With the participation of the Zelinsky Institute N-fluoroalkylpyrazolyl-substituted nitronylnitroxides were obtained and their inherent structure-property correlations were revealed
The introduction of a fluorine atom into a paramagnetic molecule changes the solubility of the compound, increases its volatility, significantly affects the basicity and acidity of functional groups, as well as the tendency to form hydrogen bonds. These properties, individually and all together, can be useful in obtaining thin films by physical vapor deposition, in the development of two-dimensional heterospin structures and caged magnetically active materials. In addition, the transition to polyfluorinated derivatives of organic paramagnets significantly shifts their redox potentials in comparison to non-fluorinated analogues. In combination with an increase in the stability of reduced forms, such paramagnets can find application as effective cathode materials in electric batteries.
With the participation of researchers of the Laboratory of Paramagnetic Materials and Molecular Spin Systems of the ZIOC, the synthesis and the study of the structures and properties of a new series of stable nitronylnitroxides containing N-fluoroalkylpyrazolyl substituents were carried out. It was established that a paramagnet with a difluoromethyl substituent can be reversibly subjected to electrochemical oxidation and reduction; in this case, radicals with fluorinated ethyl substituents are electrochemically oxidized reversibly, but their electrochemical reduction is quasi-reversible. For the first time for organic paramagnets, the study of crystal structures using the energies of pair interaction was carried out. It was shown that, in the crystalline phases of nitroxides, interactions of the С–Н…О type between the oxygen atoms of the paramagnetic fragment and the hydrogen atoms of the pyrazole and/or alkyl substituents are characterized by the highest energy. These interactions predetermine the mutual arrangement of the nitroxide groups and the distances between the oxygen atoms of the paramagnetic centers. It was found that these distances exceed the sum of van der Waals radii, which leads to the implementation of weak exchange interactions of an antiferromagnetic nature in solid phases (|J/kB| £ 2.74 K, H = –2J·S1S2).
Source:
A. Serykh, E. Tretyakov, P. Fedyushin, B. Ugrak, T. Dutova, A. Lalov, A. Korlyukov, A. Akyeva, M. Syroeshkin, A. Bogomyakov, G. Romanenko, N. Artiukhova, M. Egorov, V. Ovcharenko N -Fluoroalkylpyrazolyl-substituted Nitronyl Nitroxides // J. Mol. Struct., 2022, 1269, 133739. DOI: 10.1016/j.molstruc.2022.133739.