[H3tren] templated iron fluorides; synthesis, crystal structures and Mössbauer studies

The hydrothermal synthesis, using tris-(2-ethylamino)amine (tren) as a template, and the crystal structures of three new hybrid iron fluorides, (H₃O)₂·[H₃tren]₂·(FeF₆)₂·(FeF₅(H₂O))·2H₂O (I), [H₃tren]₂·(FeF₆)₂·(FeF₂(H₂O)₄)·8H₂O (II) and [H₃tren]₂·(FeF₆)·(F)₃·H₂O (III), are reported. I, II, and III are triclinic (P-1), monoclinic (P2₁/c) and orthorhombic (I222), respectively. The structure of I is built up from isolated FeF₆ and FeF₅(H₂O) distorted octahedra separated by triprotonated [H₃tren]³⁺ cations, disordered H₃O⁺ cations and H₂O molecules. In II, Fe^IIIF₆ and neutral [Fe^IIF₂(H₂O)₄] octahedra form, together with [H₃tren]³⁺ cations, infinite (100) layers separated by extra water molecules. The structure of III consists of isolated and disordered FeF₆ octahedra, fluoride anions F⁻ connected to [H₃tren]³⁺ cations and extra fluoride anions F⁻ disordered with H₂O molecules. All [H₃tren]³⁺ cations have a “spider” type conformation. ⁵⁷Fe Mössbauer characterization shows that +III valence state can only be considered for iron cations in I and III and preliminary Mössbauer results are consistent with the presence of both +II and +III valences for iron cations in II, in agreement with the crystallographic results.     

Synthesis of Functional Polymers by Post‐Polymerization Modification

Post‐polymerization modification is based on the direct polymerization or copolymerization of monomers bearing chemoselective handles that are inert towards the polymerization conditions but can be quantitatively converted in a subsequent step into a broad range of other functional groups. The success of this method is based on the excellent conversions achievable under mild conditions, the excellent functional‐group tolerance, and the orthogonality of the post‐polymerization modification reactions. This Review surveys different classes of reactive polymer precursors bearing chemoselective handles and discusses issues related to the preparation of these reactive polymers by direct polymerization of appropriately functionalized monomers as well as the post‐polymerization modification of these precursors into functional polymers.     

Telomerization: Advances and Applications of a Versatile Reaction

A chameleonic reaction : The transition‐metal‐catalyzed telomerization of 1,3‐dienes with different nucleophiles leads to the synthesis of numerous products which can be applied in the cosmetic and pharmaceutical industry as well as in polymers and flavors. This Review shows the versatility of the telomerization based on recent research and industrial applications.

     

Ant colony optimization with a specialized pheromone trail for the car-sequencing problem

This paper studies the learning process in an ant colony optimization algorithm designed to solve the problem of ordering cars on an assembly line (car-sequencing problem). This problem has been shown to be NP-hard and evokes a great deal of interest among practitioners. Learning in an ant algorithm is achieved by using an artificial pheromone trail, which is a central element of this metaheuristic. Many versions of the algorithm are found in literature, the main distinction among them being the management of the pheromone trail. Nevertheless, few of them seek to perfect learning by modifying the internal structure of the trail. In this paper, a new pheromone trail structure is proposed that is specifically adapted to the type of constraints in the car-sequencing problem. The quality of the results obtained when solving three sets of benchmark problems is superior to that of the best solutions found in literature and shows the efficiency of the specialized trail.     

An axiomatic analysis of concordance–discordance relations

Outranking methods propose an original way to build a preference relation between alternatives evaluated on several attributes that has a definite ordinal flavor. Indeed, most of them appeal the concordance/non-discordance principle that leads to declaring that an alternative is “superior” to another, if the coalition of attributes supporting this proposition is “sufficiently important” (concordance condition) and if there is no attribute that “strongly rejects” it (non-discordance condition). Such a way of comparing alternatives is rather natural. However, it is well known that it may produce binary relations that do not possess any remarkable property of transitivity or completeness. This explains why the axiomatic foundations of outranking methods have not been much investigated, which is often seen as one of their important weaknesses. This paper uses conjoint measurement techniques to obtain an axiomatic characterization of preference relations that can be obtained on the basis of the concordance/non-discordance principle. It emphasizes their main distinctive feature, i.e. their very crude way to distinguish various levels of preference differences on each attribute. We focus on outranking methods, such as ELECTRE I, that produce a reflexive relation, interpreted as an “at least as good as” preference relation. The results in this paper may be seen as an attempt to give such outranking methods a sound axiomatic foundation based on conjoint measurement.     

Hybrid Flow-Shop: a Memetic Algorithm Using Constraint-Based Scheduling for Efficient Search

The paper considers the hybrid flow-shop scheduling problem with multiprocessor tasks. Motivated by the computational complexity of the problem, we propose a memetic algorithm for this problem in the paper. We first describe the implementation details of a genetic algorithm, which is used in the memetic algorithm. We then propose a constraint programming based branch-and-bound algorithm to be employed as the local search engine of the memetic algorithm. Next, we present the new memetic algorithm. We lastly explain the computational experiments carried out to evaluate the performance of three algorithms (genetic algorithm, constraint programming based branch-and-bound algorithm, and memetic algorithm) in terms of both the quality of the solutions produced and the efficiency. These results demonstrate that the memetic algorithm produces better quality solutions and that it is very efficient.     

Effect of the environment on molecular properties: synthesis, structure, and photoluminescence of Cu(I) bis(2,9-dimethyl-1,10-phenanthroline) nanoclusters in eight different supramolecular frameworks

By selection of different charge-balancing anionic frameworks and different host-to-guest ratios, the photosensitizer-dye cation [Cu(dmp)2]+ (dmp = 2,9-dimethyl-1,10-phenanthroline) has been embedded in a series of three-dimensional host structures. It occurs with variable geometry in different states of aggregation, including weakly interacting monomers, isolated dimers, columns, and layers. A large variation in its emission lifetime is correlated with the relative energy level spacings of the guest- and host-framework components. In a fully saturated host framework, the lifetime exceeds values reported for a series of conventional Cu(dmp)2 salts.