Synthesis and Electrochromic Properties of New Terpyridine

Article pubs.acs.org/Macromolecules

Synthesis and Electrochromic Properties of New Terpyridine− Triphenylamine Hybrid Polymers Congbin Fan,†,‡,∥ Changqing Ye,†,∥ Xiaomei Wang,*,† Zhigang Chen,† Yuyang Zhou,† Zuoqin Liang,† and Xutang Tao§ †

Jiangsu Key Laboratory for Environmental Functional Materials, School of Chemistry, Biology and Materials Engineering, Suzhou University of Science and Technology, Suzhou 215009, China ‡ Jiangxi Key Laboratory of Organic Chemistry, Jiangxi Science and Technology Normal University, Nanchang 330013, China § State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China

Downloaded by STOCKHOLM UNIV on September 3, 2015 | http://pubs.acs.org Publication Date (Web): September 3, 2015 | doi: 10.1021/acs.macromol.5b00493

S Supporting Information *

ABSTRACT: Six metallic terpyridine-based complexes MLn (M = Ru, Fe; n = 1−3) with two triphenylamine sides have been designed and synthesized with the purpose of both providing four terminal active sites for the following electrochemical polymerization and prolonging the electrochromic memory time and the durability. Within the voltage range from 0 to 2 V, the obtained electro-polymerized films of polymers (p-MLn) present reversibly distinguishable color change (i.e., from orange red to yellow (or tan) for polymers p-RuLn and from purple to blue for polymers p-FeLn), strongly suggesting that the electrochromic colors could be tuned with the binding metal ion. Interestingly, the electrochromic memory ability and long-term stability (durability) have been found to depend on not only the rigidity but also the length of these triphenylamine-based ligands. It is interpreted that triphenylamine-based ligands with the rigid and short conjugation can promote intramolecular charge transfer from the triphenylamine group (D) to the metallic terpyridine (A), which certainly will effectively stabilize the oxidation state (i.e., Ru3+, Fe3+) of metallic terpyridine and remarkably enhance the memory ability and durability of electrochromic film.

1. INTRODUCTION Electrochromic materials (ECMs), which can be reversibly switched between different colors under the action of voltage, have received great interest due to their potential applications, such as information storage,1,2 electrochromic display,3,4 optical switch,5−8 smart windows,9,10 and antiglare mirrors.11,12 Up to date, many ECMs, such as metal oxides,13,14 conducting polymers,15−17 macromolecules, and their corresponding metal complexes18 have been developed and investigated. Among these ECMs, metal macromolecule complexes have been well-recognized because of their excellent strong optical contrast and their easy-to-control electrochromic response by the choice of the metal ions as well as the design of the ligands.19,20 For example, terpyridine-based metal complexes have been extensively studied recently,21−24 because the πconjugated terpyridine unit has high binding affinity to many metal ions,22,25−27 and can offer a thermodynamic driving force to form a stable metallosupramolecule, which makes the metallic terpyridine-based materials have excellent electrochromic properties, such as strong optical contrast, high coloration ability, low switching potential, and fast switching rate.22 However, the metallic terpyridine-based complexes usually only have poor solubility, which makes film-forming processes difficult. Moreover, although metallic terpyridinebased complexes present good thermic-photostability,28 their © XXXX American Chemical Society

electrochromic memory ability and long-term stability are much less than satisfactory. In order to overcome these problems, we have designed a series of new terpyridine-based complexes with a triphenylamine unit on both sides to facilitate the filmforming process via a convenient film-forming technique with easy fabrication, controllable film thickness, and better film morphology. It is well-known that triphenylamine derivatives have many excellent photoelectroactive properties such as holetransporters, light-emitters, and memory devices.29−31 What’s more, triphenylamine can provide a pair of lone electron on N atom, which can readily form monoradical cation and dualradical cation, respectively, to lead the corresponding electropolymerization.32,33 Furthermore, triphenylamine, due to its strong donating ability, would stabilize the oxidation state of metallic terpyridine after the voltage was turned off, which would enhance the memory ability of electrochromic film. Recently, several groups have synthesized some terpyridinetriphenylamine ligands and the corresponding Ru-complexes. Williams et al. reported the synthesis and spectroscopy properties of (4-[4-(2,2′:6′,2″-terpyridinyl)]phenyltriphenylamine);34 Yan et al. reported the synthesis Received: March 8, 2015 Revised: August 26, 2015

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DOI: 10.1021/acs.macromol.5b00493 Macromolecules XXXX, XXX, XXX−XXX

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Figure 1. Syntheses of ligands (Ln. n = 1−3), complexes (MLn. M = Ru, Fe; n = 1−3) and polymers (p-MLn. M = Ru, Fe; n = 1−3).

and excitation-dependent fluorescence of bis[4-4-(N,N′diphenylamino)phenyl-2,2′:6′,2″- terpyridine]Ruthenium(II) and bis[4′-(4-{2-[4-(N,N′-diphenylamino)phenyl]ethylene}phenyl-2,2′:6′,2″- terpyridine]Ruthenium(II).35 Later, Qiu et al. have electropolymerized [Ru(L)2](PF6)2 {L = 4′-[4(diphenylamino)phenyl]-2,2′:6′,2″-terpyridine} and found this polymer can exhibit a clear color change between the neutral and oxidized states.33 However, to the best of our knowledge, the structure/performance correlations of terpyridine-triphenylamine complexes in electrochromic behaviors have not hitherto been reported. In this paper, a series of terpyridine-triphenylamine complexes (FeLn and RuLn) and the corresponding polymer films have been synthesized to investigate electrochromic properties with attention paid to the metal ion effect and ligand conjugation effect upon the electrochromic colors, the memory ability, and durability of electrochromic films. As shown in Figure 1, Ln stands for the ligand L1 (4-(2,2′:6′,2″terpyridinyl)triphenylamine), 33 L2 (4-[4-(2,2′:6′,2″-

terpyridinyl)]phenyltriphenylamine), 34 and L3 (4-[4(2,2′:6′,2″-terpyridinyl)]styryltriphenylamine),35 respectively. These ligands contain triphenylamine as the donor (D); terpyridine as the acceptor (A); and phenyl, biphenyl and stilbene as the conjugated relay (π), respectively. With the metal ions linkage, we synthesized six “D−π−A−π−D” type complexes (MLn), where two terminal triphenylamine groups can provide a pair of lone electron on N atom and can readily lead to the electro-polymerization to obtain the corresponding six polymers p-MLn (M = Ru, Fe; n = 1−3).

2. EXPERIMENTAL SECTION 2.1. Reagents and Measurements. All chemicals were purchased from Aldrich or Acros Chemical Co. and were used without any further purification. For the experiment details of ligands’ synthesis, please see the Supporting Information.33−40 Melting points (mp) were determined on an X-5 melting point measurement instrument (Gongyi City Yuhua Instrument Co., Ltd.). Highresolution mass spectrometry (HRMS) spectrum analysis was B


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Figure 2. CVs of complexes MLn during the electropolymerization on ITO working electrode in deoxygenated dichloromethane solution containing 0.1 M electrolyte tetrabutylammonium hexafluorophosphate (n-Bu4NPF6) at potential scanning rates of 50 mV·s−1. performed by Thermo Fisher LTQ Orbitrap XL or electrospray ionization (ESI-micrOTOF). 1H NMR and 13C NMR spectra were recorded on an INOVA-400 spectrometer with CDCl3 or DMSO as the solvent and tetramethylsilane as an internal standard. AFM images were obtained on a Veeco Nanoscope III atomic force microscope (AFM). UV−vis absorption spectra were measured on a Hitachi U3500 recording spectro-photometer of solid-state film or of solution with quartz curets having a path of 1.0 cm.

Electrochemical measurements were carried out on a CHI 660B potentiostat/galvanostat (Shanghai Chenhua Instrumental Co., Ltd., China) in a three-electrode cell purged with N2, wherein ITO glass was used as working electrode, platinum wire with a diameter of 0.5 mm as counter electrode, and Ag/AgCl (0.1 M) as reference electrode. All of the electrodes were carefully cleaned with water and acetone, respectively. Then, the cyclic voltammetry (CV) was employed in deoxygenated dichloromethane (CH2Cl2) containing 0.10 M of nC


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Figure 3. Proposed polymerization mechanism: An anodic oxidation on terminal triphenylamine units. Bu4NPF6 at the scanning rate of 50 mV·s−1. Electrochromic measurements were done on a Hitachi U-3500 recording spectrophotometer of solid state film or of solution with quartz curets having a path of 1.0 cm. Electrochromic properties were investigated through UV−vis absorption spectra and the cyclic voltammetry (CV) measurements. 2.2. Electro-Polymerization of Films (p-MLn. M = Ru, Fe; n = 1−3). The preparation of polymer films (p-MLn) were obtained by the electrochemical polymerization, which were carried in a threeelectrode cell (ITO glass as the working electrode, platinum rod as the counter electrode, and Ag/AgCl (0.1 M) as the reference electrode) by cyclic voltammetry (CV) in deoxygenated dichloromethane (CH2Cl2) containing 0.10 M of n-Bu4NPF6 at the scanning rate of 50 mV·s−1.

With successively scanning within ∼5 min, complexes MLn (i.e., monomer) were gradually electro-polymerized and deposited on ITO glass to obtain a layer of colorful film, that is, polymers (p-MLn). After the polymer films were washed repeatedly with dichloromethane to remove the residual monomers and dried, they were characterized and electrochromically measured.

3. RESULTS AND DISCUSSION 3.1. Electrochemical Polymerization of Complex Films. Figure 2 (a ∼ f) present the CV curves of the complexes during the electro-polymerization. The increase of redox wave currents indicates that the amount of electroD


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Figure 4. (a ∼ c) UV−vis spectra of ligands (Ln. n = 1−3) and complexes (MLn. M = Ru, Fe; n = 1−3) in CH2Cl2 (1.0 × 10−5 M), as well as (d) polymers (p-MLn. M = Ru, Fe; n = 1−3) measured as solid state.

Table 1. UV−vis Properties of Ligands (Ln, n = 1−3), Complexes (MLn, M = Ru or Fe, n = 1−3), and the Polymers (p-MLn, M = Ru or Fe, n = 1−3)

a

Ln

λmax (nm)a (εmax [104 M−1cm−1])

MLn

L1

361 (2.10)

L2

358 (3.08)

L3

389 (0.64)

RuL1 RuL2 RuL3 FeL1 FeL2 FeL3

λ (nm) (εmax [104 M−1cm−1]) 519 498 493 576 575 570

(1.84) (1.87) (1.85) (2.35) (2.20) (2.34)

p-MLn

λ (nm)

p-RuL1 p-RuL2 p-RuL3 p-FeL1 p-FeL2 p-FeL3

496 496 496 574 574 574

Ln and MLn were measured in CH2Cl2 (1.0 × 10−5 M). Polymers were measured in solid film.

scanning. The AFM microscope images showed that surfaces of the formed six electropolymerized films were films with pump height less than 50 nm (Supporting Information, Figure S1). Therefore, these metal complex films fabricated through electrochemical polymerization were relatively uniform and suitable to be applied as electrochromic materials. 3.2. Optical Properties. Optical properties of L1 ∼ L3 and their corresponding complexes were investigated through UV− vis spectroscopy in solution (Figure 4a−c). All ligands were colorless with the maximum absorption peaks at 361 nm for L1, 358 nm for L2 and 389 nm for L3, showing that the red-shift of π−π* absorption is due to the increased molecular conjugation (Table 1). As anticipated, when these ligands were coordinated with metal ions (Ru2+ or Fe2+), the significant change in color could be found, that is, the orange red color for complexes RuLn (n = 1−3) and purple color for complexes FeLn (n = 1− 3), which could be assigned to the charge transfer from terpyridine to metal ion (LMCT).43,44 The maximum LMCT absorption bands were located at 519, 498, and 493 nm for RuL1, RuL2, and RuL3, respectively, showing that such redshift of LMCT absorption is inversely proportional to the increased conjugation of ligiands. Similar conditions for FeLn (n = 1−3) are also observed; that is, the maximum LMCT absorption bands were red-shifted from 570 nm (FeL3), 575

deposited polymer was increased on the ITO (working electrode) with the CV proceeding. These complexes (MLn, M = Ru, Fe; n = 1−3) exhibit high electro-polymerization activity because their triphenylamine units are strong electrondonating groups. We noticed that the electro-polymerization CV curves presented multistep (three) oxidation processes except RuL2 (two oxidation processes) (Figure 2c). The multistep oxidation processes suggested that the electrochemical polymerization needs multisteps to form a polymer, which can be interpreted by the electro-polymerization mechanism (Figure 3), where the electro-polymerization reaction was only involved in two terminal triphenylamine units. Under the positive bias voltage, one of the lone-electron pairs on N atom within one of two triphenylamine units was first lost to form monoradical cation (ii) and then to form a dual-radical cation (iii).41 With the p-electron delocalization around the terminal triphenylamine backbone, a series of resonated quinoid structures (iii ∼ vii) would be formed.42 By the free radical coupling with concomitance of the conversion from quinoid to Kekule structure, oligomerizer (viii) was successfully formed.32 Then, the oligomerizer (viii) would repeat the similar the redox processes to form intermediate products (ix ∼ xi) and polymer (xii). Lastly, a layer of colorful film on the ITO could be seen with successive potential E


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Figure 5. Absorption spectra of polymer films on ITO when the voltages from 0 to 2 V were applied: (a) p-RuL1; (b) p-FeL1; (c) p-RuL2; (d) pFeL2; (e) p-RuL3; (f) p-FeL3; (g) photographs of films in the neutral and oxidized states when the voltages between 0 and 2 V were applied.

nm (FeL2) to 576 nm (FeL1) with the decrease of ligand length. These strongly suggested that the ligand with the shortest conjugated length (for example L1) was beneficial to the interaction between “D” and “A”, resulting in bathochromic shift in LMCT absorption band. For the given ligand, complexes FeLn (n = 1−3) exhibited a red-shift of ca. 50−70 nm, relative to complexes RuLn (n = 1−3). Furthermore, the molar extinction coefficient (εmax) of complexes FeLn (n = 1− 3) were obviously higher than those of complexes RuLn (n = 1−3). All of these suggested that the electronic interactions between ligand and metal ion induced a different spectral shift to lower energy in the order of Fe(II) > Ru(II). Note that there

are dual absorption bands of complexes FeLn (n = 1−3) found in the range of visible region, implying that their configurations were twisted to some degree, compared with those of complexes RuLn (n = 1−3). Interestingly, after these complexes were electro-polymerized, almost all of the obtained polymer films exhibited one strong and broad absorption band in the visible range (Figure 4d). That is, p-RuLn (n = 1−3) were at 496 nm and p-FeLn (n = 1−3) at 574 nm. These results suggested that the LMCT absorption positions in the solid film were mainly affected by the binding metal ions, whereas the influence of ligands upon the LMCT absorption could be negligible. F


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Macromolecules 3.3. Electrochromic Behavior. The electrochemical behaviors of these polymer films were determined through cyclic voltammetry (CV) (Supporting Information, Figure S2), in which most of them exhibited one pair of redox peaks (exception to p-RuL1 and p-RuL3). The complex containing different metal ion and ligand can exhibit different charge distribution in molecules. So, the properties of electrochemisty are influenced by the metal and ligand.42 The electrochemical behaviors of p-RuL1 and p-RuL3 films show two pairs of redox peaks when determined by CV in agreement with the results reported by Qiu et al.33 The two polymers are mainly presented the electrochemical redox properties of triphenylamine units and its derivatives.33,45 These polymer films could be repeatedly cycled between the oxidized and neutral states without significant decomposition, indicating high redox stability of the produced polymer films. The absorption spectra, accompanied by the photographs of polymer films, were real-time monitored with potentials from 0 to 2 V (Figure 5a−g), where the neutral states (reduction states) of p-RuLn (n = 1−3) films were orange red while their oxidation states were either yellow (p-RuL1) or tan (p-RuL2 and p-RuL3). On the other hand, the neutral states of p-FeLn (n = 1−3) films were purple while their oxidation states were blue. As shown in Figure 5a, with the increasing voltages from 0 to 2 V, the absorption peak of p-RuL1 film at ∼700 nm was rapidly enhanced while the absorption band within 370−550 nm became wide and low, which turned p-RuL1 films from orange red into yellow. The neutral state of p-FeL1 film was purple, and the corresponding oxidation state was turned to blue when the potential from 0 to 2 V was applied; additionally, its absorption peak at 574 nm was decreased, and the absorption peak beyond 700 nm was increased (Figure 5b). Similar results of other polymer films (such as p-RuL2, p-RuL3, p-FeL2 and p-FeL3) could also be observed. Very importantly, these color changes of solid films were highly reversible when oxidation−reduction occurred even without special protection against oxygen and humidity. The oxidation is due to the losing of one electron on divalent metal ion (Ru2+ or Fe2+) to produce trivalent metal ion (Ru3+ or Fe3+) within terpyridine units. Because the binding metal ion played an very important role in the absorption position, absorption bands of LM(II)CT and LM(III)CT certainly would be significantly distinguished. The oxidation of transition metal ion could suspend the LMCT, causing this oxidized state to be virtually transparent.24,46,47 All of these electrochromic properties of these electropolymerizable hybrid materials indicated they might have great potential in displays and optical switches. 3.3. Electrochromic Memory and Long-Term Stability. Memory ability (time) of electrochromic film is defined as the time that can keep the half absorbance of oxidation state after the potential is turned off. For the given ligand, the memory ability was found in the order of p-FeLn > p-RuLn, and for the given metal ion, the memory ability was increased with the decrease of ligand length (Table 2). That is, the memory time of films is in the order of p-FeL1 (11.4 min) ≈ p-RuL1 (11.8 min) > p-FeL2 (10.7 min) > p-RuL2 (9.5 min) > p-FeL3 (3.3 min) ≈ p-RuL3 (3.2 min) (see Figure S3). Compared with the long and flexible ligand (L3), the short ligand (L1) with rigidity could effectively promote charge transfer from triphenylamine (D) toward metallic terpyridine (A), which could effectively stabilize trivalent mental ion (Ru3+ and Fe3+) within terpyridine units. For example, it took p-ML1 films (oxidation state) a

Table 2. Memory Ability and Long-Term Stability of Films polymer film p-RuLn

p-FeLn

a

p-RuL1 p-RuL2 p-RuL3 p-FeL1 p-FeL2 p-FeL3

memory time (min)

OD loss (%)a

11.8 9.5 3.2 11.4 10.7 3.3

10 20 40 10 23 39

Optical density (OD) loss of polymer films after redox 300 cycles.

hundred of minutes to come back its original absorbance (reduction state) after the voltage was off, which was much longer than that of other terpyridine-based counterparts.47 On the other hand, p-ML3 films only needed 10 min to recover its original absorbance (reduction state). Additionally, the flexible ligand L3 would also increase the degree of freedom of the system,37 which would lead to the shortest memory time of pML3 films (M = Ru, Fe). With moderate rigidity and length ligand of p-ML2 films, their memory abilities were in the middle. In order to inspect the long-term stability of electrochromic film, a long-term redox switching study was performed through continuously changing the voltages between the two given values of 0 and 2 V. The absorbance changes of p-MLn films were monitored after 300 redox cycles (Table 2, Supporting Information, Figure S4), and their long-term stabilities were in the order of p-ML1 > p-ML2 > p-ML3 (M = Ru, Fe). The losses of absorbance (optical density, OD) were at 10% for pRuL1 and p-FeL1 films, 20−23% for p-RuL2 and p-FeL2 films and 39−40% for p-RuL3 and p-FeL3, which indicated that the long-term stability decrease was usually accompanied by the decrease of ligand rigidity. All of these results showed that, regardless of the binding metal ion, the long-term stability was mainly influenced by the ligand. The weakest stabilities for pRuL3 and p-FeL3 might be due to the flexible stilbene unit in ligand L3.

4. CONCLUSIONS A series of “D−π−A−π−D” complexes with the metallic terpyridine-core (A) and triphenylamine (D) on their both sides were synthesized in order to provide four active sites for electrochemical polymerization. Under the very low voltages between 0−2 V, the obtained electro-polymerized films (pMLn, M = Ru or Fe, n = 1−3) showed distinguishing color changes from orange red to yellow (or tan) for polymers pRuLn (n = 1−3) and from purple to blue for polymers p-FeLn (n = 1−3), which was demonstrated to depend on the binding metal ion within the complexes. Moreover, these complexes exhibited high molar extinction coefficient (εmax > 1.84 × 104 M−1 cm−1), which was confirmed to present high contrast ratio and good coloration efficiency. Electrochromic measurements have shown that polymers pML1 (M = Ru or Fe) with rigid and short ligand (L1) possess long memory time (∼12 min) and better long-term stability (10% OD loss after redox 300 cycles), whereas polymers pML3 (M = Ru or Fe) with flexible and long ligand (L3) have short memory time (∼3 min) and worse durability (40% OD loss after redox 300 cycles). These strongly suggest that the memory ability and long-term stability rest with the ligands containing triphenylamine group. Because triphenylamine, as a strong donating group, can effectively promote intramolecular charge transfer from triphenylamine to (Ru3+ and Fe3+) and G


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Macromolecules stabilize the oxidation state of metal ion (Ru3+ and Fe3+), the rigid and short ligand of terpyridine-triphenylamine is in favor of enhancement the memory ability and long-term stability, which is helpful for the molecular design strategy for the electrochromic film applications.

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(8) Chen, C.-J.; Yen, H.-J.; Hu, Y.-C.; Liou, G.-S. Novel programmable functional polyimides: preparation, mechanism of CT induced memory, and ambipolar electrochromic behavior. J. Mater. Chem. C 2013, 1, 7623−7634. (9) Azens, A.; Granqvist, C. Electrochromic smart windows: energy efficiency and device aspects. J. Solid State Electrochem. 2003, 7, 64−68. (10) Granqvist, C. G.; Azens, A.; Hjelm, A.; Kullman, L.; Niklasson, G. A.; Rönnow, D.; Mattsso, M. S.; Veszele, M.; Vaivars, G. Recent advances in electrochromics for smart windows applications. Sol. Energy 1998, 63, 199−216. (11) Chen, J. Z.; Ko, W. Y.; Yen, Y. C.; Chen, P. H.; Lin, K. J. Hydrothermally processed TiO2 nanowire electrodes with antireflective and electrochromic properties. ACS Nano 2012, 6, 6633− 6639. (12) Pozo-Gonzalo, C.; Mecerreyes, D.; Pomposo, J. A.; Salsamendi, M.; Marcilla, R.; Grande, H.; Vergaz, R.; Barrios, D.; Sánchez-Pena, J. M. All-plastic electrochromic devices based on PEDOT as switchable optical attenuator in the near IR. Sol. Energy Mater. Sol. Cells 2008, 92, 101−106. (13) Song, Y. Y.; Gao, Z. D.; Wang, J. H.; Xia, X. H.; Lynch, R. Multistage coloring electrochromic device based on TiO2 nanotube arrays modified with WO3 nanoparticles. Adv. Funct. Mater. 2011, 21, 1941−1946. (14) Nah, Y. C.; Ghicov, A.; Kim, D.; Berger, S.; Schmuki, P. TiO2WO3 composite nanotubes by alloy anodization: growth and enhanced electrochromic properties. J. Am. Chem. Soc. 2008, 130 (48), 16154− 16155. (15) Beaujuge, P. M.; Amb, C. M.; Reynolds, J. R. A side-chain defunctionalization approach yields a polymer electrochrome sprayprocessable from water. Adv. Mater. 2010, 22, 5383−5387. (16) Rios, E. C.; Rosario, A. V.; Nogueira, A.; Micaroni, L. Electrochromic devices based on poly(3-methylthiophene) and various secondary electrochromic materials. Sol. Energy Mater. Sol. Cells 2010, 94, 1338−1345. (17) Shi, P. J.; Amb, M.; Knott, E. P.; Thompson, E. J.; Liu, D. Y.; Mei, J. G.; Dyer, A. L.; Reynolds, J. R. Broadly absorbing black to transmissive switching electrochromic polymers. Adv. Mater. 2010, 22, 4949−4953. (18) Maier, A.; Cheng, K.; Savych, J.; Tieke, B. Double-electrochromic coordination polymer network films. ACS Appl. Mater. Interfaces 2011, 3, 2710−2718. (19) Roundhill, D. M. Photochemistry and Photophysics of Metal Complexes; Springer: Berlin, 1994. (20) Balzani, V.; Scandola, F. Supramolecular Photochemistry; Ellis Harwood: Chichester, 1990; Chapter 3 (21) Yao, C. J.; Zhong, Y. W.; Yao, J. Charge delocalization in a cyclometalated bisruthenium complex bridged by a noninnocent 1,2,4,5-tetra(2-pyridyl)benzene ligand. J. Am. Chem. Soc. 2011, 133, 15697−15706. (22) Wild, A.; Winter, A.; Schlutter, F.; Schubert, U. S. Advances in the field of π-conjugated 2,2′:6′,2″-terpyridines. Chem. Soc. Rev. 2011, 40, 1459−1511. (23) Maier, A.; Tieke, B. Coordinative layer-by-layer assembly of electrochromic thin films based on metal ion complexes of terpyridinesubstituted polyaniline derivatives. J. Phys. Chem. B 2012, 116, 925− 934. (24) Han, F. S.; Higuchi, M.; Kurth, D. G. Metallosupramolecular polyelectrolytes self-assembled from various pyridine ring-substituted bisterpyridines and metal ions: photophysical, electrochemical, and electrochromic properties. J. Am. Chem. Soc. 2008, 130, 2073−2081. (25) Hilmey, D. G.; Paquette, L. A. Exo- and endo-receptors in one. A novel class of supramolecular structures housing transition-metalbinding bi- and terpyridine units alongside lithium ion-selective trispirotetrahydrofuranyl components. J. Org. Chem. 2004, 69, 3262− 3270. (26) Liang, Z.-Q.; Wang, C.-X.; Yang, J.-X.; Gao, H.-W.; Tian, Y.-P.; Tao, X.-T.; Jiang, M.-H. A highly selective colorimetric chemosensor for detecting the respective amounts of iron(II) and iron(III) ions in water. New J. Chem. 2007, 31, 906−910.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.macromol.5b00493. Experimental details for the synthesis of ligands and supplemental data as noted in the text (PDF) Crystallographic data (CIF)

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AUTHOR INFORMATION


Corresponding Author

* (X.-M.W.) E-mail: [email protected]. Tel: 860512-68326615. Author Contributions ∥

These authors contributed equally to this work (C.F. and C.Y.). Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank the NSFC (51273141, 51303122, 21203135, 21363009), Natural Science Foundation of Jiangsu Province (BK20130262), Natural Science Foundation of Jiangsu Provincial Department of Education (11KJA430003), Excellent Innovation Team in Science and Technology of Jiangsu Provincial Department of Education, Project of Science and Technology of Suzhou (SYG201204), the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), Jiangsu Provincial Cooperation Innovation Center of Water Research Technology and Materials, the Opening Project (No. SJHG1311) of the Jiangsu Key Laboratory for Environment Functional Materials, and the Young Scientist training program of the Jiangxi Province (20153BCB23008) for financial support. We are grateful to Prof. Seik Weng Ng for crystal assistance (Grant No. UM.C/625/1/HIR/247).

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REFERENCES

(1) Beaujuge, P. M.; Reynolds, J. R. Color control in π-conjugated organic polymers for use in electrochromic devices. Chem. Rev. 2010, 110, 268−320. (2) Gazotti, W. A.; Casalbore-Miceli, G.; Geri, A.; Berlin, A.; de Paoli, M. A. An all-plastic and flexible electrochromic device based on elastomeric blends. Adv. Mater. 1998, 10, 1522−1525. (3) Liu, H.; Crooks, R. M. Paper-based electrochemical sensing platform with integral battery and electrochromic read-out. Anal. Chem. 2012, 84 (5), 2528−2532. (4) Mortimer, R. J.; Dyer, A. L.; Reynolds, J. R. Electrochromic organic and polymeric materials for display applications. Displays 2006, 27, 2−18. (5) Matsui, J.; Kikuchi, R.; Miyashita, T. A trilayer film approach to multicolor electrochromism. J. Am. Chem. Soc. 2014, 136, 842−845. (6) Korgel, B. A. Composite for smarter windows. Nature 2013, 500, 278−279. (7) Vasilyeva, S. V.; Beaujuge, P. M.; Wang, S.; Babiarz, J. E.; Ballarotto, V. W.; Reynolds, J. R. Material strategies for black-totransmissive window-type polymer electrochromic devices. ACS Appl. Mater. Interfaces 2011, 3, 1022−1032. H


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Macromolecules (27) Hong, Y.; Chen, S.; Leung, C. W. T.; Lam, J. W. Y.; Liu, J.; Tseng, N.-W.; Kwork, R. T.; Yu, Y.; Wang, Z.; Tang, B. Z. Fluorogenic Zn(II) and chromogenic Fe(II) sensors based on terpyridinesubstituted tetraphenylethenes with aggregation-induced emission characteristics. ACS Appl. Mater. Interfaces 2011, 3, 3411−3418. (28) Maier, A.; Rabindranath, A. R.; Tieke, B. Fast-switching electrochromic films of Zinc polyiminofluorene-terpyridine prepared upon coordinative supramolecular assembly. Adv. Mater. 2009, 21, 959−963. (29) Shirota, Y.; Kageyama, H. Charge carrier transporting molecular materials and their applications in devices. Chem. Rev. 2007, 107, 953− 1010. (30) Ku, C. H.; Kuo, C. H.; Chen, C. Y.; Leung, M. K.; Hsieh, K. H. PLED devices containing triphenylamine-derived polyurethanes as hole-transporting layers exhibit high current efficiencies. J. Mater. Chem. 2008, 18, 1296−1301. (31) Fang, Y. K.; Liu, C. L.; Yang, G. Y.; Chen, P. C.; Chen, W. C. New donor−acceptor random copolymers with pendent triphenylamine and 1,3,4-oxadiazole for high-performance memory device applications. Macromolecules 2011, 44, 2604−2612. (32) Chang, C. L.; Hu, C. L.; Tseng, C. Y.; Chuang, C. N.; Ho, K. C.; Leung, M. K. Ambipolar freestanding triphenylamine/fullerene thinfilm by electrochemical deposition and its read-writable properties by electrochemical treatments. Electrochim. Acta 2014, 116, 69−77. (33) Qiu, D. F.; Zhao, Q.; Bao, X. Y.; Liu, K. C.; Wang, H. W.; Guo, Y. C.; Zhang, L. F.; Zeng, J. L.; Wang, H. Electropolymerization and characterization of an alternatively conjugated donor-acceptor metallopolymer: poly-[Ru(4′-(4-(diphenylamino)phenyl)-2,2′:6′,2″-terpyridine)2]2+. Inorg. Chem. Commun. 2011, 14, 296−299. (34) Goodall, W.; Wild, K.; Arm, K. J.; Williams, J. A. G. The synthesis of 4′-aryl substituted terpyridines by Suzuki cross-coupling reactions: substituent effects on ligand fluorescence. J. Chem. Soc., Perkin Trans. 2002, 2, 1669−1681. (35) Xiao, L. X.; Xu, Y. Q.; Yan, M.; Galipeau, D.; Peng, X. J.; Yan, X. Z. Excitation-dependent fluorescence of triphenylamine-substituted tridentate pyridyl Ruthenium complexes. J. Phys. Chem. A 2010, 114, 9090−9097. (36) Fan, C. B.; Wang, X. M. (E)-3-[4-(Diphenylamino)phenyl]-1(pyridin-2-yl)prop-2-en-1-one. Acta Crystallogr., Sect. E: Struct. Rep. Online 2012, 68, o417. (37) Fan, C. B.; Wang, X. M.; Ding, P.; Wang, J. J.; Liang, Z. Q.; Tao, X. T. Synthesis,photophysical and iron-sensing properties of terpyridyl-based triphenylamine derivatives. Dyes Pigm. 2012, 95, 757−767. (38) Liu, Y.; Wang, Y. F.; Guo, H. P.; Zhu, M. X.; Li, C.; Peng, J. B.; Zhu, W. G.; Cao, Y. Synthesis and optoelectronic characterization of a monochromic red-emitting europium(III) complex containing triphenylamine-functionalized phenanthroline. J. Phys. Chem. C 2011, 115, 4209−4216. (39) Piao, X. J.; Zou, Y.; Wu, J. C.; Li, C. Y.; Yi, T. Multiresponsive switchable diarylethene and its application in bioimaging. Org. Lett. 2009, 11, 3818−3821. (40) Wang, Z. M.; Wang, X. M.; Zhao, J. F.; Jiang, W. L.; Yang, P.; Fang, X. Y.; Zhou, M. Y.; Cheng, M. H. Cooperative enhancement of two-photon absorption based on electron coupling in triphenylaminebranching chromophore. Dyes Pigm. 2008, 79, 145−152. (41) Huang, L. T.; Yen, H. J.; Chang, C. W.; Liou, G. S. Red, green, and blue electrochromism in ambipolar poly(amine−amide−imide)s based on electroactive tetraphenyl-p-phenylenediamine units. J. Polym. Sci., Part A: Polym. Chem. 2010, 48, 4747−4757. (42) Maier, A.; Rabindranath, A. R.; Tieke, B. Coordinative Supramolecular Assembly of Electrochromic Films Based on Metal Ion Complexes of Polyiminofluorene with Terpyridine Substituent Groups. Chem. Mater. 2009, 21, 3668−3676. (43) Yao, C.-J.; Zhong, Y.-W.; Nie, H.-J.; Abruña, H. D.; Yao, J. N. Near-IR electrochromism in electropolymerized films of a biscyclometalated ruthenium complex bridged by 1,2,4,5-tetra(2-pyridyl)benzene. J. Am. Chem. Soc. 2011, 133, 20720−20723.

(44) Motoyama, K.; Li, H.; Koike, T.; Hatakeyama, M.; Yokojima, S.; Nakamura, S.; Akita, M. Photo- and electro-chromic organometallics with dithienylethene (DTE) linker, L2CpM-DTE-MCpL2: dually stimuli-responsive molecular switch. Dalton Trans. 2011, 40, 10643− 10657. (45) Leung, M.-k.; Chou, M.-Y.; Su, Y. O.; Chiang, C. L.; Chen, H.L.; Yang, C. F.; Yang, C.-C.; Lin, C.-C.; Chen, H.-T. Diphenylamino group as an effective handle to conjugated donor-acceptor polymers through electropolymerization. Org. Lett. 2003, 5 (6), 839−842. (46) Andres, P. R.; Schubert, U. S. New functional polymers and materials based on 2,2′:6′,2″-terpyridine metal complexes. Adv. Mater. 2004, 16, 1043−1068. (47) Han, F. S.; Higuchi, M.; Kurth, D. G. Metallo-supramolecular polymers based on functionalized bis-terpyridines as novel electrochromic materials. Adv. Mater. 2007, 19, 3928−3931.

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Synthesis and Electrochromic Properties of New Terpyridine

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