Effect of organic polycarboxylates on the architectures of cadmium(II) coordination polymers based on dipyrazino[2,3-f:2′3′-h]quino-xaline: Syntheses, crystal structures, and photoluminescence properties

Three new CdII coordination polymers tuned by the polycarboxylates, namely, [Cd(dpq)(L1)(H2O)] (1), [Cd(dpq)(L2)] (2) and [Cd2(μ3-OH)(dpq)2(L3)]·H2O (3) (dpq = dipyrido[3,2-d:2′3′-f]quinoxaline, H2L1 = 2-carboxymethylsulfanyl nicotinic acid, H2L2 = 2,5-(s-acetic acid) dimercapto-1,3,4-thiadiazole and H3L3 = 5-sulfoisophthalic acid), have been synthesized under hydrothermal conditions and structurally characterized by elemental analysis, IR, and single crystal X-ray diffraction analysis. X-ray analysis reveals that the CdII ions of complex 1 are bridged by L1 anions to form a one-dimensional (1D) linear chain. In complex 2, bimetallic CdII subunits were bridged by L2 anions to generate a 2D (4,4) network, which is stabilized by intra-molecular π–π stacking interactions. In complex 3, the CdII ions are connected by μ3-OH and carboxyl groups from L3 anion to form tetra-nuclear CdII clusters, which are further linked by L3 anions to generate a 2D (3,6)-connected binodal network with a (43)2(46·66·83) topology. The different structures of complexes 1–3 illustrate the great influence of the polycarboxylate ligands on the self-assembly of polymeric coordination architectures. In addition, the thermal and fluorescent properties of complexes 1–3 have been investigated.