Cd(ii) coordination polymers constructed from tris-pyridyl-tris-amide and polycarboxylic acid: synthesis, structures and sensing properties

Abstract

Reactions of N,N′,N′′-tris(3-methylpyridyl)trimesic amide (L) and Cd(OAc)₂·2H₂O with various polycarboxylic acids afforded {[Cd₂(L)(1,4-BDC)₂(H₂O)₂]·2H₂O}_n (1,4-H₂BDC = benzene-1,4-dicarboxylic acid), 1, {[Cd(L)(4,4′-BDC)(H₂O)]·H₂O}_n (4,4′-H₂BDC = biphenyl-4,4′-dicarboxylic acid), 2, and {[Cd₃(L)₂(1,3,5-BTC)₂(H₂O)₆]·15H₂O}_n (1,3,5-H₃BTC = benzene-1,3,5-tricarboxylic acid), 3, which have been structurally determined by using single-crystal X-ray diffraction. Complexes 1–3 display 2D layers with (3·8²)₂(3²·4)₂(3⁶·4⁴·5²·8⁴·9⁶·10⁵·11), (4⁴·6²)-sql and (4²·12⁴)₃(4³)₄-3,4L129 topologies, respectively, indicating that the identities of the polycarboxylate ligands involving length and shape play important roles in determining the structural diversity. Complexes 1 and 2 show stabilities in various solvents and display high selectivity toward sensing of Fe³⁺ ions with low detection limits and good reusability of up to five cycles.