Spectres Raman et spectres infrarouges des chlorobromométhanes

Nous avons étudié le trichloromonobromo, le dicllorodibromo et le monochlorotribomométhane Pour chacun de ces corps nous avons déterminé le spectre Raman et le spectre d'absorption dans l'infrarouge. Nous avons ensuite essayé de donner une interprétation des résultats obtenus en les reliant à la structure moléculaire de ces différents corps. Les spectres Raman et les spectres d'absorption dans l'infrarouge sont en liaison avec la structure des composés étudiés. En opérant sur des corps dont la structure a été déterminé par des considérations chimiques, on peut espérer relier les spectres obtenus aux divers modes de vibrations des atomes dans la molécule. Nous avons étudié dans ce but les ohlorobromométilanes

Series of hydrated heterometallic uranyl-cobalt(II) coordination polymers with aromatic polycarboxylate ligands: Formation of U=O—Co bonding upon dehydration process

Five new heterometallic UO22+-Co2+ coordination polymers have been obtained by hydrothermal reactions of uranyl nitrate and metallic cobalt with aromatic polycarboxylic acids. Single-crystal X-ray diffraction reveals the formation of four 3D frameworks with the mellitate (noted mel) ligand and one 2D network with the isophthalate (noted iso) ligand. The compounds [(UO2(H2O))2Co(H2O)4(mel)]·4H2O (1), [UO2Co(H2O)4(H2mel)]·2H2O (2), and [(UO2(H2O))2Co(H2O)4(mel)] (4) consist of 3D frameworks built up from the connection of mellitate ligands and mononuclear metallic centers. These three compounds exhibit two types of geometry for the uranyl cation: pentagonal bipyramidal environment for 1 and 4, and hexagonal bipyramidal environment for 2. Using the mellitate ligand, the uranyl dinuclear unit is isolated in the compound [(UO2)2(OH)2(Co(H2O)4)2(mel)]·2H2O (3). Due to their 2D framework and the presence of uncoordinated cobalt(II) cations, the compound [(UO2)(iso)3][Co(H2O)6]·3(H2O) (5) is drastically different than the previous one. The thermal behavior of compounds 1, 2, and 3 has been studied by thermogravimetric analysis, X-ray thermodiffraction, and in situ infrared. By heating, the dehydration of compounds 1 and 2 promotes two structural transitions (1 → 1′ and 2 → 2′). The crystal structures of [(UO2(H2O))2Co(H2O)2(mel)] (1′) and [(UO2)Co(H2mel)] (2′) were determined by single-crystal X-ray diffraction; each of them presents a heterometallic interaction between uranyl bond and the Co(II) center. Due to the rarely reported coordination environment for the cobalt center in compound 2′ (square pyramidal configuration), the magnetic properties and EPR characterizations of the compounds 2 and 2′ were also investigated

State of the art in visible-light photocatalysis of aqueous pollutants using metal-organic frameworks

International audienceThis review focuses on the many research that have been undertaken in visible-light driven environmental photocatalysis field employing Metal-Organic Framework (MOF) materials for the removal of aqueous pollutants. Correlations between their structural and functional features, and the reactional pathways for pollutant degradation were also addressed, with a particular emphasis on the syntheses and on the charge transfer complexes occurring in the MOF compounds. The extensive possibilities for modifying the properties of MOFs in diverse applications were critical while dealing with a variety of contaminants with different properties. Indeed, because of the infinite number of combinations of different inorganic poly-oxo clusters and organic linkers, and to the possibility of tailoring other variables such as functional groups, pore size, defects, and incorporation of other materials (dyes, semiconductors, metal nanoparticles, covalent organic frameworks, carbon-based materials, magnetic compounds, and inert carriers), MOFs have a high potential to lead the photocatalytic field. Furthermore, the use of mixed methods has shown to be a legitimate and fascinating technique for further developing these systems while considering their strengths and weaknesses. Despite considerable advancements in MOF-based photocatalysts, significant obstacles remain. However, the research of heterogeneous photocatalysis dates back to the 1970 s, but the discussion of MOF materials is even more recent, with just a few decades spent investigating these systems. Nonetheless, tremendous breakthroughs in this area have been made, from structural design to computer simulations, and reports of various MOF materials have constantly increased in the previous several years. As a result, combining the collaborative efforts of researchers from many domains, the future appears to hold promising prospects for MOF-based photocatalysts

Synthesis and structural characterization of the first neptunium based metal–organic frameworks incorporating {Np 6 O 8 } hexanuclear clusters

International audienc

Probing ²⁷Al-¹³C proximities in metal-organic frameworks using dynamic nuclear polarization enhanced NMR spectroscopy

We show how 27Al-13C proximities in the microporous metal-organic framework MIL-100(Al) can be probed using advanced 27Al-13C NMR methods boosted by Dynamic Nuclear Polarization