Multi-color electrochromism from coordination nanosheets based on a terpyridine-Fe(ii) complex

Article abstract of DOI:10.1039/c9dt02980j

A metal complex nanosheet was synthesized by the liquid-liquid interface self-assembly method from a star-shaped ligand of tris[4-(4′-2,2′:6′,2′′-terpyridyl)-phenyl]amine in organic solvents and metal ion Fe(ii) in water solution. The as-prepared nanoshee

Full text of DOI:10.1039/c9dt02980j

Dalton
Transactions
View Article Online
View Journal | View Issue
PAPER
Multi-color electrochromism from coordination
nanosheets based on a terpyridine-Fe(II) complex†
Cite this: Dalton Trans., 2019, 48,
15121
Yu Kuai,a Weijun Li, a Yujie Dong,*a Wai-Yeung Wong, *b Shuanma Yan,a
a
Yuyu Daia and Cheng Zhang
*
A metal complex nanosheet was synthesized by the liquid–liquid interface self-assembly method from a
star-shaped ligand of tris[4-(4’-2,2’:6’,2’’-terpyridyl)-phenyl]amine in organic solvents and metal ion Fe(II)
in water solution. The as-prepared nanosheet possessed excessively smooth morphology with a thickness
of hundreds of nanometers. Adhering to an ITO glass, the nanosheet showed noticeable electrochromism
from purplish red at 0 V to orange-yellow at 1.4 V and green at 1.6 V. Besides, the nanosheet exhibited
outstanding stability with the optical contrast maintained at almost 100% of its original electrochemical
activity over 500 cycles. The liquid–liquid interface self-assembly method was proven to be promising to
prepare a polymeric metal complex for potential electrochromic applications.
Received 20th July 2019,
Accepted 16th September 2019
DOI: 10.1039/c9dt02980j
rsc.li/dalton
These nanosheets were produced by liquid–liquid interfacial
synthesis with an aqueous solution of metal ions and an
Introduction
Electrochromic materials have been investigated extensively in organic solution of ligands. Taking advantage of the flexibility
the past decades due to their important potential applications in ligand design and variety of metal ions, the desired poly-
in flat panel displays, smart windows, reflecting mirrors, enzy- meric metal complexes could be easily achieved as coordi-
matic skin patches, and so on.1–9 In comparison with in- nation nanosheets by self-assembly from a liquid–liquid
organic compounds,10–13 conjugated polymers possess plenti- interface.
ful and variable colors as well as fast color switching times
2,2′:6′,2″-Terpyridine has been widely investigated as a
and thus have attracted increasing attention in the current ligand for d-block metal ions owing to its strong electron
electrochromic research.14–18 However, the relatively poor elec- affinity; this moiety can be used to prepare highly stable com-
trochromic stability of most of the conjugated polymers has plexes, supramolecular coordination compounds or polymers
become a key critical defect for their future applications.19 with interesting optical, electronic, and magnetic
Metal complexes have more stable electrochromic properties, properties.29,31–33 With these characteristics, it has also been
and their electrochromic properties are tunable via changing applied in the construction of coordination nanosheets.34–36
the metals and ligands, which make the polymeric metal com-
plexes capable of acting as promising electrochromic materials (TPABT) consisting of one central core of triphenylamine and
for future practical applications.20–24
three arms of bithiophene and demonstrated the multi-color
Recently, we reported a star-shaped thiophene derivative
The polymeric electrochromic films are usually prepared by electrochromism of pTPABT derived from the oxidative states
electropolymerization or spin-coating on an ITO glass. of the triphenylamine and quaterthiophene groups.16 In this
Recently, coordination nanosheets, i.e., a class of two-dimen- work, we designed and synthesized a star-shaped molecule tris
sional (2D) materials featuring metal complex motifs were uti- [4-(4′-2,2′:6′,2″-terpyridyl)-phenyl]amine (TPA-YPY) with triphe-
lized by Nishihara and co-workers as electrochromic films.25–29 nylamine as the central core and 2,2′:6′,2″-terpyridine as the
peripheral arms (Fig. 1), aiming to achieve multiple electro-
chromic colors. We used the liquid–liquid interface self-assem-
aState Key Laboratory Breeding Base of Green Chemistry Synthesis Technology,
College of Chemical Engineering, Zhejiang University of Technology,
Hangzhou 310014, P. R. China. E-mail: dongyujie@zjut.edu.cn, czhang@zjut.edu.cn
bDepartment of Applied Biology & Chemical Technology, The Hong Kong
Polytechnic University, Hung Hom, Hong Kong, P. R. China.
E-mail: wai-yeung.wong@polyu.edu.hk
bly method (Fig. 2b) to obtain the terpyridine-Fe(II) complex
nanosheets, which were generated at the interface between the
dichloromethane (DCM) solution of TPA-TPY and the aqueous
solution of Fe(BF4)2. After applying different voltages, multi-
color electrochromism in the electrolyte solution containing a
three-compartment system was observed for the obtained
nanosheet film, which showed excellent electrochromic stabi-
†Electronic supplementary information (ESI) available. See DOI: 10.1039/
c9dt02980j
This journal is © The Royal Society of Chemistry 2019
Dalton Trans., 2019, 48, 15121–15126 | 15121

View Article Online
Paper
Dalton Transactions
of nanosheets was measured with a DEKTAK-XT profilometer.
NMR was carried out with ANANCE III(500M). MS was carried
out with SOLANX 70 FT-MS.
Synthesis
Synthesis of bis(4-formylphenyl)phenylamine. First, 10 ml
(0.10 mol) of phosphorus(V) oxychloride was added dropwise
to 8.0 ml (0.10 mol) of N,N-dimethylformamide at 0 °C. After
10 min, the reaction mixture was curdled, and 2.0
g
(8.2 mmol) of triphenylamine was added. The reaction mixture
was heated up to 70 °C and stirred for 12 h. After cooling
down, the reaction mixture was poured into 100 ml of water at
0 °C and extracted with dichloromethane. The organic phase
was dried by magnesium sulfate and evaporated. The crude
product was purified by column chromatography on a silica
gel with ethyl acetate/hexane (1 : 3, v/v) to yield a yellow solid
Fig. 1 The synthesis route of TPA-TPY.
1
(1.6 g, 80%). H NMR (400 MHz, CDCl3) δ 9.92 (s, 2H), 7.80 (d,
J = 8.7 Hz, 4H), 7.42 (t, J = 7.8 Hz, 2H), 7.29 (m, 1H), 7.21 (m,
6H). MALDI FT-ICR-MS (mass m/z): 302.1186 [M+ + H].
Synthesis of tris(4-formylphenyl)amine. Ten ml (0.10 mol)
of phosphorus(V) oxychloride was added dropwise to 8.0 ml
(0.10 mol) of N,N-dimethylformamide at 0 °C. After 10 min,
the reaction mixture was curdled, and 2.0 g (8.2 mmol) of bis
(4-formylphenyl)phenylamine was added. The reaction mixture
was heated up to 70 °C and stirred for 12 h. After cooling
down, the reaction mixture was poured into 100 ml of water at
0 °C and extracted with dichloromethane. The organic phase
was dried by magnesium sulfate and evaporated. The crude
product was purified by column chromatography on a silica
gel with ethyl acetate/hexane (1 : 4) to yield an orange-yellow
1
solid (1.0 g, 50%). H NMR (400 MHz, DMSO) δ 9.95 (s, 3H),
7.92 (d, J = 8.6 Hz, 6H), 7.29 (d, J = 8.5 Hz, 6H). MALDI
FT-ICR-MS (mass m/z): 330.1143 [M+ + H].
Fig. 2 (a) The chemical structure of ligand TPA-TPY. (b) The liquid–
liquid interface self-assembly method and the chemical structure of the
terpyridine-Fe(II) complex nanosheet.
Synthesis of tris[4-(4′-2,2′:6′,2″-terpyridyl)-phenyl]amine
(TPA-TPY). Tris(4-formylphenyl)amine (0.20 g 0.60 mmol) and
2-acetylpyridine (0.50 g, 4.1 mmol) were stirred in tetrahydro-
furan (30 ml), followed by the addition of potassium hydroxide
(0.50 g, 8.9 mmol) and ammonium hydroxide (30 ml). After
stirring for 72 h at room temperature, the greyish-green solid
was precipitated. The precipitate was filtered and washed
using tetrahydrofuran and then, the crude product was puri-
fied by recrystallization to yield an orange solid (0.10 g, 17%).
1H NMR (400 MHz, CDCl3) δ 8.79 (s, 6H), 8.77 (d, J = 9.2 Hz,
6H), 8.71 (d, J = 7.8 Hz, 6H), 7.91 (m, 12H), 7.38 (m, 12H).
MALDI-TOF MS (mass m/z): 940.5 [M+ + H].
lity with optical contrast remaining nearly unchanged after
500 cycles. Furthermore, a solid-state electrochromic device
using the terpyridine-Fe(II) complex nanosheet as the electro-
chromic layer was fabricated to simulate practical applications.
Experimental
Materials and instrumentation
Synthesis of coordination nanosheet. A 0.10 mM solution of
Reagents and solvents used in the synthesis and characteriz- TPA-TPY was prepared by dissolving 0.93 mg (0.0010 mmol)
ation were purchased from J&K, Aladdin and Energy Chemical, TPA-TPY in 10 ml CH2Cl2. The solution (2.0 ml) was poured
and used without further purification.
into a beaker of 10 ml (the cross-sectional area is about
SEM was carried out with Nova NANOSEM 450. The electro- 18.1 cm2) and then, water (2.0 ml) was added to cover the
chemical properties and long-term stability measurements organic phase to form the interface. Next, 2.0 ml of aqueous
were performed in a three-compartment system containing solution of Fe(BF4)2·6H2O (50 mM) was added slowly into the
0.1 M Bu4NClO4 in acetonitrile solution as the electrolyte on a aqueous phase. The film emerged at the interface after 3 days.
CHI660C electrochemical analyzer. UV-vis spectra, optical con- Pure dichloromethane replacing the organic phase by an injec-
trast and switching time measurements were recorded on a tor was the same as the aqueous phase replaced by pure water.
Shimadzu UV-1800 UV-vis spectrophotometer. The thickness The film was fished out by an indium tin oxide (ITO) glass.
15122 | Dalton Trans., 2019, 48, 15121–15126
This journal is © The Royal Society of Chemistry 2019

View Article Online
Dalton Transactions
Paper
Results and discussion
The star-shaped TPA-TPY molecule was synthesized according
to a method reported in the literature.29 The nanosheets were
obtained at the liquid–liquid interface between the CH2Cl2
solution of TPA-TPY and aqueous Fe(BF4)2 and were deposited
onto an ITO glass (Fig. 3a). The thickness of the nanosheets
for the reaction time of 5 days was measured to be approxi-
mately 55 nm (Fig. 3b). Interestingly, we found that the exterior
color of the nanosheets gradually deepened with the extension
of the standing time, and their thickness increased to ∼70 nm
after 6 days (Fig. S8†), ∼90 nm after 7 days (Fig. S8†) and
∼105 nm after 8 days (Fig. S8†). When we measured their UV-
vis absorption spectra, all of the nanosheets with different
thicknesses displayed similar characteristics with two typical
absorption bands at ∼400 nm and 580 nm (Fig. S1†). The
results were consistent with those of the reported Fe2+-terpyri-
dyl coordination compounds,30 indicating the successful
preparation of the nanosheets through the self-assembly of
Fe2+ metal ions and the TPA-TPY ligand molecule. The IR spec-
trum (Fig. S4†) shows that the peak at 1583 cm−1, which
belongs to the CvC stretching vibration of TPA-TPY, shifts to
1594 cm−1 for the nanosheet, indicating that the terpyridyl
Fig. 4 The SEM images of body (a) and edge (b and c) of the nanosheet
on ITO glass. (d) The histogram of EDS by contrasting N and Fe.
ligand coordinated to the metal ions. In addition, the broad
− 30
peak around 1100 cm−1 should be attributed to BF4
.
We also used scanning electron microscopy (SEM) to evalu-
ate the morphology of the nanosheets and found that the
obtained nanosheets exhibited excessively smooth surface
morphology (Fig. 4a). As shown in Fig. 4b and c, the obvious
multi-layer sheet structure from the edge of the nanosheets
indicates their layer growth model, which results in increased
thickness with a static standing time. Energy dispersive spec-
troscopy (EDS) showed that the atomic percentages of N and
Fe were 2.37% and 0.46%, respectively (Table S1†). The calcu-
Fig. 5 Cycle voltammogram curve of the nanosheet.
lated ratio of N/Fe (5.2/1) was close to the ideal ratio of 6.6/1 in applied voltage was set within 0–1.6 V at a scanning rate of
the metal complex structure of the nanosheets (Fig. 2b), 0.1 V s−1. As shown in Fig. 5, there are two obvious reversible
further indicating that the obtained nanosheets self- redox peaks with the oxidation peaks at 1.35 V and 1.49 V and
assembled through the coordination between metal ions Fe2+ the corresponding reduction peaks at 0.97 V and 1.27 V.
and the ligand molecule TPA-TPY.
Moreover, there is a weak oxidation peak under ∼0.95 V, which
Cyclic voltammetry of the nanosheets (8 days about is assigned to the doped or adhered TPA-TPY molecules
105 nm) on the ITO glass was carried out in a solution of according to the measured CV curves at the same experimental
acetonitrile with 0.1 M Bu4NClO4 as the electrolyte, and the conditions (Fig. S2†). Considering the molecular structure of
the nanosheets and the results reported in the literature, the
two main redox peaks should be derived from the oxidation/
reduction behaviors of coordinated Fe(II)-terpyridine
(1.35/0.97 V) and central triphenylamine group (1.49/1.27 V),
which might result in multi-color electrochromism for the
nanosheets.
The electrochromic properties of the nanosheets were
measured by a spectroelectrochemical experiment in a 0.1 M
tetrabutylammonium hexafluorophosphate (TBAP)/acetonitrile
solution. As shown in Fig. 6, the nanosheet displays a purplish
red color with the maximum absorption peak at 580 nm at its
neutral state under 0 V. In comparison with the result for its
Fig. 3 (a) The nanosheet deposited onto ITO glass from the liquid–
liquid interface between 0.1 mM TPA-TPY in CH2Cl2 and 50 mM
ligand TPA-TPY (375 nm in Fig. S3†), the large redshift of
nearly 50 nm of the nanosheet should be mainly attributed to
aqueous Fe(BF4)2. (b) The thickness of the nanosheet with the reaction
time for 5 days.
This journal is © The Royal Society of Chemistry 2019
Dalton Trans., 2019, 48, 15121–15126 | 15123

View Article Online
Paper
Dalton Transactions
Fig. 6 UV-vis spectra of the nanosheet with applied potential from 0 V
to 1.6 V in a solution of acetonitrile containing 0.1 M Bu4NClO4. Inset:
The color of nanosheet (∼1.1 cm2) with applied potentials at 0 V, 1.4 V
and 1.6 V.
Fig. 7 (a) Optical contrast of the nanosheet switching electrified at 0 V
and 1.4 V at 580 nm. (b) Stability of optical contrast of the nanosheet
over 3500 s at 580 nm. (c) Response time of coloring. (d) Response time
of discoloring.
the metal-to-ligand charge transfer (MLCT) band of the co-
ordinated Fe(II)-terpyridine group.30 When the applied poten-
tials were changed gradually from 0 V to 1.4 V, the absorbance
at 580 nm decreased and even disappeared at last. At the same The coloring times of nanosheets with the thicknesses of 55 nm
time, the absorbance at 421 nm rose gradually, which was (5 days), 70 nm (6 days), 91 nm (7 days) and 106 nm (8 days) were
accompanied by a color change from purplish red to orange- 0.7 ( 0.2) s, 0.5 ( 0.1) s, 0.6 ( 0.1) s and 0.6 ( 0.1) s, respect-
yellow. This transformation of the absorbance spectra was very ively; moreover, their discoloring times were 0.75 ( 0.25) s, 0.5
similar to that of the reported coordinated Fe(II)-terpyridine ( 0.1) s, 0.5 ( 0.1) s and 0.5 ( 0.1) s, respectively, which indi-
group, indicating that the redox peak at 1.35/0.97 V should be cated that the switching time of the nanosheets is indepen-
attributed to the oxidation/reduction of the coordinated Fe(II)- dent of the thickness (in the current thickness range of
terpyridine group in our nanosheets. By further enhancing the 55–106 nm). In addition, the coloration efficiency (CE) was cal-
applied potential on the nanosheets from 1.4 V to 1.6 V, a new culated with the equation CE = ΔOD/Qd, and ΔOD = log(Tc/Tb),
peak with λmax at ∼780 nm emerged, which was accompanied where Tc is the transmittance of the oxidized state, Tb is the
by an additional color change from orange-yellow to green. transmittance of the neutral state, and Qd is the injected elec-
According to the reported literature data, this absorption band tronic charge in unit area. The CE values of the nanosheets of
was consistent with that of the oxidative triphenylamine 5 days, 6 days, 7 days and 8 days were 12.84 cm2 C−1
,
group, demonstrating that the redox peak at 1.49/1.27 V 29.29 cm2 C−1, 73.61 cm2 C−1 and 141.72 cm2 C−1, respectively,
should be from the oxidation/reduction of the triphenylamine which indicated that the CE value increased along with the
group in the nanosheets. It is obvious that the redox activity of increased thickness. Besides, the CE value is common to that
our nanosheets consisted of two oxidation/reduction processes of other electrochromic materials that have been reported.18,37
from the coordinated Fe(II)-terpyridine and triphenylamine The nanosheets monitored at 580 nm also exhibited good
groups, respectively, and this endowed the nanosheets with a stability with the optical contrast almost undiminished over
multi-color electrochromism behavior from purplish red to 500 cycles, which corresponded to the redox behavior of the
orange-yellow and green.
coordinated Fe(II)-terpyridine group. The green color electro-
The optical contrast and switching time were also tested chromism, which was observed at the higher applied potential
under a repeated step potential between 0 V and 1.4 V of 1.6 V and should be attributed to the redox behavior of the
with a residence time of 5 s. As shown in Fig. 7, for the fabri- central triphenylamine group, disappeared after several cycles
cated nanosheets (8 days, about 105 nm) monitored at with much worse electrochromic stability. This indicated that
580 nm, the optical contrast is measured to be 22.3%. The the coordinated Fe(II)-terpyridine complex part in our
switching time, which is defined as the time required to nanosheets possessed much better electrochromic stability
achieve 95% of the full switch of the transmittance or color, than the organic triphenylamine group part. Though the
was estimated to be 0.5 s for coloring and 0.4 s for discoloring. optical contrast was not large enough, the fast switching time
The fast switching time of the nanosheets was close to the and excellent electrochromic stability made the metal complex
reported data of electrochromism for polymers and obviously capable of becoming a promising candidate material system
superior to those of electrochromism for inorganic oxides. The for electrochromic displays.
switching times of the nanosheets with different thicknesses
As shown in Fig. 8(a), we fabricated a solid-state electro-
were also tested under a repeated step potential between chromic device by using the nanosheet (∼1.9 cm2) as the elec-
0 V and 1.4 V with a residence time of 5 s (Fig. S5 and S6†). trochromic layer. The solidified electrolyte composed of
15124 | Dalton Trans., 2019, 48, 15121–15126
This journal is © The Royal Society of Chemistry 2019

View Article Online
Dalton Transactions
Paper
time with 2.1 s for coloring and 0.3 s for discoloring and could
maintain excellent stability with almost invariable optical con-
trast over 500 cycles. This work demonstrates that the 2D poly-
meric metal complexes as nanosheets are capable of display-
ing multi-color electrochromism; moreover, their structural
flexibility and variety provide prospects for a fast electrochro-
mic switching speed close to that of polymers and excellent
electrochromic stability potentially comparable to that of in-
organic oxides.
Conflicts of interest
There are no conflicts to declare.
Fig. 8 (a) The structure of the solid-state device. (b) The color of the
solid-state device at 0 V, 2.2 V and 3.4 V. (c) UV-vis spectrum of the
solid-state device applied potential from 0 V to 3.4 V.
Acknowledgements
We are grateful for supports from projects funded by Zhejiang
Provincial Natural Science Foundation of China (LY19E030006,
LQ19E030016, LY17E030001), Natural Science Foundation of
PMMA and LiClO4 was sandwiched by two ITO glasses: one China (51603185, 51673174), Hong Kong Research Grants
was blank ITO and the other one regarded as the working elec- Council (PolyU 153051/17P) and The Hong Kong Polytechnic
trode was adhered to the nanosheet. The device color changed University (1-ZE1C). W.-Y. W. also thanks the support from the
from purplish red to orange-yellow (Fig. 8b) as the applied Endowed Professorship from Ms Clarea Au (847S).
potential was changed from 0 V to 2.2 V. At the same time, the
absorbance at 580 nm decreased and that of 421 nm rose
gradually, which was attributed to the MLCT band of the co-
ordinated Fe(II)-terpyridine group (Fig. 8c). When the applied
Notes and references
potential changed from 2.2 V to 3.4 V, the device color further
changed from orange-yellow to green (Fig. 8b) with a new peak
emerging at ∼780 nm, which was assigned to the oxidation/
reduction of the triphenylamine group (Fig. 8c). The changes
in colors and UV-vis spectra were similar to those measured in
the system of the electrochemical cell although the applied
potential values were different. The switching time of the
solid-state device was also tested under a repeated step poten-
tial between 0 V and 2.2 V with a residence time of 5 s
(Fig. S7†). The switching time of the solid-state device was esti-
mated to be 1 s for coloring and 0.9 s for discoloring, which
indicated that the switching time of the nanosheet with the
solid electrolyte was not different from that in the electrolyte
solution. It is obvious that the liquid–liquid interface self-
assembly method has been proven to be really practical for
preparing a polymeric metal complex film for electrochromic
applications.
1 P. M. Beaujuge and J. R. Reynolds, Chem. Rev., 2010, 110,
268.
2 A. C. Grimsdale, K. L. Chan, R. E. Martin, P. G. Jokisz and
A. B. Holmes, Chem. Rev., 2009, 109, 897.
3 A. L. Dyer, M. R. Craig, J. E. Babiarz, K. Kelly and
J. R. Reynolds, Macromolecules, 2010, 43, 4460.
4 A. A. Argun, P. H. Aubert, B. C. Thompson,
I. Schwendeman, C. L. Gaupp, J. Hwang, N. J. Pinto,
D. B. Tanner, A. G. MacDiarmid and J. R. Reynolds, Chem.
Mater., 2004, 16, 4401.
5 V. K. Thakur, G. Q. Ding, J. Ma, P. S. Lee and X. H. Lu, Adv.
Mater., 2012, 24, 4071.
6 L. B. Groenendaal, G. Zotti, P. H. Aubert, S. M. Waybright
and J. R. Reynolds, Adv. Mater., 2003, 15, 855.
7 A. W. Lang, Y. Y. Li, M. D. Keersmaecher, D. E. Shen,
A. M. Osterholm, L. Berglund and J. R. Reynolds,
ChemSusChem, 2018, 11, 854.
8 L. R. Savagian, A. M. Österholm, D. E. Shen,
D. T. Christiansen, M. Kuepfert and J. R. Reynolds, Adv.
Opt. Mater., 2018, 6, 1800594.
9 H. Kai, W. Suda, S. Yoshida and M. Nishizawa, Biosens.
Bioelectron., 2019, 123, 108.
Conclusions
We prepared coordination nanosheets based on a terpyridine-
Fe(II) complex via the liquid–liquid interface self-assembly 10 X. J. Lv, J. W. Sun, B. Hu, M. Ouyang, Z. Y. Fu, Z. Y. Wang,
method. The nanosheets on an ITO glass exhibited an electro- G. F. Bian and C. Zhang, Nanotechnology, 2013, 24, 1.
chromism behavior with a multi-color change from purplish 11 Y. D. Shi, Y. Zhang, K. Tang, J. W. Cui, X. Shu, Y. Wang,
red to orange-yellow and green with the gradually increasing
voltage. Furthermore, the nanosheets showed a fast response
J. Q. Liu, Y. Jiang, H. H. Tan and Y. C. Wu, Chem. Eng. J.,
2019, 355, 942.
This journal is © The Royal Society of Chemistry 2019
Dalton Trans., 2019, 48, 15121–15126 | 15125

View Article Online
Paper
Dalton Transactions
12 K. Hoshino, M. Okuma and K. Terashima, J. Phys. Chem. C, 26 R. Sakamoto, K. Hoshiko, Q. Liu, T. Yagi, T. Nagayama,
2018, 122, 22577.
S. Kusaka, M. Tsuchiya, Y. Kitagawa, W. Y. Wong and
13 D. Dong, W. W. Wang, A. Barnabe, L. Presmanes,
H. Nishihara, Nat. Commun., 2015, 6, 1.
A. Rougier, G. Dong, F. Zhang, H. Yu, Y. C. He and 27 T. Pal, T. Kambe, T. Kusamoto, M. L. Foo, R. Matsuoka,
X. G. Diao, Electrochim. Acta, 2018, 267, 277.
R. Sakamoto and H. Nishihara, ChemPlusChem, 2015, 80,
14 B. Schmatz, Z. B. Yuan, A. W. Lang, J. L. Hernandez,
1255.
E. Reichmanis and J. R. Reynolds, ACS Cent. Sci., 2017, 3, 28 A. Rapakousiou, R. Sakamoto, R. Shiotsuki, R. Matsuoka,
961.
U. Nakajima, T. Pal, R. Shimada, A. Hossain, H. Masunaga,
S. Horike, Y. Kitagawa, S. Sasaki, K. Kato, T. Ozawa,
D. Astruc and H. Nishihara, Chem. – Eur. J., 2017, 23, 8443.
29 T. Tsukamoto, K. Takada, R. Sakamoto, R. Matsuoka,
R. Toyoda, H. Maeda, T. Yagi, M. Nishikawa, N. Shinjjo,
S. Amano, T. Iokawa, N. Ishibashi, T. Oi, K. Kanayama,
R. Kinugawa, Y. Koda, T. Komura, S. Nakajjima,
R. Fukuyama, W. X. Zhang, R. C. Han, W. Y. Liu,
T. Tsubomura and H. Nishihara, J. Am. Chem. Soc., 2017,
139, 5359.
15 W. J. Li, L. Chen, Y. Y. Pan, S. M. Yan, Y. Y. Dai, J. Liu,
Y. Yu, X. X. Qu, Q. B. Song, M. Ouyang and C. Zhang,
J. Electrochem. Soc., 2017, 164(4), E84.
16 Y. J. Dong, F. F. Luo, L. Chen, F. Y. Yuan, Y. J. Hou, W. J. Li,
S. M. Yan, Y. Y. Dai, M. Ouyang and C. Zhang, Phys. Chem.
Chem. Phys., 2018, 20, 12923.
17 S. M. Yan, W. J. Li, Y. Y. Dai, M. Ouyang, Y. J. Zhang and
C. Zhang, J. Electrochem. Soc., 2018, 165(7), H342.
18 Q. Liang, X. J. Lv, M. Ouyang, A. Tameev, K. Katin,
M. Maslov, Q. Bi, C. H. Huang, R. Zhu and C. Zhang, ACS 30 K. Takada, R. Sakamoto, S. T. Yi, S. Katagiri, T. Kambe and
Appl. Mater. Interfaces, 2018, 10, 32404. H. Nishihara, J. Am. Chem. Soc., 2015, 137, 4681.
19 Y. Y. Dai, W. J. Li, X. X. Qu, J. Liu, S. M. Yan, M. Ouyang, 31 T. Fatima, I. U. Din, A. Akbar, M. S. Anwar and M. N. Tahir,
X. J. Lv and C. Zhang, Electrochim. Acta, 2017, 229, 271. J. Mol. Struct., 2019, 1184, 462.
20 R. Sakamoto, K. Takada, X. S. Sun, T. Pal, T. Tsukamoto, 32 R. N. Soek, C. M. Ferreira, F. S. Santana, D. L. Hughes,
E. J. H. Phua, A. Rapakousiou, K. Hoshiko and
H. Nishihara, Coord. Chem. Rev., 2016, 320–321, 118.
G. Poneti, R. R. Ribeiro and F. S. Nunes, J. Mol. Struct.,
2019, 1184, 254.
21 H. Maeda, R. Sakamoto and H. Nishihara, Coord. Chem. 33 C. J. Yao, Y. W. Zhong, H. J. Nie, H. D. Abruna and
Rev., 2017, 346, 139. J. N. Yao, J. Am. Chem. Soc., 2011, 133, 20720.
22 Y. W. Zhong, C. J. Yao and H. J. Nie, Coord. Chem. Rev., 34 Y. Nishimori, H. Maeda, S. Katagiri, J. Sendo, M. Miyachi,
2013, 257, 1357.
23 T. Mede, M. Jäger and U. S. Schubert, Chem. Soc. Rev.,
2018, 47, 7577.
24 M. K. Bera, C. Chakraborty, U. Rana and M. Higuchi,
Macromol. Rapid Commun., 2018, 39, 1800415.
25 R. Sakamoto, T. Yagi, K. Hoshiko, S. Kusaka, R. Matsuoka,
R. Sakamoto, Y. Yamanoi and H. Nishihara, Macromol.
Symp., 2012, 317–318, 276.
35 R. Sakamoto, Y. Ohirabaru, O. Matsuoka, H. Maeda,
S. Katagirl and H. Nishihara, Chem. Commun., 2013, 49, 7108.
36 M. K. Bera, T. Mori, T. Yoshida, K. Ariga and M. Higuchi,
ACS Appl. Mater. Interfaces, 2019, 11, 11893.
H. Maeda, Z. Liu, Q. Liu, W. Y. Wong and H. Nishihara, 37 D. C. Huang, J. T. Wu, Y. Z. Fan and G. S. Liou, J. Mater.
Angew. Chem., 2017, 129, 3580.
Chem. C, 2017, 5, 9370.
15126 | Dalton Trans., 2019, 48, 15121–15126
This journal is © The Royal Society of Chemistry 2019