Polycarboxylate-assisted assembly of cobalt(II) metal–organic coordination polymers from a “V”-shaped tri-pyridyl-bis-amide ligand

Abstract

The aim of this study was to explore the influence of the position and angles of carboxyl groups of polycarboxylates on constructing coordination polymers. Three Co(II) metal–organic coordination polymers based on a tri-pyridyl-bis-amide ligand, namely [Co(L)(1,2-BDC)(H2O)2]·2H2O (1), [Co(L)(1,4-BDC)(H2O)2]·2H2O (2) and [Co(L)2(BTEC)0.5]·H2O (3) (L = N,N′-bis(pyridine-3-yl)pyridine-2,6-dicarboxamide, 1,2-H2BDC = 1,2-benzenedicarboxylic acid, 1,4-H2BDC = 1,4-benzenedicarboxylic acid, H4BTEC = 1,2,4,5-benzenetetracarboxylic acid), have been obtained by tuning the auxiliary polycarboxylate ligands. Structural analyses reveal that complexes 1–3 display diverse structures. Complex 1 displays a meso-helical chain linked by L ligands, which is further extended into a three-dimensional supramolecular framework through hydrogen-bonding interactions. The 1,2-BDC with a chelating coordination mode only acts as the hydrogen bond acceptor. In complex 2, the 1,4-BDC anions connect adjacent Co(II) atoms to form a linear chain, which is connected by hydrogen-bonding interactions to construct a 3D supramolecular network. Complex 3 exhibits a chain, which is composed of left-/right-handed Co-L helical chains and Co-BTEC linear chain. The 1D chains are ultimately extended into a two-dimensional supramolecular network by hydrogen-bonding interactions. Moreover, the thermal stability and the fluorescent properties of the title complexes and the electrochemical behaviors of a bulk-modified carbon paste electrode with complex 2 have been investigated at room temperature.