Novel lanthanide complexes constructed from 3, 4-dimethoxybenzoic acid: crystal structures, spectrum and thermochemical properties

Abstract Four novel lanthanide complexes [Ln(3,4-DMOBA) 3 (H 2 O) 2 ]·H 2 O·C 2 H 5 OH (Ln = Sm(1), Tb(2), Dy(3), Ho(4); 3,4-DMOBA = 3, 4-dimethoxybenzoate) have been hydrothermal synthesized and characterized. Structural analyses reveal that adjacent lanthanide ions are connected by 3,4-DMOBA ligands adopting bridging bidentate mode to generate one-dimensional (1-D) structure with the uncoordinated water and ethanol molecules. 1-D structures are linked by hydrogen bonds to form a three-dimensional (3-D) structure, which is rarely observed in lanthanide carboxylic acids complexes. Under the radiation of UV light, complex 2 exhibits the characteristic emission of Tb 3+ ion ( 5 D 4  →  7 F 6-3 ). The thermal decomposition mechanism is investigated by TG-FTIR technology. IR spectra of the evolved gases show that the uncoordinated water and ethanol molecules lose in the first step. And then 3,4-DMOBA ligand is decomposed into H 2 O, CO 2 and other gaseous molecules as well as the gaseous organic fragments.