Seven-coordinate Environment Research Articles

A novel red phosphor of seven-coordinated Mn4+ ion-doped tridecafluorodizirconate Na5Zr2F13 for warm WLEDs.

Herein, a novel red phosphor based on seven-coordinated Mn4+ ion-doped tridecafluorodizirconate, Na5Zr2F13 (NZF), has been synthesized by stirring a mixture of K2MnF6, NaF, and H2ZrF6 at room temperature. The crystal structure and morphology of the as-obtained phosphor NZF:Mn have been determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The composition and distribution of Mn4+ ions in NZF have been confirmed by energy-dispersive spectroscopy (EDS) and element mapping via transmission electron microscopy (TEM). The phosphor NZF:Mn exhibits a strong zero phonon line (ZPL) at 616 nm under excitation of blue light from a GaN light-emitting diode (LED) chip; this is attributed to the low symmetry of Mn4+ ions occupied in a seven-coordinated environment. The luminescence intensity of NZF:Mn has been optimized by controlling the synthesis procedure and synthetic parameters. The luminescence mechanism of the red phosphor NZF:Mn has been investigated according to the detailed experimental results. A warm white light has been produced by a WLED fabricated with the red phosphor NZF:Mn and the commercial yellow phosphor Y3Al5O12:Ce3+ (YAG:Ce) on a GaN LED chip.

Steric congestion at, and proximity to, a ferrous center leads to hydration of α-nitrile substituents forming coordinated carboxamides.

The question of the conversion of nitrile groups into amides (nitrile hydration) by action of water in mild and eco-compatible conditions and in the presence of iron is addressed in this article. We come back to the only known example of hydration of a nitrile function into carboxamide by a ferrous [Fe(II)] center in particularly mild conditions and very efficiently and demonstrate that these unusual conditions result from the occurrence of steric stress at the reaction site and formation of a more stable end product. Two bis(cyano-substituted) (tris 2-pyridyl methyl amine) ligands have been prepared, and the structures of the corresponding FeCl2 complexes are reported, both in the solid state and in solution. These two ligands only differ by the position of the nitrile group on the tripod in the α and β position, respectively, with respect to the pyridine nitrogen. In any case, intramolecular coordination is impossible. Upon action of water, the nitrile groups are hydrated however only if they are located in the α position. The fact that the β-substituted β-(NC)2TPAFeCl2 complex is not water sensitive suggests that the reaction proceeds in an intramolecular way at the vicinity of the metal center. In the bis α-substituted α-(NC)2TPAFeCl2 complex, both functions are converted in a very clean fashion, pointing out that this complex exhibits ligand flexibility and is not deactivated after the first hydration. At a preparative scale, this reaction allows the one-pot conversion of the bis(cyano-substituted) tripod into a bis(amido-substituted) one in particularly mild conditions with a very good yield. Additionally, the XRD structure of a ferric compound in which the two carboxamido ligands are bound to the metal in a seven-coordinate environment is reported.

Diorganotin (IV) Heptacoordinated Complexes Containing Pentadentate [N3O2] Ligands Derived From 5-Substituted-Salicylaldehydes and Diethylenetriamine: Synthesis, Characterization, and Molecular Structure

A series of heptacoordinated tin(IV) mononuclear complexes [(R′)2Sn(5-X-saldien)] (X = H, OCH3, NO2) were synthesized by reaction of dimethyl-, di-n-butyl-, di-n-octyl-, and diphenyltin (IV) oxides with the pentadentate Schiff base ligands saldienH2, 5-MeO-saldienH2, and 5-NO2-saldienH2. All of the complexes were characterized by IR, mass spectrometry, and 1H, 13C, and 119Sn NMR spectroscopies, and the spectra display chemical shifts corresponding to a seven-coordinated tin environment. The crystal structures of complexes 2a, 2d, and 4b were determined by X-ray diffraction. The complexes are isostructural and the tin atoms exhibit pentagonal-bipyramidal geometries with the methyl, n-butyl, and phenyl groups occupying the axial positions and the donor atoms from the ligand occupying the equatorial positions. A fluxional behavior was also observed that involves a dissociation-association mechanism of the N-Sn bonds.

NaCu(Ta1−yNby)4O11 solid solution: A tunable band gap spanning the visible-light wavelengths

The new solid-solution NaCu(Ta1−yNby)4O11 (0≤y≤0.7) was synthesized by solid-state methods in the form of bulk powders that ranged from light-yellow to brown colored and were characterized by powder X-ray diffraction techniques (Space group R-3c (#167); Z=6; a=6.214(1)–6.218(1)Å and c=36.86(1)–36.94(1)Å). Full-profile Rietveld refinements confirmed a site-differentiated ordering of the Cu(I) and Na cations, i.e., occupying the 12c (linear environment) and 18d (seven-coordinate environment) crystallographic sites respectively. Conversely, a statistical mixture of Ta(V) and Nb(V) cations occurred over the 6b (octahedral environment) or the 18e (pentagonal-bipyramidal environment) crystallographic sites, without any preferential segregation. The UV-Vis diffuse reflectance spectra showed a significant red-shift of the optical bandgap size (indirect) from ∼2.70eV to ∼1.80eV across the solid solution with increasing Nb(V) content. Electronic-structure calculations using the tight-binding linear-muffin-tin-orbital approach showed that the reduction in bandgap size arises from the introduction of the lower-energy Nb 4d0 orbitals into the conduction band and consequently a lower energy of the conduction band edge. The lowest-energy bandgap transitions were found to be derived from electronic transitions between the filled Cu(I) and the empty Nb(V) d-orbitals, with a small amount of mixing with the O 2p orbitals. The resulting conduction and valence band energies are found to approximately bracket the redox potentials for water reduction and oxidation, and meeting the thermodynamic requirements for photocatalytic water-splitting reactions.

Structural Phase Transition in the S = 1/2 Kagome System Cs2ZrCu3F12 and a Comparison to the Valence-Bond-Solid Phase in Rb2SnCu3F12

The crystal structure of the S = 1/2 kagome system Cs2ZrCu3F12 has been determined at both 295 and 125 K via single-crystal X-ray diffraction. A first-order structural phase transition is seen near 225 K, confirmed by variable-temperature synchrotron powder diffraction studies, in which the structure transforms from rhombohedral (R3m) to monoclinic (P21/m). A corresponding abrupt change in dielectric constant is observed near the same temperature. The phase transition is driven by a dramatic change in coordination around the Zr site, which changes from regular octahedral in the rhombohedral phase to a seven-coordinate environment in the monoclinic phase. This leads to a severe buckling of the copper fluoride kagome layers and significant changes in the geometry around the Cu sites, which correlates with both the observed dielectric anomaly and a previously observed anomaly in magnetic susceptibility. It is suggested that this structural phase transition ultimately permits long-range antiferromagnetic ord...

Poly[μ-(1,3-dihydroxypropan-2-olato)-potassium

The asymmetric unit of the title compound, [K(C3H7O3)]n or K[H2gl]n, common name potassium glycerolate, contains half the K+ cation and half of the glycerolate anion. The other half of the anion is generated through a mirror plane passing through the K atom, and a C, an H and an O atom of the glycerolate ligand. The K+ ion is coordinated by the O atoms of the OH groups, leading to a six-membered chelate ring that adopts a very distorted boat conformation. The negatively charged O atom of the glycerolate anion, [H2gl−], is found in the flagpole position and forms an ionic bond with the K+ ion. The O atoms of the hydroxo groups are coordinated to two K+ ions, whereas the negatively charged O atom is bonded to one K+ ion. The K+ ion is coordinated by three other symmetry-related monodentate H2gl− ligands, so that each H2gl− ligand is bonded to two K+ ions, and the potassium has a seven-coordinate environment. The H2gl− ligands are connected via a strong O—H⋯O hydrogen bond and, together with the K⋯O inter­connections, form polymeric sheets which propagate in the directions of the a and b axes.

Synthesis, spectroscopic and structural properties of uranyl complexes based on bipyridine N-oxide ligands

Abstract By using 2,2′-bipyridine N-oxide (bipyO) and 2,2′-bipyridine N,N′-dioxide (bipyO2), three new uranyl complexes [UO2(bipyO)SO4]·H2O (1), [UO2(bipyO)(OH)(NO3)]2·H2O (2) and [UO2(bipyO2)H2O](ClO4)2·(3) were synthesized using uranyl salts including non-coordinating or weakly coordinating power of the ClO4− anion and the strongly coordinating power of NO3− and SO42− anions. All of the compounds were characterized by CHN microanalytical procedures, infrared and luminescence spectroscopy and by single crystal X-ray diffraction. Spectroscopic studies indicate that the bipyO is bound to the uranyl group via the nitrogen and oxygen atoms. Structural analyses revealed that overall bonding pattern is different in each case: 1 is a polymer; in 2 dimeric complex molecules are formed, whereas 3 is composed of monomers. In all of the complexes, the uranium atom is in a seven-coordinate environment.

Structural Diversity in Supramolecular Complexes of MCl3 (M = As, Sb, Bi) with Constrained Thio- and Seleno-Ether Ligands

MCl(3) react with o-C(6)H(4)(EMe)(2) (E = S, Se) or o-C(6)H(4)(CH(2)ER)(2) (E = S, R = Me or Et; E = Se, R = Me) in anhydrous CH(2)Cl(2) or MeCN to give the yellow (Bi) or white (Sb) complexes, [MCl(3){o-C(6)H(4)(EMe)(2)}], [(MCl(3))(2){o-C(6)H(4)(CH(2)SMe)(2)}(3)], [MCl(3){o-C(6)H(4)(CH(2)SEt)(2)}], and [(BiCl(3))(4){o-C(6)H(4)(CH(2)SeMe)(2)}(3)], which were characterized by IR/Raman, (1)H NMR spectroscopy, and microanalysis. The corresponding reactions with AsCl(3) gave oils. Using the tetrachalcogenoethers, 1,2,4,5-C(6)H(2)(CH(2)EMe)(4) (E = S or Se), gave [(MCl(3))(2){1,2,4,5-C(6)H(2)(CH(2)EMe)(4)}] (E = S: M = As, Sb or Bi; E = Se: M = As) as powdered solids. The structures adopted are extremely diverse within this related series. Crystal structure determinations show infinite chains for [MCl(3){o-C(6)H(4)(EMe)(2)}] (M = Bi, E = S or Se; M = Sb, E = S), although the structures differ significantly in detail. [BiCl(3){o-C(6)H(4)(SMe)(2)}] is formed through chains of orthogonal μ-Bi(2)Cl(2) units linked together, with one dithioether ligand chelating per Bi atom, and seven-coordinate Bi; [SbCl(3){o-C(6)H(4)(SMe)(2)}] comprises weakly associated Sb(2)Cl(6) dimer units linked into chains by weakly bridging dithioethers, where both available lone pairs on each S atom are used. [BiCl(3){o-C(6)H(4)(SeMe)(2)}] comprises distorted square pyramidal units involving pyramidal BiCl(3) primary coordination and a weakly chelating diselenoether ligand, and assembled into infinite chains through long bridging Bi···Cl interactions via all three Cl's. The 2:3 M:L complexes [(MCl(3))(2){o-C(6)H(4)(CH(2)SMe)(2)}(3)] (M = Bi or Sb) are isostructural, and also show one-dimensional polymers, but this time the coordination is based upon pyramidal MCl(3) units, with secondary bonding via three long M···S contacts from bridging dithioethers, and a further long M···Cl bridge which completes a distorted seven-coordinate environment at M. The Et-substituted thioether analogue gives the 1:1 [MCl(3){o-C(6)H(4)(CH(2)SEt)(2)}] for both Bi and Sb; the former showing a chain polymer structure based upon seven-coordinate Bi and bridging dithioethers and the latter a weakly Cl-bridged dimer with distorted octahedral coordination at Sb, with a chelating dithioether. The 4:3 [(BiCl(3))(4){o-C(6)H(4)(CH(2)SeMe)(2)}(3)] complexes are based upon a central BiCl(6) octahedron linked to each of the other three Bi atoms via two bridging Cl atoms; the outer Bi atoms are also bonded to two mutually trans Se donor atoms from distinct diselenoethers, and two terminal Cl atoms, giving a distorted octahedral coordination environment at Bi. One of the two crystallographically independent tetrabismuth units is discrete, while the other shows further Cl-bridges to adjacent units giving an infinite network. [(AsCl(3))(2){1,2,4,5-C(6)H(2)(CH(2)SMe)(4)}] also forms an infinite network based upon square pyramidal As(III), and comprises pyramidal AsCl(3) units each weakly coordinated to two (mutually cis) S-donor atoms from two different thioether ligands. The Sb-analogue is structurally very similar; however, in this case a solvent MeCN occupies the sixth coordination site. Finally, [(AsCl(3))(2){1,2,4,5-C(6)H(2)(CH(2)SeMe)(4)}] forms an infinite chain based upon distorted octahedral coordination at As through three terminal (pyramidal) Cl atoms, two Se atoms from κ(2)-μ(2)-selenoethers, although unexpectedly the chelation is through Se atoms that are mutually meta on the aromatic ring; with one Se atom on each ligand using both of its lone pairs to bridge (weakly) between two As atoms. These MCl(3)-chalcogenoether adducts are mostly weakly associated, and lead to very diverse structures which result from a combination of intra- and intermolecular interactions and crystal packing.

Two novel metal organic frameworks of Sn(II) and Pb(II) with Pyridine-2,6-dicarboxylic Acid and 4,4′-Bipyridine: syntheses, crystal structures and solution studies

Two novel compounds with formulae [Sn2(pydcH)2(H2O)2O]n, 1, and (4,4′-bpyH2)0.5[Pb(pydc)2(4,4′-bpyH)].4,4′-bpy.4H2O, 2, were obtained from a one-pot reaction between pyridine-2,6-dicarboxylic acid (pydcH2) and 4,4′-bipyridine (4,4′-bpy) with corresponding Sn(II) and Pb(II) salts. In compound 1 with a polymeric structure, each Sn(II) atom is six-coordinated by one water molecule, two (pydcH)− groups and one oxide group resulted in a coordination polymer. Compound 2 has a seven-coordinated environment around Pb(II) atom by two (pydc)2− groups and one (4,4′-bpyH). The anionic complex is balanced by half a (4,4′- bpyH2)2+ as counter ion. There are four uncoordinated water molecules and one 4,4′-bpy in the crystal lattice. Therefore, in compound 2, we have neutral, mono- and biprotonated forms of 4,4′-bipyridine, simultaneously. Several interactions including O-H⋅⋅⋅ O, O-H⋅⋅⋅EN and C-H⋅⋅⋅O hydrogen bonds, ion pairing, C-O⋅⋅⋅π (O⋅⋅⋅Cg 3.324(3) A and 3.381(3) A in 1 and O⋅⋅⋅Cg 3.346(4) A in 2), C-H⋅⋅⋅π (C⋅⋅⋅Cg 3.618(4) A in 2), and π⋅⋅⋅π stackings (with Cg ⋅⋅⋅ Cg distances of 3.613(2) and 3.641 (2) A in 2) are present to expand and stabilize the structure. The complexation reactions of bpy and pydc-bpy with Sn2+ and Pb2+ ions in aqueous solution were investigated by potentiometric pH titrations, and the resulting equilibrium constants and species distributions at various pHs for major formed complexes are described.

Structural study of semi-coordination in a seven-coordinate copper(II) complex: distortion isomerism of [Cu(CH3COO)2(4-aminopyridine)2(H2O)

[Di(acetato)bis(4-aminopyridine)aquacopper(II)] exists in two different monoclinic forms. The crystal structure of Form 1, which crystallizes in space group P21/c, was determined by X-ray crystallography. Experimental data was then compared with that found for Form 2, which crystallizes in space group C2/c. The seven-coordinate environment of copper in both forms is consistent with the bond-valence model. The asymmetric copper(II) coordination of Form 1 is consistent with the density-functional theory. The isomers differ in distortion of the pentagonal bipyramid as the coordination polyhedron around Cu. Carboxylate groups for both isomers are bonded to copper as bidentate ligands. The Cu in Form 1 is semi-coordinated by two long carboxylate O bonds to create the seven-coordinate environment (Cu···O distances are 2.785(4) and 2.9996(5) Å). Infrared and electron spin resonance spectra of both isomers are consistent with their crystal structures.

Assemblies of Two New Metal−Organic Frameworks Constructed from Cd(II) with 2,2‘-Bipyrimidine and Cyclic Oxocarbon Dianions CnOn2- (n = 4, 5)

Two extended networks of Cd(II) with 2,2‘-bipyrimidine (bpym) and cyclic oxocarbon dianions CnOn2- (n = 4, 5) with formulas [Cd(C4O4)(bpym)0.5(H2O)] (1) and [Cd(C5O5)(bpym)0.5(H2O)] (2) have been synthesized and characterized by single-crystal X-ray diffraction studies. Structural determination reveals that, in compounds 1, each Cd center lies in a seven-coordinate environment bonded to two bpym nitrogen atoms and five oxygen donors from four squarate and one water molecules. The squarate acts as a bridging ligand with two different binding modes, a tetramonodentate (μ4) and a bis-bridging (μ4) coordination mode, linking the Cd(II) ions to form a two-dimensional (2D) metal−squarate layer. Adjacent layers are then mutually linked via bridges of bis-bidentate bpym ligands constructing a three-dimensional (3D) triangular metal−organic framework (MOF). In compound 2, each Cd center lies in an eight-coordinate environment bonded to two bpym nitrogen atoms and six oxygen donors from three croconate ligands and ...

Hydrogen bonding and π-stacking interactions in the zipper-like supramolecular structure of the monomeric cadmium(II) complex [Cd(pyterpy)(H 2O)(NO 3) 2] (pyterpy = 4 ′-(4-pyridyl)-2,2 ′:6 ′,2 ′′-terpyridine)

The reaction of pyterpy with an excess of cadmium(II) nitrate yields the novel mononuclear complex [Cd(pyterpy)(H 2O)(NO 3) 2]. The crystal structure shows to the Cd(II) centre in a seven-coordinate environment and the molecular units behaving as supramolecular nodes. These neutral nodes are connected through aromatic π-stacking interactions concerted with O–H⋯N(4-pyridyl) and O–H⋯O(nitrate) hydrogen bonds to give couples of parallel linear strips assembled in a zipper-like motif. The infinite strips are oriented in the same direction and each one interact weakly with their neighbors by means of C–H⋯O hydrogen bonds to form the crystal. The supramolecular product is highly insoluble in the most common organic solvents and water, but soluble in dimethyl sulfoxide where the intermolecular interactions are broken.

Synthesis and characterization of dinuclear lanthanide(III) and yttrium(III) cryptates of a hexavalent anionic polydentate ligand

Reaction of tris(2-aminomethyl)amine with bis(hydroxybenzaldehyde) ( 1) in presence of M(CF 3SO 3) 3 (M=Y, Gd, Tb, Dy, Ho, Er, Tm) in methanol yielded the dinuclear lanthanide(III) and yttrium(III) cryptates [M 2L] ( 2). The structure of [Y 2L] was established by X-ray crystallography. Each yttrium ion is in a seven-coordinate environment composed of three imine nitrogen atoms, one apical nitrogen atom, and three oxygen atoms. The dinuclear complexes were found to be a host for Rb + and Cs +.

Crystal structures of [WI2(CO)3{Ph2P(CH2)nPPh2}] (n = 2 or 3)

[WI2(CO)3{Ph2P(CH2)2PPh2}] (1) crystallizes out in the monoclinic space group P21/n, with a = 13.852(7) A, b = 14.789(19) A, c = 14.915(19) A, β = 102.86(1)°, Z = 4. [WI2(CO)3{Ph2P(CH2)3PPh2}] (2) crystallizes out in the monoclinic space group P21/n, with a = 10.499(15) A, b = 14.58(2) A, c = 20.75(3) A, β = 103.59(1)°, Z = 4. Both structures show the metal in a seven-coordinate environment with a carbonyl in the unique capping position, two further carbonyls and a phosphorus in the capped face, and two iodides and the second phosphorus in the uncapped face.

Synthesis, 31P NMR data and X-ray analysis of a ruthenium(II) dimethylphenylphosphine complex with dimerized phenylacetylene: The structure of [(PhMe 2P) 4Ru( η3-PhC 3CHPh)](PF 6)

Treatment of [RuHL 5] + (L  PMe 2Ph) with phenylacetylene in ethanol the dimerization of HCCPh to ( Z)-1,4-diphenylbut-3-en-1-yne. The molecular structure of [Ru( η 3-PhC 3CHPh)L 4](PF 6) (L  PMe 2Ph) ( 2) shows a seven-coordinate environment at ruthenium; the η 3-butenynyl moiety is both σ- and π-coordinated to the metal centre. Low-temperature 31P NMR data for some [Ru(CCR)L 4](PF 6) complexes with R  Ph, CO 2Et, SiMe 3, 1Bu and L  PMe 2Ph are discussed.

Heterobimetallic MoSn complexes. Reactions of [Mo(CO) 3(CH 3CN) 2(Cl)(SnRCl 2)] (R = Me, Ph) with 4(4-XC 6H 4) 3 (X = Cl, F, H, Me, MeO)

Three families of heterobimetallic compounds were obtained by reaction of [Mo(CO) 3(CH 3CN) 2(Cl)(SnRCl 2)] (R = Ph, Me) with P(4-XC 6H 4) 3 (X = Cl, F, H, Me, MeO). The type of compound obtained dependent on the solvent and concentration of the starting compound. So, [Mo(CO) 2(CH 3COCH 3) 2(PPh 3)(Cl)(SnRCl 2)]· nCH 3COCH 3 (R = Ph, n = 0.5; R = Me, n = 1) (type I) and [Mo(CO) 3{P(4-XC 6H 4) 3}(μ-Cl)(SnRCl 2)] 2 (R = Ph, X = Cl, F, H, Me, MeO; R = Me, X = Cl, F) (type II) were isolated from acetone solution in ca 0.05 M and 0.1 M concentrations, respectively. However, [Mo(CO) 3(CH 3CN) {P(4-XC 6H 4) 3}(Cl)(SnRCl 2)] (R = Ph, X = H; R = Me, X = Cl, F, H) (type III) were obtained from dichloromethane solution independently of the concentration used. All new complexes showed a seven-coordinate environment at molybdenum, containing MoCl and MoSn bonds. Mössbauer spectra indicated a four-coordination at tin for type III complexes.