Purely organic magnetism of pyridyl-substituted stable thioaminyl radicals

N-[(4-Nitrophenyl)thio]- (1a) and N-[(2,4-dichlorophenyl)thio)]-2,6-dipheny l-4-(3-pyridyl)phenylaminyl (1b), N-[(4-nitrophenyl)thio]- (2a) and N-[(2-d ichlorophenyl)thio]-4-phenyl-2,6-di(3-pyridyl)phenylaminyl (2b) were genera ted by PbO2 oxidation of the corresponding precursors and isolated as radic al crystals. For 1b X-ray crystallographic analysis was performed. The magn etic susceptibility measurements were carried out for the isolated radicals using a SQUID magnetometer in the temperature range 1.8 - 300 K. The susce ptibilities of 1a and 2a were analyzed in terms of a one-dimensional (1D) a ntiferromagnetic (AFM) regular Heisenberg model with exchange interaction o f 2J/k(B)=-63.4 and -17.8 K, respectively, and that of 16 was interpreted i n terms of a 1D AFM alternating Heisenberg model with 2J/k(B) = -12.8 K and alpha = 0.91. On the other hand, that of 2b was explained in terms of a 1D ferromagnetic regular Heisenberg model with 2J/k(B) = 22.4 K.