Chantal Brouca-Cabarrecq

Study of new lanthanide complexes of 2,6-pyridinedicarboxylate: synthesis, crystal structure of Ln(Hdipic)(dipic) with Ln=Eu, Gd, Tb, Dy, Ho, Er, Yb, luminescence properties of Eu(Hdipic)(dipic)

Abstract This paper presents the hydrothermal synthesis of a series of new isomorphous bis-dipicolinato lanthanide complexes: Ln(Hdipic)(dipic) with Ln=Eu, Gd, Tb, Dy, Ho, Er, Yb, and dipic=2,6-pyridinedicarboxylate. A structural study has been realised for the Ho3+ complex. It crystallises in a two-dimensional network, where sheets are parallel to the (100) plane. The luminescent properties of the analogous Eu3+ complex have been investigated. The composition of the 7FJ levels is consistent with a true C1 local symmetry: six oxygen and two nitrogen atoms forming a distorted square antiprism. The 5D0 emission lifetime is only slightly shorter than in [Eu(dipic)3]3− in solution, but the ligand to metal energy transfer is much less efficient.

Lanthanide(III)-copper(II) squarates: synthesis, crystal structure, magnetism and thermal behaviour of [La2Cu(C4O4)4(H2O)16]·2H2O and [Gd2Cu(C4O4)4(H2O)12]2H2O

Abstract [La2Cu(C4O4)4(H2O)16]2H2O and [Gd2Cu(C4O4)4(H2O)12]·2H2O were obtained as single crystals from a mixture of squaric acid and metal chlorides in water. The structures, determined from X-ray diffraction data, are made of heterobimetallic layers in which hydrated Ln(III) and Cu(II) cations are related by squarate anions, according to a scheme which depends on the lanthanoid. Both compounds were submitted to thermal gravimetric and differential analyses in an oxygenated atmosphere, yielding Ln2CuO4 oxides as final decomposition products. The magnetic study of [Gd2Cu(C4O4)4(H2O)12]· 2H2O showed no significant spin coupling between Gd(III) and Cu(II).

f Element croconates. 1 : Lanthanide croconates : synthesis, crystal structure and thermal behaviour

Abstract Lanthanide croconates free of alkaline elements have been prepared by using croconic acid or triethanolammonium croconate. They are divided into two families: 1-Ln: [Ln(H2O)5]2(C5O5)3·4H2O with Ln(III)Ce, Pr, Nd, Sm, Eu, Gd; 2-Ln: [Ln(H2O)6]2(C5O5)3·3H2O with Ln(III)Tb, Dy, Ho, Er, Yb. In the general conditions used to synthesize such complexes, lanthanum, lutetium and yttrium belong neither to the family 1-Ln nor to the family 2-Ln. In the presence of oxygen and exposed to daylight the latter elements induce, after a few days, a degradation of the croconate ligand leading to oxalate complexes and to another phase still unknown. A possible hypothesis is presented. A structural study has been performed on a single-crystal representative on each family: Pr for 1-Ln, Er for 2-Ln. The first family crystallizes in the orthorhombic system, space group Pccn, while the second one crystallizes in the triclinic system, space group P1. The salient feature of both structures consists of discrete, neutral, dinuclear entities: [Ln(H2O)x]2(C5O5)3, with x=5 for 1-Ln and x=6 for 2-Ln. However, these entities differ markedly from one family to the other by the coordination mode of the croconate ligand. For 1-Ln the two independent croconates are either chelating or bis-chelating while for 2-Ln the three independent croconates are monodentate and transmonodentate. Between the two structures, a modification of the lanthanide coordination number takes place: 9 for Pr as a distorted trigonal tricapped prism, 8 for Er (Er1 and Er2) as a deformed antisquare prism. The crystal structure is assured, in both cases, by hydrogen bonding and van der Waals interactions between stacked croconate planes. Free water molecules are localized in tunnels. Dehydration of lanthanide croconates of each family takes place in a single step around 90 to 150 °C; anhydrous compounds are stable. The decomposition of the croconate ligand proceeds via oxycarbonate according to the considered lanthanide. It starts around 310 °C, and constant weight is achieved at a variable temperature up to 700 °C, leading to the corresponding oxides. An endotherm is found for the dehydration, a strong exotherm for the croconate decomposition.

f element croconates 2. Thorium(IV) and dioxo-uranium(VI) croconates — synthesis, crystal structure and thermal behaviour

Abstract Two complexes of actinide croconates, thorium(IV) and dioxo-uranium(VI) were prepared: Th(H2O)7(C5O5)2 and UO2(H2O)K2(C5O5)2. The crystal structure of these complexes was determined by X-ray single crystal technique. The thorium croconate hydrated crystallizes in the orthorhombic system, space group Pnma. It is made of discrete, neutral entities. In this complex the croconate ligand is only monodentate. The uranyl hydrated potassium croconate crystallizes in the monoclinic system, space group C2/c. This complex has a 3D structure presenting tunnels in which are localized the water molecules bound to the uranium atom. The outstanding feature of this structure is the high number (seven) of metals bound to each croconate ligand. This latter is bis-monodentate towards the uranium atom, bis-chelating towards the potassium atom and the two oxygen atoms are bound to one supplementary potassium atom. The thermal behaviour of these complexes was studied. For the thorium croconate hydrated dehydration occurs first, followed by the decomposition of the croconate ligand which yields thorium oxide, ThO2. A more complex and interesting behaviour is noticed for the complex UO2(H2O)K2(C5O5)2. The products formed at the outset of the decomposition seem to influence the further stages.

[CaSb2(EDTA)2(H2O)8]n: synthesis, crystal structure, and thermal behavior

The synthesis and crystal structure of a new EDTA complex, [CaSb2(EDTA)2(H2O)8]n, are reported. This compound crystallizes in the monoclinic space group P21/n, with a = 7.132(1) Å, b = 21.893(3) Å, c = 10.891(2) Å, β = 91.15(2)°. Sb(EDTA) entities are connected through carboxylate bridges to the calcium atoms resulting in layers parallel to the (101) plane. These layers are linked through a weak Sb···O bond (3.171 Å). Pyrolysis of this complex under sulfur vapor, between 400 and 800°C, leads to a mixture of the monometallic sulfides. Pyrolysis in air above 700°C allows the easy preparation of the mixed oxide CaSb2O6.

[NaBi(EDTA)(H2O)3]n: synthesis, crystal structure, and thermal behavior

The synthesis and crystal structure of the EDTA complex [NaBi(EDTA)(H2O)3]n are reported. It crystallizes in the monoclinic crystal system (space groupP21/c,a=6.822(1)Å,b=16.733(6)Å,c=13.763(2)Å, β=97.13(2)°). Bi(EDTA) entities are connected through carboxylate bridges resulting in layers parallel to the (010) plane. These layers are strongly linked by Na carboxylate and Na−OH2 bridging interactions, establishing short Bi−Na and Na−Na distances. Pyrolysis of this complex under sulfur vapor between 600 and 900°C leads to the mixed sulfide NaBiS2. Pyrolysis in air shows a very complicated decomposition mechanism and the probable formation of a bimetallic oxycarbonate.

Synthesis and crystal structure of a new bimetallic complex of diethylenetriamine pentaacetic acid: [YbAg2(dtpa)(H2O)]·3H2O

The reaction between Yb(III) nitrate, Ag(I) nitrate, and the diethylenetriamine pentaacetate (dtpa) ligand gives rise to a bimetallic complex. [YbAg2(dtpa)(H2O)]·3H2O is triclinic, space group P-1, with a = 8.768 (3), b = 9.862 (2), c = 13.055 (2) Å, α = 75.40 (1), β = 83.00 (2) and γ = 87.46 (2)°. Each dtpa is coordinated to one ytterbium and six silver atoms. The resulting crystal structure can be described as 2D packing. In the layers, the ytterbium atoms are connected through [Ag(COO)]2 dimers. Strong hydrogen bonds, involving the noncoordinated water molecules, ensure crystal cohesion.

LiSb(edta)(H2O): a convenient preserser to LiSbS2 and LiSbO3

The synthesis and crystal structure of the edta complex LiSb(edta)(H2O) are reported (H4edta = ethylenediaminetetraacetic acid). The compound crystallizes in the monoclinic system. Sb(edta) entities are connected by cyclic [Li(COO)]2 dimers resulting in parallel layers stacked in the [110] direction. Pyrolysis of this complex under sulfur vapour between 700 and 850 °C leads to the mixed sulfide β-LiSbS2. Pyrolysis in air above 660 °C allows the preparation of the mixed oxide LiSbO3.

MANGANESE COMPLEXES OF 1,3-BIS(3-NITROSALICYLIDENEAMINO)-PROPAN-2-OL. STRUCTURE AND MAGNETIC AND ELECTROCHEMICAL PROPERTIES

Four complexes [MnII(3NO2-Hsalpro)]1, [MnII2(3NO2-salpro)(O2CMe)]·4MeOH 2, [MnIII2(3NO2-salpro)2(H2O)]·H2O 3 and [{MnIII(3NO2-salpro)}2]·2dmf 4, [3NO2-H3salpro = 1,3-bis(3-nitrosalicylideneamino)propan-2-ol, dmf = dimethylformamide] have been synthesized and studied. The structure of 4 was solved by direct methods and refined to conventional agreement indices R=R′= 0.041. The molecular structure consists of discrete [{MnIII(3NO2-salpro)}2] units and lattice-held dmf molecules. The co-ordination octahedron around each MnIII in cludes three donors from each of the two pentadentate trianionic ligands. Both ligands asymmetrically bridge the Mn atoms affording an intra-dinuclear Mn ⋯ Mn′ separation of 3.223(1)A. The symmetry-related manganese centres are in a distorted-octahedral environment. Infrared, ESR spectroscopic, magnetic susceptibility and electrochemical studies of 1–4 evidence a variety of structural types and nuclearities. Complex 1, resulting from the reaction of manganese(II) acetate with 3NO2-H3salpro, is characterized by the MnL stoichiometry while 2, resulting from the reaction of manganese(II) acetate with Na3(3NO2-salpro), is characterized by the Mn2L stoichiometry. Two structurally different dinuclear manganese(III) complexes characterized by the same overall formulation [{MnIII(3NO2-salpro)(solvent)}2] were obtained from the reaction of 1 with O2. In non-dehydrated methanol, the asymmetric dinuclear species 3 is formed. When this complex is dissolved in dry dmf the water molecule is driven out of the manganese co-ordination sphere and a subsequent ligand environment reorganization affords 4. Variable-temperature magnetic susceptibility studies established the presence of isotropic magnetic exchange interactions between the manganese(III) centres of the dimeric species 3 and 4(J=–1.9 and –1.6 cm–1, respectively) and crystalline field anisotropy of MnIII(D=–2.6 and –2.5 cm–1, respectively). Electrochemical studies indicated that the MnII2, MnIIMnIII, MnIII2 and MnIIIMnIV oxidation states are accessible for 4 in dmf–water.

Crystal structure of aquo (hydroxo) (ethylenediaminetetraacetato) sodium(I) tin(IV), NaSn(OH)(edta)(H2O)

NaSn(OH)(edta)(H2O) is monoclinic, space groupP21/c, witha=9.747(3)Å,b=9.121(3)Å,c=16.430(6)Å, β=98.69(4)°, Å3, andZ=4. The coordination environment of Sn(IV) is a capped octahedron. Sn−O distances range from 1.990(6)Å to 2.351(7)Å. Na(I) is five coordinated to three different edta molecules. Na−O distances range from 2.283(9)Å to 2.414(7)Å. The edta ligand presents the E, G/R conformation. The crystal structure is composed of sheets parallel to (001): inside a sheet Sn(OH)(edta) molecules are connected to each other by the Na(I) interactions.