Effect of solvent nature on spin exchange in rigid nitroxide biradicals |
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| Authors: | A I Kokorin V A Tran K Rasmussen G Grampp |
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| Institution: | 1. N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, Kosygin ulitsa 4, 119991, Moscow, Russian Federation
2. Institute of Physical and Theoretical Chemistry, Graz University of Technology, Graz, Austria
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| Abstract: | Intramolecular electron spin exchange as a function of temperature and solvent viscosity and polarity has been studied by
X-band electron paramagnetic resonance (EPR) spectroscopy in two rigid nitroxide biradicals existing in one spatial conformation
only. Temperature variations of the isotropic hyperfine splitting constanta and exchange integral value |J/a| were measured from EPR spectra and subsequently analyzed. The interaction of polar solvent molecules with >N-O fragments
of nitroxide groups led to a slight decrease of the |J/a| value with the increase of temperatureT. In contrast, the interaction of polar solvent molecules with functional groups inside the bridge resulted in a noticeable
increase of |J/a| vs.T. In the last case, a coverse relationship between the values of |J/a| and the hyperfine splitting constanta has been observed for solvents with different polarity. |
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