Solvothermal Synthesis and Characterization of Two Cd(II) Coordination Polymers with Isomeric Multi-carboxylate Ligands

In this work two isomeric semi-rigid multi-carboxylate ligands 3,5-bi(3-carboxyphenoxy)benzoic acid (3-H3BCP), 3,5-bi(4-carboxyphenoxy)benzoic acid (4-H3BCP) and two rigid ligands (bis-triazole 4-(4-(4H-1,2,4-triazol-4-yl)phenyl)-4H-1,2,4-triazole (L-1 ), 2-(1 H-pyrazol-3-yl)pyrazine (L-2)) have been employed to react with Cd(II) salts under similar solvothermal reactions. Two novel Cd(II) mixed-ligand coordination polymers, namely, {[Cd-3(3-BCP)(2)(L-1)]center dot 3H(2)O}(n) (1) and [Cd(4-HBCP)(L-2)](n) (2), have been isolated. 1 displays a rare 2D cluster-based network while 2 displays a 3D supramolecular network through weak interactions. Solid-state luminescent properties and thermal analyses of 1 and 2 also have been determined, indicating strong fluorescent emissions and good thermal stabilities. Different coordination modes of two semi-rigid multi-carboxylate ligands and L-1 and L-2 also have been briefly discussed, which also reveal the great potential in the construction of these novel mixed-ligand luminescent frameworks with diverse structural motifs and unique functional properties.