Four Dinuclear and One-Dimensional-Chain Dysprosium and Terbium Complexes Based on 2-Hydroxy-3-methoxybenzoic Acid: Structures, Fluorescence, Single-Molecule-Magnet, and Ab Initio Investigation

Abstract

The unique electronic configurations of lanthanide(III) ions generate abundant electronic energy levels, resulting in the fantastic magnetic and optical multifunctional properties of lanthanide complexes. Here, 2-hydroxy-3-methoxybenzoic acid (H₂MBA) was used to construct four Dy(III) and Tb(III) complexes containing two isostructural dinuclear complexes of [Ln₂(HMBA)₂(MBA)₂(DMF)₂(H₂O)₂]·6H₂O [Ln = Dy (<b>1</b>), Tb (<b>2</b>); DMF = <i>N</i>,<i>N</i>-dimethylformamide] and two other isostructural beltlike one-dimensional-chain complexes of [NH₄][Ln(HMBA)₄] [Ln = Dy (<b>3</b>), Tb (<b>4</b>)]. Fluorescence measurements reveal that H₂MBA can sensitize Dy(III) and Tb(III) characteristic luminescence. Furthermore, complex <b>3</b> can emit white light under UV-light irradiation originating from a dichromatic mixture of a blue emission of H₂MBA and a dominating yellow emission of Dy³⁺ ions. Magnetic susceptibility measurements show that two Dy(III) complexes are single-molecule magnets with anisotropy barriers of 90(2) and 31(5) cm^-1 for <b>1</b> and <b>3</b>, respectively. The magnet-luminescence-structure correlations as well as relaxation pathways are investigated by ab initio calculations and fluorescent spectrometry.