In situ electrochemical SFG/DFG study of CN⁻ and nitrile adsorption at au from 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl) amide ionic liquid([BMP][TFSA]) containing 4-{2-[1-(2-cyanoethyl)-1,2,3,4-tetrahydroquinolin-6-yl]diazenyl} benzonitrile (CTDB) and K[Au(CN)₂

In this paper we report an in situ electrochemical Sum-/Difference Frequency Generation (SFG/DFG) spectroscopy investigation of the adsorption of nitrile and CN? from the ionic liquid 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl) amide ([BMP][TFSA]) containing 4-{2-[1-(2-cyanoethyl)-1,2,3,4-tetrahydroquinolin-6-yl]-diazenyl}benzonitrile (CTDB) at Au electrodes in the absence and in the presence of the Au-electrodeposition process from K[Au(CN)?]. The adsorption of nitrile and its coadsorption with CN? resulting either from the cathodic decomposition of the dye or from ligand release from the Au(I) cyanocomplex yield potential-dependent single or double SFG bands in the range 2,125-2,140 cm?1, exhibiting Stark tuning values of ca. 3 and 1 cm?1 V?1 in the absence and presence of electrodeposition, respectively. The low Stark tuning found during electrodeposition correlates with the cathodic inhibiting effect of CTDB, giving rise to its levelling properties. The essential insensitivity of the other DFG parameters to the electrodeposition process is due to the growth of smooth Au.     

Hypervalent Silicon Compounds by Coordination of Diphosphine–Silanes to Gold

Coordination of ambiphilic diphosphine–silane ligands [o‐(iPr₂P)C₆H₄]₂Si(R)F (R=F, Ph, Me) to AuCl affords pentacoordinate neutral silicon compounds in which the metal atom acts as a Lewis base. X‐ray diffraction analyses, NMR spectroscopy, and DFT calculations substantiate the presence of Au→Si interactions in these complexes, which result in trigonal‐bipyramidal geometries around silicon. The presence of a single electron‐withdrawing fluorine atom is sufficient to observe coordination of the silane as a σ‐acceptor ligand, provided it is positioned trans to gold. The nature of the second substituent at silicon (R=F, Ph, Me) has very little influence on the magnitude of the Au→Si interaction, in marked contrast to N→Si adducts. According to variable‐temperature and 2D EXSY NMR experiments, the apical/equatorial positions around silicon exchange in the slow regime of the NMR timescale. The two forms, with the fluorine atom in trans or cis position to gold, were characterized spectroscopically and the activation barrier for their interconversion was estimated. The bonding and relative stability of the two isomeric structures were assessed by DFT calculations.     

Non-overlapping Domain Decomposition Method for a Nodal Finite Element Method

A new approach is proposed for constructing nonoverlapping domain decomposition procedures for solving a linear system related to a nodal finite element method. It applies to problems involving either positive semi-definite or complex indefinite local matrices. The main feature of the method is to preserve the continuity requirements on the unknowns and the finite element equations at the nodes shared by more than two subdomains and to suitably augment the local matrices. We prove that the corresponding algorithm can be seen as a converging iterative method for solving the finite element system and that it cannot break down. Each iteration is obtained by solving uncoupled local finite element systems posed in each subdomain and, in contrast to a strict domain decomposition method, is completed by solving a linear system whose unknowns are the degrees of freedom attached to the above special nodes.     

Microcalorimetric Studies on the Promoter Function in E. Coli TG1 from P. Maltophilia AT18 Chromosome DNA

In this paper, a promoter-probe plasmid pKK232-8 was used as a vector, which functioned in Escherichia coli TG₁ host. The plasmid DNA fragments from Pseudomonas maltophilia AT18 chromosome DNA active as promoter inEscherichia coli TG₁, the promoter function was studied by means of microcalorimetry, the promoter is about 800 bp DNA, it can promote the chloramphenicol (Cm) gene in plasmid pKK232-8, the Cm resistance level is about 80 μg mL^–1, the promoter activity is high. It implicates that there are probably many promoters in Pseudomonas maltophilia AT18 chromosome. All these information is readily obtained by an LKB 2277-204 heat conduction microcalorimeter. Microcalorimetry is a quantitative, inexpensive, and versatile method for microbiological genetic research. This revised version was published online in August 2006 with corrections to the Cover Date.     

Investigation of the adsorption of 4-cyanopyridine on Au(111) by in situ visible–infrared sum frequency generation

We have investigated the configuration of 4-cyanopyridine on Au(111) electrodes in perchlorate solution by in situ visible–IR sum frequency generation (SFG). Thanks to the use of two IR tunable lasers (the free electron laser CLIO and a table laser based on an optical parametric oscillator) we have obtained SFG spectra of the system in the spectral range of both the aromatic cycle and the CN stretching modes. We present herein the first SFG spectra ever obtained under electrochemical conditions in the 9–12 μm range. Our results show a potential-dependent orientation of the adsorbed 4-cyanopyridine from a configuration where the molecule is adsorbed perpendicular to the electrode via the nitrogen of the pyridine ring at negative potentials, to a flat adsorption configuration at intermediate potentials, and finally a perpendicular orientation again where the molecule is bound through the nitrogen of the cyanide end.     

Towards Understanding the Anticorrosive Mechanism of Novel Surfactant Based on Mentha pulegium Oil as Eco-friendly Bio-source of Mild Steel in Acid Medium:a Combined DFT and Molecular Dynamics Investigation

Today,due to the increasingly stringent European directives concerning the use of molecules with certain toxicities towards the environment or their users,the essential oils,extracts,and molecules derived from plants exhibiting the characteristic of being biodegradable can be considered as a source of green corrosion inhibitors instead of harmful synthetic chemicals.The present work was devoted to testing the essential oil extracted from Mentha pulegium leaves(M1) as a corrosion inhibitor for C-steel in 1mol/L HCl solution using both electrochemical techniques and gravimetric measurements for the evaluation of the inhibition efficiencies at different temperatures.The results obtained showed that the inhibition efficiency increased with an increase in Ml concentration to reach a maximum value of 92.21%.We sought to determine the molecule responsible for this high efficiency,starting with the analysis of oil chemical composition by gas chromatography coupled with mass spectrometry.This analysis revealed that menthol(M2)and isomenthol(M3)were the principal constituents.In order to identify the molecule responsible for the inhibition and explain the protection mechanism involved,quantum chemical calculations and Monte Carlo simulations were used to explain the interaction of menthol,the major constituent of M1 with the Fe-surface.To practically confirm these results,we studied the action of 1mol/L HCl on steel with and without the addition of M2 by both methods(gravimetric and electrochemical study).A very high efficiency was obtained,an efficiency of 94.90% at 10^-3 mol/L,which was retained for a long exposure time,and slightly decreased in function of temperature.Finally,a good correlation between the experimental data,theoretical calculations,and SEM studies was obtained,which denied that the Ml efficiency was only a result of a synergy effect and confirmed the high efficiency of Mentha oil and its main component(menthol)as a strong ecological inhibitor of corrosion.     

Approximation by Multipoles of the Multiple Acoustic Scattering by Small Obstacles in Three Dimensions and Application to the Foldy Theory of Isotropic Scattering

The asymptotic analysis carried out in this paper for the problem of a multiple scattering in three dimensions of a time-harmonic wave by obstacles whose size is small as compared with the wavelength establishes that the effect of the small bodies can be approximated at any order of accuracy by the field radiated by point sources. Among other issues, this asymptotic expansion of the wave furnishes a mathematical justification with optimal error estimates of Foldy’s method that consists in approximating each small obstacle by a point isotropic scatterer. Finally, it is shown how this theory can be further improved by adequately locating the center of phase of the point scatterers and the taking into account of self-interactions. In this way, it is established that the usual Foldy model may lead to an approximation whose asymptotic behavior is the same than that obtained when the multiple scattering effects are completely neglected.     

SFG experiment and ab initio study of the chemisorption of CN on low-index platinum surfaces

A dual analysis is proposed in order to have a better understanding of the adsorption of the cyanide ions on a platinum electrode. The SFG (Sum Frequency Generation) spectroscopy allows the in situ vibrational study and the SFG spectra of the CN⁻ species adsorbed on single crystal Pt electrode allow a systematic study of the low-index platinum surfaces. This experimental work is supported by ab initio calculations using density functional theory and cluster models. For each surface orientation and each geometry, a cluster model of 20-30 Pt atoms has been built in order to interpret the chemisorption of the CN⁻ ions through four kinds of adsorption geometry: on-top or bridge site, bonding via C or N atoms. Geometries have been optimized and adsorption energies, electronic properties and vibrational frequencies have been computed. From the electronic properties, we can propose an analysis of the bonding mechanism for each studied kind of adsorption.The SFG spectra of the CN⁻/Pt(1 1 1) system present an unique resonance owing to the top C adsorption. It is mainly the same for the CN⁻/Pt(1 0 0) system. It is also the case for the SFG spectra of the CN⁻/Pt(1 1 0) system recorded at negative electrochemical voltage; at more positive voltage, a second resonance appears at a lower frequency, owing to the top N adsorption.Experimental and theoretical values of the C-N stretching frequencies are in excellent agreement.