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International audience; Flash vacuum thermolysis of N,N′-di-tert-butyl-2,3-dihydro-1H-1,3,2-diazaborole (1) and N,N′-di-tert-butyl-2-cyano-2,3-dihydro-1H-1,3,2-diazaborole (2) has been performed with a progressive increase in temperature and direct analysis of the gaseous flow by UV-photoelectron spectroscopy. The generation of isobutene was confirmed by its PE bands, and the formation of 2,3-dihydro-1H-1,3,2-diazaborole (1′) and 2-cyano-2,3-dihydro-1H-1,3,2-diazaborole (2′) has also been evidenced. These experimental results have been corroborated by TDDFT and OVGF calculations of the ionization energies. The elusive 2,3-dihydro-1H-1,3,2-diazaborole (1′) has been generated by flash vacuum thermolysis of N,N′-di-tert-butyl-2,3-dihydro-1H-1,3,2-diazaborole (1) and studied by UV-photoelectron spectroscopy. The HOMO of 1′ is destabilized by 0.3 eV in comparison with that of pyrrole, whereas the HOMO-1 is significantly stabilized (0.9 eV).

2-(4,8,11-Triscarbamoylmethyl-1,4,8,11-tetraazacyclotetradec-1-yl)acetamide (TETAM) derivatives bearing 1, 2, or 4 silylated arms have been synthesized and grafted to the surface of silica gel and ordered mesoporous silica samples. The resulting organic-inorganic hybrids have been incorporated into carbon paste electrodes and applied to the preconcentration electroanalysis of Pb(II). The attractive recognition properties of these cyclam derivatives functionalized with amide pendent groups toward Pb(II) species and the highly porous structure of the adsorbents can be exploited for the selective and sensitive detection of the target analyte. Various parameters affecting the preconcentration and detection steps have been discussed with respect to the composition and pH of both accumulation and detection media, the nature of the adsorbent (number of silylated groups linking the macrocycle to silica, texture of materials), the accumulation time, and the presence of interfering cations. Under optimal conditions and for 2 min accumulation at open-circuit, the voltammetric response increased linearly with the Pb(II) concentration in a range extending from 2×10−7 to 10−5 M, while a longer accumulation time of 15 min afforded a linear calibration curve between 10−8 and 10−7 M with a detection limit of 2.7×10−9 M which is well below the European regulatory limit of lead in consumption water.

The phases Pb 5 Bi 17 P 5 O 43 and Pb 5 Bi 18 P 4 O 42 are among many recent new oxyphosphates discovered in the ternary system PbO–Bi 2 O 3 –P 2 O 5 . The syntheses of the vanadates and arsenates led to isostructural compounds. Both series display a distorted 3×3×3 superstructure of the tetragonal δ -Bi 2 O 3 polymorph. These types of phases display interesting anion conductivities and measurements were performed from 300 °C to 800 °C on the phosphates, arsenates and vanadates of the two families. The Pb 5 Bi 18 X 4 O 42 phases have higher conductivity values than those of Pb 5 Bi 17 X 5 O 43 . Of the three homologues the vanadates always have the highest conductivities, i.e., at 800 °C: 1.6×10 −2 Siemens·cm −1 for Pb 5 Bi 18 V 4 O 42 and 1.6×10 −3 Siemens·cm −1 for Pb 5 Bi 17 V 5 O 43 . An increase of the volume of the unit cell due to the increasing radius of the pentavalent cations from P, As to V, 0.34 A, 0.47 A, 0.59 A respectively, helps the anion migration through the structure.