Photolytic and Reductive Activations of 2-Arsaethynolate in a Uranium–Triamidoamine Complex: Decarbonylative Arsenic-Group Transfer Reactions and Trapping of a Highly Bent and Reduced Form

Little is known about the chemistry of the 2-arsaethynolate anion, but to date it has exclusively undergone fragmentation reactions when reduced. Herein, we report the synthesis of [U(Tren^TIPS)(OCAs)] ( 2 , Tren^TIPS=N(CH₂CH₂NSiiPr₃)₃), which is the first isolable actinide-2-arsaethynolate linkage. UV-photolysis of 2 results in decarbonylation, but the putative [U(Tren^TIPS)(As)] product was not isolated and instead only [{U(Tren^TIPS)}₂(μ-η²:η²-As₂H₂)] ( 3 ) was formed. In contrast, reduction of 2 with [U(Tren^TIPS)] gave the mixed-valence arsenido [{U(Tren^TIPS)}₂(μ-As)] ( 4 ) in very low yield. Complex 4 is unstable which precluded full characterisation, but these photolytic and reductive reactions testify to the tendency of 2-arsaethynolate to fragment with CO release and As transfer. However, addition of 2 to an electride mixture of potassium-graphite and 2,2,2-cryptand gives [{U(Tren^TIPS)}₂{μ-η²(OAs):η²(CAs)-OCAs}][K(2,2,2-cryptand)] ( 5 ). The coordination mode of the trapped 2-arsaethynolate in 5 is unique, and derives from a new highly reduced and bent form of this ligand with the most acute O-C-As angle in any complex to date (O-C-As ≈128°). The trapping rather than fragmentation of this highly reduced O-C-As unit is unprecedented, and quantum chemical calculations reveal that reduction confers donor–acceptor character to the O-C-As unit.     

Determination of ephedrine and related compounds in pharmaceutical preparations by ion chromatography with direct conductivity detection

An ion chromatographic method with conductivity detection for the simultaneous determination of ephedrine, pseudoephedrine and norephedrine was developed. A mixture of 2.0 mmol/L HNO3 and 2% (v/v) acetonitrile was used as eluent. The three ephedrine-like compounds were separated and determined within 20 min. The linear ranges were 0.08-50 microg/mL for ephedrine, 0.08-40 microg/mL for pseudoephedrine and 0.06-40 microg/mL for norephedrine. The detection limits were 0.03 microg/mL for ephedrine and pseudoephedrine, and 0.02 microg/mL for norephedrine. The method has been applied successfully to the determination of these sympathomimetics in pharmaceutical preparations and in Ephedra herbs.     

Ultrasonic polar scans: numerical simulation on generally anisotropic media

Ultrasonic polar scans are based on the recording of the reflected or transmitted amplitude of sound, impinging a fiber reinforced composite from every possible angle of incidence. The mechanical anisotropy of such materials makes the reflection coefficient direction dependent, whence an ultrasonic polar scan forms a fingerprint of the investigated material. Such scans have already proved to be very valuable in the characterization of composites. Simulations have been performed for single layered and multi-layered systems, for pulsed and harmonic waves. Fiber reinforced composites are mostly orthotropic. The current report presents simulations not only on orthotropic materials but on materials of any kind of anisotropy. These extended numerical simulations are not only valuable in the characterization of highly sophisticated composites, but may also be used to characterize thin slices of crystals and even layered crystals.     

An efficient quasi-Newton method for two-dimensional steady free surface flow

Steady free surface flows are of interest in the fields of marine and hydraulic engineering. Fitting methods are generally used to represent the free surface position with a deforming grid. Existing fitting methods tend to use time-stepping schemes, which is inefficient for steady flows. There also exists a steady iterative method, but that one needs to be implemented with a dedicated solver. Therefore a new method is proposed to efficiently simulate two-dimensional (2D) steady free surface flows, suitable for use in conjunction with black-box flow solvers. The free surface position is calculated with a quasi-Newton method, where the approximate Jacobian is constructed in a novel way by combining data from past iterations with an analytical model based on a perturbation analysis of a potential flow. The method is tested on two 2D cases: the flow over a bottom topography and the flow over a hydrofoil. For all simulations the new method converges exponentially and in few iterations. Furthermore, convergence is independent of the free surface mesh size for all tests.     

Description of the fluctuating colloid-polymer interface

To describe the full spectrum of surface fluctuations of the interface between phase-separated colloid-polymer mixtures from low scattering vector q (classical capillary wave theory) to high q (bulklike fluctuations), one must take account of the interface's bending rigidity. We find that the bending rigidity is negative and that on approach to the critical point it vanishes proportionally to the interfacial tension. Both features are in agreement with Monte Carlo simulations.     

Development of an integrated informatics toolbox: HT kinetic and virtual screening

We discuss thoroughly aspects and issues for the development of a bespoke, but generic, electronic infrastructure designed to cope with the dynamic in high-throughput experimentation and knowledge management, is applicable to large or contract research organizations. We present the first generation of an informatics platform developed for TOPCOMBI, a research project funded by the European Commission for Nanotechnology and Nanoscience. It is composed by an infrastructure and a collection of modules dealing with laboratory analytics, robotics, data handling and analytics, optimization, in-database processing and visualization, which are developed collegially by the partners of the Consortium. This best-of-breed informatics system enables the capture and the re-usage of processes and methodologies, i.e. process and data flows, using the workflow paradigm. Complex workflows designed by power users can be eventually used by either other domain experts or by novices through a web portal. Workflows can also be run interactively to allow visual analytics for instance, or automatically. We present two case studies dealing with the kinetic study of glycerol catalytic oxidation using parallel equipments, and a novel, fully integrated QSAR applied in heterogeneous catalysis, respectively.     

Adsorption properties of the penicillin derivative DTPA on gold substrates.

Despite the large number of articles and patents dealing with penicillin and other beta-lactam antibiotics, there have been no reports about the self-assembly of such substances as monolayers on gold surfaces. The main reason stems from the high reactivity of the beta-lactam ring, which hinders the development of molecules possessing this entity together with a metal-anchoring function. Herein, we present the synthesis of a novel molecule, 6-[(R,S)-5-(1,2-dithiolan-3-yl)pentanoyl-amino]-penicillanic acid, which combines the beta-lactam ring and a metal-anchoring group. Using spectroscopic tools, we demonstrate the chemisorption of this compound on gold as self-assembled monolayers without any alteration of the penicillin pharmacophore and document its reactivity towards a penicillin-binding protein, BlaR-CTD. Our work is a preliminary step towards the development of new biosensors and well-ordered protein arrays, both based on the high affinity of penicillin for penicillin-binding proteins.