Novel synthesis of poly(3,4-dinitro-thiophen-2-yl arylamine) derivatives via facile C–Br/N–H bulk polycondensation and its application of thermalsensor

Article abstract of DOI:10.1016/j.polymer.2020.122550

C–Br/N–H bulk polycondensation is firstly proposed and corresponding poly(3,4-dinitro-thiophen-2-yl arylamine)s derivatives have been successfully obtained with quantitative yield. Typical crystal analysis reveals that its effective reaction points distance (RPD, distance between Br and H atom) is 5.083 ?, which is 66.7% longer than the sum of van der Waals radius (r_w) of bromine and hydrogen atoms (3.05 ?). Carbazole-based monomer was explored as a thermalsensor with excellent relative sensitivity (S_a) of 0.45% K^?1.

Full text of DOI:10.1016/j.polymer.2020.122550

Polymer 201 (2020) 122550
Contents lists available at ScienceDirect
Polymer
journal homepage: http://www.elsevier.com/locate/polymer
Novel synthesis of poly(3,4-dinitro-thiophen-2-yl arylamine) derivatives
via facile C–Br/N–H bulk polycondensation and its application
of thermalsensor
,b,*
Kai Penga, Qi Luoa, Yichi Zhanga, Jiangbin Xiaa
a Hubei Key Lab on Organic and Polymeric Optoelectronic Materials, College of Chemistry and Molecular Science, Wuhan University, Wuhan, 430072, PR China
b Engineering Research Center of Organosilicon Compounds & Materials, Ministry of Education, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan,
430072, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords:
C–Br/N–H bulk polycondensation is firstly proposed and corresponding poly(3,4-dinitro-thiophen-2-yl aryl-
amine)s derivatives have been successfully obtained with quantitative yield. Typical crystal analysis reveals that
its effective reaction points distance (RPD, distance between Br and H atom) is 5.083 Å, which is 66.7% longer
than the sum of van der Waals radius (rw) of bromine and hydrogen atoms (3.05 Å). Carbazole-based monomer
C-Br/N–H Bulk polycondensation
Poly(3,4-dinitro-thiophen-2-yl arylamine)
Thermalsensor
was explored as a thermalsensor with excellent relative sensitivity (Sa) of 0.45% KÀ 1
.
1. Introduction
yields of polymers [24–26] would be obtained through C–N bond for-
mation involved polycondensation and in some cases, such method even
does not work [27]. Moreover, it is a big challenge to obtain arylamine
involved polymer through traditional methods due to less resources of
the diaryldiamines and the difficulty of making sure of the coupling
reactions occurring at diaryldiamines groups completely. Herein, the
third section of C–Br/N–H bulk polycondensation (Scheme 1) is firstly
proposed and it would generate non-conjugated arylamine polymers and
those conjugated polyaniline derivatives as well by simply keeping
primary amines groups in the platform.
Conjugated polymer attracts extensive interest due to its excellent
optical-electronic properties in lots of fields and they have played
pivotal roles in modern materials [1–3]. As the foot-stone of it, their
synthesis methods has undergone different evolutionary processes and
metal catalyzed involved polycondensation [4–7] have played a crucial
role. It is noted that these synthesis methods usually have been
employed at solution media with expensive Pd catalysts and sophisti-
cated ligands especially those C–H direct arylation polycondensation [8,
9] involved.
Furthermore, it is noted that the organic dye-, polymer-, quantum
dots- and Ln3þ-based luminescent thermosensors have been developed
and most of them demonstrate relative sensitivity (Sa) of 1–20% KÀ 1
[28]. Although several types of polymers [29–32] have been developed
as thermosensors, no polytriphenylamine derivatives involved have
been reported.
Thus, the important progress [10–19] in the new century involving
of polythiophene synthesis has been made through bulk polymerization,
which has lots advantages of solvent free, easy purification and pro-
cessibility [20]. Through devoting others and our efforts [14,15,17–19,
21], we gradually realize [15] that it can be classified into two types of
C–Br/C–Br [10–15] and C–Br/C–H [16–19] bulk polycondensation.
Let we trace back to the history of conjugated polymer or other
electro-optical polymer synthesis. It is no doubt that their great progress
definitely depends on the development of C-C or C-H bonds involved
small-molecule coupling reactions. Nevertheless, the prospect of C–N
bond formation involved polycondensation is not optimistic due to the
late invention of Buchward-Hartwig reaction [22], although Ullmann
reaction [23] was already proposed one century ago. Generally, 40–80%
2. Experimental section
2.1. Materials
All organic solvents and reagents were purchased from Sinopharm
Chemical Reagent Co., Ltd and used without further purification. N, N-
dimethylformamide (DMF), THF were dried with calcium hydride, then
* Corresponding author. Hubei Key Lab on Organic and Polymeric Optoelectronic Materials, College of Chemistry and Molecular Science, Wuhan University,
Wuhan, 430072, PR China.
E-mail address: jbxia@whu.edu.cn (J. Xia).
https://doi.org/10.1016/j.polymer.2020.122550
Received 16 January 2020; Received in revised form 25 April 2020; Accepted 2 May 2020
Available online 18 May 2020
0032-3861/© 2020 Elsevier Ltd. All rights reserved.

K. Peng et al.
Polymer 201 (2020) 122550
column with petroleum ether/ethyl acetate (v: v ¼ 20 : 1) as eluent,
followed by recrystallization from EtOH to give pure product.
2.3. General bulk polycondensation
The C–Br/N–H bulk polycondensation procedure was similar to
those C–Br/C–Br or C–Br/C–H bulk polymerization method [33–35]. In
a closed 5 mL vial, these monomers (50–200 mg) were incubated at
60-200 �C for 6–48 h.
2.4. Crystal structure determination
Scheme 1. Different bonding modes involved toward typical thiophene
Intensity data for two crystals were collected using Mo Kα radiation
(λ ¼ 0.7107 Å) on a Bruker SMART APEX diffractometer equipped with a
CCD area detector at rt. The crystallographic data and details of data
collection for two monomers were given in Table S1. Data sets reduction
and integration were performed using the software package SAINT PLUS
[36]. The crystal structure is solved by direct methods and refined using
the SHELXTL 97 software package [37].
monomers platforms proposed for bulk polycondensation.
distilled under reduced pressure.
2.2. Typical monomers synthesis procedure
To a stirred solution of amine (3 mmol) in EtOH (5 mL) was added
dropwise a solution of 2,5-dibromo-3,4-dinitrothiophene (2 mmol) in
THF (5 mL), and the mixture was stirred at rt. for 2 h. Then the reaction
mixture was poured into water (200 mL) and the exacted ethyl acetate.
After dried over anhydrous sodium sulfate, the organic phase was
concentrated in vacuum and purified by chromatography on silica gel
3. Result and discussion
3.1. Synthesis and characterizations
Monomers (M1-M16) were synthesized according to the route
Scheme 2. Synthesis of thiophen-2-yl arylamine derivatives monomers.
2

K. Peng et al.
Polymer 201 (2020) 122550
Table 1
C–Br/N–H bulk polycondensation of 3,4-dinitro-thiophen-2-yl arylamine derivatives monomers.
Entry
R
Melting point/�C
Reaction condition
Yield %
Mn (kDa)
PDI
Tonset/�C
1
2
3
n-C4H7
97
69
44
105 �C, 24 h
110 �C, 24 h
115 �C, 24 h
>95
>90
>90
2.5
7.6
4.0
1.05
1.61
1.15
85
90
n-C18H37
95
105
170
4
5
143
201
125 �C, 24 h
190 �C, 24 h
>90
>90
5.5a
1.46
–
–
95
6
135
115 �C, 24 h
>95
–
–
75
7
8
9
142
141
46
95 �C, 24 h
120 �C, 24 h
85 �C, 24h
>95
>95
>90
–
–
100
65
–
–
3.7
1.14
90
10
11
12
13
71
110 �C, 24 h
140 �C, 24h
100 �C, 24 h
125 �C, 24 h
>90
>95
>95
>95
3.3
–
1.07
112
178
167
–
–
–
120
80
–
–
105
14
15
142
143
140 �C, 24h
>90
>90
7.5a
1.50
1.26
120
100
120 �C, 24 h
5.6a
16
124
130 �C, 24 h
>90
4.8
1.41
110
a
Solid state polymerization.
Table 2
C–Br/N–H bulk polymerization of M10.
Entry
Reaction condition
Yield %
Mn (kDa)
PDI
1
2
3
4
5
110 �C,1 d
110 �C,2 d
110 �C,3 d
140 �Ca,1 d
180 �Ca,1 d
100
100
100
100
100
4.0
3.7
4.3
8.1
11.4
1.16
1.12
1.22
1.26
1.10
a
Melt state polymerization.
depicted in Scheme 2. The precursors of 2,5-dibromo-3,4-dinitrothio-
phene, 4-((2-ethylhexyl)oxy)aniline, 4-(hexadecyloxy)aniline 9,9-dibu-
tyl-9H-fluoren-2-amine were synthesized following the processes
reported in the literature [38–40]. Due to its instability under ambient
condition [41], we failed to get non-substituted thiophene monomers.
Thus, strong electron-withdrawing nitro group was introduced in 3,
4-positions of thiophene to stabilize these monomers. As shown in
Table 1, except for M5 with the extraordinary high onset temperature
(Tonset) of 170 �C for polymerization, most monomers have their Tonset
around 60–120 �C, which are comparable to those thiophene involved
C–Br/C–Br bulk polycondensation [10–15]. Accordingly, the obtained
polymers generally demonstrate Mn of 3–8 kDa, which is corresponding
of degree polymerization of 8–20. Monomer of M10 undergoes melt
state polymerization at 110 �C for 24 h and it gives Mn of 4 kDa. Mn of
P10 are almost independent on the reaction time when further extension
to 2 or 3 days. (entry 2–3, Table 2). However, their Mn of 8.1 kDa and
Fig. 1. Evolution of 1H NMR spectra of M9 under 80 �C. (5 mg of each sample).
11.4 kDa can be obtained at elevated temperature of 140 �C and 180 �C
respectively.
Let M9 as an example, its NMR spectra evolution under 80 �C was
shown in Fig. 1. The signal of hydrogen atoms of secondary amine and
the CH2 attached to O atom are assigned to 8.80 and 3.85 ppm respec-
tively with the integrated area ratio of 1 to 2. After treated for 30 min at
3

K. Peng et al.
Polymer 201 (2020) 122550
Fig. 2. FTIR spectra for these polymers (a) and UV–Vis absorption spectra of polymers in CH2Cl2 solutions (b). Inset imagine of polymers in CH2Cl2 solutions (1 �
10À 7 M) irradiation by portable UV-365 lamp.
Fig. 3. Cyclic voltammograms of P4(a), P6(b), P11(c) and P15(d) in acetonitrile containing 0.1 M [(C4H9)4N]ClO4 at a scan rate of 50 mV sÀ 1
.
80 �C the ratio decreases to 1 to 4 while it drops further to 1 to 8 after 45
min with the monomer conversion yield of 50–60%. Further extend the
reaction time to 12 h (near 100% yield), the ratio of 1 to 16.8 is ob-
tained, which is estimated of average repeat unit of 4 of the oligomer.
Thus, the C–Br/N–H bulk polymerization smoothly occurred in an ex-
pected way without side-reactions.
stretching and asymmetric stretching modes at 1340 and 1552 cmÀ 1
respectively. As shown in Fig. 2b, due to the poor conjugation of poly-
mer backbone and the strong electron-withdraw of NO2 groups attached
on the thiophene ring, all polymers show non apparent peaks but with
the long tail in the visible region. The imagine of polymers CH2Cl2 so-
lutions irradiation by portable UV-365 lamp was shown as inset in
Fig. 2b and it is clear that P15 shows the strongest fluorescence intensity
among all polymers.
3.2. Optical and electrochemical properties
Electochemical data (Fig. 3) together with corresponding optical
data derived from Fig. 2b are summarized in Table S3. According to
electochemical experiments, the onset of oxidation potentials are 1.22 V,
0.83 V, 0.85 V and 1.21 V vs Ag/AgCl for P4, P6, P11 and P15
respectively. Thus, it seems that phenyl groups would shift up HOMO
level of polymers compared with those bearing carbazole and cyclo-
hexane moieties. In addition, the nitro group attached on benzene ring
of the side chain has almost no effect on HOMO energy level of the
polymer.
In FTIR spectra (Fig. 2a), there are strong absorption region of
1200–1600 cmÀ 1, which were assigned to the stretching of C C and
–
–
C–C of thiophene or aromatic rings. Due to the existence of thiophene
rings in the backbones, most polymers demonstrate featured peaks
around 690-740 cmÀ 1 related to in-plane deformation of C–S–C of
thiophene ring. Meanwhile, P4 and P15 show distinct strong sharp peaks
at 2924, 2852 cmÀ 1, which are assigned to CH3 or CH2 stretching modes.
–
In addition, all polymers bearing NO groups show N O symmetrical
–
2
4

K. Peng et al.
Polymer 201 (2020) 122550
shown in inset of Fig. 2b. To eliminate the effect of generated bromic
acid, 20
μL/mL of triethyl amine (TEA) was added for the thermal
treated samples (16 h and 24 h) solutions. As shown in Fig. 5a, before
thermal treatment, M15 shows maximum absorption value of 0.4 at
peak of 400 nm with no absorption over 550 nm. Along with the thermal
treatment at 120 �C for 1 h, the absorption peak value at 400 nm
drastically decreases to 0.23. With the further extension 4 and 8 h, the
absorption value increases more apparent in short wavelength region
below 400 nm than that in the visible region of 400–800 nm. And its
absorption spectrum almost does not change once over 16 h of incuba-
tion. However, its fluorescence intensity decreases gradually with the
annealing time, shown in Fig. 5b.
Meanwhile, evolution procedure of M15 under different incubation
time was monitored through fluorescence microscope as well. It is
noteworthy that the monomer has no apparent imagine with the only
observation of the background while all thermal treated samples have
clear imagines under the microscope. And even some 3–10 μm sized
Fig. 4. Structure of compound M4 (a), view of Br/H and corresponding C/N
contact distances (b) and (c) crystal packing viewed along the a-axis, proposed
the most plausible polymerization pathway.
sphere aggregations are observed after 120 �C aging for 16 h in the
imagine, which may due to the melted corresponding polymer.
To gain further insight into the temperature-fluorescence relation-
ships, we studied fluorescence intensity at different temperatures of the
M15. Before fluorescence test, 5 mg of M15 was treated within 383–413
K for 3 h with interval of 5 K. After that, solid monomer/polymer
mixture was dissolved in dichloromethane solution to prepare homo-
geneous solution (1 mg/L) for fluorescence measurements. Thus, the
fluorescence intensities at 330 nm (I330) and at 432 nm (I432) are cor-
responding approximately to the amount of M15 and P15 respectively.
The intensities at 330 nm of the mixture (M15/P15) were decreased
gradually along with the increase of the temperature (Fig. 6a). However,
the value of I432 was increased continually at the detected temperature
3.3. Crystal structure analysis
Monomer of M4 has the first and the second closest Br/H distances of
5.083 and 5.763 Å respectively, with corresponding C18–N2 and
C18–N2 contact distances of 5.519 and 5.978 Å respectively (Fig. 4b).
The larger sole Br/H distance of 5.763 Å is involved in the second
polymerization pathway (Fig. S33), taking this into consideration, the
plausible polymerization pathway would (red arrow marked, shown in
Fig. 4c) involve shorter sole Br/H distances of 5.083 Å. Therefore, the
effective reaction points distance (RPD) [14,19] of 5.083 Å for M4 is
much longer (66.7%) than the van der Waals radius (rw) of reaction
points, i.e. the sum of rw of bromine and hydrogen atoms (3.05 Å).
range. Meanwhile, the dependent of temperature with I330/(I330 þ I432
)
was plotted (Fig. 6c) and it gives an equation of y ¼ 2.096–3.34� 10À 3 T
with R of 0.996. Thermal sensor of M15 has the sensitivity Sa [27], Sa ¼
∂
Q
Q, of 0.43 %–0.48% KÀ 1 at 380–420 K. This value is comparable to those
∂
T
thermal sensors based on Ln3þ phosphors nano-particles [42,43] and is
superior one or two order to those of organic dye [44,45] or polymers
thermal sensors [29–32].
3.4. Temperature fluorescence sensing analysis
To monitor the evolution of these monomers under C–Br/N–H bulk
polycondensation, M15 was selected due to its strong fluorescence
Fig. 5. The evolution of M15 under 110 �C for 1, 4, 8, 16 and 24 h (a) absorption spectroscopy (1 mg/100 mL), (b) emission spectra under irradiation of 281 nm (c)
fluorescence microscopic images of M15 at different incubated time under 120 �C. (1uL of 1 mg/mL deposited on slide glass, Scale bar represents 200
μm, irradiation
at 365 nm)
5

K. Peng et al.
Polymer 201 (2020) 122550
Fig. 6. Temperature dependent emission spectra of M15 (treated for 3 h) of CH2Cl2 solution (1 mg/L) excited at 281 nm and 365 nm respectively (a), fluorescence
intensity at 330 nm (excited at 281 nm) and 432 nm (excited at 365 nm) (b) and intensity ratio and the fitting line of I330/(I330þI432) (c).
4. Conclusions
References
[1] Q. Pei, Y. Yang, G. Yu, C. Zhang, A.J. Heeger, J. Am. Chem. Soc. 118 (1996)
3922–3929.
In summary, a section of C–Br/N–H bulk polycondensation is pro-
posed and the corresponding polymers are obtained. Crystal analysis of
M4 reveals its effective RPD of 5.083 Å, which is 66.7% longer than the
sum of van der Waals radius (rw) of bromine and hydrogen atoms. Our
study would drastically push the bulk polycondensation scope forward
and shed light to deep understand this fascinating field. In addition, M15
[2] F. Garnier, G. Tourillon, M. Gazard, J.C. Dubois, J. Electroanal. Chem. 148 (1983)
299–303.
[3] G. Yu, J. Gao, J.C. Hummelen, F. Wudl, A.J. Heeger, Science 270 (1995) 1789.
[4] A. Yokoyama, R. Miyakoshi, T. Yokozawa, Macromolecules 37 (2004) 1169–1171.
[5] M. Rehahn, A. Schlüter, G. Wegner, W.J. Feast, Polymer 30 (1989) 1060–1062.
[6] M. Bochmann, K. Kelly, J. Chem. Soc., Chem. Commun. (1989) 532–534.
[7] Z. Bao, W. Chan, L. Yu, Chem. Mater. 5 (1993) 2–3.
thermalsensor exhibits excellent sensitivity of 0.45% KÀ 1
Declaration of competing interst
.
[8] M. Se Vignon, J. Papillon, E. Schulz, M. Lemaire, Tetrahedron Lett. 40 (1999)
5873–5876.
[9] Q. Wang, R. Takita, Y. Kikuzaki, F. Ozawa, J. Am. Chem. Soc. 132 (2010)
11420–11421.
[10] H. Meng, D.F. Perepichka, M. Bendikov, F. Wudl, G.Z. Pan, W. Yu, W. Dong,
S. Brown, J. Am. Chem. Soc. 125 (2003) 15151–15162.
The authors declare no competing financial interest.
CRediT authorship contribution statement
[11] H.J. Spencer, R. Berridge, D.J. Crouch, S.P. Wright, M. Giles, I. McCulloch, S.
J. Coles, M.B. Hursthouse, P.J. Skabara, J. Mater. Chem. 13 (2003) 2075–2077.
[12] A. Patra, Y.H. Wijsboom, S.S. Zade, M. Li, Y. Sheynin, G. Leitus, M. Bendikov,
J. Am. Chem. Soc. 130 (2008) 6734–6736.
Kai Peng: Data curation, Formal analysis. Qi Luo: Formal analysis.
Yichi Zhang: Data curation. Jiangbin Xia: Conceptualization, Writing -
original draft, Writing - review & editing.
�
�
[13] M. Lepeltier, J. Hiltz, T. Lockwood, F. Belanger-Gariepy, D.F. Perepichka, J. Mater.
Chem. 19 (2009) 5167–5174.
[14] C. Tusy, L. Huang, J. Jin, J. Xia, RSC Adv. 4 (2014) 8011–8014.
[15] K. Peng, T. Pei, N. Huang, L. Yuan, X. Liu, J. Xia, J. Polym. Sci., Part A: Polym.
Chem. 56 (2018) 1676–1683.
Acknowledgements
[16] P. Wagner, K.W. Jolley, D.L. Officer, Aust. J. Chem. 64 (2011) 335–338.
[17] Y. Yin, Z. Li, J. Jin, C. Tusy, J. Xia, Synth. Met. 175 (2013) 97–102.
[18] C. Tusy, K. Jiang, K. Peng, L. Huang, J. Xia, Polym. Chem. 6 (2015) 1014–1022.
[19] K. Jiang, X. Cai, X. Liu, J. Xia, Polymer 168 (2019) 70–76.
[20] C.D. Papaspyrides, S.N. Vouyiouka, Solid State Polymerization, John Wiley & Sons,
INC, 2009.
This work was supported by the Natural Science Foundation of China
(21875173).
[21] L. Chen, J. Jin, X. Shu, J. Xia, J. Power Sources 248 (2014) 1234–1240.
[22] F. Paul, J. Patt, J.F. Hartwig, J. Am. Chem. Soc. 116 (1994) 5969–5970.
[23] F. Ullmann, J. Bielecki, Ber. Dtsch. Chem. Ges. 34 (1901) 2174–2185.
[24] B. Jung, J. Lee, H.Y. Chu, L. Do, H. Shim, Macromolecules 35 (2002) 2282–2287.
[25] T. Kanbara, Y. Miyazaki, K. Hasegawa, T. Yamamoto, J. Polym. Sci., Part A: Polym.
Chem. 38 (2000) 4194–4199.
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.polymer.2020.122550.
[26] A.R. Rabindranath, Y. Zhu, K. Zhang, B. Tieke, Polymer 50 (2009) 1637–1644.
[27] T. Kanbara, K. Izumi, T. Narise, K. Hasegawa, Polym. J. 30 (1998) 66.
6

K. Peng et al.
Polymer 201 (2020) 122550
�
[28] C.D.S. Brites, P.P. Lima, N.J.O. Silva, A. Millan, V.S. Amaral, F. Palacio, L.D. Carlos,
[37] G.M. Sheldrick, Acta Crystallogr. A A64 (2008) 112.
Nanoscale 4 (2012) 4799–4829.
[38] J. Zhou, S. Xie, E.F. Amond, M.L. Becker, Macromolecules 46 (2013) 3391–3394.
[39] T. Gonec, I. Zadrazilova, E. Nevin, T. Kauerova, M. Pesko, J. Kos, M. Oravec,
P. Kollar, A. Coffey, J. O’Mahony, A. Cizek, Molecules 20 (2015) 9767–9787.
[40] C. Wang, Z. Wang, T. Ma, Chin. J. Appl. Chem. 30 (2013) 757–763.
[41] O.A. Tarasova, L.V. Klyba, V.Y. Vvedensky, N.A. Nedolya, B.A. Trofimov,
L. Brandsma, H.D. Verkruijsse, Eur. J. Org Chem. (1998) 253–256.
[42] X. Wang, X. Kong, Y. Yu, Y. Sun, H. Zhang, J. Phys. Chem. C 111 (2007)
15119–15124.
~
[29] V. Augusto, C. Baleizao, M.N. Berberan-Santos, J.P.S. Farinha, J. Mater. Chem. 20
(2010) 1192–1197.
[30] K. Iwai, Y. Matsumura, S. Uchiyama, A.P. de Silva, J. Mater. Chem. 15 (2005)
2796–2800.
[31] C. Gota, S. Uchiyama, T. Yoshihara, S. Tobita, T. Ohwada, J. Phys. Chem. B 112
(2008) 2829–2836.
[32] S. Ryu, I. Yoo, S. Song, B. Yoon, J. Kim, J. Am. Chem. Soc. 131 (2009) 3800–3801.
[33] H. Meng, D.F. Perepichka, M. Bendikov, F. Wudl, G.Z. Pan, W. Yu, W. Dong,
S. Brown, J. Am. Chem. Soc. 125 (2003) 15151–15162.
[34] C. Tusy, L. Huang, J. Jin, J. Xia, RSC Adv. 4 (2014) 8011–8014.
[35] C. Tusy, K. Jiang, K. Peng, L. Huang, J. Xia, Polym. Chem. 4 (2015) 1014–1022.
[36] G.M. Sheldrick, SHELXTL, Version 6.14, Bruker Analytical X-ray Instruments, Inc,
Madison, WI, USA, 2003.
[43] M. Nakamura, S. Ozaki, M. Abe, T. Matsumoto, K. Ishimura, J. Mater. Chem. 21
(2011) 4689–4695.
[44] N. Chandrasekharan, L.A. Kelly, J. Am. Chem. Soc. 123 (2001) 9898–9899.
€
[45] M.E. Kose, B.F. Carroll, K.S. Schanze, Langmuir 21 (2005) 9121–9129.
7