Paper
Organic & Biomolecular Chemistry
supporting electrolyte. The tetrabutylammonium trichloroace-
tate was prepared in dry methanol in a Schlenck tube by
Acknowledgements
mixing stoichiometric amounts of trichloroacetic acid (99%) D.P.V. and P.D.A.S. acknowledge Conacyt for a PhD grant. The
and tetrabutylammonium hydroxide 1 M–methanol. The water authors acknowledge B.R. Díaz and L.S. Hernández for their
produced in this reaction was eliminated under vacuum as a assistance with the acquisition of the NMR and ESR spectra.
water–methanol azeotrope.
The authors acknowledge CONACyT for financial support
through the project 103714.
Electrochemical instrumentation and electrodes
The electrochemical apparatus consisted in a potentiostat
DEA-332 (Radiometer Copenhagen) with positive feedback Notes and references
resistance compensation. A conventional three electrode cell
1 (a) Y. Matsumura, Encyclopedia of Electrochemistry, Wiley-
was used to carry out the voltammetric experiments. The
working electrode was a 1 mm diameter platinum disk, which
was polished with 0.3 μm alumina powder and ultrasonically
rinsed with distilled water and ethanol before each experimen-
tal run. The auxiliary electrode was a platinum mesh and the
reference electrode a Saturated Calomel Electrode (SCE). A salt
VCH, 2007, ch. 6, vol. 8003B; (b) H. J. Shaefer, Top. Curr.
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and B. E. Conway, Chem. Rev., 1967, 67, 623; (e) S. Torii and
H. Tanaka, Organic Electrochemistry, Marcel Dekker,
New York, 2001, ch. 14.
+
bridge containing 0.1 M n-Bu4NPF6 acetonitrile solution con-
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nected the cell with the reference electrode. All the electroche-
mical experiments were performed at room temperature
(∼25 °C).
Spectroscopic instrumentation
1H and 13C NMR spectra were recorded on a JEOL EKA-500
spectrometer. X-band ESR spectra were collected using an
EMX Plus Bruker System and by using a Wilmad cell. The
samples were prepared under an argon atmosphere, in deuter-
ated acetonitrile. In all the cases, the experiments were per-
formed at room temperature.
Computational details
All the electronic calculations were performed with the Gaus-
sian 09 package of programs.13 Geometry optimizations and
frequency calculations were carried out using the M05-2X func-
tional14 and the 6-311++G(d,p) basis set. They have been
carried out in solution, using the SMD continuum model15
and acetonitrile as the solvent. The M05-2X functional has
been chosen for the task at hand because it has been proven
to be among the functionals with the best performance for
general purpose applications in thermochemistry, kinetics,
and noncovalent interactions involving nonmetals.12 It is also
among the best performing functionals for calculating reaction
energies involving free radicals.16 The SMD solvent model has
been chosen since its performance for describing solvation in
energies of both neutral and ionic species, in aqueous and
also in non-aqueous solvents, is better than that achieved with
other solvent models. Geometries were fully optimized without
imposing any restriction. Local minima were confirmed by the
absence of imaginary frequencies. Thermodynamic corrections
at 298.15 K were included in the calculation of relative ener- 10 (a) M. Galicia and F. J. González, J. Electrochem. Soc., 2002,
gies. The Bader topological analyses12 of the wave functions
were performed with the AIM2000 code.17
149, 46; (b) M. Galicia, M. A. González-Fuentes,
D. P. Valencia and F. J. González, J. Electroanal. Chem.,
324 | Org. Biomol. Chem., 2013, 11, 318–325
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