Self-Assembly of Lanthanide Helicate Coordination Polymers into 3D Metal-Organic Framework Structures

A new route for the syntheses of coordination polymers using magnetic influence: syntheses, crystal structures and fluorescence properties

Five coordination polymers [TM1(absa)(H2O)4]n and [TM2(absa)(bipy)(H2O)]n [TM1 = Zn (1), Co (2); TM2 = Zn (3), Co (4), Cu (5); Na2absa = 5,5'-azobissalicylic acid disodium salt; bipy = 4,4'-bipyride] were synthesized by solvent evaporation under a magnetic field. It is evident that magnetic fields bring significant and noticeable changes to the absa2- ligand orientation and the component movement behaviors to construct coordination polymers. The absa2- ligands bind to the metal ions in bridging coordination mode through the carboxylate groups, in addition to the bipy molecules adopting bridging modes. Photoluminescence measurements indicate that the emissions of compounds 1-5 are at 626, 600, 632, 658 and 682 nm in the solid state, respectively.

Probing the Difference in the Complexation of Trivalent Actinides and Lanthanides with a Tridentate N,O-Hybrid Ligand: Spectroscopy, Thermodynamics, and Coordination Modes

Comparatively revealing the complexation behavior of trivalent actinides and lanthanides with functional ligands in aqueous solution is of great importance to enrich our knowledge on the fundamental coordination chemistry of trivalent f-block elements and to control the fate of minor actinides in nuclear fuel cycles. In this work, the complexation of Am(III) and Nd(III), representatives for trivalent actinides and lanthanides, respectively, with a N,O-hybrid ligand 6-(dimethylcarbamoyl)picolinic acid (DMAPA, denoted as HL) was investigated by absorption spectroscopy, calorimetry, X-ray crystallography, and density functional theory (DFT) calculations. Successive formation of 1:1, 1:2, and 1:3 (metal/ligand) complexes of Am(III) and Nd(III) with DMAPA was identified, and the corresponding thermodynamic parameters were determined. The binding strength of Am(III) with DMAPA is slightly stronger than that of Nd(III), and the complexation of Nd(III) with DMAPA is mainly entropy-driven. The crystal structure of the 1:2 Nd(III)/DMAPA complex and the DFT calculation shed additional light on the coordination and structural characteristics of the complexes. In contrast to the Nd-N bond in the Nd(III)/DMAPA complex, the Am-N bond in the Am(III)/DMAPA complex exhibits more covalency, which contributes to the slightly stronger complexation of Am(III) with DMAPA.

Rare-earth metal–organic frameworks: from structure to applications

In the past 30 years, rare-earth metal–organic frameworks (MOFs) have been gaining attention owing to their diverse chemical structures, and tunable properties.

Crystal structure of bis-(μ-2-benzoyl-benzoato-κ(2) O:O')bis-[bis-(2,2'-bi-pyridine-κ(2) N,N')manganese(II)] bis-(perchlorate)

The title compound, [Mn2(C6H5COC6H4COO)2(C10H8N2)4](ClO4)2, comprises a centrosymmetric binuclear cation and two perchlorate anions. In the complex cation, two Mn(II) atoms are bridged by two O atoms of two different 2-benzoyl-benzoate ligands, each Mn(II) atom being further coordinated by two 2,2'-bi-pyridine (bipy) ligands in a distorted octa-hedral environment. Within the binuclear mol-ecule, the Mn⋯Mn separation is 4.513 (7) Å. Inter-molecular C-H⋯O and C-H⋯ π inter-actions link the mol-ecules into a three-dimensional network.

3D lanthanide metal–organic frameworks constructed from lanthanide formate skeletons and 3,5-bis(4′-carboxy-phenyl)-1,2,4-triazole connectors: synthesis, structure and luminescence

3D Ln-MOFs constructed from lanthanide formate skeletons and 3,5-bis(4′-carboxy-phenyl)-1,2,4-triazole connectors show tunable luminescence emission including white light emission.

A novel alkaline earth strontium(II) coordination polymer: poly[hexaaquatetrakis(μ5-pyridine-2,6-dicarboxylato)bis(μ4-pyridine-2,6-dicarboxylato)(μ7-sulfato)heptastrontium(II)]

The title compound, [Sr7(C7H3NO4)6(SO4)(H2O)6]n, has been synthesized by an ionothermal method using the ionic liquid 1-ethyl-3-methylimidazolium ([Emim]Br) as solvent, and characterized by elemental analysis, energy-dispersive X-ray spectroscopy, IR and single-crystal X-ray diffraction. The structure of the compound can be viewed as a three-dimensional coordination polymer composed of Sr(2+) cations, pyridine-2,6-dicarboxylate anions, sulfate anions and water molecules. The compound not only exhibits a three-dimensional structure with a unique coordination mode of the sulfate anion, but also features the first example of a heptanuclear strontium(II) coordination polymer. The structure is further stabilized by O-H···O hydrogen bonds and π-π stacking interactions.

Crystal structure of poly[triaqua-µ2-sulfato-κ4O,O':O'',O'''-pyridine-3,5-dicarboxylato-κ4O,O':O'':O''']cerium(III) monohydrate, C7H11CeNO10S

C7H11CeNO10S, monoclinic, C2/c (no. 15), a = 26.211(4) Å, b = 13.530(2) Å, c = 6.7481(9) Å, β = 92.294(1)°, V = 2391.1 Å3, Z = 8, Rgt(F) = 0.0179, wRref(F2) = 0.0472, T = 296 K.

Crystal structure of 2-(pyridine-4-yl)-1H-imidazole-4,5-dicarboxylic acid, monohydrate, C10H9N3O5·H2O, C10H9N3O5

C10H9N3O5, monoclinic, P21/c (no. 14), a = 5.6030(8) Å, b = 8.422(1) Å, c = 21.521(3) Å, β = 94.809(2)°, V = 1011.9 Å3, Z = 4, Rgt(F) = 0.0419, wRref(F2) = 0.1171, T = 293 K.

Hydrothermal synthesis and crystal structure of novel bis(6-carboxypyridine-2-carboxylato-κ3O2,N,O6)nickel(II) trihydrate, Ni(Hpydc)2·3H2O

The synthesis and crystal structure of the compound bis(6-carboxypyridine-2-carboxylato-κ(3)O(2),N,O(6))nickel(II) trihydrate, Ni(Hpydc)(2)·3H(2)O, with a supramolecular network is reported (H(2)pydc is pyridine-2,6-dicarboxylic acid). The compound has been prepared by hydrothermal methods. The crystal structure has been solved by direct methods using single-crystal X-ray diffraction data collected at 293 K and refined by full-matrix least-squares procedures to a final R value of 0.0323 for 2779 observed reflections. The compound has distorted octahedral geometry around the metal centre. The complex contains two identical singly ionized ligand molecules. The nickel(II) is bonded to four O atoms and two N atoms from the tridentate ligand molecules, which are nearly perpendicular to each other. Hydrogen-bonded interactions create a three-dimensional supramolecular porous network. The supramolecular structure accounts for the porous structure of the compound as is evident from the Brunauer, Emmett & Teller (BET) surface area of 80 m(2) g(-1). Thermal degradation of the compound shows that lattice water molecules give stability to the crystal structure.

2-(1H-Tetra-zol-1-yl)acetic acid monohydrate

The crystal structure of the title compound, C(3)H(4)N(4)O(2)·H(2)O, exhibits O-H⋯O and O-H⋯N hydrogen bonds, which lead to the formation of a two-dimensional network parallel to the bc plane. The dihedral angle between the ring and the carboxylic acid group is 84.6 (14)°.

Poly[[tetra-aqua-bis-(μ(3)-pyridine-2,6-dicarboxyl-ato)(μ(2)-pyridine-2,6-dicarboxyl-ato)dilanthanum(III)] dihydrate]

There are two independent La^III cations in the polymeric title compound, {[La₂(C₇H₃NO₄)₃(H₂O)₄]·2H₂O}_n. One is nine-coordinated in an LaN₂O₇ tricapped trigonal–prismatic geometry formed by three pyridine-2,6-dicarboxyl­ate anions and two water mol­ecules, while the other is ten-coordinated in an LaNO₉ bicapped square-anti­prismatic geometry formed by four pyridine-2,6-dicarboxyl­ate anions and two water mol­ecules. The two La^III cations are separated by a non-bonding distance of 5.026 (3) Å. The pyridine-2,6-dicarboxyl­ate anions bridge the La^III cations, forming a three-dimensional polymeric complex. The crystal structure contains extensive classical O—H⋯O hydrogen bonds and weak inter­molecular C—H⋯O hydrogen bonds. The crystal structure is further consolidated by π–π stacking between pyridine rings, the shortest centroid–centroid distance between parallel pyridine rings being 3.700 (5) Å.