American Chemical Society
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Preparation and Spectroscopic, Magnetic, and Electrochemical Studies of Mono-/Biradical TEMPO Derivatives

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journal contribution
posted on 2013-07-05, 00:00 authored by Miroslav Kavala, Roman Boča, Lubomír Dlháň, Vlasta Brezová, Martin Breza, Jozef Kožíšek, Marek Fronc, Peter Herich, Lubomír Švorc, Peter Szolcsányi
A comparison set of mono-/biradical TEMPO derivatives was prepared, novel compounds were fully characterized, and their physicochemical properties were determined. Cyclic voltammetry revealed reversible redox behavior for all studied nitroxides. Moreover, the electron-withdrawing substituents increased the oxidation potential of the respective nitroxides in comparison to electron-donating groups. While EPR spectra of monoradicals in dichloromethane at 295 K reveal the expected three-line signal, spectra of biradicals show more complex features. DFT and MP2 calculations indicate that the EPR splitting pattern of dinitroxide 7 could be explained by its interactions with solvent molecules. In the solid state, mononitroxides 4 and 5 behave as a Heisenberg antiferromagnetic chain, whereas dinitroxides 68 are almost isolated paramagnetic diradicals coupled in an antiferromagnetic manner.