Isabelle Gautier-Luneau

New materials for infrared non-linear optics. Syntheses, structural characterisations, second harmonic generation and optical transparency of M(IO3)3 metallic iodates

Two new phases α-In(IO3)3 and β-In(IO3)3 have been synthesised by evaporation of concentrated nitric acid solution containing metallic salts and sources of iodate. Single crystal structures reveal an acentric three-dimensional network for α-In(IO3)3 and a centrosymmetric two-dimensional network for β-In(IO3)3. Temperature-dependent X-ray powder diffraction experiments shows the transformation of α-In(IO3)3 to β-In(IO3)3 at 365 °C. The phase transition is not reversible. α-In(IO3)3 is the kinetically favoured phase whereas β-In(IO3)3 is the thermodynamically stable phase. α-In(IO3)3 is isomorphic to Cr(IO3)3, Fe(IO3)3 and Ga(IO3)3 and crystallises in space group P63 (no. 173) with a = 9.541(1) A and c = 5.266(1) A. Structural relationships among the anhydrous non-centrosymmetric metallic iodates M(IO3)3 (M = Cr, Fe, In, Ga), M(IO3)2 (M = Mg, Mn, Co, Ni, Zn) and α-LiIO3 are described. Structural analogies between these metallic iodates allow us to prepare solid solutions as In1−xFex(IO3)3 and In1−xCrx(IO3)3. Luminescence of the In1−xCrx(IO3)3 phases has been observed. DSC analyses of β-In(IO3)3 and Ga(IO3)3 show that they decompose at 535 °C and 525 °C respectively. Fe(IO3)3, Ga(IO3)3 and α-In(IO3)3 generate second harmonics and have high non-linear coefficients and high optical damage thresholds in powder form. Furthermore, they do not absorb up to 12 µm. Consequently, they possess a large domain of transparency from visible light to the beginning of the far-infrared, including three atmospheric transparency windows. They are particularly interesting for potential applications in quadratic non-linear optics in atmospheric transparency bands II and III.

Coordination of Ferrocenyl Ligands Bearing bipy Subunits: Electrochemical, Structural and Spectroscopic Studies

The coordinative properties of mono(bipy) and bis(bipy) (bipy refers to 6or 6,6 -substituted 2,2 -bipyridine) carbonyloxyand carboxamido-bridged derivatives of ferrocene L1−5 towards a number of metal cations (CuI, CuII, NiII, FeII, CoII, HgII, PbII, AgI) have been investigated by the interplay of voltammetry, mass spectrometry and X-ray diffraction studies. Particular attention was paid to the electrochemical recognition properties of these redox-active ligands, as monitored by modulation of the ferrocene/ferricinium redox couple upon complexation. It was found that the bis(bipy)bridged ligands exhibit a sandwich effect that gives rise to a

Crystal structure of M(IO3)2 metal iodates, twinned bypseudo-merohedry, with MII: MgII, MnII, CoII, NiII and ZnII

Abstract The non-centrosymmetric materials Zn(IO3)2, Mn(IO3)2, Co(IO3)2, Mg(IO3)2 and β-Ni(IO3)2 have been synthesised by evaporation of nitric acid solutions of metal salts and lithium iodate. All these compounds are isostructural and their structures were characterised both by X-ray diffraction on powder and single crystals. They crystallise in the monoclinic crystal system, space-group type P21 (no. 4) with a pseudo-hexagonal lattice, as shown by the lattice parameters of Mn(IO3)2 for example: a = 11.247(1) Å, b = 5.045(1) Å, c = 11.246(1) Å, β = 120.02(1)°, V = 552.5(1) Å3, Z = 4. This monoclinic symmetry with a ∼ c and β ∼ 120° leads to a three-individual pseudo-hexagonal twin by pseudo-merohedry. The structure reveals a three-dimensional network in which each octahedrally coordinated cation is linked to ten others via iodate bridges. All these metal iodates generate second harmonics.

Structure, Bonding, and Stability of Mercury Complexes with Thiolate and Thioether Ligands from High-Resolution XANES Spectroscopy and First-Principles Calculations

We present results obtained from high energy-resolution L3-edge XANES spectroscopy and first-principles calculations for the structure, bonding, and stability of mercury(II) complexes with thiolate and thioether ligands in crystalline compounds, aqueous solution, and macromolecular natural organic matter (NOM). Core-to-valence XANES features that vary in intensity differentiate with unprecedented sensitivity the number and identity of Hg ligands and the geometry of the ligand environment. Post-Hartree-Fock XANES calculations, coupled with natural population analysis, performed on MP2-optimized Hg[(SR)2···(RSR)n] complexes show that the shape, position, and number of electronic transitions observed at high energy-resolution are directly correlated to the Hg and S (l,m)-projected empty densities of states and occupations of the hybridized Hg 6s and 5d valence orbitals. Linear two-coordination, the most common coordination geometry in mercury chemistry, yields a sharp 2p to 6s + 5d electronic transition. This transition varies in intensity for Hg bonded to thiol groups in macromolecular NOM. The intensity variation is explained by contributions from next-nearest, low-charge, thioether-type RSR ligands at 3.0-3.3 Å from Hg. Thus, Hg in NOM has two strong bonds to thiol S and k additional weak Hg···S contacts, or 2 + k coordination. The calculated stabilization energy is -5 kcal/mol per RSR ligand. Detection of distant ligands beyond the first coordination shell requires precise measurement of, and comparison to, spectra of reference compounds as well as accurate calculation of spectra for representative molecular models. The combined experimental and theoretical approaches described here for Hg can be applied to other closed-shell atoms, such as Ag(I) and Au(I). To facilitate further calculation of XANES spectra, experimental data, a new crystallographic structure of a key mercury thioether complex, Cartesian coordinates of the computed models, and examples of input files are provided as Supporting Information .

Synthesis, electrochemistry and complexation studies of ferrocene crown ethers

Abstract Voltammetric and UV spectrophotometric investigations of alkali and alkaline earth metal cations binding by the new ferrocene macrocyclic ligands 1–4 have been performed in acetonitrile electrolyte. Stability constants were determined from UV measurements. All the metal cations surveyed formed 1:1 stoichiometric complexes with 2 and 3 , with the exception of barium which produced a 1:2 intermolecular sandwich complex with 2 . No complexation occurred with 1 . Electrochemical studies have demonstrated that the binding of Li + , Na + , K + , Mg 2+ , Ca 2+ and Ba 2+ with 2 resulted in shifts of the ferrocene oxidation wave to more positive potentials. The same features were observed with 3 in the presence of Li + , Na + , K + and Mg 2+ , and with 4 and Ba 2+ . In contrast, a different type (two-wave behaviour) of positive shift revealed the binding of Ca 2+ and Ba 2+ with 3 , allowing the amperometric titration of these metal cations. The magnitude and the type of potential shift could not be related to the radius and charge to radius ratio of the cations, or to the strength of the host-guest association. It can be assumed that additional effects such as an effective charge transfer interaction between the cationic guest and the redox centre control the electrochemical recognition behaviour of these redox ionophores. Single crystal X-ray structure of [ 3 -Ba](ClO 4 ) 2 has also been determined to gain better understanding of the barium complextion in 3 .

New stereoselective reaction of methylglyoxal with 2-aminopyridine and adenine derivatives: Formation of imino acid-nucleic base derivatives in water under mild conditions

A remarkable stereoselective reaction of methylglyoxal with 2-aminopyridine, the nucleic base adenine and adenine nucleosides leads in good yield to heterocycles of a new family in water under mild conditions and should be of interest in the understanding of the biological effects of methylglyoxal which is toxic, mutagenic and involved in diabetic complications.

Structures, Thermal Behaviors, and Luminescent Properties of Anhydrous Lanthanum Iodate Polymorphs

The structural and thermal studies of six anhydrous lanthanum iodate polymorphs are presented. The variation of the [IO3(-)]:[La(3+)] molar ratio in the starting solution and the evaporation rate of the solution leads to either the centric La(IO3)3(HIO3) or the acentric La(IO3)3(HIO3)1.33 phases. The crystal structure of La(IO3)3(HIO3)1.33 was determined. The thermal treatments of these two phases up to 490 °C lead to β-La(IO3)3, observed at room temperature. To better understand the similar thermal behaviors of La(IO3)3(HIO3)1.33 and La(IO3)3(HIO3) compounds and their structural evolution, thermogravimetry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC) analyses and in situ temperature-dependent powder X-ray diffraction (XRD) experiments were carried out. These experiments allowed us to highlight the successive formation of δ-La(IO3)3 and γ-La(IO3)3. δ-La(IO3)3 is observed from the beginning of thermal decomposition of La(IO3)3(HIO3)1.33 (at 340 °C) or La(IO3)3(HIO3) (at 300 °C) up to 440 °C. A phase transition from δ-La(IO3)3 to γ-La(IO3)3 then occurs at 440 °C. Finally, the phase transition from γ-La(IO3)3 to β-La(IO3)3 occurs at 140 °C. A cycle of heating and cooling shows the reversible phase transition at 185 and 140 °C, respectively. β-, γ-, and δ-La(IO3)3 are three polymorph phases of the first α-La(IO3)3 already characterized. The structure of β-La(IO3)3 and γ-La(IO3)3 were determined on powder XRD analyses. The iodate compounds present a very broad domain of transparency from the visible range to the beginning of the far-infrared range. The intensities of SHG light generated by α-La(IO3)3, β-La(IO3)3, La(IO3)3(HIO3)1.33, and α-LiIO3 compounds with acentric structures were compared: β-La(IO3)3 < La(IO3)3(HIO3)1.33 < α-La(IO3)3 ≈ α-LiIO3. Finally, the luminescence spectroscopy of La(IO3)3(HIO3)1.33:Nd(3+), α-La(IO3)3:Nd(3+), and α-La(IO3)3:Yb(3+) is studied.

Optical properties of Nd3+ and Yb3+ -doped metal iodates (AgM(IO3)4): transparent host matrices for mid-IR lasers and nonlinear materials

Nine new isomorphic iodate compounds NaM(IO3)4 with M ¼ Y, Nd, Gd and AgM0(IO3)4 with M0 ¼ Y, La, Nd, Eu, Gd, Bi have been synthesized either by evaporation of concentrated nitric acid solution or by hydrothermal synthesis. They crystallize in the monoclinic acentric Cc space group. Typical unit cell parameters for AgY(IO3)4 are a ¼ 31.277(3) °A, b ¼ 5.547(1) °A, c ¼ 12.556(2) °A, b ¼ 91.11(2) , V ¼ 2178.0(6) °A3 and Z ¼ 8. Crystal structures have been solved on single crystals for NaY(IO3)4, AgY(IO3)4, AgLa(IO3)4, AgGd(IO3)4 and AgBi(IO3)4 and on powder for NaNd(IO3)4, NaGd(IO3)4, AgEu(IO3)4 and AgGd(IO3)4. They are thermally stable up to 550 C for NaY(IO3)4, 430 C for AgY(IO3)4, 500 C for AgLa(IO3)4 and 490 C for AgBi(IO3)4. The crystal structure reveals a two-dimensional layered network. The sheets are connected together by I/O interactions. All these metal iodates generate second harmonics and are transparent up to 12µm. So they are interesting as potential laser matrices in the mid and beginning of the far-infrared. The properties of Nd3+ and Yb3+-doped AgGd(IO3)4 and of Nd3+-doped AgLa(IO3)4 have been studied.

Separation of Geometric Isomers of a Dicopper Complex by Using a 19F-Labeled Ligand: Dynamics, Structures, and DFT Calculations

Introducing a fluorine group on two pyridines of the HL(CH(3)) ligand (2,6-bis[(bis(2-pyridylmethyl)amino)methyl]-4-methylphenol) allows the separation of two geometric isomers after complexation by two copper(II) ions. Methods for isolating the isomers (1(meso) and 1(rac)) as a mu-phenoxo,mu-hydroxo dicopper(II) complex as a crystalline product have been developed. Both isomers (1(meso) and 1(rac)) have been characterized by X-ray crystallography and (19)F NMR. The isomerism is determined by the disposition of the fluorine atoms with respect to the plane containing the Cu(2)O(2) core. Density functional theory calculations using different functionals were performed to provide additional support for the existence of these two forms. Dissolution of 1(meso) in acetone or acetonitrile causes its spontaneous isomerization into the 1(rac) form at room temperature. Combined experimental studies (UV-vis, (19)F NMR) and theoretical calculations support this process. Paramagnetic (19)F NMR appears as a unique and powerful probe for distinguishing the two isomers and supplying direct evidence of this isomerization process in solution.

Electron delocalisation in a trinuclear copper(II) complex: high-field EPR characterization and magnetic properties of Na3[Cu3(mal)3(H2O)]·8H2O

The complex Na3[Cu3(mal)3(H2O)] x 8H2O was obtained from evaporation of an aqueous solution containing Cu(OAc)2, malic acid (HO2CCH2CHOHCO2H) and NaOH and was characterised by X-ray diffraction on single crystal, X-band and high-field EPR spectroscopy (HF-EPR) and magnetic susceptibility measurements. The trinuclear complex [Cu3(mal)3(H2O)]3- is trapped in a three-dimensional network with sodium cations. The three copper atoms are connected by alkoxo bridges and form an almost isosceles triangle with Cu...Cu distances of 3.076(1), 3.504(1) and 3.513(1) A. Two of the copper ions are also bridged by an extra aquo ligand. EPR spectroscopy combined with magnetic susceptibility measurements provide a powerful tool to resolve the electronic structure of the complex. The overall magnetic behaviour corresponds to an antiferromagnetically coupled triangular system. The 285 GHz-EPR spectrum (g = 2; 10.18 T) is characteristic of a spin state S = 1/2, with a rhombic anisotropy of [g]. This rhombic pattern allows us to propose that the electronic spin density is delocalised on the three copper ions.