Intramolecular Spin Exchange in Flexible PEG-based Nitroxide Biradicals in Aqueous Solutions

G. Ionita, G. A. Vorobieva, V. Chechik, A. I. Kokorin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Intramolecular spin exchange in four flexible PEG-based bis-nitroxides was studied by X-band electron paramagnetic resonance (EPR) spectroscopy as a function of temperature and solvent viscosity. A series of biradicals with different lengths of the ethylene glycol bridge connecting the two nitroxide groups was investigated in aqueous and mixed 1:1 i-propanol:water solutions. Conformational transitions in liquid solutions of the biradicals were analyzed, and thermodynamic parameters of the conformational reorganization were calculated from the EPR spectra. Intramolecular distances r between paramagnetic >N–O fragments in biradicals in frozen solutions were calculated and compared with dynamic properties of the biradicals.

Original languageEnglish
Pages (from-to)251-260
Number of pages10
Issue number3
Early online date10 Jan 2015
Publication statusPublished - Mar 2015

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