ИСТИНА

Organic carbonates are used in lithium power sources in space and nuclear engineering. For this reason, the radiation resistance of carbonates is of significant interest. In particular, the batteries using organic carbonates as electrolyte are exposed to ionizing radiation, which may crucially affect the functional characteristics of the device during continuous operation. Here we report the study on the mechanism of the radiation-induced processes in propylene carbonate and dimethyl carbonate in low-temperature matrices using EPR and optical absorption spectroscopy. The EPR spectra of the “hole” species (radical cations and/or products of their transformations) were obtained by irradiation of propylene carbonate and dimethyl carbonate in freon matrices at 77 K. The quantum-chemical calculations of the structure and magnetic resonance parameters for the propylene carbonate radical cation were carried out at the MP2 and DFT levels. The comparison of experimental and calculated data makes us conclude that the propylene carbonate radical cation is partially stabilized in the CFCl3 freon matrix at 77 K. On the other hand, the dimethyl carbonate radical cation undergoes intramolecular hydrogen transfer under the same conditions. We suggest that this process occurs likely through a five-membered cyclic transition state resulting in the formation of dystonic radical cation of dimethyl carbonate. The radical anions of both carbonates were found to be stabilized in irradiated neat glassy substances. It was shown that propylene carbonate radical anion decayed upon photolysis with visible light without formation of new paramagnetic species. The dimethyl carbonate radical anion undergoes fragmentation upon photolysis at λ >500 nm due to fragmentation yielding methyl radicals. This work was supported by the Russian Foundation for Basic Research (project no 14-03- 32088).