Synthesis and characterization of four 2D-3D Zn/Cd/Pb coordination polymers assembled by diverse SBUs and based on isomeric N-heterocyclic multicarboxylate ligands

Abstract Four novel coordination polymers, namely, [Zn3 (L1)2(H2O)2]n·n (CH3CN)·n (H2O) (1), [Cd3 (L1)2(H2O)4]n (2), [Cd3 (L2)2Cl(H2O)2]n·n (H3O) (3), [Pb(HL2)]n (4) were solvothermally synthesized based on isomeric N-heterocyclic multicarboxylate ligands (H3L1 = 5-(2,3-dicarboxylphenoxy)nicotinic acid, H3L2 = 5-(3,4-dicarboxylphenoxy)nicotinic acid). Compound 1 is a 2D layer framework with a (4,8)-connected new topology with the point symbol of (418·610) (45·6)2 based on the [Zn3(COO)4] SBUs (Secondly Building Units). Compound 2 displays a 3D topological network with the point symbol of (3·42·53) (35·46·59·68) and possess the uncommon trinuclear [Cd3 (μ2-H2O) (COO)2] SBUs. Compound 3 shows an interesting (4,4,8)-connected 3D network based on the [Cd3(COO)3] SBUs with the point symbol of (414·613·8) (44·62) (45·6). Compound 4 has the [Pb2(COO)2] SBUs and further spreaded by (HL2)2- to give rise to 2D structure with the uncommon (4,8)-connected sqc169 topology with the point symbol of (412·612·84). H3L1 in 1, 2 and H3L2 in 3, 4 show different coordination modes, respectively, and are found easy to form various metal clusters (secondary building units, SBUs) in final structures. Meanwhile, the solid state luminescence properties of compounds 1–4 were studied at room temperature, and compound 1 showed the high selectivity and sensitivity for Cu2+ ion by a luminescence quenching effect, while 3 can detect nitrobenzene with high selectivity and sensitivity. Moreover, the mechanisms for the luminescence quenching of 1 and 3 have been further studied.