Mononuclear and trinuclear DyIII SMMs with Schiff-base ligands modified by nitro-groups: first triangular complex with a N-N pathway.

Abstract

Using two Schiff-base ligands containing an electron-withdrawing group (NO2), we obtained two mononuclear and two trinuclear complexes with the general formula [Dy(hni)(NO3)(DMF)2]·DMF (1·DMF), [Dy(hni)2(H2O)2]·NO3·EtOH (2·NO3·EtOH), [Dy3(hnc)3(DMF)6] (3) and [Gd3(hnc)3(DMF)6] (4) (H-hni: 2-(hydroxyl-3-methoxy-5-nitrophenyl)methylene(isonictino)hydrazine and H3-hnc: 1,5-bis(2-hydroxy-3-methoxy-5-nitrobenzylidene)carbonohydrazide). Four complexes were confirmed by infrared spectroscopy and single-crystal X-ray diffraction. The crystal structure of complex 3 reveals that the modified Schiff-base ligand provides two different tridentate coordination pockets (ONN and ONO) to encapsulate DyIII with a unique N-N pathway. The magnetic properties of all four complexes have been investigated using dc and ac susceptibility measurements. The frequency-dependent ac susceptibility is indicative of single-molecule magnetic behavior without and/or with an optimum dc field with a relaxation barrier Ueff = 34 K (400 Oe), 19 K (0 Oe) and 80 K (0 Oe) for complexes 1, 2 and 3, respectively.