Search results for " complex"

Computational Analysis of n→π* Back-Bonding in Metallylene-Isocyanide Complexes R2MCNR′ (M = Si, Ge, Sn; R = tBu, Ph; R′ = Me, tBu, Ph)

2013

A detailed computational investigation of orbital interactions in metal–carbon bonds of metallylene–isocyanide adducts of the type R2MCNR′ (M = Si, Ge, Sn; R, R′ = alkyl, aryl) was performed using density functional theory and different methods based on energy decomposition analysis. Similar analyses have not been carried out before for metal complexes of isocyanides, even though the related carbonyl complexes have been under intense investigations throughout the years. The results of our work reveal that the relative importance of π-type back-bonding interactions in these systems increases in the sequence Sn < Ge ≪ Si, and in contrast to some earlier assumptions, the π-component cannot be …

Unusual B4N2C2 Ligand in a Ruthenium Pseudo-Triple-Decker Sandwich Complex Displaying Three Reversible Electron-Transfer Steps

2008

Open, sesame: The reaction of a heterobicyclic pentalenediyl-like Me2Ph4B4N2C2 dianion with [{(C5Me5)RuCl}4] cleaves the N[BOND]N bond of the ligand and affords a pseudo-triple-decker sandwich complex containing a B4N2C2 middle deck (see picture). This eight-membered ring features nearly linear B-N-B moieties and brings the ruthenium centers unusually close. Cyclic voltammetry indicates efficient electron delocalization over the framework. peerReviewed

Synthesis, X-ray structures and redox behaviour of the group 14 bis-boraamidinates M[PhB(μ-N-t-Bu)2]2 (M = Ge, Sn) and Li2M[PhB(μ-N-t-Bu)2]2 (M = Sn,…

2009

The solid-state structures of the complexes M[PhB(μ-N-t-Bu)2]2 (1a, M= Ge; 1b, M = Sn) were determined to be spirocyclic with two orthogonal boraamidinate (bam) ligands N,N′-chelated to the group 14 centre. Oxidation of 1b with SO2Cl2 afforded the thermally unstable, blue radical cation {Sn[PhB(μ-N-t-Bu)2]2}•+, identified by electron paramagnetic resonance (EPR) spectroscopy supported by density functional theory (DFT) calculations, whereas the germanium analogue 1a was inert towards SO2Cl2. The reaction between Li2[PhB(μ-N-t-Bu)2]2 and SnCl2 or PbI2 in 2:1 molar ratio in diethyl ether produced the novel heterotrimetallic complexes Li2Sn[PhB(μ-N-t-Bu)2]2 (2b) and (Et2O·Li)LiPb[PhB(μ-N-t-Bu)…

Cyclotriveratrylene-Containing Porphyrins

2016

International audience; The C-3-symmetric cyclotriveratrylene (CTV) was covalently bonded via click chemistry to 1, 2, 3, and 6 zinc(II) porphyrin units to various host for C-60. The binding constants, Ka, were measured from the quenching of the porphyrin fluorescence by C-60. These constants vary between 400 and 4000 M-1 and are considered weak. Computer modeling demonstrated that the zinc(II) porphyrin units, [Zn], exhibit a strong tendency to occupy the CTV cavity, hence blocking the access for C-60 to land on this site. Instead, the pincer of the type [Zn]-[Zn] and in one case [Zn]-CTV, were found to be the most probable geometry to promote host-guest associations in these systems.

Badanie właściwości inkluzyjnych p-tert-butylokaliksarenów metodą inwersyjnej chromatografii gazowej

2007

Metodą QSRR scharakteryzowano właściwości inkluzyjne p-tert-butylokaliksarenów o 4, 6 i 8 merach w cyklu oraz ich octanów, wykorzystując do tego celu inwersyjną chromatografię gazową. W badaniach zastosowano przy tym dwa szeregi homologiczne solutów - alkohole alifatyczne oraz benzen i jego homologi. Stwierdzono, że zdolności inkluzyjne w znacznym stopniu zależą od wymiarów luki molekularnej cyklomeru. Zamiana w kaliksarenach grup wodorotlenowych na octanowe nie wywiera natomiast istotnego wpływu na możliwości tworzenia kompleksów typu gość-gospodarz. Wyniki uzyskane metodą QSRR potwierdzono wyznaczonymi wartościami indeksów Kovátsa.

Badanie metodą inwersyjnej chromatografii gazowej wpływu wielkości podstawnika na właściwości inkluzyjne kaliksarenów

2009

Badano wpływ wielkości alifatycznego podstawnika na zdolności inkluzyjne kaliksarenów {kaliks[4]arenu(K4), p-izopropylokaliks[4]arenu (IPK4) i p-tert-butylokaliks[4]arenu (TBK4)}. Oceny wpływu dokonywano za pomocą metody QSRR przy użyciu inwersyjnej chromatografii gazowej. W charakterze solutów użyto szeregu alifatycznych alkoholi, homologów benzenu i homologów pirydyny. Na podstawie indeksów retencji Kovatsa i wykresów zależności właściwej objętości retencji od temperatury wrzenia [Vg=f(Tw)] stwierdzono, że tylko podstawione kaliksareny wykazują właściwości inkluzyjne w stosunku do niższych alkoholi.

Influence of Anion and Cation Structure of Ionic Liquids on Carboxylic Acids Extraction

2019

A recently proposed new mechanism and a model of reactive extraction of carboxylic acids by hydrophobic ionic liquids (ILs) was tested on five systems from published as well as from new equilibrium data on liquid-liquid extraction of butyric and lactic acids (BA and LA) from aqueous solutions. Two phosphonium and one ammonium ILs were used. The model describes experimental data for all systems with a good fit. The mechanism of acid extraction by ILs is very similar for all tested systems. This indicates a more general validity of the developed model. The model allows deeper understanding of regularities in carboxylic acid extraction by hydrophobic ILs. Stability constants of the first acid-…

CIGARETTE SMOKE INDUCES p38 MAPK-INITIATED AND FAS-MEDIATED ERYPTOSIS

2022

Analyser les catastrophes : une approche par les comportements humains

2011

La catastrophe est une forme de crise qui altère profondément un système social soumis à une situation de stress collectif. Ce dernier est confronté à une agression qui surpasse ses capacités d'adaptation induisant une désorganisation sociale et territoriale plus ou moins longue. L'environnement physique, qui influe peu sur les comportements observés en situation normale, contrairement à l'environnement social, impose de nouvelles façons d'agir, de nouveaux modes d'organisation, quelles que soient les échelles considérées. Il s'agit au moment du choc d'assurer sa survie et celle de ses proches (à condition qu'ils ne soient pas trop éloignés spatialement), puis une fois le danger écarté, de …

Repression of Human Papillomavirus Oncogene Expression under Hypoxia Is Mediated by PI3K/mTORC2/AKT Signaling

2019

Oncogenic HPV types are major human carcinogens. Under hypoxia, HPV-positive cancer cells can repress the viral E6/E7 oncogenes and induce a reversible growth arrest. This response could contribute to therapy resistance, immune evasion, and tumor recurrence upon reoxygenation. Here, we uncover evidence that HPV oncogene repression is mediated by hypoxia-induced activation of canonical PI3K/mTORC2/AKT signaling. AKT-dependent downregulation of E6/E7 is only observed under hypoxia and occurs, at least in part, at the transcriptional level. Quantitative proteome analyses identify additional factors as candidates to be involved in AKT-dependent E6/E7 repression and/or hypoxic PI3K/mTORC2/AKT ac…