Syntheses, Structures And Properties Of Coordination Polymers Constructed From N-containing Carboxylate Ligands

Over the past two decades, an increasing number of researchers have paid attention to the design and synthesis of various Coordination polymers (CPs) not only owing to their intriguing structural motifs but also for their tremendous potential applications in fluorescence, magnetism, electrochemistry, catalysis, and so on. Recently, hydrothermal in situ ligand synthesis has become a powerful approach in the synthesis of CPs. A number of in situ ligand reactions have been reported, including hydrolysis, tetrazole formation, oxidation-hydrolysis, carbon-carbon bond formation, decarboxylatio and so on. To our knowledge, Lin’s research on the in situ hydro (solvo) thermal hydrolysis of cyano and ester groups is outstanding.Lanthanide based CPs (Ln-CPs), owing to their specific optical and magnetic properties arising from 4/electrons, are fantastic candidates to construct functional compounds with extraordinary properties. One of the significant issues concerning the design of new structure by using lanthanide ions is their coordination preferences. Compared with transition metal, lanthanide elements have higher coordination numbers in the range of 8 to 12 and more flexible coordination geometry which can produce various connected modes. Many different kinds of organic ligands have been used to synthesize porous CPs with attractive topology, and because of these carboxylc acid ligands containing N and O make their coordination way more diverse.We select N-containing carboxylate ligands H3PIDC, Habidc, H^nta as bridging ligands and lanthanide ions as metal centers to construct novel Ln-CPs and study their structures, luminescence and magnetic properties. Under hydrothermal/solvothermal conditions, we have prepared ten Ln-CPs. The main research results are listed as follows:1. Seven novel Ln-CPs have been constructed by various lanthanide ions and 2-(pyridin-2-yl-N-oxide)-1H-imidazole-4,5-dicarboxylate (H3POIDC) ligand, which derived from the partial oxidation of 2-(pyridin-2-yl)-1H-imidazole-4,5-dicarboxylate (H3PIDC) in situ reaction, under hydrothermal/solvothermal conditions. These compounds exhibit two different types of structures with the formula [Ln(H2PIODC)(HPIODC)]-H2O (Ln= Eu (1), Gd (2), Sm (3)), and [Ln(PIODC)·H2O]·H2O (Ln= Eu (4), Gd (5), Tb (6), Dy (7)) by modulating the reaction conditions. Compounds 1-3 with the infinite left-and right-hand helices show 3D supramolecular structure constructing from 1D chains connecting each other through strong hydrogen-bond interactions. Compounds 4-7 show 2D layered structure with sql topology which are built from 4-connected nodes. We get another compound 8 [Eu(ox)2(H3O)]·2H2O based on compounds 4-7 by adding oxalate Into reaction system. Compound 8 is a unique 3D coordination framework. The luminescent spectra show that compounds 1,4,8,3 and 6 display intense red, orange and green luminescence of the typical Eu(Ⅲ), Sm(Ⅲ) and Tb(Ⅲ) ion emission, respectively. Meanwhile, compounds 2 and 5 exhibit intense blue luminescence. At the same time we research the compounds of Eu(Ⅲ) and Tb(Ⅲ)s’fluorescence response in small molecule solvents. The results show that they all show a strong luminescence performance in seven different solvents. And they also show millisecond luminescence lifetimes.2. Two novel 2D layer Sc-CPs:[Sc(Hbidc)(OH)(H2O)]·H2O (9) and [Sc(nta)(H2O)]·H2O (10) have been constructed by two different ligands H3bidc and H3nta respectively, under hydrothermal/solvothermal conditions. Compound 9 has a 1D zipper-like chain built up from dimeric ScO6, moreover, the ligands Hsbidc link with neighbouring zipper-like chain to build up a 2D layer with rhombus windows. Compound 10 shows 2D layered structure with sqI topology which are built from 4-connected nodes. Moreover, compound 9 and 10 exhibit good catalytic activity for the cyanosilylation of aromatic aldehydes, but the catalytic conversion of compound 10 is higher than that of compound 9.