Tuning the slow magnetic relaxation with the substituents in anilate bridged bis(dysprosium) complexes.

Dinuclear lanthanide complexes [((HB(pz) 3 ) 2 Dy) 2 (μ-Th 2 An)] (1Dy) and [((HB(pz) 3 ) 2 Dy) 2 (μ-ClCNAn)] (2Dy), based on the hydrotris(pyrazol-1-yl)borate (HBpz 3 - ) scorpionate capping ligand and anilate (An 2- ) bridging linkers, namely homosubstituted dithiophene- and heterosubstituted chlorocyanoanilate, bearing electron-donating and withdrawing substituents at the 3,6-positions of the benzoquinone core, are reported. 1Dy shows an octacoordinated {N 6 O 2 } Dy III ion within a D 4h distorted square antiprismatic coordination, an ideal geometry for Single-Molecule Magnet (SMM) behavior, given its oblate nature, whereas in 2Dy the octacoordinated Dy III ion adopts a D 2d triangular dodecahedron geometry, while maintaining the same {N 6 O 2 } coordination sphere. Both complexes show field-induced single molecule magnet (SMM) behaviour, with tuning of the slow magnetic relaxation as a function of the nature of the substituents at the 3,6-positions of the anilate moiety. A comparison of the Arrhenius fitting parameters for 1Dy and 2Dy supports the hypothesis that square antiprismatic Dy III complexes, as 1Dy, exhibit higher energy barriers. This interpretation is supported by ab initio calculations that also shed light on the crucial role of intermolecular dipolar interactions.