Syntheses, structural modulation, and slow magnetic relaxation of three dysprosium(iii) complexes with mononuclear, dinuclear, and one-dimensional structures

Abstract

Three mononuclear, dinuclear and one-dimensional dysprosium(III) complexes based on 3-azotriazolyl-2,6-dihydroxybenzoic acid (H₄ATB) of [Dy(H₃ATB)₃]·3H₂O (1), [Dy₂(H₂ATB)₂(H₂DHB)₂(H₂O)₄]·2CH₃CN·5H₂O (2), and [Dy₂(H₂ATB)₂(DCB)(DMF)₂(H₂O)₂]·4DMF (3) were synthesized and structurally characterized by X-ray single crystal diffraction (H₃DHB = 2,6-dihydroxybenzoic acid, H₂DCB = 1,4-dicarboxybenzene). Complex 1 was used as a precursor to synthesize complexes 2 and 3, and 2 was further used to synthesize 3. Complex 1 is a mononuclear complex, in which the Dy(III) ion is in a nine-coordinated structure surrounded by three tridentate chelate H₃ATB⁻ ligands. Complex 2 displays a dinuclear structure bridged by two μ₂ carboxyl groups of two H₂DHB⁻ ligands and two μ_1,1-O atoms from the phenolic hydroxyl groups of two H₂ATB²⁻ ligands. Complex 3 shows a one-dimensional structure formed by two bridging DCB²⁻ ligands. The magnetic measurements were performed on three complexes 1–3, and they showed different magnetic behavior. Complex 1 shows a field-induced slow magnetic relaxation. Complexes 2 and 3 display distinct slow magnetic relaxation under zero dc field with energy barriers (U_eff) of 26(2) cm⁻¹ and 11(1) cm⁻¹, respectively. The magnetic behavior of three complexes 1–3 was investigated by ab initio calculations.