Strongly photoluminescent Eu(III) tetrazolate ternary complexes with phosphine oxides as powerful sensitizers

The Eu(III) cation forms electrically neutral photoluminescent complex with 5-(2-pyridyl-1-oxide)tetrazolate (PTO) anion. Although the photoluminescence properties of such tertiary Eu(III) and Tb(III) complexes were not as high (13 and 31% photoluminescence quantum yield, respectively) as reported for other diketonate lanthanide complexes probably because of high number of nitrogen atoms involved in PTO which leads to attachment of water molecules, reducing the luminescence quantum yield with vibrational and rotational quenching. Here, we report the removal of quencher molecules from the coordination sphere of tris–europium tetrazolate oxide complex by replacing them with various phosphine oxides which leads to improved photoluminescence quantum yield for the complexes by acting as auxiliary co-ligands with that of the main antenna 5-(2-pyridyl-1-oxide)tetrazolate. The coordination sphere in these complexes can be complemented by aromatic phosphine oxides to provide highly photoluminescent Eu(III) complexes. The highest quantum yield was 38% in 3 [Eu(PTO)₃·DPEPO](H₂O)₅ containing bis(2-(diphenylphosphino)phenyl) ether oxide (DPEPO) as compared to tris–europium complex with 5-(2-pyridyl-1-oxide)tetrazolate.     

Molecular Chains in the Crystals of a Calcium(II) Complex with Pyridine-3,5-Dicarboxylate (Dinicotinate) and Water Ligands

The crystal of pentaqua (catena-pyridine-3,5-dicarboxylato-O,O) calcium(II) contain zigzag molecular chains composed of Ca ions linked by two bridging oxygen atoms, each donated by one carboxylate group [Ca-O1 2.353(2) Å, Ca-O3^III 2.334(1) Å]. The Ca ions, the ligand molecules and one water oxygen atom coordinated by each metal ion [Ca-O5 2.410(2) Å] are coplanar. The coordination of the Ca ion is completed by four other water oxygen atoms situated above and below the plane of the chain [Ca-O6 2.475(1) Å, Ca-O7 2.371(2) Å]. The coordination number of the calcium(II) ion is seven. The water molecules act as donors in a system of hydrogen bonds.     

Crystal Structure and Luminescence of a Europium Coordination Polymer {[Eu(p-MOBA)_3·2H_2O]·0.5H_2O· 0.5(4,4′-bipy)}_∞

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A square‐pyramidal copper(II) complex with strong intramolecular hydrogen bonds: diaqua(N,N′‐dimethylformamide‐κO)bis[2‐(diphenylphosphoryl)benzoato‐κO]copper(II)

In the title Cu^II complex, [Cu(C₁₉H₁₄O₃P)₂(C₃H₇NO)(H₂O)₂], the molecule is bisected by a twofold axis relating the two 2‐(diphenylphosphoryl)benzoate (ODPPB) ligands. The asymmetric unit consists of a Cu^II metal centre on the symmetry axis, an ODPPB ligand, one water ligand and one dimethylformamide (DMF) ligand (disordered around the twofold axis). The Cu^II ion has fivefold coordination provided by two carboxylate O atoms from two ODPPB ligands, two O atoms from two coordinated water molecules and another O atom from a (disordered) DMF molecule, giving a CuO₅ square‐pyramidal coordination geometry. The ODPPB ligand adopts a terminal monocoordinated mode with two free O atoms forming two strong intramolecular hydrogen bonds with the coordinated water molecules, which may play a key role in the stability of the molecular structure, as shown by the higher release temperature for the coordinated water molecules than for the coordinated DMF molecule. The optical absorption properties of powder samples of the title compound have also been studied.     

Crystal structure of a new binuclear complex bis(2,4,6,8-tetramethyl-2,4,6,8-tetraazabicyclo(3.3.0)octane-3,7-dione-o,o′)-tetraaqua-hexakis(nitrato-o,o′)-dieuropium(III)

A centrosymmetric binuclear complex of europium(III) nitrate with bicyclic bisurea (2,4,6,8-tetramethyl-2,4,6,8-tetraazabicyclo(3.3.0)octane-3,7-dione, or mebicar, Mk) [Eu(C₈H₁₄N₄O₂)(H₂O)₂(NO₃)₃]₂ (I) is synthesized and its atomic structure (CIF file CCDC No. 1451437) is determined. The crystals of I are triclinic: space group \(P\overline 1 \), a = 9.8343(4) Å, b = 10.2544(4) Å, c = 10.9411(4) Å, α = 74.366(3)°, β = 67.734(4)°, γ = 67.673(4)°, V = 934.32(7) ų, ρ(calc.) = 2.03398 g/cm³, Z = 1. The europium atom is coordinated by two oxygen atoms of two Mk molecules connected by a symmetry operation, three bidentate nitrate anions, and two water molecules. The coordination polyhedron of the europium atom is a 10-vertex polyhedron, the Eu…Eu distance is 9.7433(6) Å.     

EuIrIn4 with LaCoAl4 Type Structure – Synthesis,Magnetic Properties,and 151Eu Mössbauer Spectroscopy

LaCoAl₄ type EuIrIn₄ was synthesized by induction-melting of the elements in a sealed tantalum ampoule, followed by annealing of the sample in a high-frequency or in a muffle furnace. The EuIrIn₄ structure was refined from single-crystal X-ray diffraction data: Pmma, a = 860.65(3), b = 430.33(6), c = 757.65(7) pm, wR = 0.0748, 633 F² values and 24 variables. The striking building units are iridium-centered trigonal prisms of indium atoms, distorted bcc indium cubes and a pentagonal prismatic indium coordination of the europium atoms. Within the three-dimensional [IrIn₄]^2– polyanionic network the Ir–In and In–In distances range from 260–288 pm and 306–332 pm, respectively. The divalent ground state of europium was manifested through magnetic [7.96(1) μ_B / Eu atom, T_N = 7.9(1) K] and ¹⁵¹Eu Mössbauer spectroscopic data [δ = –10.54(2) mm · s^–1; B_hf = 19.1(1) T at 6 K].     

Crystal structure of barium bis(nitrilotriacetato)cobaltate(III), Ba<Subscript>3</Subscript>[Co(Nta)<Subscript>2</Subscript>]<Subscript>2</Subscript> · 10H<Subscript>2</Subscript>O

Crystals of Ba₃[Co(Nta)₂]₂ · 10H₂O (Nta^3? is the ion of nitrilotriacetic acid) are obtained (monoclinic crystal system, a = 17.094(3), b = 13.1873(13), c = 21.490(3) Å, β = 98.457(18)°, Z = 4, space group I2/c). The crystal structure of the compound is determined by X-ray diffraction analysis. The crystals consist of the Ba²⁺ cations, water molecules, and [Co(Nta)₂]^3? anions in which the donor N and 2O atoms of each Nta^3? ion are located at opposite faces of the coordination octahedron. The Co(1, 2) atoms are arranged in the inversion centers. The Ba atoms of the complexes form an intricate three-dimensional framework. One of the two crystallographically nonequivalent complexes binds eight Ba atoms, and another one binds six Ba atoms. The coordination number of the Ba(1) atoms (in the general position) is nine (three O atoms of water molecules and six O atoms of the carboxyl groups of five complexes), and that of the Ba(2) atoms (on the 2 axis) is 6 (two O atoms of water molecules and four O atoms of the carboxyl groups of four complexes).     

Ordering and Clathrate Hydrate Formation in Co‐deposits of Xenon and Water at Low Temperatures

Local ordering in co‐deposits of water and xenon atoms produced at low temperatures can be followed uniquely by ¹²⁹Xe NMR spectroscopy. In water‐rich samples deposited at 10 K and observed at 77 K, xenon NMR results show that there is a wide distribution of arrangements of water molecules around xenon atoms. This starts to order into the definite coordination for the structure I, large and small cages, when samples are annealed at ～140 K, although the process is not complete until a temperature of 180 K is reached, as shown by powder Xray diffraction. There is evidence that Xe ? 20 H₂O clusters are prominent in the early stages of crystallization. In xenon‐rich deposits at 77 K there is evidence of xenon atoms trapped in Xe ? 20 H₂O clusters, which are similar to the small hydration shells or cages observed in hydrate structures, but not in the larger water clusters consisting of 24 or 28 water molecules. These observations are in agreement with results obtained on the formation of Xe hydrate on the surface of ice surfaces by using hyperpolarized Xe NMR spectroscopy. The results indicate that for the various different modes of hydrate formation, both from Xe reacting with amorphous water and with crystalline ice surfaces, versions of the small cage are important structures in the early stages of crystallization.     

Spectral properties of Eu(III) compound with antibacterial agent ciprofloxacin (cfqH). Crystal structure of [Eu(cfqH)(cfq)(H2O)4]Cl2 · 4.55H2O

A novel europium complex of fluoroquinolone ciprofloxacin (cfqH) with formula [Eu(cfqH)(cfq)(H₂O)₄]Cl₂ · 4.55H₂O (1) was synthesized and its crystal structure determined by X-ray crystallography. The coordination number of europium is eight and in this structure two bidentate, O,O-bonded quinolone molecules and four aqua ligands are coordinated to the metal. One molecule of quinolone is anionic whereas the other is zwitterionic. Additionally, two chloride ions are also present in the structure to compensate the charge of the europium(III) whilst disordered solvent water molecules too are present. The spectral properties (IR, Raman, luminescence) of compound 1 were studied. Analysis of the Stark structure of the luminescence spectra was carried out and the scheme of the electronically excited states and photophysical processes of compound 1 was arranged. The spectral properties show that europium–ciprofloxacin complexes could be suitable for various applications based on their solution-state stability as measured by ¹H and ¹⁹F NMR.     

Supramolecular structure of the polymeric Eu(III) complex with pyridine-2,6-dicarboxylic acid

The europium complex with pyridine-2,6-dicarboxylic acid forms three-dimensional polymers in the solid state. The crystal structure of this assembly shows that europium cation is nine-coordinated and the first coordination sphere contains four water molecules. Mono(dipicolinate) structural units are interconnected by bridging carboxylate oxygens to provide a compact supramolecular structure with a high density.     

Poly[[aqua(μ7‐ethylenediaminetetraacetato)dicadmium(II)] monohydrate]

The title compound, {[Cd₂(C₁₀H₁₂N₂O₈)(H₂O)]·H₂O}_n, consists of two crystallographically independent Cd^II cations, one ethylenediaminetetraacetate (edta) tetraanion, one coordinated water molecule and one solvent water molecule. The coordination of one of the Cd atoms, Cd1, is composed of five O atoms and two N atoms from two tetraanionic edta ligands in a distorted pentagonal–bipyramidal coordination geometry. The other Cd atom, Cd2, is six‐coordinated by five carboxylate O atoms from five edta ligands and one water molecule in a distorted octahedral geometry. Two neighbouring Cd1 atoms are bridged by a pair of carboxylate O atoms to form a centrosymmetric [Cd₂(edta)₂]⁴⁻ unit located on the inversion centre, which is further extended into a two‐dimensional layered structure through Cd2—O bonds. There are hydrogen bonds between the coordinated water molecules and carboxylate O atoms within the layer. The solvent water molecules occupy the space between the layers and interact with the host layers through O—H...O and C—H...O interactions.     

Tieftemperatur‐Oxidation in flüssigem Ammoniak: [Eu2(Ind)4(NH3)6], das erste Indolat eines Selten‐Erd‐Elementes

Low‐Temperature Oxidation in Liquid Ammonia: [Eu₂(Ind)₄(NH₃)₆], the First Indolate of a Rare Earth Element Intensively yellow to orange coloured, transparent crystals of [Eu₂(Ind)₄(NH₃)₆] were obtained by low‐temperature oxidation of europium metal with indole (C₈H₆NH) in liquid ammonia at —50 °C and subsequent melting of the reaction mixture in excess indole at 120 °C. [Eu₂(Ind)₄(NH₃)₆] has a dimeric structure and contains divalent Eu. The coordination sphere around the europium atoms consists of five N atoms of two cisoid indolate anions and three NH₃ molecules as well as an η⁵‐coordinating π‐system of another indolate ligand, bridging to the next Eu atom with an sp²‐orbital.     

On the reaction products of lanthanide chlorides with biurete

The synthesis and results of IR spectroscopy and X-ray diffraction analysis of new complexes of biurete NH₂CONHCONH₂ (BU) with the composition LnCl₃ · 2BU · 4H₂O, where Ln = La (I), Pr (II), Ho (III), Er (IV), and Lu (V), are presented. Crystals of complexes I–V include complex cations [Ln(H₂O)₄(BU)₂]³⁺ and uncoordinated chloride ions. The coordination mode of biurete molecules is bidentate through the oxygen atoms, and upon coordination the BU molecules are transformed from the initial trans to cis configuration. Water molecules are also coordinated through the oxygen atom (the shape of the polyhedron of the Ln atoms is a two-capped trigonal prism). The oxygen atoms of both BU molecules and the oxygen atoms of the first and second water molecules form a trigonal prism, whereas the oxygen atoms of the third and fourth water molecules form two caps of the coordination polyhedron. The coordinated BU molecules are joined with the chloride ions and water molecules of the adjacent complex cations by hydrogen bonds. The degree of conversion of trans-BU to cis-BU in the lanthanide series of complexes of this type is discussed.     

Ab Initio quantum mechanical charge field study of hydrated bicarbonate ion: Structural and dynamical properties

The ab initio quantum mechanical charge field molecular dynamics (QMCF MD) formalism was applied to simulate the bicarbonate ion, HCO₃^?, in aqueous solution. The difference in coordination numbers obtained by summation over atoms (6.6) and for the solvent‐accessible surface (5.4) indicates the sharing of some water molecules between the individual atomic hydration shells. It also proved the importance to consider the hydration of the chemically different atoms individually for the evaluation of structural and dynamical properties of the ion. The orientation of water molecules in the hydration shell was visualized by the θ–tilt surface plot. The mean residence time in the surroundings of the HCO₃^? ion classify it generally as a structure‐breaking ion, but the analysis of the individual ion‐water hydrogen bonds revealed a more complex behavior of the different coordination sites. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Syntheses,Molecular Structure and Thermodynamic Properties of 3‐Nitro‐1,2,4‐triazol‐5‐one Europium Complex [Eu(NTO)3(H2O)5]·5H2O

3‐Nitro‐1,2,4‐triazol‐5‐one (NTO) europium complex of [Eu(NTO)₃(H₂O)₅]·5H₂O was synthesized by mixing the aqueous solution of lithium 3‐nitro‐1,2,4‐triazol‐5‐onate and the dilute nitric acid solution of europium oxide. The title complex was characterized by elemental analysis and IR spectra. The single crystal structure was determined by a four‐circle x‐ray diffractometer. The title complex is monoclinic with space group P2₁/n and unit cell parameters of a = 1.8720(2) nm, b = 0.6548(3) nm, c = 1.9323(3) nm and β = 95.33(1)°. The coordination geometry around the europium ion is a distorted dodecahedron and there are five crystalline water molecules to form the stable structure of the crystal. From measurements of the enthalpy of solution in water at 298.15 K, the standard enthalpy of formation, lattice enthalpy and lattice energy have been determined as ‐(3798.6 ± 3.7), ?4488.4 and ?4452.4 kJ·mol^?;1, respectively.     

Transition metal complexes with squarate anion and the pyridyl-donor ligand 1,3-bis(4-pyridyl)propane (BPP): Synthesis,crystal structure and spectroscopic investigation

Synthesis, crystal structure and the vibrational spectra of coordination polymers with 1,3-bis(4-pyridyl)propane (BPP) and squarate ion ligands and transition metal ions (M = Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺) are described. All compounds are isostructural, and the BPP is not coordinated to metal site since it is in cationic form due to protonation of N atoms from pyridyl rings. The metal is coordinated to two squarate ions and two water molecules in an octahedral distorted geometry. The two water molecules are involved in medium hydrogen bonds with squarate ligands and the average of O?O distance is 2.679(3) Å. Squarate ions adopt the 1,3-bis(monodentate) coordination mode bridging two metal centers giving rise to a 2D arrangement with (4,4) topology. The four-member ring is slightly distorted and the M–M distances are respectively 8.024 and 8.111 Å. The cationic form of BPP molecules are located inside of four-member ring cavity, presenting two different orientations, in which one molecule is inverted comparing to another. Vibrational spectra of all compounds are very similar, in agreement to crystal data. In all infrared spectra of the compounds a medium band at 1640 cm⁻¹ is observed, assigned to the in plane deformation mode of NH bond, indicative of the formation of cationic BPP. In the Raman spectra of the investigated compounds is observed a weak band around 1800 cm⁻¹, assigned to the stretching mode of free CO bond, whereas the medium band observed around 1600 cm⁻¹ is tentatively assigned to coordinated CO stretching mode. At last, a very important achievement of this investigation refers to the coordination geometries of all the investigated compounds, which are governed only by the ligands, independently of the different electronic properties of the metal ions.     

Optical chemosensor properties of europium(III) tris(β-diketonates)

Interaction between Eu(III) tris(β-diketonates) and ammonia vapors increases the luminescence of Eu(III). A mechanism for the effect of analyte molecules on the intensification of Eu(III) luminescence is proposed. The mechanism includes the displacement of water molecules from the coordination sphere of europium(III).     

Formation and dissociation kinetics of Eu(III) complexes with H5do3ap and similar dota-like ligands

Complexation kinetics of the europium(III)-H₅do3ap complex (1,4,7,10-tetraazacyclododecane-1,4,7-triacetic-10-(methylphosphonic acid)) was studied at 25 °C and I = 0.1 M KCl and compared with the analogous H₄dota-like ligands. The mechanism of the formation reactions between the europium(III) ion and H₃do3a, H₄dota and H₄dota analogs having one methylphosphonic (H₅do3ap) or phosphinic acid pendant arms with a propionate side chain (H₅do3ap^PrA) was proposed on the basis of TRLIFS measurements. The experimental data of the dissociation kinetics of the europium(III) complexes with H₅do3ap and H₅do3ap^PrA ligands show that there is no change in reactivity of the complexes due to the side chain of the phosphinic acid bifunctional chelate. The TRLIFS study of the proton-assisted decomplexation reaction of the europium(III) complexes with H₃do3a, H₄dota, H₅do3ap and H₅do3ap^PrA demonstrates different behaviour influenced by a change in the number of water molecules during the reaction. The advantages and disadvantages of the TRLIFS methodology as a new experimental technique for simultaneous evaluation of kinetics and reaction mechanisms are discussed.     

Synthesis,Crystal Structure and Thermal Stability Properties of a Binuclear Copper(Ⅱ) Coordination Polymer {[Cu_2(4,4'-bipy)_2(o-ABA)_4(H_2O)_2][(H_2O)_2]}_n

One-dimensional chain copper(Ⅱ) coordination polymer has been synthesized and characterized in the solvent mixture of water and alcohol with o-acetamidobenzoic acid,4,4'-bipyridine and copper perchlorate.It is of tetragonal,space group P41212 with a=1.57756(10),b= 1.57756(10),c=2.1438(3)nm,V=5.3352(8) nm3,Dc=1.524 g/cm3,Z=4,F(000)=2536,R= 0.0479 and wR=0.0979.The crystal structure shows two coordination modes.The copper(1) is coordinated with two nitrogen atoms of one 4,4'-bipyridine molecule and two oxygen atoms from two o-acetamidobenzoic acid molecules,forming a distorted tetrahedral coordination geometry;the copper(2) is coordinated with two nitrogen atoms of one 4,4'-bipyridine molecule,four oxygen atoms from two o-acetamidobenzoic acid molecules and two water molecules,generating a distorted octahedral coordination geometry.The result of TG analysis shows that the title complex is stable below 180.0 ℃.     

Synthesis and X-ray structural study of bis(2-sodiumsulfonylethyl) sulfoxide hexahydrate

The structure of bis(2-sodiumsulfonylethyl) sulfoxide hexahydrate (1), which was synthesized by the reaction of divinyl sulfoxide with sodium metabisulfite in an aqueous ethanol medium, has been determined by X-ray structural analysis. Both Na⁺ cations are coordinated by six O atoms of crystallization water molecules and SO₃ groups; the coordination sphere is a distorted octahedron. The crystals are stabilized by an extensive network of hydrogen bonds through the water molecules of crystallization.