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Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels
Published on: July 4, 2016
3,5-Di-tert-butyl-3'-(N-tert-butyl-N-aminoxy)-4-oxybiphenyl: A Heterospin Diradical with Temperature Dependent
Yi Liao1, Chunping Xie1, Paul M Lahti1
1Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003 and Bruker Instruments Inc., Billerica, Massachusetts 01821.
Abstract:
The title diradical was synthesized and investigated by ESR and UV-vis spectroscopy. It was found to have a lifetime of weeks even in the presence of oxygen, and even survives brief heating in toluene up to about 60 °C. In the UV-vis spectrum, the diradical showed reversible thermochromic behavior in the -10 to 50 °C range. In the ESR spectrum, hyperfine analysis showed nearly isolated behavior by the phenoxyl and nitroxide spin carrying units. Upon warming, additional, broad lines appeared at the expense of the lower temperature lines. This temperature behavior was reversible over the 0 to 50 °C range, so long as the raised temperatures were not maintained for long time periods. The spectral behavior is interpreted as being due to temperature-dependent conformational effects on the exchange coupling between the spin carrying units, i.e., J-modulated exchange behavior.
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