Magnetic properties of purely organic radical magnets, N-(arylthio)-2,4,6-triarylphenylaminyls: Susceptibility and heat capacity measurements

The magnetic properties of N-[(dichlorophenyl)thio]-2,4,6-tris(chlorophenyl)phenylaminyl radical crystals are reported. The stable radical crystals of N-[(2,4-dichlorophenyl)thio]-2,4,6-tris(4-chlorophenyl)phenylammy (1) and N-[(2,4-dichlorophenyl)thio]-2,4,6-tris(3-chlorophenyl)phenylaminyl (2) have shown one-dimensional ferromagnetic behavior which have described using the Bonner-Fisher model with the large ferromagnetic exchange interaction of J/k_B = 14.0 K and J/k_B = 5.7 K, respectively. In addition to these ferromagnetic compounds, N-[(3,5-dichlorophenyl)thio]-2,4,6-tris(4-chlorophenyl)phenylaminyl (3) has also shown the ferromagnetic intermolecular exchange interaction of J/k_B= 1.8 K. For these crystals, we have carried out low-temperature susceptibility and heat capacity measurements below 2 K. Radical 1 has shown a magnetic phase transition at 0.4 K. The susceptibility in the ordered state, however, shows spinflip transition, indicating antiferromagnetic long range ordering. For the ordered state the interchain interactions are also estimated to be J′/k_B = 0.02 K. and J″k/_B = -0.01 K. In order to clarify the electronic structures, ab-initio molecular orbital calculations of their substituted radicals are carried out. The correlation between the magnetic interactions and the electronic structures is discussed.