Dynamic Coordination Chemistry of Fluorinated Zr-MOFs: Synthetic Control and Reassembly/Disassembly Beyond de Novo Synthesis to Tune the Structure and Property

Known for excellent stability, porosity and functionality, the high-valent Zr⁴⁺ metal–organic frameworks (Zr-MOFs) still meets synthetic challenge in modulating the strength of Zr-O_carboxylate linkage. Herein we explore the unusual coordination dynamics of fluorinated Zr-MOFs by designing two trifluoromethyl modified ligands with distinct geometry preference to form a family of thermodynamic and kinetic products. The low-connecting kinetic Zr-MOFs possess substitutable coordination sites to endow Zr₆-cluster with extra dynamic behaviors, thus opening a post-synthetic pathway to sequential reassembly/disassembly processes. Comprehensive factors, including ligand geometry, Zr₆-cluster connectivity, acid modulator and reaction temperature/concentration, have been studied for controllable syntheses. The stability, hydrophobicity and gas adsorption/separation properties of obtained Zr-MOFs are explored. This work sheds light on the understanding of the dynamic coordination chemistry of Zr-MOFs beyond strong Zr−O bond, which poses a versatile platform for modification and functionalization of Zr-MOFs.     

Efficient BOP-mediated synthesis of fulgimides

A mild and efficient method for the synthesis of fulgimides is presented in which the peptide coupling reagent BOP is employed for dehydratation of fulgenic acid monoamides (succinamic acids). The disclosed method proved to be superior to those described in the literature.     

Selective reflection spectroscopy at the interface between a calcium fluoride window and Cs vapour

A special vapour cell has been built, that allows the measurement of the atom–surface van der Waals interaction exerted by a CaF₂ window at the interface with Cs vapour. Mechanical and thermal fragility of fluoride windows make common designs of vapour cells impractical, so that we have developed an all-sapphire sealed cell with an internal CaF₂ window. Although some impurities have remained when filling up the prototype cell, leading to line broadening and a shift, the selective reflection spectrum of the Cs D₁ line (894 nm) makes apparent the weak van der Waals surface interaction. The uncertainties introduced by the effects of these impurities in the van der Waals measurement are nearly eliminated when comparing the selective reflection signal at the CaF₂ interface of interest and at a sapphire window of the same cell. The ratio of the interactions respectively exerted by a sapphire interface and a CaF₂ interface is found to be 0.55±0.25, in good agreement with the theoretical evaluation of ∼0.67. PACS 34.35.+a; 42.62.Fi; 42.70.Km     

Experimental evidence supported by simulations of a very high H2 diffusion in metal organic framework materials

Quasielastic neutron scattering measurements are combined with molecular dynamics simulations to extract the self-diffusion coefficient of hydrogen in the metal organic frameworks MIL-47(V) and MIL-53(Cr). We find that the diffusivity of hydrogen at low loading is about 2 orders of magnitude higher than in zeolites. Such a high mobility has never been experimentally observed before in any nanoporous materials, although it was predicted in carbon nanotubes. Either 1D or 3D diffusion mechanisms are elucidated depending on the chemical features of the MIL framework.     

On incomplete orthogonal arrays

First we prove that, if an incomplete orthogonal array (1, r, s, k, t) does exist, then s ?(r ? t + 1)k. Next, we establish a relation between the existence of incomplete orthogonal arrays and the existence of orthogonal arrays. From this relation, we may bring out the upper bounds of the maximum number of contraints.     

Infrared properties of TMTTF fluoborates

An attempt is done to explain the transmission behaviour of two TMTTF fluoborates within molecular frequencies region, with an electron-phonon coupling phenomenological model. In the far infrared region, the libration spectrum which comes out at low temperature, allows us to infer that BF₄ pyramid orientation fluctuate during the time.     

Synthesis of 4-Oxo-1,2,3,4-tetrahydropyridine (2,3-Dihydro-4(1H)pyridinone)

N-Ethoxycarbonyl-4-pyridone is reduced to N-ethoxycarbonyl-4-oxo-1, 2, 3, 4-tetrahydropyridine by sodium borohydride in t-butyl alcohol containing ethyl chloroformate. Saponification of the product leads to 4-Oxo-1, 2, 3, 4-tetrahydropyridine.     

Sur les composes fluores et oxyfluores du tellure (IV) : Synthese,caracterisation et etude structurale de l'acide trioxotetrafluoroditellurique (IV), H2Te2O3F4

The trioxotetrafluoroditelluric (IV) acid, H₂Te₂O₃F₄, was synthetized in fluorhydric solution and characterized by X-ray powder diffraction. The structure was solved by means of three-dimensional Patterson synthesis (final R value = 0,026). This structure is characterized by Te₂O₃F₄ groups linked by hydrogen bonds to form a very distorted diamond network.