Tuning the magnetization dynamics of Tb^III-based single-chain magnets through substitution on the nitronyl nitroxide radical

Two one-dimensional nitronyl nitroxide radical (NITR)-bridged lanthanide chain compounds, namely [Tb(hfac)₃(NIT-4-ThienPh)]_n (1) and [Tb(hfac)₃(NIT-5-ThienPh)]_n (2), where hfac = hexafluoroacetylacetonate, NIT-4-ThienPh = 2-(4′-phenyl-2′-thienyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide, and NIT-5-ThienPh = 2-(5′-phenyl-2′-thienyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide, were obtained with different NITRs. Alternating-current magnetic susceptibility studies show that both the compounds are single-chain magnets, while a minor change of the site of the phenyl substituent on the NITR significantly influences the magnetization dynamics. The effective magnetization reversal barrier of 1 (53 cm^-1) is more than two times higher than that of 2 (20 cm^-1) and the coercive field of 1 is also much higher than that of 2 because of minor changes in the local coordination symmetry of the Tb^III centers and the magnetic interactions between the spin carriers along the chain induced by substitution on the radical ligand.