Synthesis, Structures And Photoluminescence Of Novel4f/5f Metal Coordination Polymers Constructed From Carboxylate Ligands

It is well-known that carboxylate ligands play an important role in coordination chemistry because of their diverse coordination modes and stronger bonding ability. Therefore metal coordination polymers constructed by carboxylic acid have attracted great interest of chemists. In this paper, we have focused our efforts to explore the synthesis, structures and properties of rigid-flexible lanthanide coordination polymers in order to select the metal centre and organic carboxylate ligands reasonably from a crystal engineering perspective. In the synthesis aspect, we study how to affect the structures on organic ligands, the source of metal, template and pH value and so on. We can further understand the influence of multicarboxylate ligands with diverse coordination modes by controlling the reaction conditions and summarizing the synthetic regularity. On the basis of our groups work, two series of six functional complexes were synthesized under different conditions, four novel lanthanide coordination polymers of which have been synthesized under hydrothermal conditions, with rigid1,2,4,5-benzenetetracarboxylic acid, nicotinic acid as the first ligands and flexible adipic acid as the ancillary ligand; two new uranium coordination polymers of which have been solvently obtained. And complexes1-6were characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, powder X-ray diffraction, thermal analysis. The solid-state photoluminescent properties of3,5and6at room temperature are discussed in detail. The chemical formulas of the six complexes are as following:[CeK(btec)o.5(H20)2](1)[Pr(nic)(ad)-2H2O](4)[Ho(btec)o.5(ad)o.5(H20)](2)[(UO2)2O2(Suc)(2,2’-bipy)](5)[Sm(μ3-O)(nic)3(ad)o.5(H2O)](3)[UO2(BC)2(DMF)](6) Note:H4btec=1,2,4,5-benzenetetracarboxylic acid; H2ad=adipic acid; Hnic=nicotinic acid; H2Suc=succinic acid;2,2’-bipy=2,2’-bipyridine; HBC=benzoic acid; DMF=N, N-dimethylformamideX-ray structure analyses revealed complex1is constructed by1,2,4,5-benzenetetracarboxylic acid. Eight-coordinated europium ion and six-coordinated potassium ion alternately connected by btec4-groups to form a3D structure. Complex2is a3D network assembled by1,2,4,5-benzenetetracarboxylic acid and adipic acid ligands. Complex3is constructed by nicotinic acid and adipic acid ligands. It is a dinuclear units linked by μ3-O. And Sm1and Sm2have different coordination environments. Sm1(Ⅲ) ions are eight-coordinated. Sm2(Ⅲ) ions are nine-coordinated. The nicotinic acid ligand exhibits two types of coordination mode:μ2-η1-η1and μ1-η1-η1. Complex4is constructed by nicotinic acid and adipic acid ligands. The eight O-atoms and one N-atom coordinate to the Pr (Ⅲ) ion to exhibit a slightly distorted dodecahedron configuration. Complex5is constructed by2,2’-bipyridine and succinic acid ligands. It is a dinuclear unit. The dinuclear units are linked by succinic acid to formed ID chain and the ID chain is connected into3D supramolecular network by hydrogen bonds of C-H…O between the carbon atoms of2,2’-bipyridine ligand and the uranyl oxygen atoms. Complex6is constructed by benzoic acid and N, N-dimethylformamide molecule. It is monomeric entities which are further assembled into ID supramolecular network by hydrogen bonds of C17-H17A…O2. And complexes5and6exhibit the interesting photoluminescent properties.