Metalated nitriles: cation-controlled cyclizations

Judicious choice of cation allows the selective cyclization of substituted gamma-hydroxynitriles to trans- or cis-decalins and trans- or cis-bicyclo[5.4.0]undecanes. The stereoselectivities are consistent with deprotonations generating two distinctly different metalated nitriles: an internally coordinated nitrile anion with BuLi, and a C-magnesiated nitrile with i-PrMgCl. Employing cations to control the geometry of metalated nitriles permits stereodivergent cyclizations with complete control over the stereochemistry of the quaternary, nitrile-bearing carbon.     

Cover Picture

The cover picture shows linear motor molecules in action on a silicate support. Under the spotlight, tethered threadlike polyether chains (pink) intercepted by electron‐donating naphthalene units (red) doff and don electron‐accepting cyclobis(paraquat‐p‐phenylene) girdles (blue). Their risque actions are revealed by the luminescence of the naphthalene units when the girdles are removed. The temporal sequence (left to right) shows the bare thread donning a girdle and then doffing it under the influence of light. The action is attentively monitored by the luminescence spectra; the intensity increases when the girdle is doffed and is quenched when it is donned. More about this process is reported by Zink, Stoddart, and co‐workers on p. 2447 ff.     

A Chemically and Electrochemically Switchable [2]Catenane Incorporating a Tetrathiafulvalene Unit

A mechanical switch in a [2]catenane , made up of a cyclobis(paraquat-p-phenylene) tetracation interlocked with a macrocyclic polyether containing a redox-active tetrathiafulvalene (TTF) unit and a 1,5-dioxynaphthalene ring system, can be thrown either chemically or electrochemically. The neutral TTF unit resides “inside” the tetracationic cyclophane in the reduced state and “alongside” it in the oxidized species (TTF⁺/ TTF²⁺). Switching between the reduced (I⁴⁺) and oxidized state (I⁵⁺(I⁶⁺)) is accompanied by a dramatic color change.     

Functionalised β-diketonate polynuclear lanthanoid hydroxo clusters: Synthesis,characterisation, and magnetic properties

The controlled hydrolysis of lanthanoid trichloride hexahydrate (Ln = Nd, Eu, Ho) in methanol with the β-diketone ligands dibenzoylmethane and 1,3-bis(4-ethoxyphenyl)propane-1,3-dione yielded tetranuclear and pentanuclear hydroxo clusters for Eu and Ho. In contrast, performing the reaction in the presence of 1,3-bis(4-methoxyphenyl)propane-1,3-dione yielded a mononuclear complex for Nd. The compounds were structurally characterised by means of single crystal X-ray diffraction, showing that the increased bulkiness of the ligand due to the ethoxy functionalities does not affect the capability of the diketonate to stabilize the cluster core. Variable temperature dc susceptibility magnetic measurements were made on the clusters and were indicative of very weak to zero antiferromagnetic, intra-cluster coupling. Variable frequency ac data recorded at low temperatures did not show any evidence for single molecule magnet (SMM) behaviour, unlike the recent reported case of the analogue [Dy₅(OH)₅(Ph₂acac)₁₀], where Ph₂acac⁻ is the dibenzoylmethanide ligand.     

Dynamic modelling and simulation of a hot strip finishing mill

Hot rolling is an essential industrial process in the production of sheet steel, a widely used product in manufacturing and construction. A finishing mill performs a set of operations in a hot strip rolling mill, and is a complex unit including many processes and control loops. Its modelling is a challenging task due to the variety of phenomena that occur within the mill, and variable transport delays. Model validation is also challenging due to a scarcity of measurements. On the other hand, a dynamic model that adequately reflects the numerous interactions between the mill units can be very useful for tasks such as high performance control design or vibration analysis. In this study, a one-dimensional model has been developed and validated against real plant data. The end use of the model is intended to be looper control analysis, but the model is kept sufficiently general so that it can be used or easily extended for other applications.     

Protein-cofactor interactions and EPR parameters for the Q(H) quinone binding site of quinol oxidase. A density functional study

Recent multifrequency EPR studies of the "high-affinity" quinone binding site of quinol oxidase (Q(H) site) have suggested a very asymmetric hydrogen-bonding environment for the semiquinone radical anion state. Single-sided hydrogen bonding to the O1 carbonyl position was one of the proposals, which contrasts with some previous experimental indications. Here density functional calculations of the EPR parameters (g-tensors, 13C, 1H, and 17O hyperfine tensors) for a wide variety of supermolecular model complexes have been used to provide insight into the detailed relations among structure, environment, and EPR parameters of ubisemiquinone radical anions. A single-sided binding model is not able to account for the experimentally observed low g(x) component of the g-tensor or for the observed magnitude of the asymmetry of the 13C carbonyl HFC tensors. Based on the detailed comparison between computation and experiment, a model with two hydrogen bonds to O1 and one hydrogen bond to O4 is suggested for the Q(H) site, but a model with one more hydrogen bond on each side cannot be excluded. Several general conclusions on the interrelations between EPR parameters and hydrogen bond patterns of ubisemiquinones in proteins are provided.