A novel (3,6)-connected Cd coordination polymer based on an ether-linked tricarboxylate ligand: synthesis, topology and luminescence sensing properties in aqueous solution.

A novel three-dimensional coordination polymer, namely, poly[[diaquabis(μ-4,4'-bipyridine)bis{μ-5-[(2-carboxyphenoxy)methyl]isophthalato}tricadmium(III)] dimethylformamide monosolvate 2.5-hydrate], {[Cd(CHO)(CHN)(HO)]·2CHNO·5HO}, was obtained by the reaction of ether-linked 5-[(2-carboxyphenoxy)methyl]isophthalic acid (HL) with Cd salts in the presence of 4,4'-bipyridine (bpy) under solvothermal conditions. In this complex, the Cd centres are connected by the carboxylate ligands to form two-dimensional wave-like layers, which are pillared by bpy ligands and extended into a rare three-dimensional (3,6)-connected sqc27 framework. The complex demonstrated good water stability and strong luminescence emissions. It not only possesses excellent luminescence sensing activities toward Fe and CrO in aqueous solution, but can also distinguish between CrO and CrO by luminescence. Furthermore, it could be simply and quickly regenerated at least five times. A study of the sensing mechanism indicated that luminescence quenching may be related to the energy competition between the complex and sensing analytes.