Novel Uranyl Coordination Polymers Based on Quinoline-Containing Dicarboxylate by Altering Auxiliary Ligands: From 1D Chain to 3D Framework

Abstract

Novel uranyl coordination polymers, UO2(bqdc)­(phen)·H2O (1), [UO2(μ-OH)­(bqdc)­(H2bpy)0.5(H2O)] (2), Na­[(UO2)2(bqdc)3Na­(H2O)2] (3), and [Na­(bqdc)0.5(bpp)­(H2O)] (4) (H2bqdc = 2,2′-biquinoline-4,4′-dicarboxylic acid; phen = 1,10-phenanthroline; bpy = 4,4′-bipyridine; bpp = 1,3-di­(4-pyridyl)­propane), with bqdc2– ligands have been successfully synthesized by hydrothermal reactions and characterized by single-crystal X-ray diffraction, Infrared spectroscopy (IR), thermogravimetric analysis (TGA), and powder X-ray diffraction (PXRD). The topological structures feature 1D chain to 3D framework by altering N-donor ancillary ligands. Compound 1 shows a 1D wave-shaped zigzag chain structure and further extends to a two-dimensional (2D) layer through π···π interactions between the quinoline ring of bqdc2– ligand and benzene ring of phen ligand. The uranium adopts an approximate hexagonal bipyramidal coordination geometry with the equatorial plane warped to the unusual chair conformation. Compound 2 features rectangular-shaped units with space range of 12.28(2) Å × 7.16(3) Å, exhibiting an intriguing 2D uranyl double layered motif formed by 1D ladder chains. The protonated bpy molecules provide space filling and form hydrogen bonds with the layers. Compound 3 is based upon 3D heterometallic frameworks constructed from UO2 2+, Na+, and bqdc2– ligands. The most striking feature of compound 3 is that one sodium ion is located in the middle of two adjacent uranyl ions, forming the trinuclear heterometal clusters (U2Na), which are further connected by bqdc2– ligands to generate UOFs with the cavity size of 10.07(0) Å × 13.86(2) Å. The local 1D structure of compound 3 is similar to the zigzag chain of compound 1. Compound 4 displays 1D chain structure and further extends to 3D framework via hydrogen bond and π···π interactions. Moreover, the electronic structural and bonding properties of the uranyl compounds 1–3 have been systematically explored by density functional theory (DFT) calculations.

An Anionic Uranium-Based Metal–Organic Framework with Ultralarge Nanocages for Selective Dye Adsorption

“…The chemistry of uranium is currently witnessing a speeding up of its historical process owing to the diverse charming structures and various applications, such as ion exchange, gas storage and separation, photochemical catalysis, photoelectronic effects, and nonlinear optics. − Over the past two decades, a large number of efforts have been made to build zero-dimensional (0D) clusters, one-dimensional (1D) chains, and two-dimensional (2D) layers of uranium complexes. − However, three-dimensional (3D) uranium-organic frameworks (UOF) are quite rare, especially for the compounds with ultralarge pore structures. − The main reason may be attributed to the linear geometry of the uranyl ion UO 2 2+ in the axial direction, which restricts the incoming carboxylic ligand to only bonding to the U­(VI) center at the equatorial plane, forming the planar triangular [UO 2 (COO) 3 ] − units. Due to the lack of extension along the axial direction, uranyl coordination complexes usually tend to form chain-like or sheet-like structures rather than 3D porous networks, especially when the planar or rigid organic ligands are utilized. , The flexible multidentate ligands tend to form 3D networks because they can extend the structures along not only the equatorial plane but also the axial direction of the U­(VI) ion through the nonplanar conformations of the ligands.…”

Multifunctional Aromatic Carboxylic Acids as Versatile Building Blocks for Hydrothermal Design of Coordination Polymers

“…For selected examples of CPs, functional properties and applications are also highlighted. A high diversity of aromatic polycarboxylic acids has been extensively applied as multifunctional building blocks in designing novel metal-organic networks [32,33]. Among such building blocks, flexible ligands containing biphenyl and phenyl-pyridine cores with a varying number and position of carboxylic groups as well as distinct locations of N-pyridyl functionality have attracted a special interest [34,35].…”

Semirigid Tripodal Ligand Based Uranyl Coordination Polymer Isomers Featuring 2D Honeycomb Nets

“…As a latecomer, the synthesis and study of actinide-based coordination polymers have also caught increasing attention, benefiting from the flourish of nuclear chemistry in recent years. − As the key element in the nuclear fuel cycle, − uranium has been widely used in the synthesis of actinide-based CPs in light of its unique fission behavior (pure alpha emitting nature and long half-life) as well as its amazing structural and physicochemical properties. − The triatomic species uranyl (UO 2 2+ ) is the most stable species of uranium under the ambient environment. The two axial oxygen atoms force the additional ligands to coordinate in the equatorial plane, often generating tetragonal, pentagonal, and hexagonal bipyramidal coordination geometries. ,− It is worth mentioning that the three carboxylate group coordinated unit [UO 2 (RCOO) 3 ] − can be regarded as the regular triangular secondary building unit (SBU), which can be used to construct specific topological structures containing a three-node unit. ,, In our previous work, we reported two novel (3, 4)-connected UOFs (featuring ctn -type topology or bor -type topology respectively) by combining the uranyl carboxylate SBUs with tetrahedral T d symmetrical H 4 MTB (tetrakis­(4-carboxy­phenyl)­methane) organic linkers . Farha and co-workers obtained a water-stable UOF based on 4,4′,4″,4‴- (pyrene-1,3,6,8-tetrayl)­tetra­benzoic acid (H 4 TBAPy) with pseudo 4-fold symmetry and featuring tbo -type topology .…”