The first observation of CIDEP generated through the interaction between an excited singlet oxygen molecule and a free radical

Mitsui, Masaaki; Takeda, K.; Kobori, Yasuhiro; Kawai, Akio; Obi, Kinichi

doi:10.1016/0009-2614(96)01058-5

Cited by 25 publications

(38 citation statements)

References 28 publications

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“…The doublet spin-correlated state of TEMPO and the ground-state oxygen molecule (O2(3Eg-)) pair creates the net Abs CIDEP through the doublet precursor RTPM. This has been demonstrated experimentally by Mitsui et al [26]. Figure 9 shows TRESR spectra of TEMPO and the signal time evolutions in the anthracene-TEMPO system in benzene with and without argon bubbling.…”

Section: Cidep In the Oy Ag) Quenchingmentioning

confidence: 73%

“…The basic idea to understand the sign of J is useful to describe the nature of the quenching process and is considered to be helpful in the ESR spectroscopic studies on the excited states of macromolecules which have radicals and excited molecules to create doublet, quartet and quintet excited states [21][22][23][24][25]. The story will be closed by introducing a new technique for determinating the O2(1Ag) lifetime by detecting CIDEP of free radicals used as O2(~Ag) probes [26][27][28][29] and by a comment on the technique.…”

Section: A Kawaimentioning

confidence: 99%

“…Recently, the efficient CIDEP creation in the O2(tAg) and free radical system has been reported [26][27][28][29]. It is well known that O2(tAg) is one of important species in biological systems, and the quenching of O2(1Ag) by radicals has attracted much interest.…”

Section: Cidep In the Oy Ag) Quenchingmentioning

confidence: 99%

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Dynamic electron polarization created by the radical-triplet pair mechanism: Application to the studies on excited state deactivation processes by free radicals

Kawai

2003

Appl. Magn. Reson.

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The radical-triplet pair mechanism for chemically induced dynamic electron polarization (CIDEP) created in the quenching of excited state molecules by free radicals is explained on the basis of recent time-resolved electron spin resonance spectroscopic results and theoretical studies. The CIDEP of 2,2,6,6-tetramethylpiperidinyl-l-oxyl (TEMPO) and galvinoxyl radicals exhibir various CIDEP patterns of net and mutliplet types and CIDEP phases of absorption and emission. The CIDEP patterns are described by the quartet-doublet state mixings within the radical-triplet encounter pairs. The mixings by the spin-dipolar and the hyperfine interactions are responsible for the net and the multiplet patterns, respectively. The factors controlling the CIDEP phases are the spin multiplicity of the excited state quenched by radicals and the sign of the intermolecular exchange interaction of the radical-triplet encounter pairs. In particular, the intermolecular charge transfer effect on the exchange interaction is discussed much in detail from the viewpoints of CIDEP magnitudes and phases. A CIDEP creation in the O2(~Ag)-TEMPO system is also introduced and is described by the radical-triplet pair mechanism. Applications of this CIDEP used asa probe of O2(IAs) in condensed phase are mentioned. I IntroductionExcited state quenching by free radicals such as 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) and galvinoxyl results in the creation of chemically induced dynamic electron polarization (CIDEP) on free radicals [1][2][3][4][5]. These CIDEPs of organic free radicals in liquid phase can be easily detected by the time-resolved (TR) electron spin resonance (ESR) spectroscopic method with enhanced absorption (Abs) or emission (Em) signals of hyperfine lines. As is well known, CIDEPs created in photochemically produced intermediate radicals have been extensively studied by the TRESR method [6]. Therefore, it is promising that CIDEP in the excited states quenching provides fruitful information on the dynamics of the quenching process.

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Section: Cidep In the Oy Ag) Quenchingmentioning

confidence: 73%

Section: A Kawaimentioning

confidence: 99%

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Dynamic electron polarization created by the radical-triplet pair mechanism: Application to the studies on excited state deactivation processes by free radicals

Kawai

2003

Appl. Magn. Reson.

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“…2,6 In contrast to the emissive CIDEP signal from the nitroxide in the absence of oxygen, Obi et al observed absorptiVe CIDEP of nitroxides in air-saturated solutions of nitroxides and triplet sensitizers, such as anthracene, naphthalene, and benzophenone. 9 This unusual absorption phase of the CIDEP was explained with the involvement of singlet oxygen 1 O 2 ( 1 ∆ g ). Singlet oxygen is generated in air-saturated solutions by quenching of the triplet states of the sensitizer by triplet oxygen (eq 6).…”

Section: Introductionmentioning

confidence: 99%

Chemically Induced Dynamic Electron Polarization Generated through the Interaction between Singlet Molecular Oxygen and Nitroxide Radicals

et al. 2005

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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 ( 15 N, 14 N), 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.

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“…Moreover, during the $1 quenching by radical its CIDEP phase becomes opposite to that in the triplet quenching process [48,49]. For example, quenching of O2(1Ag) by TEMPO creates CIDEP and an intense net absorption signal of TEMPO was observed by TRPSR [55,56]. This CIDEP is strong enough to determine the lifetime of O2(IAg) from the time profile of the signal.…”

Section: Cidep Workmentioning

confidence: 95%

Developments of magnetic-resonance-related spin chemistry in Japan

et al. 2003

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Abstraet. A review on the developments of the magnetic-resonance-related spin chemistry in Japan is presented. We describe how studies in this atea started in Japan and developed into the flourishing state of the present. Important contributions made by Japanese spin chemists in the last two decades in three areas, namely, work on chemically induced dynamic electron polarization, excited states and controlling of photochemical reactions, are presented. More emphases are placed on the new deveIopments in recent years, particularty new concepts and new methodologies.

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The first observation of CIDEP generated through the interaction between an excited singlet oxygen molecule and a free radical

Cited by 25 publications

References 28 publications

Dynamic electron polarization created by the radical-triplet pair mechanism: Application to the studies on excited state deactivation processes by free radicals

Dynamic electron polarization created by the radical-triplet pair mechanism: Application to the studies on excited state deactivation processes by free radicals

Chemically Induced Dynamic Electron Polarization Generated through the Interaction between Singlet Molecular Oxygen and Nitroxide Radicals

Developments of magnetic-resonance-related spin chemistry in Japan

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