Transition metal salts of 2-amino-3,5-dihalopyridine - dimers: syntheses,structures and magnetic properties of (3,5-diCAPH)2Cu2Br6 and (3,5-diBAPH)2Cu2X6

Three dimeric copper(II) complexes have been prepared with the general formula bis(2-amino-3,5-dihalopyridinium)hexahalodicuprate cuprate(II): (3,5-diCAPH)₂Cu₂Br₆ (1), (3,5-diBAPH)₂Cu₂Cl₆ (2) and (3,5-diBAPH)₂Cu₂Br₆ (3) [3,5-diCAPH = 2-amino-3,5-dichloropyridinium; 3,5-diBAPH = 2-amino-3,5-dibromopyridinium]. The compounds have been characterized via single crystal X-ray diffraction and temperature dependent magnetic susceptibility measurements. All three compounds crystallize in monoclinic space groups (1, C2/c; 2 and 3, P2₁/c) and exhibit alternating layers of hexahalodicuprate ions and organic cations. The hexahalodicuprate ions exhibit short X?Cu and X?X contacts which link the dimers into a square array. Variable temperature magnetic susceptibility data reveal strong intradimer antiferromagnetic exchange (J = ?153, ?65, ?122 K for 1–3, respectively), but negligible inter-dimer magnetic exchange.     

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.     

Rouse dynamics of colloids bound to polymer networks

We present experimental evidence of a transition in the short-time Brownian motion of colloids from diffusive to subdiffusive, Rouse-like. This transition is seen for particles that are bound, through physical adsorption, to transient polymer networks. The characteristic Rouse scaling of the mean square particle displacement with radical t, found in the experiments, is rationalized using an analytical bead-spring model of a large particle anchored to a set of polymer chains.     

A note on the integrality gap of an ILP formulation for the periodic maintenance problem

We address the integrality gap of the integer linear program introduced by Grigoriev et al. (2006) [3] for the periodic maintenance problem. We prove that the integrality gap of this program is bounded by a constant.     

Toward a computational tool predicting the stereochemical outcome of asymmetric reactions: development of the molecular mechanics-based program ACE and application to asymmetric epoxidation reactions

The development and application of ACE, a program that predicts the stereochemical outcome of asymmetric reactions is presented. As major implementations, ACE includes a genetic algorithm to carry out an efficient global conformational search combined with a conjugate gradient minimization routine for local optimization and a corner flap algorithm to search ring conformations. Further improvements have been made that enable ACE to generate Boltzmann populations of conformations, to investigate highly asynchronous reactions, to compute fluctuating partial atomic charges and solvation energy and to automatically construct reactants and products from libraries of catalysts and substrates. Validation on previously investigated reactions (asymmetric Diels Alder cycloadditions and organocatalyzed aldol reactions) followed by application to a number of alkene epoxidation reactions and a comparative study of DFT-derived and ACE-derived predictions demonstrate the accuracy and usefulness of ACE in the context of asymmetric catalyst design.     

Chromium(III) stars and butterflies: synthesis, structural and magnetic studies of tetrametallic clusters

We report the synthesis, structures and magnetic properties of a series of chromium(III) metal-centered triangle (or "star") clusters, [Cr(4){RC(CH(2)O)(3)}(2)(4,4'-R'(2)-bipy)(3)Cl(6)] [R = Et, R' = H (2); R = HOCH(2), R' = H (3); R = Et, R' = (t)Bu (4)], prepared by two-step solvothermal reactions starting from [CrCl(3)(thf)(3)]. The product of the first stage of this reaction is the salt [Cr(bipy)(2)Cl(2)](2)[Cr(2)Cl(8)(MeCN)(2)] (1). In the absence of the diimine, a different family of tetrametallics is isolated: the butterfly complexes [Cr(4){EtC(CH(2)O)(3)}(2){NH(C(R)NH)(2)}(2)Cl(6)] (R = Me (5), Et (6), Ph (7)] where the chelating N-acetimidoylacetamidine NH(C(R)=NH)(2) ligands are formed in situ via condensation of the nitrile solvents (RCN) under solvothermal conditions. Magnetic measurements show the chromium stars to have an isolated S = 3 ground state, arising from antiferromagnetic coupling between the central and peripheral metal ions, analogous to the well-known Fe(III) stars. Bulk antiferromagnetic ordering is observed at 0.6 K. The butterfly complexes have a singlet ground state, with a low-lying S = 1 first excited state, due to dominant wing-body antiferromagnetic coupling.     

6-Aminopenicillanic acid (6-APA) derivatives equipped with anchoring arms

6-APA derivatives were considered as selective labels for the construction of bifunctional linkers dedicated to the oriented immobilization of proteins on materials. Sulbactam-like compounds (i.e., 6-β-sulfonamido-penam sulfones) and penicillin G—like compounds (i.e., para-substituted 6-β-phenylacetamido-penams) were prepared and tested as irreversible inhibitors of representative β-lactamases and D,D-peptidases, respectively. The activity of the modified antibiotics was preserved despite their substitution with various anchoring arms. The (2-nitro-4,5-dimethoxy)-benzyl esters revealed of particular interest due to their capacity to acylate BlaR-CTD without deprotection.     

Synthesis, characterisation and magnetic study of a cyano-substituted dysprosium double decker single-molecule magnet

Bis(octacyanophthalocyanine)dysprosium(III) (1) has been synthesised, characterised and magnetically studied. By the incorporation of cyano substituents on the phthalocyanine (Pc) rings, a starting point has been created for the chemical modification of double deckers for the purpose of surface self-assembly. The modification of the rings leaves the magnetic properties of the double decker largely unaffected.     

Estimate on the Pathwise Lyapunov Exponent of Linear Stochastic Differential Equations with Constant Coefficients

In this article, we study the problem of estimating the pathwise Lyapunov exponent for linear stochastic systems with multiplicative noise and constant coefficients. We present a Lyapunov type matrix inequality that is closely related to this problem, and show under what conditions we can solve the matrix inequality. From this we can deduce an upper bound for the Lyapunov exponent. In the converse direction, it is shown that a necessary condition for the stochastic system to be pathwise asymptotically stable can be formulated in terms of controllability properties of the matrices involved.     

A Continuous Implementation of a Second-Variation Optimal Control Method for Space Trajectory Problems

The paper describes a continuous second-variation method to solve optimal control problems with terminal constraints where the control is defined on a closed set. The integration of matrix differential equations based on a second-order expansion of a Lagrangian provides linear updates of the control and a locally optimal feedback controller. The process involves a backward and a forward integration stage, which require storing trajectories. A method has been devised to store continuous solutions of ordinary differential equations and compute accurately the continuous expansion of the Lagrangian around a nominal trajectory. Thanks to the continuous approach, the method adapts implicitly the numerical time mesh and provides precise gradient iterates to find an optimal control. The method represents an evolution to the continuous case of discrete second-order techniques of optimal control. The novel method is demonstrated on bang–bang optimal control problems, showing its suitability to identify automatically optimal switching points in the control without insight into the switching structure or a choice of the time mesh. A complex space trajectory problem is tackled to demonstrate the numerical robustness of the method to problems with different time scales.