Synthesis of Graphene-like Films by Electrochemical Reduction of Polyhalogenated Aromatic Compounds and their Electrochemical Capacitor Applications

Electrosynthetic C-F bond cleavage

Fluorinated organic compounds are common among pharmaceuticals, agrochemicals and materials. The significant strength of the C-F bond results in chemical inertness that, depending on the context, is beneficial, problematic or simply a formidable synthetic challenge. Electrosynthesis is a rapidly expanding methodology that can enable new reactivity and selectivity for cleavage and formation of chemical bonds. Here, a comprehensive overview of synthetically relevant electrochemically driven protocols for C-F bond activation and functionalization is presented, including photoelectrochemical strategies.

On the Dynamics of the Carbon-Bromine Bond Dissociation in the 1-Bromo-2-Methylnaphthalene Radical Anion

This paper studies the mechanism of electrochemically induced carbon-bromine dissociation in 1-Br-2-methylnaphalene in the reduction regime. In particular, the bond dissociation of the relevant radical anion is disassembled at a molecular level, exploiting quantum mechanical calculations including steady-state, equilibrium and dissociation dynamics via dynamic reaction coordinate (DRC) calculations. DRC is a molecular-dynamic-based calculation relying on an ab initio potential surface. This is to achieve a detailed picture of the dissociation process in an elementary molecular detail. From a thermodynamic point of view, all the reaction paths examined are energetically feasible. The obtained results suggest that the carbon halogen bond dissociates following the first electron uptake follow a stepwise mechanism. Indeed, the formation of the bromide anion and an organic radical occurs. The latter reacts to form a binaphthalene intrinsically chiral dimer. This paper is respectfully dedicated to Professors Anny Jutand and Christian Amatore for their outstanding contribution in the field of electrochemical catalysis and electrosynthesis.

Hexachlorobenzene-negative ion formation in electron attachment experiments

In this contribution, we report a comprehensive study on the formation of hexachlorobenzene (C₆Cl₆) negative ions probed by low-energy electron interactions from 0 up to 12 eV in a gas-phase crossed beam experiment. The anionic yields as a function of the electron energy reveal a rich fragmentation pattern of the dissociative electron attachment process, yet the most intense ion has been assigned to the non-dissociated parent anion that survives long enough within the detection time window. Other less intense fragment anions have been assigned as Cl^-, Cl₂^-, C₆Cl₄^-, and C₆Cl₅^-. The experimental results are accompanied by quantum chemical calculations at various levels of accuracy, providing an insight into the electronic structure, thermochemical thresholds, electron affinities and structures of neutral and anionic molecular species. The electron attachment process induces a considerable geometry change in the temporary-negative ion relative to the neutral molecule, where the most intense fragment anion assigned to Cl^- can be formed solely through a curve crossing involving a π*/σ* coupling. The yield of chlorine anions shows a signature of vibrational excitation reminiscent of a Jahn-Teller distortion.

Dissociative electron attachment to hexachlorobenzene

Gas phase molecules of hexachlorobenzene (C 6 Cl 6 ) were investigated by means of Dissociative Electron Attachment Spectroscopy (DEAS). Three channels of molecular negative ions decay have been recorded: Cl- and Cl 2 - as well as electron detachment (t a ~250 ms at 343 K). All of these decay channels exhibit temperature dependence. The electron affinity was estimated within the framework of the simple Arrhenius model (EA=1.6-1.9 eV), as well as quantum-chemically at various levels (EA a =0.9-1.0 eV). The reasons for the discrepancy between the obtained estimates of the EA value and the results of previous works (EA from 1 to 2 eV) are discussed.

Production of novel carbon nanostructures by electrochemical reduction of polychlorinated organic rings under mild conditions for supercapacitors

Here, new carbon-based nanostructures were prepared via a one-step electrochemical method using hexagonal and pentagonal polychlorinated organic rings as the carbon source.

Dissociative Electron Attachment to 2,3,6,7,10,11-Hexabromotriphenylene

2,3,6,7,10,11-Hexabromotriphenylene (HBTP) and 2,3,6,7,10-pentabromotriphenylene (PBTP) were investigated by means of dissociative electron attachment spectroscopy (DEAS). The dominant decay channel of the transient molecular negative ions consists of elimination of Br^- with resonances in the low electron energy region. Formation of long-lived parent anions with autodetachment lifetime τ_a = 310 μs is observed at thermal electron energies. The adiabatic electron affinities, EA_a = 1.12 ± 0.1 eV in HBTP and 1.09 ± 0.1 eV in PBTP, evaluated using a simple Arrhenius approach are in good agreement with those predicted by DFT (XYG3/Def2-TZVPP//PBE0/Def2-TZVPP) calculations.