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Transition Metal Complexes with Sulfur Ligands. XLIV. Ruthenium(II) Complexes with the Sterically Demanding Thioether-thiolate Ligand ?buS4’?2?(= 1,2-Bis(3,5-di(tertiarybutyl)-2-mercaptophenylthio) ethane (2-)) and PPh3, CO, PMe3, NH3, and N2H4 Coligands The coordination properties of the sterically demanding thioether-thiolate ligand ‘buS4’2? (= 1,2-Bis(3,5-di(tertiarybutyl)-2-mercaptophenylthio)ethane (2-)) towards Ruthenium were investigated. [Ru(PPh3)2 (‘buS4’)], 1 , was obtained from [RuCl2(PPh3)3] and ‘buS4’? Li2. One PPh3 ligand in 1 is labile towards substitution and can be exchanged by L ? CO ( 2 ), PMe3 ( 3 ), or NH3 ( 5 ) yielding [Ru(L)(PPh3)(‘buS4’)]. The PMe3 complex [Ru(PMe3)2(‘buS4’)], 4 , is thermically inert as well as 2, 3 , and [Ru(CO)2(‘buS4’)], 6 , which was obtained from [RuCl2(CO)3THF] and ‘buS4’? Li2. Considering the thermical reaction inertness of 6 , its fast reaction with N2H4 yielding [Ru(N2H4) (CO) (‘buS4’)], 7 , is remarkable; the reaction probably takes place via 19e- intermediates. All ‘buS4’ complexes are better soluble in organic solvents than the corresponding [Ru(‘S4’)] parent compounds, their ν(CO)frequencies or 31PNMR shifts, however, are nearly identical, allowing the conclusion that the influence of the t-butyl groups is topological and not electronic. All now complexes were characterized by elemental analyses as well as IR, NMR, and mass spectroscopy. 相似文献
44.
We studied, and performed research for our Ph.D. degrees in the area of gas electron diffraction. Our mentor was Lawrence Brockway. a pioneer in this subject. At that time, research in gas electron diffraction was in its early stages of development. In 1941, the distinguished Peter Debye wrote a theoretical paper concerning gas electron diffraction which challenged ones capability to develop the necessary experimental equipment and to further advance the theoretical developments so as to greatly extend the science of gas electron diffraction. We carried these thoughts in mind when we joined the Naval Research Laboratory, where the opportunity to design and produce excellent equipment was readily available. In the course of pursuing this research area, one of the findings was the existence of non-negativity as a condition for the results of a diffraction experiment for gaseous substances. When we became interested in the field of crystal structure determination, the familiarity with non-negativity which was needed in the study of gases, led to a search for the necessary and sufficient condition for a Fourier series to be non-negative. The search was successful and has played an important part in crystal structure determination. Some early applications to complicated structures are described. 相似文献
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46.
Vera M Leirer Christian Wienbruch Isabella Paul-Jordanov Stephan Kolassa Thomas Elbert Iris T Kolassa 《BMC neuroscience》2010,11(1):113
Background
The hippocampus is a brain region that is particularly affected by age-related morphological changes. It is generally assumed that a loss in hippocampal volume results in functional deficits that contribute to age-related cognitive decline. In a combined cross-sectional behavioural and magnetoencephalography (MEG) study we investigated whether hippocampal-associated neural current flow during a transverse patterning task - which requires learning relational associations between stimuli - correlates with age and whether it is modulated by cognitive competence. 相似文献47.
A short new proof of the fact that all shifted complexes are fixed by reverse lexicographic shifting is given. A notion of
lexicographic shifting, Δlex—an operation that transforms a monomial ideal of S = K[xi: i ∈ ℕ] that is finitely generated in each degree into a squarefree strongly stable ideal—is defined and studied. It is proved
that (in contrast to the reverse lexicographic case) a squarefree strongly stable ideal I ⊂ S is fixed by lexicographic shifting if and only if I is a universal squarefree lexsegment ideal (abbreviated USLI) of S. Moreover, in the case when I is finitely generated and is not a USLI, it is verified that all the ideals in the sequence
} are distinct. The limit ideal
is well defined and is a USLI that depends only on a certain analog of the Hilbert function of I.
Research partially supported by NSF grants DMS 0070571 and DMS 0100141. 相似文献
48.
Teresa?D’AprileEmail author Francesca?De?Marchis Isabella?Ianni 《Calculus of Variations and Partial Differential Equations》2018,57(4):99
We study the existence of at least one conformal metric of prescribed Gaussian curvature on a closed surface \(\Sigma \) admitting conical singularities of orders \(\alpha _i\)’s at points \(p_i\)’s. In particular, we are concerned with the case where the prescribed Gaussian curvature is sign-changing. Such a geometrical problem reduces to solving a singular Liouville equation. By employing a min–max scheme jointly with a finite dimensional reduction method, we deduce new perturbative results providing existence when the quantity \(\chi (\Sigma )+\sum _i \alpha _i\) approaches a positive even integer, where \(\chi (\Sigma )\) is the Euler characteristic of the surface \(\Sigma \). 相似文献
49.
Abstract We have investigated Cu, Zn Superoxide Dismutase (Cu, Zn SOD) metal sites at high pressure using X-ray absorption. XAS (X-ray Absorption Spectroscopy) gives information on local structure and it is particularly suited to metal site investigation. To the best of our knowledge, this is the first time that protein conformational states have been investigated using the high pressure XAS technique. Cu, Zn SOD catalyses the dismutation of toxic oxygen radicals produced in cells; this reaction occurs at the copper metal site. Structural changes around the copper, induced by pressure, can be directly related to protein substates. Their characterisation is thus important in the understanding of protein activity. The high-pressure device was a Paris-Edinburgh large volume cell. Experiments were performed on lyophilised Cu, Zn SOD between 0 and 48 kbar at the copper and zinc K-edges. The two metal local atomic environments have a different behaviour as pressure increases: copper exhibits a more flexible environment; on the contrary, zinc shows small structural modifications. We have identified a state, formed between 3 and 8 kbar, which is stable up to 48 kbar. 相似文献
50.
Chiara Lavarello Sebastiano Barco Martina Bartolucci Isabella Panfoli Emanuele Magi Gino Tripodi Andrea Petretto Giuliana Cangemi 《Molecules (Basel, Switzerland)》2021,26(14)
Liquid-chromatography coupled to high resolution mass spectrometry (LC-HRMS) is currently the method of choice for untargeted metabolomic analysis. The availability of established protocols to achieve a high confidence identification of metabolites is crucial. The aim of this work is to describe the workflow that we have applied to build an Accurate Mass Retention Time (AMRT) database using a commercial metabolite library of standards. LC-HRMS analysis was carried out using a Vanquish Horizon UHPLC system coupled to a Q-Exactive Plus Hybrid Quadrupole-Orbitrap Mass Spectrometer (Thermo Fisher Scientific, Milan, Italy). The fragmentation spectra, obtained with 12 collision energies, were acquired for each metabolite, in both polarities, through flow injection analysis. Several chromatographic conditions were tested to obtain a protocol that yielded stable retention times. The adopted chromatographic protocol included a gradient separation using a reversed phase (Waters Acquity BEH C18) and a HILIC (Waters Acquity BEH Amide) column. An AMRT database of 518 compounds was obtained and tested on real plasma and urine samples analyzed in data-dependent acquisition mode. Our AMRT library allowed a level 1 identification, according to the Metabolomics Standards Initiative, of 132 and 124 metabolites in human pediatric plasma and urine samples, respectively. This library represents a starting point for future metabolomic studies in pediatric settings. 相似文献