Issue 34, 2010

Divalent zinc and cadmium coordination polymers of a new flexible tetracarboxylate ligand: syntheses, crystal structures and properties

Abstract

A series of seven metal–organic frameworks, namely, {[Zn4(bptc)2(bpp)2]·3.5H2O}n (1), {[Zn2(bptc)(bix)]·H2O}n (2), {[Zn2(bptc)(bpe)1.5(H2O)3]·H2O}n (3), [Zn2(Hbptc)(μ3-OH)(4,4′-bpy)]n (4), [Cd2(bptc)(bpa)2(H2O)]n (5), [Cd2(bptc)(bpp)2(H2O)2]n (6), {[Cd4(bptc)2(bix)2(H2O)2]·4.5H2O}n (7) (bptc = 2,2′,3,3′benzophenonetetracarboxylate), have been hydro(solvo)thermally synthesized through the reaction of 2,2′,3,3′-benzophenone tetracarboxylic dianhydride (2,2′,3,3′-bptda) with divalent zinc and cadmium salts in the presence of ancillary nitrogen ligands (bpa = 1,2-bis(4-pyridyl)ethane, bpe = 1,2-bis(4-pyridyl)ethene, bpp = 1,3-bi(4-pyridyl)propane, bix = 1,4-bis(imidazol-1-ylmethyl)benzene, and bpy = 4,4′bipyridine). Due to various coordination modes and conformations of the versatile 2,2′,3,3′-bptc ligand and co-ligands, these complexes exhibit structural and dimensional diversity. In compounds 1–5, M–bptc (M = Zn or Cd) ribbons are connected together through bpp, bix, bpe, bpy and bpa, respectively, to form metal–organic sheets, which are then united together to generate 3D supramolecular structures through interlayer hydrogen bonding, C–H⋯π, or π⋯π interactions. In the structure of 4, the ribbon is formed from interlaced coaxial meso-helical Zn–Hbptc chains, and the meso-helical chains are stabilized by the bpa co-ligand in 5. Compound 6 features a 3D metal–organic framework in which [Cd2(bptc)]nmeso-helices are bridged by bpp ligands to exhibit a (2,6,2)-connected self-penetrating network with the Schläfli symbol (12)(42129164)(4)2. Compound 7 also exhibits a 3D metal–organic framework in which [Cd2(bptc)]n layers are connected by pillared bix ligands to yield a (4,4,8)-connected network with the Schläfli symbol (416612)(4462)(4462)2. Compounds 1 and 7 display intense blue fluorescence emissions at 460 and 465 nm, respectively, and may be suitable as excellent candidates of blue fluorescent materials.

Graphical abstract: Divalent zinc and cadmium coordination polymers of a new flexible tetracarboxylate ligand: syntheses, crystal structures and properties

Supplementary files

Article information

Article type
Paper
Submitted
27 Apr 2010
Accepted
09 Jun 2010
First published
26 Jul 2010

Dalton Trans., 2010,39, 8022-8032

Divalent zinc and cadmium coordination polymers of a new flexible tetracarboxylate ligand: syntheses, crystal structures and properties

S. Zang, R. Liang, Y. Fan, H. Hou and T. C. W. Mak, Dalton Trans., 2010, 39, 8022 DOI: 10.1039/C0DT00374C

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