Lanthanide-based coordination compounds based on 4-(4-carboxyphenyl)-1,2,4-triazole: synthesis, structures, Hirshfeld surface and luminescence properties

Abstract

Four novel lanthanide compounds based on the 4-(4-carboxyphenyl)-1,2,4-triazole ligand (Hcpt), {[Pr₂(cpt)₄(H₂O)₁₀]·10H₂O·2ClO₄} (1), {[Ln(cpt)₂(H₂O)₂(OH)]·4H₂O}_n (Ln = Er(2), Lu(3)), and {[Sm(cpt)₂(CH₃CH₂OH)(H₂O)₃]·ClO₄}_n (4), have been obtained under hydrothermal conditions and further characterized by elemental analysis, single-crystal X-ray diffraction and thermogravimetric analysis. Compound 1 exhibits a discrete dinuclear structure constructed by one cpt⁻ ligand coordinated to two Pr³⁺ ions and another cpt⁻ ligand coordinated to more than one Pr³⁺ ion. Compounds 2 and 3 are isomorphous and every cpt⁻ ligand coordinates to two Ln³⁺ ions, resulting in a polymeric 1-D chain structure. Different from the above compounds, the nitrogen atoms of triazole are also involved in the coordination of compound 4. One cpt⁻ ligand coordinates to two Sm³⁺ ions and another cpt⁻ ligand coordinates to more than one Sm³⁺ ion, meanwhile, the nitrogen atoms of triazole coordinate to the third Sm³⁺ ion, resulting in a 2-D polymeric network structure. The luminescence properties of compound 4 were characterized, and the results revealed that it exhibited characteristic Sm³⁺ emission in the yellow region.