An electron spin polarization study of the interaction of photoexcited triplet molecules with mono- and polynitroxyl stable free radicals

Journal Article · Thu Feb 11 00:00:00 EST 1993 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100108a007· OSTI ID:6296425

Turro, N J; Khudyakov, I V; Bossmann, S H ^[1]; Dwyer, D W ^[2]

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1. Columbia Univ., New York, NY (United States)
2. State Univ. of New York, Brockport (United States)

Time-resolved electron spin resonance (TR ESR) has been used to investigate the chemically induced dynamic electron polarization (CIDEP) generated by the interaction of stable free radicals with the triplet states of benzophenone, benzil, and 2-acetylnaphthalene. The stable radicals were mono-, di-, tri-, and tetranitroxyl free radicals possessing the 2,2,6,6-tetramethylpiperidine-N-oxyl moiety. All of the stable radical systems investigated were found to be emissively polarized by interaction with the triplet states, and the phase of polarization was independent of the sign of zero-field splitting (D) of the interacting triple molecule. Possible and likely mechanisms of polarization transfer (creation) resulting from the interaction of photoexcited triplet molecules with nitroxyls in the strong electron exchange are discussed. The emissive CIDEP of nitroxyls observed in the interactions with triplet benzil, which has D > 0, provides strong support for the operation of the radical-triplet pair mechanism. Within the time scale of TR ESR experiments ([approximately]10[sup [minus]7]--10[sup [minus]6] s) no significant variation in the shape of the CIDEP spectra of the nitroxyls was observed, either in viscous media or in micelles. It is concluded that intramolecular spin exchange (or conformational change) of polynitroyls occurs much faster than the time resolution of the experiment. 24 refs., 6 figs., 1 tab.

• OSTI ID: 6296425
• Journal Information: Journal of Physical Chemistry; (United States), Vol. 97:6; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
AROMATICS
CHEMICAL REACTIONS
ELECTRONIC STRUCTURE
KETONES
RADICALS
BENZOPHENONE
ELECTRON SPIN RESONANCE
PHOTOCHEMISTRY
POLARIZATION
SPECTROSCOPY
CHEMISTRY
MAGNETIC RESONANCE
ORGANIC COMPOUNDS
RESONANCE
400500* - Photochemistry
400201 - Chemical & Physicochemical Properties