Herein, we report the synthesis of N-tert-butoxycarbonyl (BOC) protected [V 6 O 13 {(OCH 2) 3 C-NH 2 } 2 ] 2built from the Lindqvist-type hexavanadate. The reaction of di-tert-butyl dicarbonate (BOC 2 O) with tris(hydroxymethyl)aminomethane (Tris) led to the organic derivative [(OCH 2) 3 C-NH(BOC)] that reacts with the decavanadate in dimethylacetamide (DMA) to form the [V 6 O 13 {(OCH 2) 3 C-NH(BOC)} 2 ] 2anions. The tetrabutylammonium (TBA +) salt of this hybrid polyoxovanadate, TBA 2 [V 6 O 13 {(OCH 2) 3 C-NH(BOC)} 2 ]•2DMA, has been characterized in the solid-state by single crystal X-ray diffraction and infrared spectroscopy, and in solution by multinuclear (1 H, 13 C and 51 V) and DOSY NMR, and UV-visible spectroscopy.
It
is well known that the trivacant anions α-B–[XW9O33]9– react with vanadyl ions
to give the sandwich-type polyoxometalates [(VIVO)3(XW9O33)2]12– with X = AsIII or SbIII. Nevertheless, the
oxidized derivatives have been obtained selectively by electrochemical
oxidation from the fully reduced derivatives [(VIVO)3(XW9O33)2]12– allowing full characterization both in solution using UV–vis
and multinuclear (17O, 51V, and 183W) NMR spectroscopies and in the solid state by single-crystal X-ray
diffraction. Structural analysis of the oxidized [(VVO)3(XW9O33)2]9– polyanions is consistent with the idealized D
3h
symmetry, while solution studies reveal
a fair hydrolytic stability in a wide pH range from 0 to 6. Besides,
the D
3h
polyanions either
as reduced or oxidized forms [(VO)3(AsW9O33)2]9/12– have been identified
as the thermodynamic product that results from the conversion of the C
2v
polyanion [(H2O)(VO)3(AsW9O33)2]9/12– through moderate heating. Conversely, the SbIII-containing derivative gives exclusively the D
3h
polyanion, probably either due to
the extended lone pair of the trigonal SbIII heterogroup
that prevents the formation of the C
2v
arrangement or the lability of the oxo-metalate
bonds that favor chemical exchange. The electrochemical studies of
sandwich-type polyoxometalates revealed that each {VO} group
gives rise to a one-electron transfer process. At last, the redox
properties appear strongly altered in the 0.3–5 pH range, consistent
with proton-coupled electron transfers.
J. Servain, a French scientist [21], proposed a dipole index of a thermal state of waters in the tropical Atlantic. In [8], the index is calculated as a difference between mean water surface temperatures in the northern and southern tropical Atlantic for each month of 1941-2000. The dipole index is assumed to characterize seasonal and interannual changes in the position of the intertropical convergence zone (ITCZ) and thermal equator and potentially is a predictor of the moistening regime in the West African countries. For Cote de Voire, based on the multiyear data on monthly precipitation, five equiprobable gradations were determined. The intercomparison of gradations of the dipole index of the tropical Atlantic and seasonal precipitation in Cote de Voire made it possible to reveal a number of interrelations that can be used for long-range forecasting of precipitation during a rain season.
Apprendre à innover dans un monde incertainConcevoir les futurs de l'agriculture et de l'alimentation Collection Synthèses Odorat et goût. De la neurobiologie des sens chimiques aux applications Roland Salesse et Rémi Gervais, coordinateurs 2012, 550 p. Comment l'herbe pousse. Développement végétatif, structures clonales et spatiales des graminées Michel Lafarge, Jean-Louis Durand 2011, 184 p. Grands paysages pédologiques de France Marcel Jamagne 2011, 624 p. Production durable de biomasse. La lignocellulose des poacées Denis Pouzet 2011, 216 p. La photosynthèse. Processus physiques, moléculaires et physiologiques 2 e édition Jack Farineau, Jean-François Morot-Gaudry 2011, 412 p.Les chapitres 1, 2, 3, 6, 8 et 9 ont été traduits en français par Anya Cockle.
Version anglaise :Renewing innovation systems in agriculture and food: how to go towards more sustainability?
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.