatelli, Alberto,Sartori, Elena,Ruzzi, Marco,Jockusch, Steffen,Lei, Xuegon,Khudyakov, Igor,Turro, Nicholas
, p. 205 - 210 (2014/02/14)
Time-resolved electron paramagnetic resonance spectroscopy, transient absorption, and phosphorescence spectroscopy were used to investigate the spin polarization of a nitroxide free radical induced by interaction with singlet oxygen (1O2). The latter was generated by photolysis of endoperoxides of two anthracene derivatives. Although both anthracene endoperoxides are structurally similar, opposite spin polarization of the nitroxide was observed. Photolysis of one endoperoxide leads to absorptive nitroxide spin polarization due to interaction with the generated 1O2. Photolysis of the other endoperoxide generated emissive nitroxide spin polarization, probably due to interaction of the endoperoxide triplet states with nitroxides. The Royal Society of Chemistry and Owner Societies.
THE ROLE OF INTERSYSTEM CROSSING STEPS IN SINGLET OXYGEN CHEMISTRY AND PHOTO-OXIDATIONS
Turro, Nicholas J.
, p. 2089 - 2098 (2007/10/02)
Singlet oxygen chemistry and photo-oxidation reactions, in general, often require one or more critical reaction steps that involve an intersystem crossing from a singlet state to a triplet state or vice versa.This paper considers two important intersystem crossing mechanisms, electron spin-electron orbit (spin-orbit) coupling and electron spin-nuclear spin (spin-spin) coupling, and how they may be involved: (1) in the deactivation of 1O2 to 3O2; (2) in the thermal catalytic conversion of 3O2 to 1O2; and (3) in the fragmentation of aromatic endoperoxides to yield O2 and an aromatic substrate.
Mechanism of Thermolysis of Endoperoxides of Aromatic Compounds. Activation Parameters, Magnetic Field, and Magnetic Isotope Effecs
Turro, Nicholas J.,Chow, Ming-Fea,Rigaudy, Jean
, p. 7218 - 7224 (2007/10/02)
A mechanistic investigation has been made of the thermolysis of several endoperoxides of anthracenes and naphthalenes which produce molecular oxygen and the parent aromatic species quantitatively.Qualitative thermochemical measurements in the solid state indicate that in all cases studied, the reactions were endothermic.This situation appears to be valid in solution also.Clean first-order kinetics were observed for these thermolyses.Activation parameters were derived from the temparature dependence of the first-order rate constants.The primary yields of singlet oxygen (1O2) from the several endoperoxides were determined, and a correlation was discovered between the A factors (ΔS values) for thermolysis and the yield of 1O2.It was found that high A factors (positive ΔS values) correlated with relatively low yields of 1O2 and that low A factors (slightly negative or near zero ΔS values) correlated with nearly quantitative yields of 1O2.These two results are interpreted in terms of a diradical mechanism which leads to low yield of 1O2 and a concerted mechanism which leads to quantitative yields of 1O2.This interpretation is consistent with the observation of a magnetic field effect on the yield of 1O2 from endoperoxides whose thermolyses proceed with positive ΔS values and the absence of a magnetic field effect on the yield of 1Oi endoperoxides whose thermolyses proceed with near zero ΔS values.Further support for the occurrence of a diradical mechanism is available from the demonstration of a special 17O isotope effect on the thermolysis of an endoperoxide which is postulated to undergo thermolysis principally via a diradical intermediate.The thermolysis of endoperoxides which decompose mainly by a diradical mechanism yields triplet molecular oxygen that is selectively enriched in 17O.
