Syntheses, Structures And Properties Of Coordination Polymers Based On Novel Flexible Multi-carboxylate Innersalt Ligands

In recent years, more and more attention has been focused on the construction ofpolymeric frameworks, by reactions of metal salts with organic ligands, due to theirintriguing structures and interesting properties. Among the reported studies, organicligands with carboxylate groups are especially interesting because they can adopt avariety of coordination modes and result in diverse multidimensional architectures. Inaddition, the coordination polymers based on multi-carboxylate acid have importantpotential application value in the photochemical catalysis, adsorption, magnetic, andetc. In this paper, with the aim of construct of novel coordination polymers withintriguing structural motifs and good properties, a novel flexible multi-carboxylateinnersalt Ligands (H3L) and N donor ancillary coligands were selected to prepare21complexes in the cooperation of metal ions. These complexes were characterized withelemental analysis, X-ray single crystal diffraction, IR. Furthermore, their thermalstability, relative phase purity, as well as photoluminescence of some compoundswere studied.In this paper, our main work includes the following two parts:1. Eight metal-organic complexes with novel structure were obtained from thehydrothermal method through the4-carboxy-1-(3,5-dicarboxy-benzyl)-pyridiniumbromide(H3L) ligand, auxiliary ligands (4,4’-bipyridine,1,1′-(1,4-butanediyl)bis(imidazole),1,2-di(pyridine-4-yl)ethylene) with Zn(NO3)2,Cd(NO3)2and Cu(NO3)2, namely:{[Zn(L)(H2O)3]·H2O}n(1),{[Zn(L)]·H2O}n(2),{[Zn(L)(4,4′-bpy)0.5]·2H2O}n(3),{[Cd(L)]·H2O}n(4),{[Cd(L)(1,4-bbi)(H2O)]·H2O}n(5),[Cu(L)(H2O)2]n(6),{[Cu(L)(4,4′-bpy)(H2O)]·5H2O}n(7),{[Cu(L)(bpe)]·6H2O}n(8). Complex1contains two kinds of kinds of helical chains, it displays a3Dsupramolecular structure through π···π interaction by the adjacent benzene rings andbenzene ring with pyridine ring. In Complex2, the isophthalic groups of H3L ligandwith three Zn(Ⅱ) ions to form a2D layer, in the methyl pyridine groups, thecoordination of carboxylic connects the adjacent2D layer to form a3D framework.Compound3displays a3D3-fold interpenetrating framework with pillaredhelical-layers. In Complex4, due to the twist angle of the methy pyridyl group andthe benzene ring, the H3L ligand connects the metal centers to form athree-dimensional network. Complex5is a layered structure with two types of helical layer features a interesting2D�'3D interdigitated architecture. In Complex6, thecopper center with the three carboxy groups of the H3L ligand are taken μ1η1:η0monodentate mode to form a2D layer, and the adjacent2D layer connect a3Dsupramolecular framework by the hydrogen bonding. Complex7displays a2D�'3D interdigitated architecture constructed from2D layers with rectangularlattice unit. Complex8exhibits3D supramolecular framework by the hydrogenbonding with a Z layer shape of double layer structure.2. Thirteen Ln(III) coordination polymers with dinuclear SBUs based on H3Lligand were hydrothermally synthesized. namely:{[La(L)(H2O)2]·2H2O}n(9-10)、{[Nd--2(L)2(H2O)2(NO3)]·5H2O·Br}n(11) and {[Eu(L)(H2O)2]·2H2O·NO-3}n(12-21).The complex9-11crystalizes in the triclinic with space group Pī, all of them are3Dframework. The single-crystal X-ray analyses of the complexes (1221) reveal thatthay all crystalize in the same triclinic space group Pī, and display a3Dsupramolecular structure through π···π interaction. In addition, the luminescentproperties of complex12,13,15and16have also been investigated. And we asloprepared a series of doped Eu-Tb complexes. The power diffraction analysis showsthe structure is similar with complexes1221. The photoluminescence color of theEu3+doped MOF can be turned from green to yellow, orange, and red. At the sametime, the corresponding CIE chromaticity coordinates change from (0.337,0.567) to(0.602,0.356) by changing the doping concentration of the Eu3+ions.