Electron Transfer in the Cs⊂{Mn4Fe4} Cubic Switch: A Soluble Molecular Model of the MnFe Prussian-Blue Analogues

A mixed-valence {Mn^II₃Mn^IIIFe^II₂Fe^III₂} cyanide-bridged molecular cube hosting a caesium cation, Cs⊂{Mn₄Fe₄}, was synthesized and structurally characterized by X-ray diffraction. Cyclic-voltammetry measurements show that its electronic state can be switched between five different redox states, which results in a remarkable electrochromic effect. Magnetic measurements on fresh samples point to the occurrence of a spin-state change near room temperature, which could be ascribed to a metal-to-metal electron transfer converting the {Fe^II−CN−Mn^III} pair into a {Fe^III−CN−Mn^II} pair. This feature was only previously observed in the polymeric MnFe Prussian-blue analogues (PBAs). Moreover, this novel switchable molecule proved to be soluble and stable in organic solvents, paving the way for its integration into advanced materials.     

Unexpected reactions associated with the xanthate‐mediated polymerization of N‐vinylpyrrolidone

The monomer N‐vinylpyrrolidone (NVP) undergoes side reactions in the presence of R group functional xanthates and impurities. The fate of the monomer NVP and a selection of six O‐ethyl xanthates during xanthate‐mediated polymerization were studied via NMR spectroscopy. A high number of by‐products were identified. Significant side reactions affecting NVP include the formation of an unsaturated dimer and hydration products in bulk or in solution in C₆D₆. In addition, the xanthate adjacent to a NVP unit was found to undergo elimination at moderate temperature (60–70 °C), resulting in unsaturated species and the formation of new xanthate species. The presence of the chlorinated compound α‐chlorophenyl acetic acid, ethyl ester, a precursor in the synthesis of the xanthate S‐(2‐ethyl phenylacetate) O‐ethyl xanthate, resulted in a dramatic increase in the rate of side reactions such as unsaturated dimer formation and a high ratio of unsaturated chain ends. The conditions for the occurrence of such side reactions are discussed in this article, with relevance to increasing the control over the polymerization kinetics, endgroup functionality, and control over the molar mass distribution. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6575–6593, 2008     

High proton conduction in a chiral ferromagnetic metal-organic quartz-like framework

A complex-as-ligand strategy to get a multifunctional molecular material led to a metal-organic framework with the formula (NH(4))(4)[MnCr(2)(ox)(6)]·4H(2)O. Single-crystal X-ray diffraction revealed that the anionic bimetallic coordination network adopts a chiral three-dimensional quartz-like architecture. It hosts ammonium cations and water molecules in functionalized channels. In addition to ferromagnetic ordering below T(C) = 3.0 K related to the host network, the material exhibits a very high proton conductivity of 1.1 × 10(-3) S cm(-1) at room temperature due to the guest molecules.     

Highly Phosphorescent Crystals of Square‐Planar Platinum Complexes with Chiral Organometallic Linkers: Homochiral versus Heterochiral Arrangements,Induced Circular Dichroism,and TD‐DFT Calculations

A novel class of chiral luminescent square‐planar platinum complexes with a π‐bonded chiral thioquinonoid ligand is described. Remarkably the presence of this chiral organometallic ligand controls the aggregation of this square planar luminophor and imposes a homo‐ or hetero‐chiral arrangement at the supramolecular level, displaying non‐covalent Pt–Pt and π–π interactions. Interestingly these complexes are highly luminescent in the crystalline state and their photophysical properties can be traced to their aggregation in the solid state. A TD‐DFT calculation is obtained to rationalize this unique behavior.     

Polymer-protein conjugates from omega-aldehyde endfunctional poly(N-vinylpyrrolidone) synthesised via xanthate-mediated living radical polymerisation

Aldehyde omega-endfunctional poly(N-vinylpyrrolidone) was synthesised via quantitative conversion of a xanthate endfunctional precursor obtained via RAFT-mediated polymerisation.     

Supercritical fluid chromatography and two-dimensional supercritical fluid chromatography of polar car lubricant additives with neat CO(2) as mobile phase

Car lubricant additives are added to mineral or synthetic base stocks to improve viscosity and resistance to oxidation of the lubricant and to limit wear of engines. Their total amount in the commercial lubricant varies from a few percents to 20-25%. As they belong to various chemical classes and are added to a very complex medium, the base stock, their detailed chromatographic analysis is very difficult and time consuming as it should involve sample treatment and preparative scale separations in order to simplify the sample. The aim of this work is to determine the feasibility of the separation of low molecular weight lubricant additives using various packed columns with pure CO(2) as a mobile phase to enable implementation of flame ionisation detection as universal detector. This is part of a hypernated system including more sophisticated specific detectors, such as AED, FTIR or MS to obtain detailed structural information of compounds. This paper is devoted to the comparison of some stationary phases supposed to provide hydrocarbon group type separation (silica and normal phase) or separations on alkyl-bonded silica in non-aqueous mode of some selected classes of additives in test mixtures or in base stocks. Adsorption chromatography allows partial separation of additives from the base stocks while the direct elution of test additives can only be obtained on reversed phase supports having a very efficient silanol group protection so the interaction of the more polar compounds is much reduced. A two-dimensional scheme of analysis is also described. It combines adsorption chromatography to separate most of the polar additives from the base stock and alkyl-bonded silica for more detailed separation of the additives. However, overlapping between groups of compounds and the lack of resolution between some additives and the base stock should be addressed by the implementing of selective detectors.     

Electron Transfer in the Cs⊂{Mn4Fe4} Cubic Switch: A Soluble Molecular Model of the MnFe Prussian‐Blue Analogues

A mixed‐valence {Mn^II₃Mn^IIIFe^II₂Fe^III₂} cyanide‐bridged molecular cube hosting a caesium cation, Cs?{Mn₄Fe₄}, was synthesized and structurally characterized by X‐ray diffraction. Cyclic‐voltammetry measurements show that its electronic state can be switched between five different redox states, which results in a remarkable electrochromic effect. Magnetic measurements on fresh samples point to the occurrence of a spin‐state change near room temperature, which could be ascribed to a metal‐to‐metal electron transfer converting the {Fe^II?CN?Mn^III} pair into a {Fe^III?CN?Mn^II} pair. This feature was only previously observed in the polymeric MnFe Prussian‐blue analogues (PBAs). Moreover, this novel switchable molecule proved to be soluble and stable in organic solvents, paving the way for its integration into advanced materials.     

Synthesis of Triangular Tripalladium Cations as Noble‐Metal Analogues of the Cyclopropenyl Cation

The first C₃‐symmetric 44‐core‐valence‐electron triangular palladium clusters, [{(SAr′)(PAr₃)Pd}₃]⁺, have been synthesized by activation of the C? S bond of isothioureas. Owing to delocalized metal–metal bonding, these stable complexes are the first noble‐metal analogues of the π‐aromatic cyclopropenyl cation [C₃H₃]⁺, with their all‐metal aromaticity involving d‐type atomic orbitals.