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1.
Experimental and Theoretical Studies on Arene‐Bridged Metal–Metal‐Bonded Dimolybdenum Complexes 下载免费PDF全文
Dr. Mario Carrasco Natalia Curado Dr. Eleuterio Álvarez Dr. Celia Maya Dr. Riccardo Peloso Prof. Dr. Manuel L. Poveda Dr. Amor Rodríguez Prof. Dr. Eliseo Ruiz Prof. Dr. Santiago Álvarez Prof. Dr. Ernesto Carmona 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(20):6092-6102
The bis(hydride) dimolybdenum complex, [Mo2(H)2{HC(N‐2,6‐iPr2C6H3)2}2(thf)2], 2 , which possesses a quadruply bonded Mo2II core, undergoes light‐induced (365 nm) reductive elimination of H2 and arene coordination in benzene and toluene solutions, with formation of the MoI2 complexes [Mo2{HC(N‐2,6‐iPr2C6H3)2}2(arene)], 3?C6H6 and 3?C6H5Me , respectively. The analogous C6H5OMe, p‐C6H4Me2, C6H5F, and p‐C6H4F2 derivatives have also been prepared by thermal or photochemical methods, which nevertheless employ different Mo2 complex precursors. X‐ray crystallography and solution NMR studies demonstrate that the molecule of the arene bridges the molybdenum atoms of the MoI2 core, coordinating to each in an η2 fashion. In solution, the arene rotates fast on the NMR timescale around the Mo2‐arene axis. For the substituted aromatic hydrocarbons, the NMR data are consistent with the existence of a major rotamer in which the metal atoms are coordinated to the more electron‐rich C?C bonds. 相似文献
2.
Experiments by Gittings, Bandyopadhyay and Durian (Europhys. Lett. 65, 414 (2004)) demonstrate that light possesses a higher probability to propagate in the liquid phase of a foam due to total
reflection. The authors term this observation photon channelling which we investigate in this article theoretically. We first
derive a central relation in the work of Gitting et al. without any free parameters. It links the photon's path-length fraction f in the liquid phase to the liquid fraction ɛ. We then construct two-dimensional Voronoi foams, replace the cell edges by
channels to represent the liquid films and simulate photon paths according to the laws of ray optics using transmission and
reflection coefficients from Fresnel's formulas. In an exact honeycomb foam, the photons show superdiffusive behavior. It
becomes diffusive as soon as disorder is introduced into the foams. The dependence of the diffusion constant on channel width
and refractive index is explained by a one-dimensional random-walk model. It contains a photon channelling state that is crucial
for the understanding of the numerical results. At the end, we shortly comment on the observation that photon channelling
only occurs in a finite range of ɛ. 相似文献
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Lobo AO Corat MA Ramos SC Matsushima JT Granato AE Pacheco-Soares C Corat EJ 《Langmuir : the ACS journal of surfaces and colloids》2010,26(23):18308-18314
A method for the electrodeposition of hydroxyapatite films on superhydrophilic vertically aligned multiwalled carbon nanotubes is presented. The formation of a thin homogeneous film with high crystallinity was observed without any thermal treatment and with bioactivity properties that accelerate the in vitro biomineralization process and osteoblast adhesion. 相似文献
5.
We discuss the role of generalized Heisenberg algebras (GHA) in obtaining an algebraic method to describe physical systems. The method consists in finding the GHA associated to a physical system and the relations between its generators and the physical observables. We choose as an example the infinite square-well potential for which we discuss the representations of the corresponding GHA. We suggest a way of constructing a physical realization of the generators of some GHA and apply it to the square-well potential. An expression for the position operator x in terms of the generators of the algebra is given and we compute its matrix elements. 相似文献
6.
MF Miller IA Franchi AS Sexton CT Pillinger 《Rapid communications in mass spectrometry : RCM》1999,13(13):1211-1217
The use of infrared laser-assisted fluorination to release oxygen from milligram quantities of silicates or other oxide mineral grains is a well-established technique. However, relatively few studies have reported the optimisation of this procedure for oxygen-17 isotope measurements. We describe here details of an analytical system using infrared (10 μm) laser-assisted fluorination, in conjunction with a dual inlet mass spectrometer of high resolving power ( approximately 250) to provide (17)O and (18)O oxygen isotope measurements from 0.5-2 mg of silicates or other oxide mineral grains. Respective precisions (1) of typically 0.08 and 0.04 per thousand are obtained for the complete analytical procedure. Departures from the mass-dependent oxygen isotope fractionation line are quantified by Delta(17)O; our precision (1) of such measurements on individual samples is shown to be +/-0.024 per thousand. In turn, this permits the offset between parallel, mass-dependent fractionation lines to be characterised to substantially greater precision than has been possible hitherto. Application of this system to investigate the (17)O versus (18)O relationship for numerous terrestrial whole-rock and mineral samples, of diverse geological origins and age, indicates that the complete data set may be described by a single, mass-dependent fractionation line of slope 0.5244+/- 0.00038 (standard error). Copyright 1999 John Wiley & Sons, Ltd. 相似文献
7.
CM Silva MF Duarte ML Mira MH Florêncio K Versluis AJ Heck 《Rapid communications in mass spectrometry : RCM》1999,13(12):1098-1103
Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
8.
Based on the behavior of living beings, which react mostly to external stimuli, we introduce a neural-network model that uses external patterns as a fundamental tool for the process of recognition. In this proposal, external stimuli appear as an additional field, and basins of attraction, representing memories, arise in accordance with this new field. This is in contrast to the more-common attractor neural networks, where memories are attractors inside well-defined basins of attraction. We show that this procedure considerably increases the storage capabilities of the neural network; this property is illustrated by the standard Hopfield model, which reveals that the recognition capacity of our model may be enlarged, typically, by a factor . The primary challenge here consists in calibrating the influence of the external stimulus, in order to attenuate the noise generated by memories that are not correlated with the external pattern. The system is analyzed primarily through numerical simulations. However, since there is the possibility of performing analytical calculations for the Hopfield model, the agreement between these two approaches can be tested—matching results are indicated in some cases. We also show that the present proposal exhibits a crucial attribute of living beings, which concerns their ability to react promptly to changes in the external environment. Additionally, we illustrate that this new approach may significantly enlarge the recognition capacity of neural networks in various situations; with correlated and non-correlated memories, as well as diluted, symmetric, or asymmetric interactions (synapses). This demonstrates that it can be implemented easily on a wide diversity of models. 相似文献
9.
Marina Pérez-Jiménez Dr. Natalia Curado Dr. Celia Maya Dr. Jesús Campos Prof. Dr. Eliseo Ruiz Prof. Dr. Santiago Álvarez Prof. Ernesto Carmona 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(21):6569-6578
This contribution focuses on complex [Mo2(H)2(μ-AdDipp2)2] ( 1 ) and tetrahydrofuran and pyridine adducts [Mo2(H)2(μ-AdDipp2)2(L)2] ( 1⋅thf and 1⋅py ), which contain a trans-(H)Mo≣Mo(H) core (AdDipp2=HC(NDipp2)2; Dipp=2,6-iPr2C6H3). Computational studies provide insights into the coordination and electronic characteristics of the central trans-Mo2H2 unit of 1 , with four-coordinate, fourteen-electron Mo atoms and ϵ-agostic interactions with Dipp methyl groups. Small size C- and N-donors give rise to related complexes 1⋅L but only one molecule of P-donors, for example, PMe3, can bind to 1 , causing one of the hydrides to form a three-centered, two-electron (3c-2e) Mo-H→Mo bond ( 2⋅PMe3 ). A DFT analysis of the terminal and bridging hydride coordination to the Mo≣Mo bond is also reported, along with reactivity studies of the Mo−H bonds of these complexes. Reactions investigated include oxidation of 1⋅thf by silver triflimidate, AgNTf2, to afford a monohydride [Mo2(μ-H)(μ-NTf2)(μ-AdDipp2)2] ( 4 ), with an O,O’-bridging triflimidate ligand. 相似文献
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