Structural diversity of photoluminescent lanthanide(iii) coordination compounds with an isothiazole derivative

Abstract

Two different series of europium(III), terbium(III) and gadolinium(III) complexes with 4,5-dichloroisothiazole-3-carboxylic acid (HL) were obtained. According to the data obtained from various analysis methods, the first type of coordination compounds with the general formula of [Ln(H₂O)L₂(OAc)]_n was polymer chains, and the second type with the general formula of [Ln₆(H₂O)₁₀L₁₈] was hexanuclear complexes, with central atoms arranged similar to octahedrons. DFT calculations were used to determine the location of the electron density in HOMO/LUMO and the value of the triplet state energy of the ligand molecule. The highest luminescence quantum yield was observed in the case of the hexanuclear terbium(III) complex (24%) with a millisecond luminescence lifetime, while the hexanuclear europium(III) compound (96%) exhibited the highest value of color purity.