Structural transformations in cobalt(ii) coordination polymers constructed from flexible N,N′-bis(3-pyridylmethyl)sebacoamide and benzene-1,3,5-tricarboxylic acid

Abstract

Hydro(solvo)thermal reactions of cobalt(II) salts, N,N′-bis(3-pyridylmethyl)sebacoamide (L), and benzene-1,3,5-tricarboxylic acid (1,3,5-H₃BTC) in water afforded {[Co(L)(1,3,5-HBTC)]·H₂O}_n1 and {[Co₂(L)₂(1,3,5-HBTC)₂(H₂O)₄]·9H₂O}_n2, whereas those in MeOH and MeOH/H₂O gave {[Co₃(L)(1,3,5-BTC)₂(CH₃OH)₅]·5CH₃OH}_n3 and {[Co_1.5(L)_0.5(1,3,5-BTC)(CH₃OH)(H₂O)₃]·H₂O}_n4, respectively, which have been structurally characterized by using single-crystal X-ray diffraction. Complex 1 displays a two-dimensional (2D) network with the {4²·6⁷·8}{4²·6}-3,5L2 topology, and complexes 2 and 3 are three-dimensional (3D) frameworks with the {6⁵·8}-cds topology and a new topology with a point symbol of {5·6·7}{5·6·8}₂{5²·6²·7·8²·9³}, respectively, while 4 shows a 2D layer with the {6³}-hcb topology, demonstrating that the concentration of the reagent and the solvent system are important in determining the structural diversity. Irreversible structural transformations from 1 to 3 and 2 to 3 under hydro(solvo)thermal conditions are observed and discussed, showing that the flexible nature of the spacer ligands is important in promoting the structural transformations.