Divalent zinc and cadmium coordination polymers of a new flexible tetracarboxylate ligand: syntheses, crystal structures and properties
作者:Shuang-Quan Zang、Ran Liang、Ya-Juan Fan、Hong-Wei Hou、Thomas C. W. Mak
DOI:10.1039/c0dt00374c
日期:——
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.
一系列七种
金属有机框架,即[Zn4(bptc)2(bpp)2]·3.5 }n (1), [Zn2(bptc)(bix)]·
H2O}n (2), [Zn2(bptc)(bpe)1.5( )3]· }n (3), [Zn2(Hbptc)(μ3-OH)(4,4′-bpy)]n (4), [Cd2(bptc)(bpa)2( )]n (5), [Cd2(bptc)(bpp)2( )2]n (6), [Cd4(bptc)2(bix)2( )2]·4.5 }n (7) (bptc = 2,2′,3,3′
二苯甲酮四
羧酸酯),通过2,2′,3,3′-
二苯甲酮四
羧酸二酐(2,2′,3,3′-bptda)与二价
锌和
镉盐在辅助氮
配体(bpa =
1,2-双(4-吡啶基)乙烷,bpe = 1,2-双(4-
吡啶基)
乙烯,bpp = 1,3-双(4-
吡啶基)
丙烷,bix = 1,4-双(
咪唑-1-基甲基)苯,和bpy = 4,4′联
吡啶)的存在下反应,通过
水(溶剂)热合成得到。由于多功能的2,2′,3,3′-bptc
配体和共
配体的各种配位模式和构象,这些配合物表现出结构和维度的多样性。在化合物1-5中,M-bptc(M = Zn或Cd)带通过bpp,bix,bpe,bpy和bpa分别连接在一起,形成
金属有机片层,然后通过层间氢键、C-H⋯π或π⋯π相互作用连接在一起,生成三维超分子结构。在结构4中,带由交织的同轴介观螺旋Zn-Hbptc链形成,并在5中通过bpa共
配体稳定介观螺旋链。化合物6具有三维
金属有机框架,其中[Cd2(bptc)]n介观螺旋通过bpp
配体桥接,展现出(2,6,2)-连接的自穿透网络,具有Schläfli符号(12)(42129164)(4)2。化合物7也展现出一种三维
金属有机框架,其中[Cd2(bptc)]n层通过支柱状bix
配体连接,产生(4,4,8)-连接的网络,具有Schläfli符号(416612)(4462)(4462)2。化合物1和7分别在460和465 nm处显示出强烈的蓝色荧光发射,可能是优秀的蓝色荧光材料候选者。