Synthesis, Structures And Properties Of Complex Based On Pyridine-dicarboxylic Acid

The design and construction of metal organic frameworks (MOFs) have received much attention in the area of crystal engineering due to their potential applications in many fields such as photochemical area, catalysis, magnetism and adsorption. In order to get novel MOFs, much effort should be devoted not only to selecting organic ligands, but also to investigating the factors that have important effect on the structures of MOFs:metal ions, pH value, temperature, solvent, template agents. Taking these characteristics into consideration, we choose pyridine-dicarboxylic acid as ligand in this paper, because it has O atoms and N atom which result in more varied coordination modes with metal ions, and then MOFs with fascinating structures and properties could be prepared; on the other hand, we have a preliminary research on the aforementioned factors(template agent, solvent, pH vablue).Firstly, we chose5-(pyridin-4-yl)isophthalic (H2L) as a target ligand and employed the organic molecule with reactive functional groups (4,4’-bipyridyl, cyanoacetic acid,2,3-Pyridinedicarboxylic acid) as template agents in the DMF-EtOH-H2O solvent system to prepare three novel complexes, namely,[Mn3(L)2(HCOO)2(H2O)2]n (1),{[Co(L)(H2O)]·H2O}n (2) and [Co2(L)2(DMF)]n (3). Besides that, two other complexes{[Mn2(L)2(H20)4]·5H2O}n (4) and [Co(L)(EtOH)(H2O)]n (5) were isolated when we didn’t add template agent in the reaction system. These complexes showed different structures by single crystal X-ray diffraction.1is a3D framework built from trinuclear linear manganese clusters;2shows a organic network that contains Co(II) dinuclear and generate a2D double-layered framework via carboxylate oxygen bridges;3exhibits a3D framework that consists of Co(Ⅱ) dinuclear and L2-ligands;4features an infinite2D network and further results in a3D supramolecule via hydrogen bond interactions;5contains two independent2D network and the neighbouring2D layers can be further linked to yield a2D double-layered supramolecule via hydrogen bonding between aqua ligands and coordinated carboxylate O atoms. The magnetic studies of1-3reveal weak antiferromagnetic interactions mediated by pyip2+. Compared with4and5,1-3exhibit relative complex structures and intriguing properties. Template-assistant method is a potential approach to obtain complexes with specific structures and properties that may be difficult to access by routine synthetic methods.Secondly, we chose5-(3’-carboxylphenyl) nicotic acid (H2L1) as a target ligand and prepared two novel complexes [Zn(L1)NH(CH3)2]n(6),[Zn(L1)]n (7) via solvent-induced synthesis. The use of DMF as solvent led to6; While7was obtained by using DMA as solvent. Another complex [Co1.5(L1)(DMA)(PTA)o.5]n (8) was yield not only by using mix solvent(DMA-CH3OH) and adjusting PH value via NaOH, but also by employing PTA as auxiliary ligand.6shows an infinite2D network;7is a3D chiral coordination made up of Zn(Ⅱ) dinuclear and L12-ligands;8exhibits a3D framework consisting of Co(II) dinuclear. We found that the solvent and pH value had important effects on the structures of complexes, and the results provided us with ideas and guidance in our later work.