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Issue 8, 2003
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Solid-state absorption and luminescence spectroscopy of nitronyl nitroxide radicals

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Abstract

Low-temperature absorption and luminescence spectra of three crystalline nitronyl nitroxides are presented. For 2-(2-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide and 2-(2-benzimidazolyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide, luminescence with resolved vibronic structure is observed between 700 nm and 1100 nm. The modes forming the resolved structure have frequencies of approximately 600 cm−1 and 1400 cm−1. They are characterized by Raman spectroscopy and electronic structure calculations. The intensity distribution within the vibronic progressions indicates small structural changes between the ground and emitting states. The lowest-energy absorption bands observed between 450 nm and 700 nm of the two luminescent compounds and of 2-cyano-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide also show resolved structure, but the overall width of these absorption band systems is larger by a factor of 2 than that of the luminescence spectra. This difference is rationalized in terms of overlapping electronic transitions to at least two excited states arising from the (SOMO − 1)1(SOMO)2 and (SOMO)0(SOMO + 1)1 electron configurations, supported by transition energies and oscillator strengths from density functional calculations.

Graphical abstract: Solid-state absorption and luminescence spectroscopy of nitronyl nitroxide radicals

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Publication details

The article was received on 05 Feb 2003, accepted on 01 Apr 2003 and first published on 26 Jun 2003


Article type: Paper
DOI: 10.1039/B301479G
Citation: New J. Chem., 2003,27, 1200-1206
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    Solid-state absorption and luminescence spectroscopy of nitronyl nitroxide radicals

    R. Beaulac, G. Bussière, C. Reber, C. Lescop and D. Luneau, New J. Chem., 2003, 27, 1200
    DOI: 10.1039/B301479G

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