Zn(II), Cd(II) and Hg(II) halide coordination polymers supported by bis-pyridyl-bis-amide: structural diversity and structural transformation

Abstract

Reactions of metal halide with N,N’-bis(3-pyridylmethyl)oxalamide (L1), N,N’-bis(4-methylpyridyl)oxalamide (L2) or N‚N'-bis(3-methylpyridyl)adipamide (L3) afforded {[ZnI2(L1)]⋅2DMF}n, 1, [ZnI2(L1)]n, 2, [CdI2(L1)]n, 3, and [HgI2(L1)]n, 4, [HgI2(L2)]n, 5, [Hg2I4(L3)], 6, [CdI2(L3)]n, 7, 1D-[CdBr2(L1)2]n, 8, 2D-[CdBr2(L1)2]n, 9, and [Cd2Br2(ox)(L1)2]n (ox- = oxalate), 10, whereas reaction of Cd(CH3COO)2·2H2O with L1 gave {[Cd(ox)(L1)]·4H2O}n, 11, which have been structurally characterized by using single-crystal X-ray diffraction. Complexes 1 and 2 form a pair of supramolecular isomers, giving a 1D concavo-convex chain and a 1D zigzag chain, respectively, whereas, 3, 4, 5 and 7 are 1D zigzag chains and 6 is a dinuclear complex, demonstrating that the solvent identity and the length of the spacer ligand are important in determining the structural diversity. Complexes 8 and 9 are another pair of supramolecular isomers, adopting a 1D looped-chain and a 2D layer with the (44⋅62)-sql topology, respectively. Complex 10 is a 3D framework with the (66)-dia topology and 11 is a 2D layer with the (44⋅62)-sql topology. Moreover, complexes 1 and 2 display irreversible structural transformation upon solvent removal, whereas temperature-dependent structural transformations from 8 to 9, 8 to 10 and 9 to 10 are observed.