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841.
Cimadevilla F García ME García-Vivó D Ruiz MA Graiff C Tiripicchio A 《Inorganic chemistry》2012,51(13):7284-7295
The title compound reacted rapidly with CN(t)Bu at room temperature by displacing the BF(4)(-) ligand and incorporating three molecules of isocyanide to yield the electron-precise complex [Mo(2)Cp(2)(μ-PPh(2))(2)(CN(t)Bu)(3)(CO)](BF(4))(2), which was obtained as a mixture of cis and trans isomers. Reaction with several HER(n) molecules (HER(n) = HSPh, HSePh, H(2)PCy) took place with formal elimination of HBF(4) and spontaneous carbonylation to give the electron-precise cations [Mo(2)Cp(2)(μ-ER(n))(μ-PPh(2))(2)(CO)(2)](+). Reactions with several bidentate ligands (L(2)H) having acidic E-H bonds (2-hydroxypyridine, 2-mercaptopyridine, cathecol, 2-aminophenol, and 2-aminothiophenol) proceeded analogously with deprotonation of these bonds with the preference E = S > O > N. The N,O-donor ligands yielded 32-electron chelate derivatives of the type [Mo(2)Cp(2)(O,N-L(2))(μ-PPh(2))(2)(CO)]BF(4) (L(2) = OC(5)H(4)N, OC(6)H(4)NH(2)), whereas the S,N-donors yielded 34-electron, S-bridged complexes [Mo(2)Cp(2)(μ-S:S,N-L(2))(μ-PPh(2))(2)(CO)]BF(4) [L(2) = SC(5)H(4)N (Mo-Mo = 2.8895(8) ?), SC(6)H(4)NH(2)]. However, reaction with catechol gave a monodentate derivative [Mo(2)Cp(2)(O-OC(6)H(4)OH)(μ-PPh(2))(2)(CO)]BF(4). In contrast, reactions of the title complex with several carboxylic acids and related species (acetic, benzoic, and thioacetic acids, acetamide, thioacetamide, and sodium diethyldithiocarbamate) were insensitive to the nature of the donor atoms and gave in all cases 32-electron chelate derivatives of type [Mo(2)Cp(2)(κ(2)-L(2))(μ-PPh(2))(2)(CO)]BF(4). All of the above cations having Mo-bound OH, NH, or NH(2) groups were easily deprotonated upon reaction with 1,8-diazabicycloundec-7-ene (DBU) or other bases to give neutral complexes which exhibited different coordination motifs depending on the donor atoms, including chelate complexes of the type [Mo(2)Cp(2)(κ(2)-L(2)')(μ-PPh(2))(2)(CO)] (L(2)' = OC(6)H(4)O, OC(6)H(4)NH), the bridged complexes [Mo(2)Cp(2)(μ-S,N:S,N-SC(6)H(4)NH)(μ-PPh(2))(2)] and [Mo(2)Cp(2){μ-S,N-N(S)CMe}(μ-PPh(2))(2)], and the terminal acetylimido complex [Mo(2)Cp(2){N-N(O)CMe}(μ-PPh(2))(2)(CO)]. 相似文献
842.
The phosphinidene complex [Mo(2)Cp(μ-κ(1):κ(1),η(5)-PC(5)H(4))(CO)(2)(η(6)-HMes*)] reacts with CO to give the diphosphanediyl derivative [Mo(2){μ-κ(1),η(5):κ(1),η(5)-(C(5)H(4))PP(C(5)H(4))}(η(6)-HMes*)(2)]. The latter compound features unreactive lone electron pairs at phosphorus, which instead contribute to the electronic communication between metal centers via a weak π(PP)-bonding interaction. As a result, this complex displays metal-centered acid-base and redox behavior. 相似文献
843.
The application of symmetry and mathematical group theory is a powerful tool for investigating the vibrations of molecules.
In this paper, we present an overview of the methods utilized. First we briefly discuss the quantum mechanical nature of vibrations
and the experimental methods used. We then present the principal concepts for applying group theory to molecules. The symmetry
operations which are used to comprise groups are described and then used to determine the point groups of molecules. The properties
of character tables are presented and the method for obtaining a reducible representation for all the motions of a molecule
is detailed. This can then be broken down to obtain the irreducible representation which contains the symmetry species of
the individual vibrations. The determination of symmetry adapted linear combinations is outlined and the basis for spectroscopic
selection rules is presented. The paper concludes by examining how matrix algebra along with symmetry concepts simplifies
calculations with molecular force constants. 相似文献
844.
Fulbright RK Kingsley PB Guo X Hoffmann C Kahana E Chapman JC Prohovnik I 《Magnetic resonance imaging》2006,24(9):1121-1129
The E200K mutation on chromosome 20 can cause familial Creutzfeldt-Jakob disease (CJD). Patients with this mutation are clinically similar to those with sporadic CJD, but their imaging features are not well documented. We report here the quantitative and qualitative evaluation of the magnetic resonance (MR) imaging characteristics of this unique group of patients using three-dimensional spoiled gradient recalled (SPGR) echo images, diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) measurements, MR spectroscopy and a fluid-attenuated inversion recovery (FLAIR) sequence. The SPGR and ADC data were analyzed with SPM99. ANCOVA and regression models were used for a region-of-interest (ROI) analysis of ADC and metabolic ratios. CJD patients had a decreased fraction of gray matter and an increased fraction of cerebrospinal fluid (P=.001) in the cortex and cerebellum and increased ADC values in the cortex (P<.001). Focal decreases of ADC were found in the putamen via ROI analysis (548+/-83 vs. 709+/-9 microm(2)/s, P=.02). N-acetyl aspartate (NAA) was generally reduced, with the NAA/Cho ratio lowest in the cingulate gyrus. Qualitative assessment revealed hyperintensities on FLAIR, DWI or both in the putamen (three out of four patients), caudate (three out of four patients) and thalamus. These results provide a framework for future study of patients with genetically defined familial CJD. 相似文献
845.
Barrena E de Oteyza DG Sellner S Dosch H Ossó JO Struth B 《Physical review letters》2006,97(7):076102
We report the self-organization of organic nanodots with high crystallinity during the growth of organic heterostructures of Di-indenoperylene (DIP) onto copper-hexadecafluorophthalocyanine (F16CuPc), donor and acceptor molecules, respectively. The process is related to the Stranski-Krastanov growth mode, which is accompanied by a novel type of structural reconstruction of the underlying organic film. This reconstruction affects three monolayers adjacent to the organic interface. In spite of the close resemblance to the formation of semiconductor nanostructures for inorganic heteroepitaxy, the present results conclusively demonstrate a distinctly different growth mechanism for organic heteroepitaxy whose understanding demands further theoretical studies. 相似文献
846.
Rebollar E Bounos G Oujja M Georgiou S Castillejo M 《The journal of physical chemistry. B》2006,110(33):16452-16458
This work investigates the effect of polymer molecular weight (M(W)) on the surface morphology of poly(methyl methacrylate) (PMMA) and polystyrene (PS) films doped with iodonaphthalene (NapI) and iodophenanthrene (PhenI) following irradiation in air at 248 nm. In agreement with previous studies, irradiation of PMMA at 248 nm results in surface swelling and bubble formation within the irradiated bulk. Most importantly, the size of bubbles varies sensitively for the different M(W) values, with larger bubbles being formed for the low M(W) systems. Nevertheless, the maximum swelling attains higher values for the high M(W) values (when compared at the corresponding ablation threshold of the systems). Real-time monitoring of transmission of a probing beam shows that morphological changes last longer in the low M(W) polymer. Melting, consistent with a thermal mechanism, occurs, and enough evidence is gathered to provide direct support for the bulk photothermal model, according to which ejection requires that a critical number of bonds is broken. In particular, the observed different morphological effects can be ascribed to the interplay of two factors, namely, of the much more efficient decomposition of the low M(W) polymer to gaseous products and of the dependence of the mechanical polymer properties on M(W). For PS at 308 nm, the changes parallel the ones for PMMA at 248 nm. In contrast, at the strongly absorbed 248 nm, the morphological processes in PS show a less dramatic dependence on M(W). In all, these results are of direct importance for the optimization of laser processing schemes and applications (e.g., tissue processing, laser deposition, laser restoration, etc.). 相似文献
847.
de Oteyza DG Barrena E Sellner S Ossó JO Dosch H 《The journal of physical chemistry. B》2006,110(33):16618-16623
We present an experimental study on the first stages of the thin film growth of the organic molecule F(16)CuPc (hexadecafluoro-copper-phthalocyanines) on SiO(2). By means of in situ X-ray reflectivity, in situ grazing incidence X-ray diffraction (GIXD), and ex situ atomic force microscopy (AFM), we provide a detailed picture of the film growth mode and its structural evolution at the nanometer scale. We discovered the formation of a low-density layer of molecular aggregates with heights between 5 and 10 A at the interface with the SiO(2) and show that, on top of this interfacial layer, the nucleation and two-dimensional growth of elongated islands of upright standing molecules take place. Structural changes are observed, pointing to significant relaxations of the lattice parameters within the first layers of standing molecules. 相似文献
848.
Sánchez L Martín N González-Cantalapiedra E Echavarren AM Aminur Rahman GM Guldi DM 《Organic letters》2006,8(12):2451-2454
Light-harvesting C(60)-based dyads endowed with a truxene fluorophore unit have been synthesized. Their photophysical studies in solution reveal a singlet-singlet energy transfer deactivation mechanism that confirms the actuation of the latter as an efficient molecular panel for light absorption and energy transduction. Those processes strongly depend on the nature of the linker connecting both chromophores, such as C(60) and truxene, owing to the overlapping degree between their respective orbitals. [structure: see text] 相似文献
849.
[reaction: see text] A more sustainable protocol leading to 2-alkyl- or 2-aryl-substituted benzo[b]furans is reported, involving a copper-TMEDA complex which catalyzes the transformation of readily available ketone derivatives into the corresponding benzofurans in good to excellent yields. The reaction is accomplished using water as the solvent without organic cosolvents, and one example of catalyst reutilization is also presented. 相似文献
850.