The design and construction of a series of metal–organic coordination polymers based on two isomeric semi-rigid bis-pyridyl-bis-amide ligands and three aromatic polycarboxylates

Abstract

A series of metal–organic coordination polymers, namely, {[Cu₃(4-bpah)₄(1,3,5-BTC)₂]·8H₂O}_n (1), {[Cu₃(4-bpah)₃(1,2-BDC)₃(H₂O)₂]·4H₂O}_n (2), {[Cu(4-bpah)(1,3-BDC)(H₂O)]}_n (3), {[Co(4-bpah)(1,3-BDC)(H₂O)]}_n (4), {[Ni(4-bpah)(1,3-BDC)(H₂O)]}_n (5), {[Zn(4-bpah)(1,3-BDC)(H₂O)]}_n (6), {[Cd(4-bpah)(1,3-BDC)]}_n (7), {[Cd(3-bpah)(1,3-BDC)]·H₂O}_n (8), {[Cu₂(3-bpah)(1,3-BDC)₂]·H₂O}_n (9), where 4-bpah = N,N′-bis(4-pyridinecarboxamide)-1,2-cyclohexane, 3-bpah = N,N′-bis(3-pyridinecarboxamide)-1,2-cyclohexane, 1,3,5-H₃BTC = 1,3,5-benzenetricarboxylic acid, 1,2-H₂BDC = 1,2-benzenedicarboxylic acid, 1,3-H₂BDC = 1,3-benzenedicarboxylic acid, have been synthesized under hydrothermal conditions. The structures of 1–9 have been determined by single crystal X-ray diffraction analyses and further characterized by infrared spectroscopy (IR), elemental analyses, powder X-ray diffraction (PXRD), and thermogravimetric analyses (TGA). Complex 1 displays a 2D (4²·8³·10)(4³·6²·8)₄(4)₂ topological network. Complex 2 shows a 2D (3·4·5·6²·7)₂(3·4²·5²·7) topological framework that contains tri-flexural and left-hand helix chains. Complexes 3–6 reveal a similar 2D sql network with (4⁴·6²) topology. Complexes 7 and 8 show two different 2D double-layer structures with (4²·6)(4³·6·8⁴·10²)(4) and (4²·6·8⁶·12)(4²·6)(8) topology, respectively. Complex 9 exhibits a new 3D 3-nodal topology with the Schläfli symbol (4·6²)₂(4²·6⁴)₂(4²·6⁸·8²·10³). The successful construction of complexes 1–9 implies that using semi-rigid bis-pyridyl-bis-amide ligands can obtain various architectures with small voids. The effect of the isomeric semi-rigid bis-pyridyl-bis-amide ligands and the three aromatic polycarboxylates, as well as the central metal ions on the formation and structures of the title coordination polymers have been discussed. The fluorescent and photocatalytic properties of complexes 1–9 have also been investigated.