1 research outputs found
Single-Molecule Magnet Behavior and Magnetocaloric Effect in Ferromagnetically Coupled Ln<sup>III</sup>-Ni<sup>II</sup>-Ni<sup>II</sup>-Ln<sup>III</sup> (Ln<sup>III</sup> = Dy<sup>III</sup> and Gd<sup>III</sup>) Linear Complexes
New
types of linear tetranuclear Ln<sup>III</sup>-Ni<sup>II</sup>-Ni<sup>II</sup>-Ln<sup>III</sup> (Ln<sup>III</sup> = Dy (<b>1</b>),
Gd (<b>2</b>)) complexes have been prepared using the multidentate
ligand <i>N</i>,<i>N</i>ā²-bisĀ(3-methoxysalicylidene)-1,3-diaminobenzene,
which has two sets of NO and OOā² coordination pockets that
are able to selectively accommodate Ni<sup>II</sup> and Ln<sup>III</sup> ions, respectively. The X-ray structure analysis reveals that the
Ni<sup>II</sup> ions are bridged by phenylenediimine groups forming
a 12-membered metallacycle in the central body of the complex, whereas
the Ln<sup>III</sup> ions are located at both sides of the metallacycle
and linked to the Ni<sup>II</sup> ions by diphenoxo bridging groups.
Phenylenediimine and diphenoxo bridging groups transmit ferromagnetic
exchange interactions between the two Ni<sup>II</sup> ions and between
the Ni<sup>II</sup> and the Ln<sup>III</sup> ions, respectively. Complex <b>1</b> shows slow relaxation of the magnetization at zero field
and a thermal energy barrier <i>U</i><sub>eff</sub> = 7.4
K with <i>H</i><sub>DC</sub> = 1000 Oe, whereas complex <b>2</b> exhibits an S = 9 ground state and significant magnetocaloric
effect (āĪ<i>S</i><sub>m</sub> = 18.5 J kg<sup>ā1</sup> K<sup>ā1</sup> at <i>T</i> = 3 K
and Ī<i>B</i> = 5 T)