Four cobalt(II) coordination polymers based on a flexible N,N′-bis(3-pyridinecarboxamide)-1,6-hexane ligand: Modulation of crystal architectures through the substituent groups of isophthalates

Four cobalt(II) mixed ligand coordination polymers based on the flexible N,N′-bis(3-pyridinecarboxamide)-1,6-hexane (3-dpyh) and four isophthalates with different substituent groups, namely [Co(3-dpyh)(5-HIP)(H2O)3]·H2O (1), [Co(3-dpyh)(5-NIP)]·H2O (2), [Co(3-dpyh)(5-MIP)]·H2O (3) and [Co(3-dpyh)0.5(5-AIP)(H2O)]·2H2O (4), have been hydrothermally synthesized and structurally characterized (5-H2HIP = 5-hydroxyisophthalic acid, 5-H2NIP = 5-nitroisophthalic acid, 5-H2MIP = 5-methylisophthalic acid, 5-H2AIP = 5-aminoisophthalic acid). X-ray diffraction analyses reveal that complex 1 is a chain constructed from a [Co-3-dpyh]n meso-helical chain and 5-HIP anions, in which each 5-HIP anion adopts a monodentate mode coordinating to one Co(II) ion. The isostructural complexes 2 and 3 are assembled from 5-NIP and 5-MIP anions, respectively, featuring a 2D 3,5-connected network with the {42·67·8}{42·6} topology, in which the two carboxyl groups of dicarboxylates exhibit μ1:η1–η1 and μ2:η1–η1 modes. When the 5-AIP anion is utilized in 4, a different 2D (3,4)-connected {42·63·8}{42·6} network is obtained, in which the two carboxyl groups of AIP exhibit μ1:η1–η1 and μ1:η1–η0 modes, and the N atom of AIP also coordinates to the Co(II) ion. The influence of the substituent groups of the isophthalates on the structures has been discussed in detail. The fluorescent, electrochemical and photocatalytic properties of complexes 1–4 have also been investigated.

Graphical abstractFour cobalt(II) coordination polymers based on the flexible bis-pyridyl-bis-amide (3-dpyh) ligand and four isophthalates with different substituent groups have been hydrothermally synthesized. The substituent groups of the isophthalates play important roles in tuning the structures. The fluorescent, electrochemical and photocatalytic properties of complexes 1–4 have been studied.Figure optionsDownload full-size imageDownload as PowerPoint slide