Magnetic interaction of pyridyl-substituted thioaminyl stable free radicals

N-(2-Pyridylthio)-2,6-diaryl-4-R-phenylaminyls (R = Ph, 4-ClC(6)H(4), MeCO, CN, EtOCO) and N-(4-pyridylthio)-2,6-diaryl-4-R-phenylaminyls (R = Ph, 4-ClC(6)H(4), EtOCO) were prepared and isolated as radical crystals. Their ESR spectra were measured, and the NS and pyridyl nitrogen and anilino meta and pyridyl ortho and para proton hyperfine coupling constants were determined. The spin-density calculations based on the density functional theory were performed by the UBecke 3LYP hybrid method using the STO 6-31G basis set. X-ray crystallographic analyses were performed for three radicals, and their structures were discussed in detail. The magnetic susceptibility measurements were carried out for the nine kinds of isolated radicals with a SQUID magnetometer. One radical showed ferromagnetic coupling (2J/k(B) = 44 K), and the others showed antiferromagnetic behavior. The magnetic interactions observed are explained on the basis of the crystal structures.