Bi‐Compartmental Schiff‐Base with Peripheral Ester Functionalization: Synthesis and Magnetic Behavior of Bimetallic Zn‐Ln Complexes (Ln = Dy, Tb, Gd)

Abstract

A novel ester-functionalized bi-compartmental Schiff-base ligand and its dinuclear Zn-Ln complexes [Ln = Dy (1), Tb (2), Gd (3)] are reported herein. Athough electron-withdrawing substituents at the para position of the phenol moieties do not change the coordination environment of the Ln centers in comparison with the nonfunctionalized ligand, they have a clear steric effect on the crystal packing and alter the coordination strength of the central ligand core. This is illus-[a] CNRS

Syntheses, Structures, and Magnetic Properties of Symmetric and Dissymmetric Ester‐Functionalized 3d‐4f Schiff Base Complexes

“…In this situation, a ZnDy complex was found to exhibit slow relaxation of its magnetization, while its nonfunctionalized homologue did not. [8] In an extension of this preliminary result, we verified that the classical alteration of the 3d ion and the accommodation of different Ln salts also apply for this particular ligand. Moreover, we considered the flexibility of the ester function to anchor an additional functionality, such as chirality, to the complex.…”

“…This substitution at the periphery resulted in a lengthening of the phenoxo–Ln bonds, suggesting a sensible modification of the ligand field sensed by the metal ion. In this situation, a ZnDy complex was found to exhibit slow relaxation of its magnetization, while its nonfunctionalized homologue did not . In an extension of this preliminary result, we verified that the classical alteration of the 3d ion and the accommodation of different Ln salts also apply for this particular ligand.…”

“…As anticipated, the Zn ion is in a square‐pyramidal environment defined by the inner N2O2 cavity of the ligand and the N atom of a pyridine located in the apical position. The Dy ion is linked to the Schiff base by the four O atoms of the outer cavity with two sets of bond lengths (average Dy–O phenoxy 2.3260 Å and average Dy–O methoxy 2.5036 Å) as classically reported . The ten‐coordination sphere is completed with six O atoms from three bidentate nitrates (average Dy–O nitrate 2.4766 Å) and displays a polyhedral shape close to a spherocorona (see Supporting Information).…”

“…Subsequent insertion of the Ln ions into the O2O2 cavity was achieved in CHCl 3 or CH 2 Cl 2 . Such poorly coordinating solvents were required, because the electron‐withdrawing ester groups lessen the complexation strength of the phenol O atom with rare‐earth ions . Single crystals suitable for X‐ray diffraction for Cu d L COOMe and 1 – 5 were obtained by diffusion of diethyl ether (for Cu d L COOMe and 1 – 4 ) or hexane (for 5 ) into a solution of the complexes either in CH 2 Cl 2 or CHCl 3 (see Experimental Section).…”

“…The synthesis of the Schiff base ligands, the 3d complexes, and the 3d‐4f complexes is presented in Scheme . The 3‐formyl‐4‐hydroxy‐5‐methoxybenzoic acid, its methyl ester, methyl 3‐formyl‐4‐hydroxy‐5‐methoxybenzoate, and the Schiff base H 2 L COOMe were prepared according to a reported procedure . The [CuLPy]ClO 4 complex (Py = pyridine, L = half‐unit ligand corresponding to the monocondensation of 2,2‐dimethyl‐1,3‐diaminopropane with o ‐vanillin) was prepared according to a reported procedure .…”