Assembly of novel phenanthroline-based cobalt(II) coordination polymers by selecting dicarboxylate ligands with different spacer length: From 1-D chain to 3-D interpenetrated framework

Three novel CoII coordination polymers [Co(Dpq)2(1,4-NDC)0.5] · (1,4-HNDC) (1), [Co(Dpq)(2,6-NDC)] (2), and [Co2(Dpq)2(BPEA)4(H2O)] · H2O (3) have been obtained from hydrothermal reaction of cobalt nitrate with the mixed ligands dipyrido[3,2-d:2′,3′-f]quinoxaline (Dpq) and three dicarboxylate ligands with different spacer length [1,4-naphthalene-dicarboxylic acid (1,4-H2NDC), 2,6-naphthalene-dicarboxylic acid (2,6-H2NDC) and biphenylethene-4,4′-dicarboxylic acid (BPEA)]. All these complexes are fully structurally characterized by elemental analysis, IR, and single-crystal X-ray diffraction analysis. Single-crystal X-ray analysis reveal that complex 1 is infinite one-dimensional (1-D) chains bridged by 1,4-NDC ligands, which are extended into a two-dimensional (2-D) supramolecular network by π–π interactions between the Dpq molecules. Complex 2 is a distorted three-dimensional (3-D) PtS network constructed from infinite Co–O–C rod units. Complex 3 has a 5-fold interpenetrated 3-D structure with diamondoid topology based on dinuclear [Co2(CO2)2(μ2-OH2)N4O2] units and BPEA molecules. The different structures of complexes 1–3 illustrate the influence of the length of dicarboxylate ligands on the self-assembly of polymeric coordination architectures. In addition, the thermal properties of complexes 1–3 and fluorescent properties of complexes 2 and 3 have been investigated in the solid state.