Tb and Er dimers based on an asymmetric anilato ligand with slow magnetic relaxation

We report the synthesis, structure and magnetic properties of two dimers prepared with the asymmetric chloronitranilato ligand: 3-chloro-6-nitro-2,5-dihydroxy-1,4-benzo-quinone (C6O4(NO2)Cl)2- and two lanthanoid ions as TbIII and ErIII. The two compounds, formulated as: [Tb2(C6O4Cl(NO2))3(H2O)10]·6H2O (1) and [Er2(C6O4Cl(NO2))3(H2O)10]·6H2O (2) are isostructural and present a dimeric structure where the LnIII ions are connected by a bridging bis-bidentate chloronitranilato ligand. Each metal completes its nona-coordination environment with a terminal bidentate chloronitranilato ligand and five water molecules in a slightly distorted capped square antiprismatic geometry. In addition, these dimers exhibit field-induced slow magnetic relaxation with energy barriers of ca. 5 and 24 K, respectively.