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International audience; A series of new glyconanoparticles (GNPs) was obtained by self-assembly by direct nanoprecipitation of a mixture of two carbohydrate amphiphilic copolymers consisting of polystyrene-block-β-cyclodextrin and polystyrene-block-maltoheptaose with different mass ratios, respectively 0–100, 10–90, 50–50 and 0–100%. Characterizations for all these GNPs were achieved using dynamic light scattering, scanning and transmission electron microscopy techniques, highlighting their spherical morphology and their nanometric size (diameter range 20–40 nm). In addition, by using the inclusion properties of cyclodextrin, these glyconanoparticles were successfully post-functionalized using a water-soluble redox compound, such as anthraquinone sulfonate (AQS) and characterized by cyclic voltammetry. The resulting glyconanoparticles exhibit the classical electroactivity of free AQS in solution. The amount of AQS immobilized by host–guest interactions is proportional to the percentage of polystyrene-block-β-cyclodextrin entering into the composition of GNPs. The modulation of the surface density of the β-cyclodextrin at the shell of the GNPs may constitute an attractive way for the elaboration of different electroactive GNPs and even GNPs modified by biotinylated proteins

The state-of-the-art procedure for investigating homogenous and heterogeneous electrocatalysts is cyclic voltammetry (CV). However, this technique usually requires an inactive electrode material. One common problem arising e. g. in studying the oxygen reduction reaction (ORR) is the significant background contribution to the overall ORR current provided by many carbon-based and metal-based electrode materials. Furthermore, rotating ring-disc electrodes (RRDEs) made of common materials like glassy carbon/platinum (GC/Pt) can be affected by overlapping reduction potentials on the disc. Interference from overlapping reactions on the ring might also occur, particularly in connection with oxygen reduction and hydrogen peroxide oxidation in ORR studies. We present herein a novel subtraction method which allows a semi-quantitative description of homogeneous electrocatalysts and helps to overcome the overlapping problems described above using anthraquinone-2-sulfonate (AQS) as a “case study material” for the ORR. Fonds zur Förderung der Wissenschaftlichen Forschung Z222-N19 Version of record

The aerobic organocatalytic oxidation of alcohols was achieved by using water‐soluble sodium anthraquinone sulfonate. Under visible‐light activation, this catalyst mediated the aerobic oxidation of alcohols to aldehydes and ketones. The photo‐oxyfunctionalization of alkanes was also possible under these conditions.

The state-of-the-art procedure for investigating homogenous and heterogeneous electrocatalysts is cyclic voltammetry (CV). However, this technique usually requires an inactive electrode material. One common problem arising e. g. in studying the oxygen reduction reaction (ORR) is the significant background contribution to the overall ORR current provided by many carbon-based and metal-based electrode materials. Furthermore, rotating ring-disc electrodes (RRDEs) made of common materials like glassy carbon/platinum (GC/Pt) can be affected by overlapping reduction potentials on the disc. Interference from overlapping reactions on the ring might also occur, particularly in connection with oxygen reduction and hydrogen peroxide oxidation in ORR studies. We present herein a novel subtraction method which allows a semi-quantitative description of homogeneous electrocatalysts and helps to overcome the overlapping problems described above using anthraquinone-2-sulfonate (AQS) as a “case study material” for the ORR.

Charge storage in concentrated electrolytes gives redox flow batteries (RFBs) a unique edge in grid-scale energy storage. It also creates a unique challenge in the design of organic molecules as alternatives to expensive vanadium salts. Molecules often come in the form of organic salts, and dissolve by ionic bond breakingand ion solvation, which can hardly be interpreted by “like dissolves like.” Here we use anthraquinone sulfonate salts as a model system to investigate factors underlying their aqueous solubility. We synthesize fifteen salts, measure their solubilities with UV–vis spectroscopy, and find that the solubility of the same quinone could change by three orders of magnitude with a change in its counter-cation. The same impact can come from the position and number of the sulfonate groups. We explain the results with the differences in the ion solvation energy and the lattice energy, the latter of which is corroborated by single-crystal X-ray diffraction. We also derive a simple method to semi-quantitatively predict the solubility of a quinone sulfonate salt based on that of a common sulfate salt. The work provides a physical-chemical base for understanding the solubilities of organic salts for the design of high capacity electrolytes for aqueous flow batteries.

[EN] This work describes a two-step procedure for the electrochemical coating of reduced graphene oxide (RGO) and polypyrrole anthraquinone sulfonate (PPyAQS) onto an activated carbon cloth (ACC) by cyclic voltammetry (CV). The textile samples were characterized by CV, electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge measurements using a sandwich-type (electrode/separator/electrode) cell designed to operate in three or two-electrode configurations. The presence of RGO onto the ACC surface optimized the electrosynthesis of PPyAQS and reinforced the stability of the polymer with the number of charge/discharge cycles. A retention capacity of 90% after 100 charge-discharge cycles together with an energy density of 7.8¿×¿10¿4¿W¿h¿cm¿2 at a power density of 1.8¿×¿10¿3¿W¿cm¿2 were obtained for the ACC/RGO/PPyAQS sample. The analyses by field emission scanning electron microscopy (FESEM) showed the RGO veils-like and PPyAQS glomerular structures covering the ACC-fibers. The Fourier transform infrared spectroscopy (FTIR) analyses not only detected the presence of PPy and AQS, but also, the changes in the molecular structure of PPyAQS, depending on its oxidation state, as consequence of the redox reactions occurred in the charge/discharge processes in the two-electrode cell., The authors wish to acknowledge to Chemviron Carbon who kindly donated the ZORFLEX® activated carbon fabric. The authors wish to thank the Spanish Agencia Estatal de Investigación de Economía (AEI) and European Union (FEDER funds) for the financial support (contract MAT2016-77742-C2-1-P). Tim Vickers is gratefully acknowledged for help with the English revision. Electron Microscopy Service of the UPV (Universitat Politècnica de València) is gratefully acknowledged for help with FESEM characterization.

FT-NMR experiments with scalar coupled multi-spin systems employing variation of the external magnetic field B are described, allowing one to discriminate interaction parameters because of their different dependence on B. The mayor part of the work deals with spin ensembles far away from their thermal equilibrium. In particular, hyper-polarization (HP) generated by means of chemically induced dynamic nuclear polarization (CIDNP), and T1-relaxation in liquids (fast motional regime) are studied. Field cycling experiments are shown to open possibilities for detailed studies of the relaxation behavior of individual protons, to provide access to the magnetic properties of the precursor radicals in which HP was formed, and for a proton site specific transfer of HP. Furthermore, the method allows one to differentiate mechanisms of CIDNP formation and the analysis of photoreactions. In low field the nuclear spin states of coupled multi-spin systems are collective states and hyper-polarization (HP) and spin-relaxation become properties of the entire spin system. As a consequence, field dependences of HP and T1-relaxation tend to become similar for nuclei fulfilling the condition of strong scalar coupling J (2J > L), within a time that corresponds to the inverse J-coupling. In nuclear magnetic relaxation dispersion (NMRD), this results in stepwise features being observed in the field regions where the Larmor precession L becomes comparable to the J-coupling. Zero-quantum-coherences are shown to occur in the spin density matrix upon non-adiabatic field variation and product formation (radical recombination). Variations of the time interval for free spin-evolution reveal characteristic quantum beats in the amplitudes of NMR signals after the coherences are transferred into polarization by non-adiabatic field variation. This way, HP is coherently transferred from primarily polarized spins to particular target spins within coupled spin systems by devising appropriate field cycling schemes, even in case the two spins are not noticeably coupled by spin-spin interaction in the high field of the spectrometer but only through a chain of coupled spacer- spins. Positions where nuclear spin states anti-cross are of particular significance for efficient transfer of HP. Depending on the timing of field cycling, maxima and minima are observed in these regions in various kinds of field dependent NMR experiments. The outcome of the experiments depends on the timing for the formation of HP, for free spin-evolution and for the field switches. Another consequence of the grouping of spin-levels in low field is that multiplet CIDNP is observable over entire multi-spin systems. The intensities of individual lines within multiplets characteristically depend on the RF-flip angle of the detection, and their nutation patterns are analyzed by means of Fourier expansion with respect to the flip angle. This technique separates the multiplet effects belonging to different sub-sets of nuclei by their nutation frequency (harmonic order) and yields spectra that exclusively reflect the mutual alignment of several coupled spins. The techniques described are applied to the analysis of the photolysis of the aromatic amino acids tyrosine (NATyrOH) and tryptophan (NATrpH) at = 308 nm in aqueous media. Their photolysis proceeds with the formation of CIDNP in the parent amino acids and in the residual protons of the solvent (HDO). From the field dependence of CIDNP and its time dependence at high magnetic field (TR-CIDNP), the photo-physics and -chemistry is analyzed. Ionization occurs from electronic singlet states, and is most efficient in basic solution, yielding solvated electrons (e-aq) and the radicals NATyrO• and NATrpH•+. Reduction of the parent amino acids by e-aq and subsequent reaction steps yield selectively deuterated amino acids and explains the strong CIDNP observed for HDO. The abovementioned amino acid radicals are further investigated in the presence of different triplet sensitizers, e.g. 2,2’-dipyridyl (DP) and anthraquinone-2-sulfonic acid (AQ2S), yielding the same amino acid radicals in spin correlated triplet radical pairs with the radicals of the dyes. Various combinations of the amino acid and dye radicals allow a comparison of the g-values from several CIDNP field dependences. Because of their inter- dependence, each g-value is extracted from more than a single field- dependence, and values of higher accuracy are obtained for the radicals under study. The mechanisms for efficient CIDNP formation upon restriction of molecular mobility are investigated on the photolysis of cyclic ketones. In the solid phase, no CIDNP is detected, and molecular mobility is found as a prerequisite for the formation of CIDNP. When confined by a matrix of plastic crystalline C6D12, the average exchange interaction, Jex, in the resulting bi- radicals tends to be determined by the matrix dimensions. When acetone is photolyzed in liquid and plastic crystalline C6D12, the photo-chemistry of the primary events remains the same, but the mechanism of CIDNP formation abruptly changes from S-T0 to S-T- at the phase transition, giving rise to comparable values for Jex as in the case of the cyclic ketones. In this case, the two radicals are not connected via a network of chemical bonds, and Jex is thus transmitted through space. The prospects of further applications of field dependent magnetic resonance techniques are discussed., Es werden FT-NMR Experimente an skalar gekoppelten Spinsystemen mit Magnetfeld-zyklisierung beschrieben, welche eine Unterscheidung von Wechselwirkungsparametern anhand ihrer Abhängigkeit vom externen Magnetfeld B erlauben. Der größte Teil der Arbeit befaßt sich mit Spinensembles weitab vom thermischen Gleichgewicht. Insbesondere Hyper-polarisation (HP) erzeugt durch chemisch induzierte dynamische Kernspinpolarisation (CIDNP) und T1-Relaxation in Flüssigkeiten werden studiert. Die Feldzyklisierung ermöglicht das Studium der Relaxation individueller Protonen, die Bestimmung magnetischer Wechsel- wirkungsparameter der Vorläuferradikale in denen HP erzeugt wurde, sowie einen Polarisationstransfer zu bestimmten ausgewählten Protonen. Des weiteren erlaubt die Methode eine Unterscheidung der Mechanismen für die photoinduzierte CIDNP Bildung und eine Analyse der beteiligten Photoreaktionen. Weil im niedrigen Magnetfeld die Kernspinzustände gekoppelter Spinsysteme kollektive Zustände aller beteiligten Spins sind, werden Phänomene wie Hyperpolarisation (HP) und Kernspinrelaxation zu Eigenschaften der gesamten Spinsysteme. Als Konsequenz werden die Magnetfeldabhängigkeiten der HP und T1-Relaxation für stark gekoppelte Kerne (2J > L) auf einer der inversen J-Kopplung entsprechenden Zeitskala tendenziell gleich. In den frequenzabhängigen Relaxationszeiten (NMRD) sind Stufen an den Feldstellen sichtbar, in denen die Larmor-Präzession der Größenordnung der J-Kopplung entspricht. Im Falle nicht-adiabatischer Magnetfeldvariation oder Produktbildung treten Null-Quantenkohärenzen auf. Durch Variation des Zeitintervalls für freie Spinevolution werden diese durch nicht-adiabatische Feldvariation in Polarisation überführt, und können in den Amplituden der NMR- Signale als charakteristische Quantenschwebungen detektiert werden. Auf diese Weise kann durch Anwendung geeigneter Feldzyklisierung HP von ursprünglich polarisierten Kernen auf unpolarisierte Kerne sogar dann übertragen werden, wenn die beiden Kerne im Hochfeld nicht direkt, sondern nur über weitere Kerne indirekt miteinander gekoppelt sind. Positionen, an denen Kernspinzustände kreuzen, sind für eine effiziente Übertragung von HP von besonderer Bedeutung und in unterschiedlichen feldabhängigen NMR Experimenten als Minima oder Maxima zu beobachten. Je nach Wahl der zeitlichen Parameter für die Bildung der HP, die freie Spinevolution und die Feldschaltung werden unterschiedliche Polarisationsmuster detektiert. Als weitere Folge der Gruppierung von Kernspinzuständen werden im Niederfeld Multiplett-Polarisationen beobachtet, die sich über das gesamte Spinsystem erstrecken. Die Amplituden einzelner Linien innerhalb des Spin-Multipletts hängen charakteristisch vom RF Nachweis- winkel  ab, und die Nutationsmuster werden durch Fourier-Zerlegung entlang  analysiert. Bei dieser Technik wird das Spektrum entsprechend den unterschiedlichen Nutations-frequenzen in Spektren verschiedener Ordnungen zerlegt, welche ausschließlich die gegenseitige Orientierung bestimmter Untergruppen gekoppelter Kerne wiedergeben. Die beschriebenen Techniken werden auf die Photolyse der aromatischen Aminosäuren Tyrosin (NATyrOH) und Tryptophan (NATrpH) bei =308nm in wäßriger Lösung ange-wandt, welche zur CIDNP Bildung in den Aminosäuren sowie den Protonen des Lösungsmittels (HDO) führt. Anhand der Feldabhängigkeit (FD-CIDNP) und zeitaufgelöster Messungen im Hochfeld (TR-CIDNP) wird die Photophysik und chemie analysiert. In basischer Lösung erfolgt die Ionisierung aus einem angeregten Singulett-Zustand, und führt zur Bildung von Radikalpaaren solvatisierter Elektronen (e-aq) mit den Radikalen NATyrO• und NATrpH•+. Die Reduktion der ursprünglichen Aminosäuren durch e-aq führt zu selektiv deuterierten Aminosäuren und erklärt die starke Polarisation von HDO. Die oben genannten Aminosäuren werden des weiteren in der Gegenwart geeigneter Farbstoffe, z.B. 2,2’-Dipyridyl (DP) und Anthrachinon-2-sulfonat (AQ2S) untersucht, was zur Bildung von spinkorrelierten Triplett-Radikalpaaren aus denselben Aminosäure Radikalen und Farbstoff-Radikalen führt. Unterschiedliche Kombination derselben Radikale in Paaren mit unterschiedlichen Farbstoff-Radikalen erlaubt einen Vergleich der g-Werte aus mehreren CIDNP Feldabhängigkeiten, so daß g-Werte höherer Genauigkeit für die untersuchten Radikale erhalten werden. Die Mechanismen der effizienten CIDNP Bildung bei Änderung molekularer Beweglichkeit wird anhand der Photolyse zyklischer Ketone untersucht. In der festen Phase bildet sich keine Polarisation, was zeigt, daß die Mobilität der Moleküle eine Voraussetzung für die CIDNP Bildung ist. Unter eingeschränkter Mobilität in der plastisch kristallinen Phase von C6D12 wird die mittlere Austauschwechselwirkung Jex in den resultierenden Diradikalen tendenziell durch die Dimensionen der Matrix bestimmt. Die Photolyse von Aceton in flüssigem und plastisch-kristallinem C6D12 zeigt bei gleich bleibender Photochemie eine abrupte Änderung im Polarisationsmechanismus von S-T0 nach S-T- beim Phasenübergang. Ähnliche Werte für Jex wie im Fall der zyklischen Ketone werden gefunden. In diesem Fall sind die zwei Radikale nicht über Bindungen verknüpft und die Jex wird durch den Raum übermittelt. Die Perspektiven zukünftiger Anwendungen feldabhängiger Messungen der magnetischen Resonanz werden diskutiert.