Redox- And protonation-induced fluorescence switch in a new triphenylamine with six stable active or non-active forms

Article abstract of DOI:10.1002/chem.201404622

The synthesis, photophysical and electrochemical properties as well as theoretical calculation studies of a newly designed triphenylamine derivative are described. This original compound displays one neutral form, three oxidized forms, and two protonated

Full text of DOI:10.1002/chem.201404622

DOI: 10.1002/chem.201404622
Full Paper
&
Fluorescence Switches
Redox- and Protonation-Induced Fluorescence Switch in a New
Triphenylamine with Six Stable Active or Non-Active Forms
Cassandre Quinton, Valꢀrie Alain-Rizzo,* Cꢀcile Dumas-Verdes, Fabien Miomandre,
[a]
Gilles Clavier, and Pierre Audebert
Abstract: The synthesis, photophysical and electrochemical
properties as well as theoretical calculation studies of
a newly designed triphenylamine derivative are described.
This original compound displays one neutral form, three oxi-
dized forms, and two protonated forms with distinct photo-
physical characteristics. The interplay of the emission with
the protonation or the redox state (electrofluorochromism)
has been explored and an on–off–on–off fluorescence
switching was observed in the case of oxidation and an on–
on–off fluorescence switching in the case of protonation.
Introduction
states, whereas others can present absorption bands in the
[9d,e]
NIR area.
Electrochromism deals with compounds or materials whose
absorption properties can be modified in relation with their
The new triphenylamine derivative 3 (Scheme 1) was pre-
pared and its original photophysical and electrochemical prop-
erties were studied. In order to obtain several protonation and
redox states, three amine groups are present on the molecule
as well as two biphenyl links, which allow extended electron
delocalization on the molecule and therefore a better stabiliza-
tion of the redox states. In addition an electron-donating me-
thoxy group has been added to increase the electron-rich char-
acter and the stability of the different forms of the molecule.
Thanks to these features, this new compound has been found
to display four stable redox states (see Scheme 2), and three
protonated states (see Figure 10). The absorption and fluores-
cence variations, not only with the oxidation state, but also
with the protonation state, were investigated, and are de-
scribed therein. Theoretical quantum calculations were also
performed providing a correlation with the experimental
results.
[
1]
oxidation or reduction state. Similarly, electrofluorochromism
describes the fluorescence response of a given molecule, or
device, to an electrochemical stimulation or by extension, to
a change in its redox state, and is receiving more and more at-
[
2]
tention nowadays. Molecules bearing different fluorescence
properties related to their redox state (i.e., neutral, oxidized, or
[
3]
reduced state) have already been reported. Amatore et al. re-
ported the fluorescence change with the redox state for bio-
[
4]
analytical applications. We have recently described the elec-
[
5]
[6]
trofluorochromism of tetrazines, metal complexes, and mul-
tichromophoric compounds based on tetrazines and boron-di-
[
7]
pyrromethene (Bodipy) dyes.
However, to the best of our knowledge, there is no report
on fluorescence changes resulting from different oxidation
states of a triphenylamine derivative. Some electron-rich tri-
phenylamines are known to be easily oxidized into stable
cation radicals and the oxidation process is always associated
with a noticeable change of coloration. For example a recent Results and Discussion
article by Tanaka et al. describes the electrochemistry and elec-
Synthesis
[8]
trochromism of an extended triphenylamine derivative. Poly-
mers containing triphenylamine moieties are also well known
The design of the triphenylamine 3 (Scheme 1) was rational-
ized in order to obtain a molecule sensitive to both potential
and proton quantity variations. Dimethylamino substituents
were chosen as both proton sensors and electron-donating
groups, and a methoxy moiety was added in order to contrib-
ute to the delocalization. We also chose to place methoxy and
dimethylamino substituents on the para positions of the
phenyl groups, in order to stabilize the cation radical of the tri-
phenylamine and avoid its polymerization. The synthesis of
this new triphenylamine derivative 3 has been successfully re-
alized in few steps through cross-coupling reactions. First, the
diphenylamine derivative 1 was synthesized by using a Hart-
[
9]
for their electrochromic properties. Some of them can pres-
[
10]
ent up to four different colors
depending on their redox
[
a] Dr. C. Quinton, Dr. V. Alain-Rizzo, Dr. C. Dumas-Verdes, Dr. F. Miomandre,
Dr. G. Clavier, Prof. P. Audebert
PPSM, CNRS UMR8531, ENS Cachan
6
9
1 Avenue du Prꢀsident Wilson
4235 Cachan (France)
Fax: (+33)1-47402454
E-mail: valerie.alain@ens-cachan.fr
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201404622.
[11]
wig–Buchwald coupling reaction between anisidine and 1,4-
Chem. Eur. J. 2014, 20, 1 – 12
1
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
Scheme 1. Synthetic route to the triphenylamine derivative 3. Dba=dibenzylideneacetone, DPPF=1,1’-bis(diphenylphosphino)ferrocene.
dibromobenzene. It should be noted that the triphenylamine 2
was also isolated during this one-pot reaction (12%). A second
coupling step allowed us to transform quantitatively com-
pound 1 into the triphenylamine precursor 2. Finally, the use
[
12]
of standard Miyaura–Suzuki conditions led us to the expect-
ed final compound 3 in a very good yield (89%).
Electrochemical properties and electrofluorochromism
The redox properties of compound 3 were investigated by
cyclic voltammetry (CV). As can be seen in Figure 1, compound
Scheme 2. Representation of the oxidized forms of compound 3.
ꢀ
4
Figure 1. Cyclic voltammetry of compound 3 (5ꢂ10 m) in dichloromethane
and 0.1m Bu
um (Fc /Fc) couple. Scan rate: 40 mVs
4
NPF
6
on C. Potentials are referenced to the ferrocene/ferroceni-
+
ꢀ1
.
Figure 2. Absorption (black solid line, left y axis) and fluorescence emission
spectra (gray dash line, right y axis) of compound 3 in acetonitrile. Excitation
wavelength: lexc =264 nm.
3
exhibits three well-defined peaks corresponding to the suc-
cessive oxidation steps involving each amine moiety through
a one-electron process. The peaks are fully reversible and the
standard potentials referenced to ferrocene are 0.02, 0.23, and
0
.54 V, respectively. The structures of the different oxidized
The absorption and emission spectra of compound 3 are dis-
played in Figure 2 and the photophysical data for both com-
pounds 2 and 3 are gathered in Table 1. These triphenylamine
derivatives display one intense absorption band in the UV
region at l=304 and 346 nm, respectively for compounds 2
and 3.
In order to ascribe the origin of the absorption band, time-
dependent (TD) DFT calculations were done on both com-
pounds after geometry optimization and the results are gath-
ered in Table 1 as well as Tables S1 and S2 in the Supporting
Information. For compounds 2 and 3, this band is in fact due
forms of compound 3 are proposed in Scheme 2. The first
value corresponds to the oxidation of the central nitrogen
atom on the triphenylamine in order to obtain compound 3(I).
This oxidation is the easiest because of the electronic delocali-
zation with the phenyl rings. Its low value in comparison with
[
11d,13]
other triphenylamine derivatives
can be explained by the
presence of the dimethylamino and the methoxy electron-do-
nating groups, which stabilize by mesomeric effect the first
cation radical 3(I). The two higher values correspond to the ox-
idations of the two dimethylamino moieties, which are not in-
dependent leading successively to compounds 3(II) and 3(III).
to two p–p* transitions: the first one (l =319 and 359 nm, re-
th
&
&
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
2
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
2
, as it could be expected given the presence of five absorbing
Table 1. Experimental and calculated absorption wavelength (l), molar
absorption coefficient (e), emission wavelength (lem), fluorescence quan-
tum yield (F ) and fluorescence lifetime (t) for compounds 2 and 3 in
F
phenyl units in compound 3 against three in compound 2.
Both triphenylamine derivatives display a fluorescence band
around l=400 nm. The shift between the emission bands can
be explained similarly to the absorption band shift. The fluo-
rescence quantum yields of compounds 2 and 3 are 0.0004
and 0.39, respectively. In fact the fluorescence of compound 2
is quenched by a heavy-atom effect due to the bromine
atoms. Conversely, compound 3 has a pretty high quantum
yield (0.39) and a lifetime around 2.2 ns comparable to other
acetonitrile.
[
a]
l
exptl
e
exptl
l
calcd
e
calcd
l
em
F
F
t
ꢀ
1
ꢀ1
ꢀ1
ꢀ1
[
nm] [Lmol cm
]
[nm] [Lmol cm
]
[nm]
[ns]
[
b]
2
3
304
346
26000
43400
316
357
41500
93300
392
424
0.0004 n.d.
0.39 2.2
[
(
2 4
a] Fluorescence quantum yields measured with quinine sulfate in H SO
[
15]
F
0.5n) as a standard (F =0.546). [b] Not determined.
[14]
triphenylamine compounds.
The spectroscopic properties of compound 3 upon oxidation
have been studied. The photophysical data of all the species
are gathered in the Table 2. The generation of the different oxi-
Table 2. Experimental and calculated absorption wavelength (l), emis-
sion wavelength (lem) and fluorescence quantum yield (F
ent species of compound 3 in acetonitrile.
F
) for the differ-
[
a]
l
1
l
2
l
3
l
4
l
5
l
em
F
F
[
nm]
[nm]
[nm]
[nm]
[nm]
[nm]
3
3
3
3
3
3
346
326
326
313
355
266
–
472
472
540
–
–
1361
1136
591
–
–
–
–
664
–
658
–
–
–
728
–
728
424
409-519
0.39
0.06
0.12
<0.0001
0.20
[
b]
[b]
(I)
[
b]
(II)
513
–
492
–
(III)
+
(H )
2
3
+
(H )
499
591
<0.0001
[
(
a] Fluorescence quantum yields measured with quinine sulfate in H
2
SO
4
[15]
0.5n) as a standard (F
F
=0.546). [b] Approximate estimation due to
a mixture with species with lower and higher oxidation degrees.
dized forms (two cation radicals and one dication) of com-
pound 3 (Scheme 2) can be achieved either by electrochemical
or by chemical oxidation. First of all, a one-electron chemical
oxidation was chosen and Cu(ClO ) was used as a mild and
Figure 3. Representation of the main molecular orbitals involved in the elec-
tronic transitions of compounds 2 and 3 and their corresponding energy
levels.
4
2
clean oxidant, which has been recently reported to effectively
generate arylaminium cation radicals by our group and oth-
spectively) from the HOMO localized on the whole molecule to
[11d,13a,16]
a p* orbital localized on the two identical branches (L+1 and
ers.
Another advantage of using Cu(ClO4)2 is that it
LUMO, respectively) and the second one (l =303 and
gives no absorption nor emission in the UV/Vis domain at low
concentrations and its reduction potential in acetonitrile is
th
332 nm, respectively) from the HOMO to the L+2 localized on
+
the whole molecule (Figure 3). Absorption spectra constructed
from these theoretical data (Figures S5 and S6 in the Support-
ing Information) gave calculated absorption maxima at l=316
and 357 nm for compounds 2 and 3, respectively (Table 1).
This band is very sensitive to the substituents on the triphenyl-
amine core. Indeed compound 2 is substituted with two elec-
tron-withdrawing bromine atoms, which lower the p and p*
levels compared to compound 3, which is substituted with
two electron-donating dimethylaminophenyl groups (Fig-
ure S10 in the Supporting Information). As the p* orbital is less
influenced, the energy gap for compound 2 is therefore higher
and thus the absorption wavelength is red shifted from com-
pound 2 to compound 3. Molecules 2 and 3 display high
molar absorption coefficients because of the transition nature
and an important overlap of the orbitals. It can be noticed that
the molar absorption coefficient of compound 3 is closely
equal to the ratio 5:3 of the corresponding one of compound
0.7 V versus Fc/Fc , which matches well with the different
redox potentials of compound 3. In order to prove that only
an oxidation occurred with Cu(ClO ) (no complexation reac-
4
2
II
tion for example between Cu and the triphenylamine deriva-
tives), other oxidants could be used. Fe(ClO ) was also chosen
4
3
because as for Cu(ClO4)2, Fe(ClO4)3 gives no absorption nor
emission in the UV/Vis domain at low concentrations and its
+
[17]
reduction potential in acetonitrile is 1.07 V versus Fc/Fc ,
which matches well too with the different redox potentials of
compound 3. The cation radicals of compound 3 were thus
generated by either using Cu(ClO ) or Fe(ClO ) in acetonitrile
4
2
4 3
and characterized by absorption and emission spectroscopy.
Indeed compound 3 has three oxidizable sites and, as shown
in the electrochemistry section, these oxidations occur step by
step.
Here, only the evolution of the absorption spectra of com-
pound 3 upon oxidation with Cu(ClO4)2 is displayed in
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
3
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
Figure 5. Representation of the main molecular orbitals involved in the elec-
tronic transitions of compound 3(I).
groups are) to the S+1 orbital (Figure 5). At l=472 and
1361 nm only one transition is involved: one from the SOMO
to the S+1 orbital and one from the Sꢀ1 to the SOMO, respec-
tively (Table S3 in the Supporting Information). Furthermore
the SOMO is delocalized on the entire molecule.
One can observe in the UV/Vis region the appearance of iso-
sbestic points: one around l=264 nm and another one at l=
386 nm, which is in agreement with an equilibrium between
only two different forms, that is, compounds 3 and 3(I).
By increasing the amount of Cu(ClO ) , from R=1 to 2, one
4
2
dimethylamino moiety is then oxidized and compound 3(I) is
transformed in compound 3(II). The evolution of the absorp-
tion spectra is shown in Figure 4b. The bands located at l=
326 and 472 nm decrease slightly and the band in the IR
region is blue shifted from l=1361 to 1136 nm. Similarly, the
Figure 4. Absorption spectra recorded upon oxidation of compound 3 by
II
ꢀ5
ꢀ1
Cu(ClO
a) From R=0 (black solid line) to R=1 (black dashed line), b) from R=1
black solid line) to R=2 (black dashed line), and c) from R=2 (black solid
4 2 3
) in CH CN as a function of R=[Cu ]/[3], [3]=6.4ꢂ10 molL .
band at l=326 nm corresponds to two p–p* transitions (l =
th
(
line) to R=3 (black dashed line).
330 nm, HOMO!L+2 and l =320 nm, Hꢀ1!L+1), at l=
th
4
72 nm to one p–p* transition (l =360 nm, HOMO!L+1),
th
and at l=1136 nm to one p–p* transition (l =947 nm,
th
Figure 4. The evolution of the absorption spectra of compound
HOMO!LUMO), Table S4 in the Supporting Information). Iso-
sbestic points are located at l=271, 375, and 410 nm, which is
in agreement with an equilibrium between compounds 3(I)
and 3(II). Similarly, from R=2 to R=3, the bands located at
l=313 and 1136 nm decrease, whereas new bands between
l=540 (Sꢀ2!SOMO), and 728 nm (SOMO!S+1 and Sꢀ1!
S+1) appear (Figure 4c) (see Table S5 in the Supporting Infor-
mation). Isosbestic points are located at l=284, 380, 437, 472,
and 848 nm corresponding to the equilibrium between com-
pounds 3(II) and 3(III). These isosbestic points show that the
oxidation is indeed achieved step by step and these different
compounds can be observed one by one.
3
upon oxidation with Fe(ClO ) shows a similar behavior (com-
4 3
pare Figure S5 in the Supporting Information). Figure 4a dis-
plays the evolution of the absorption spectra of compound 3
upon oxidation with Cu(ClO4)2 from zero to one equivalent.
Two bands gradually appear, one in the visible region at l=
472 nm, the other in the IR region at l=1361 nm, whereas the
absorption band centered at l=346 nm decreases and shifts
to l=326 nm. The new bands are attributed to the formation
of the monocation radical centered on the triphenylamine
core, that is, compound 3(I). TD-DFT calculations allow attribut-
ing these bands to various p–p* transitions. At l=326 nm, it
comes from two transitions: one (l =370 nm) from the Sꢀ2
The fluorescence spectra upon oxidation were recorded in
the same ranges of [oxidant]/[3] ratios as those used for the
spectrophotometric oxidations and are shown in Figure 6. One
can observe a similar behavior in the fluorescence spectra evo-
lution upon oxidation with Cu(ClO ) or Fe(ClO ) . This evolu-
th
orbital (delocalized on the entire molecule) to the S+1 orbital
(localized on the two branches to which the dimethylamino
groups belong) and one (l =337 nm) from the Sꢀ1 orbital
th
(localized on the two branches where the dimethylamino
4
2
4 3
&
&
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
4
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
513 nm, whereas an absorption
band is observed at lower ener-
gies in the IR domain; this rela-
tively rare situation probably in-
dicates that, in this very delocal-
ized species, fluorescence can be
observed stemming from a S –S
n
0
transition, with n>1. As shown
in Figure 6c, the fluorescence in-
tensity decreases simultaneously
to the appearance of compound
3(III), the fluorescence of which
is negligible (quantum yield esti-
mated below 0.0001).
One important characteristic
of electrofluorochromic materials
is the contrast ratio Ifmax/Ifmin in-
volving the fluorescence intensi-
ty at the same wavelength for
compound 3 at different oxida-
tion degrees. These results are
gathered in Table 3. We can note
that the contrast ratio between
compounds 3 and 3(I) is ten be-
cause the solution contains com-
pound 3 and compound 3(II) in
a small amount. This is also the
reason why the contrast ratio
between compounds 3(I) and
3(II) is only three. The contrast
ratio of ten (between com-
pounds 3 and 3(I) at l=424 nm)
or 29 (between compounds 3
and 3(II) at l=424 nm) is mod-
erate. What is the most impres-
4 2 4 3 3
Figure 6. Emission spectra recorded upon oxidation of compound 3 by using Cu(ClO ) or Fe(ClO ) in CH CN as
ꢀ
5
ꢀ1
a function of R=[oxidant]/[3], [3]=10 molL . a) From R=0 (black solid line) to R=1 (black dashed line),
b) from R=1 (black solid line) to R=2 (black dashed line), and c) from R=2 (black solid line) to R=3.3 (black
dashed line).
tion is not dependent of the oxidant that is used. As shown in
the electrochemistry section, these oxidations occur step by
step and because no particular reaction could occur in the ex-
cited state, one can suppose that the emission evolution is fol-
lowing the absorption one. So in this case, for one equivalent
of oxidant, compound 3(I) is the major form, and it is com-
pound 3(II) and compound 3(III) with two and three equiva-
lents, respectively.
Table 3. Contrast ratio between the different oxidized species of com-
pound 3.
[a]
[a]
[a]
[a]
3
3(I)
3(II)
3(III)
[
b]
3
3
–
3
1
10
–
2
29
3
–
8344
870
290
–
[b]
(I)
3(II)
3(III)
[
b]
[
b]
3232
1182
2915
One can observe a decrease of fluorescence intensity at l=
[
a] At l=513 nm [b] At l=424 nm.
4
24 nm upon oxidation by either Cu(ClO ) or Fe(ClO ) from
4 2 4 3
R=0 to R=1 (Figure 6a) and, respectively, with a factor of 4.4
and 5.0. The decrease of the overall fluorescence intensity is
linear with the transformation of 3(0) into 3(I) (see Figure S7 in
the Supporting Information) and the fluorescence quantum
yield is calculated to be 0.39 for compound 3 and estimated
to be 0.06 for compound 3(I). Then with oxidation of 3(I) into
sive observation is the contrast ratio of compound 3(III) with
all other species at l=424 or 513 nm, which is at least 290
and can be as high as 8344.
Finally, compound 3 is stable in four redox states with differ-
ent spectroscopic properties. This behavior is not dependent
of the used oxidant because one can observe the same evolu-
tion in the case of two different oxidants, that is, Cu(ClO ) or
3
(II), the fluorescence intensity at l=424 nm further decreases
and concomitantly a new red-shifted band grows at l=
13 nm (Figure 6b). Compound 3(II) is slightly fluorescent
F =0.12). Fluorescence is interestingly observed at l=
4
2
5
Fe(ClO ) . Indeed it shows four different color states. In the
4 3
(
neutral state, compound 3 is colorless whereas upon oxidation
F
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
5
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
[19]
ready observed in conjugated triphenylamine derivatives,
but this time the IVCT process is observed with only one tri-
phenylamine core. At intermediate potential (0.8 V) the NIR
band starts to decrease in intensity and becomes blue shifted,
whereas a new band first centered at l=700 nm and then
progressively shifting to l=740 nm starts to grow. All those
data fit perfectly well with the behavior observed for chemical
oxidation, evidencing that the same oxidized species are
formed whatever the oxidation process is. Upon reduction
from the fully oxidized state (Figure 8b), the recorded spectra
show the same trend in the band evolution in the opposite di-
rection: namely the NIR band increases at first and then de-
creases again, the l=700 nm band quickly vanishes, whereas
the l=345 and 470 nm bands increases and decreases, respec-
tively, in a symmetrical way. Even if the overall reduction pro-
cess takes some time to convert the oxidized forms into the
fully reduced one, one can estimate that the process is actually
reversible with the same intermediate species formed at the
forward and backward steps.
Then, the fluorescence intensity at l=530 nm was recorded
in the same cell as a function of time, along with a CV curve at
low scan rate (Figure 9). Comparison between the current and
the fluorescence intensity when varying the potential clearly
shows that the first oxidation leads to a dramatic quenching,
whereas the second oxidation step leads to a slowdown in the
fluorescence quenching with a small plateau. The third oxida-
tion step induces quenching again. The process is reversible,
as shown by the shape of the curves after the potential rever-
sal, although the amplitude of the variation is smaller for the
backward step. Compared to the fluorescence variation record-
ed upon chemical oxidation, it can be noticed that a non-mon-
otonic behavior is observed in both cases, evidencing the fact
Figure 7. a) Absorption and b) fluorescence properties of the four redox
states of compound 3.
it becomes yellow (compound 3(I)) and then turns into green
(
compound 3(II)) and blue (compound 3(III)) when completely
oxidized. Besides one of the redox states, namely compound
(III), is not fluorescent and the three others emit light, com-
3
pounds 3(0) and 3(II) at l=424 and 513 nm, respectively. In
the presence of one equivalent
of oxidant, one can observe
a low fluorescence band, which
is more diffuse from l=400 to
600 nm. These properties are
summarized in Figure 7.
In order to test the reversibili-
ty of the system, spectroelectro-
chemistry was performed in
a tailored thin layer electrochem-
[
18]
ical cell.
Electronic absorption spec-
troelectrochemistry was record-
ꢀ
4
ed for a 5ꢂ10 m solution of
compound 3 in acetonitrile. The
results are shown in Figure 8.
Upon gradual oxidation (Fig-
ure 8a), a broad band in the NIR
region starts to appear simulta-
neously to another one centered
at l=470 nm, whereas the band
centered at l=345 nm gradually
disappears. This NIR band is re-
lated to an intervalence charge-
ꢀ
4
Figure 8. Electronic absorption (UV/Vis/NIR) spectroelectrochemistry of compound 3 in acetonitrile (5ꢂ10 m).
a) Variation of the absorbance versus the wavelength upon increasing the potential from 0.2 V to the indicated
value. The inset highlights the NIR region. b) Variation of the absorbance versus the wavelength upon decreasing
the potential from 1.4 V to the indicated value. The inset highlights the NIR region. A background spectrum is re-
transfer (IVCT) process as was al- corded under open circuit potential and substracted from all other spectra.
&
&
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
6
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
displays the corresponding variations of the fluorescence in-
tensity measured at l=430 nm (excitation wavelength l=
265 nm) and the coulombic charges when potential steps are
applied between ꢀ0.2 and +0.55 V, that is, when switching
between compounds 3(0) and 3(I). One can observe that the
fluorescence behavior totally follows the electrochemical
signal, especially the fluorescence is fully recovered at the end
of each cycle. This is not the case when the upper potential is
pushed further to reach the second oxidation state 3(II).
(
Figure 10, bottom): as expected the amplitude of the first fluo-
rescence decrease is higher, but the reversibility is clearly
lower. It may seem not consistent with the result in Figure 9,
in which the fluorescence intensity is almost reversible after
the third oxidation, but Figure 10 shows a chronocoulometry
during only 40 s. A longer time would give back a higher
signal. The time required for a good cyclicibility is higher than
the one observed for thienoviologens which is only five sec-
Figure 9. Current intensity (black dashed line, right scale) and fluorescence
intensity (gray line, left scale) versus time for a cyclic voltammetry between
ꢀ1
0
4 6
.2 and 1.4 V at 10 mVs of compound 3 in acetonitrile and 0.1m Bu NPF
on Pt. Potential measured versus a pseudo-reference Ag wire. Excitation
wavelength: l=375 nm. Fluorescence intensity recorded at 530 nm.
[21]
that the successive oxidation steps have various influences on
the fluorescence: the mono- and tricationic states are clearly
non-fluorescent, whereas the dicationic one is probably weakly
fluorescent. The contrast ratio Ifmax/Ifmin of five is the same
onds. The amount of recovered fluorescence at the end of
each cycle depends on the potential values (not only the
upper limit but also the lower one) and on the duration of
each cycle. Leaving more time or bringing back the potential
to a lower value has a positive impact on the reversibility.
order as the one obtained for thienoviologens (i.e,. Ifmax/Ifmin
=
1
0). These values are enough to be seen at naked eye, even if
[
20]
they are lower than for other compounds.
Behavior upon protonation
We investigated the origin of the fluorescence at l=530 nm
by recording excitation spectra when cycling the potential (see
Figure S6 in the Supporting Information). Upon oxidation,
a gradual decrease of the band centered near l=355 nm in
the excitation spectra is clearly observed in the 0.5–1.0 V
range, whereas in the 0–0.5 V potential range, that is, when
compounds 3(0) and 3(I) are the main redox species, this band
is unaffected. No new band in the excitation spectra below the
emission wavelength (l=530 nm) can be seen upon oxidation.
This behavior is reversible, cycling back the potential in the
negative direction making the excitation band at l=355 nm
growing again with the same shape. Thus, it can be concluded
that the fluorescence observed at l=530 nm upon oxidation
is correlated with the disappearance of the band at l=355 nm
in the excitation spectra, which is also observed in the absorp-
tion spectra (see Figure 8). Thus, although compound 3(II) is
actually luminescent, it is not surprising not to observe an in-
crease in the fluorescence intensity in Figure 9, because the
absorption at the excitation wavelength gradually decreases as
compound 3(II) is formed. The exact origin of this fluorescence
remains however still unclear because: 1) no new band ap-
pears in the excitation spectra when transforming compound
Because of the presence of dimethylamino groups, compound
3 is not only sensitive to oxidation as previously demonstrated
but also to acido–basic conditions. To the best of our knowl-
edge, only few proton sensors based on triphenylamine deriva-
[
22]
tives have already been published, either based on chromic
[23]
or fluorescent switch.
The acidic constants for the nitrogen atoms of the dimethyl-
phenylamine and of the triphenylamine are around 11.5 and
[24]
1 in acetonitrile, respectively.
Hence, the dimethylamino
groups are more basic than the triphenylamine moiety and are
protonated first. The lone electron pair of the nitrogen atom
on the triphenylamine might be quaternized at higher proton
concentrations. The structures of the different protonated
forms of compound 3 are proposed in Scheme 3.
Therefore, a preliminary study of compound 3 was realized
in order to check if the central nitrogen atom of the triphenyl-
amine core could be protonated. A strong acid, the perchloric
[25]
acid (pKa around ꢀ1 in acetonitrile) was used and the evolu-
tion of the absorption spectra upon protonation is shown in
Figure 11. At low amount of protons, it is likely that only the
nitrogen atoms on the dimethylamino groups could be pro-
5
3(I) into compound 3(II) and 2) the fluorescence switch is not
tonated, then the third protonation occurred with about 10
fully reversible when the potential is pushed toward the
second and third oxidation states (see below). When the po-
tential is slowly scanned upon the whole range allowing to
reach the four redox states of compound 3, a modulation in
the fluorescence intensity is observed, with a loss at the end of
the first backward scan and a kind of steady-state behavior for
the following scans (Figure S18 in the Supporting Information).
The cyclability of the fluorescence switch was also assessed
upon successive potential steps by using the same system as
above (described in the Experimental Section). Figure 10 (top)
equivalents of protons and the solution became slightly blue.
Then the spectroscopic properties of compound 3 upon
protonation by perchloric acid were investigated in more
depth. The amounts effectively employed rose up to five
equivalents of perchloric acid but in Figure 12 the evolution
over the addition of only three equivalents is displayed, be-
cause no significant change in absorption or in fluorescence
could then be detected before very high acid concentrations
were reached (Scheme 3). During all the acidification process
(from zero to more than three equivalents of HClO ), the ab-
4
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
7
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
sorption band located around l=340 nm decreases
and two isosbestic points appear at l=265 and
380 nm. Only one set of isosbestic points is observed
even if there are normally two acid/base equilibriums
because of the two nitrogen atoms.
In order to know exactly which forms are in the so-
lution upon protonation, an analysis of the spectro-
photometric protonation data by the SPECFIT pro-
gram was performed. Three hypotheses were investi-
gated: only one protonation, two successive protona-
tion steps, and two simultaneous protonation steps.
Only the third hypothesis was confirmed. The recon-
struction, from the calculated equilibrium constant,
of the absorption spectra of compounds 3 and
+
3
(H ) (Figure 13a) is consistent with the experimen-
2
tal results, which provides a criterion for acceptability
of the fit. Accordingly, Figure 13b presents the calcu-
+
lated distribution curves of compounds 3 and 3(H )
2
and one can see that with three equivalents of pro-
tons, around 80% of compound 3 is transformed
+
into compound 3(H ) , which is in agreement with
2
the fact that no significant evolution in the absorp-
tion is observed after three equivalents of protons
have been added. So the last spectrum (for three
equivalents of HClO ) corresponds to the absorption
4
+
of compound 3(H ) and we cannot observe the for-
2
+
mation of the monoprotonated form 3(H ).
Concerning the fluorescence behavior, the fluores-
cence intensity centered at l=424 nm decreases
upon protonation, which is in agreement with the
decreasing quantity of compound 3 and a band cen-
tered at l=492 nm appears at the same time. This
+
latter band is characteristic of the 3(H ) form.
2
+
When three equivalents of H were added, no evo-
lution in absorption nor in emission is observed and
the absorption and emission spectra still correspond
+
to the one of compound 3(H ) (see Figure 12). The
2
Figure 10. Comparison of the fluorescence intensity (black solid line) and the coulombic
charge (gray dashed line) variations upon five successive potential steps from ꢀ0.2 to
fluorescence intensity is thus modulated from the
neutral form to the diprotonated form with two
emission wavelengths, one centered at l=424 nm
and the other one at l=492 nm. The quantum yield
decreases from 0.39 for compound 3 to 0.20 for
+
0.55 (top) or ꢀ0.2 to +0.75 V (bottom) of compound 3 in acetonitrile and 0.1m
4 6
Bu NPF on Pt. Potential measured versus a pseudo-reference Ag wire. Excitation wave-
length: l=265 nm. Fluorescence intensity recorded at l=430 nm.
+
+
compound 3(H ) . The 3(H ) form, formed at very
2
3
low pH values, is non-emissive.
In summary, the spectroscopic properties of compound 3
can be influenced by addition of perchloric acid. By increasing
the amount of protons in the solution, the strongly fluorescent
compound 3 at l=424 nm turns into the slightly less fluores-
+
cent derivative 3(H ) , which emits at l=492 nm and subse-
2
+
quently to the non-emissive compound 3(H ) . The results
3
clearly indicate that the triphenylamine derivative 3 is a highly
efficient “on–on–off” switch for protons, displaying two specific
emission wavelengths for the on-state system. In conclusion,
the fluorescence modification of compound 3 in solution with
the amount of protons shows that compound 3 can be used
to monitor local acidity variations.
Figure 11. Absorption spectra recorded upon acidification of compound 3
by HClO in CH CN, [3]=1.0ꢂ10 molL .
4 3
ꢀ
5
ꢀ1
&
&
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
8
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
Conclusion
In summary, N,N-di-[4’’-(N’,N’-dimethyl)-1’,1’’-biphenyl]-4-anisi-
dine was synthesized by cross-coupling reactions and then
studied by cyclic voltammetry, UV/Vis spectroscopy, and fluo-
rescence spectroscopy. Spectroelectrochemistry reveals that
this triphenylamine derivative has distinct electrochromic prop-
erties with four different color states (colorless, yellow, green,
and blue) and three different emission properties (not emis-
sive, purple, and green fluorescent), according to its redox
state. These redox states can be reached either by chemical or
electrochemical oxidation. Furthermore, upon successive pro-
tonation steps, this compound displays also three different be-
haviors in absorption (colorless, yellow, and blue) and in emis-
sion (purple, cyan, and non-emissive at increasing proton con-
centration). An on–on–off fluorescence switch by using only
one molecule could therefore be observed with both redox
and acid–base inputs.
Scheme 3. Representation of the successive protonated forms of compound
3.
Experimental Section
Spectroscopic measurements: UV/Vis absorption spec-
tra were recorded on a Cary 5000 spectrophotometer in
1
cm optical length quartz cuvettes. The data were glob-
ally analyzed by the program SPECFIT Global Analysis
System V3.0 for 32-bit Window System to determine the
species obtained upon protonation and the thermody-
namic constants. This program uses singular value de-
composition and non-linear regression modeling by the
[26]
Levenberg–Marquardt method.
Corrected emission
spectra were obtained on a Jobin–Yvon Horiba Spex Flu-
oroMax-3 spectrofluorometer. Acetonitrile (SDS, spectro-
metric grade) was used as the solvent for absorption
and fluorescence measurements. The fluorescence quan-
tum yields were determined by using quinine sulfate in
[13b]
H SO (0.5n) as a standard (F =0.546).
The estimat-
2
4
F
ed experimental error is less than 10%. For the emission
measurements, a right-angle configuration was used.
Fluorescence decay curves in solution were obtained by
using a time-correlated single-photon counting method
by using a titanium–sapphire laser pumped by an argon
ion laser (Tsunami, by Spectra-Physics, 82 MHz, 1 ps
pulse width, repetition rate lowered to 4 MHz with
a pulse peaker, a doubling crystal was used to reach l=
4
95 nm excitation). The Levenberg–Marquardt algorithm
was used for the non-linear least-squares fit. Copper(II)
perchlorate hexahydrate was commercially available
from Aldrich.
Electrochemistry: Dichloromethane or acetonitrile (SDS,
HPLC grade) and electrolyte salts (tetrabutylammonium
hexafluorophosphate from Fluka, puriss.) were used
without further purification. Cyclic voltammetry was per-
formed in a three-electrode cell with a potentiostat (Ver-
saSTAT4, Princeton Applied Research) driven by a PC. A
carbon electrode disk (1 mm diameter) was used as the
+
working electrode, whereas a platinum wire and Ag
(0.01m in acetonitrile)/Ag were used, respectively, as the
counter and reference electrodes. All the investigated
solutions were desaerated by argon-bubbling for at least
2 min before performing the electrochemical measure-
Figure 12. Spectra recorded upon acidification of compound 3 by HClO
4
in CH
3
CN as
ꢀ
5
ꢀ1
a function of R=[HClO
behavior. lexc =265 nm.
4
]/[3], [3]=1.0ꢂ10 molL . a) Absorbance and b) fluorescence
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
9
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
[28]
to the oscillator strength as implemented in GaussSum The ecalcd
value was thus obtained at the maximum of the band.
Synthesis: Reagents were commercially available from Aldrich and
used without further purification. Column chromatography was
performed with SDS 0.040–0.063 mm silica gel. All compounds
1
were characterized by the usual analytical methods: H and
13
C NMR spectra were recorded with a JEOL ECS (400 MHz) spec-
trometer. All chemical shifts are referenced to the solvent peak (J
values are given in Hz). Melting points were measured with
a Kofler melting-point apparatus. IR spectra were recorded with
a Nicolet Avatar 330 FTIR spectrometer.
N-4-Bromophenyl-4-anisidine (1): To a solution of palladium chlo-
ride (35 mg, 0.197 mmol) and 1,1’-bis(diphenylphosphino)ferrocene
(148 mg, 0.271 mmol) in dried toluene (5 mL) under an argon at-
mosphere was added 1,4-dibromobenzene (5.81 g, 24.63 mmol) at
room temperature. The resulting mixture was stirred for 10 min.
Then sodium tert-butoxide (1.92 g, 19.98 mmol) and 4-anisidine
(1.06 g, 8.61 mmol) were added to this mixture and stirred at
110 8C for 44 h. The reaction mixture was cooled to room tempera-
ture and water (10 mL) was added. The aqueous layer was extract-
ed with CH Cl (3ꢂ10 mL). The organic layer was dried over anhy-
2
2
drous sodium sulfate, filtered, and concentrated under reduced
pressure. The crude product was purified by a silica gel flash chro-
matography (dichloromethane/PE (2:8) to dichloromethane) to
1
give compound 1 (1.33 g, 81%) as a gray solid. M.p. 848C; H NMR
(
400 MHz, CDCl ): d=7.29 (d, J=8.7 Hz, 2H), 7.06 (d, J=8.7 Hz,
3
2
3
1
H), 6.89 (d, J=8.7 Hz, 2H), 6.76 (d, J=8.7 Hz, 2H), 5.52 (s, 1H),
13
.82 ppm (s, 3H); C NMR (100 MHz, CDCl ): d=155.7, 144.5, 135.1,
3
32.1, 122.8, 117.0, 114.8, 111.0, 55.6 ppm; IR: n˜ =3419, 3050–2850,
Figure 13. Reconstruction, from the calculated equilibrium constant of a) the
+
ꢀ1
absorption spectra of compounds 3 and of 3(H )
2
and b) the calculated dis-
1594, 1508, 1491, 1243, 1030, 813cm
.
+
+
2
tribution curves of compounds 3 and 3(H ) versus [H ].
N,N-Di(4-bromophenyl)-4-anisidine (2): To a solution of tris(diben-
zylideneacetone)dipalladium(0) (282 mg, 0.308 mmol) and 1,1’-bis-
ꢀ
5
ꢀ1
[
3]=1.0ꢂ10 molL .
(diphenylphosphino)ferrocene (230 mg, 0.421 mmol) in dried tolu-
ene (10 mL) under an argon atmosphere was added 1,4-dibromo-
benzene (5.17 mg, 21.92 mmol) at room temperature. The resulting
mixture was stirred for 10 min. Then sodium tert-butoxide (1.53 g,
ments. The reference electrode was checked versus ferrocene as
recommended by IUPAC.
1
5
1
5.92 mmol) and N-4-bromophenyl-4-anisidine (1) (1.12 g,
.25 mmol) were added to this mixture and stirred at 1108C for
5 h. At this time, the starting materials had disappeared as
Electrofluorochromism: A thin-layer electrochemical cell (Pt mini-
grid working electrode, Ag pseudo-reference electrode, Pt counter
electrode) was filled with the solution of the compound of interest.
For fluorescence spectroelectrochemistry, excitation and emission
were focused on the working electrode through optical fibers con-
nected to a Jobin–Yvon Fluorolog 3 spectrophotometer. The fluo-
rescence near the maximum emission wavelength was recorded
versus the time simultaneously to the current corresponding to
low scan rate cyclic voltammetry (10 mVs ). The electrochemical
cell was connected to a CHInstruments (CHI 600) potentiostat
driven by a PC. For UV/Vis spectroelectrochemistry, the thin-layer
cell was directly inserted in the spectrophotometer (Cary 5000,
Varian). The spectrum for open circuit potential was recorded and
used as background for all other subsequent spectra.
judged by TLC. The reaction mixture was cooled to room tempera-
ture and concentrated under reduced pressure. The crude product
was purified by a silica gel flash chromatography [dichlorome-
thane/PE (2:8) to dichloromethane/PE (3:1)] to give compound 2
1
(1.74 g, quantitative yield) as a white solid. M.p. 758C; H NMR
ꢀ
1
(400 MHz, CDCl ): d=7.32 (d, J=9.2 Hz, 4H), 7.07 (d, J=9.2 Hz,
3
2
3
1
3
1
H), 6.93 (d, J=8.7 Hz, 4H), 6.88 (d, J=8.7 Hz, 2H), 3.82 ppm (s,
13
H); C NMR (100 MHz, CDCl ): d=156.7, 146.8, 139.7, 132.2,
3
27.4, 124.3, 115.1, 114.6, 55.5 ppm; UV/Vis (CH Cl ): l (e)=
max
2
2
ꢀ
1
ꢀ1
04 nm (26000 Lcm mol ); IR: n˜ =3050–2830, 1578, 1504, 1482,
ꢀ
1
237, 813cm ; F =0.0004 in CH CN.
F
3
N,N-Di-[4’’-(N’,N’-dimethyl)-1’,1’’-biphenyl]-4-anisidine
(3):
In
Quantum chemical calculations: Calculations were performed at
the MESO calculation centre of the ENS Cachan (Nec TX7 with 32
processors of type Itanium 2). Molecules were drawn with the
Gaussview 03 software by using included templates and their ge-
a Schlenk flask under an argon tetrakistriphenylphosphine
(130 mg, 0.112 mmol, 0.05 equiv) was added to a solution of N,N-
bis-(4’-bromophenyl)-4-anisidine (999 mg, 2.31 mmol, 1.0 equiv) in
toluene (15 mL). The mixture was stirred at room temperature for
15 min and then solutions of 4-(N,N-dimethylamino)phenylboronic
acid (846 mg, 5.13 mmol, 2.2 equiv) in methanol (7 mL) and of
sodium carbonate (985 mg, 9.29 mmol, 4.0 equiv) in distilled water
(4.6 mL) were added. The mixture was heated at 808C for 7 h. After
the mixture was cooled down, dichloromethane (50 mL) and satu-
rated ammonium chloride solution (50 mL) were added. Organic
compounds were extracted with dichloromethane (3ꢂ50 mL). The
combined organic phases were dried over anhydrous sodium sul-
[27]
ometry optimized at the B3LYP/3-21g(d) level of theory. Infrared
spectra were calculated on the final geometry to ascertain that
a minimum was obtained (no negative frequencies). Time-depend-
ant density functional theory (TDDFT) calculations at the PBE0 level
of theory with the 6-31g(d) basis set were subsequently performed.
Reconstructed absorption spectra have been obtained by convolu-
tion of Gaussian functions for each calculated transition with a full
ꢀ
1
width at half maximum (FWHM) of 2500 cm and a surface equals
&
&
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
10
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
fate, filtrated, and concentrated under reduced pressure. The crude
product was purified by silica gel flash chromatography (dichloro-
[10] a) X. Cheng, J. Zhao, C. Cui, Y. Fu, X. Zhang, J. Electroanal. Chem. 2012,
6
77–680, 24–30; b) C. Xu, J. Zhao, C. Cui, M. Wang, Y. Kong, X. Zhang,
J. Electroanal. Chem. 2012, 682, 29–36.
methane/PE (2:8) to dichloromethane) to give compound 3
1
[11] a) J. F. Hartwig, M. Kawatsura, S. I. Hauck, K. H. Shaughnessy, L. M. Alca-
zar-Roman, J. Org. Chem. 1999, 64, 5575–5580; b) N. Kataoka, Q. Shelby,
J. P. Stambuli, J. F. Hartwig, J. Org. Chem. 2002, 67, 5553–5566; c) J. P.
Wolfe, S. L. Buchwald, J. Org. Chem. 2000, 65, 1144–1157; d) C. Quinton,
V. Alain-Rizzo, C. Dumas-Verdes, G. Clavier, F. Miomandre, P. Audebert,
Eur. J. Org. Chem. 2012, 1394–1403; e) J. P. Wolfe, S. Wagaw, S. L. Buch-
wald, J. Am. Chem. Soc. 1996, 118, 7215.
(
1.06 g, 89%) as a white solid. M.p. 2438C; H NMR (400 MHz,
CDCl ): d=7.49 (d, J=8.7 Hz, 4H), 7.44 (d, J=8.2 Hz, 4H), 7.15 (d,
3
J=8.7 Hz, 2H), 7.11 (d, J=8.7 Hz, 4H), 6.87 (d, J=9.2 Hz, 2H), 6.81
1
3
(
(
d, J=8.7 Hz, 4H), 3.82 (s, 3H), 2.99 ppm (s, 12H); C NMR
100 MHz, CDCl ): d=156.2, 149.7, 146.5, 141.0, 134.8, 129.2, 127.4,
3
1
27.3, 126.9, 123.3, 114.9, 113.0, 55.6, 40.8 ppm; UV/Vis (CH CN):
3
ꢀ
1
ꢀ1
lmax (e)=346 nm (43400 Lcm mol ); IR: n˜ =3029, 2890, 1608,
[12] N. Miyaura, A. Suzuki, Chem. Rev. 1995, 95, 2457–2483.
ꢀ
1
[
13] a) C. Quinton, V. Alain-Rizzo, C. Dumas-Verdes, F. Miomandre, P. Aude-
bert, Electrochim. Acta 2013, 110, 693–701; b) K. Idzik, J. Soloducho, M.
Lapkowski, S. Golba, Electrochim. Acta 2008, 53, 5665–5669.
1
494, 1444, 1317, 1285, 1233, 1164, 1028, 945, 840, 807cm ; MS:
+
calcd for C H N O: 514.2853 [M+H] ; found: 514.2845; F =0.39
3
5
35
3
F
in CH CN; t=2.2 ns; E8 (C, CH Cl ) versus ferrocene: 0.02, 0.23,
3
2
2
[
14] a) Y. A. Skryshevskii, J. Appl. Spectrosc. 2002, 69, 726–731; b) J. H. Seo,
N. S. Han, H. S. Shim, S. M. Park, J. H. Kwon, J. K. Song, Chem. Phys. Lett.
0
.54 V.
2
010, 499, 226–230.
[15] G. A. Crosby, J. N. Demas, J. Phys. Chem. 1971, 75, 991–1024.
[16] C.-C. Chang, H. Yueh, C.-T. Chen, Org. Lett. 2011, 13, 2702–2705.
[
17] T. Pacze s´ niak, A. Sobkowiak, J. Mol. Catal. A 2003, 194, 1.
Acknowledgements
We thank Dr. R. Mꢀtivier and Dr. C. Allain for fruitful discussions
and J. Fromont for technical assistance. We thank the CNRS
and the Ministry of the French Research for funding the proj-
ect. This work has benefited from the facilities and expertise of
the Small Molecule Mass Spectrometry platform of IMAGIF
[18] M. Krej cˇ ik, M. Dan eˇ k, F. Hartl, J. Electroanal. Chem. Interfacial Electro-
chem. 1991, 317, 179–187.
[
19] C. Lambert, G. Nçll, Angew. Chem. Int. Ed. 1998, 37, 2107; Angew. Chem.
998, 110, 2239.
1
[20] a) H.-J. Yen, G. S. Liou, Chem. Commun. 2013, 49, 9797; b) H. Nakamura,
K. Kanazawa, N. Kobayashi, Chem. Commun. 2011, 47, 10064.
[
[
[
21] A. Beneduci, S. Cospito, L. La Deda, G. Chidichimo, Nat. Commun. 2013,
, 3105.
22] H. Niu, J. Cai, P. Zhao, C. Wang, X. Bai, W. Wang, Dyes Pigm. 2013, 96,
58–169.
23] a) D. Gu, G. Yang, Y. He, B. Qi, G. Wang, Z. Su, Synth. Met. 2009, 159,
497–2501; b) L. Chi, Y. Wu, X. Zhang, S. Ji, J. Shao, H. Guo, X. Wang, J.
(
Centre de Recherche de Gif—http://www.imagif.cnrs.fr).
5
1
Keywords: electrofluorochromism · fluorescence · molecular
modeling · protonation · redox chemistry · triphenylamine
2
Zhao, J. Fluoresc. 2010, 20, 1255–1265; c) B. Hu, X. Chen, Y. Wang, P. Lu,
Chem. Asian J. 2013, 8, 1144–1151.
24] K. Haav, J. Saame, A. Kꢅtt, I. Leito, Eur. J. Org. Chem. 2012, 2167.
25] A. Kutt, T. Rodima, J. Saame, E. Raamat, V. Maemets, I. Kaljurand, I. A.
Koppel, R. Y. Garlyauskayte, Y. L. Yagupolskii, L. M. Yagupolskii, E. Bern-
hardt, H. Willner, I. Leito, J. Org. Chem. 2011, 76, 391.
[
[
[
1] P. M. Beaujuge, J. R. Reynolds, Chem. Rev. 2010, 110, 268–320.
2] P. Audebert, F. Miomandre, Chem. Sci. 2013, 4, 575–584.
3] S. J. Yeh, C. Y. Tsai, H. C. Y., G.-S. Liou, S.-H. Cheng, Electrochem.
Commun. 2003, 5, 373–377.
4] a) C. Amatore, S. Arbault, Y. Chen, C. Crozatier, F. Lemaitre, Y. Verchier,
Angew. Chem. Int. Ed. 2006, 45, 4000; Angew. Chem. 2006, 118, 4104;
b) A. Meunier, O. Jouannot, R. Fulcrand, I. Fanget, M. Bretou, E. Karate-
kin, S. Arbault, M. Guille, F. Darchen, F. Lemaꢃtre, C. Amatore, Angew.
Chem. Int. Ed. 2011, 50, 5081–5084; Angew. Chem. 2011, 123, 5187–
[
[
[
[
26] H. Gampp, M. J, Maeder, C. J. Meyer, A. D. Zuberbꢅlher, Talanta 1985,
3
2, 95.
[
27] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R.
Cheeseman, J. A. Montgomery, Jr., T. Vreven, K. N. Kudin, J. C. Burant, J.
M. Millam, S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G.
Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K.
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O.
Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross, C.
Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J.
Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuma,
G. A. Voth, P. Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich,
A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K. Ra-
ghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J.
Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi,
R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayak-
kara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong, C.
Gonzalez, and J. A. Pople, Gaussian 03, Revision C.02, Gaussian, Inc.,
Wallingford CT, 2004.
5
190.
5] a) Y. Kim, E. Kim, G. Clavier, P. Audebert, Chem. Commun. 2006, 3612–
614; b) S. Seo, Y. Kim, Q. Zhou, G. Clavier, P. Audebert, E. Kim, Adv.
[
3
Funct. Mater. 2012, 22, 3556–3561; c) F. Miomandre, E. Lꢀpicier, S. Mun-
teanu, O. Galangau, J. F. Audibert, R. Mꢀallet-Renault, P. Audebert, R. B.
Pansu, ACS Appl. Mater. Interfaces 2011, 3, 690–696; d) Y. Kim, J. Do, E.
Kim, G. Clavier, L. Galmiche, P. Audebert, J. Electroanal. Chem. 2009, 632,
201.
[
[
6] F. Miomandre, R. B. Pansu, J. F. Audibert, A. Guerlin, C. R. Mayer, Electro-
chem. Commun. 2012, 20, 83–87.
7] C. Dumꢄs-Verdes, F. Miomandre, E. Lꢀpicier, O. Galangau, T. T. Vu, G. Cla-
vier, R. Mꢀallet-Renault, P. Audebert, Eur. J. Org. Chem. 2010, 2525–
2535.
[
[
8] Y. Hirao, A. Ito, K. Tanaka, J. Phys. Chem. A 2007, 111, 2951–2956.
9] a) S. Beauprꢀ, J. Dumas, M. Leclerc, Chem. Mater. 2006, 18, 4011–4018;
b) S.-H. Hsiao, G.-S. Liou, Y.-C. Kung, H.-J. Yen, Macromolecules 2008, 41,
[
28] N. M. O’Boyle, A. L. Tenderholt, K. M. Langner, J. Comput. Chem. 2008,
2
9, 839.
2
800–2808; c) G. Nursalim, Y. Chen, Polymer 2010, 51, 3187–3195; d) A.
Ito, D. Sakamaki, Y. Ichikawa, K. Tanaka, Chem. Mater. 2011, 23, 841–
50; e) C.-Y. Huang, C.-Y. Hsu, L.-Y. Yang, C.-J. Lee, T.-F. Yang, C.-C. Hsu,
C.-H. Ke, Y. O. Su, Eur. J. Inorg. Chem. 2012, 1038–1047.
8
Received: July 27, 2014
Published online on && &&, 0000
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
11
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
FULL PAPER
On–off–on–off: A triphenylamine (TPA)
derivative (see figure) sensible to oxida-
tion and protonation was designed and
synthesized. Its photophysical and elec-
trochemical properties were investigat-
ed. This compound leads to six redox or
acidic stable states with various colors
(yellow, green, blue, colorless). The
&
Fluorescence Switches
C. Quinton, V. Alain-Rizzo,*
C. Dumas-Verdes, F. Miomandre,
G. Clavier, P. Audebert
&
& – &&
Redox- and Protonation-Induced
Fluorescence Switch in a New
Triphenylamine with Six Stable Active
or Non-Active Forms
emission properties can also be modu-
lated with oxidation or protonation
(purple, cyan, green, no fluorescence).
&
&
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
12
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!