Jean Le Bideau

Immobilization of ionic liquids in translucent tin dioxide monoliths by sol–gel processing

SnO2 translucent monolith ionogels were obtained by a sol-gel processing using bis(2-methylbutan-2-oxy)di(pentan-2,4-dionato)tin as a precursor in the presence of various ionic liquids: [BMI][Br], [BMI][TFSI], [BMI][BF4]. The confinement of ionic liquids within the gels was evidenced by Differential Scanning Calorimetry, FTIR and FT-Raman spectroscopy. The ionic liquids could be efficiently washed off, which resulted in supermicroporous solids. Calcination in air at 550 degrees C of the dried monoliths resulted in nanoporous nanocrystalline cassiterite tin dioxide particles with crystallite sizes of about 8-12 nm and mean pore sizes around 5 nm.

Structural and magnetic studies of the [Mn12O12(CH3COO)16(H2O)4]·2CH3COOH·4H2O thermal derivatives

Thermal transformations of the well-known high spin manganese carboxylate cluster [Mn12O12(CH3COO)16(H2O)4]·4H2O·2CH3COOH have been studied in detail. Three steps in its thermal transformation have been observed with the successive formation of well-defined compounds. Upon heating at 403 K, acetic acid and water molecules located in inter-cluster void spaces are removed without significant modification of the structural packing and magnetic properties. Interestingly, the resulting material presents the remarkable property of being able to incorporate ammonia into its structure. Dramatic changes in the magnetic properties of this insertion compound have been observed and confirmed the first synthesis of a single-molecule magnet material by gas inclusion. Further heating at 513 K stabilizes the hausmannite Mn3O4 phase as indicated by X-ray diffraction, thermogravimetric analyses and magnetic measurements. Finally, heating of the compound above 573 K leads to a mixture of different manganese compounds, Mn3O4 and MnCO3, previously observed in the decomposition of Mn(CH3COO)2·4H2O.

Redox-active pH-responsive molecules: ferrocenylphosphonic acid, ferrocenylmethylphosphonic acid and 1,1′-ferrocenylbisphosphonic acid. Structural determination of FcPO3Na2·5H2O

The acidity constants of the reduced and oxidized species of ferrocenylphosphonic acids FcPO3H2, FcCH2PO3H2 and fc(PO3H2)2 (Fc = (eta5-C5H5)Fe(eta5-C5H4), fc = (eta5-C5H4)Fe(eta5-C5H4)) in water have been evaluated by potentiometric, 31P NMR, and electrochemical methods. The oxidized forms are more acidic than the reduced ones. The interaction between the redox centre and the charged oxygen atoms of the phosphonate group is shown to be electrostatic. The maximum oxidation shift DeltaE between the protonated and unprotonated species increases with the number of charges of the substrate and decreases with the increase of the distance between the ferrocenyl centre and the oxygen atoms of the phosphonate group. The structure of FcPO3Na2.5H2O is determined. The compound crystallizes in the monoclinic system. It is lamellar with an inorganic layer formed by tetramers Na4O14, the ferrocenyl groups occupying the interlamellar space.