Magnetic Properties of 1,3,5-Tris[bis(p-methoxyphenyl)ainino]benzene Cation Radicals

In order to pursue the possibility of charge-transfer organic ferromagnets, magnetic properties of the monocationic ClO₄- and BF₄-salts of a triaminobenzene derivative, 1,3,5-tris[bis(p-methoxyphenyl)amino]benzene (TBMAB), were characterized by means of ESR and a Faraday-type magnetic balance. MNDO-PM3 calculations predicted 1,3,5-tris(diphenylamino)benzene (TDAB) dication and trication to be ground-state triplet and quartet, respectively. Thus these triaminobenzenes fulfill the necessary precondition for the appearance of intermolecular ferromagnetic coupling based on so-called McConnell's second model. Negative Weiss constants (-1 to 0 K) and low spin concentrations (7-8 %) were observed for TBMAB-ClO₄ and TBMAB-BF₄, although, according to this rule, intermolecular ferromagnetic coupling is expected to occur for these systems.