New insight into the electrochemical reduction of different aryldiazonium salts in aqueous solutions

Article abstract of DOI:10.1039/d1ra04482f

Electrochemical reduction of different aryldiazonium salts in aqueous solution was studied in this work and it is shown that the aryldiazonium salts are converted to the corresponding aryl radical and aryl anion. The results of this research indicate that the reduction of aryldiazonium salts takes place in two single-electron steps. Our data show that when the substituted group on the phenyl ring is H, Cl, OH, NO₂, OCH₃or SO₃^?, the corresponding diazonium salt shows poor adsorption characteristics, but when the substituted group is methyl, the corresponding diazonium salt shows strong adsorption characteristics. In the latter case, the voltammogram exhibits three cathodic peaks. In addition, the effect of various substitutions on the aryldiazonium reduction was studied by Hammett's method. The data are show that with increasing electron withdrawing capacity of the substituent, the reduction of corresponding diazonium salt becomes easier.

Full text of DOI:10.1039/d1ra04482f

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New insight into the electrochemical reduction of
different aryldiazonium salts in aqueous solutions
Cite this: RSC Adv., 2021, 11, 25811
Zahra Tavakkoli, Hamed Goljani, Hassan Sepehrmansourie, Davood Nematollahi
*
and Mohammad Ali Zolfigol
Electrochemical reduction of different aryldiazonium salts in aqueous solution was studied in this work and
it is shown that the aryldiazonium salts are converted to the corresponding aryl radical and aryl anion. The
results of this research indicate that the reduction of aryldiazonium salts takes place in two single-electron
3ꢀ
steps. Our data show that when the substituted group on the phenyl ring is H, Cl, OH, NO
2
, OCH
3
or SO
,
the corresponding diazonium salt shows poor adsorption characteristics, but when the substituted group is
methyl, the corresponding diazonium salt shows strong adsorption characteristics. In the latter case, the
voltammogram exhibits three cathodic peaks. In addition, the effect of various substitutions on the
aryldiazonium reduction was studied by Hammett's method. The data are show that with increasing
electron withdrawing capacity of the substituent, the reduction of corresponding diazonium salt
becomes easier.
Received 9th June 2021
Accepted 16th July 2021
DOI: 10.1039/d1ra04482f
rsc.li/rsc-advances
group. Many researchers have worked on the graing of aryl-
diazonium salts on different electrode surfaces, and obtained
Introduction
Diazonium salts are a large group of organic compounds with satisfactory results. Among them we can mention the inter-
+
ꢀ
22–31
32–41
the general formula R–N
2
X , where R can be alkyl or aryl and X esting studies conducted by Pinson
and Downard et al.
1
is an organic or inorganic anion such as a halogen. Diazonium In these published papers, the authors provided valuable
salts are very important chemicals that have been used as information on the electrochemical reduction mechanism of
versatile building blocks for the syntheses of a broad range of aryldiazoniums in acetonitrile. Nevertheless, this study seeks to
organic molecules. These compounds are able to perform two expand the frontiers of knowledge on some electrochemical
types of reactions: nitrogen-removal reactions and nitrogen- properties of aryldiazonium salts in aqueous solutions. There-
2
retention reactions. In the rst type, with the loss of the N
2
fore, in this paper, we want to provide some new information on
molecule, chemical bonds such as C–C, C–X, C–S, C–P and C–P the electrochemical behavior of aryldiazonium salts in water
2–8
are formed. In the second type, the nitrogen atoms remain in and investigate the effect of substituent groups on adsorption
2,5,9,10
the molecule as N]N or N–N bonds.
activity and electrochemical behavior of these compounds. This
The high efficiency and high selectivity of these compounds study will contribute to expand the understanding of electro-
have led to an increase in their use in the synthesis of organic chemical reduction of aryldiazonium salts in aqueous
11,12
compounds.
Despite the large number of published papers solutions.
on the synthesis of organic compounds using diazonium salts,
the electrochemical behavior of these salts has not been well
studied. A literature survey on electrochemical reduction of Results and discussion
diazonium salts show that the goal of most of these studies is
the reduction of the diazonium salts to produce the corre-
Mechanistic studies
Cyclic voltammograms of twelve aryldiazonium hydrogen
sponding radical in order to modify the electrode surface
ꢀ
2 3 3
sulfate salts (ADs) (10 mM) containing H, Cl, NO , OCH , SO ,
13–21
(Scheme 1).
These studies show that the reduction of aryldiazoniums
involves a single-electron transfer from the cathode to the
aryldiazonium salt, resulting in the release of a nitrogen
molecule and the formation of an aryl radical followed by the
bond formation between the electrode surface and the aryl
Faculty of Chemistry, Bu-Ali-Sina University, Hamedan 65174, Iran. E-mail: nemat@
basu.ac.ir
Scheme
grafting of diazonium salts.
1 Modification of electrode surface by electrochemical
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2021 The Author(s). Published by the Royal Society of Chemistry
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OH and CH
3
substituent groups in aqueous solution (H
2
SO
4
, c
ꢂ
¼
1.0 M) at a temperature 4 ꢁ 1 C are shown in Fig. 1. The rst
common feature of these diazonium salts is their irreversibility.
The absence of anodic peak even at high potential scan rates
indicates the high reactivity of the electrode product and its
participation in an irreversible fast chemical reaction. Most of
these compounds (containing Cl, NO
substituent groups) have two cathodic peaks (C
some (containing CH
peaks (C , C and C ).
2
, OCH
3
, SO
3
H, H and OH
and C ) and
1
2
3
substituent group), have three cathodic
0
1
2
To explain this difference, the linear sweep voltammograms
of 2-chlorobenzenediazonium (2ClAD) and 3-methyl-
benzenediazonium (3MeAD) were recorded at a temperature 4
ꢂ
ꢁ
1 C, at different scan rates (Fig. 2). As can be seen, in both
compounds the peak current ratio (IpC2/IpC1) changes with
increasing scan rates. This shows the unequal inuence of the
adsorption process on two single-electron transfer steps. The
examination of 2ClAD voltammograms shows that while at
ꢀ1
a scan rate of 10 mV s , the peak current ratio, IpC2/IpC1 is about
.3 (log IpC2/IpC1 ¼ ꢀ0.52), with the increase of potential scan
0
ꢀ
1
rate to 4000 mV s , the ratio increases sharply to about 2.4
(
log IpC2/IpC1 ¼ 0.38). These results indicate that the adsorption
ability of the product of second electron transfer process is
more than that of the rst electron transfer process. To conrm
1 2
this statement, the dependence of logarithm of the C and C
Fig. 2 Parts I and II: linear sweep voltammograms of 10 mM of 2ClAD.
Parts III and IV: linear sweep voltammograms of 10 mM of 3MeAD in
peak currents (log IpC1 and log IpC2) on the logarithm of poten-
tial scan rate (log n) were examined (Fig. 2, part VI). Under these
conditions, the slope of the line for a pure diffusion controlled
aqueous solution (H
carbon electrode. Scan rates from (a) to (j) are: 10, 25, 50, 100, 250,
2
SO
4
, c ¼ 1 M) in various scan rates at glassy
42
(p. 236)
ꢀ1
process is 0.5,
adsorption process.
This value is higher than the theoretical value of 0.5 and is less
than one, which indicate a partial adsorption for peak C . The
while this value is equal to 1 for a pure 500, 1000, 2000, 3000 and 4000 mV s . Part V: plot of log IpC2/IpC1
42
(p. 591)
values derived from linear sweep voltammograms of 2ClAD (parts I and
II) vs. log v. Part VI: plot of log IpC1 and IpC2 values derived from linear
sweep voltammograms of 2ClAD (parts I and II) vs. log v. Part V, inset:
The slope of log IpC1 vs. log n is 0.57.
1
plot of log IpC0 values derived from linear sweep voltammograms of
ꢂ
3
MeAD (parts III and IV) vs. log v. Temperature: 4 ꢁ 1 C.
slope of log IpC2 vs. log n is 0.92. This value is near to one which
is the theoretical value for the adsorption-controlled process
and conrms the greater adsorption ability of the product of
second electron transfer process than that of the rst electron
transfer process.
The voltammograms of 3MeAD however, show a more
complex behavior. The linear sweep voltammogram of 3MeAD
ꢀ1
at a scan rate of 10 mV s , shows three cathodic peaks (C
0 1
, C
and C ). At low scan rates, I 0 and I 1 are larger than the IC2. As
2
C
C
the potential scan rate increases, IC0 increases linearly and its
shape (peak C ) becomes sharper and more symmetrical. Under
0
these conditions, the slope of log IpC0 vs. log n is 0.96 (Fig. 2,
part V, inset). This value conrms that peak C
peak which is separated by a 96 mV from peak C
peak is observed when the electrode product is strongly adsor-
0
is an adsorption
1
. This type of
42
(p. 596)
bed.
1 2
The response of peaks C and C to increasing
potential scan rate is generally similar to that seen for 2ClAD.
The LSV of 3MeAD in aqueous solution (H SO , c ¼ 1 M) is
2
4
shown in Fig. 3a and has been compared with that of in
Fig. 1 Cyclic voltammograms of 10 mM of ADs in aqueous solution acetonitrile solution containing HClO (1 M) (Fig. 3b). The most
4
ꢀ1
(
H
2
SO
4
, c ¼ 1 M) at glassy carbon electrode. Scan rate: 100 mV s
.
important feature of Fig. 3b is the presence of two peaks. Based
ꢂ
Temperature: 4 ꢁ 1 C.
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Fig. 3 (a) LSV of 3MeAD (10 mM) in aqueous solution (H
2
SO
4
, c ¼ 1 M)
and (b) LSV of 3MeAD (10 mM) acetonitrile solution (HClO
4
, c ¼ 1 M).
ꢀ1
ꢂ
Scan rate: 10 mV s . Temperature: 4 ꢁ 1 C.
Scheme 2 Electrochemical reduction pathway of ADs.
on our ndings on the adsorption nature of peak C , this
0
change in acetonitrile solution was predictable. The polarity of
the solvent has a signicant effect on the adsorption of organic
compounds onto electrode surface. The higher solubility of the
organic compounds in organic solvents decreases the adsorp-
tion process due to the higher affinity between organic
4
6
nitro group. This statement cannot be general, because, as
shown in Fig. 1, there are two peaks in the cyclic voltammogram
of aryldiazonium salts with other substituent groups, such as
3
CH , Cl, H or OH.
43
Based on our results, it is clear that the data reported for the
presence of two reduction peaks in acetonitrile solution cannot
be used in water. According to our results, it can be concluded
that in the case of 3MeAD, we are confronted with the strong
adsorption of electrochemically generated aryl radicals. This
compound and solvent. Therefore, in acetonitrile solution,
peak C (a pre-peak) is removed and the voltammogram shows
only peaks C and C .
0
1
2
The presence of two peaks in the voltammograms of aryl-
25,31,44–48
diazoniums have also been reported in other studies.
Downard and coworkers studied the electrochemical reduction
of 4-nitrobenzenediazonium ion in [Bu N]BF –ACN and stated
strong adsorption causes peak C
CVs of 3MeAD. These data, along with the results of previously
0
to appear as a pre-peak in the
42
4
4
50
published results can be used to propose the following
pathway for the electrochemical reduction of ADs (Scheme 2).
According to the proposed scheme, in the rst stage an electron
transfer concerted with the cleavage of dinitrogen produces
the aryl radical and in the second stage, the produced aryl
radical is converted to related aromatic compound by taking
one electron and one proton.
that the presence of two peaks in voltammograms is due to “a
surface-catalyzed reduction step (proceeding at a clean surface
only) followed by an uncatalyzed reduction at a more negative
50
48
potential”. Since our studies were conducted in aqueous
solution (H SO , c ¼ 1.0 M), but Downard's research in [Bu N]
2
4
4
BF –ACN, there are some important differences in our results.
4
48
In the voltammograms recorded by Downard et al., the ratio of
the rst cathodic peak to the second cathodic peak (IpC1/IpC2
)
increases with increasing potential scan rate, while our results
are completely opposite (Fig. 2). Also in the case of some aryl-
Hammett studies
diazonium salts such as 3MeAD, we clearly observed three The effect of substituents on the reduction potential of AD
51
cathodic peaks (C , C and C ) while such a case was not re- compound is analyzed using the Hammett equation:
0
1
2
ported by Downard et al.
In connection with the observation of two cathodic peaks in
the cyclic voltammogram of aryldiazonium salts, Pinson et al.
4 4
reported that (in [Bu N]BF –ACN) the steric effect can limit or
even suppress aryl radical graing for aryldiazonium
49
substituted in ortho position. They reported that the cyclic
voltammograms under these conditions show only one cathodic
49
peak. However, we observed that, the position of the
substituted group on the phenyl ring has no effect on the
number of peaks. As shown in Fig. 1 and 2, the cyclic voltam-
mograms of aryldiazonium salts such as 2ClAD, 2MeAD and
2
NO
In this regard, Richard and co-workers investigated the
electrochemical reduction of 4-nitrobenzenediazonium ion in
water (0.1 M HCl) at GC electrode and announced that peak C
corresponds to the reduction of 4NO AD with concomitant
2
AD clearly show the presence of two cathodic peaks.
1
Fig. 4 Relationship between log EpC2 and s
p
for AD derivatives in
2
aqueous solution (H SO , c ¼ 1 M) at glassy carbon electrode.
2
4
ꢂ
graing, and peak C corresponds the reduction of the graed Temperature: 4 ꢁ 1 C.
2
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log E ¼ log E + rs
(1) electrode used in the voltammetry experiments was a glassy
carbon disc (2.6 mm diameter) and a platinum wire was used as
i 0
where, E is the reduction potential of substituted AD, E is the the counter electrode. The working electrode potentials were
i
0
p
ꢀ
1
reduction potential of AD when R ¼ H, s is the substituent measured vs. Ag/AgCl (3.0 mol L KCl) (all electrodes from
constant (Hammett constant), which is dependent on the AZAR electrodes). The glassy carbon electrode was polished
substituent group (in para position) and r is the slope of the using alumina slurry followed by washing with water and
log E –s graph, reecting the sensitivity of reduction potentials acetone. All anilines derivatives were obtained from commercial
i
to the substituent effects. The Hammett plot for AD compounds sources.
is shown in Fig. 4. As can be seen, there is a relatively good
Aryldiazonium salts were synthesized by adding 0.1 mmol
linear relationship between reduction peak potential (EpC2) and aniline derivatives in 10 ml aqueous solution containing 1.0 M
Hammett constant (s). The slope of the line is 0.63. The positive of sulfuric acid. Aer cooling the temperature of the solution
ꢂ
slope indicates that the reduction potential of AD compounds is down to 4 ꢁ 1 C, 0.12 mmol of sodium nitrite was added to the
increased (easier reduction) signicantly with increasing mixture. In order to synthesize aryldiazonium salts suitable for
electron-withdrawing ability of the substituents. The results study in organic solvents, follows the method already described
also show that the reduction potential of AD compounds to vary and use only perchloric acid instead of sulfuric acid. The
in the order 4NO AD (s ¼ 0.78 (ref. 52)) > 4ClAD s ¼ 0.23 (ref. precipitate was separated by ltration and washed several times
2
p
p
ꢀ
5
(
2)) > 4SO3 AD (s ¼ 0.09 (ref. 53 and 54)) > 4MeAD (s ¼ ꢀ0.17 with cold distilled water. In the following, for voltammetry in
p
p
ref. 52)) > 4OHAD (s
p
¼ ꢀ0.37 (ref. 52)). On the other hand, 4- acetonitrile, 0.1 mmol of the precipitate was dissolved in 10 ml
methoxybenzenediazonium (4MeOAD) has a signicant devia- acetonitrile containing 1.0 M perchloric acid.
tion from EpC2–s
OCH group (resonance and inductive). The methoxide is
inductively a withdrawing and resonantly a donating group. At
p
plot. This can be due to the dual properties
3
Conflicts of interest
the moment, we do not have a strong argument for diverting The authors declare no conict of interest.
HAD from the EpC2–s plot. This linear relationship shows that
p
reduction pathway of mentioned substituents are same
together.
Acknowledgements
The authors wish to acknowledge the Bu-Ali Sina University
Research Council for the support of this work.
Conclusions
In this study electrochemical reduction of AD derivatives has
been studied in aqueous solution (H SO , c ¼ 1 M) and in
Notes and references
2
4
ꢂ
temperature 4 ꢁ 1 C by cyclic voltammetry technique at a glassy
carbon electrode. Our results show two irreversible cathodic
processes which are attributed to the reduction of ADs to the
corresponding aryl radical and reduction of aryl radical to aryl
1 F. Mo, G. Dong, Y. Zhang and J. Wang, Org. Biomol. Chem.,
2013, 11, 1582–1593.
2 M. Wang, B. C. Tang, J. C. Xiang, X. L. Chen, J. T. Ma,
Y. D. Wu and A. X. Wu, Org. Lett., 2019, 21, 8934–8937.
3 Z. Ni, X. Huang and Y. Pan, Org. Lett., 2016, 18, 2612–2615.
4 F. L. Callonnec, E. Fouquet and F. X. Felpin, Org. Lett., 2011,
13, 2646–2649.
anion. Our data indicate that when the substituted group on the
ꢀ
phenyl ring is H, Cl, OH, NO
2
, OCH
3
or SO
3
, the corresponding
diazonium salt shows poor adsorption characteristics. As
a result, the voltammograms of these diazonium salts show only
5 H. Goljani, Z. Tavakkoli, A. Sadatnabi and D. Nematollahi,
Org. Lett., 2020, 15, 5920–5924.
two reduction peaks (C1 and C ). But when the substituted
2
group is methyl, the corresponding diazonium salts show
strong adsorption characteristics. Therefore, the voltammo-
6 Q. Liu, B. Sun, Z. Liu, Y. Kao, B. W. Dong, S. D. Jiang, F. Li,
G. Liu, Y. Yang and F. Mo, Chem. Sci., 2018, 9, 8731–8737.
7 Y. He, H. Wu and F. D. Toste, Chem. Sci., 2015, 6, 1194–1198.
8 F. Mo, Y. Jiang, D. Qiu, Y. Zhang and J. Wang, Angew. Chem.,
Int. Ed., 2010, 49, 1846–1849.
grams of these diazonium salts, in addition to the peaks C
1
and
C
2
, show the adsorption peak C . The effect of substituent
0
groups on the reduction of ADs was investigated by Hammett
studies. The data are show that with increasing electron with-
drawing capacity of the substituent, the reduction of corre-
9 M. Ramanathan, Y. H. Wang and S. T. Liu, Org. Lett., 2015,
17, 5886–5889.
sponding diazonium salt becomes easier. In the end, according 10 Y. Shao, H. Zheng, J. Qian and X. Wan, Org. Lett., 2018, 20,
48
to Downard “the origin of this intriguing behavior remains
controversial”.
2412–2415.
11 J. Liu, E. Xu, J. Jiang, Z. Huang, L. Zheng and Z. Q. Liu, Chem.
Commun., 2020, 56, 2202–2205.
1
2 R. Abrams, Q. Lefebvre and J. Clayden, Angew. Chem., 2018,
7, 13587–13591.
3 H. Salehzadeh, D. Nematollahi, V. Khakyzadeh, B. Mokhtari
Experimental section
Apparatus and reagents
5
1
Cyclic voltammetry and linear sweep voltammetry were per-
and L. C. Henderson, Electrochim. Acta, 2014, 139, 270–280.
formed using an Autolab model PGSTAT 20 potentiostat/ 14 H. Salehzadeh, D. Nematollahi and S. Alizadeh,
galvanostat equipped with NOVA 1.10 soware. The working
Electroanalysis, 2015, 27, 2738–2744.
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Paper
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1
1
1
5 Z. Kudas, U. Atmaca, T. Saruhan, M. Celik and D. Ekinci, 35 M. G. Paulik, P. A. Brooksby, A. D. Abell and A. J. Downard, J.
Electroanalysis, 2020, 32, 1379–1390. Phys. Chem. C, 2007, 111, 7808–7815.
6 F. Lebon, R. Cornut, V. Derycke and B. Jousselme, 36 B. S. Flavel, A. J. Gross, D. J. Garrett, V. Nock and
Electrochim. Acta, 2019, 318, 754–761.
A. J. Downard, ACS Appl. Mater. Interfaces, 2010, 2, 1184–
1190.
37 K. J. Bell, P. A. Brooksby, M. I. J. Polson and A. J. Downard,
Chem. Commun., 2014, 50, 13687–13690.
7 Y. Yang, W. Yan, Y. Guo, X. Wang, F. Zhang, L. Yu, C. Guo
and G. Fang, Sens. Actuator Rep., 2020, 2, 100009.
8 N. Vil `a and D. B ´e langer, Electrochim. Acta, 2012, 85, 538–547.
1
1
9 M. D. Raicopol, C. Andronescu, R. Atasiei, A. Hanganu, 38 L. Lee, P. A. Brooksby and A. J. Downard, Electrochem.
E. Vasile, A. M. Brezoiu and L. Pilan, Electrochim. Acta,
016, 206, 226–237.
Commun., 2012, 19, 67–69.
39 A. J. Downard, Langmuir, 2000, 16, 9680–9682.
2
2
0 G. L. C. Paulus, Q. H. Wang and M. S. Strano, Acc. Chem. Res., 40 J. Lehr, B. E. Williamson and A. J. Downard, J. Phys. Chem. C,
013, 46, 160–170. 2011, 115, 6629–6634.
1 A. Kaplan, Z. Yuan, J. D. Benck, A. G. Rajan, X. S. Chu, 41 D. J. Garrett, J. Lehr, G. M. Miskelly and A. J. Downard, J. Am.
2
2
Q. H. Wang and M. S. Strano, Chem. Soc. Rev., 2017, 46,
530–4571.
2 M. Delamar, R. Hitmi, J. Pinson and J. M. Saveant, J. Am.
Chem. Soc., 1992, 114, 5883–5884.
Chem. Soc., 2007, 129, 15456–15457.
42 A. J. Bard and L. R. Faulkner, Electrochemical Methods, Wiley,
New York, 2nd edn, 2001. pp. 236 and 595.
43 A. M. Dowaidar, M. S. El-Shahawi and I. Ashour, Sep. Sci.
Technol., 2007, 42, 3609–3622.
4
2
2
3 P. Allongue, M. Delamar, B. Desbat, O. Fagebaume, R. Hitmi,
J. Pinson and J. M. Saveant, J. Am. Chem. Soc., 1997, 119, 201– 44 K. K. Cline, L. Baxter, D. Lockwood, R. Saylor and A. Stalzer,
07. J. Electroanal. Chem., 2009, 633, 283–290.
4 A. Chauss ´e , M. M. Chehimi, N. Karsi, J. Pinson, F. Podvorica 45 A. Benedetto, M. Balog, P. Viel, F. Le Derf, M. Salle and
and C. Vautrin-Ul, Chem. Mater., 2002, 14, 392–400. S. Palacin, Electrochim. Acta, 2008, 53, 7117–7122.
5 J. Pinson and F. Podvorica, Chem. Soc. Rev., 2005, 34, 429– 46 W. Richard, D. Evrard and P. Gros, J. Electroanal. Chem.,
39. 2012, 685, 109–115.
6 P. Doppelt, G. Hallais, J. Pinson, F. Podvorica, F. Podvorica 47 T. Menanteau, E. Levillain and T. Breton, Chem. Mater.,
and S. Verneyre, Chem. Mater., 2007, 19, 4570–4575. 2013, 25, 2905–2909.
7 S. Bouden, J. Pinson and C. Vautrin-Ul, Electrochem. 48 L. Lee, P. A. Brooksby, P. Hapiot and A. J. Downard,
2
2
2
2
2
4
Commun., 2017, 81, 120–123.
Langmuir, 2016, 32, 468–476.
2
2
8 D. Hetemi, V. No ¨e l and J. Pinson, Biosensors, 2020, 10, 4.
9 D. Belanger and J. Pinson, Chem. Soc. Rev., 2011, 40, 3995–
49 C. Combellas, D. Jiang, F. Kanou, J. Pinson and
F. I. Podvorica, Langmuir, 2009, 25, 286–293.
50 P. Andrieux and J. Pinson, J. Am. Chem. Soc., 2003, 125,
14801–14806.
4
048.
0 J. Pinson and F. I. Podvorica, Curr. Opin. Electrochem., 2020,
4, 44–48.
1 C. Combellas, F. Kanou, J. Pinson and F. I. Podvorica, J. Am. 52 C. Hansch, A. Leo and R. W. Ta, Chem. Rev., 1991, 91, 165–
Chem. Soc., 2008, 130, 8576–8577. 195.
2 P. A. Brooksby and A. J. Downard, Langmuir, 2004, 20, 5038– 53 E. A. Savicheva, G. Y. Mitronova, L. Thomas, M. J. B ¨o hm,
3
3
3
3
3
2
51 L. P. Hammett, J. Am. Chem. Soc., 1937, 59, 96–103.
5045.
J. Seikowski, V. N. Belov and S. W. Hell, Angew. Chem., Int.
Ed. Engl., 2020, 59, 5505–5509.
54 H. Zollinger, W. B u¨ chler and C. Wittwer, Helv. Chim. Acta,
1953, 36, 1711–1722.
3 T. Menanteau, M. Dias, E. Levillain, A. J. Downard and
T. Breton, J. Phys. Chem. C, 2016, 120, 4423–4429.
4 J. Lehr, B. E. Williamson, B. S. Flavel and A. J. Downard,
Langmuir, 2009, 25, 13503–13509.
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