Single-Molecule Magnet Behavior and Magnetocaloric Effect in Ferromagnetically Coupled Ln super(III)-Ni super(II)-Ni super(II)-Ln super(III)(Ln super(III)= Dy super(III) and Gd super(III)) Linear Complexes

• Published in: Inorganic chemistry 2014-11, Vol.53 (22), p.12092-12099
• Main Authors: Meseguer, Carlos, Titos-Padilla, Silvia, Hanninen, Mikko M, Navarrete, R, Mota, A J, Evangelisti, Marco, Ruiz, Jose, Colacio, Enrique
• Format: Article
• Language: English
• Subjects: Bridging; Dysprosium; Ferromagnetism; Ion exchangers; Ligands; Magnetization; Metalorganic compounds; Pocket
• ISSN: 0020-1669
• DOI: 10.1021/ic501915j

New types of linear tetranuclear Ln super(III)-Ni super(II)-Ni super(II)-Ln super(III)(Ln super(III)= Dy (1), Gd (2)) complexes have been prepared using the multidentate ligand N,N'-bis(3-methoxysalicylidene)-1,3-diamino benzene, which has two sets of NO and OO' coordination pockets that are able to selectively accommodate Ni super(II) and Ln super(III) ions, respectively. The X-ray structure analysis reveals that the Ni super(II) ions are bridged by phenylenediimine groups forming a 12-membered metallacycle in the central body of the complex, whereas the Ln super(III) ions are located at both sides of the metallacycle and linked to the Ni super(II) ions by diphenoxo bridging groups. Phenylenediimine and diphenoxo bridging groups transmit ferromagnetic exchange interactions between the two Ni super(II) ions and between the Ni super(II) and the Ln super(III) ions, respectively. Complex 1 shows slow relaxation of the magnetization at zero field and a thermal energy barrier U sub(eff)= 7.4 K with H sub(DC)= 1000 Oe, whereas complex 2 exhibits an S = 9 ground state and significant magnetocaloric effect (-[Delta]S sub()m 18.5 J kg super(-1) K super(-1) at T= 3 K and [Delta]B= 5 T).