Designed synthesis of Co(ii) coordination polymers for evaluation of structural transformations

Abstract

Five coordination polymers constructed from Co(II) salts, N,N′-bis(3-pyridylmethyl)oxalamide (L) and 4,4′-methylenedibenzoic acid (H₂MBA), {[Co(L)(MBA)(H₂O)]·H₂O}_n, 1, {[Co(L)(MBA)]·4H₂O}_n, 2, {[Co(L)(MBA)]·0.25H₂O}_n, 3, [Co(L)(MBA)(H₂O)₂]_n, 4, and {[Co(L)_0.5(MBA)(H₂O)₂]·CH₃OH}_n, 5, are reported, which have been structurally characterized by using single crystal X-ray crystallography. Complexes 1 and 4 have the same formula, but differ in the number of coordinated and cocrystallized water molecules, whereas 2 and 3 form a pair of supramolecular isomers with different numbers of cocrystallized water molecules. Complexes 1 and 4 show interdigitated 2D layers with a (6⁴·8·10)(6)-2,4L3 topology, which differ in the ligand conformations of L and bonding modes of MBA²⁻. Complex 2 shows 2-fold interpenetrated 2D layers with a (6⁴·8·10)(6)-2,4L3 topology and 3 displays a 2-fold interpenetrated 3D framework with a (4·6²)(4·6⁶·8³)-fet topology, whereas 5 is a 1D ladder with a (6²·10)(6)-2,3C1 topology, indicating that the coordination and/or cocrystallization of solvent molecules are important in determining their structural diversity. The structural transformations of 1–4 are also evaluated.