bluuebunny/crossref_metadata_2025_split huggingface dataset:
Asymmetric Synthesis of Substituted Piperidine Derivatives Based on the Indirect Cation Pool Method
Authors: Suga Seiji , Haisa Masahiro , Yoshioka Kazuki , Mitsudo Koichi 
Published: February 2020

N-Acyliminium ions having a piperidine skeleton were attractive because the functionalized piperidines frequently show interesting biologically properties. The “indirect cation pool method” 1) is useful to prepare a solution of synthetically valuable N-acyliminium ions having a protecting group that is labile under acidic conditions, because organic cations can be generated and accumulated under neutral conditions. In this presentation we demonstrated utilities of highly enantiomerically enriched chiral N-Acyliminium ions bearing a piperidine skeleton, which are generated by the indirect cation pool method.
Almost enantiomerically pure chiral precursor 2 was prepared by using the enantioselective lithiation strategy using chiral diamine 1 (Scheme 1).2)
N-Acyliminium ion pool 3 was then irreversibly generated from 2 by the treatment of ArS(ArSSAr)+, which was generated by low temperature electrolysis (Scheme 2). The reaction of 3 with allylstannane gave trans isomer in high diastereomer and enantiomer ratios. In contrast, the coupling between 3 and allylmagnesium bromide afforded cis isomer in high stereoselectivity. As a result, we could selectively synthesized two
1) Suga, S.; Matsumoto, K.; Ueoka, K.; Yoshida, J. J. Am. Chem. Soc.
2006, 128, 7710-7711. Matsumoto, K.; Suga, S.; Yoshida, J. Org. Biomol. Chem.
2011, 9, 2586-2596.
2) Coldham, I.; O’Brien, P.; Patel, J. J.; Raimbault, S.; Sanderson, A. J.; Stead, D.; Whittaker, D. T. E. Tetrahedron: Asymmetry
2007, 18, 2113–2119.

Figure 1
Role of the Unsaturated Groups in the Covalent Modification By the Carboxylate Oxidation: Mechanistic Aspects
Authors: Morales-Martínez Daniel , González Felipe J 
Published: February 2020

The oxidation mechanism of tetrabutylammonium carboxylates RCOO- involves the formation of radicals R• and carbocations R+, whose reactivity towards carbon surfaces allow the covalent grafting of the surface [1]. Experimental results have shown that the presence of the unsaturated terminal groups in the carboxylate structure are a determining factor for the covalent modification [2]. However, the role of these unsaturated groups in the mechanism is unknown. Therefore, in this work the study the oxidation of some carboxylates in presence of molecules with unsaturated groups (naphthalene and hexyne) was done. The results showed the intervention of a redox reaction between the carbocations R+ got from the carboxylate oxidation and the unsaturated molecule. This reaction regenerates the radical R• and allows the covalent modification. When naphthalene was used as additive, this molecule was also attached to the carbon surface. This observation arises from the fact that the oxidation response for the naphthalene groups attached to the surface was observed, confirming the electron transfer between the unsaturated group and the carbocatión R+. On the other hand, in the case of the hexyne, the solvent effect in the mechanism was studied, showing an association product between acetonitrile and hexyne. This fact helps to understand the specie that interacts with the carbocation in the redox reaction. These results give new insights about the covalent modification by carboxylate oxidation.
[1] C.P. Andrieux, F. Gonzalez, J.M. Savéant., J. Am. Chem. Soc., 119, 1997, 4292.
[2] D. M. Hernández-Morales, F. J. González., Electrochem.
Comm., 46, 2014, 48.

Figure 1
Electrochemical Characterization of Fischer Biscarbene Complexes of Chromium
Authors: Hoskovcová Irena , Metelková Radka , Váňová Hana , Tobrman Tomáš , Dvořák Dalimil , Ludvík Jiří 
Published: February 2020

Carbene complexes are characterized by presence of a formally double bond M=CR2. In electrophilic carbenes of Fischer type, the Mδ– = Cδ+ polarity of this bond is typical. An extended study of mononuclear complexes (CO)nM = C(NR’)R showed that there are two rather independent redox active centers present: oxidation is aimed on the metal atom, reduction on the carbene moiety.[1] This picture is in agreement with their HOMO and LUMO composition. [2]
Studied biscarbenes: (CO)5 Cr = C(X) - bridge - C(X) = Cr (CO)5 ; bridges: 1,3- or 1,4-phenylene, bis-, tris-, tetrakis-2,5-thienylene and their combinations; X: dialkylamino- or alkoxy-
Biscarbenes belong to molecules with multiple redox centres as they comprise two oxidizable metal atoms together with two reducible carbene moieties connected by a bridge. Electronic communication manifests itself in the course of redox process depending on the electronic properties of the bridge. It is evaluable by analysis of electrochemical behavior of the compounds in the frame of homologous series and with respect to their mononuclear analogs.
For oxidation, the extent of this communication can be identified by occurrence of two subsequent oxidation signals whereas in absence of the electronic communication both the metals are oxidized at the same potential. Potential of the first oxidation step of biscarbenes does not differ from that of monocarbenes indicating lack of the communication.
The reduction process of biscarbenes is influenced by the reducibility of the bridge itself, and by its participation in the LUMO. Since the reduction of biscarbenes is substantially easier than that of monocarbenes, the bridge is involved in the delocalization system and the amino or alkoxy substituent X plays important role in tuning of the reduction potential.
Recently, a new modular synthesis of biscarbenes [3] has open a way to molecules with longer bridging groups with various intramolecular conductivity.
Acknowledgement: Financial support from GACR 17-21770S and from specific university research (MSMT No 20/2017) is gratefully acknowledged.
References:
[1] Ludvík, J.; Hoskovcová, I.; in Advances in Organometallic Chemistry and Catalysis: The Silver/Gold Jubilee Int. Conf. on Organomet. Chem. Celebration Book; Pombeiro, A. J. L., Ed., Wiley 2014, pp. 653
[2] Kvapilová, H.; Hoskovcová, I.; Ludvík, J. ; Záliš, S. Organometallics
2014,
33, 4964,
[3] Váňová, H.; Tobrman, T.; Hoskovcová I.; Dvořák D. Organometallics
2016, 35, 2999
A Self-Sustained Photoelectrochemical System with Anodic Rgo/ZnIn2S4/g-C3N4 p-n-Hetero-Junction Catalyst for Antibiotic Wastewater Degradation
Authors: Yu Tingting 
Published: February 2020

The use of natural sunlight or indoor light for heterogeneous semiconductor photocatalysis is a promising alternative technology that could help address increasing environmental threats including water pollution and the energy crisis. A novel ternary hetero-junction of rGO/ZnIn2S4/g-C3N4 photo-electro-catalyst was prepared by a simple hydrothermal method.
By SEM or XRD, the morphology and the composition of the rGO/ZnIn2S4/g-C3N4, ZnIn2S4/g-C3N4, ZnIn2S4 and g-C3N4 were studied. Anode coated with rGO/ZnIn2S4/g-C3N4 has more smaller nanoparticles than others. This means that the positive effect of the layered GO and g-C3N4 increased the surface areas and made the catalyst more uniformly. XRD of the rGO/ZnIn2S4/g-C3N4 showed the typically peaks of ZnIn2S4. GO and g-C3N4 induce the formation and growth of ZnIn2S4 on the surface. The UV-vis diffuse reflection spectrums are compared in Fig. 2. Both the pure g-C3N4 and ZnIn2S4 have an absorption in the visible light region. After the combination of GO, ZnIn2S4 and g-C3N4, the enhanced absorption in the visible region is clearly observed compared to pure ZnIn2S4 or g-C3N4.
The anode was the rGO/ZnIn2S4/g-C3N4 catalyst coated on carbon fiber and carbon fiber with Pt nanoparticles was used as the cathode in a self-sustained catalytic fuel cell for triclosan degradation. Electron transferred spontaneously without additional applied voltage and this save the energy consumption. Triclosan (98.8%) was degraded after 30 minutes in the self-biased system (1000 Ω). Potential degradation mechanisms for pollutants were proposed. ZnIn2S4 was the P-type semiconductor and g-C3N4 was a N-type semiconductor. The conduction band of g-C3N4 is more negative than ZnIn2S4 and ZnIn2S4 is more negative than rGO. An interior bias can be produced to transfer the localized e- of g-C3N4 to ZnIn2S4 and and combination with the h+ of ZnIn2S4. Aeration and activation of molecular oxygen by the e- of ZnIn2S4 in the fuel cell, lead to the formation of reactive oxidizing species. The holes of g-C3N4 oxidized H2O and generated •OH for triclosan removed.
This photoelectrochemical system was conducive to the separation of photo-generated e-/hole pairs and e- transfer to the cathode irrespective of light. Compare to the traditional method, it can remove pollutants without light irradiation or any externally applied voltage. This new catalytic pollution control route can lower the energy consumption and may degrade many kinds of pollutants.
Figure captions:Mechanism of the self-biased photoelectrochemical system.

Figure 1
Square Wave Bipolar Electrochemistry for the Detection of Proteins
Authors: Shannon Curtis , Yu Songyan 
Published: February 2020

Rapid and specific quantitation of proteins is desirable for assays used at the point-of-care, as well as in clinical and research laboratories. The advantages of such devices include short turnaround times for acquiring critical data, low cost, and improved patient compliance with diagnosis and therapeutic regimens. Electrochemical detection is currently employed in a wide range of biosensors because of its inherent signal stability, high sensitivity, and ease of calibration. Our laboratories have developed the electrochemical proximity assay (ECPA) for protein detection, a sensitive and selective assay based on the electrochemical detection of surface-confined affinity complexes. ECPA demonstrates extremely high sensitivity (e.g., 10 fM for insulin).
Bipolar electrodes (BPEs) have been used for decades in industrial applications ranging from organic electrosynthesis to catalysis. Recently, sensor platforms have been reported in which electrochemiluminescence (ECL) is used to readout the state of a bipolar sensor operating under steady state conditions. In these measurements ECL intensity is directly proportional to the analyte concentration. In contrast to these conventional amperometric sensors, the ECPA signal is based on a surface limited reaction, and therefore does not lend itself to such a straightforward readout strategy. In this paper, we describe the development of an ECPA based on a bipolar platform in which a square wave voltage program is employed both to interrogate and reset the redox state of the surface confined affinity complex. Signal averaging over multiple cycles allows us to detect proteins at low concentration levels.
CO Adsorption on Different Oxide-Supported Catalysts Studied By a Combination of in Situ X-Ray Absorption Spectroscopy (XAS) and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS)
Authors: Roth Christina , Lentz Claudia , Melke Julia , Reinholz Uwe , Buzanich Ana Guilherme , Riesemeier Heinrich , Narayan Manoj Krishna Kayarkatte , Derr Igor , van der Bosch Nils 
Published: February 2020

Polymer electrolyte membrane fuel cells are promising systems in a future sustainable energy scenario. In the so-called power-to-gas strategy, the supply of hydrogen produced by intermittently available wind and solar energy will be converted into electricity on demand using a combination of water electrolysis and fuel cells. However, in order to make this dream a viable reality, material costs need to be dramatically reduced and material stability significantly enhanced.
State-of-the-art catalysts for fuel cell applications are Pt nanoparticles supported on various carbon substrates, predominantly carbon black, but also carbon nanotubes or graphene. However, in the harsh conditions at the fuel cell cathode, carbon is not stable and catalyst degradation due to carbon support corrosion becomes a key issue. One concept towards enhanced durability is to replace carbon by more stable support materials, such as electron-conducting (doped) oxides. Substituting carbon by e.g. tin oxide can alter the catalytic activity significantly, as in contrast to carbon supports the oxide phase may take part in the electrocatalytic reaction (so-called metal-support interaction).
We use CO as a probe molecule to study the interaction between Pt nanoparticles and the support, as the CO-Pt adsorption is affected by the support underneath the Pt nanoparticles. A novel in-situ cell was developed to allow for a combination of X-ray absorption spectroscopy (XAS) and diffuse infrared Fourier transform reflectance spectroscopy (DRIFTS) at the same time and with high quality [1, 2]. We thus benefit from the DRIFTS being able to distinguish between different CO binding sites (atop, bridge, analyzed also by DFT calculations [3]) and XAS being able to probe adsorption and nanoparticle structure. Differences in gas phase IR spectra during static and continuous CO adsorption on platinum nanoparticles reveal information on the influence of the support as well as on the binding sites. In this study, XAS and DRIFTS were recorded simultaneously for Pt/C, Pt/SnO2, Pt/ATO and Pt/ITO and analyzed with respect to kind of surface adsorbates, binding sites, coverage as well as nanoparticle structure.
[1] A. Drochner, M. Fehlings, K. Krauss, H. Vogel, Chem. Eng. Technol. 23 (2000) 319-322.
[2] C. Brieger, J. Melke, N. van der Bosch, A. Schökel, M. Krishna, I. Derr, M. Labza, C. Roth, J. Catal. 339 (2016) 57-67.
[3] C. Lentz, S. P. Jand, J. Melke, C. Roth, P. Kaghazchi, J. Molecular Catal. A: Chemical (2016), article in press.
(Physical and Analytical Electrochemistry Division David S. Grahame Award Address) Nanoscale Templates and Scaffolds for Electrochemical Device Applications
Authors: Birss Viola 
Published: February 2020

This talk will review some of our recent fuel cell-related research efforts, which have had a primary focus on increasing the lifetime and performance of both anode and cathode catalyst layers. In our recent work on PEM fuel cells, a new class of ordered, mesoporous carbon materials (both powders and free-standing scaffolds), with nano-engineered pore diameters and lengths, have been developed as support materials to better distribute and stabilize catalytic nanoparticles that are attached to their surface. These carbons have also been surface modified with a range of functional groups, showing that this can significantly alter their wettability, enhance their resistance to corrosion, better anchor catalytic nanoparticles, and are also beneficial in redox flow battery electrochemistry. These reproducibly ordered carbon scaffolds are also proving to be ideal for the investigation of the interactions of Nafion with Pt/carbon in relation to performance, especially as a function of carbon pore diameter, depth and surface hydrophilicity.
In parallel research related to catalyst supports, we have constructed ordered metal oxide nanotubular arrays, then converting them to conducting oxy-nitride forms, primarily to replace carbon. These metal oxy-nitrides undergo interesting redox transitions that will be shown to correlate with the activity of these materials (after deposition of Pt nanoparticles) towards the oxygen reduction reaction. Ordered surface arrays of Zr oxide nanotubes are also very promising for use in novel, nano-structured, high temperature solid oxide fuel cells.
Palladium Electrocatalysts Synthesis: Probing Reducing Agent Effect By XRD, XPS and ORR
Authors: Napporn Teko W. , Holade Yaovi , Canaff Christine , Poulin Suzie , Servat Karine , Arrii-Clasens Sandrine , Kokoh Kouakou Boniface 
Published: February 2020

Palladium (Pd) affinity with hydrogen and the subsequent effect on its physical structure is well known in literature. However, the majority of chemical methods for synthesizing Pd-based nanomaterials use sodium borohydride (NaBH4) as reducing agent, which releases hydrogen in aqueous solution. Pd can readily absorb this hydrogen in its lattice and forms PdHx hydrides. Alternatively, organic compounds such as ascorbic acid (AA) can be also used for reducing Pd ions in Pd nanoparticles. Pd nanomaterials are used for various reactions as those in fuel cells. In electrocatalysis where the electrode structure plays a key role, the subsequent impact on the catalytic properties should be carefully examined.. In the present work, reducing agent effect on Pd nanomaterials and their long-term chemical stability (during 2 years) were scrutinized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The impact of the hydrogen insertion (into Pd crystalline network) on the electrocatalytic properties of the synthesized Pd nanomaterials is investigated through oxidation of carbon monoxide and oxygen reduction reaction (ORR). It was observed that the surface state of the nanomaterials (Figures 1a-b) prepared by using sodium borohydride as reducing agent (Pd/C-NaBH4) is radically different from those obtained from L-ascorbic acid (Pd/C-AA) (Figure 1c). ORR starts with enhanced kinetics (E > 1 V vs. RHE) in a 4-electron process, producing p(H2O2) < 0.5% associated with excellent durability over 5000 cycles (Figures 1d-e). Both catalysts outperform all reported data for Pd electrocatalysts in alkaline medium. Finally, this work combined ex/in situ XPS and XRD analyses together with ORR as catalytic model towards a clear development in our understanding of Pd affinity with hydrogen and its electrocatalysis.

Figure 1. (a,b) HRTEM micrographs of the as-prepared nanomaterials of Pd/C-NaBH4 and Pd/C-AA and their corresponding high-resolution Pd 3d XPS spectra. (d) The normalized electrochemical surface area (ECSA) behaviour before and after 5000 cycles of accelerated potential cycling test (APCT: 0.6-1 V vs. RHE at 100 mV s−1 in O2-saturated 0.1 M KOH). Note that ECSA was evaluated at 50 mV s−1 and 5 mV s−1 scan rates and had the same trend. (e) ORR polarization curves recorded in a O2-saturated 0.1 M KOH solution at the ring (top) and disc (bottom) for 5 mV s−1 scan rate before (initial) and after APCT (5000 cycles) at RRDE speed of 1600 rpm.
Acknowledgments
The authors gratefully acknowledge financial support from the French National Research Agency ANR-ChemBio-Energy
References
1. Holade Y., et al., ChemElectroChem. 2, 592−599 (2015)
2. Holade Y., et al., RSC Advances 6, 12627−12637 (2016)

Figure 1
Adsorption of Benzyl Viologen Dichloride and Its Displacement By 3-Mercapto-1-Propanesulfonate during Copper Electrodeposition
Authors: Lu Jing , Barkey Dale P 
Published: February 2020

Typical copper electroplating baths used for super-conformal electrodeposition of copper interconnects in submicron-scale vias or trenches on semi-conductor devices contain additives for control of current distribution. The additives operate through absorption and desorption at the metal-electrolyte interface where they regulate the copper deposition rate. In this paper, adsorption of the leveler benzyl viologen dichloride (BV) and its displacement by the accelerant 3-mercapto-1-propanesulfonate(MPS) in an acid-sulfate copper plating bath were studied by means of chronoamperometry. The measured copper deposition rate was taken to be the sum of current densities for surfaces fully covered by either BV or MPS weighted by the fractional surface coverage of each component. At constant potential, current-time curves were recorded during stepwise addition of additives. Figure 1 shows results for addition of BV to a solution that contained no MPS. These measurements provide an isotherm for BV adsorption. Similar measurements were made for stepwise addition of MPS to solutions containing a given concentration of BV to determine the fractional displacement of BV as a function of MPS concentration.
Results showed that BV adsorption and its replacement by MPS are both potential and temperature dependent. Both processes fit the Langmuir model well at low BV or MPS concentrations. The dependence of the Langmuir constant on temperature and potential were also measured. The temperature dependence of the constant indicates that adsorption is a spontaneous exothermic process and its displacement by MPS is a spontaneous endothermic process.

Figure 1
Lithium Metal Deposition during Low Temperature Charge-Discharge Cycles in Lithium Ion Batteries Observed By in Situ 7li NMR
Authors: Arai Juichi , Nakahigashi Rie 
Published: February 2020

Lithium metal deposition is induced by a low temperature charging and causes failure in lithium ion batteries (LIBs). Lithium metal deposition during low temperature charge-discharge cycles in LIBs was investigated by in situ
7Li solid state nuclear magnetic resonance (NMR) spectroscopy. Cells composed of LiCoO2 (LCO) and graphite (MAG) were cycled with a continue current (CC) and pulse current (PC) mode at low temperatures (-5, 0 and 5 ℃) to examine kinetics of Li metal deposition. The growth rate, activation energy driven from Arrhenius low for Li metal deposition are evaluated by collecting cell capacities and NMR peak intensities at selected sampling points (e.g., Fig.1 for 0 ℃). The Li metal deposition started after one cycle and reaches the maximum value which is half of the Li amount contained in LCO after 10-20 cycles with CC mode operation at -5 ℃. While, no Li metal depositions were detected at all in the samples operated with PC modes (e.g., 1/2 duty 1 sec width pulse) even after 360000 cycle at -5 ℃. A good correlation between growth rate (n) of deposited Li metal and capacity fading rate (k) in CC mode operation.
Figure 1. Stacked in situ
7Li NMR spectra measured after 1, 10 and 20 cycle charge-discharge at 0 ℃ (experiments were done with two samples for each measurement).
(Invited) Safety of Aged Lithium-Ion Cells
Authors: Jeevarajan Judith A. , Mukherjee Partha P. , Juarez Robles Daniel 
Published: February 2020

Lithium-ion batteries have been introduced into large stationary energy storage systems. In recent years, used automotive batteries are being repurposed for use in stationary energy storage systems. It is of significant importance to understand the hazards associated with used cells and batteries and also determine the changes that occur to the cell components such as cathode, anode, separator and electrolyte. Under this study, cells were cycled to various levels of capacity loss and subjected to safety tests such as external short and overcharge. The cell cycling protocol included cycling the cells to the full end of charge and end of discharge voltages as well as reduced end of charge and end of discharge voltages. Cells were removed at 10%, 15% and 20% capacity loss and subjected to external short and overcharge tests. Cells were also cycled under hybrid electric vehicle usage profiles and at different temperatures to characterize the changes.