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.

Graphical abstractThree novel CoII metal–organic complexes have been hydrothermally prepared by the employment of three dicarboxylate ligands with different spacer length. Complexes 1–3 exhibit three different structures: infinite 1-D chains in 1; 3-D PtS topology in 2 and 5-fold interpenetrated diamondoid topology in 3. The thermal stabilities of complexes 1–3 and fluorescent properties of complexes 2 and 3 have been investigated.Figure optionsDownload full-size imageDownload as PowerPoint slide