bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Nitrogenase Electrochemistry for Ammonia Production
Authors: Cai Rong , Milton Ross , Abdellaoui Sofiene , De Lacey Antonio L. , Pita Marcos , Sahin Selmihan , Minteer Shelley 
Published: February 2020

The Haber-Bosch process, responsible for producing NH3 from H2 and N2, ranks as one of the most important discoveries in the history of chemistry. Its industrial application in synthetic fertilizers contributed to the continuously increasing population and their quality of life. The Haber-Bosch process, however, is a very energy-intensive process with high temperature (500 °C) and pressure (20 MPa) required for efficient NH3 production. Over 1 % of the world’s energy sources were consumed in order to produce ~140 megatons of NH3 in 2015. Additionally, 3 % of global CO2 emissions are due to the Haber-Bosch related technology. A renewable strategy for ammonia production would therefore be valuable.
In nature, the ability to reduce N2 to NH3 is limited to a group of bacteria and archaea classified as diazotrophs, all of which share an enzyme called nitrogenase. Using methylviologen (N,N’-dimethyl-4,4’-bipyridinium) to shuttle electrons to nitrogenase, N2 reduction to NH3 can be mediated at an electrode surface. The coupling of this nitrogenase cathode with a bioanode which utilizes the enzyme hydrogenase to oxidize molecular hydrogen (H2) results in an enzymatic fuel cell (EFC) that is able to produce NH3 from H2 and N2, while simultaneously producing an electrical current. To demonstrate this, 60 mC of charge was passed across H2/N2 EFCs, which resulted in the formation of 286 nmol NH3 mg-1 MoFe protein, corresponding to a Faradaic efficiency of 26.4 %. Importantly, this EFC produces NH3 and electrical energy in a carbon-neutral manner.
A protective FeSII protein, which can reversibly lock nitrogenase into a multicomponent protective complex upon exposure to low concentrations of O2, was incorporated into a nitrogenase bioelectrosynthetic cell whereby NH3 was produced using air as a substrate. This marks a significant step forward in overcoming the crippling limitation of nitrogenase’s sensitivity toward O2.
Microelectrode Arrays: Moving Toward the Synthesis of More Complex Surfaces
Authors: Moeller Kevin D , Yeh Nai-Hua , Nguyen Bichlien 
Published: February 2020

Microelectrode arrays can be ideal tools for probing a host of biological interactions. Yet in spite of their general utility, their use is still limited by our ability to construct complex molecular surfaces that can spatially isolate molecules in specific locations proximal to specific electrodes.
With this in mind, we have been developing electrochemically based tools that allow for the placement of molecules by specific electrodes in an array and then probe the binding of those molecules with biological targets in “real-time”. Yet while those methods are very useful, they have limits. They enable the analysis of smaller libraries, but are not as effective if one wants to probe a receptor with even a medium size library. The problem is that the tools developed to date require a library to be synthesized at a remote site and then transfer that library to the array one molecule at a time. For larger libraries, this is time consuming and cumbersome. A better strategy would be to build the library directly on the array.
The approach to building a molecular library typically involves a diversification strategy like the one shown in Scheme 1. In the Scheme, P1-P4 represent protecting groups that can be orthogonally removed. But what are the orthogonal protecting groups that can be removed site-selectively on a microelectrode array so that such a strategy can be used to synthesize more complex molecular surfaces? Furthermore, are the current surfaces used on the arrays compatible with such an intensive synthetic effort?
In the talk to be given, we will describe initial findings that begin to address these questions as we push for the development of new methods that will allow for the greater community to take full advantage of what microelectrode arrays can offer.

Figure 1
Controlled Synthesis of Organic Frameworks of Pillar[6]Arene By Electrochemical Oxidation
Authors: Inagi Shinsuke , Tsuneishi Chiaki , Nishiyama Hiroki , Tomita Ikuyoshi , Ogoshi Tomoki 
Published: February 2020

Recently, the novel synthesis of supramolecular 2D sheet materials composed of a pillar[6]arene (a cyclic hexamer of p-arylenemethylene), driven by charge-transfer (CT) interaction between its hydroquinone form and its benzoquinone form was reported [1]. When the hydroquinone form of pillar[6]arene was oxidized with an oxidant in a methanol solution, a generated partially oxidized benzoquinone form underwent CT complex formation with its pristine form to 2D-assemble with a hexagonal packing, followed by further assembly to form fibrils. In order to control the size and shape of the material, we investigated the electrochemical oxidation of a pillar[6]arene, and resulted in the successful formation of uniform hexagonal cylinder structures on an electrode surface (Figure 1) [2].
[1] T. Ogoshi, K. Yoshikoshi, R. Sueto, H. Nishihara, T. Yamagishi, Angew. Chem. Int. Ed. 2015, 54, 6466-6469.
[2] C. Tsuneishi, Y. Koizumi, R. Sueto, H. Nishiyama, K. Yasuhara, T. Yamagishi, T. Ogoshi, I. Tomita, S. Inagi, Chem. Commun. 2017, 53, 7454-7456.

Figure 1
Reactions Using Organo-Dications As Redox-Switchable Catalysts in Batch and Flow Systems
Authors: Suga Seiji , Kurihara Yuusuke , Hirata Takayuki , Tanaka Hiroki , Mitsudo Koichi 
Published: February 2020

Organocations such as trityl cation effectively promote a variety of organic reactions. The electrochemically generated carbocations [1] can also be utilized for the efficient promoter of these reactions and are applicable to a redox-switchable system which involving entirely organic compounds. The transformation using a redox-switchable catalyst is an emerging research field that seeks to regulate chemical reactions by the simple reduction-oxidation manipulation. For example, when the solution of an aldehyde, enol silyl ether and a precursor of organo-dication were subjected to the electrochemical oxidation, the aldol reaction smoothly started. Subsequent electrochemical reduction of the solution brought the reaction to a stop. We would demonstrate the utility and applicability of the present investigation. Some preliminary applications to the electrochemical microflow system will also be discussed.
[1] M. Okajima, S. Suga, K. Itami, J. Yoshida, J. Am. Chem. Soc.
2005, 127, 6930.
Differences in Reactivity of Primary Amines, Diamines and Amino Acids with Orthophthalaldehyde – Spectroelectrochemistry and Structure of Products
Authors: Ludvík Jiří , Donkeng Joel , Kantnerová Kristýna 
Published: February 2020

Orthophthalaldehyde (OPA) is used in analytical and biologically significant reactions for many years due to its specific reactivity with N-, S- and O- nucleophiles [1,2]. Besides the analytical method for determination of amino acids, the solution of OPA is broadly applied in hospitals as a disinfecting agent for surgery instruments made from plastics. In the literature, there is a simplified "traditional" description of main products and the expected mechanism related to the applications, however, our recent systematic research in this field revealed several unobserved phenomena showing that the mechanisms are not understood [3,4].
Due to the ortho-position of the two carbonyls, OPA contains a system of two communicating redox centers exhibiting very specific reactivity. The main feature of the OPA behavior is ability to fast intramolecular cyclization of primary intermediates of classic addition and condensation reactions of a carbonyl with a nucleophile. As a consequence, the reaction mechanism and formation of products strongly depends on the structure of the nucleophile itself, since the cyclization and inter-as well as intramolecular follow-up reactions offer a number of structural and stoichiometric possibilities.
In the present report (spectro)electrochemical monitoring of the reactions of OPA with various types of nucleophiles (water which is, in fact, the most abundant nucleophile in the system, primary amines, 1,2- and a,ω-diamines derived from aromatic, aliphatic or alicyclic species, amino acids, thiols and various molecules containing two different nucleophilic centers) will be discussed and the mechanistic conclusions will be supported by identification of products by MS, NMR and x-ray structural analyses [5-9].

Acknowledgments

The research was supported by GA CR (project No. 17-18108S) and by institutional support (RVO: 61388955).

References

[1] Roth, M. Anal. Chem.
1971, 43 (7), 880–882.
[2] Simoes, M.; et al. J. Basic Microbiol.
2007, 47, 230–242.
[3] Zuman, P. Chemical Reviews
2004, 104 (7), 3217–3237.
[4] Zuman, P.; et al. Electroanalysis
2009, 21 (3-5), 645–649.
[5] Kantnerová, K.; Donkeng Dazie, J.; Ludvík, ECS Transactions
2015, 60 (26), 13-22.
[6] Donkeng Dazie, J.; Liška, A.; Ludvík, J.; Fábry, J.; Dušek, M. Acta Crystallogr., Sect. C: Cryst. Struct. Commun.
2016, 72, 518-524.
[7] Donkeng Dazie, J.; Liška, A.; Ludvík, J. J. Electrochem. Soc.
2016, 163 (9), G127-G132.
[8] Donkeng Dazie, J.; Liška, A.; Ludvík, J.; Fábry, J.; Dušek, M.; Eigner, V.

Kristallogr.
2017, DOI: https://doi.org/10.1515/zkri-2016-2001

[9] Donkeng Dazie, J.; Liška, A.; Urban, J.; Ludvík, J. J. Electroanal. Chem. – submitted 2017.
Electrochemistry of (Thia)Calix[4]Arenes Bearing Various Redox Probes
Authors: Liška Alan , Modi Krunal M. , Ludvík Jiří 
Published: February 2020

Calixarene skeleton is a stable supramolecular frame which is, however, electrochemically inactive. Introduction of one or more electroactive substituents to the molecule enable its electrochemical investigation, moreover, the interpretation of series of electrochemical data can reveal the distribution of electrons in the molecule, their mutual communication, shape of the molecule, its dynamic behaviour etc. Suitable substitution on the upper and/or lower rim can influence not only geometry of the molecule, but also its reactivity and coordination ability. Generally, structure modification or introduction of heteroatoms lead to unusual and surprising properties of the whole supramolecule.
Thiacalix[4]arenes contain four aromatic units connected by sulphur atoms. This contribution will be focused first on two series of 1,3-alt-conformers bearing one or more nitro groups as electrochemical probes and on other calixarene derivatives bearing various redox probes..
The first series consists of eight para-tetranitro derivatives which resemble each other in their electrochemical response: first two two-electron reversible waves are followed by final step during which a tetrakis(hydroxylamino) derivative is formed. This reduction pattern is analogous to the “standard” methylene-bridged para-tetranitrocalix[4]arenes, where no mutual electron interaction takes place, all nitrogroups are totally independent and a stable tetraanion tetraradical is formed [1,2].
The second series includes four meta-nitro derivatives. Generally, the electroreductive behaviour of them is more complicated (except the first member which bears only one nitrogroup). Presence of two and three nitro groups in the same molecule in position meta towards the lower rim (that means in position ortho- and para- towards the thia bridges), exhibit clear intramolecular communication. [3,4]. This phenomenon was confirmed by quantum chemical calculations.
In the third series some newly synthesized derivatives with various redox probes are presented.

Acknowledgement: This work was supported by the GACR grant No. 17-18108S and by institutional support RVO: 61388955. The authors thank prof. Pavel Lhoták for granting the compounds.
Krunal M. Modi -

On leave from Chemistry Department, Gujarat University, Ahmedabad-380009 India

References:

[1] Alan Liška, Pavel Vojtíšek, Albert J. Fry, Jiří Ludvík: J.Org.Chem 78 (2013) 10651 – 10656.
[2] Alan Liška, Marco Rosenkranz, Jiří Klíma, Lothar Dunsch, Pavel Lhoták, Jiří Ludvík: Electrochimica Acta 140 (2014) 572 – 578.
[3] Alan Liška, Karolína Flídrová, Pavel Lhoták, Jiří Ludvík: Monatsh. Chem. 146 (2015) 857–862.
[4] Alan Liška, Jiří Ludvík: Current Opinions in Electrochemistry - submitted
Electrochemical Preparation of Aryl Mom Ethers
Authors: de Kruijff Goswinus H. M. , Waldvogel Siegfried R. 
Published: February 2020

In organic synthesis, methoxymethyl (MOM) ethers are frequently used as acid-labile protecting group [1] or leaving group in aryl cross-coupling reactions [2]. Their preparation commonly involves MOM chloride, a carcinogenic liquid with high vapour pressure which should be avoided as much as possible [3].
Therefore, we started to synthezise aryl MOM ethers without the use of MOM chloride by application of sustainable electrosynthetic methods [4]. Anodic decarboxylation of 2-aryloxy acetic acids under non-Kolbe conditions and trapping of the corresponding cation with methanol gives the desired MOM ethers (Figure 1). Indeed, this pathway is described for few aliphatic α-alkoxyacetic acids [5] and unsubstituted phenoxyacetic acid [6], but scope of this transformation to prepare substituted aryl MOM ethers has not been investigated so far.
We now present our studies on the preparation of substituted aryl MOM ethers by anodic decarboxylation using an undivided cell setup. A wide range of substituents on the phenyl moiety is tolerated, giving access to valuable protected phenols [7].
References:
[1] P. G. M. Wuts, T. W. Greene, Greene's Protective Groups in Organic Synthesis, John Wiley & Sons, Inc,
Hoboken, NJ, USA, 2006.
[2] J. W. Dankwardt, Angew.
Chem. Int. Ed.
2004, 43, 2428-2432.
[3] Encyclopedia of Reagents for Organic Synthesis, John Wiley & Sons, Ltd, Chichester, UK, 2001.
[4] B. A. Frontana-Uribe, R. D. Little, J. G. Ibanez, A. Palma, R. Vasquez-Medrano, Green Chem.
2010, 12, 2099-2119.
[5] H.-J. Schäfer in Topics in Current Chemistry, Vol. 152 (Ed.: E. Steckhan), Springer, Berlin Heidelberg, 1990.
[6] S. I. Rosca, E.-M. Ungureanu, M.-G. Alexandru, U. P. B. Sci. Bull., Series B, 2007, 69, 3-10.
[7] G. H. M. de Kruijff, S. R. Waldvogel, in preparation.

Figure 1
Electrochemical Synthesis of Azanucleosides
Authors: Okamoto Kazuhiro , Ishii Seika , Shoji Takao , Chiba Kazuhiro 
Published: February 2020

Recently, the nucleic acid medicine receiving a lot of attention because of various drug targets and few side effects compared with conventional low molecular medicine. The numerous nucleoside analogues have been reported. Especially, azanucleosides, in which the oxygen atom of furanose ring has been replaced with a nitrogen atom, show anticancer, antivirus, and antileukemia activity. Furthermore, azanucleosides exhibit tolerance towards nucleases when their incorporate into oligonucleotides. However, the traditional synthetic strategy requires multiple steps and harsh conditions, thereby limiting to obtain desired product with high yield.
We developed mild condition and efficient synthesis of azanucleosides from prolinol derivative using by an electrochemical reaction in a 1.0 M lithium perchlorate-nitroethane and small amount of acetic acid mixture medium with a glassy carbon anode and platinum cathode. In this reaction, intermediate iminium cation was generated through anodic oxidation of N-α position. The nitroalkane solvent is suitable for cation-pool method because the cation intermediate species are stabilized at nearly room temperature. After 2.6 F of electricity, the nucleophiles were added into reaction medium and stirred overnight. We used each nucleobases (N6-benzoyl adenine: A(Bz), N4-benzoyl cytosine: C(Bz), N2-isobutyryl guanine: G(Ib)) as nucleophiles. The coupling with thymine (T) was carried out through silyl Hilbert-Johnson reaction from other prolinol derivative that has hydroxyl group in N-α position. It was also prepared by anodic oxidative C-H activation. As a result, desired deoxyribo-azanucleosides was obtained.
However, the desired azanucleosides was generated as α and β anomer by equally ratio in this reaction. The natural nucleic acids are composed by only β-anomer nucleosides. In this reason, to regulate the anomeric selectivity is very important. Now, we are challenging the stereoselective synthesis of these deoxyribo-azanucleosides. Furthermore, we are applying our electrochemical method for the synthesis of ribo-azanucleosides.
Electrocatalytic Difunctionalization of Alkenes
Authors: Lin Song 
Published: February 2020

Alkene difunctionalization represents one of the most efficient methods for the construction of highly functionalized products from simple and readily available starting materials. These transformations are usually promoted by a highly reactive electrophilic reagent (e.g., peracid, metal oxide, and hypervalent iodine), which engages the unactivated π electrons of the alkene to form two new vicinal chemical bonds in either a concerted or a stepwise fashion. The requirement for these highly reactive electrophiles can often lead to functional group compatibility issues, which may limit their broad use in late-stage synthesis. In addition, many of these reagents generate substantial amounts of byproducts upon reaction.
Herein, we describe the development of alkene difunctionalization reactions via electrochemical generation of radical intermediates. Electrochemistry allows for the generation of highly reactive intermediates in situ from simple and readily available feedstocks and with high atom economy. The heteroatom-based radical can be produced directly from the corresponding anion via anodic oxidation, and will add across a C=C bond in the alkene substrate to yield a carbon based radical. Due to the high reactivity and promiscuity of this carbon radical species, a variety of undesired pathways, including polymerization, dimerization, elimination, and over-oxidation, could follow. In order to realize difunctionalization with high selectivity in addition to high stereochemical control, we introduce a metal catalyst that could associate with the second heteroatom-based radical and deliver it to the carbon radical via a catalyst-controlled mechanism. The therefore reduced catalyst could then also be oxidized on the anode to complete the catalytic cycle. Judicious choice of catalyst and careful control of the applied electrochemical bias allow for the regulation of the reactivity and selectivity of the alkene difunctionalization process.
A Modular Flow-through Platform for Spectroelectrochemical Analysis
Authors: Noyhouzer Tomer , Snowden Michael Edward , Tefashe Ushula M , Mauzeroll Janine 
Published: February 2020

Electrochemical flow systems are broadly used in research and applied fields such as environmental, industrial and medical monitoring because they cost-effectively determine concentrations, yield energy data (redox potential) and elucidate reaction mechanism via kinetic analysis. The use of a flow system enables the automation of a process and can provide a much needed design flexibility. Moreover, the combination of reaction-oriented electrochemical flow systems with species-focused spectroscopy enables complete analysis of reactions involving multiple electron transfer steps, as well as unstable intermediates.
In this work, we present a new type of flow platform for electrochemical and spectroelectrochemical measurements is presented. Finite element method simulations confirm that the hydrodynamic profile within the device is not turbulent, and provides an analytical platform for the investigation of homogenous kinetics, radical lifetimes and reaction mechanisms. The modular “plug and play” configuration of the platform allows one to carry out electrochemistry and spectroscopy individually or simultaneously. Specific demonstrations of electroanalytical measurements using the flow system platform includes voltammetric analysis of organometallic compounds and quantitative analysis of ascorbic acid in commercial orange juice samples. Combined spectroelectrochemical (SEC) demonstrations include electrochemical luminescence of ruthenium compounds and ligand exchange reactions of iron complexes using UV-Vis spectroscopy.
Noyhouzer et al, Anal. Chem., 2017, 89 (10), pp 5246–5253

Figure 1
Surface-Enhanced Raman Spectroelectrochemistry with Screen-Printed Electrodes for Quantitative Analysis
Authors: Fanjul Bolado Pablo , Martín Yerga Daniel , Junquera Pérez Alejandro , González García María Begoña , Hernández Santos David 
Published: February 2020

Electrochemically roughened silver surfaces have been widely employed for Surface-enhanced Raman scattering (SERS) assays. In most cases, the roughening process is usually performed ex situ with a specific electrolyte solution and, afterwards, the analyte is adsorbed on the substrate for the detection. This procedure has several possible issues: the final state of the substrate could not be the optimum for enhancing the SERS effect, the surface could become passivated between the roughening and the detection steps, decreasing the SERS activity, and the step for the analyte adsorption could take several minutes. Moreover, one of the main issues of SERS-based assays is the reproducibility between experiments and these substrates have been mainly used for qualitative studies. However, there is a strong scientific interest for increasing the applicability of SERS assays for quantitative studies with reproducible and simple methods. Screen-printed electrodes could be promising SERS substrates because they are mass-fabricated using the well-established thick-film technology leading to precise, disposable, low-cost and easy-to-use devices.
In this work, the real-time in situ electrochemical roughening of readily-available metal screen-printed electrodes is proposed to obtain a quantitative and precise SERS detection of several species at low concentrations using a fast and cost-effective methodology. The roughening and the analytical detection are carried out simultaneously, solving the typical issues of the ex situ preparation. The time-resolved character of this method allows to get dynamic information about the processes leading to a SERS active substrate and correlate them with the microscopic electrode structure at various stages of the substrate preparation. Results show a good linearity between the SERS signals and low concentrations of several species with a good precision between measurements.