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1.
J Am Chem Soc ; 146(22): 15230-15250, 2024 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-38769770

RESUMO

Due to their eco-sustainability and versatility, organic electrodes are promising candidates for large-scale energy storage in rechargeable aqueous batteries. This is notably the case of aqueous hybrid batteries that pair the low voltage of a zinc anode with the high voltage of a quinone-based (or analogue of quinone-based) organic cathode. However, the mechanisms governing their charge-discharge cycles remain poorly understood and are even a matter of debate and controversy. No consensus exists on the charge carrier in mild aqueous electrolytes, especially when working in an electrolyte containing a multivalent metal cation such as Zn2+. In this study, we comprehensively investigate the electrochemical reactivity of two model quinones, chloranil, and duroquinone, either diluted in solution or incorporated into carbon-based composite electrodes. We demonstrate that a common nine-member square scheme proton-coupled electron transfer mechanism allows us to fully describe and rationalize their electrochemical behavior in relation to the pH and chemical composition of the aqueous electrolyte. Additionally, we highlight the crucial role played by the pKas associated with the reduced states of quinones in determining the nature of the charge carrier that compensates for the negative charges reversibly injected in the active material. Finally, contrary to the widely reported findings for Zn/organic batteries, we unequivocally establish that the predominant solid-state charge carriers in Zn2+-based mild aqueous electrolytes are not multivalent Zn2+ cations but rather protons supplied by the weakly acidic hexaaqua metal ions (i.e., [Zn(H2O)6]2+]).

2.
Chem Sci ; 13(9): 2764-2777, 2022 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-35356676

RESUMO

The strength of autocatalytic reactions lies in their ability to provide a powerful means of molecular amplification, which can be very useful for improving the analytical performances of a multitude of analytical and bioanalytical methods. However, one of the major difficulties in designing an efficient autocatalytic amplification system is the requirement for reactants that are both highly reactive and chemically stable in order to avoid limitations imposed by undesirable background amplifications. In the present work, we devised a reaction network based on a redox cross-catalysis principle, in which two catalytic loops activate each other. The first loop, catalyzed by H2O2, involves the oxidative deprotection of a naphthylboronate ester probe into a redox-active naphthohydroquinone, which in turn catalyzes the production of H2O2 by redox cycling in the presence of a reducing enzyme/substrate couple. We present here a set of new molecular probes with improved reactivity and stability, resulting in particularly steep sigmoidal kinetic traces and enhanced discrimination between specific and nonspecific responses. This translates into the sensitive detection of H2O2 down to a few nM in less than 10 minutes or a redox cycling compound such as the 2-amino-3-chloro-1,4-naphthoquinone down to 50 pM in less than 30 minutes. The critical reason leading to these remarkably good performances is the extended stability stemming from the double masking of the naphthohydroquinone core by two boronate groups, a counterintuitive strategy if we consider the need for two equivalents of H2O2 for full deprotection. An in-depth study of the mechanism and dynamics of this complex reaction network is conducted in order to better understand, predict and optimize its functioning. From this investigation, the time response as well as detection limit are found to be highly dependent on pH, nature of the buffer, and concentration of the reducing enzyme.

3.
Chem Commun (Camb) ; 57(86): 11374-11377, 2021 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-34647564

RESUMO

Here we report a simple autocatalytic organic reaction network based on the redox chemistry of quinones and reactive oxygen species. Autocatalysis arises from the cross-activation between the H2O2-catalyzed deprotection of a pro-benzoquinone arylboronic ester probe and the benzoquinone-catalyzed H2O2 production through redox cyling with ascorbate in an aerated buffered solution.

4.
Chemphyschem ; 22(15): 1611-1621, 2021 08 04.
Artigo em Inglês | MEDLINE | ID: mdl-34038617

RESUMO

Molecule based signal amplifications relying on an autocatalytic process may represent an ideal strategy for the development of ultrasensitive analytical or bioanalytical assays, the main reason being the exponential nature of the amplification. However, to take full advantage of such amplification rates, high stability of the starting co-reactants is required in order to avoid any undesirable background amplification. Here, on the basis of a simple kinetic model of cross-catalysis including a certain degree of intrinsic instability of co-reactants, we highlight the key parameters governing the analytical response of the system and discuss the analytical performances that are expected from a given kinetic set. In particular, we show how the detection limit is directly related to the relative instability of reactants within each catalytic loop. The model is validated with an experimental dataset and is intended to serve as a guide in the design and optimization of autocatalytic molecular-based amplification systems with improved analytical performances.

5.
Chemistry ; 25(31): 7534-7546, 2019 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-30809849

RESUMO

Herein, a new molecular autocatalytic reaction scheme based on a H2 O2 -mediated deprotection of a boronate ester probe into a redox cycling compound is described, generating an exponential signal gain in the presence of O2 and a reducing agent or enzyme. For such a purpose, new chemosensing probes built around a naphthoquinone/naphthohydroquinone redox-active core, masked by a self-immolative boronic ester protecting group, were designed. With these probes, typical autocatalytic kinetic traces with characteristic lags and exponential phases were obtained by using either UV/Visible or fluorescence optical detection, or by using electrochemical monitoring. Detection of concentrations as low as 0.5 µm H2 O2 and 0.5 nm of a naphthoquinone derivative were achieved in a relatively short time (<1 h). From kinetic analysis of the two cross-activated catalytic loops associated with the autocatalysis, the key parameters governing the autocatalytic reaction network were determined, indirectly showing that the analytical performances are currently limited by the slow nonspecific self-deprotection of boronate probes. Collectively, the present results demonstrate the potential of this new exponential molecular amplification strategy, which, owing to its generic nature and modularity, is quite promising for coupling to a wide range of bioassays involving H2 O2 or redox cycling compounds, or for use as a new building block in the development of more complex chemical reaction networks.

9.
Faraday Discuss ; 203: 301-313, 2017 10 13.
Artigo em Inglês | MEDLINE | ID: mdl-28726928

RESUMO

Five N-phenylviologen (PV2+) derivatives have been synthesized and their electrochemical behavior in the presence of halide anions has been studied. Further investigations were carried out by 1H and 19F NMR spectroscopy at different chloride concentrations. This is the first time a systematic study combines cyclic voltammetry and NMR spectroscopy in order to analyse the contribution of halogen bonding among the various non-covalent interactions between iodinated N-phenylviologens. The results show strong evidence for a significant "halogen bonding effect" in the interaction between halides and the iodo-tetrafluoro-phenylviologen PV2+-C6F4I. A significant influence of halogen bonding on reduction potentials of the novel halogen bond donor PV2+-C6F4I has been evidenced resulting in the first example of "inverse redox switching" of an XB-donor being partially deactivated upon reduction. Furthermore the particular binding properties of the perfluorinated derivative PV2+-C6F5 towards chloride are discussed considering a possible contribution of π-anion interaction in solution.

10.
Chem Commun (Camb) ; 50(93): 14616-9, 2014 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-25313384

RESUMO

Cyclic voltammetry has been used for the first time to probe and to control the formation of non-covalent halogen bonding (XB) via redox switching. These results strongly encourage the use of electrochemistry as an economical and precisely controllable tool for the investigation of XB in solution.

11.
Chemistry ; 20(6): 1530-8, 2014 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-24382747

RESUMO

Herein, we report the development of biohybrid catalysts that are capable of catalyzing the aldol reaction. The use of biotinylated imidazolium salts in combination with racemic or enantiomerically pure catalytic anions allowed us to study the adaptive and cooperative positioning of the anionic catalyst inside the protein. Supramolecular encapsulation of the biotinylated catalyst into avidin resulted in good selectivity for the aldol reaction performed in ionic liquid/water mixtures.


Assuntos
Aldeídos/química , Avidina/química , Imidazóis/química , Líquidos Iônicos/química , Biotinilação , Catálise , Sais/química
12.
Anal Chem ; 85(12): 5770-7, 2013 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-23706008

RESUMO

Ionic liquid self-assembled monolayers (SAM) were designed and applied for binding streptavidin, promoting affinity biosensing and enzyme activity on gold surfaces of sensors. The synthesis of 1-((+)-biotin)pentanamido)propyl)-3-(12-mercaptododecyl)-imidazolium bromide, a biotinylated ionic liquid (IL-biotin), which self-assembles on gold film, afforded streptavidin sensing with surface plasmon resonance (SPR). The IL-biotin-SAM efficiently formed a full streptavidin monolayer. The synthesis of 1-(carboxymethyl)-3-(mercaptododecyl)-imidazoliumbromide, a carboxylated IL (IL-COOH), was used to immobilize anti-IgG to create an affinity biosensor. The IL-COOH demonstrated efficient detection of IgG in the nanomolar concentration range, similar to the alkylthiols SAM and PEG. In addition, the IL-COOH demonstrated low fouling in crude serum, to a level equivalent to PEG. The IL-COOH was further modified with N,N'-bis (carboxymethyl)-l-lysine hydrate to bind copper ions and then, chelate histidine-tagged biomolecules. Human dihydrofolate reductase (hDHFR) was chelated to the modified IL-COOH. By monitoring enzyme activity in situ on the SPR sensor, it was revealed that the IL-COOH SAM improved the activity of hDHFR by 24% in comparison to classical SAM. Thereby, IL-SAM has been synthesized and successfully applied to three important biosensing schemes, demonstrating the advantages of this new class of monolayers.


Assuntos
Técnicas Biossensoriais/métodos , Imidazóis/química , Líquidos Iônicos/química , Humanos , Ressonância de Plasmônio de Superfície/métodos
13.
Angew Chem Int Ed Engl ; 51(20): 4981-4, 2012 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-22488881

RESUMO

Frozen: the spontaneous crystallization of an achiral compound in a chiral conformation is used as the unique source of chirality in an absolute asymmetric synthesis of tertiary amino acids. The dynamic axial chirality of tertiary aromatic amides is frozen in a crystal and is responsible for the stereoselectivity of the deprotonation/alkylation. α-Amino acid derivatives are synthesized in up to 96 % ee.


Assuntos
Aminoácidos/síntese química , Aminoácidos/química , Catálise , Conformação Molecular , Estrutura Molecular , Estereoisomerismo
14.
Chem Commun (Camb) ; 47(38): 10644-6, 2011 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-21879044

RESUMO

A simple anion metathesis in diluted aqueous carbonate at room temperature affords 1-(12-mercaptododecyl)-3-methyl-imidazolium carbonate (MDMI-HCO(3)) from MDMI salts self-assembled on gold films and nanoparticles. The properties of MDMI-SAM differ from MDMI in solution, for which the anion exchange reaction does not proceed.


Assuntos
Resinas de Troca Aniônica/química , Carbonatos/química , Ouro/química , Líquidos Iônicos/química , Imidazóis/química , Nanopartículas/química , Espectrofotometria Infravermelho , Análise Espectral Raman , Propriedades de Superfície , Temperatura
15.
Phys Chem Chem Phys ; 13(25): 12015-23, 2011 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-21625701

RESUMO

The properties of a surface modified with an ionic liquid self-assembled monolayer (IL-SAM) can be tuned by simply changing the deposition temperature. Mid-IR, SERS, and molecular modelling demonstrated that 1-(12-mercaptododecyl)-3-methylimidazolium bromide (MDMIBr) exhibited a crystalline monolayer for deposition temperatures below 25 °C. Above 25 °C, the aliphatic chain collapsed into a disordered conformation. At 40 °C, another phase transition occurs due to the imidazolium group tilting parallel to the surface. Consequently, the wettability of IL-SAM was tuned over a broad range of contact angle (from 20° to nearly 40°) by varying the deposition temperature. Permeation of redox mediators to a Au electrode coated with MDMIBr strongly depends on the net charge of the redox mediator. Electron transfer was excellent for neutral and negatively charged redox mediators on electrodes coated with IL-SAM regardless of deposition temperature.

16.
J Am Chem Soc ; 131(30): 10711-8, 2009 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-19580316

RESUMO

A new methodology for the asymmetric synthesis of quaternary alpha-substituted amino acids using memory of chirality has been developed. The strategy utilizes the dynamic axial chirality of tertiary aromatic amides to memorize the initial chirality of an alpha-amino acid during an enolization step. Starting from five different l-amino acids, the corresponding oxazolidin-5-ones containing a tertiary aromatic amide group have been synthesized in one step and then alkylated with various electrophiles, with good yields and enantioselectivities (up to 96% and up to >99% after recrystallization). One-step deprotection affords enantioenriched or enantiopure quaternary alpha-amino acids. We describe here the optimization process, the results obtained in each series and a plausible explanation, based on NMR studies, DFT calculations and crystallographic structures. The methodology presented herein constitutes an efficient synthesis of enantiopure quaternary alpha-amino acids (three steps only) starting from tertiary l-amino acids, without any external source of chirality.


Assuntos
Amidas/química , Aminoácidos/química , Aminoácidos/síntese química , Alquilação , Modelos Moleculares , Conformação Molecular , Estereoisomerismo , Especificidade por Substrato
17.
J Am Chem Soc ; 130(18): 5864-5, 2008 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-18410101

RESUMO

A new methodology for the asymmetric synthesis of quaternary alpha-substituted amino acids using memory of chirality has been developed. This strategy employs dynamic axial chirality of tertiary aromatic amides to memorize the initial chirality of an alpha-amino acid during the enolization step. Starting from L-valine, an oxazolidin-5-one containing a tertiary aromatic amide was synthesized in one step and then alkylated with various electrophiles with good yield and enantioselectivity (up to 96%). Quaternary products can be obtained enantiomerically pure by recrystallization. One-step deprotection affords enantioenriched (S)-alpha-methyl valine (ee = 94%) or enantiopure (S)-alpha-isopropyl aspartic acid (ee >99%) in only three steps starting from L-valine.


Assuntos
Amidas/química , Aminoácidos/síntese química , Valina/análogos & derivados , Alquilação , Ácido Aspártico/análogos & derivados , Ácido Aspártico/síntese química , Ácido Aspártico/química , Espectroscopia de Ressonância Magnética , Conformação Molecular , Oxazolidinonas/química , Estereoisomerismo , Valina/síntese química , Valina/química
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