Structural and magnetic investigations of a binuclear coordination compound of dysprosium(iii) dinitrobenzoate

Abstract

A centro-symmetric binuclear compound of formula [Dy(L)·(CH₃COO)₂·(H₂O)₂]₂ (1) was isolated from the reaction between the 2,4-dinitrobenzoate anion (L) and the tris(acetate) of Dy(III). Single crystal diffraction studies reveal a μ₁–κ²,η¹:η¹ chelating binding mode of L while the binuclear compound is formed by the two bridging (μ₂–κ³,η¹:η²) acetate anions. The nona-coordinated sphere of each Dy(III) ion is filled with a chelating (κ²,η¹:η¹) acetate anion and two terminal water molecules. Static magnetic measurements combined with ab initio SA-CASSCF/RASSI-SO calculations lead to two intramolecular competitive interactions i.e. ferromagnetic exchange interactions (0.04 cm⁻¹) and antiferromagnetic dipolar interactions (−0.5 cm⁻¹). Finally, dynamic magnetic measurements revealed a Single-Molecule Magnet behaviour in a zero-applied magnetic field with an effective energy barrier Δ = 21.5(2) cm⁻¹ and τ₀ = 7(3) × 10⁻⁶ s through Orbach and Quantum Tunnelling of the Magnetization relaxation mechanisms.