Aqueous synthesis of sulfonate-functionalized 1,2,4-triazole ligands and their 2D Cd2+ coordination networks: crystal structure and photoluminescent properties.

We have developed a water-based synthesis for the preparation of 4-substituted 1,2,4-triazole ligands with highly polar functional groups. This general synthetic approach has allowed us to prepare two sulfonate functionalized 4-substituted 1,2,4-triazole anions ( L1(-)= 4-(1,2,4-triazol-4-yl)benzenesulfonate; L2(-)= 4-(1,2,4-triazol-4-yl)ethanesulfonate). Reaction of these ligands with cadmium(II) salts leads to the formation of two novel two-dimensional coordination networks of formula [Cd(L)Cl]n (1, L1; and 2, L2), which were structurally characterized by X-ray diffraction. In both compounds, the cadmium ions are bridged by chloride ions and the triazole ligands in a bis-bidentate coordination mode using the N1, N2 atoms from the triazole and two oxygen atoms from the -SO3 group. The photoluminescence studies indicate that the ligand photoemission is retained in these networks.