Search results for "Electron transfer"
showing 10 items of 282 documents
Electron delocalization in mixed-valence Keggin polyoxometalates. Ab initio calculation of the local effective transfer integrals and its consequence…
2002
We present a quantitative evaluation of the influence of the electron transfer on the magnetic properties of mixed-valence polyoxometalates reduced by two electrons. For that purpose, we extract from valence-spectroscopy ab initio calculations on embedded fragments the value of the transfer integrals between W nearest-neighbor atoms in a mixed-valence alphaPW(12)O(40) polyoxowolframate Keggin anion. In contradiction with what is usually assumed, we show that the electron transfer between edge-sharing and corner-sharing WO(6) octahedra have very close values. Considering fragments of various ranges, we analyze the accuracy of calculations on fragments based on only two WO(5) pyramids which s…
The effect of N-tetradecyl-N,N-dimethylamine oxide micelles on the kinetics of the electron transfer reaction of Ce(IV) with substituted malonic acids
2009
Abstract The kinetics of the oxidation of malonic acid and (its substituted compounds, methyl-, ethyl-, butyl- and benzyl-malonic acid) by ceric ions has been studied at 20.0 °C in the absence and the presence of the surfactant N-tetradecyl-N,N-dimethylamine oxide (C 14 DMAO). The addition of increasing amounts of C 14 DMAO influences the rate of the redox process to an extent that significantly depends on the hydrophobicity of the reducing species. The reactivity data together with the estimated binding constants and the standard transfer free energies of the malonic acids from water to the micelles suggest that the malonic acid is confined to the aqueous pseudo-phase while for the other s…
Interspecies interactions mediated by conductive minerals in the sediments of the ferruginous Lake La Cruz, Spain
2018
AbstractLake La Cruz is considered a biogeochemical analogue to early Earth marine environments because its water column is depleted in sulfate, but rich in methane and iron, similar to conditions envisaged for much of the Precambrian. In this early Earth analogue environment, we show that conductive particles establish a tight metabolic coupling between electroactive microbial clades. We propose that mineral-based syntrophy is of potential relevance for the evolution of Earth’s earliest complex life forms. We show that the anoxic sediment of Lake La Cruz, which is rich in biogeochemically ‘reactive’ iron minerals, harbors known electroactive species such asGeobacterandMethanothrix,in addit…
Electronic aspects of the hydride transfer mechanism. Ab initio analytical gradient studies of the cyclopropenyl‐cation/lithium hydride model reactan…
1985
The electronic mechanisms of a model hydride transfer reaction are theoretically studied with ab inito RHF and UHF SCF MO procedures at the 4‐31G basis set level and analytical gradient methods. The model system describes the reduction of cyclopropenyl cation to cyclopropene by the oxidation of lithium hydride to lithium cation. The molecular fragments corresponding to the asymptotic reactive channels characterizing the stepwise mechanisms currently discussed in the literature have been characterized. The binding energy between the fragments is estimated within a simple electrostatic approximate scheme. The results show that a hydride‐ion mechanism is a likely pathway for this particular sy…
Monofunctional pyrenes at carbon nanotube electrodes for direct electron transfer H2O2 reduction with HRP and HRP-bacterial nanocellulose
2021
Abstract The non-covalent modification of carbon nanotube electrodes with pyrene derivatives is a versatile approach to enhance the electrical wiring of enzymes for biosensors and biofuel cells. We report here a comparative study of five pyrene derivatives adsorbed at multi-walled carbon nanotube electrodes to shed light on their ability to promote direct electron transfer with horseradish peroxidase (HRP) for H2O2 reduction. In all cases, pyrene-modified electrodes enhanced catalytic reduction compared to the unmodified electrodes. The pyrene N-hydroxysuccinimide (NHS) ester derivative provided access to the highest catalytic current of 1.4 mA cm−2 at 6 mmol L−1 H2O2, high onset potential …
Magnetoelectrochemistry of 4,4′-bis(dimethylamino)biphenyl and 4,4′-dinitrobiphenyl azacrown macrocyclic lactams
2005
Abstract The voltammetric behaviour at carbon fibre microelectrodes under the application of static magnetic fields of two series of macrolactams containing in their structure 4,4′-bis(dimethylamino)biphenyl or 4,4′-dinitrobiphenyl groups in MeCN solution is described. The response of 4,4′-dinitrobiphenyl receptors is dominated by two successive one-electron reduction processes at −0.9 and −1.6 V versus AgCl/Ag. 4,4′-bis(dimethylamino)biphenyl-containing receptors display two one-electron oxidations above +0.8 and +1.0 V. In both cases, a dihedral/planar interconversion precedes the second electron transfer step. Upon application of moderate (0.05–0.2 T) static magnetic fields to the electr…
Synthesis and Photodynamics of Fluorescent Blue BODIPY-Porphyrin Tweezers Linked by Triazole Rings
2012
Novel zinc porphyrin tweezers in which two zinc porphyrins were connected with π-conjugated boron dipyrromethenes (BDP meso-Por(2) and BDP β-Por(2)) through triazole rings were synthesized to investigate the photoinduced energy transfer and electron transfer. The UV-vis spectrum of BDP β-Por(2) which has less bulky substituents than BDP meso-Por(2) exhibits splitting of the Soret band as a result of the interaction between porphyrins of BDP β-Por(2) in the excited state. Such interaction between porphyrins of both BDP β-Por(2) and BDP meso-Por(2) is dominant at room temperature, while the coordination of the nitrogen atoms of the triazole rings to the zinc ions of the porphyrins occurs at l…
Molecular Basis of the Chemiluminescence Mechanism of Luminol
2019
Light emission from luminol is probably one of the most popular chemiluminescence reactions due to its use in forensic science, and has recently displayed promising applications for the treatment of cancer in deep tissues. The mechanism is, however, very complex and distinct possibilities have been proposed. By efficiently combining DFT and CASPT2 methodologies, the chemiluminescence mechanism has been studied in three steps: 1)luminol oxygenation to generate the chemiluminophore, 2)a chemiexcitation step, and 3)generation of the light emitter. The findings demonstrate that the luminol double-deprotonated dianion activates molecular oxygen, diazaquinone is not formed, and the chemiluminopho…
Rate Theory for Electrocatalytic Systems: Fixed Potential Formulation for General, Electron Transfer, and Proton-Coupled Electron Transfer Reactions
2019
Atomistic modeling of electrocatalytic reactions is most naturally conducted within the grand canonical ensemble (GCE) which enables fixed chemical potential calculations. While GCE has been widely adopted for modeling electrochemical and electrocatalytic thermodynamics, the electrochemical reaction rate theory within GCE is lacking. Molecular and condensed phase rate theories are formulated within microcanonical and canonical ensembles, respectively, but electrocatalytic systems described within the GCE require extension of the conventionally used rate theories for computation reaction rates at fixed electrode potentials. In this work, rate theories from (micro) canonical ensemble are gene…
Unified Rate Theory of Electrochemistry and Electrocatalysis: Fixed Potential Formulation for General, Electron Transfer, and Proton-Coupled Electron…
2019
Atomistic modeling of electrocatalytic reactions is most naturally conducted within the grand canonical ensemble (GCE) which enables fixed chemical potential calculations. While GCE has been widely adopted for modeling electrochemical and electrocatalytic thermodynamics, the electrochemical reaction rate theory within GCE is lacking. Molecular and condensed phase rate theories are formulated within microcanonical and canonical ensembles, respectively, but electrocatalytic systems described within the GCE require extension of the conventionally used rate theories for computation reaction rates at fixed electrode potentials. In this work, rate theories from (micro)canonical ensemble are gener…