MAGNETIC-PROPERTIES AND CRYSTAL-STRUCTURES OF 1,5-BIS(4-NITROPHENYL)-3-T-BUTYLVERDAZYL RADICALS

The crystal structures and magnetic properties of 1,5-bis(4-nitropheny l) derivatives of verdazyl free radicals (1-3) are described. The magn etic properties of 1 are explained by the singlet-triplet model with t he coupling constant 2J(AF)/K(B) = 93 K. The susceptibility of 2 was f itted by the Bonner-Fisher model with J(AF)/k(B) = 5.6 K. These result s were in good agreement with the molecular arrangement in the crystal . The susceptibility of 3 obeyed the Curie-Weiss law with the Weiss co nstant theta = -0.5 K. The magnetic intermolecular interactions were s ignificantly suppressed by introducing the substituent at the 6-positi on.