Magnetism in organic diradical ion salts based on nitronyl nitroxide

Abstract

Abstract 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 ) + BF 4 - and the diradical anion salt (C 4 H 9 ) 4 N + (2,4-POBNN) − .