Magnetism in organic diradical ion salts based on nitronyl nitroxide

Magnetism in organic diradical ion salts prepared from the diradicals, pyridine-2,6-diylbis(nitronyl nitroxide) [(2,6-PYBNN)] and phenol-2,4-diylbis(nitronyl nitroxide) [(2,4-POBNN)], were investigated by using SQUID magnetometers. The diradical cation salt (2,6-PYBNN)+Cl− shows intramolecular ferromagnetic (FM) interaction with the exchange coupling constant J/k = +9.0 K and intermolecular antiferromagnetic (AFM) interaction with the Weiss constant θ = −0.75 K in the low temperature phase below 4.5 K. Although the intramolecular FM interaction is close to that observed in the neutral diradical 2,6-PYBNN, the intermolecular AFM interaction is significantly reduced from J′/k = −57 K due probably to the increase of intermolecular distances by the incorporation of Cl− ions into the salt. We also present and discuss the magnetic behavior in the diradical cation salt (2,6-PYBNN)+BF4- and the diradical anion salt (C4H9)4N+(2,4-POBNN)−.

Magnetism in organic diradical ion salts based on (2,4-POBNN)− and (2,6-PYBNN)+ were investigated by using SQUID magnetometers. The diradical cation salt (2,6-PYBNN)+Cl− shows intramolecular ferromagnetic interaction with the exchange coupling constant J/k = +9.0 K and intermolecular antiferromagnetic interaction with the Weiss constant θ = −0.75 K. The intermolecular interaction in the diradical cation salt is about one hundred times as low as that observed in the neutral diradical (2,6-PYBNN), while the intramolecular interaction is close to that obtained for the neutral radical.Figure optionsDownload as PowerPoint slide