Synthesis, crystal structures and magnetic properties of two Ni-Dy heterometallic complexes with the structural topologies regulated by employing different Schiff base ligands

Regulation of the structural topologies of single molecule magnets (SMMs) is one of the most important approach for enhancing their SMM performance. In this work, we first obtained a Ni2Dy trinuclear complex, [Ni2Dy (Hhmmp)(2) {(py)(2)CO2}(CH3COO)(2)]OH (1, H(2)hmmp = 2- [(2-hydroxyethylimino)methyl]-6-methoxyphenol, (py)(2)C(OH)(2) = the gem-diol form of di-2-pyridyl ketone (dpk)) by employing H(2)hmmp and dpk reacting with Dy (NO3)(3)center dot 5H(2)O and Ni(CH3COO)(2)center dot 4H(2)O in the MeCN solution containing triethylamine. However, when H2hmmp, triethylamine and MeCN in the reaction system of 1 were replaced by 2-(((2-hydroxy-3-methoxyphenyemethylene)amino)-2-(hydroxymethyl)-1,3-propanediol (H4L), N(Me)40I-L5H20 and the mixture of MeCN and N,Ndimethylformamide (DMF), a (NiDy2)-Dy-2 complex, iNi(2)Dy(2)(HL)(2){(py)(2)CO(OH)}(2)(CH3COO)(2)]center dot 2H(2)O (2), was obtained. Structural analysis revealed that two Ni-II and one Dy-III in 1 formed a "V-shaped" topology, while two Ni-II and two Dy-III ions in 2 formed a butterfly-like topology with Ni and Dy-III ions occupied on the body positions and the wing positions, respectively. Additionally, the coordination geometries of Dy-III ion in 1 and 2 square antiprism geometry (D-4d and capped octahedron (C-3v), respectively. Magnetic investigation indicated that 1 exhibits obviously slow magnetic relaxation behavior, with an energy barrier U-eff of similar to 6 K. The orientations of the magnetic anisotropy of Dy-III in 1 and 2 were estimated by Magellan software; the results indicate that few co-ordination atoms were located on the equatorial plane of Dy-III in 1 and 2, which result in 1 and 2 exhibiting poor SMM performance.