title: Chemically induced dynamic electron polarization generated through the interaction between singlet molecular oxygen and nitroxide radicals.
abstract: An absorptive chemically induced dynamic electron polarization (CIDEP) was generated by the quenching of singlet oxygen by nitroxide radicals (TEMPO derivatives). The spin polarization decay time of the nitroxide (measured by time-resolved EPR) correlates with the lifetime of singlet oxygen (measured by singlet oxygen phosphorescence spectroscopy). In addition, a deuterium isotope effect on the spin polarization decay time was observed, a signature of singlet oxygen involvement. With use of isotope labeled nitroxides (15N, 14N), the relative spin polarization efficiencies of TEMPO, 4-oxo-TEMPO, and 4-hydroxy-TEMPO by singlet oxygen were determined. The relative spin polarization efficiencies (per quenching event) decrease in the order 4-hydroxy-TEMPO > TEMPO > 4-oxo-TEMPO, whereas an opposite trend was observed for the total quenching rate constants of singlet oxygen by the nitroxides where the order is 4-hydroxy-TEMPO < TEMPO < 4-oxo-TEMPO.
authors.affiliation: Department of Chemistry, Columbia University, New York, New York 10027, USA.
authors.forename: Claudia G
authors.initials: CG
authors.lastname: Martínez
authors.forename: Steffen
authors.initials: S
authors.lastname: Jockusch
authors.forename: Marco
authors.initials: M
authors.lastname: Ruzzi
authors.forename: Elena
authors.initials: E
authors.lastname: Sartori
authors.forename: Alberto
authors.initials: A
authors.lastname: Moscatelli
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Turro
authors.forename: Anatoly L
authors.initials: AL
authors.lastname: Buchachenko