Magnetic Interaction of Tri- and Di-oxytriphenylamine Radical Cation FeCl₄ Salts

The tetrachloroferrates of the 2,2‘:6‘,2‘ ‘:6‘ ‘,6-trioxytriphenylamine (TOT·+·FeCl4-) and 2,2‘:6‘,2‘ ‘-dioxytriphenylamine (DOT·+·FeCl4-) radical cations were prepared, and their structures, magnetic properties, and the relationship between them were investigated. The TOT·+ moiety had a highly planar structure and packed as a dimer surrounded by tetrachroferrates, which also formed a dimer structure. The magnetic properties of TOT·+·FeCl4- were characterized by strong (2J/kB = ∼ −1.3 × 103 K, H = −2JS1/2·S1/2) and weak (2J/kB = −1.76 K, H = −2JS5/2·S5/2) antiferromagnetic interactions due to the (TOT·+)2 and (FeCl4-)2 structures, respectively. DOT·+ had a twisted form and no dimer formation was observed between the DOT·+'s and FeCl4-'s. Instead, short contacts between the DOT·+ and chlorine atoms and between the DOT·+'s producing a DOT·+ chain were observed. The magnetic properties of DOT·+·FeCl4- were characterized by a 3D magnetic phase transition to an antiferromagnet with TN = ∼8 K.