Monocapped Square Research Articles

New quaternary R2CoAl4Si2 compounds

Eight new R2CoAl4Si2 silicides (R = Y, Gd-Yb) were synthesized by arc melting, and their crystal structures were studied by X-ray powder diffraction. The compounds were found to adopt the same tetragonal structure type Tb2NiAl4Ge2 (Pearson symbol tI18, space group I4/mmm) and the cell parameters refined to: a = 4.09319 (6), c = 19.3431 (4) Å (R = Y), a = 4.1109 (3), c = 19.425 (2) Å (R = Gd), a = 4.09788 (8), c = 19.3616 (5) Å (R = Tb), a = 4.0850 (1), c = 19.2967 (8) Å (R = Dy), a = 4.07802 (2), c = 19.2575 (2) Å (R = Ho), a = 4.06871 (8), c = 19.2082 (5) Å (R = Er), a = 4.05836 (4), c = 19.1599 (4) Å (R = Tm), and a = 4.06627 (6), c = 4.06627 (6) Å (R = Yb). Isotypic compounds with R = Sm, Lu were not observed under the experimental conditions.The structure type Tb2NiAl4Ge2 is a quaternary variant of the prototype Yb3S2F4 ≡ (NiGe2)Tb2Al4. The structure of the R2CoAl4Si2 compounds can be described as a packing of monocapped square antiprisms [SiAl4R5] and cubes [CoAl8]. It can also be considered as formed by two types of layer containing cubes, stacked along the crystallographic direction [001]. One kind of layer is built of cubes of composition Al8, with every second cube centered by a Co atom, while the other kind of layer consists of slightly deformed empty cubes of composition R4Si4.

Structure and mobility of rare earth ions in interlayer space of montmorillonite: a molecular dynamics study.

Ion adsorption-type deposits (IADs) are the dominant sources of rare earth elements (REEs), in which REEs are mainly enriched in clay minerals. However, the adsorption mechanism of REEs in the interlayer region of clay minerals is still poorly understood. In this study, by using molecular dynamics (MD) simulations, we explored the interlayer structures and dynamics of REEs-intercalated montmorillonite. La3+ and Lu3+ were used as the model cations for light REEs (LREEs) and heavy REEs (HREEs), respectively. It was found that the most thermodynamically stable state for both LREE- and HREE-montmorillonite was the double-hydration state and the corresponding basal spacing was calculated to be ∼16.1 Å. REE ions are located at the middle plane of the interlayer space and adsorbed on the montmorillonite basal surface through hydrogen bonds between its coordination water and the basal oxygens (i.e. as outer-sphere complexes). La3+ was 9-fold coordinated in the interlayer space with a mono-capped square antiprism coordination shell, while Lu3+ was 8-fold coordinated in a square antiprism cage. The mobility of REEs intercalated in the interlayer was significantly reduced compared to the mobility of REEs in aqueous solutions. The microscopic structures, thermodynamic data, and mobility obtained in the present study can help understand the enrichment and mobilization of REEs in IADs, and provide a molecular level basis for developing more efficient extraction techniques.

Lanthanide Squarate Complexes Containing Mono- and Trivalent Thallium.

The synthesis and structural characterization of 16 new thallium lanthanide squarate complexes and 1 new cerium squarate oxalate complex are presented. These new complexes─Tl[Ln(C4O4)(H2O)5]·C4O4 (Ln = La-Nd) (1), Tl3[Ln3(C4O4)6(H2O)6]·8H2O (Ln = Sm-Lu, Y) (2), Tl[Ce(C4O4)2(H2O)6]·C4O4 (3), and [Ce2(C4O4)2(C2O4)(H2O)8]·2H2O (4)─all contain the squarate ligand bound to the trivalent lanthanides with varying coordination modes and denticities. Of the four new groups of complexes prepared in this work, two groupings contain monovalent thallium and trivalent lanthanides, the most common oxidation states for these metals. One complex (3), however, contains trivalent thallium, which is an unusual and challenging oxidation state to stabilize. The Tl3+ cation is formed from in situ oxidation by way of tetravalent cerium (Ce4+/Ce3+, E° = 1.72 V; Tl3+/Tl+ = 1.252 V), leading to the formation of a Tl3+-Ce3+-squarate complex. Additionally, one complex (4) is unique in this work in that it contains both the squarate and oxalate ligands, the latter of which was formed in situ from squarate. Single-crystal X-ray diffraction analysis reveals that 1 and 2 have a 2D structure constructed from either LnO4(H2O)5 monocapped square antiprismatic (CN = 9) metal centers (for 1) or LnO4(H2O)4 square antiprismatic (CN = 8) metal centers (for 2), 3 is a 1D chain structure constructed from CeO3(H2O)6 monocapped square antiprismatic (CN = 9) cerium centers, and 4 is a 3D framework structure constructed from CeO5(H2O)4 monocapped square antiprismatic (CN = 9) cerium centers. 2 and 4 display rare coordination modes for the squarate ligand. Herein, the synthesis, characterization, and structural descriptions of these new complexes are presented.

Structural characteristics of mixed nido‐[Si9−xGex]4− (x=1, 2) Zintl clusters in solution and within solvent crystals

AbstractMixed Zintl‐type anionic clusters of silicon and germanium comprise an important class of potential materials in electronic applications. Herein, we present quantum chemical investigations to describe the mixing behavior of Si and Ge within [Si9−xGex]4− (x=0, 1, 2) Zintl anions that can be considered as precursors for novel Si−Ge materials. To understand the mixing behavior of such clusters in solution, we analyze the molecular clusters at using Density Functional Theory (DFT) and Coupled Cluster methods. Systematic assessment of relative energies of various structural isomers indicates that there is a preference to substitute Si with Ge in the open square of the monocapped square antiprismatic [Si8Ge]4− and [Si7Ge2]4− clusters. Population analysis reveals that the highest negative partial charge is also located at these positions. Investigation of Rb4Si9−xGex(NH3)5 solvent crystals using DFT methods and periodic boundary conditions further elucidates the behavior during crystallization. It is shown that in addition to the favored [Si8Ge]4− open‐square isomers arising in solution, the weak intermolecular interactions in the crystalline environment affect which structural isomers are observed in the crystal structure. The experimentally observed Ge site occupations could be explained by analysis of their energetics. This analysis contributes to the understanding of the mixing behavior of these important building blocks for material design.

Synthesis, Spectroscopic and X-Ray Structure Determination of a New Mononuclear Terbium (III) Complex from the Ligand N,N'-1,5-bis(pyridylmethylidene) Carbonohydrazone (H2L)

In the title compound, [Tb(H2L)2(H2O)3].3Cl.4(H2O).(C2H5OH), the Tb3+ is nine-coordinated in a distorted monocapped square antiprismgeometry by four nitrogen atoms, two oxygen atoms from the ligand molecules of the tridentate N,N'-1,5-bis(pyridylmethylidene) carbonohydrazone) (H2L) and three oxygen atoms of coordinating water molecules. The structure of the complex was elucidated by X-ray diffraction analysis. Suitable crystals were grown by slow evaporation of ethanol solution. The compound crystallizes in the triclinic crystal system with a space group of Pī. The asymmetric unit of the compound contains two neutral ligand molecules, oneterbium ion, three coordinated water molecules, five and half uncoordinated water molecules and one uncoordinated ethanol molecule. In the crystal, the complex cations are linked by hydrogen bonds into layers. These layers, chloride anions and non-coordinating water molecules are connected by O—H···O, O—H···N, O—H···Cl, N—H···O, N—H···Cl and C—H···Cl hydrogen bonds into a three-dimensional structure.

Three-Dimensional Lanthanide-Based Nanoporous Metal–Organic Frameworks for High-Performance Supercapacitors

Lanthanides have been proved to be unprecedented when it comes to organized nanoporous materials with high coordination environment. In the quest to enhance the applications for energy-storage materials, three lanthanide-based metal–organic frameworks (MOFs) have been synthesized by facile hydrothermal conditions using 5-nitroisophthalic acid (H2L) as a ligand, namely, Ce–H2L, Sm–H2L, and Eu–H2L. These nanoporous MOFs consist of nine coordination sites around the lanthanide metal ion giving rise to distorted monocapped square antiprism geometry and 3D crystal structures. The electrochemical measurements demonstrate that charge storage in these MOFs occurs through faradaic redox reactions. The charge–discharge studies show that these nanoporous MOF materials deliver high specific capacity. Ce–H2L, Sm–H2L, and Eu–H2L deliver specific capacities of 625, 356, and 252 C g–1 (1389, 791, and 560 F g–1), respectively, at a current density of 1 A g–1. A symmetric supercapacitor Swagelok device has been fabricated using Ce–H2L as an electrode to further demonstrate the advantage of as-synthesized MOF. The developed symmetric supercapacitor gives a maximum specific energy of 13.6 Wh kg–1 and a maximum specific power of 7110 W kg–1 in the voltage window of 1.425 V. The energy storage trend in these nanoporous materials is Ce–H2L > Sm–H2L > Eu–H2L, which is further supported by the DFT calculations.

Ba3[Sn(OH)6][SeO4]2·3H2O, a hydrated 1:2 double salt of barium hexa-hydroxidostannate(IV) and barium selenate(VI).

Single crystals of tribarium hexa-hydroxidostannate(IV) bis-[selenate(VI)] trihydrate, Ba3H12O17Se2Sn or Ba3[Sn(OH)6][SeO4]2·3H2O, prepared from solid BaSnO3 and aqueous Na2[SeO4] solutions have hexa-gonal (P63) symmetry. The structure consists of four different primary building units: a hexa-hydroxidostannate(IV) ion, two different selenate(VI) ions, all three of point group symmetry C 3, and a mono-capped {BaO9}-square anti-prism of point group symmetry C 1. The secondary building units result from three of the barium coordination polyhedra linked together via common edges. While one of the two tetra-hedral voids formed from these trimeric units is filled by one bidentate, chelating μ2-selenate ion, the other one remains unoccupied as the corresponding second selenate ion only acts as a monodentate, μ1-ligand. SBUs are completed by hexa-hydroxidostannate(IV) ions sharing adjacent edges on the uncapped faces of the three, mono-capped square anti-prisms. These SBUs are arranged into layers via common edges on the uncapped, square faces of the {BaO9} coordination polyhedra in a way that the hexa-hydroxidostannate(IV) ions act as linkage between two neighboring layers.

Synthesis, crystal structure, NMR and near infra-red luminescence studies of nine-coordinate Nd and Yb complexes based on fluorinated β‑diketone and a tridentate antenna chromophore, 2, 4, 6-Tris-(2-pyridyl)-s-triazine

Three nine-coordinate ternary complexes of La(III), Nd(III) and Yb(III) of general composition, [Ln(hfaa)3(tptz)] {hfaa = hexafluoroacetylacetone and tptz = 2, 4, 6-tris-(2-pyridyl)-s-triazine} are synthesised and comprehensively characterised. The X-ray single crystal structure and NMR studies show that the coordination structure of the complexes is nine-coordinate monocapped square antiprismitic in both solid and solution states with LnO6N3 (six oxygen atoms from three hfaa and three nitrogen atoms from one tptz) polyhedra. The complexes are stable in non-coordinating (chloroform) and coordinating (methanol) solvents as indicated by NMR spectrum where no dissociation of any ligand/s is observed. The longitudinal relaxation rate (ρ = 1/T1) is very fast in the cases of paramagnetic Nd(III) and Yb(III) complexes as compared to their diamagnetic La(III) analogue, suggesting their possible use as a relaxation probe in the magnetic resonance imaging. The complexes, on UV light excitation, show characteristic near infra-red emission transitions; 4F3/2→4Ij=9/2, 11/2, 15/2 of Nd(III) and 2F5/2→2F7/2 of Yb(III) ions. The tptz ligand has proved very efficient antenna as it increased the photoluminescence quantum yield of Nd(III) complex. The complexes showed considerable improved photophysical properties in NIR region, which could lead them as significant candidates in developing new materials for more efficient laser and optical amplifier systems, and windows transparent to the biological tissues

Two Bi-MOFs with pyridylmulticarboxylate ligands showing distinct crystal structures and phosphorescence properties

Two Bi-MOFs, [Bi(PDC)(OH)] (Bi-PDC; H2PDC ​= ​2,4-pyridine bicarboxylic acid) and [Bi(PTC)(H2O)2] (Bi-PTC; H3PTC ​= ​2,4,6-pyridine tricarboxylic acid), have been synthesized under almost the same solvothermal condition, respectively. Both Bi-PDC and Bi-PTC were characterized by microanalysis, infrared spectra (IR), thermal gravimetric analyses (TGA), and powder X-ray diffraction (PXRD) techniques. Single-crystal structural analyses indicate that the Bi3+ ions adopt similar coordination sphere of monocapped square antiprism in Bi-PDC and Bi-PTC, while PDC2− and PTC3− ligands display distinct bridging modes through carboxylates and pyridyl groups, leading to Bi-PDC forming three-dimensional (3D) pillared-layer framework and Bi-PTC developing into two-dimensional (2D) layered structure. Two Bi-MOFs emit ligand-centered room temperature phosphorescence due to the heavy atom effect of Bi3+ ion, with lifetime and quantum yield of 0.39 ​ms and 2.49% in Bi-PDC versus 0.57 ​ms and 5.45% in Bi-PTC, and the intense green and orange phosphorescence is visible by naked eyes under ambient condition, and the long-wavelength (orange) phosphorescence Bi-based MOF is seldom reported.

Solvothermal synthesis and crystal structures of two Holmium(III)-5-Hydroxyisophthalate entangled coordination polymers and theoretical studies on the importance of π•••π stacking interactions

Two new Ho(III)-5-hydroxyisophthalates with the formulae; {[Ho(hip)(H2O)5].(NO2).H2O}n (1) and {[Ho4(hip)4(H2O)20].2(hip2−).8H2O}n (2) were solvothermally synthesized by self-assembly of Ho(III)-nitrate with rigid 5-hydroxyisophthalic acid (H2hip) linker. The coordination polymers (CPs) 1 and 2 crystallize in monoclinic P21/c and P21/n space groups, respectively. Both the CPs 1 and 2, shows 1D linear ladder shaped extension with the linkage having the backbone of hip2− moieties. In the both CPs 1 and 2, the Ho centers are nine coordinated. In CP 1, Ho shows distorted tricapped trigonal prismatic geometry while in CP 2, four Ho centres display three different geometries (monocapped square antiprismatic geometry around Ho1 and Ho3; distorted tricapped trigonal prismatic geometry around Ho2 and; distorted monocapped square antiprismatic geometry around Ho4). The organic linker hip2− exhibits only one coordination mode (μ2-κO,O:κO,O). Theoretical calculations have been performed to analyze the antiparallel and parallel π stacking interactions observed in the solid-state structures of coordination polymers1 and 2, respectively. The DFT study is focused on the energetic features of the π-stacking, the influence of the ligand coordination to Ho upon the π-stacking strength and their characterization by the noncovalent interaction plot (NCIplot) index computational tool.

Insights into the Effect of Trans-to-Cis Photoisomerization of a Co-coordinated Stilbene Derivative on the Luminescence of Di-β-diketonate Lanthanide Complexes.

Five lanthanide complexes constructed from a stilbene derivative, (E)-N′,N′-bis(pyridin-2-ylmethyl)-4-styrylbenzoyl hydrazide (HL), and two β-diketonates (2-thenoyltrifluoroacetonate, tta), with or without a trifluoroacetate anion (CF3CO2–), namely, [Ln(tta)2(HL) (CF3CO2)] [LnC45H32F9N4O7S2, Ln = La (1), Nd (2), Eu (3), or Gd (4)] and [Yb(tta)2(L)] (YbC43H31F6N4O5S2 (5), L = deprotonated HL), were synthesized and characterized. Crystals of these five complexes were obtained and analyzed by single-crystal X-ray diffraction. These complexes all belonged to the monoclinic P21/c space group. For La3+, Nd3+, Eu3+, and Gd3+, the central lanthanide ion was nine-coordinate with a monocapped twisted square antiprism polyhedron geometry. The central Yb3+ ion of complex 5 was eight-coordinate with a distorted double-capped triangular prism polyhedron geometry. Among the five complexes, trans-to-cis photoisomerization of the stilbene group in gadolinium complex 4 showed the largest quantum yield. Complexes 2, 3, and 4 showed dual luminescence and photoisomerization functions. The luminescence change of complex 3 was reversible upon the trans-to-cis photoisomerization process. The sensitization efficiencies of luminescent europium complex 3 in acetonitrile solutions and in the solid state were 49.9 and 42.6%, respectively. These medium sensitization efficiencies led to the observation of simultaneous photoisomerization and luminescence, which further confirmed our previous report that photoisomerization of the stilbene group within complexes was related to the lanthanide ion energy level and whether a ligand-to-metal center or ligand-to-ligand charge-transfer process was present. In complexes 1–5, in addition to the intramolecular absorption transition of the ligand itself (IL, πHL–πHL* and πtta–πtta*), the presence of a ligand-to-ligand charge-transfer transition between tta and HL (LLCT, πtta–πHL* or πHL–πtta*) indicated whether the triplet-state energy of HL was able to transfer to the excited energy level of the lanthanide ions, leading to different extents of HL photoisomerization. These results provide an important route for the design of new dual-function lanthanide-based optical switching materials.

Synthesis and characterization of new families of lanthanide perrhenate complexes

The synthesis, structures, and characterization of two new families of trivalent lanthanide perrhenate complexes, [Ln(ReO4)(H2O)4Cl]Cl·H2O (Ln ​= ​La – Nd) (1) and [Ln(ReO4)3(H2O)2] (Ln ​= ​Tb, Ho, Er) (2), along with the expansion of a third known family, [Ln(ReO4)3(H2O)4] (Ln ​= ​Tm, Lu, Y) (3), is presented. Complex 1 is a purely inorganic member of a rare class of compounds known as cationic materials. Single crystal X-ray diffraction analysis reveals that 1 crystallizes in the P21/m space group and is comprised of two-dimensional (2D) sheets constructed from LnO4(H2O)4Cl monocapped square antiprismatic (CN ​= ​9) lanthanide cations, 2 crystallizes in the C2 space group and is a three-dimensional (3D) structure constructed from two crystallographically unique LnO6(H2O)2 square antiprismatic (CN ​= ​8) lanthanide cations, and 3 crystallizes in the P21/n space group and is comprised of one-dimensional chains constructed from LnO4(H2O)4 square antiprismatic (CN ​= ​8) lanthanide cations. This work provides a comprehensive study on essentially the entire lanthanide series (sans Pm) and its complexation with perrhenate at room temperature. The structural features of these complexes exhibit properties influenced by contracting ionic radii and increasing Pearson hardness upon traversing the lanthanide series.

Two new rare-earth orthoborates Ba2CdLn2(BO3)4 (Ln = Tb, Eu) and multicolor tunable emission in the Ba2CdTb2-2xEu2x(BO3)4 (0 ≤ x ≤ 0.2) phosphors

Two new rare-earth orthoborates Ba2CdLn2(BO3)4 (Ln = Tb, Eu) were prepared by the high-temperature solution reactions at 950 °C. The single-crystal XRD analyses showed that they crystallized in the monoclinic space group P21/c and the crystal structures consisted of 3D networks constructed by CdO5 square pyramids (CdO6 mono-capped square pyramids), Tb(Eu)On (n = 7, 8) polyhedra and BO3 planar triangles, with open channels accommodating Ba2+ cations. The IR and Raman studies supported the presence of BO3 groups in the structures and the UV–vis absorption measurements showed the typical Tb3+ and Eu3+ absorption bands arising from their unpaired 4f electrons. In addition, solid solutions Ba2CdTb2-2xEu2x(BO3)4 (0 ≤ x ≤ 0.2) were prepared via the solid-state reaction method. By doping Eu3+ into the Ba2CdTb2(BO3)4 host and varying the doping concentration of Eu3+, tunable colors from green to orange and eventually to red were obtained in the Ba2CdTb2-2xEu2x(BO3)4 phosphors under the excitation at 377 nm. The energy transfer process from Tb3+ to Eu3+ was verified through luminescence spectra and fluorescence decay curves. The above results indicated that the Ba2CdTb2-2xEu2x(BO3)4 phosphors may find potential applications in the field of displays and lighting.

Structures and magnetic properties of five lanthanide-radical complexes constructed by 8-methoxyquinoline substituted tridentate chelating nitronyl nitroxide radical

Five lanthanide complexes [Ln(hfac)3(8-MeOTQ-2-NIT)] constructed by a tridentate chelating 8-methoxyquinoline substituted nitronyl nitroxide radical (Ln ​= ​Gd (1), Tb (2), Dy (3), Ho (4), Er (5), hfac ​= ​hexafluoroacetylacetonate, 8-MeOTQ-2-NIT ​= ​2-(8-methoxyquinoline)-4,4,5,5- tetra-methylimidazoline-1-oxyl-3-oxide) have been successfully synthesized and characterized. The five complexes have similar mononuclear two-spin structures with one LnIII ion and one radical (Rad) in the molecules. And all LnⅢ ions are nine-coordinated in the geometry between mono-capped square antiprism (C4v) and a trigonal bipyramidal (D3h). Alternating current magnetic studies show that Tb and Dy complexes display frequency dependence of out of phase signals indicating the slow magnetic relaxation behavior of single molecular magnets. The ferromagnetic interactions in Gd/Tb-Rad complexes and the very weak antiferromagnetic interactions in Dy/Ho/Er-Rad complexes were estimated by the rough model combining lanthanide single ions approximation and molecular-field approximation.

Lanthanide complexes with 2,6-dimethylbenzoic acid and 2,2′:6′,2′′-terpyridine: Crystal structures, thermochemical property and luminescent behavior

Four 2D lanthanide complexes [Ln(2,6-DMBA)2(terpy)(NO3)]2·4(terpy) (Ln = Sm(1), Eu(2), Gd(3), Tb(4)); 2,6-DMBA = 2,6-dimethylbenzoate; terpy = 2,2′:6′,2′′-terpyridine) were obtained via conventional solution method at room temperature. The crystal structures are characterized by IR, X-ray single crystal diffraction and elemental analysis. The results show that the four complexes are isomorphic, and the coordination number of each metal center is nine, showing a distorted monocapped square anti-prismatic geometry. The complexes 1-4 form a 2D supramolecular framework structure by CH⋯O hydrogen bond interactions. The thermal decomposition mechanism of complexes 1-4 were investigated by the technology TG/DSC-FTIR. The luminescence studies show that the crystal complexes 1, 2 and 4 have good luminescent properties and show good potential as fluorescent materials. The luminescence lifetimes of the Eu(III) and Tb(III) complexes are 1.03 ms and 1.24 ms, respectively.

A lanthanide–mercury compound: preparation and photophysical properties

A neodymium (Nd)–mercury (Hg) complex [Nd(IA)2(H2O)3(NO3)(HgCl2)] n ·2nH2O·nEtOH (1; IA is isonicotinic acid anion) was synthesised and characterised. Compound 1 is of monoclinic system, space group C2/c with a = 25.4224(12), b = 8.1410(3), c = 22.2963(9) Å, β = 90.788(4)°, V = 4614.1(3) Å3, C14H24Cl2HgN3NdO13, Z = 8, M r = 858.09, D c = 2.471 g/cm3, S = 1.120, μ(Mo Kα) = 9.174 mm−1, F(000) = 3256, R = 0.0530 and wR = 0.1288. The mercury (II) (Hg2+) ions are bound by two terminal chloride (Cl−) ions and two nitrogen (N) atoms, displaying a distorted tetrahedral geometry. The neodymium (III) (Nd3+) ion is coordinated with nine oxygen (O) atoms to form a monocapped square antiprismatic polyhedron. Every two neighbouring neodymium (III) ions are interlinked by two μ 3-bridging IA groups to form a one-dimensional (1D) infinite –Nd–IA2–Nd– chain. The 1D chains link to each other through HgCl2N2 tetrahedra and yield a two-dimensional layer. It emits cyan photoluminescence, which should be due to the 4 G 11/2 → 4 I 9/2 transition of the 4f electrons of the neodymium ions. It exhibits Commission Internationale de l’Éclairage chromaticity coordinates of (0.1274, 0.3525). A solid-state diffuse reflectance spectrum unveils that it has a 2.51 eV band gap.

Synthesis and structural characterization of an air and water stable divalent Europium squarate prepared by in situ reduction

A new air and water stable divalent Europium squarate, [Eu(C4O4)(H2O)] (1), has been prepared and structurally characterized. 1 was synthesized by in situ reduction of a trivalent Europium salt using a Zinc amalgam and mild solvothermal heating. The resulting divalent Europium metal centers in 1 are both air and water stable. This demonstrates that this methodology does not require strict anaerobic conditions. A variation on the synthetic conditions used to prepare 1 (sans the Zinc amalgam) yielded two new series of trivalent lanthanide squarates, [Ln2(C4O4)2(C4O3OH)2(H2O)12] (Ln ​= ​La – Nd) (2) and [Ln2(C4O4)3(H2O)8] (Ln ​= ​Dy – Lu) (3), which have also been structurally and spectroscopically characterized. Single crystal X-ray diffraction analysis reveals that 1 crystallizes in the C2/m space group and is a 3D structure constructed from sheets of EuO7(H2O) polyhedra with an unusual triangular dodecahedral (CN ​= ​8) geometry, 2 crystallizes in the P1¯ space group and is a 0D structure constructed from LnO3(H2O)6 monocapped square antiprismatic (CN ​= ​9) metal centers, and 3 crystallizes in the P21/n space group and is a 2D sheet structure constructed from LnO4(H2O)4 square antiprismatic (CN ​= ​8) metal centers. In all structures, the squarate ligands bind to the metal centers with varying, and sometimes uncommon, coordination modes and denticities. Herein, the synthesis, structure, and solid-state UV–vis–NIR spectroscopy of 1, 2, and 3 are presented.

Alkali and alkaline earth coordination polymers constructed from benzene-1,2,4,5-tetracarboxylic acid and flexible dicarboxylate acid ligands: syntheses, structures and spectroscopic and thermal properties.

Two new metal coordination complexes, namely, poly[aqua(μ6-benzene-1,2,4,5-tetracarboxylic acid-κ8O1:O1,O2:O2':O4:O4,O5:O5')(μ-but-2-enedioato-κ2O1:O4)potassium(I)], [K2(C4H2O4)(C10H6O8)(H2O)2]n or [K2(fum)(H4btec)(H2O)2]n, (1), and poly[aqua(μ8-2,5-dicarboxybenzene-1,4-dicarboxylato-κ12O1:O1',O2:O2,O2':O2':O4:O4',O5:O5,O5':O5')(μ-ethanedioato-κ4O1,O2:O1',O2')strontium(II)], [Sr2(C2O4)(C10H4O8)(H2O)2]n or [Sr2(ox)(H2btec)(H2O)2]n, (2) (H4btec = benzene-1,2,4,5-tetracarboxylic acid, H2btec = 2,5-dicarboxybenzene-1,4-dicarboxylate, fum = fumarate and ox = oxalate), have been obtained under hydrothermal conditions by reacting the different alkali and alkaline earth metal salts with H4btec, fumaric acid (H2fum) and oxalic acid (H2ox). Complexes (1) and (2) were structurally characterized by single-crystal X-ray diffraction, IR and UV-Vis spectroscopy, powder X-ray diffraction (PXRD) and thermogravimetic analysis-differential scanning calorimetry (TGA-DSC). Complex (1) displays a two-dimensional (2D) layer with the K+ ion in a distorted pentagonal bipyramidal geometry and exhibits a uninodal 6-connected hxl/Shubnikov plane net (3,6) with {36.46.53} topology. Complex (2) displays a three-dimensional (3D) network structure, in which the Sr2+ ion is in a distorted monocapped square antiprism geometry. The framework possess a binodal (5,8)-connected net with the Schläfli symbol {32.410.58.64.74}{32.46.52}2. The 3D Hirshfeld surfaces and 2D fingerprint plots show that the main interactions are the O...H/H...O intermolecular interactions. Moreover, the thermal decompositions of (1) and (2) in the temperature range 303-1273 K revealed that they both decompose in three steps and transform to the corresponding metal oxide.

Li2Eu3Br2[BO3]2: A New Europium(II) Halide Oxoborate with Yellow Luminescence

The europium(II) oxoborate Li2Eu3Br2[BO3]2 featuring lithium and bromide ions was synthesized by the reaction of Eu2O3 with Li[BH4] as lithium‐ and boron‐ as well as EuBr3 as bromide‐source at 750 °C for 24 h in silica‐jacketed sealed niobium capsules. The yellow, air‐stable and yellow fluorescent compound crystallizes in the trigonal space group R3m (a = 1049.06(7) pm, c = 2993.1(3) pm, c/a = 2.853, Z = 12). The two crystallographically distinguishable Eu2+ cations show either an eightfold coordination as bicapped trigonal prism ([EuO6Br2]12–) or a ninefold coordination as monocapped square antiprism ([EuO5Br4]12–). All oxygen atoms stem from isolated triangular [BO3]3– anions and the Li+ cations reside in octahedral voids provided by both oxygen atoms and Br– anions.

Supramolecular of lanthanide-2,6-dimethylbenzoic acid-2,2′:6′,2″-terpyridine materials: Crystal structures, luminescent property, and thermochemical behaviour

Three mononuclear complexes [Ln(2,6-DMBA)3(terpy)] (Ln = Dy(1), Ho(2), Er(3); 2,6-DMBA = 2,6-dimethylbenzoate; terpy = 2,2′:6′,2″- terpyridine) were synthesized via conventional solution method and characterized by elemental analysis, IR spectra, thermal analysis and single X-ray diffraction techniques. The single-crystal X-ray structures of complex 1–3 are described here, and the complexes are isomorphous and crystallize in the orthorhombic crystal system Pbcn space group. Each Ln(III) ion is nine-coordinated by six O atoms from three 2,6-DMBA ligands and three N atoms from a terpy molecule, which is defined as a distorted monocapped square anti-prismatic geometry. Each adjacent Ln(III) structural unit forms a 2D supramolecular structure through CH⋯O intermolecular hydrogen bonding interaction. The thermal decomposition mechanism of complexes 1–3 were analyzed by TG/DSC-FTIR. The luminescence spectra of Dy(III) complex were studied and the characteristic emission peaks of Dy(III) ion were observed.