From Discrete Molecule to One-Dimension Chain: Two New Nitronyl Nitroxide-Lanthanide Complexes Exhibiting Slow Magnetic Relaxation

A mononuclear lanthanide-radical complex [Tb(hfac)(3)(NITPhSCH3)(2)] (1) and a one-dimensional chain complex [Tb(hfac)(3)(NITPhSCH3)](n), (2) {hfac = hexafluoroacetylacetonate, NITPhSCH3 = 2-[4-(methylthio)phenyl]-4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide} have been synthesized. Single-crystal X-ray diffraction studies revealed that compound 1 is a mononuclear complex in which two NITPhSCH3 radicals are coordinated as monodentate ligands to the Tb-III ion through their NO groups to form a tri-spin complex, and complex 2 is a 1D chain structure constructed of Tb(hfac)(3) units bridged by NITPhSCH3 radicals through their NO groups. The temperature dependence of the magnetic susceptibilities of 1 and 2 indicates ferromagnetic coupling between the Tb-III ion and the NITPhSCH3 radical. Frequency-dependent out-of-phase signals of alternating current magnetic susceptibilities were observed at low temperature for both complexes, indicative of slow magnetic relaxation.