CO adsorption on neutral iridium clusters

The adsorption of carbon monoxide on neutral iridium clusters in the size range of n = 3 to 21 atoms is investigated with infrared multiple photon dissociation spectroscopy. For each cluster size only a single v(CO) band is present with frequencies in the range between 1962 cm-1 (n = 8) and 1985 cm-1 (n = 18) which can be attributed to an atop binding geometry. This behaviour is compared to the CO binding geometries on clusters of other group 9 and 10 transition metals as well as to that on extended surfaces. The preference of Ir for atop binding is rationalized by relativistic effects on the electronic structure of the later 5d metals

Capacity building efforts for rabies diagnosis in resource-limited countries in Sub-Saharan Africa: a case report of the central veterinary laboratory in Benin (Parakou)

Rabies has been listed as a priority zoonotic disease in many African countries and the countdown to reach the goal of eliminating dog-mediated human rabies deaths by 2030 means that disease control measures need to be applied fast. In this context, an essential pillar of any national plan to control rabies is the implementation of reliable diagnostic techniques to ensure the success of field surveillance systems. Although many African countries have received international support for the control of rabies-some countries, like Benin, have not received a similar level of support. Indeed, until 2018, Benin was not able to diagnose rabies and rabies diagnosis in animals as well as humans relied solely on observed clinical symptoms. Although the Central Veterinary Laboratory (CVL) of Parakou had the equipment to implement two recommended tests, the lack of specific reagents and skills prevented the implementation of a rabies diagnostic service. Here we present the joint efforts of the national authorities in Benin, intergovernmental agencies, and non-governmental organizations to assess the strengths and weaknesses of the government's rabies control efforts. We have applied the Stepwise Approach toward Rabies Elimination (SARE) analysis, implemented rabies diagnostic capacities at the CVL of Parakou, characterized strains of rabies virus circulating in Benin, and finally integrated an inter-laboratory comparison program

Efficacité des actions de réduction des pertes des réseaux d’AEP : Rapport intermédiaire 2016

L’objectif de la collaboration Irstea-Veolia Environnement-VEDIF est d’étudier l’efficacité des actions de réduction des pertes et plus particulièrement : 1.l’impact du renouvellement des canalisations sur les pertes (axe Renouvellement) ; 2.le lien entre la pression de service et le débit de fuite (axe Pression) ; 3.les apports de la sectorisation dans la lutte contre les pertes (axe Sectorisation). L’année 2016 a concentré les travaux de construction de protocoles de traitement primaire des données de sectorisation et de télérelève fournies par les exploitants. Elle a également permis de lancer les premiers travaux sur la mesure des pertes à l’échelle du secteur et l’impact des interventions réalisées sur les débits de pertes en fonction de la nature des fuites et des caractéristiques du tronçon. Une analyse poussée des débits de nuit de quelques secteurs, sélectionnés en première approche parmi les données d’étude, a conduit à l’élaboration puis à la critique de plusieurs méthodes de modélisation de la part des consommations nocturnes dans le débit total (les volumes de pertes étant déduit directement de cette valeur par soustraction à partir du débit de nuit total)

Towards energy decomposition analysis for open and closed shell f-elements mono aqua complexes

International audienceWe propose an energy decomposition analysis of mono aqua systems of both open and closed shell lanthanide and actinide cations using the CSOV scheme. We compared the values obtained with either large f-in-core or small core quasi relativistic pseudopotentials and computed the unpaired electrons contribution to the polarization energy component. Through a quasi-systematic approach on a number of chosen f-element cations, we quantified the different trends across both series for each contribution. This work is an important preliminary step for the acquisition of reference ab initio data for further parameterization of polarizable force fields for lanthanides and actinides. (Cop) 2013 Elsevier B. V. All rights reserved

Novel Di- and Trinuclear Palladium Complexes Supported by <i>N</i>,<i>N</i>′‑Diphosphanyl NHC Ligands and <i>N</i>,<i>N</i>′‑Diphosphanylimidazolium Palladium, Gold, and Mixed-Metal Copper–Gold Complexes

The reaction of the trinuclear complex [Ag₃(μ₃-<b>PC</b>_<b>NHC</b><b>P</b>,κ<i>P</i>,κ<i>C</i>_NHC,κ<i>P</i>)₂]­(OTf)₃ (<b>Ag3</b>; <b>PC</b>_<b>NHC</b><b>P</b> = <i>N</i>,<i>N</i>′-bis­(di-<i>tert</i>-butylphosphanyl)­imidazol-2-ylidene) with [Pd­(dba)₂] afforded the trinuclear palladium complex [Pd₃(μ₃-<b>PC</b>_<b>NHC</b><b>P</b>,κ<i>P</i>,κ<i>C</i>_NHC,κ<i>P</i>)₂]­(OTf)₂ (<b>Pd3</b>) and the dinuclear palladium­(I) complex [Pd₂(μ₂-<b>PC</b>_<b>NHC</b><b>P</b>,κ<i>P</i>,κ<i>C</i>_NHC,κ<i>P</i>)₂]­(OTf)₂ (<b>Pd2</b>). The assignment of the oxidation state of the metals in the mixed-valence <b>Pd3</b> chain as Pd⁰–Pd^II–Pd⁰ was based on the reactivity of the complex with 2,6-dimethylphenyl isocyanide and density functional theory calculations. Reaction of <b>PC</b>_<b>NHC</b><b>P</b> with [PdMe₂(tmeda)] afforded the palladium­(II) complex [PdMe₂(<b>PC</b>_<b>NHC</b><b>P</b>,κ<i>P</i>,κ<i>C</i>_NHC)] (<b>Pd-Me2</b>), with <b>PC</b>_<b>NHC</b><b>P</b> acting as a bidentate ligand. The reaction of <b>PC</b>_<b>NHC</b><b>P</b> with [Pd­(dba)₂] led to a dinuclear palladium(0) complex [Pd₂(μ₂-<b>PC</b>_<b>NHC</b><b>P</b>,κ<i>P</i>,κ<i>C</i>_NHC,κ<i>P</i>)]­(dba) (<b>Pd2-dba</b>); attempted replacement of the remaining dba by <b>PC</b>_<b>NHC</b><b>P</b> failed. The imidazolium triflate <b>PCHP</b>, precursor to <b>PC</b>_<b>NHC</b><b>P</b>, was reacted with [Pd₂(dba)₃]·CHCl₃ to give the (2 + 2) metalla-mesocyclic cationic palladium(0) complex [Pd₂(μ₂-<b>PCHP</b>,κ<i>P</i>,κ<i>P</i>)₂] (<b>PCHP-Pd2</b>), which resisted further deprotonation of the imidazolium cation. In contrast, <b>PCHP</b> reacted with [AuCl­(tht)] to give [Au₂Cl₂(μ₂-<b>PCHP</b>,κ<i>P</i>,κ<i>P</i>)] (<b>PCHP-Au2</b>), in which one Au–Cl moiety is bound to each P donor. Further reaction of <b>PCHP-Au2</b> with [Au­{N­(SiMe₃)₂}­(PPh₃)] afforded a mixture of the trinuclear [Au₃(μ₃-<b>PC</b>_<b>NHC</b><b>P</b>,κ<i>P</i>,κ<i>C</i>_NHC,κ<i>P</i>)₂]­(OTf)₃ (<b>Au3</b>) and [AuCl­(PPh₃)], while reaction with [CuMes]₅, where Mes = 2,4,6-trimethylphenyl, resulted in a novel, centrosymmetric, heterometallic complex [Au₂Mes₂(Cu₄Cl₄)­(<b>PCHP</b>,κ<i>P</i>,κ<i>P</i>)₂] (<b>PCHP-AuCu</b>) featuring a new <b>PCHP-AuMes</b> metalloligand bridging a Cu···Cu diagonal of a Cu₄Cl₄ cubane via the P and AuMes functionalities

Toward accurate solvation dynamics of lanthanides and actinides in water using polarizable force fields: From gas-phase energetics to hydration free energies

International audienceIn this contribution, we focused on the use of polarizable force fields to model the structural, energetic, and thermodynamical properties of lanthanides and actinides in water. In a first part, we chose the particular case of the Th(IV) cation to demonstrate the capabilities of the AMOEBA polarizable force field to reproduce both reference ab initio gas-phase energetics and experimental data including coordination numbers and radial distribution functions. Using such model, we predicted the first polarizable force field estimate of Th(IV) solvation free energy, which accounts for -1,638 kcal/mol. In addition, we proposed in a second part of this work a full extension of the SIBFA (Sum of Interaction Between Fragments Ab initio computed) polarizable potential to lanthanides (La(III) and Lu(III)) and to actinides (Th(IV)) in water. We demonstrate its capabilities to reproduce all ab initio contributions as extracted from energy decomposition analysis computations, including many-body charge transfer and discussed its applicability to extended molecular dynamics and its parametrization on high-level post-Hartree-Fock data. © 2012 Springer-Verlag

Cyclic(Alkyl)(Amino)Carbene (CAAC)-Supported Zn Alkyls: Synthesis, Structure and Reactivity in Hydrosilylation Catalysis

The reactivity of ZnII dialkyl species ZnMe2 with a cyclic(alkyl)(amino)carbene, 1-[2,6-bis(1-methylethyl)phenyl]-3,3,5,5-tetramethyl-2-pyrrolidinylidene (CAAC, 1), was studied and extended to the preparation of robust CAAC-supported ZnII Lewis acidic organocations. CAAC adduct of ZnMe2 (2), formed from a 1:1 mixture of 1 and ZnMe2, is unstable at room temperature and readily undergoes a CAAC carbene insertion into the Zn−Me bond to produce the ZnX2-type species (CAAC-Me)ZnMe (3), a reactivity further supported by DFT calculations. Despite its limited stability, adduct 2 was cleanly ionized to robust two-coordinate (CAAC)ZnMe+ cation (5+) and derived into (CAAC)ZnC6F5+ (7+), both isolated as B(C6F5)4− salts, showing the ability of CAAC for the stabilization of reactive [ZnMe]+ and [ZnC6F5]+ moieties. Due to the lability of the CAAC−ZnMe2 bond, the formation of bis(CAAC) adduct (CAAC)2ZnMe+ cation (6+) was also observed and the corresponding salt [6][B(C6F5)4] was structurally characterized. As estimated from experimental and calculations data, cations 5+ and 7+ are highly Lewis acidic species and the stronger Lewis acid 7+ effectively mediates alkene, alkyne and CO2 hydrosilylation catalysis. All supporting data hints at Lewis acid type activation–functionalization processes. Despite a lower energy LUMO in 5+ and 7+, their observed reactivity is comparable to those of N-heterocyclic carbene (NHC) analogues, in line with charge-controlled reactions for carbene-stabilized ZnII organocations