Speaker
Description
Borazine (B$_3$N$_3$H$_6$) is a heterocyclic compound made of alternating boron and nitrogen atoms, known as the "inorganic benzene" because the C=C and B=N bonds are isostructural and isoelectronic. Despite such similarities with benzene, the borazine ring has very different electronic properties due to significant differences in electronegativity between the boron and nitrogen atoms.
We synthesized the first example of borazine functionalized by nitroxide free radicals: the N,N',N''-tris(4 Bromophenyl))-B,B',B''-tris((2,6-dimethyl-4-(N-tert-butyl-N-oxyamino)phenyl)borazine (simplified as Borazine-B-Tris-Nitroxide), in order to study whether the nitroxide radicals could be coupled via the borazine ring and comparatively with other π-conjugated systems.
We will show that the molecule exhibits crystalline polymorphism that differently affects the magnetic properties of these systems. Two phases were isolated and their magneto-structural investigated. To explore where the unpaired electrons are localized in the crystal we completed this work with the mapping of charge and spin densities using high-resolution X-ray and polarized neutron diffractions.
All together, these studies help to rationalize for the first time.the relationships between structure, magnetic properties and exchange interactions involving the borazine core.
Acknowledgments: LABEX iMUST of the University of Lyon (ANR-10-LABX-0064), Région Auvergne-Rhône-Alpes and its programme “Amorçage Europe” for financial support (N°: 23 007040 01 – 40890).
