Multifarious zinc coordination polymers based on biphenyl-3,3′,5,5′-tetracarboxylate and different flexibility of N-donor ligands

Abstract

Based on different flexibility of N-donor and biphenyl-3,3′,5,5′-tetracarboxylate ligands we successfully construct four novel Zn(II) coordination polymers, formulated as {[Zn₂(bptc)(4,4′-bpy) (H₂O)₂]·2H₂O}_n (1), {[Zn(H₂bptc)(bpe)]·2H₂O}_n (2), {[Zn₂(bptc)(bpmp)₂]·2H₂O}_n (3) and {[Zn₂(bptc)(biim-4)₂]·H₂O}_n (4) [H₄bptc = biphenyl-3,3′,5,5′-tetracarboxylic acid, 4,4′-bpy = 4,4′-bipyridine, bpe = 1,2-bis(4-pyridyl)ethane, bpmp = N,N′-bis-(4-pyridyl-methyl) piperazine and biim-4 = 1,1′-(1,4-butanediyl)bis(imidazole)]. Single-crystal X-ray diffraction studies reveal that these four coordination polymers present various topological supramolecular architectures originated from auxiliary N-donor ligands with different flexibility. Complex 1 displays a 3D supramolecular polymer based on the rigid 4,4′-bpy ligands. Complex 2 shows a twofold 2D → 3D framework by parallel polycatenation of undulating 2D sheets based on the semi-rigid bpe ligands. Complex 3 exhibits an unusual 3D self-penetrating coordination framework constructed from the semi-rigid bpmp ligands. Complex 4 is a unique threefold 3D interpenetrated framework based on the flexible biim-4 ligands. In addition, their solid-state luminescent properties also have been systematically investigated.