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 TbIII centers and the magnetic interactions between the spin carriers along the chain induced by substitution on the radical ligand.