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In 1968 Wolfson et al. published the concept for producing energy inside the body using catalytic electrodes exposed to the body fluid as an electrolyte and utilising naturally occurring fuels such as glucose. Since then, the technology has advanced to enhance the levels of power using enzymes immobilised within three-dimensional bioelectrodes that are nanostructured. Current research in the field of enzymatic fuel cells is directed toward applying electrochemical and nanostructural expertise to increase the energy density, to increase the power density, to increase the operational stability, and to increase the voltage output. Nonetheless, biocompatibility remains the major challenge for increasing the life-time for implanted enzymatic biofuel cells. Here, we discuss the current issues for biocompatibility and suggest directions to enhance the design of biofuel cells so as to increase the life-time of implantation whilst maintaining sufficient performance to provide power for implanted medical devices. [ABSTRACT FROM AUTHOR]

Electroactive organic compounds could bring new chemical opportunities to further improve existing electrochemical energy‐storage technologies as they can be prepared from less‐limited resources and potentially at low environmental footprint. Among the current explored research fields, the anion–ion cell configuration appears poorly investigated although quite promising to promote the fabrication of molecular (metal‐free) rechargeable batteries. Herein, we report the synthesis and the electrochemical behavior of both Mg/Li salts of 2,5‐(dianilino)terephthalate (MgDAnT and Li2DAnT) and cross‐linked polyviologen (c‐PV2+) that can reversibly uptake/extract anions at different working potentials, enabling the assembly of full anionic organic batteries. The reversible anion ingress in MgDAnT is however accompanied by solvent co‐insertion from the electrolyte that provokes an overpotential effect during the first charge. Full anionic batteries pairing Li2DAnT with c‐PV2+ were assembled giving rise to 0.7 V as output voltage with a specific capacity of 50 mAh per gram of Li2DAnT. [ABSTRACT FROM AUTHOR]

The structural characterization of stable complexes of pentavalent uranyl synthesized from the reaction of the complex with the bulky amine-phenolate ligand potassium salt [K.sub.2](salan-[super]t[Bu.sub.2]) or the Schiff base ligand potassium salt [K.sub.2](salophen-[super]t[Bu.sun.2]) in pyridine is described. The presence of a back-bonding interaction in the pentavalent uranyl complexes possibly contributed significantly to the observed solution stability of the [U[O.sub.2](salan-[super]t[Bu.sub.2])(py)K] and [U[O.sub.2](salophen-[super]t[Bu.sub.2])(py)K] complexes with respect to disproportionation and hydrolysis.

The mixed-valent diiron(II, III) complexes of unsymmetrical phenolato ligand exchange are studied by Mossbauer spectroscopy and electrochemical techniques. The drastic effects of aqua ligand exchange and deprotonation on the electronic structure and redox potentials of diiron centers are illustrated.

Research has been conducted on dimanganese(II) complexes with unsymmetrical phenol ligand. The authors report that these complexes can react with hydrogen peroxide in acetonitrile solution.

Research has been conducted on unsymmetrical phenol ligand. The authors report that the reactions of this ligand with Mn(OAc) (sub)2 .4H (sub)2 O carried out in the presence of NaOBz lead to dimanganese(II) complexes.

The problem of partitioning dense matrices into sets of sub-matrices has received increased attention recently and is crucial when considering dense linear algebra and kernels with similar communication patterns on heterogeneous platforms. The problem of load balancing and minimizing communication is traditionally reducible to an optimization problem that involves partitioning a square into rectangles. This problem has been proven to be NP-Complete for an arbitrary number of partitions. In this paper, we present recent approaches that relax the restriction that all partitions be rectangles. The first approach uses an original mathematical technique to find the exact optimal partitioning. Due to the complexity of the technique, it has been developed for a small number of partitions only. However, even at a small scale, the optimal partitions found by this approach are often non-rectangular and sometimes non-intuitive. The second approach is the study of approximate partitioning methods utilizing recursive partitioning algorithms. In particular we use the work on optimal partitioning to improve pre-existing algorithms. In this paper we discuss the different perspectives this approach opens and present two algorithms, SNRPP which is a $\sqrt{\frac{3}{2}}$ approximation, and NRPP which is a $\frac{2}{\sqrt{3}}$ approximation. While sub-optimal, the NRRP approach works for an arbitrary number of partitions. We use the first exact approach to analyse how close to the known optimal solutions the NRRP algorithm is for small numbers of partitions. [ABSTRACT FROM AUTHOR]

Silicon nanoparticles (NPs) serve a wide range of optical, electronic, and biological applications. Chemical grafting of various molecules to Si NPs can help to passivate their reactive surfaces, 'fine-tune' their properties, or even give them further interesting features. In this work, 1H, 13C, and 29Si solid-state NMR spectroscopy has been combined with density functional theory calculations to study the surface chemistry of hydride-terminated and alkyl-functionalized Si NPs. This combination of techniques yields assignments for the observed chemical shifts, including the contributions resulting from different surface planes, and highlights the presence of physisorbed water. Resonances from near-surface 13C nuclei were shown to be substantially broadened due to surface disorder and it is demonstrated that in an ambient environment hydride-terminated Si NPs undergo fast back-bond oxidation, whereas long-chain alkyl-functionalized Si NPs undergo slow oxidation. Furthermore, the combination of NMR spectroscopy and DFT calculations showed that the employed hydrosilylation reaction involves anti-Markovnikov addition of the 1-alkene to the surface of the Si NPs. [ABSTRACT FROM AUTHOR]

The preparation and characterization of a series of complexes of the Yb and Eu cations in the oxidation state II and III with the tetradentate N,O-donor tripodal ligands (tris(2-pyridylmethyl)amine (TPA), BPA− (HBPA=bis(2-pyridylmethyl)(2-hydroxybenzyl)amine), BPPA− (HBPPA=bis(2-pyridylmethyl)(3.5-di- tert-butyl-2-hydroxybenzyl)amine), and MPA2− (H2MPA=(2-pyridylmethyl)bis(3.5-di- tert-butyl-2-hydroxybenzyl)amine) is reported. The X-ray crystal structures of the heteroleptic Ln2+ complexes [Ln(TPA)I2] (Ln=Eu, Yb) and [Yb(BPA)I(CH3CN)]2, of the Ln2+ homoleptic [Ln(TPA)2]I2 (Ln=Sm, Eu, Yb) and [Eu(BPA)2] complexes, and of the Ln3+ [Eu(BPPA)2]OTf and [Yb(MPA)2K(dme)2] (dme=dimethoxyethane) complexes have been determined. Cyclic voltammetry studies carried out on the bis-ligand complexes of Eu3+ and Yb3+ show that the metal center reduction occurs at significantly lower potentials for the BPA− ligand as compared with the TPA ligand. This suggests that the more electron-rich character of the BPA− ligand results in a higher reducing character of the lanthanide complexes of BPA− compared with those of TPA. The important differences in the stability and reactivity of the investigated complexes are probably due to the observed difference in redox potential. Preliminary reactivity studies show that whereas the bis-TPA complexes of Eu2+ and Yb2+ do not show any reactivity with heteroallenes, the [Eu(BPA)2] complex reduces CS2 to afford the first example of a lanthanide trithiocarbonate complex. [ABSTRACT FROM AUTHOR]

Magic-angle spinning dynamic nuclear polarization (MAS-DNP) has been proven to be a powerful technique to enhance the sensitivity of solid-state NMR (SSNMR) in a wide range of systems. Here, we show that DNP can be used to polarize lipids using a lipid-anchored polarizing agent. More specifically, we introduce a C16-functionalized biradical, which allows localization of the polarizing agents in the lipid bilayer and DNP experiments to be performed in the absence of excess cryo-protectant molecules (glycerol, dimethyl sulfoxide, etc.). This constitutes another original example of the matrix-free DNP approach that we recently introduced. [ABSTRACT FROM AUTHOR]

We consider the classical problem of broadcasting a large message at an optimal rate in a large scale distributed network under the multi-port communication model. In this context, we are interested in both building an overlay network and providing an explicit algorithm for scheduling the communications. From an optimization point of view, we aim both at maximizing the throughput (i.e., the rate at which nodes receive the message) and minimizing the degree of the participating nodes, i.e., the number of TCP connections they must handle simultaneously. The main novelties of our approach are the introduction of this degree constraint and the classification of the set of participating nodes into two parts: open nodes that stay in the open-Internet and “guarded” nodes that lie behind firewalls or NATs. Two guarded nodes cannot communicate directly, but rather need to use an open node as a gateway for transmitting a message. In the case without guarded nodes, we prove that it is possible to reach the optimal throughput, at the price of a quasi-optimal (up to a small additive increase) degree of the participating nodes. In presence of guarded nodes, our main contributions are a closed form formula for the optimal cyclic throughput and the proof that the optimal solution may require arbitrarily large degrees. In the acyclic case, we propose an algorithm that reaches the optimal throughput with low degree. Then, we prove a worst case ratio between the optimal acyclic and cyclic throughput and show through simulations that this ratio is on average very close to 1, what makes acyclic solutions efficient both in terms of throughput maximization and degree minimization. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (rGO) is used as a conductive additive for nanosilicon-based lithium battery anodes with the high active-mass loading typically required for industrial applications. In contrast to conventional Si electrodes that use acetylene black (AcB) as an additive, the rGO system shows pronounced improvement of electrochemical performance, irrespective of the cycling conditions. With capacity limitation, the rGO system results in improved coulombic efficiency (99.9%) and longer cycle life than conventional electrodes. Upon cycling without capacity limitation, much higher discharge capacity is maintained (2000 mAh g−1 after 100 cycles for 2.5 mg of Si cm−2). Used in conjunction with the bridging carboxymethyl cellulose binder, the crumpled and resilient rGO allows highly reversible functioning of the electrode in which the Si particles repeatedly inflate and deflate upon alloying and dealloying with lithium. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of our work was to evaluate separately the absorption and regeneration performances of different types of amine(s) based solvents (primary, secondary and tertiary alkanolamines, sterically hindered amines, non-cyclical tetramine and cyclical absorption activators) by carrying out screening tests using small scale apparatus: a gas-liquid contactor for absorption, namely a double-stirred cell, and a regeneration cell. Absorption and regeneration performances of the solvents were compared thanks to calculated absorption and regeneration efficiencies. Concerning the absorption results, the positive effect of an activator, and especially the cyclical di-amine piperazine (PZ), on the absorption performances of the different simple amine solutions was clearly highlighted. The activation of the secondary amine MMEA by PZ gives also higher absorption efficiencies. Regarding the regeneration tests, the better regeneration performances of tertiary and sterically hindered amines (MDEA and AMP) were confirmed. For the amines blends, higher regeneration performances were observed with PZ activated solutions than with PIP activated solutions. These absorption and regeneration results will be taken into account in the solvent selection for future combined absorption-regeneration tests. [Copyright &y& Elsevier]

Abstract: The purpose of this work was to evaluate the absorption-regeneration performances of different types of amine(s) based solvents (primary, secondary and tertiary alkanolamines, sterically hindered amines, non-cyclical tetramine and cyclical absorption activators), previously selected thanks to a methodological study and separate laboratory absorption and regeneration tests. In this work absorption-regeneration experiments were carried out using a newly developed CO2 capture laboratory micro-pilot and applying a high gaseous CO2 content (from 20% to 30%) representative of cement plant flue gases. The different experiments allowed us to compare a large number of solvents (simples and blends) by weighing absorption and regeneration performances measured in our plant. The positive effect of an activator (especially the cyclical di-amine piperazine, from 5 to 10%) on the absorption-regeneration performances of the different solutions (especially on the sterically hindered amine 2-amino-2-methyl-1-propanol and on the secondary amines diethanolamine and methylmonoethanolamine, 30% solutions) was clearly highlighted. The influence of other components present in industrial emissions, especially in cement plant flue gases (mainly O2, SOx, and NOx), on the absorption-regeneration performances of the amine solvents was also studied. [Copyright &y& Elsevier]

In this paper, we consider the problem of assigning a set of clients with demands to a set of servers with capacities and degree constraints. The goal is to find an allocation such that the number of clients assigned to a server is smaller than the server's degree and their overall demand is smaller than the server's capacity, while maximizing the overall throughput. This problem has several natural applications in the context of independent tasks scheduling or virtual machines allocation. We consider both the offline (when clients are known beforehand) and the online (when clients can join and leave the system at any time) versions of the problem. We first show that the degree constraint on the maximal number of clients that a server can handle is realistic in many contexts. Then, our main contribution is to prove that even if it makes the allocation problem more difficult (NP-Complete), a very small additive resource augmentation on the servers degree is enough to find in polynomial time a solution that achieves at least the optimal throughput. After a set of theoretical results on the complexity of the offline and online versions of the problem, we propose several other greedy heuristics to solve the online problem and we compare the performance (in terms of throughput) and the cost (in terms of disconnections and reconnections) of all proposed algorithms through a set of extensive simulation results. [ABSTRACT FROM AUTHOR]

Nickel(II) β-azido-meso-tetraphenylporphyrin was successfully anchored on silicon using a bifunctional linker that bears two terminal alkyne functions by the sequence (i) hydrosilylation of a C=C triple bond of the linker by surface Si-H groups and (ii) 1,3-Huisgen cycloaddition between the alkyne-terminated silicon surface and the azidoporphyrin derivative. [ABSTRACT FROM AUTHOR]

Nickel(ii) β-azido-meso-tetraphenylporphyrin was successfully anchored on silicon using a bifunctional linker that bears two terminal alkyne functions by the sequence (i) hydrosilylation of a CC triple bond of the linker by surface Si–H groups and (ii) 1,3-Huisgen cycloaddition between the alkyne-terminated silicon surface and the azidoporphyrin derivative. [ABSTRACT FROM AUTHOR]

Molecular hydrophobic cavities can be mapped thanks to the detection of magnetization transfer from laser polarized xenon to nearby protons. This so called SPINOE approach is described. The study of the spin dynamics during this experiment and its consequences on the practical implementation are detailed. We show that thanks to the knowledge of the physical properties of the system, it becomes possible to choose the best experimental conditions in order to be able to assign magnetization transfer through two dimensional NMR methods. As an illustration, the first 2D SPIROE-TOCSY experiment is reported. To cite this article: L. Dubois et al., C. R. Physique 5 (2004). [Copyright &y& Elsevier]

The dimanganese(ll,ll) complexes 1a [Mn[sub 2](L)(OAc)[sub 2](CH[sub 3]OH)](CIO[sub 4]) and lb [Mn2(L)(OBz)[sub 2](H[sub 2]O)](CIO[sub 4]), where HL is the unsymmetrical phenol ligand 2-(bis-(2-pyridylmethyl)aminomethyl)-6-((2-pyridylmethyl)(benzyl)aminomet hyl)4-methylphenol, react with hydrogen peroxide in acetonitrile solution. The disproportionation reaction was monitored by electrospray ionization mass spectrometry (ESI-MS) and EPR and UV-visible spectroscopies. Extensive EPR studies have shown that a species (2) exhibiting a 16-line spectrum at g ∼ 2 persists during catalysis. ESI-MS experiments conducted similarly during catalysis associate 2a with a peak at 729 (791 for 2b) corresponding to the formula [Mn[sup III]Mn[sup IV]V(L)(O)[sub 2](OAc)][sup +] ([Mn[sup III]Mn[sup IV](L)(O)[sub 2](OBz)][sup +] for 2b). At the end of the reaction, it is partly replaced by a species (3) possessing a broad unfeatured signal at g ∼ 2. ESI-MS associates 3a with a peak at 713 (775 for 3b) corresponding to the formula [Mn[sup II]Mn[sup III](L)(O)(OAc)][sup +] ([Mn[sup II]Mn[sup III](L)(O)(OBz)][sup +] for 3b). In the presence of H[sub 2, sup 18]O, these two peaks move to 733 and to 715 indicating the presence of two and one oxo ligands, respectively. When H[sub 2, sup 18]O[sub 2] is used, 2a and 3a are labeled showing that the oxo ligands come from H[sub 2]O[sub 2]. Interestingly, when an equimolar mixture of H[sub 2]O[sub 2] and H[sub 2, sup 18]O[sub 2] is used, only unlabeled and doubly labeled 2a/b are formed, showing that its two oxo ligands come from the same H[sub 2]O[sub 2] molecule. All these experiments lead to attribute the formula [Mn[sup III]Mn[sup IV](L)-(O)[sub 2](OAc)][sup +] to 2a and to 3a the formula [Mn[sup II]Mn[sup III](L)(O)(OAc)][sup +]. Freeze-quench/EPR experiments revealed that 2a appears at 500 ms and that another species with a 6-line spectrum is formed transiently at ca. 100 ms. 2a was prepared by reaction of la with reft-butyl hydroperoxide as shown by EPR and UV-visible spectroscopies and ESI-MS experiments, its structure was studied by X-ray absorption experiments which revealed the presence of two or three O atoms at 1.87 Å and three or two N/O atoms at 2.14 Å. In addition one N atom was found at a longer distance (2.3 Å) and one Mn at 2.63 Å. 2a can be one-electron oxidized at E[sub ½] = 0.91 V[sub NHE] (ΔE[sub ½] = 0.08 V) leading to its Mn[sup IV]Mn[sup IV] analogue. The formation of 2a from la was monitored by UV-visible and X-ray absorption spectroscopies. Both concur to show that an intermediate Mn[sup II]Mn[sup III] species, resembling 4a [Mn[sub 2](L)(OAc)[sub 2](H[sub 2]O)](ClO[sub 4])[sub 2], the one-electron-oxidized form of 1a, is formed initially and transforms into 2a. The structures of the active intermediates 2 and 3 are discussed in light of their: spectroscopic properties, and potential mechanisms are considered and discussed in the context of the biological reaction. [ABSTRACT FROM AUTHOR]

Reactions of the unsymmetrical phenol ligand 2-(bis(2-pyridyimethyl)aminomethyl)-6-((2-pyridylmethyl)(benzyl)aminometh yl)-4-methylphenol with Mn(OAc)[sub 2]·4H[sub 2]O or Mn(H[sub 2]O)[sub 6](ClO[sub 4])[sub 2] in the presence of NaOBz affords the dimanganese(II) complexes 1(CH[sub 3]OH), [Mn[sub 2](L)(OAc)[sub 2](CH[sub 3]OH)](ClO[sub 4]), and 2(H[sub 2]O), [Mn[sub 2](L)(OBz)[sub 2](H[sub 2]O)](ClO[sub 4]), respectively. On the other hand, reaction of the ligand with hydrated manganese(III) acetate furnishes the mixedvalent derivative 3(H[sub 2]O), [Mn[sub 2](L)(OAc)[sub 2](H[sub 2]O)](ClO[sub 4])[sub 2]. The three complexes have been characterized by X-ray crystallography. 1(CH[sub 3]OH) crystallizes in the monoclinic system, space group P2[sub 1]/c, with a = 10.9215(6) Å, b = 20.2318(12) Å, c = 19.1354(12) Å, α = 90°, β = 97.5310(10)°, γ = 90°, V = 4191.7 A³, and Z = 4. 2(H[sub 2]O) crystallizes in the monoclinic system, space group P2[sub 1]/n, with a = 10.9215(6) Å, b = 20.2318(12) Å, c = 19.1354(12) Å, α = 90°, β = 97.5310(10)°, γ = 90°, V = 4191.7 ų, and Z = 4.3(H[sub 2]O) crystallizes in the monoclinic system, space group P2[sub 1]/c, with a = 11.144(6) Å, b = 18.737(10) Å, c = 23.949(13) Å, α = 90°, β = 95.910(10)°, γ = 90°, V-4974(5) ų, and Z = 4. Magnetic measurements revealed that the three compounds exhibit very similar magnetic exchange interactions -J = 4.3(3) cm[sup -1]. They were used to establish tentative magnetostructural correlations which show that for the dimanganese(II) complexes -J decreases when the Mn-O[sub phenoxo] distance increases as expected from orbital overlap considerations. For the dimanganese(II,III) complexes, crystallographic results show that the Mn[sup II]-O[sub phenoxo] and Mn[sup III]-O[sub phenoxo] bond lengths are inversely correlated. An... [ABSTRACT FROM AUTHOR]

Examines the properties of the dinuclear manganese complex. Outcome on the reaction of manganese compounds with ethylamines compounds; X-ray crystallography of the binuclear manganese compounds; Electrochemical behavior of the manganese complex.

This article focuses on the book "Afro-Antillean Literature in French," by Roger Toumson. The book is published in two volumes and the author's goal is to establish how, why and when Afro-Antillean literature acceded to a meaningful autonomy. The book is divided into three sections. It starts with a discussion of methodology and a definition of its topic. The second section is an attempt to characterize the white "Creole" literary production of the earlier period and it focuses in particular on the rise of an Antillean regionalism. The third section presents an account of the discursive system of Negritude, highlighting factors that helped bring about the birth and subsequent evolution of a literary ideology based upon a cultural and racial coming to awareness.

Summary: In High Performance Computing, heterogeneity is now the norm with specialized accelerators like GPUs providing efficient computational power. Resulting complexity led to the development of task‐based runtime systems, where complex computations are described as task graphs, and scheduling decisions are made at runtime to perform load balancing between all the resources of the platforms. Developing good scheduling strategies, even at the scale of a single node, and analyzing them both theoretically and in practice are expected to have a very high impact on the performance of current HPC systems. The special case of 2 kinds of resources, typically CPUs and GPUs, is already of great practical interest. The scheduling policy HeteroPrio has been proposed in the context of fast multipole computations (FMM) and has been extended to general task graphs with very promising results. In this paper, we provide a theoretical study of the performance of HeteroPrio, by proving approximation bounds compared to the optimal schedule, both in the case of independent tasks and in the case of general task graphs. Interestingly, our results establish that spoliation (a technique that enables resources to restart uncompleted tasks on another resource) is enough to prove bounded approximation ratios for a list scheduling algorithm on two unrelated resources, which is known to be impossible otherwise. This result holds true both for the independent and dependent tasks graphs. Additionally, we provide an experimental evaluation of HeteroPrio on real task graphs from dense linear algebra computation, which establishes its strong performance in practice. [ABSTRACT FROM AUTHOR]

Tris-copper centers are present at the active site of multicopper oxidases (MCO) which couple the four-electron reduction of molecular oxygen to water with the oxidation of substrates. Modelling these sites with small molecular complexes has thus attracted the interest of many groups in the (bio)inorganic community over the past three decades and still appears a challenge. These enzymes and their model complexes presently enjoy a renewed interest as potential non-precious metal catalyst for the Oxygen Reduction Reaction. Moreover recent work has revealed that tris-copper centers can catalyze methane oxidation. Therefore the elaboration of tris-copper system constitutes an important and timely issue. The aim of the present review is to analyze the various attempts at preparing tris-copper complexes in terms of strategy of ligand design. Of course the challenge to be met is to force three independent binding sites to converge and react in concert. Three main approaches have been developed to anchor these binding sites based on the use of (i) a node either (a) a single atom node (tren-based systems and related), or (b) an hexa -atom node (mesityl-based systems and derivatives), (ii) macrocyclic systems, and (iii) combination of mono- and dinuclear sites. The structures of the different systems will be described and analyzed accordingly. Then the various reactivities exhibited by these systems will be presented so as to evaluate how the ligand design influences the reactivity and to discern promising future directions. [ABSTRACT FROM AUTHOR]

A new series of complexes of Eu2+ and Yb2+ with tripodal aminophenolate ligands are reported by M. Mazzanti and colleagues in their Full Paper on page 15188 ff. Cyclic voltammetry studies show that these ligands can be effectively used to tune the redox properties and reactivity of lanthanide ions possessing weak reducing power. The increased reducing power of Eu2+ in a homoleptic aminophenolate complex allows the reduction of CS2 and affords the first example of a lanthanide trithiocarbonate complex. [ABSTRACT FROM AUTHOR]

Matrix ‐ Free DNP on Lipid Membranes Dynamic nuclear polarization (DNP) has been proven to be a powerful technique to enhance the sensitivity of solid ‐ state NMR. However, until now, there has been limited success in its application to synthetic membrane ‐ type systems. In their Communication on page 4512 ff., G. De Paëpe et al. present an innovative approach based on system ‐ driven radical design in order to insert the polarizing agent inside a lipid bilayer. Combined with matrix ‐ free DNP, this strategy solves additive ‐ induced problems by releasing the need for a DNP ‐ compatible solvent. [ABSTRACT FROM AUTHOR]

Abstract: The presence of highly concentrated dissolved laser-polarized xenon (∼1mol/L, polarization up to 0.2) induces numerous effects on proton and xenon NMR spectra. We show that the proton signal enhancements due to 129Xe–1H cross-relaxation (SPINOE) and overall shifts of the proton resonances due to the average dipolar shift created by the intense xenon magnetization are correlated. Protons behave as very useful sensors of the xenon magnetization. Indeed the xenon resonances exhibit many features such as superimposition of narrow lines on the main resonance due to clustering effects, or such as a polarization-dependent line broadening that is tentatively assigned to the effects of temperature fluctuations that decorrelate some distant dipolar field effects from local interactions, transforming xenon spins from “like” to “unlike” spins. These spectral features make difficult the determination of the average dipolar field by means of the xenon resonance but have interesting consequences on the heteronuclear polarization transfer experiment in Hartmann–Hahn conditions (SPIDER). [Copyright &y& Elsevier]

Implantable devices powered by batteries have been used for sixty years. In recent devices, lithium-based batteries are the most widely used power source. However, lithium batteries have many disadvantages in terms of safety, reliability, and longevity and require regular monitoring and substitution. Implantable glucose biofuel cells (BFCs) are increasingly seen as a potential future technology for replacing lithium-based batteries because they do not require surgical replacement after 8-10 years and have a theoretically unlimited lifetime thanks to the continued recovery of glucose and oxygen present in the human body. This paper shows the fabrication of flexible implantable abiotic cathodes, based on a nitrogen/iron-doped graphene catalyst, for glucose/oxygen biofuel cell application. An ink, based on nitrogen-iron doped graphene as the abiotic catalyst and chitosan as a binder, was prepared and coated on a flexible teflonated gas diffusion layer using doctor blade coating. The characterization of the biocathode shows an open potential circuit corresponding to the potential of the abiotic catalyst and a high oxygen reduction current density of up to 66 μA cm -2 under physiological conditions. Those cathodes remain stable for up to two years with a current density loss of only 25%. The flexible abiotic electrode cytotoxicity was evaluated by cell culture experiments showing living cells' high tolerance on the biocathode surface. This work demonstrates that this abiotic catalyst can be a promising alternative for the development of implantable glucose BFCs due to its stability and its cytocompatibility., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (This journal is © The Royal Society of Chemistry.)

Synthetic iron-sulfur cubanes are models for biological cofactors, which are essential to delineate oxidation states in the more complex enzymatic systems. However, a complete series of [Fe 4 S 4 ] n complexes spanning all redox states accessible by 1-electron transformations of the individual iron atoms ( n = 0-4+) has never been prepared, deterring the methodical comparison of structure and spectroscopic signature. Here, we demonstrate that the use of a bulky arylthiolate ligand promoting the encapsulation of alkali-metal cations in the vicinity of the cubane enables the synthesis of such a series. Characterization by EPR, 57 Fe Mössbauer spectroscopy, UV-visible electronic absorption, variable-temperature X-ray diffraction analysis, and cyclic voltammetry reveals key trends for the geometry of the Fe 4 S 4 core as well as for the Mössbauer isomer shift, which both correlate systematically with oxidation state. Furthermore, we confirm the S = 4 electronic ground state of the most reduced member of the series, [Fe 4 S 4 ] 0 , and provide electrochemical evidence that it is accessible within 0.82 V from the [Fe 4 S 4 ] 2+ state, highlighting its relevance as a mimic of the nitrogenase iron protein cluster.

Organic materials derived from biomass can constitute a viable option as replacements for inorganic materials in lithium-ion battery electrodes owing to their low production costs, recyclability, and structural diversity. Among them, conjugated carbonyls have become the most promising type of organic electrode material as they present high theoretical capacity, fast reaction kinetics, and quasi-infinite structural diversity. In this letter, we report a new perylene-based all-organic redox battery comprising two aromatic conjugated carbonyl electrode materials, the prelithiated tetra-lithium perylene-3,4,9,10-tetracarboxylate (PTCLi6) as negative electrode material and the poly(N-n-hexyl-3,4,9,10-perylene tetracarboxylic)imide (PTCI) as positive electrode material. The resulting battery shows promising long-term cycling stability up to 200 cycles. In view of the enhanced cycling performances, the two organic materials studied herein are proposed as suitable candidates for the development of new all-organic lithium-ion batteries.

Silicon nanoparticles (NPs) serve a wide range of optical, electronic, and biological applications. Chemical grafting of various molecules to Si NPs can help to passivate their reactive surfaces, "fine-tune" their properties, or even give them further interesting features. In this work, (1) H, (13) C, and (29) Si solid-state NMR spectroscopy has been combined with density functional theory calculations to study the surface chemistry of hydride-terminated and alkyl-functionalized Si NPs. This combination of techniques yields assignments for the observed chemical shifts, including the contributions resulting from different surface planes, and highlights the presence of physisorbed water. Resonances from near-surface (13) C nuclei were shown to be substantially broadened due to surface disorder and it is demonstrated that in an ambient environment hydride-terminated Si NPs undergo fast back-bond oxidation, whereas long-chain alkyl-functionalized Si NPs undergo slow oxidation. Furthermore, the combination of NMR spectroscopy and DFT calculations showed that the employed hydrosilylation reaction involves anti-Markovnikov addition of the 1-alkene to the surface of the Si NPs., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This article describes the study of a linear trimer and three polyarylamines PB1-3 containing a 3,4'-biphenyl ferromagnetic coupler. The synthesis of the model compound (trimer) and the polymers has been presented. The formation of radical cations was studied using electrochemical and optical (UV-vis) methods. The chemical oxidation of these compounds leads to the creation of high-spin states, evidenced by pulsed EPR nutation spectroscopy. A quartet spin state is observed for the trimer model compound, and its J exchange coupling constant has been measured experimentally (J/k = 11.8 K) and compared quantitatively to DFT calculations. Most importantly, quartet and quintet spin states have been formed for PB3 and PB2, respectively. These last two doped polymers thus exhibit the highest spin states observed to date for linear polyarylamine compounds.

The preparation and characterization of a series of complexes of the Yb and Eu cations in the oxidation state II and III with the tetradentate N,O-donor tripodal ligands (tris(2-pyridylmethyl)amine (TPA), BPA(-) (HBPA=bis(2-pyridylmethyl)(2-hydroxybenzyl)amine), BPPA(-) (HBPPA=bis(2-pyridylmethyl)(3.5-di-tert-butyl-2-hydroxybenzyl)amine), and MPA(2-) (H2 MPA=(2-pyridylmethyl)bis(3.5-di-tert-butyl-2-hydroxybenzyl)amine) is reported. The X-ray crystal structures of the heteroleptic Ln(2+) complexes [Ln(TPA)I2 ] (Ln=Eu, Yb) and [Yb(BPA)I(CH3 CN)]2 , of the Ln(2+) homoleptic [Ln(TPA)2 ]I2 (Ln=Sm, Eu, Yb) and [Eu(BPA)2 ] complexes, and of the Ln(3+) [Eu(BPPA)2 ]OTf and [Yb(MPA)2 K(dme)2 ] (dme=dimethoxyethane) complexes have been determined. Cyclic voltammetry studies carried out on the bis-ligand complexes of Eu(3+) and Yb(3+) show that the metal center reduction occurs at significantly lower potentials for the BPA(-) ligand as compared with the TPA ligand. This suggests that the more electron-rich character of the BPA(-) ligand results in a higher reducing character of the lanthanide complexes of BPA(-) compared with those of TPA. The important differences in the stability and reactivity of the investigated complexes are probably due to the observed difference in redox potential. Preliminary reactivity studies show that whereas the bis-TPA complexes of Eu(2+) and Yb(2+) do not show any reactivity with heteroallenes, the [Eu(BPA)2 ] complex reduces CS2 to afford the first example of a lanthanide trithiocarbonate complex., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Magic-angle spinning dynamic nuclear polarization (MAS-DNP) has been proven to be a powerful technique to enhance the sensitivity of solid-state NMR (SSNMR) in a wide range of systems. Here, we show that DNP can be used to polarize lipids using a lipid-anchored polarizing agent. More specifically, we introduce a C16-functionalized biradical, which allows localization of the polarizing agents in the lipid bilayer and DNP experiments to be performed in the absence of excess cryo-protectant molecules (glycerol, dimethyl sulfoxide, etc.). This constitutes another original example of the matrix-free DNP approach that we recently introduced., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This report describes the study of a dimer d 2+ and a linear trimer t 3+ of amminium radical cations coupled by 3,4'-biphenyl spin coupling units. The synthesis of the parent diamine and triamine and their optical and electrochemical properties obtained by UV-visible and cyclic voltammetry are presented. The chemical doping of the parent diamine d and triamine t was performed quantitatively to obtain samples containing the corresponding dimer d 2+ and trimer t 3+ in almost pure high-spin states as evidenced by pulsed EPR nutation spectroscopy. The J coupling constants of the corresponding S = 1 and S = 3/2 spin states were measured (J/k = 135 K) and compared quantitatively to DFT calculations.

Polyarylamine containing meta-para-para-aniline units in the main chain and meta-para-aniline units in the pendant chains was synthesized. The polymer can be oxidized to radical cations in chemical or electrochemical ways. The presence of meta-phenylenes in the polymer chemical structure allows for the ferromagnetic coupling of electronic spins, which leads to the formation of high spin states. Detailed pulsed-EPR study indicates that the S = 2 spin state was reached for the best oxidation level. Quantitative magnetization measurements reveal that the doped polymer contains mainly S = 2 spin states and a fraction of S = 3/2 spin states. The efficiency of the oxidation was determined to be 74%. To the best of our knowledge, this polymer is the first example of a linear doped polyarylamine combining such high spin states with high doping efficiency.

Magnetic properties of a doped linear polyarylamine (PA2), whose chain includes alternating para-phenylene and meta-phenylene groups, and of two cyclic and linear model compounds (C2 and D2) were explored by pulsed-EPR nutation spectroscopy, SQUID magnetometry and DFT calculations. Stoichiometrically doped PA2 samples exhibit a pure S = 1 state (exchange coupling constant J = 18 K) with a high spin concentration (0.65) corresponding to 65% of mers bearing holes. Such properties were already observed for doped reticulated polyarylamines but are quite unusual for doped linear polyarylamines. In order to better understand the properties of PA2, model compounds C2 and D2 were also investigated: pure S = 1 spin states could also be obtained, but with higher J (respectively 57 K and 35 K) and, surprisingly, with high but still limited spin concentrations (respectively 0.77 and 0.65).

Nickel(II) beta-azido-meso-tetraphenylporphyrin was successfully anchored on silicon using a bifunctional linker that bears two terminal alkyne functions by the sequence (i) hydrosilylation of a C[triple bond]C triple bond of the linker by surface Si-H groups and (ii) 1,3-Huisgen cycloaddition between the alkyne-terminated silicon surface and the azidoporphyrin derivative.