One-Dimensional Supramolecular Organization of Single-Molecule Magnets

An out-of-plane dimeric MnIII quadridentate Schiff-base compound, [Mn2(salpn)2(H2O)2](ClO4)2
(salpn2- = N,N‘-(propane)bis(salicylideneiminate)), has been synthesized and structurally characterized. The crystal structure reveals that the [Mn2(salpn)2(H2O)2]2+ units are linked through weak H-bonds
(OHwater···OPh) in one dimension along the c-axis, forming supramolecular chains. The exchange interaction
between MnIII ions via the biphenolate bridge is ferromagnetic (J/kB = +1.8 K), inducing an ST = 4 ground
state. This dinuclear unit possesses uni-axial anisotropy observed in the out-of-plane direction with
DMn2/kB = −1.65 K. At low temperatures, this complex exhibits slow relaxation of its magnetization in
agreement with a single-molecule magnet (SMM) behavior. Interestingly, the intermolecular magnetic
interactions along the one-dimensional organization, albeit weak (J‘/kB = −0.03 K), influence significantly
the thermally activated and quantum dynamics of this complex. Thus, unique features such as M vs H
data with multiple steps, hysteresis effects, and peculiar relaxation time have been explained considering
SMMs in small exchange-field perturbations and finite-size effects intrinsic to the chain arrangement. The
magnetic properties of this new complex can be regarded as an intermediate behavior between SMM and
single-chain magnet (SCM) properties.