The temperature dependence of kinetic parameters of triplet phenazine have been determined by analysis of transient response to photoexcitation. The analogue computer used in the analysis is described. 相似文献
Transient nutations of the magnetization of photoelectrons ejected from rubidium and cesium anions are described. The nature of the nutations requires that the time between photoexcitation and appearance of the photoelectron is less than ≈10?7 s. 相似文献
A facile and efficient method for the cleavage of the Ar-Si bond of various aryl trimethyl silanes is described. When adsorbed on montmorillonite KSF (mont KSF), these arylsilanes readily undergo a solvent-free protodesilylation to the corresponding arenes at room temperature in excellent yields. This approach seems to be superior to the traditional mild methods (i.e., desilylation by TFA, TBAF, CsF), in terms of reaction yield, rate, and environmentally benign conditions. Some mechanistic studies using both solution and solid-state magic-angle spinning (SS MAS) (1)H NMR are also presented. 相似文献
We prepared the first sigma-bonded metal complexes of widely utilized organic dyes, perylene tetracarboxylic acid diimides (PDIs). These 1,7-dipalladium PDI complexes were synthesized by C-Br oxidative addition of 1,7-dibromo-N,N'-dicyclohexyl PDI (Br2PDI) to Pd(0) phosphine complexes bearing triphenylphosphine and bischelating 1,2-bis(diphenylphosphino)ethane (dppe). The structures of Pd-PDI complexes were elucidated by single-crystal X-ray analysis. Surprisingly, despite direct attachement of two late transition metal centers, Pd-PDI systems are highly fluorescent (Phi=0.65 and 0.22 for triphenylphosphine and dppe systems, respectively). This is rationalized in terms of weak electronic interactions between the metal centers and PDI pi-system, as revealed by TD-DFT calculations. 相似文献
Abstract The 8-phosphabicyclo[3.2.1]octa-2,6-diene ring system is conveniently synthesized by the addition of chloro(diisopropylamino)phosphenium ion ((Cl)(i-Pr2N)P+,1) to cycloheptatriene. Hydrolysis of the primary adduct yields the corresponding phosphinamide (3). The NMR of 3 is discussed in terms of its structure, and the orientation at P is assigned by a combination of 2-D NMR techniques. The structure of 3 is also probed by model calculations at the MNDO level. 相似文献
A highly active alkyne metathesis catalyst is realized by replacing the amide ligands of a molybdenum(VI) trisamide alkylidyne complex with silanol groups from incompletely condensed POSS (polyhedral oligomeric silsesquioxane) ligands. This catalyst serves as an effective homogeneous mimic of an amorphous silica-supported catalyst. Reactivities of various catalytic mixtures are reported along with an X-ray structure of the aniline-coordinated amidodisiloxymolybdenum(VI) alkylidyne complex. 相似文献
Simplify, simplify, simplify! Pretubulysin (structure without the green substituents), a simplified tubulysin was prepared in the laboratory and also found in a natural myxobacterial source. This biosynthetic precursor of the tubulysins is not as active as tubulysins A and D but is still effective in picomolar concentrations against cancer cell lines.
We report here on an ongoing experimental program initiated at the ISOLDE facility at CERN for the measurement of magnetic
moments of short-lived radionuclides, with the emphasis on magnetic moments of mirror nuclei in far-from-stability regions.
The nuclei are polarized by the tilted foil technique and the resulting 0–180○ βasymmetry is monitored as a function of rf frequency applied in an NMR setup. In order to achieve sufficiently high energy
for transmission through the foils, the experimental setup is mounted on a high voltage platform. The first experiment in
this program was the measurement of the βasymmetry and the NMR resonance for the ground state of 23Mg (I=3/2, T1/2=11.3 s), yielding μ=−0.533(6) nm. Improvements to the experimental setup are presently being designed, to be used in conjunction
with the new developments at ISOLDE for obtaining high charge-state ions from the EBIS (REX-ISOLDE) ion source. This will
help pave the way for measurements of magnetic moments of T=3/2 nuclei in the s–d shell and of T=1/2 f-shell nuclei. The study
of relaxation times and other solid-state phenomena in semiconductors and other materials of interest using this technique
is also contemplated.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献