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

Four novel lanthanide compounds based on the 4-(4-carboxyphenyl)-1,2,4-triazole ligand (Hcpt), {[Pr-2(cpt)(4)(H2O)(10)]center dot 10H(2)O center dot 2ClO(4)} (1), {[Ln(cpt)(2)(H2O)(2)(OH)]center dot 4H(2)O}(n) (Ln = Er(2), Lu(3)), and {[Sm(cpt)(2)-(CH3CH2OH)(H2O)(3)]center dot 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 Ln(3+) 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.