Crystallochemistry laboratory

Faculty of Chemistry, University of Warsaw

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Opus radicals

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Analysis of the electron density distribution of the dithiadiazolyl radical systems – towards construction of the organic magnets and organic conductors

The main aim of this project was the investigation of the physical and chemical properties of series of molecules containing one unpaired electron – so called dithiadiazolyl radicals (Figure 1). The investigation was performed to find a way to optimize solid state properties of these systems in order to create organic magnets or molecular conducting materials. We were interested in finding the correlation between magnetic/electrical properties of these systems and the distribution of electrons in those molecules. The dithiadiazolyl radicals tend to dimerize in solid state. This unfavorable behavior rend the dimers of radicals to be diamagnetic. In the dimer form they do not exhibit magnetic character. Therefore, we tried to explain the nature of this behavior and how we could prevent it. Different aspects were studied, particularly the influence of the R subsituents and the nature and the magnitude of the interactions between the molecules in the crystal lattice. We found that the majority of spin density (unpaired electrons) were localized on the dithiadiazolyl ring, close to the nitrogen and sulphur atoms. These theoretical findings were compared with the electron density distribution obtained from high resolution X-ray diffraction experiments and a good correlation was found. Both approaches show that the strongest interactions are between the sulphur atoms within a dimer.

This research project confirmed a possibility to get reliable results of the electron density distribution even for the radical systems (for the first time). We observed that we can influence the properties of the dimers: strength of interaction, spin density etc. by using different substituents and/or co-crystallization techniques. That way we can weaken or prevent the dimerization of radicals and preserve the paramagnetic character of these species in solid state. In the future by employing these results one can design organic conductors or magnetic materials using the derivatives of dithiadiazolyl radicals.

radicals
Figure 1. Schematic reprezentation of the dithiadiazolyl radical. Different substituent groups R were tested i.e. phenyl, fluorophenyl, fluoropirydyl etc.

This project was funded by the Polish National Science Centre within the OPUS programme, Grant No. UMO-2012/05/B/ST4/03339.

Last Updated on Monday, 09 May 2016 10:14  


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