A novel bis(terpyridine) with π?conjugated phenyl viologen and its metallo- supramolecular polymers: Synthesis and electrochromism

Article abstract of DOI:10.1016/j.dyepig.2020.108251

A novel phenylene viologen functionalized bis(terpyridine) is synthesized and characterized with ¹HNMR and Maldi-tof-MS. This rod-like and π-conjugated molecule, 1,1'-[4'-(4-phenyl)-2,2:6′,2″- terpyridine-4,4′-bipyridine-1,1′-diium dichloride (

Full text of DOI:10.1016/j.dyepig.2020.108251

Dyes and Pigments 176 (2020) 108251
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Dyes and Pigments
journal homepage: http://www.elsevier.com/locate/dyepig
A novel bis(terpyridine) with πÀ conjugated phenyl viologen and its
metallo- supramolecular polymers: Synthesis and electrochromism
Yuchen Qian, Han Yang, Yuechuan Wang*
College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials and Engineering, Sichuan University, Chengdu, 610065, PR China
A R T I C L E I N F O
A B S T R A C T
A novel phenylene viologen functionalized bis(terpyridine) is synthesized and characterized with 1HNMR and
Maldi-tof-MS. This rod-likeþan2d π-Àconjugated molecule, 1,1’-[4’-(4-phenyl)-2,2:60,200- terpyridine-4,40-bipyridine-
1,10-diium dichloride (TPV 2Cl ), synthesized by Zincke reaction of 4’-(4-aminophenyl)-2,2:60,200-terpyridine
with 1,10-bis (2,4-dinitrophenyl)-4,40-bipyridine,1,10-diium dichloride, exhibited strong absorption and fluores-
cence in wide UV and visible wavelength range. It complexes with Fe- and Ru- ions and can self-assemble into
metallo-supramolecular polymers in solution, which can be coated on ITO-glass. The electrochemical charac-
teristics of TPVþ22ClÀ and its Fe-TPVþ2-BF4 supramolecular polymer in solution were studied with cyclic vol-
tammetry. Four different color states, colorless (transparent), purple, reddish brown and grayish green, were
observed in a cycle of redox reaction during the cyclic voltammetry scanning. A simple liquid electrochromic
device with the Fe-TPVþ2-BF4 supramolecular polymer film as working electrode, and with LiClO4 aqueous and
K3Fe(CN)6, was fabricated. It can be colored/bleached reversibly between purple and green-yellowish colors by
Keywords:
Bis(terpyridine)
Viologen
Metallo-supramolecular polymer
Electrochromism
switching the applied voltage from 0 to 0.8 V. The π-conjugation among the bis(terpyridine)s and the phenylene
viologen leads the subunits electronically and chemically connected. This interesting viologen functionalized bis
(terpyridine) dye will find applications in wide ranges.
1. Introduction
[7–12].
In designing electrochromic materials, in order to achieve multicolor
Molecular self-assembly is an essential and powerful tool for fabri-
cating molecular materials and molecular-based nanodevices [1]. The
coordination of transition metal ions with ligands on designed mole-
cules, such as bis(terpyridine)s, is a useful handle for molecular
self-assembly, especially when precisely placing the active components
into a molecular-based device or architecture is required. Bis(terpyr-
idine)s have been widely used as the binding modules of such molecular
devices for controlling light at molecular level, artificial species or sys-
tems for solar energy conversion, due to their high binding affinity to-
ward transition-metals, p-stacking ability, and their distinct
photophysical and electrochemical properties [2–6].
discoloration, combining two or more electro chromophores in one
molecule is an often adopted strategy, because a single chromophore can
rarely simultaneously exists in more than two different color states
[13–21]. Because viologen and bis(terpyridine) chromophores are
colored at different voltages in electrochromic reactions, and the bis
(terpyridine) can complex with different metals [22,23], the combina-
tion of viologen with bis(terpyridine) will lead to molecular materials
capable of showing multicolors by only tuning the applied potential.
There are a few studies on the bis(terpyridine)s with viologen motifs as a
pendent or a non-conjugated chromophore, such as the so called met-
alloviologen [24–27].
Viologens, i.e. 4,40-bipyridinium ions, are electrochromic dyes that
can undergo reversible one- and two-electron reductions. They have
been well studied and used for fabrication of electrochromic devices,
such as auto-dimming smart windows, anti-glare rear-view mirrors or
low power consumption displays, and as the building blocks for the
construction of nanosheets, charged covalent organic networks as well
We designed a new bis(terpyridine) dye, TPVþ2, in which the two
terminal terpyridines are linked and πÀ conjugated by a phenyl viologen
subunit. By complexation with transition metal ions TPVþ2 is capable of
self-assembling into metallo- supramolecular polymers (Scheme 1). Both
the bis(terpyridine) and the phenyl-viologen chromophores have been
well studied for their electrochromism: the color of bis(terpyridine)s-
* Corresponding author.
E-mail address: 1873843369@qq.com (Y. Wang).
https://doi.org/10.1016/j.dyepig.2020.108251
Received 28 November 2019; Received in revised form 27 January 2020; Accepted 28 January 2020
Available online 30 January 2020
0143-7208/© 2020 Elsevier Ltd. All rights reserved.

Y. Qian et al.
Dyes and Pigments 176 (2020) 108251
metal complex is the metal ion dependent, and the phenyl-viologen
shows deep green color at colored state. We report here the synthesis,
characterization, optical and the primary electrochromic properties of
this viologen functionalized bis(terpyridine) dye and its Fe-
supramolecular complex. The optical properties of Ru- supramolecular
complex are also reported for comparison.
ammonium hydroxide (75 mL, 25–28%) was slowly added in turn. The
reaction was carried out at 0 �C for 24 h. The crude product was
recovered by filtration, and washed once with water and then with
ethanol. It was finally recrystallized from ethanol and dried in vacuo to
get a dark brown solid 1.91 g, yield 18.3%. 1H NMR δH (400 MHz,
CDCl3): 7.37(dt, J ¼ 4.53, 6.95 Hz 2H), 7.90(td, J ¼ 1.51, 7.69 Hz 2H),
8.03–8.07(m, 2H), 8.35–8.5(m, 2H), 8.69(dd, J ¼ 7.74 Hz 2H), 8.75(s,
2H), 8.79(dd, J ¼ 8.46 Hz 2H).
2. Experimental section
2.2.2. Synthesis of 4’-(4-aminophenyl)-2,2:60,200- terpyridine (T2)
T1 (1.6 g, 4.5 mm), SnCl2 (5.35 g, 28 mmol) and hydrochloric acid
(40 mL, 36%–38%) were added in flask and reacted under reflux for 6 h.
Then the flask was cooled to room temperature and the product was
filtered. Appropriate amount of 10% NaOH aqueous solution then added
into the filtrate and stirred for 1 h. After filtration and washing with
water and then dried in vacuo, it give a brown solid 1.27 g, yield 79%.
1H NMR δH (400 MHz, CDCl3): 3.86(d, J ¼ 9.32 Hz, 2H), 6.87(d, J ¼
8.42 Hz, 2H), 7.41(ddd, J ¼ 1.06, 4.75, 7.42 Hz, 2H), 7.85(d, J ¼ 8.45
Hz, 2H), 7.94(td, J ¼ 1.75, 7.72 Hz, 2H), 8.73(d, J ¼ 7.91 Hz, 2H),8.76
(s, 2H), 8.77–8.81(m, 2H).
2.1. Materials and instruments
All commercially available chemicals and solvents were purchased
and used unless otherwise mentioned. 1,10-bis(2.4-dinitrophenyl)-4,40-
bibyridine-1,10-diium dichloride was synthesized by the reported pro-
cedures [28]. 1,4-Bis-(2,2’:60,200- terpyridine-40-yl) benzene (BTP) and
the Fe-BTP were synthesized as descripted in the supporting materials.
Instruments: Bruke AC-200 nuclear magnetic resonance instru-
ment; UV-3802S ultraviolet visible spectrophotometer, Unico
(Shanghai) Instrument Co, Ltd; CS350 electrochemical workstation,
Wuhan Kesite Instrument Co, Ltd; DC stabilized power supply;
FluoroMax-4 fluorescence spectrophotometer, France HORIBA; Agilent
HP5973 mass spectrometer for the high resolution matrix assisted laser
dissociation time-of-flight mass spectrometer (MALDI-TOF-MS).
2.2.3. Synthesis of 1,1’-[4’-(4-phenyl)-2,2:60,200-terpyridine-4,40-
bipyridine-101-diium dichloride (TPVþ22ClÀ )
T2 (1.2 g, 3.7 mmol) in ethanol (25 mL) and 1,1’-bis(2,4-dini-
trophenyl)-4,4′-bipyridine-1,1′-diium dichloride (0.86 g, 1.5 mmol) in
distilled water (26 mL) were mixed in flask and stirred under reflux for
70 h. After rotavap to remove the water and ethanol, the solid was
dissolve with a small amount of methanol, and then precipitated with
diethyl ether. By washed twice with diethyl ether and dried under
vacuo, it gave a red-brown solid product 1.97 g, the counter anions is
chloride ion, yield 57%. The samples for 1H NMR and HRMS
2.2. Synthesis of the viologen-conjugated bis(terpyridine) and the metallo-
supramolecular complex polymer
2.2.1. Synthesis of 4’-(4-nitrophenyl)-2,2:60,2’’ -terpyridine (T1)
p-Nitro benzaldehyde (3.78 g, 25 mmol), 10% aqueous sodium hy-
droxide solution (27.5 mL) and ethanol (125 mL) were added to a 500 ml
flask. Under magnetic stirring 2-acetylpyridine (6.65 g, 55 mmol) and
Scheme 1. Bis(terpyridine) and the metallo-supramolecular polymers.
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Y. Qian et al.
Dyes and Pigments 176 (2020) 108251
measurements were recrystallized from methanol and diethyl ether. 1H
NMR (400 MHz, (CD3)2SO): δH ppmÀ 1 ¼ 7.63 (dd, J ¼ 5.52, 6.83 Hz,
4H), 8.14 (dd, J ¼ 7.15, 15.27 Hz, 4H), 8.25 (d, J ¼ 8.35 Hz, 4H), 8.44
(d, J ¼ 8.35 Hz, 4H), 8.79(d, J ¼ 7.73 Hz, 4H), 8.83(d, J ¼ 4.14 Hz, 4H),
8.89 (s, 4H), 9.21 (d, J ¼ 6.42 Hz, 4H), 9.85(d, J ¼ 6.42 Hz, 4H). HRMS
(ESI): C52H36N8 calculated 772.3052, found 772.3051.
2.2.4. Synthesis of Fe-TPVþ2-BF4 supramolecular polymer
TPVþ2 2Cl- (169 mg, 0.2 mmol) was added in water (160 mL) and
refluxed under N2 for 0.5 h. Then ferrous acetate tetrahydrate (49 mg,
0.2 mmol) was added under stirring. The solution turned into a dark
purple immediately. It was further refluxed for 12 h, then cooled to room
temperature and filtered to remove trace solid. After addition of lithium
tetrafluoroborate 0.64 g to the filtration, the purple and flocculent
precipitate was formed and the solution gradually became clear. The
purple-black solid product was collected by centrifugation, then dried
under vacuo, TPVþ2-Fe-BF4, 148 mg, yield 68%.
Ru-TPVþ2-BF4 supramolecular polymer was similarly synthesized
with RuCl2(DMSO)4 (97 mg 0.2 mmol), yield 56%.
2.3. Preparation of Fe-and Ru-TPVþ2-BF4 film
The Fe-TPVþ2-BF4 or Ru-TPVþ2-BF4 film was prepared by the
following step: firstly, preparing 1.0 mg/mL solution of Fe-TPVþ2-BF4 in
acetonitrile, and then filtrated with a microporous membrane; secondly,
a 2 � 2 cm bare area on ITO glass sized 3 � 4 cm was taped with self-
adhesive tape and placed on a hot plate at 80 �C; thirdly about 2–4
mL of the Fe-TPVþ2-BF4 in acetonitrile solution was sprayed evenly onto
the bare area with a mini spray gun. The Fe-TPVþ2-BF4 film with size of
2 � 2 cm on ITO glass was obtained after peeling off the surrounding
protective tape.
Scheme 2. Syntheses of the viologen conjugated bis(terpyridine), TPVþ2 2Cl-.
2.4. Preparation of Fe-TPVþ2-BF4 device
�C. When the reaction was carried out under reflux almost no T1 product
was obtained. Yield could be further improved by extending reaction
time.
The device is assembled with the Fe-TPVþ2-BF4 film as working
electrode, 0.1 mol/L LiClO4 aqueous as electrolyte solution and 20 mg/
mL K3Fe(CN)6 as complementary material. The working area of the PV-
Fe-BF4 film was 2 � 2 cm with 0.2 mm thickness controlled by the
sealing strip.
T2 was synthesized by the reduction of T1 under mild condition as
the reported procedure [29]. Finally the TPVþ2 dichloride, TPVþ2 2Cl-,
was obtained by Zincke reaction of 4’-(4-aminophenyl)-2,2:60,200-ter-
pyridine with 1,10-bis(2,4-dinitrophenyl)-4,40-bipyridine-1,10- diium
dichloride. TPVþ2 2Cl- is soluble in methanol, DMSO and propylene
carbonate, but only slightly soluble in water and ethanol.
2.5. Electrochemical and electrochromic test
Spectroelectrochemical tests of Fe-TPVþ2-BF4 and Fe-BTPþ2-BF4 su-
pramolecular polymers were carried out in acetonitrile with LiClO4 as
the electrolyte, Pt as the counter electrode and Fe-TPVþ2-BF4 or Fe-
BTPþ2-BF4 as the working electrode, and cyclic voltammetrically scan-
ning between À 1.2 V and 1.5 V to obtain the redox curves.
The Ru- and Fe-TPVþ2-BF4 supramolecular polymers were prepared
in water by the complexation reaction of TPVþ2 2Cl- with the Ruþ2 or
Feþ2 salt at 1:1mol ratio, followed by treating with LiBF4 to replace the
ClÀ counter anions with BFÀ4 . The resultant Fe- or Ru- supramolecular
polymer complex is soluble in acetonitrile, but not in water, DMSO,
methanol and propylene carbonate.
3D- and 2D-fluorescence spectroscopy of TPVþ2 was recorded with
the solution of 0.06 g/L of TPVþ2 in DMSO by a fluorescence spectro-
photometer set at 5 nm slit width, and excitation wavelength in
250–500 nm, emission in 300–800 nm with 10 nm interval wavelength.
The matrix assisted laser desorption ionization-mass spectrometry
TPVþ2 was characterized by 1H NMR and high resolution mass
spectrometer (HRMS). All the H-atoms of TPV were assigned in the
spectra, as showed in Fig. 1a. Under the soft Maldi-tof-MS condition for
HRMS the molecular ion of the TVP, Mþ ¼ C52H37N8þ, with the m/z
calculated as 772.3052 was found as m/z ¼ 772.3051, as showed in
Fig. 1b. The other ions above the Mþ include those ions as Mþþ H2O,
Mþ Hþ and M þ Naþ.
(Maldi-tof-MS) was performed with
α-Cyano-4-hydroxycinnamic acid
(CHCA) as matrix to obtain the spectra in a linear mode.
The Fe-TPVþ2-BF4 supramolecular polymer was also checked with
Maldi-tof-MS. There is a region of wide m/z distribution beyond m/z ¼
2500 in the Maldi-tof-MS, as shown in the inset of Fig. S1. The emerged
peak at m/z around 3000-6000D can not be easily explained, because
the m/z values of ions in MS depend on the number of charges on the
ions, which in turn depends on the degree of ionization of the metallo-
supramolecular polymers. The detected ions in the ESM processes may
also contain some anions. For metallo-supramolecular polymer it is still
not clear whether the molecular weight can be directly determined by
Maldi-tof-MS [32,33]. The smooth thin film made with the
3. Results and discussion
3.1. Synthesis and characterization of TPVþ2 2Cl-, and its Fe- or Ru-
supramolecular polymers
The viologen conjugated bis(terpyridine), TPVþ22ClÀ , was synthe-
sized, as showed in Scheme 2. The building block T1 was prepared in
one-step by slightly modifying the reported two-step reaction proced-
ures [29–31] with improved product yield. We found that for our
one-step reaction to T1, the reaction temperature greatly affected the
product yield, and the optimal temperature for the reaction is about 0
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Y. Qian et al.
Dyes and Pigments 176 (2020) 108251
Fig. 1. a) 1H NMR and b) Maldi-tof-MS of TPVþ2 2Cl-.
Fig. 2. a) Pictures of powder and films Fe-/Ru-TPVþ2-BF4 metallo-supramolecular polymer and b) UV–Vis absorption spectra of TPVþ22ClÀ .
Fe-TPVþ2-BF4 metallo-supramolecular polymer solution on glass, as
depicted in Fig. 2a, is an indication of high molecular mass, because low
molecular mass substance, especially with rigid rod-like molecule, can
not form smooth thin film by its self.
absorption spectra of TPVþ22ClÀ in DMSO solution are showed in
Fig. 2b. The strong absorption band, with λ
278 nm and ε ¼ 5.58 �
104 dm3molÀ 1cmÀ 1, extended from UV to vimsiabx¼le region of 200–650 nm.
This wide range of absorption is quite characteristic in comparing with
the other bis-(terpyridine)s with viologen-like motifs that cut off ab-
sorption under 500 nm wavelength [24,34]. It is resultant of the long
The powder and films of the Fe-/Ru-TPVþ2-BF4 metallo-
supramolecular polymers are deep colored, as depicted in Fig. 2a. The
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Y. Qian et al.
Dyes and Pigments 176 (2020) 108251
shown in Fig. 4. In the 3D spectra the excitation wavelength sets at the
ordinate and emission wavelength at the abscissa, and the fluorescence
intensities were indicated by the color apertures. The 2D- luminescence
spectra were obtained by excitation at three specific wavelengths. From
Fig. 4, it can be seen that TPVþ22ClÀ is a fluorescent dye strongly
emitting fluorescent covering the entire visible range, from 330 nm to
750 nm, when excited by radiation from 250 nm to 475 nm. The rigid
structure of the TPVþ22ClÀ molecule makes its luminescence intensified.
The luminescence of the Fe- or Ru-TPVþ2 supramolecular polymer
complex is much weaker than TPVþ2, and their fluorescence properties
are still under studying.
3.2. Electrochemical and electrochromic behaviors of TPVþ22ClÀ and Fe-
TPVþ2-BF4 supramolecular
Fig. 3. UV–Vis absorption spectra of Fe-/Ru-TPVþ2-BF4 supramolecu-
lar polymer.
The electrochemical characteristics of TPVþ22ClÀ were studied with
cyclic voltammetry in DMSO solution containing LiClO4 as the electro-
lyte. Pt sheets were used both as the working and counter electrode
against the Ag/AgCl reference electrode. In the cyclic voltammetry
curve, Fig. 5, the two pairs of redox peaks comes from the redox of the
viologen subunit. The two oxidation peaks at À 0.41 V and À 0.13 V
correspond to the oxidation of zero valent TPV0 to the radical cation
TPV●þ1, and TPV●þ1 to TPVþ2, respectively. The reduction peaks at
À 0.37 V and À 0.87 V arise from TPVþ2 to TPV●þ1, and TPV●þ1 to TPV0,
respectively. During the cyclic voltammetry scanning, the Pt working
electrode, after reductive scanning to below À 0.37 V, was found to have
a thin layer of green-colored deposition, like the color of phenyl viol-
ogen at the colored state. This deposition came from the TPV●þ1 radical
cations that tend to dimerize in solution [8]. The dimers are less soluble
range of
π-conjugation through the electro-withdrawing phenylene
viologen unit. The absorption shoulder around 321 nm is composed of
the absorption of viologen and the pyridine ligand subunits of TPVþ2
.
The UV–Vis absorption spectra of the Ruþ2 or Fe-TPVþ2-BF4 complex
are showed in Fig. 3. The strong absorption bands at visible wavelength
range, with λmax¼494 nm (
ε
¼ 2.85 � 104molÀ 1dm3cmÀ 1) and λmax
¼
575 nm (
ε
¼ 2.67 � 104molÀ 1dm3cmÀ 1) for Ru-TPVþ2-BF4 and Fe-
TPVþ2-BF4 complex, respectively, come from the ligands complexed
with the metal ions, similar to the of Fe- and Ru-bis(terpyridine)s
complexes in absorption wavelength [2,23].
The 3D and 2D-fluorescence spectra of TPVþ22ClÀ were measured, as
Fig. 4. a) 3D-dimensional fluorescence spectra of TPVþ22ClÀ 1 in DMSO (the ordinate is the excitation wavelength and the abscissa is the emission wavelength); 2D-
luminescent spectra at b) fluorescence spectra exited with photons of b) 310 nm; c) 350 nm; d) 430 nm.
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Y. Qian et al.
Dyes and Pigments 176 (2020) 108251
These changes can be ascribed to the complexation of the TPVþ2 ligands
with metal ions, which makes the orbital energy of the viologen unit
lower, or more stable.
Fig. 6b is the images of the color changes of Fe-TPVþ2-BF4 film as the
working electrode of the electrochemical cell during the cyclic voltam-
metry scanning. At least four colors can be observed in a cycle of redox
reaction. The corresponding states of the chromophores are denoted.
A simple liquid electrochromic device with Fe-TPVþ2-BF4 supramo-
lecular polymer film as the working electrode, LiClO4 aqueous as elec-
trolyte,
was
fabricated
and
its
electrochromism
was
spectroelectrochemically studied, as showed in Fig. 7a. To reduce the
device driving potential K3Fe(CN)6 was added as the complementary
material. At 0 V, or without the applied potential, owing to the ab-
sorption at about 330 nm and at 575 nm, the supramolecular polymer
film on ITO glass is purple-colored. When a positive potential 1.2 V
applied it bleached to slight yellow-greenish owing to the oxidation of
Feþ2 to Feþ3 that leads to gradual disappearance of the absorption at
575 nm. When negative potential applied the color of the film changed
to brownish, depending on the potential applied, the more negative the
potential, the deeper the color, owing to formation of the greenish
radical cation TPV●þ1. Fig. 7b shows the structure and images of the
color changes. More electrochromic properties are still under study and
will be reported elsewhere.
Fig. 5. Cyclic voltammetry curve of TPVþ22ClÀ (0.1 mol/L LiClO4/DMSO so-
lution as electrolyte).
because of their rigid and conjugated structure.
The electrochemical redox reactions of Fe- TPVþ2-BF4 supramolec-
ular polymer were similarly studied with cyclic voltammetry in aceto-
nitrile with LiClO4 as the electrolyte, and the Fe-TPVþ2-BF4 film sprayed
on an ITO glass as the working electrode and a Pt sheet as the counter
electrode, against the Ag/AgCl reference electrode. The cyclic voltam-
metry curve is shown in Fig. 6, together with that of Fe-BTP for com-
parison [23]. By comparing the two cyclic voltammetry curves, it can be
seen that the cyclic voltammetry curve of Fe-TPVþ2-BF4 film is
composed of the two redox reactions of TPVþ2 unit and Feþ2 ions. The
two peaks at 1.09 V and 0.75 V come from the oxidation of Feþ2 to Feþ3
and the reduction of Feþ3 to Feþ2, respectively. The two peaks at À 0.46
and À 0.23 V arise from the oxidation of the TPVþ2 to TPV●þ1, and
TPV●þ1 to TPVþ2, respectively. The reductions of TPVþ2 to TPV●þ1 and
further reduction to TPV0 are included in the wide peak that started at
about À 0.2 V, centered at À 0.63 V and ended at about À 0.9 V. From
Figs. 5 and 6, it can be calculated that the onset of the oxidation peak for
the TPV●þ1 fromTPV0 is about À 0.81 V and À 0.53 V for the supramo-
lecular polymer and for TPVþ2, respectively, while the onset of reduc-
tion of TPVþ2 to TPV●þ1, for either the supramolecular polymer or
TPVþ2 is about À 0.2 V. In other words, while the lowest unoccupied
molecular orbital energy, ELUMO, for either TPV●þ1 of supramolecular
polymer or of the bis(terpyridine) does not change much, the highest
occupied molecular orbital energy, EHOMO, of TPV●þ1 decreased about
The electrochemical and electrochromic characteristics of Ru-
TPVþ2-BF4 are in some way similar to Fe-TPVþ2-BF4 supramolecular
polymer, and are still under studying.
4. Conclusion
A novel bis(terpyridine) including π-conjugated phenylene viologen
is synthesized and studied. It strongly absorbs photons and emits fluo-
rescence in wide UV and visible wavelength range. It complexes with
transition metal ions and self-assembles into metallo-supramolecular
polymers in solution, which can be sprayed on ITO-glass. The Fe-
TPVþ2-BF4 supramolecular polymer exhibited electrochromic multi-
colors, depending on the metal ions coordinated and potentials applied.
The π-conjugation among the bis(terpyridine)s and the phenylene viol-
ogen makes these subunits electronically and chemically connected that
the optical absorption of the coordinated ligands redshifted and the
oxidation potential of the viologen unit decreased. This interesting
viologen functionalized bis(terpyridine) dye will find applications in
wide ranges.
0.81–0.53 ¼ 0.28 V for the supramolecular polymer relative to TPVþ2
.
Fig. 6. a) Cyclic voltammetry curve of Fe-TPVþ2-BF4 (purple) and Fe-bis(terpyridine) complex (Fe-BTP, blue) in acetonitrile with LiClO4 as electrolyte; b) Images of
the Fe-TPVþ2-BF4 film color changes in cyclic voltammetry scanning, denoted with the corresponding states. (For interpretation of the references to color in this
figure legend, the reader is referred to the Web version of this article).
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Dyes and Pigments 176 (2020) 108251
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Structure of Fe-TPVþ2-BF4 supramolecular polymer and Images of electro-
chromic device colour changes. (For interpretation of the references to color in
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~
~
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Declaration of competing interest
[19] Moon HC, Kim CH, Lodge TP, Frisbie CD. Multicolored, low power, flexible
electrochromic devices based on ion gels. ACS Appl Mater 2016;89:6252–60.
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The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
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CRediT authorship contribution statement
Yuchen Qian: Conceptualization, Data curation. Han Yang:
Conceptualization, Data curation. Yuechuan Wang: Methodology,
Writing - original draft.
[23] Yang H, Zhang Y, Qian Y, Wang Y. Synthesis of metallo-supramolecular polymers
and their multicolor electrochromic devices. Sci Sin Chim 2018;48:743–50.
[24] Zhang CF, Liu A, Chen M, Nakamura C, Miyake J, Qian DJ. Interfacial self-
assembly of metal-mediated viologen-like coordination polyelectrolyte hybrids of
the bisterpyridine ligand and their optical, electrochemical, and electrochromic
properties. ACS Appl Mater Interfaces 2009;1:1250–8.
Acknowledgment
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Sparr E, Tocher DA, Zehnder M, Zimmermann Y. Development of supramolecular
structure through alkylation of pendant pyridyl functionality. J Chem Soc Dalton
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This work is partly supported by the Project of State Key Laboratory
of Polymer Materials Engineering (Sichuan University).
�
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Appendix A. Supplementary data
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Photoinduced processes in dyads and triads containing a ruthenium(II) – bis
(terpyridine) photosensitizer covalently linked to electron donor and acceptor
groups. Inorg Chem 1991;30:4230–8.
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.dyepig.2020.108251.
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