Steric hindrances create a discrete linear Dy-4 complex exhibiting SMM behaviour

Two linear tetranuclear lanthanide complexes of general formula [Ln(4)(L)(2)(C6H5COO)(12)(MeOH)(4)], where HL = 2,6-bis((furan-2-ylmethylimino) methyl)-4-methylphenol, (Scheme 1) and Ln(III) = Dy-III (1) and Gd-III (2), have been synthesized and characterized. The crystal structural analysis demonstrates that two Schiff-base ligands inhibit the growth of benzoate bridged 1D chains, leading to the isolation of discrete tetranuclear complexes due to their steric hindrances. Every Ln(III) ion is coordinated by eight donor atoms in a distorted bicapped trigonal-prismatic arrangement. Alternating current (ac) susceptibility measurements of complex 1 reveal a frequency-and temperature-dependent out-of-phase signal under zero dc field, typical of single-molecule magnet (SMM) behaviour with an anisotropic barrier Delta(eff) = 17.2 K