SYNTHESES ET ÉTUDES STRUCTURALES DE COMPLEXES À OXO-ANION DE L'IODE (V) : VERS DE NOUVEAUX MATERIAUX POUR L'OPTIQUE NON LINEAIRE QUADRATIQUE

The thesis focused on the synthesis of metallic iodates, materials for quadratic NLO, in order to develop optical devices with a broad band of transparency from visible to far infrared, covering the II and III transparency windows of the atmosphere. The discovery of NaI3O8, possessing the main feature of iodates, has opened the way for research and characterization of new phases containing the new oxo-anion [I3O8]- of iodine(V). DFT calculations were performed to describe the I-O bonds in the Rb2(IO3)(I3O8)(HIO3)2(H2O) compound. Furthermore, the crystal growth of millimeter size NaI3O8 crystals was performed by slow lowering of temperature and by solution circulation method to determine NLO properties on single crystals. Other phases containing the [IO3]- anion were obtained by synthesis in concentrated nitric acid solution, by hydrothermal or by solid state route under high pressure. The first characterizations of TiO(IO3)2 show a potentially interesting material for the NLO. The alternation of long and short bond lengths, similar to that observed in KTP, suggests significant charge transfer along the chains ***O-Ti-O***. Solid solutions beta -La1-XLnX(IO3)3 present a reversible structural transition in yama -La1-XLnX(IO3)3. The transition temperature for acentric phase with nonlinear properties varies according to the size and percentage of doping ions. Photoluminescence studies of some matrixes doped with Nd3+ and Yb3+ were performed.Le sujet de thèse a porté sur l'élaboration de iodates métalliques, matériaux pour l'ONL quadratique, qui permettraient de développer des dispositifs optiques à large bande de transparence du visible à l'IR lointain, couvrant les fenêtres de transparence II et III de l'atmosphère. La découverte de NaI3O8 présentant les principales caractéristiques des iodates a ouvert la voie à la recherche et caractérisation de nouvelles phases contenant le nouvel oxoanion [I3O8]- de l'iode (V). Des calculs DFT ont été effectués pour décrire les liaisons I-O dans le composé Rb2(IO3)(I3O8)(HIO3)2(H2O). En parallèle, la cristallogenèse de cristaux millimétriques de NaI3O8 a été réalisée par ALT puis par circulation pour déterminer ses propriétés ONL sur monocristaux. D'autres phases contenant l'anion [IO3]- ont été obtenues par synthèse en solution d'acide nitrique concentré, par voie hydrothermale, ou par voie solide sous haute pression. Les premières caractérisations de TiO(IO3)2 montrent que c'est un matériau potentiellement intéressant pour l'ONL. L'alternance de liaisons courtes et longues, similaire à celles observées dans KTP, laisse présager des transferts de charge importants le long des chaines ***O-Ti-O***. Les solutions solides beta-La1-xLnx(IO3)3 présentent une transition structurale displacive réversible en yama -La1-xLnx(IO3)3. La température de transition de la phase non centrosymétrique aux propriétés non linéaires évolue en fonction de la taille et du pourcentage d'ions dopants insérés. Des études de photoluminescence de certaines matrices dopées avec des ions Nd3+ et Yb3+ont été réalisées

Titanyl Iodate - A Promising Material for Infrared Nonlinear Optics Showing Structural Similarities with KTP

International audienceA new nonlinear compound, TiO(IO3)2, was synthesized by the hydrothermal method and characterized by single-crystal X-ray diffraction. It crystallizes in the acentric Cmc21 space group with the following lattice parameters: a = 10.222(1) Å, b = 8.254(1) Å, c = 7.277(1) Å, and V = 613.98(13) Å3. The structure has alternating Ti-O bond lengths, short [Ti-O 1.733(12) Å, titanyl bond] and long [Ti-O 2.113(12) Å], as observed in the KTiOPO4 (KTP) material. IR spectroscopy and NLO efficiency studies on a powder sample suggest that TiO(IO3)2 is a good potential NLO material

A Journey in Lanthanide Coordination Chemistry: From Evaporable Dimers to Magnetic Materials and Luminescent Devices

International audienceConspectus. Lanthanide ions are prime ingredients for the design of compounds, materials, and devices with unique magnetic and optical properties. Accordingly, coordination chemistry is one of the best tools for building molecular edifices from these ions because it allows careful control of the ions’ environment and of the dimensionality of the final compound.In this Account, we review our results on lanthanide-based dimers. We show how a pure fundamental study on lanthanide coordination chemistry allows the investigation of a full continuum of results from the compound to materials and then to devices. The conversion of molecules into materials is a tricky task because it requires strong molecular robustness toward the surface deposition processes as well as the preservation and detectability of the molecular properties in the material. Additionally, the passage of a material toward a device implies a material with a given function, for example, a tailored response to an external stimulus.To do so, we targeted neutral and isolated molecules whose transfer on surfaces by chemi- or physisorption is much easier than that of charged molecules or extended coordination networks. Then, we focused on molecules with very strong evaporability to avoid wet chemistry deposition processes that are more likely to damage the molecules and/or distort their geometries.We thus designed lanthanide dimers based on fluorinated β-diketonates and pyridine-N-oxide ligands. As expected, they show remarkable evaporability but also strong luminescence and interesting magnetic behavior because they behave as single-molecule magnets (SMMs). Ligand substitutions and stoichiometric modifications allow the optimization of the geometric organization of the dimers in the crystal packing as well as their evaporability, SMM behavior, luminescent properties, or their ability to be anchored on surfaces. Most of all, this family of molecules shows a strong ability to form thick films on various substrates. This allows converting these molecules to magnetic materials and luminescent devices.Magnetic materials can be designed by creating thick films of the dimers deposited on gold. These films have been designed and investigated with the most advanced techniques of on-surface imaging (atomic force microscopy, AFM), on-surface physicochemical characterization (X-ray photoelectron spectroscopy (XPS), time of flight-secondary ion mass spectroscopy (Tof-SIMS)), and on-surface magnetic investigation (low-energy muon spin relaxation (LE-μSR)). Contrary to what was previously observed on other SMM films, no depth dependence of the SMM behavior was observed. This means that the dimers do not suffer from the vacuum or substrate interface and behave similarly, whatever their localization. This exceptional magnetic robustness is a key ingredient in the creation of materials for molecular magnetic data storage.Luminescent devices can be obtained by layering molecular films of the dimers with a copper-rich solid-state electrolyte between ITO/Pt electrodes. The electromigration of Cu(2+) ions into films of Eu(3+), Tb(3+), and Dy(3+) dimers quenches their luminescence. This luminescence tuning by electromigration is reversible, and this setup can be considered to be a proof of concept of full solid-state luminescent device where reversible coding can be tailored by an electric field. It is envisioned for optical data storage purposes. In the future, it could also benefit from the SMM properties of the molecules to pave the way toward multifunctional molecular data storage devices

Luminescence and mechanoluminescence of Ba4Si6O16:Eu2+, RE phosphors

International audienceThe luminescence properties of green Ba4Si6O16:Eu2+, rare-earths (RE) (RE = Sc, Y, La and Lu except Pm) phosphors are reported. Their long-lasting phosphorescence is discussed in view trap depths concentrations determined from thermally stimulated experiments. A second emission band centered at 439 nm was evidenced low temperatures, which stems the substitution Eu2+ two non-equivalent Ba2+ sites Ba4Si6O16. mechanoluminescence RE described, a new mechanism proposed, case where Ho3+, involving distribution 0.694 to 0.924 eV. Mechanical loading (post UV irradiation) induces decrease depth distribution, leading an increase intensity, whereas drop intensity observed upon unloading, following faster release charge carriers

Evidence of reaction intermediates in microwave-assisted synthesis of SHG active α-La(IO 3 ) 3 nanocrystals

International audienceWe explore here how, under microwave assisted hydrothermal process, various synthesis conditions influence the formation of different lanthanum iodate compounds: α-La(IO3)3, La(IO3)3(H2O), La(IO3)3(HIO3) and La(IO3)2.66(OH)0.66. Whatever the intial [La 3+ ]:[IO3-] ratio, α-La(IO3)3 crystallizes if the synthesis temperature exceeds 220°C. Phase transformations in solid state or under hydrothermal synthesis are also discussed. Interestingly, we evidence the full phase transformation under hydrothermal synthesis from the new hydrate form La(IO3)3(H2O) into stable and optically active α-La(IO3)3 through an appropriate hydrothermal process. This evolution can be explained by structural rearrangements of the coordination sphere of lanthanum atoms, stabilizing the structure

Mono-, Di-, and Tetranuclear Manganese(II) Complexes with p-Phenylsulfonylcalix[4]arene Macrocycles as Ligand Antennas: Synthesis, Structures, and Emission Properties

International audienceThree manganese(II) coordination compounds with a p-phenylsulfonylcalix[4]arene (ppThiaSO2) ligand were synthetized and are denoted as follows: [MnII(ppThiaSO2)(DMF)4] (1) (DMF = N,N-dimethylformamide), [Mn2II(ppThiaSO2)(DMF)6] (2), and K[Mn4II(ppThiaSO2)2F] in the form of two pseudo-polymorphs (3a and 3b). Their electronic emission spectra were studied in the solid state at different temperatures and at various excitation wavelengths. All compounds (2, 3a, and 3b) except 1 present luminescent properties at UV excitation wavelength, with emission maxima centered at 695, 602, and 675 nm, respectively. Their structural and optical properties were compared to those of previously reported analogous compounds bearing the p-tert-butylsulfonylcalix[4]arene (ThiaSO2) ligand. The luminescence of these complexes was attributed to the spin-forbidden 4T1→ 6A1d-d transition of manganese(II). The emission depends on the coordination of the metal center, the conformation of the macrocycle, and the structural packing. Hereafter, we present the synthesis, structure, and excitation and emission spectra of each compound, together with the dependence of the emission quenching on molecular dioxygen. © 2022 American Chemical Society. All rights reserved

Hexanuclear Molecular Precursors as Tools to Design Luminescent Coordination Polymers with Lanthanide Segregation

International audienceSolvothermal reactions between hexanuclear complexes with the general chemical formula [Ln(μ-O)(μ-OH)(NO)(HO)]·2NO·2HO and 2-bromobenzoic acid (2-bbH) lead to a series of isostructural one-dimensional coordination polymers with the general chemical formula [Ln(2-bb)] with Ln = Sm, Eu, Tb, Dy, and Y. These coordination polymers crystallize in the orthorhombic space group 2 (No. 43) with the following cell parameters: = 29.810(3) Å, = 51.185(6) Å, = 11.7913(14) Å, = 17992(4) Å, and = 16. The europium- and terbium-based derivatives show sizable luminescence intensities under UV excitation. Isostructural heterolanthanide coordination polymers have also been prepared. Their luminescent properties suggest that during the synthetic process the starting hexanuclear complexes are destroyed but strongly influence the distribution of the different lanthanide ions over the metallic sites of the crystal structure. Indeed, it is possible to prepare heterolanthanide coordination polymers in which lanthanide-ion segregation is controlled

Differences and Similarities between Lanthanum and Rare-Earth Iodate Anhydrous Polymorphs: Structures, Thermal Behaviors, and Luminescent Properties

International audienceThe Ln(IO)(HIO) (y = 1 or 1.33) compounds are isostructural with the La(IO)(HIO) phases, but thermal studies reveal different behaviors. On the one hand, the partial thermal decompositions of these lanthanide compounds lead to the Ln(IO) formulation, with a room temperature structure different from the β-La(IO) obtained from La(IO)(HIO). On the other hand, the partial thermal decompositions of the LaLn(IO)(HIO) compounds prepared with lanthanides ions (Ce, Pr, Nd, Sm, Eu, Gd, and Yb) lead to acentric β-LaLn(IO). As for β-La(IO), reversible structural transitions from β-LaLn(IO) to centrosymmetric γ-LaLn(IO) are observed. Differential scanning calorimetry analyses of LaLn(IO) solid solutions show that the transition temperatures vary with the lanthanide concentration in the solid solution. A transition is observed only up to a certain fraction of lanthanide-ion substitution; this substitution limit decreases with the cationic radius of the lanthanide ion. Finally, the β-LaNd(IO) and β-LaYb(IO) phases are investigated by luminescence spectroscopy

Microwave-assisted synthesis of lanthanide coordination polymers with 2-bromobenzoic acid as ligand from hexa-lanthanide molecular precursors

International audienceMicrowave-assisted reactions, between 2-bromobenzoic acid (2-bbH) and hexa-lanthanide molecular precursors of general chemical formula Ln6(µ6-O)(µ3-OH)8(NO3)6(H2O)12·2NO3·2H2O [Ln6], lead to iso-structural 1D coordination polymers of general chemical formula [Ln(2-bb)3]∞ with Ln = Eu, Tb or Dy. These compounds crystallize in the monoclinic system, space group P21/c (n°14), with the following cell parameters (for the Dy-derivative): a = 12.3809(10) Å, b = 21.8653(16) Å, c = 7.9119(7) Å, β = 98.709(3)°, V = 2117.2(3) Å3 and Z = 4. The influence of the hexa-nuclear precursors over the final coordination polymer is demonstrated. Indeed, while the hexa-nuclear complexes collapse during the synthetic process their progressive destruction affords a unique 1D coordination polymer that cannot be readily obtained otherwise. Additionally, some iso-structural hetero-lanthanide derivatives with general chemical formulas [EuxTb1-x(2-bb)3]∞ and [YxTb1-x(2-bb)3]∞ with 0 ≤ x ≤ 1 have been prepared from the corresponding hexa-nuclear complexes [Eu6xTb6-6x] and [Y6xTb6-6x], respectively. Luminescent properties have been recorded and colorimetric coordinates have been calculated for all the compounds. These measurements indicate that the molecular chains host strong intermetallic energy transfers

Controlling Lanthanide Exchange in Triple-Stranded Helicates: A Way to Optimize Molecular Light-Upconversion

The kinetic lability of hexadentate gallium-based tripods is sufficient to ensure thermodynamic self-assembly of luminescent heterodimetallic [GaLn(L3)3]6+ helicates on the hour time scale, where Ln is a trivalent 4f-block cation. The inertness is, however, large enough for preserving the triplehelical structure when [GaLn(L3)3]6+ is exposed to lanthanide exchange. The connection of a second gallium-based tripod further slows down the exchange processes to such an extent that spectroscopically active [CrErCr(L4)3]9+ can be diluted into closed-shell [GaYGa(L4)3]9+ matrices without metal scrambling. This feature is exploited for pushing molecularbased energy-transfer upconversion (ETU) at room temperature