Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 17 de 17
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Dalton Trans ; 51(41): 15716-15724, 2022 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-36177940

RESUMO

Solar conversion of water into the storable energy carrier H2 can be achieved through photoelectrochemical water splitting using light adsorbing anodes and cathodes bearing O2 and H2 evolving catalysts, respectively. Herein a novel photocathode nanohybrid system is reported. This photocathode consists of a dye-sensitized p-type nickel oxide (NiO) with a perylene-based chromophore (PCA) and a tetra-adamantane modified cobaloxime reduction catalyst (Co) that photo-reduces aqueous protons to H2. An original supramolecular approach was employed, using ß-cyclodextrin functionalized gold nanoparticles (ß-CD-AuNPs) to link the alkane chain of the PCA dye to the adamantane moieties of the cobaloxime catalyst (Co). This new architecture was investigated by photoelectrochemical measurements and via femtosecond-transient absorption spectroscopy. The results show that irradiation of the complete NiO|PCA|ß-CD-AuNPs|Co electrode leads to ultrafast hole injection into NiO (π = 3 ps) from the excited dye, followed by rapid reduction of the catalyst, and finally H2 evolution.

2.
ACS Appl Mater Interfaces ; 12(4): 4501-4509, 2020 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-31872996

RESUMO

A facile surface amide-coupling method was examined to attach dye and catalyst molecules to silatrane-decorated NiO electrodes. Using this method, electrodes with a push-pull dye were assembled and characterized by photoelectrochemistry and transient absorption spectroscopy. The dye-sensitized electrodes exhibited hole injection into NiO and good photoelectrochemical stability in water, highlighting the stability of the silatrane anchoring group and the amide linkage. The amide-coupling protocol was further applied to electrodes that contain a molecular proton reduction catalyst for use in photocathode architectures. Evidence for catalyst reduction was observed during photoelectrochemical measurements and via femtosecond-transient absorption spectroscopy demonstrating the possibility for application in photocathodes.

3.
Inorg Chem ; 58(4): 2761-2769, 2019 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-30724559

RESUMO

The chemistry of Fe2(µ-SH)2(CO)4(PPh3)2 (2HH) is described with attention to S-S coupling reactions. Produced by the reduction of Fe2(µ-S2)(CO)4(PPh3)2 (2), 2HH is an analogue of Fe2(µ-SH)2(CO)6 (1HH), which exhibits well-behaved S-centered redox. Both 2HH and the related 2MeH exist as isomers that differ with respect to the stereochemistry of the µ-SR ligands (R = H, Me). Compounds 2HH, 2MeH, and 2 protonate to give rare examples of Fe-SH and Fe-S2 hydrides. Salts of [H2]+, [H2HH]+, and [H2MeH]+ were characterized crystallographically. Complex 2HH reduces O2, H2O2, (PhCO2)2, and Ph2N2, giving 2. Related reactions involving 1HH gave uncharacterizable polymers. The differing behaviors of 2HH and 1HH reflect stabilization of the ferrous intermediates by the PPh3 ligands. When independently generated by the reaction of 2HH with 2,2,6,6-tetramethyl-1-piperidinyloxy, 2* quantitatively converts to 2 or, in the presence of C2H4, is trapped as the ethanedithiolate Fe2(µ-S2C2H4)(CO)4(PPh3)2. Evidence is presented that the Hieber-Gruber synthesis of 1 involves polysulfido intermediates [Fe2(µ-S n)2(CO)6]2- ( n > 1). Two relevant experiments are as follows: (i) protonation of [Fe4(µ-S)2(µ-S2)CO)12]2- gives 1 and 1HH, and (ii) oxidation of 1HH by sulfur gives 1.

4.
Inorg Chem ; 58(4): 2430-2443, 2019 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-30707014

RESUMO

Described are the syntheses of several Ni(µ-SR)2Fe complexes, including hydride derivatives, in a search for improved models for the active site of [NiFe]-hydrogenases. The nickel(II) precursors include (i) nickel with tripodal ligands: Ni(PS3)- and Ni(NS3)- (PS33- = tris(phenyl-2-thiolato)phosphine, NS33- = tris(benzyl-2-thiolato)amine), (ii) traditional diphosphine-dithiolates, including chiral diphosphine R,R-DIPAMP, (iii) cationic Ni(phosphine-imine/amine) complexes, and (iv) organonickel precursors Ni( o-tolyl)Cl(tmeda) and Ni(C6F5)2. The following new nickel precursor complexes were characterized: PPh4[Ni(NS3)] and the dimeric imino/amino-phosphine complexes [NiCl2(PCH═NAn)]2 and [NiCl2(PCH2NHAn)]2 (P = Ph2PC6H4-2-). The iron(II) reagents include [CpFe(CO)2(thf)]BF4, [Cp*Fe(CO)(MeCN)2]BF4, FeI2(CO)4, FeCl2(diphos)(CO)2, and Fe(pdt)(CO)2(diphos) (diphos = chelating diphosphines). Reactions of the nickel and iron complexes gave the following new Ni-Fe compounds: Cp*Fe(CO)Ni(NS3), [Cp(CO)Fe(µ-pdt)Ni(dppbz)]BF4, [( R,R-DIPAMP)Ni(µ-pdt)(H)Fe(CO)3]BArF4, [(PCH═NAn)Ni(µ-pdt)(Cl)Fe(dppbz)(CO)]BF4, [(PCH2NHAn)Ni(µ-pdt)(Cl)Fe(dppbz)(CO)]BF4, [(PCH═NAn)Ni(µ-pdt)(H)Fe(dppbz)(CO)]BF4, [(dppv)(CO)Fe(µ-pdt)]2Ni, {H[(dppv)(CO)Fe(µ-pdt)]2Ni]}BF4, and (C6F5)2Ni(µ-pdt)Fe(CO)2(dppv) (DIPAMP = (CH2P(C6H4-2-OMe)2)2; BArF4- = [B(C6H3-3,5-(CF3)2]4-)) Within the context of Ni-(SR)2-Fe complexes, these new complexes feature new microenvironments for the nickel center: tetrahedral Ni, chirality, imine, and amine coligands, and Ni-C bonds. In the case of {H[(dppv)(CO)Fe(µ-pdt)]2Ni}+, four low-energy isomers are separated by ≤3 kcal/mol, one of which features a biomimetic HNi(SR)4 site, as supported by density functional theory calculations.

5.
Inorg Chem ; 57(8): 4409-4418, 2018 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-29620876

RESUMO

The synthesis and redox properties are presented for the electron-rich bis(monothiolate)s Fe2(SR)2(CO)2(dppv)2 for R = Me ([1]0), Ph ([2]0), CH2Ph ([3]0). Whereas related derivatives adopt C2-symmetric Fe2(CO)2P4 cores, [1]0-[3]0 have Cs symmetry resulting from the unsymmetrical steric properties of the axial vs equatorial R groups. Complexes [1]0-[3]0 undergo 1e- oxidation upon treatment with ferrocenium salts to give the mixed valence cations [Fe2(SR)2(CO)2(dppv)2]+. As established crystallographically, [3]+ adopts a rotated structure, characteristic of related mixed valence diiron complexes. Unlike [1]+ and [2]+ and many other [Fe2(SR)2L6]+ derivatives, [3]+ undergoes C-S bond homolysis, affording the diferrous sulfido-thiolate [Fe2(SCH2Ph)(S)(CO)2(dppv)2]+ ([4]+). According to X-ray crystallography, the first coordination spheres of [3]+ and [4]+ are similar, but the Fe-sulfido bonds are short in [4]+. The conversion of [3]+ to [4]+ follows first-order kinetics, with k = 2.3 × 10-6 s-1 (30 °C). When the conversion is conducted in THF, the organic products are toluene and dibenzyl. In the presence of TEMPO, the conversion of [3]+ to [4]+ is accelerated about 10×, the main organic product being TEMPO-CH2Ph. DFT calculations predict that the homolysis of a C-S bond is exergonic for [Fe2(SCH2Ph)2(CO)2(PR3)4]+ but endergonic for the neutral complex as well as less substituted cations. The unsaturated character of [4]+ is indicated by its double carbonylation to give [Fe2(SCH2Ph)(S)(CO)4(dppv)2]+ ([5]+), which adopts a bioctahedral structure.

6.
Organometallics ; 36(11): 2054-2057, 2017 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-28781407

RESUMO

The azadithiolate complex Fe2[(SCH2)26NMe](CO)6 reacts with borane to give an initial 1:1 adduct, which spontaneously decarbonylates to give Fe2[(SCH2)2NMeBH3](CO)5. Featuring a Fe-H-B three-center, two-electron interaction, the pentacarbonyl complex is a structural model for H2 complexes invoked in the [FeFe]-hydrogenases. The pentacarbonyl compound is a "σ complex", where a B-H σ bond serves as a ligand for iron. The structure of this σ complex was characterized by variable-temperature NMR spectroscopy and X-ray crystallography. Complementary to the 1:1 borane adduct is the quaternary ammonium complex [Fe2](SCH2)2NMe2](CO)6]+, which was also characterized. It represents a kinetically robust analogue of the N-protonated amine cofactor, as indicated by its mild reduction potential.

7.
Angew Chem Int Ed Engl ; 56(7): 1845-1849, 2017 02 06.
Artigo em Inglês | MEDLINE | ID: mdl-28078719

RESUMO

A biomimetic nickel bis-diphosphine complex incorporating the amino acid arginine in the outer coordination sphere was immobilized on modified carbon nanotubes (CNTs) through electrostatic interactions. The functionalized redox nanomaterial exhibits reversible electrocatalytic activity for the H2 /2 H+ interconversion from pH 0 to 9, with catalytic preference for H2 oxidation at all pH values. The high activity of the complex over a wide pH range allows us to integrate this bio-inspired nanomaterial either in an enzymatic fuel cell together with a multicopper oxidase at the cathode, or in a proton exchange membrane fuel cell (PEMFC) using Pt/C at the cathode. The Ni-based PEMFC reaches 14 mW cm-2 , only six-times-less as compared to full-Pt conventional PEMFC. The Pt-free enzyme-based fuel cell delivers ≈2 mW cm-2 , a new efficiency record for a hydrogen biofuel cell with base metal catalysts.

8.
Chemistry ; 22(30): 10494-500, 2016 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-27328033

RESUMO

We report the controlled orientation of bilirubin oxidases (BOD) from Myrothecium verrucaria on multiwalled carbon nanotubes (MWCNTs) functionalised by electrografting of 6-carboxynaphthalenediazonium and 4-(2-aminoethyl)benzenediazonium salts. On negatively charged naphthoate-modified MWCNTs, a high-potential (0.44 V vs. SCE) oxygen reduction electrocatalysis is observed, occurring via the T1 copper centre. On positively charged ammonium-modified MWCNTs, a low-potential (0.15 V) oxygen reduction electrocatalysis is observed, occurring through a partially oxidised state of the T2/T3 trinuclear copper cluster. Finally, chemically modified naphthoate MWCNTs exhibit high bioelectrocatalytic current densities of 3.9 mA cm(-2) under air at gas-diffusion electrode.


Assuntos
Compostos de Diazônio/química , Nanotubos de Carbono/química , Oxirredutases/química , Oxigênio/química , Catálise , Difusão , Técnicas Eletroquímicas , Eletrodos , Elétrons , Hypocreales/enzimologia , Conformação Molecular , Oxirredução , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/química , Propriedades de Superfície
9.
Chemistry ; 21(47): 16868-73, 2015 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-26449635

RESUMO

The efficient immobilization and orientation of bilirubin oxidase from Myrothecium verrucaria on multi-walled carbon nanotube electrodes by using π-stacked porphyrins as a direct electron-transfer promoter is reported. By comparing the use of different types of porphyrin, the rational effect of the porphyrin structure on both the immobilization and orientation of the enzyme is demonstrated. The best performances were obtained for protoporphyrin IX, which is the natural precursor of bilirubin. These electrodes exhibit full orientation of the enzyme, as confirmed by the observable non-catalytic redox system corresponding to the T1 copper center associated with pure Nernstian electrocatalytic behavior with high catalytic currents of almost 5 mA cm(-2) at neutral pH.


Assuntos
Cobre/química , Enzimas Imobilizadas/química , Nanotubos de Carbono/química , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/química , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/metabolismo , Porfirinas/química , Biocatálise , Eletrodos , Transporte de Elétrons , Concentração de Íons de Hidrogênio , Oxirredução
10.
Bioelectrochemistry ; 106(Pt A): 73-6, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25934467

RESUMO

This study reports a mixed operational/storage stability of a MWCNT-based glucose biofuel cell (GBFC) over one year. The latter was examined by performing a one hour discharge every day during one month followed by several discharges over a period of 11 months. Under continuous discharge in physiological conditions (5 mM glucose, 37°, pH7), the GBFC exhibits a 25% power decrease after 1 h of operation. This decrease is mainly due to the deactivation of laccase biocathodes at neutral pH. Nevertheless, the biocathodes can be reversibly reactivated via storage in phosphate buffer (pH 5). Under these conditions, the GBFC finally exhibits 22% of its initial maximum power density after one year at intermittent reactivation/discharge cycles. Although both GBFC electrodes can exhibit one year stability, short-term experiments show that biocathodes are limited by hydroxide inhibition while long-term experiments indicate that bioanodes are likely limited by the stability of the GOx itself. While most of the GBFCs in the literature present stability in the range of several weeks, these results demonstrate the viability of a GBFC for industrial applications in a long period of time.


Assuntos
Fontes de Energia Bioelétrica , Glucose/química , Lacase/metabolismo , Nanotubos de Carbono/química , Oxigênio/química , Animais , Bovinos , Eletrodos , Ativação Enzimática , Concentração de Íons de Hidrogênio
11.
Chem Commun (Camb) ; 51(35): 7447-50, 2015 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-25845356

RESUMO

A biocathode was designed by the modification of a carbon nanotube (CNT) gas-diffusion electrode with bilirubin oxidase from Bacillus pumilus, achieving high current densities up to 3 mA cm(-2) for the reduction of O2 from air. A membraneless air-breathing hydrogen biofuel cell was designed by combination of this cathode with a functionalized CNT-based hydrogenase anode.


Assuntos
Fontes de Energia Bioelétrica , Hidrogenase/metabolismo , Nanotubos de Carbono/química , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/metabolismo , Ar , Bacillus/enzimologia , Eletrodos , Enzimas Imobilizadas/química , Enzimas Imobilizadas/metabolismo , Hidrogênio/química , Hidrogênio/metabolismo , Hidrogenase/química , Nanotubos de Carbono/ultraestrutura , Oxirredução , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/química , Oxigênio/química , Oxigênio/metabolismo
12.
Chemistry ; 21(8): 3198-201, 2015 Feb 16.
Artigo em Inglês | MEDLINE | ID: mdl-25504469

RESUMO

Reduced graphene oxide (RGO) was covalently functionalized by the in situ generation and reduction of anthraquinone diazonium salt. Deposition on multi-wall carbon nanotube (MWCNT) electrodes prevents the aggregation of RGO nanosheets and allows the stable deposition of modified graphene, accompanied with excellent electron transfer properties. Laccases were immobilized on the nanostructured electrode by the interaction between the anthraquinone moiety and the laccase hydrophobic pocket located near the T1 copper center. The MWCNT/f-RGO electrode exhibits efficient bioelectrocatalytic oxygen reduction, with current densities of up to 0.9 mA cm(-2) .


Assuntos
Antraquinonas/química , Grafite/química , Lacase/química , Nanotubos de Carbono/química , Oxigênio/química , Fontes de Energia Bioelétrica , Catálise , Eletroquímica , Transporte de Elétrons , Lacase/metabolismo , Oxirredução
13.
Chemistry ; 20(10): 2953-9, 2014 Mar 03.
Artigo em Inglês | MEDLINE | ID: mdl-24519626

RESUMO

A series of redox-labeled L-tyrosinamide (L-Tym) derivatives was prepared and the nature of the functional group and the chain length of the spacer were systematically varied in a step-by-step affinity optimization process of the tracer for the L-Tym aptamer. The choice of the labeling position on L-Tym proved to be crucial for the molecular recognition event, which could be monitored by cyclic voltammetry and is based on the different diffusion rates of free and bound targets in solution. From this screening approach an efficient electroactive tracer emerged. Comparable dissociation constants Kd were obtained for the unlabeled and labeled targets in direct or competitive binding assays. The enantiomeric tracer was prepared and its enantioselective recognition by the corresponding anti-D-Tym aptamer was demonstrated. The access to both enantiomeric tracer molecules opens the door for the development of one-pot determination of the enantiomeric excess when using different labels with well-separated redox potentials for each enantiomer.


Assuntos
Aptâmeros de Nucleotídeos/química , Oligonucleotídeos/química , Tirosina/análogos & derivados , Ligação Competitiva , Difusão , Eletroquímica , Eletroforese Capilar , Oxirredução , Estereoisomerismo , Tirosina/química
14.
Chem Commun (Camb) ; 49(81): 9281-3, 2013 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-23994955

RESUMO

We report the functionalization of multi-walled carbon nanotube (MWCNT) electrodes by oxidative electropolymerization of pyrrole monomers bearing pyrene and N-hydroxysuccinimide groups. Both polymers were applied to the immobilization and electrical wiring of Trametes versicolor laccase via chemical grafting or non-covalent binding. A "pseudo" host-guest interaction of polymerized pyrene with a hydrophobic cavity of laccase was used for the oriented enzyme immobilization on MWCNT electrodes. The latter leads to higher catalytic current for oxygen reduction (1.85 mA cm(-2)) and higher electroenzymatic stability (50% after one month).


Assuntos
Lacase/metabolismo , Nanotubos de Carbono/química , Oxigênio/metabolismo , Polímeros/química , Pirenos/química , Pirróis/química , Biocatálise , Eletrodos , Enzimas Imobilizadas/química , Enzimas Imobilizadas/metabolismo , Lacase/química , Oxirredução , Trametes/enzimologia
15.
Chemistry ; 19(28): 9371-5, 2013 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-23740491

RESUMO

An efficient way of immobilizing and wiring a large amount of laccase on non-covalently-functionalized multi-walled carbon nanotube (MWCNT) electrodes is reported. 1-(2-anthraquinonylaminomethyl)pyrene and 1-[bis(2-anthraquinonyl)aminomethyl]pyrene were synthesized and studied for their capability to non-covalently functionalize MWCNT electrodes and immobilize and orientate laccase on the nanostructured electrodes. This led to high-performance biocathodes for oxygen reduction by direct electron transfer with maximum current densities of (1±0.2) mA cm(-2). The performance of the resulting bioelectrodes could be doubled simply by using the bis-anthraquinone compound. The bioelectrodes show excellent stability over weeks and can thus be envisioned in enzymatic biofuel cells.


Assuntos
Antraquinonas/síntese química , Enzimas Imobilizadas/química , Lacase/química , Nanotubos de Carbono/química , Oxigênio/química , Pirenos/síntese química , Antraquinonas/química , Fontes de Energia Bioelétrica , Eletrodos , Transporte de Elétrons , Elétrons , Pirenos/química
16.
Org Biomol Chem ; 10(38): 7780-8, 2012 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-22911002

RESUMO

The influence of anions on tautomerism in benzimidazole containing anion receptors has been studied via a variety of techniques in both solution and the solid state. The results show that hydrogen bonding interactions between the receptors and guests have a significant effect of the nature of the tautomer present. The compounds show a preference for complexation of lactate over pyruvate.


Assuntos
Benzimidazóis/química , Indóis/síntese química , Ácido Láctico/química , Ácido Pirúvico/química , Ureia/síntese química , Ânions/química , Cristalografia por Raios X , Ligação de Hidrogênio , Indóis/química , Modelos Moleculares , Estrutura Molecular , Ureia/análogos & derivados , Ureia/química
17.
Org Biomol Chem ; 10(30): 5909-15, 2012 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-22218531

RESUMO

Tautomeric switching is observed in a series of benzimidazole-based anion receptors upon addition of basic anions. An N-methylbenzimidazole based receptor selectively interacts with dihydrogen phosphate over a variety of other putative anionic guests via a combination of donated and accepted hydrogen bonds.


Assuntos
Benzimidazóis/química , Ligação de Hidrogênio , Isomerismo , Modelos Moleculares , Conformação Molecular , Fosfatos/química , Especificidade por Substrato
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...