| Investigations of the assembly of metal-organic frameworks (MOFs) have become the robust subject of many current studies, due to not only their versatile architecture, but also their potential application as luminescent and sensory materials. And many of these MOFs also present excellent photoluminescence and magnetic properties. Many multidentate ligands containing N-or O-donors would be expected to be good organic ligands in constructing metal-organic frameworks, due to:(a) the inherent negative charge of carboxylate groups compensate for the charge induced by metal cations and can mitigate the counterion effect; (b) the diverse coordination modes of organic ligand provide the potential for the formation of metal-organic bridging units, which help enhance the robustness of the resulting network architecture.With this paper, the multifunction ligands containing N-or O-donors, were introduced to self-assemble with transition metal ions to present a series of porous metal-organic frameworks with different topology & dimension number. The crystal structure and properties were chacterized, which can be summarized as the following:1. [Ni(2,2',5,5'-bpdc)(H2O)]-H2O(1)&[Ni(2,2',6,6'-bpdc)2]-4H2O(2) were synthesized hydrothermally from 2,2'-bipyridine-5,5'-dicarboxylic acid (2,2',5,5'-bpdc),2,2'-bipyridine-6,6'-dicarboxylic acid(2,2',6,6'-bpdc) as bridging ligand, and transition metal Ni(II) as center metal ion. The crystal structure revealed that the little differences on the carboxyl location attached on the ligands result into their completely different structure, implying the ligands having a modulation on the coordination polymer constructions. there are rich hydrogen bonding interactions formed between the lattice water and the oxygen atoms from the terminal COO- group attached on the corresponding ligands, which play vital role in building the porous crystal structure. The results of thermal gravity analyses show that both the title compounds are thermally stable.2. The rigid 4,4'-bpy and flexible 1,2-bis(4-pyridyl) ethylene are selected as bridging ligands to link Ag(I) cation to build up novel sandwich-like coordination polymers, naming [Ag2(bpy)2(Hda)2](HAc)2-2H2O(3) & [Ag2(dpe)2(da)]-4H2O (4) with the help of 1,1'-biphenyl-2,2'-dicarboxylate acid, by diffusion method under room temperature. The single-crystal diffraction results revealed that both complexes contain fascinating sandwich-like framework, in which the anionic sheets built up from da2- anions and lattice water molecules via rich hydrogen-bonding interactions were inserted between the cationic silver complex layers[AgL]∞(L=bpy & dpe). And the Optical absorption properties of complexes 3 and 4 were determined with UV/Vis/NIR diffuse reflectance spectra.3. [Mn(bpy)(Hbpy)2](V2W4O]9) (5), [Ni(bpy)(Hbpy)2](V2W4O19) (6), and[Co(bpy) (Hbpy)2](V2W4O19)(7) were obtained from the hydrothermal syntheses of the mixture of 4,4'-bpy, WO3, NH4VO3 and transition metal ions (Mn, Co, Ni). The crystal structure revealed that they are isomorphic compounds, in which [V2W4O19]4- and 4,4'-bpy ligand act as the building blocks to join corresponding metal ions M(II) (M=Mn, Ni, Co) via bidentate mode, respectively. The nature of the transition metals is very similar, so their configurations show no significant differences. They are found to have an optical energy gap of 2.1eV from UV-Vis-NIR diffuse reflectance spectrum, and can be used as semi-conductor materials. |
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