Conductivities of some tetraalkylammonium halides, viz. tetrabutylammonium bromide (Bu4NBr), tetrapentylammonium bromide (Pen4NBr), tetrahexylammonium bromide (Hex4NBr) and tetraheptylammonium bromide (Hep4NBr) were measured at 298.15 K in THF + C6H6 mixtures with 10, 20, 30 and 40 mass% of C6H6. A minimum in the conductance values was observed as concentration increases, which dependent both on the salt and the solvent. The observed molar conductivities were explained by the formation of ion-pairs (M+ + X− ↔ MX, KP) and triple-ions (2 M+ + X− ↔ M2X+; M+ + 2X− ↔ MX2−, KT). A linear relationship between the triple-ion formation constants [log(KT/KP)] and the salt concentrations at the minimum conductivity (log Cmin) was given for all salts in C6H6 + THF mixtures. The formation of triple-ions might be attributed to the ion sizes in solutions in which coulombic interactions and covalent bonding forces act as the main forces between the ions (R4N+ X−). 相似文献
A series of hydrogen‐abstraction barriers of a nonheme iron(IV)–oxo oxidant mimicking the active species of taurine/α‐ketoglutarate dioxygenase (TauD) are rationalized by using a valence‐bond curve‐crossing diagram (see figure). It is shown that the barriers correlate with the strength of the C? H bond. Furthermore, electronic differences explain the differences between nonheme and heme iron(IV)–oxo hydrogen‐abstraction barriers.
It has been found that the photocatalytic activity of TiO2 toward the decomposition of gaseous benzene can be greatly enhanced by loading TiO2 on the surface of SrAl2O4: Eu2+, Dy3+ using sol–gel technology. The prepared photocatalyst was characterized by BET, XRD, and XPS analyses. XRD results reveal
that the peaks of titania in either rutile or anatase form are not detected by XRD in the 2θ region from 20° to 50°. The binding
energy values of Ti 2p of pure TiO2 are 458.90 and 464.60 eV, while for TiO2/SrAl2O4: Eu2+, Dy3+, the binding energy values of Ti 2p are 458.50 and 464.20 eV. The results indicate that the optimum loading of TiO2 is 1 wt% and TiO2/SrAl2O4: Eu2+, Dy3+ (1 wt%) demonstrates 1.4 times the photocatalytic activity of that of pure TiO2, but the underlying mechanism of SrAl2O4: Eu2+, Dy3+ in the photocatalytic reaction remains to be unraveled. 相似文献
The cationic organometallic aqua complexes formed by hydrolysis of [(C6H6)2RuCl2]2 in water, mainly [(C6H6)Ru(H2O)3]2+, intercalate into white sodium hectorite, replacing the sodium cations between the anionic silicate layers. The yellow hectorite
thus obtained reacts in water with molecular hydrogen (50 bar, 100 °C) to give a dark suspension containing a black hectorite
in which large hexagonally shaped ruthenium nanoparticles (20–50 nm) are intercalated between the anionic silicate layers,
the charges of which being balanced by hydronium cations. If the reduction with molecular hydrogen (50 bar, 100 °C) is carried
out in various alcohols, spherical ruthenium nanoparticles of smaller size (3–38 nm depending on the alcohol) are obtained.
In alcohols other than methanol, the reduction also works without H2 under reflux conditions, the alcohol itself being the reducing agent; the ruthenium nanoparticles obtained in this case are
spherical and small (2–9 nm) but tend to aggregate to form clusters of nanoparticles. Whereas the ruthenium nanoparticles
prepared by reduction of the yellow hectorite in refluxing alcohols without hydrogen pressure are almost inactive, the nanoparticles
formed by hydrogen reduction catalyze the hydrogenation of benzene to give cyclohexane under mild conditions (50 °C) with
turnover frequencies up to 6500 catalytic cycles per hour, the best solvent being ethanol.
Dedicated to Professor C. N. R. Rao, pioneer of nanocluster chemistry, on the occasion of his 75th birthday. 相似文献
In the nick(el) of time : Bis(μ‐oxo) dinickel(III) complexes 2 (see scheme), generated in the reaction of 1 with H2O2, are capable of hydroxylating the xylyl linker of the supporting ligand to give 3 . Kinetic studies reveal that hydroxylation proceeds by electrophilic aromatic substitution. The lower reactivity than the corresponding μ‐η2:η2‐peroxo dicopper(II) complexes can be attributed to unfavorable entropy effects.