Tetranuclear [2×2] Square‐Grid Lanthanide(III) Complexes: Syntheses, Structures, and Magnetic Properties

Abstract

Abstract The reactions of lanthanide(III) nitrate salts (Dy III , Tb III , Gd III , and Er III ) with the aroylhydrazone‐based multidentate ligand 6‐(hydroxymethyl)‐ N′ ‐[1‐(pyridin‐2‐yl)ethylidene]picolinohydrazide (LH 2 ) in the presence of Et 3 N in a molar ratio of 1:1:4 afforded a series of homometallic tetranuclear lanthanide(III) complexes, [Ln 4 (LH) 4 (μ 2 ‐OH) 3 (μ 2 ‐OMe)]4NO 3 · x MeOH · y H 2 O ( 1 , Ln = Dy, x = 2, y = 4; 2 , Ln = Tb, x = 2, y = 4; 3 , Ln = Gd, x = 2, y = 5; and 4 , Ln = Er, x = 3, y = 3). X‐ray diffraction studies revealed that all of the complexes contain a tetracationic [2×2] square‐grid‐like [Ln 4 (μ 2 ‐ OH) 3 (μ 2 ‐ OMe)(μ 2 ‐ O) 4 ] 4+ core, which is assembled by the concerted coordination action of four monoanionic [LH] – ligands along with three μ 2 ‐OH ligands and a μ 2 ‐OMe ligand. All of the lanthanide centers are eight‐coordinate and adopt distorted triangular‐dodecahedral coordination geometries with two different types of coordination environments (6O,2N and 4O,4N). The magnetic susceptibility measurements of the complexes reveal both the presence of all‐antiferromagnetic coupling interactions as well as both isotropic ( 3 ) and anisotropic ( 1 , 2 , 4 ) single‐ion contributions, which do not result in slow relaxation characteristics typical of single‐molecule magnets.