Mixed occupancy: the crystal structure of scheelite-type LiLu[MoO4]2.

Coarse colorless single crystals of lithium lutetium bis-[orthomolybdate(VI)], LiLu[MoO4]2, were obtained as a by-product from a reaction aimed at lithium derivatives of lutetium molybdate. The title compound crystallizes in the scheelite structure type (tetra-gonal, space group I41/a) with two formula units per unit cell. The Wyckoff position 4b (site symmetry ) comprises a mixed occupancy of Li+ and Lu3+ cations in a 1:1 ratio. In comparison with a previous powder X-ray study [Cheng et al. (2015 ▸). Dalton Trans. 44, 18078-18089.] all atoms were refined with anisotropic displacement parameters.

Crystal structure of defect scheelite-type Nd2/3[WO4].

Neodymium(III) ortho-oxidotungstate(VI) was synthesized as a side-product in an unsuccessful synthesis attempt at fluoride derivatives of neodymium tungstate in fused silica ampoules, using neodymium(III) oxide, neodymium(III) fluoride and tungsten trioxide. Violet, platelet-shaped single crystals of the title compound emerged of the bulk, which crystallize in the defect scheelite type with a trigonal dodeca-hedral coordination of oxide anions around the Nd3+ cations and the hexa-valent tungsten cations situated in the centers of oxide tetra-hedra.

Blue Excitement: The Lanthanide(III) Chloride Oxidomolybdates(VI) Ln3Cl3[MoO6] (Ln = La, Pr, and Nd) and Their Spectroscopic Properties.

The lanthanide(III) chloride oxidomolybdates(VI) with the empirical formula Ln3Cl3[MoO6] (Ln = La, Pr, and Nd) were synthesized by solid-state reactions utilizing the respective lanthanide trichloride, lanthanide sesquioxide (where available), and molybdenum trioxide together with lithium chloride as a fluxing agent. The title compounds crystallize in hexagonal space group P63/ m ( a = 942-926 pm, c = 542-533 pm, Z = 2). Besides tetracapped trigonal prismatically coordinated Ln3+ cations, noncondensed trigonal prismatic [MoO6]6- entities are found in the crystal structure. In addition to X-ray diffraction, the title compounds were also characterized by single-crystal Raman and infrared spectroscopy as well as measurements to determine their magnetic susceptibility and behavior at low temperatures. The most outstanding properties of the Ln3Cl3[MoO6] representatives (Ln = La, Pr, and Nd), however, are of an optical nature, because their band gaps, determined by diffuse reflectance spectroscopy, show a significant shift toward lower energies compared to those of other rare-earth metal chloride molybdates with a different polyhedral arrangement. This culminates in La3Cl3[MoO6]:Eu3+ exhibiting luminescence, which can be excited in the visible range of the electromagnetic spectrum by a blue light-emitting diode.

Black Current: Structure, Characterization, and Optoelectronic Properties of Ce3 Cl3 [MoO6 ].

The admixture of CeO2 , Ce, CeCl3 , and MoO3 with an excess of LiCl as flux in evacuated silica ampules leads to large black single crystals as well as a black microcrystalline powder of Ce3 Cl3 [MoO6 ] after tempering at 850 °C for three days. The title compound crystallizes in the hexagonal space group P63 /m (a=934.93(4), c=538.86(2) pm) with two formula units per unit cell. The crystal structure consists of rather unusual trigonal-prismatic [MoO6 ]6- units besides Ce3+ ions in a tetra-capped trigonal-prismatic coordination, formed by four Cl- and six O2- ions. The black color is related to an optical band gap of 1.35(2) eV, which was determined by diffuse reflectance spectroscopy and confirmed by theoretical calculations. The low band gap between the 4f1 state of cerium (HOMO) and the 5d0 state of molybdenum (LUMO) gave rise to the idea of electronic excitation between these two states by IR irradiation, creating a drop in the resistivity of the material, which was detected by appropriate measurements.

Synthesis, crystal structure and spectroscopic properties of a novel yttrium(III) fluoride dimolybdate(VI): YFMo2O7.

Thermal treatment of a mixture of Y2O3, YF3 and MoO3 in a 1 : 1 : 6 molar ratio at 850 °C in evacuated silica ampoules yielded colorless, platelet-shaped single crystals of YFMo2O7. SiO2 was dissolved from the ampoule wall in small amounts, but could be removed from the crude product by treatment with hydrofluoric acid (20%). The title compound crystallizes monoclinically in the space group P2/c with two formula units per unit cell with the dimensions a = 4.2609(2), b = 6.5644(4), c = 11.3523(7) Å, and ß = 90.511(2)°. Its crystal structure contains crystallographically unique Y(3+) cations in a pentagonal bipyramidal environment consisting of two F(-) anions in the apical positions and five O(2-) anions in the equatorial positions. These polyhedra are connected to {[YFO](8-)} chains along [100] by sharing common F(-) vertices. The likewise crystallographically unique Mo(6+) cations exhibit a coordination number of five and reside in the centers of distorted square pyramids built up of oxide anions. These entities are fused to chains along [001] by sharing common edges and vertices according to {[MoOOO](-)}. Taking a sixth oxygen ligand further away from the Mo(6+) cations into account, the aforementioned chains assemble to corrugated {[MoOOO](-)} layers perpendicular to [010] with the {[YFO](8-)} chains situated between these sheets. Since Y(3+) represents a non-luminescent rare-earth metal(iii) cation, YFMo2O7 is a suitable host material for doping with luminescence-active lanthanoid(iii) cations, such as Eu(3+).

Tetra-yttrium difluoride disilicate orthosilicate, Y4F2[Si2O7][SiO4].

In the crystal structure of Y4F2[Si2O7][SiO4], three fundamental building blocks are present, viz. anionic disilicate and orthosilicate units ([Si2O7](6-) and [SiO4](4-)) and cationic [F2Y4](10+) entities. The latter are built up by two [FY3](8+) triangles sharing a common edge. The four crystallographically independent Y(3+) cations display coordination numbers of eight for one and of seven for the other three cations, provided by oxide and fluoride anions. The overall arrangement of the building blocks can be considered as layer-like parallel to the ac plane.

The defect scheelite-type lanthanum(III) ortho-oxidomolybdate(VI) La(0.667)[MoO(4)].

In scheelite-type La(0.667)[MoO(4)], one crystallographically unique position with site symmetry -4.. and an occupancy of 2/3 is found for the La(3+) cation. The cation is surrounded by eight O atoms in the shape of a trigonal dodeca-hedron. The structure also contains one [MoO(4)](2-) anion (site symmetry -4..), which is surrounded by eight vertex-attached La(3+) cations. The polyhedra around the La(3+) cations are inter-connected via common edges, building up a three-dimensional network, in the tetra-hedral voids of which the Mo(6+) cations reside.

Filling gaps in the series of noninnocent hetero-1,3-diene chelate ligands: ruthenium complexes of redox-active α-azocarbonyl and α-azothiocarbonyl ligands RNNC(R')E, E = O or S.

The series of 4-center unsaturated chelate ligands A═B-C═D with redox activity to yield (-)A-B═C-D(-) in two steps has been complemented by two new combinations RNNC(R')E, E = O or S, R = R' = Ph. The ligands N-benzoyl-N'-phenyldiazene = L(O), and N-thiobenzoyl-N'-phenyldiazene = L(S), (obtained in situ) form structurally characterized compounds [(acac)(2)Ru(L)], 1 with L = L(O), and 3 with L = L(S), and [(bpy)(2)Ru(L)](PF(6)), 2(PF(6)) with L = L(O), and 4(PF(6)) with L = L(S) (acac(-) = 2,4-pentanedionato; bpy = 2,2'-bipyridine). According to spectroscopy and the N-N distances around 1.35 Å and N-C bond lengths of about 1.33 Å, all complexes involve the monoanionic (radical) ligand form. For 1 and 3, the antiferromagnetic spin-spin coupling with electron transfer-generated Ru(III) leads to diamagnetic ground states of the neutral complexes, whereas the cations 2(+) and 4(+) are EPR-active radical ligand complexes of Ru(II). The complexes are reduced and oxidized in reversible one-electron steps. Electron paramagnetic resonance (EPR) and UV-vis-NIR spectroelectrochemistry in conjunction with time-dependent density functional theory (TD-DFT) calculations allowed us to assign the electronic transitions in the redox series, revealing mostly ligand-centered electron transfer: [(acac)(2)Ru(III)(L(0))](+) ⇌ [(acac)(2)Ru(III)(L(•-))] ⇌ [(acac)(2)Ru(III)(L(2-))](-)/[(acac)(2)Ru(II)(L(•-))](-), and [(bpy)(2)Ru(III)(L(•-))](2+)/[(bpy)(2)Ru(II)(L(0))](2+) ⇌ [(bpy)(2)Ru(II)(L(•-))](+) ⇌ [(bpy)(2)Ru(II)(L(2-))](0). The differences between the O and S containing compounds are rather small in comparison to the effects of the ancillary ligands, acac(-) versus bpy.

Scheelite-type sodium neodymium(III) ortho-oxidomolybdate(VI), NaNd[MoO(4)](2).

Scheelite-type NaNd[MoO(4)](2) contains one crystallographic position (site symmetry [Formula: see text]) for the large cations, which is mixed-occupied by Na(+) and Nd(3+) cations in a 1:1 molar ratio. Thus, both are surrounded by eight O atoms in the shape of a trigonal dodeca-hedron. Furthermore, the structure consists of crystallographically unique [MoO(4)](2-) units (site symmetry [Formula: see text]) surrounded by eight sodium and neodymium cations, which are all vertex-attached. The polyhedra around the Na(+)/Nd(3+) cations are connected to four others via common edges, building up a three-dimensional network in whose tetra-hedral voids of O atoms the Mo(6+) cations reside.

2,3-Bis(1-methylimidazol-2-yl)quinoxaline (bmiq), a new ligand with decoupled electron transfer and metal coordination sites: the very different redox behaviour of isoelectronic complexes with [PtCl2] and [AuCl2]+.

The new, potentially ambidentate heterocyclic ligand 2,3-bis(1-methylimidazol-2-yl)quinoxaline (bmiq) was obtained from 2,3-bis(1-methylimidazol-2-yl)glyoxal and 1,2-diaminobenzene. Its coordination to PtCl(2) and to the isoelectronic [AuCl(2)](+) in [AuCl(2)(bmiq)](AuCl(4)) occurs via the imine N donors of the imidazolyl groups, leading to the formation of seven-membered chelate rings with boat conformation. According to the spectroelectrochemistry (UV-vis-NIR, EPR), the reversible electron addition to the [PtCl(2)(bmiq)] and the free ligand takes place in the (non-coordinated) quinoxaline part of the molecule, similarly as for related complexes of dipyrido[3,2-a:2',3'-c]phenazines (dppz), 2,3-bis(2-pyridyl)quinoxalines (bpq) and 2,3-bis(dialkylphosphino)quinoxalines (QuinoxP). DFT calculations confirm the experimental results (structures, spectroscopy) and also point to the coordination potential of the quinoxaline N atoms. The electron addition to [AuCl(2)(bmiq)](+) takes place not at the ligand but at the metal site, according to experimental and DFT results.

A five-center redox system: molecular coupling of two noninnocent imino-o-benzoquinonato-ruthenium functions through a pi acceptor bridge.

Combining the concepts of noninnocent behavior of metal/ligand entities and the coupling of redox-active moieties via an electronically mediating bridge led to the synthesis and the structural, electrochemical, and spectroscopic characterization of [Cl(Q)Ru(mu-tppz)Ru(Q)Cl](n) where Q(o) is 4,6-di-tert-butyl-N-phenyl-o-iminobenzoquinone and tppz(o) is 2,3,5,6-tetrakis(2-pyridyl)pyrazine, the available oxidation states being Ru(II,III,IV), Q(o,*-,2-), and tppz(o,*-,2-). One-electron transfer steps between the n = (2-) and (4+) states were studied by cyclic voltammetry and by EPR, UV-vis-NIR spectroelectrochemistry for the structurally characterized anti isomer of [Cl(Q)Ru(mu-tppz)Ru(Q)Cl](PF(6))(2), 2(PF(6))(2), the only configuration obtained. The combined investigations reveal that 2(2+) is best described as [Cl(Q(*-))Ru(III)(mu-tppz(o))Ru(III)(Q(*-))Cl](2+) with antiferromagnetic coupling between the ruthenium(III) and the iminosemiquinone components at each end. A metal-based spin as evident from large g factor anisotropy (EPR) and an intense intervalence absorption band at 1850 nm in the near-infrared (NIR) suggest that oxidation occurs at both iminosemiquinones to yield two Ru(II,III)-bonded quinones, implying redox-induced electron transfer. Reduction takes place stepwise at the metal centers yielding iminosemiquinone complexes of Ru(III,II) as evident from radical complex EPR spectra with small (99,101)Ru hyperfine contributions. After complete metal reduction to ruthenium(II) the bridging ligand tppz is being reduced stepwise as apparent from typical NIR absorption bands around 1000 nm and from small g anisotropy of the monoanion [Cl(Q(*-))Ru(II)(mu-tppz(*-))Ru(II)(Q(*-))Cl](-). A structure-based DFT calculation confirms the Ru-Cl character of the HOMO and the iminoquinone-dominated LUMO and illustrates the orbital interaction pattern of the five electron transfer active components in this new system.

Combining two non-innocent ligands in isomeric complexes [Pt(pap)(m)Q(n)](0) (pap = phenylazopyridine, Q = 3,5-di-tert-butyl-benzoquinone.

Isomeric complexes of platinum, which contain two non-innocent ligands are reported. The built-in coordination asymmetry in the ligands makes it possible to separate two different positional isomers. Results from X-ray crystallography is used to invoke the popular structure oxidation state correlation in these complexes. The redox processes are discussed and interpreted with the help of UV-vis-NIR and EPR spectroelectrochemistry.

Benzo-1,3,2-diazaphospholide and benzo-1,3,2-diazaphospholium: an isoelectronic aromatic anion-cation pair.

Isoelectronic benzo-1,3,2-diazaphospholium cations and benzo-1,3,2-diazaphospholide anions were prepared from the same phosphazane precursor; both species display according to computational studies similar aromaticity as the neutral benzo-1,3,2-diazaphosphole but are chemically more stable due to their ionic nature.

Carboxyl-functionalized task-specific ionic liquids for solubilizing metal oxides.

Imidazolium, pyridinium, pyrrolidinium, piperidinium, morpholinium, and quaternary ammonium bis(trifluoromethylsulfonyl)imide salts were functionalized with a carboxyl group. These ionic liquids are useful for the selective dissolution of metal oxides and hydroxides. Although these hydrophobic ionic liquids are immiscible with water at room temperature, several of them form a single phase with water at elevated temperatures. Phase separation occurs upon cooling. This thermomorphic behavior has been investigated by (1)H NMR, and it was found that it can be attributed to the temperature-dependent hydration and hydrogen-bond formation of the ionic liquid components. The crystal structures of four ionic liquids and five metal complexes have been determined.

YF[MoO4] and YCl[MoO4]: two halide derivatives of yttrium ortho-oxomolybdate: syntheses, structures, and luminescence properties.

The halide derivatives of yttrium ortho-oxomolybdate YX[MoO 4] (X = F, Cl) both crystallize in the monoclinic system with four formula units per unit cell. YF[MoO 4] exhibits a primitive cell setting (space group P21/ c; a = 519.62(2) pm, b = 1225.14(7) pm, c = 663.30(3) pm, beta = 112.851(4) degrees ), whereas the lattice of YCl[MoO 4] shows face-centering (space group C2/m; a = 1019.02(5) pm, b = 720.67(4) pm, c = 681.50(3) pm, beta = 107.130(4) degrees ). The two compounds each contain crystallographically unique Y (3+) cations, which are found to have a coordination environment of six oxide and two halide anions. In the case of YF[MoO 4], the coordination environment is seen as square antiprisms, and for YCl[MoO 4], trigon-dodecahedra are found. The discrete tetrahedral [MoO 4] (2-) units of the fluoride derivative are exclusively bound by six terminal Y (3+) cations, while those of the chloride compound show a 5-fold coordination around the tetrahedra with one edge-bridging and four terminal Y (3+) cations. The halide anions in each compound exhibit a coordination number of two, building up isolated planar rhombus-shaped units according to [Y 2F 2] (4+) in YF[MoO 4] and [Y 2Cl 2] (4+) in YCl[MoO 4], respectively. Both compounds were synthesized at high temperatures using Y2O3, MoO3, and the corresponding yttrium trihalide in a molar ratio of 1:3:1. Single crystals of both are insensitive to moist air and are found to be coarse shaped and colorless with optical band gaps situated in the near UV around 3.78 eV for the fluoride and 3.82 eV for the chloride derivative. Furthermore, YF[MoO 4] seems to be a suitable material for doping to obtain luminescent materials because the Eu (3+)-doped compound shows an intense red luminescence, which has been spectroscopically investigated.

Metal-induced tautomerization of p- to o-quinone compounds: experimental evidence from CuI and ReI complexes of azophenine and DFT studies.

Azophenine (7,8-diphenyl-2,5-bis(phenylamino)-p-quinonediimine, L(p)) reacts with [Cu(PPh3)4](BF4) or [Re(CO)(5)Cl] to yield the (Ph3P)(2)Cu(+) or [(OC)(3)ClRe] complex of the tautomeric form 7,8-diphenyl-4,5-bis(phenylamino)-o-quinonediimine, L(o), as evident from structure determinations and from very intense metal-to-ligand charge transfer (MLCT) transitions in the visible region. Time-dependent DFT (TD-DFT) calculations on model complexes [(N intersection N)Re(CO)(3)Cl] confirm the spectroscopic results, showing considerably higher oscillator strengths of the MLCT transition for the o-quinonediimine complexes in comparison to compounds with N intersection N=1,4-dialkyl-1,4-diazabutadiene. The complexes are additionally stabilized through hydrogen bonding between two now ortho-positioned NHPh substituents and one fluoride of the BF(4) (-) anion (Cu complex) or the chloride ligand (Re complex). DFT Calculations on the model ligands p-quinonediimine or 2,5-diamino-p-quinonediimine and their ortho-quinonoid forms with and without Li(+) or Cu(+) are presented to discuss the relevance for metal-dependent quinoproteins.

A Fully Characterized Complex Ion with Unreduced TCNQ as Fourfold Bridging Ligand: [(µ4 -TCNQ){fac-Re(CO)3 (bpy)}4 ]4+ .

Innocent behavior of a typical non-innocent ligand has been observed for the first structurally characterized discrete metal complex with tetranucleating TCNQ. The coordination of four [Re(CO)3 (bpy)]+ units (see picture: C: black, N: green, O: blue, Re: red) facilitates the reduction of the already excellent π-acceptor molecule TCNQ by a further 0.74 V! TCNQ=7,7,8,8-tetracyano-p-quinodimethane, bpy=2,2'-bipyridine.