A Series of Lanthanide(III) Coordination Polymers Based on 3,4-Dichloroisothiazole-5-Carboxylic Acid

Europium(III), terbium(III), samarium(III), and gadolinium(III) coordination compounds with 3,4-dichloroisothiazole-5-carboxylic acid of general formula [Ln(H₂O)₂L₂(OAc)]_n are obtained. The complexes are characterized by a number of physicochemical techniques: elemental analysis, powder and single crystal X-ray diffraction (XRD), and IR spectroscopy. According to the single crystal XRD data, these complexes have the polymeric structure formed by the bridging function of acetate ions. In the case of the deprotonated isothiazole derivative, only oxygen atoms of the carboxyl group participate in coordination (two coordination modes: bidentate cyclic or monodentate). When studying the photoluminescent properties of the obtained europium(III) and terbium(III) complexes, it is found that the quantum yield of terbium(III) compounds exceeds 9 times this parameter for the europium(III) complex. The excited state lifetimes are in the millisecond range.