Furan-based diketopyrrolopyrrole chromophores: Tuning the spectroscopic, electrochemical and aggregation-induced fluorescent properties with various intramolecular donor-acceptor spacers

Accepted Manuscript Furan-based diketopyrrolopyrrole chromophores: Tuning the spectroscopic, electrochemical and aggregation-induced fluorescent properties with various intramolecular donor-acceptor spacers Tao Tao, Liang Chen, Hui Cao, Min-Dong Chen, Wei Huang PII:

S0022-2860(17)30463-5

DOI:

10.1016/j.molstruc.2017.04.021

Reference:

MOLSTR 23643

To appear in:

Journal of Molecular Structure

Received Date: 18 January 2017 Revised Date:

11 March 2017

Accepted Date: 10 April 2017

Please cite this article as: T. Tao, L. Chen, H. Cao, M.-D. Chen, W. Huang, Furan-based diketopyrrolopyrrole chromophores: Tuning the spectroscopic, electrochemical and aggregationinduced fluorescent properties with various intramolecular donor-acceptor spacers, Journal of Molecular Structure (2017), doi: 10.1016/j.molstruc.2017.04.021. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Graphical Abstract

Furan-based diketopyrrolopyrrole chromophores: Tuning the spectroscopic, electrochemical and

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aggregation-induced fluorescent properties with various intramolecular donor-acceptor spacers

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Tao Tao,* Liang Chen, Hui Cao, Min-Dong Chen, Wei Huang

A family of furan-based diketopyrrolopyrrole chromophores, which presents red fluorescent characteristic properties with the emission maximum at 709 nm, has effective π-conjugated systems and adjustable

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electronic properties.

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Furan-based

diketopyrrolopyrrole

chromophores:

Tuning

the

spectroscopic, electrochemical and aggregation-induced fluorescent properties with various intramolecular donor-acceptor spacers

a

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Tao Tao,a,b * Liang Chen,a Hui Cao,a Min-Dong Chen,a Wei Huangb

Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution

Control, Collaborative Innovation Center of Atmospheric Environment and

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Equipment Technology, School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, P. R. China b

State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical

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Engineering, Nanjing University, Nanjing 210093, P. R. China

Tel: +86-25-58731090, Fax: +86-25-58731090. E-mail: [email protected]

* Correspondence to: T. Tao.

ABSTRACT

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A family of furan-based diketopyrrolopyrrole chromophores, which comprise different donor or acceptor spacers, was synthesized by classic Suzuki-Miyaura reactions

between

dibrominated

diketopyrrolopyrrole

intermediate

and

five

substituted aromatic boronic acids. They have the same π-extended unit and different

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pyridyl, thienyl and triarylamino tails with various intramolecular donor-acceptor spacers. Furthermore, absorption and emission spectral studies reveal that all dyes show extraordinarily large molar absorption coefficients (εmax = 22 400–120 000

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L·mol–1·cm–1) and high luminescence quantum yields (Φs = 27–88%). Moreover, the

TGA studies indicate that the triarylamino-extended compounds have excellent thermal stabilities. A systematical investigation has been carried out, including energy

gap correlation among optical, electrochemical and computational data. All the targeted chromophores exhibit potential applications in luminescent materials and optoelectronic devices. Keywords: Diketopyrrolopyrroles; Syntheses; Photophysics; Electrochemistry; DFT Computations

1

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1. Introduction

After decades of development, organic π-conjugated materials [1–3] have been

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studied in optoelectronics, which have demonstrated their fascinating applications including luminescent materials [4,5], photodetectors [6,7], organic solar cells [8–10],

organic field-effect transistors [11,12], and biological molecular probes [13,14].

Compared with the conjugated polymers, the small molecules have many advantages such as monodispersity, well-defined chemical structure, and easier functionalization

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[15]. However, how to design and utilize π-extended organic small molecules for fabricating electronic materials have been challenging problems.

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Recently, many scientific efforts have been carried out to develop the semiconducting π-conjugated materials, such as acene [16,17], thiophene [18,19], thiazole [20–23], furan [24,25], 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) [26,27] and diketopyrrolopyrrole [28–31], which might have the numerous advantages such as excellent thermal stabilities, large absorption coefficients and high fluorescence quantum yields. Moreover, the alternating electron-withdrawing and electron-donating arrangement can cause the hybridization of the frontier molecular

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orbitals, especially the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) [32]. Also, core-embedded method can finely tune the size, symmetry, conformation, spectroscopic and electrochemical properties of the conjugated molecular materials [33,34]. It is for sure that increasing the

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push-pull electronic donor/acceptor strengths in general would be a more effective method than purely enlarging the molecular lengths of π-conjugated systems from an

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energy gap engineering perspective [32,35]. Numerous soluble thiophene molecules with different groups have been described

in our previous work, which reveal blue or yellow fluorescent characteristics [36]. However, red diketopyrrolopyrrole dyes have narrow energy gaps because of the particular quinoid structure, which has attracted the attention of chemists [28–31,37–47].

Furthermore,

research

on

the

thiophene-based

[37–42]

diketopyrrolopyrrole units has been more than those on the furan-based [43–47] counterparts. Herein, we have improved our work on the furan-based red fluorescent molecules with the distinguishable intramolecular donor-acceptor groups, namely 2

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pyridyl,

thienyl

and

triarylamino

tails

(Scheme 1).

Compared

with

the

thiophene-based diketopyrrolopyrrole molecules, furan-based derivatives have many advantages including their easier biodegradation, lower aromaticity, better solubility, smaller molecular weight, and higher photoluminescent quantum efficiency without

[please insert Scheme 1 here]

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fluorescence quenching from spin-orbital coupling [48,49].

The aim of combing the electron-deficient diketopyrrolopyrrole block and

intramolecular push-pull substituents is not only to tune its π-conjugated structure but

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also to explore the relationship between structure and property. We focus on syntheses, spectroscopic, electrochemical and aggregation-induced fluorescent properties of a

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series of furan-embedded diketopyrrolopyrrole chromophores with the emission maximum at 709 nm in this paper. A systematical investigation has been carried out, including energy gap correlation among optical, electrochemical and computational data.

2. Experimental section

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2.1. General Synthetic Procedure of Diketopyrrolopyrrole Compounds 3–7 Syntheses of diketopyrrolopyrrole compounds 1–7 can be seen in the Supporting Information for details. General procedure of compounds 3–7 follows. A mixture of dye 2 (0.59 g, 1.00 mmol), Cs2CO3 (0.72 g, 2.20 mmol), [Pd(PPh3)4] (0.06 g, 0.05

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mmol), substituted aromatic boronic acids (2.20 mmol), toluene (40 mL) and water (5 mL) was degassed for 10 min and heated to reflux for 18 h. CHCl3 (60 mL) was

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added, and the organic phase was washed with brine, separated, and dried over anhydrous Na2SO4. The filtrate was evaporated, and the residue was purified by column chromatography over silica gel using hexane and CH2Cl2 (v/v = 1:1) as the eluent to give target products 3–7 as red solid in 75–93% yield. 2.1.1. Compound 3. Yield: 91%. M. p. > 300 °C. 1H NMR (300 MHz, CDCl3): δ 8.70 (d, 4H, J = 6.1 Hz, pyridine), 8.42 (d, 2H, J = 3.9 Hz, furan), 7.57 (d, 4H, J = 6.1 Hz, pyridine), 7.17 (d, 2H, J = 3.9 Hz, furan), 4.21 (t, 4H, n-hexyl), 1.87-1.77 (m, 4H, n-hexyl), 1.53-1.44 (m, 4H, n-hexyl), 1.38-1.25 (m, 8H, n-hexyl), 0.87 (t, 6H, n-hexyl). FT−IR (KBr pellets, cm−1): 3401 (b), 3133 (b), 1685 (m), 1663 (m), 1604 3

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(m), 1401 (vs), 1281 (w), 1165 (w), 1114 (m), 1030 (m), 819 (w), 684 (w), 564 (m), 547 (m). ESI–MS (m/z): calcd for [C36H38N4O4]+: 590.7. Found: 591.5. Anal. calcd for C36H38N4O4: C, 73.20; H, 6.48; N, 9.48 %. Found: C, 72.98; H, 6.52; N, 9.40 %.

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2.1.2. Compound 4. Yield: 75%. M. p. > 300 °C. 1H NMR (300 MHz, CDCl3): δ 8.41 (d, 2H, J = 3.4 Hz, furan), 7.40-7.36 (m, 4H, thiophene), 7.11 (t, 2H, thiophene), 6.82 (d, 2H, J = 3.9 Hz, furan), 4.19 (t, 4H, n-hexyl), 1.83-1.78 (m, 4H, n-hexyl), 1.52-1.47 (m, 4H, n-hexyl), 1.35-1.26 (m, 8H, n-hexyl), 0.87 (t, 6H, n-hexyl). FT−IR (KBr

pellets, cm−1): 3402 (b), 3134 (b), 1689 (m), 1663 (m), 1609 (m), 1567 (w), 1398 (vs),

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1104 (m), 1056 (m), 1030 (m), 892 (w), 818 (w), 688 (m), 562 (m). ESI–MS (m/z): calcd for [C34H36N2O4S2]+: 600.8. Found: 601.5. Anal. calcd for C34H36N2O4S2: C,

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67.97; H, 6.04; N, 4.66 %. Found: C, 67.77; H, 6.12; N, 4.62 %.

2.1.3. Compound 5. Yield: 81%. M. p. > 300 °C. 1H NMR (300 MHz, CDCl3): δ 8.49 (d, 2H, J = 3.8 Hz, furan), 8.44 (s, 2H, carbazole), 8.16 (d, 2H, J = 7.7 Hz, carbazole), 7.75 (d, 2H, J = 8.7 Hz, carbazole), 7.63-7.49 (m, 10H, carbazole+benzene), 7.43-7.33 (m, 8H, carbazole+benzene), 6.98 (d, 2H, J = 3.8 Hz, furan), 4.29 (t, 4H, n-hexyl), 1.96-1.86 (m, 4H, n-hexyl), 1.66-1.58 (m, 4H, n-hexyl), 1.43-1.28 (m, 8H,

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n-hexyl), 0.85 (t, 6H, n-hexyl). FT−IR (KBr pellets, cm−1): 3404 (b), 3130 (b), 1685 (m), 1663 (m), 1593 (m), 1501 (m), 1400 (vs), 1278 (w), 1228 (m), 1175 (w), 1100 (m), 1027 (m), 791 (w), 734 (w), 699 (w), 563 (m). ESI–MS (m/z): calcd for [C62H54N4O4]+: 919.1. Found: 919.6. Anal. calcd for C62H54N4O4: C, 81.02; H, 5.92;

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N, 6.10 %. Found: C, 80.84; H, 5.96; N, 6.02 %.

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2.1.4. Compound 6. Yield: 89%. M. p. > 300 °C. 1H NMR (300 MHz, CDCl3): δ 8.48 (d, 2H, J = 3.8 Hz, furan), 8.17 (d, 4H, J = 7.6 Hz, benzene), 8.00 (d, 4H, J = 8.5 Hz, carbazole), 7.70 (d, 4H, J = 8.5 Hz, carbazole), 7.50-7.41 (m, 8H, carbazole+benzene),

7.32 (t, 4H, carbazole), 7.09 (d, 2H, J = 3.8 Hz, furan), 4.29 (t, 4H, n-hexyl),

1.92-1.87 (m, 4H, n-hexyl), 1.54-1.48 (m, 4H, n-hexyl), 1.38-1.28 (m, 8H, n-hexyl), 0.88 (t, 6H, n-hexyl). FT−IR (KBr pellets, cm−1): 3406 (b), 3133 (b), 1684 (m), 1662 (m), 1605 (m), 1400 (vs), 1104 (m), 1047 (w), 752 (w), 612 (w), 557 (m). ESI–MS (m/z): calcd for [C62H54N4O4]+: 919.1. Found: 919.6. Anal. calcd for C62H54N4O4: C, 81.02; H, 5.92; N, 6.10 %. Found: C, 80.80; H, 5.99; N, 6.01 %. 4

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2.1.5. Compound 7. Yield: 93%. M. p. > 300 °C. 1H NMR (300 MHz, CDCl3): δ 8.38 (s, 2H, furan), 7.60 (d, 4H, J = 7.8 Hz, triphenylamino), 7.30 (t, 8H, triphenylamino), 7.15-7.06 (m, 16H, triphenylamino), 6.84 (s, 2H, furan), 4.20 (t, 4H, n-hexyl), 1.85-1.75 (m, 4H, n-hexyl), 1.49-1.39 (m, 4H, n-hexyl), 1.33-1.23 (m, 8H, n-hexyl),

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0.81 (t, 6H, n-hexyl). FT−IR (KBr pellets, cm−1): 3403 (b), 3136 (b), 1687 (m), 1663 (m), 1608 (m), 1408 (vs), 1161 (w), 1113 (m), 1061 (m), 613 (w), 565 (m). ESI–MS (m/z): calcd for [C62H58N4O4]+: 923.2. Found: 923.8. Anal. calcd for C62H58N4O4: C, 80.67; H, 6.33; N, 6.07 %. Found: C, 80.43; H, 6.39; N, 6.01 %.

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2.2. Computational Details

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All calculations were carried out with Gaussian 09 programs [50]. The geometries of dyes 1−7 were fully optimized and calculated by the B3LYP method and 6-31G* basis set. The structural files 2−7 were obtained by the substituent-modified approach based on the single-crystal structure of compound 1 [51] as the starting geometry. The methyl groups take the place of the n-hexyl groups in order to simplify computations because the normal replacement is not expected to

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change the results and the trends remarkably [52].

3. Results and discussion

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3.1. Syntheses and Spectral Characterizations

According to the routes shown in Scheme 1, compounds 3–7 were prepared from

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various substituted aromatic boronic acids and the dibrominated diketopyrrolopyrrole intermediate 2 (Supporting Information) by Suzuki–Miyaura reactions in high yields ranging from 75 to 93%. This family has excellent π-extended systems with

A–π–A–π–A or D–π–A–π–D structures as well as distinguishable pyridyl, thienyl, 9-phenyl-9H-carbazol-3-yl, 4-(diphenylamino)phenyl and 4-(9H-carbazol-9-yl)phenyl

tails. As shown in Fig. SI1–7 (Supporting Information), furan decorated diketopyrrolopyrrole dyes 1–7 have been characterized by 1H NMR, FT–IR, EA, UV–Vis and ESI–MS spectra methods including their aggregation-induced fluorescence behaviors. The introduction of two n-hexyl groups on the diketopyrrolopyrrole ring can easily form the target chromophores and effectively 5

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increase the solubility. As shown in Fig. 1, electronic absorption and fluorescence emission spectra of dyes 1–7 have been recorded in dichloromethane solutions. Seven compounds show the double peak absorptions at 498–630 nm in UV–Vis spectra corresponding to the

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π–π∗ transitions within the whole conjugated molecules. As the conjugated length is increased, the maximum absorption peaks (λmax) are shifted to lower energy bands. For

instance, the absorption peak λmax shows bathochromic shift of approximately 100 nm in

dye 7 compared with the π–π∗ transition of compound 1 largely because of the conjugated length effect of two triphenylamino groups. It is noted that the maximum absorption

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peak of isomer 5 (λmax = 621 nm) is bigger than that of isomer 6 (λmax = 605 nm), which may be due to the stronger electron-donating group. Furthermore, compounds 1–7

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present very high molecular absorption coefficients. For example, the maximum molar extinction coefficients (εmax) of compounds 3, 4 and 7 are 85 600, 85 400 and 120 000 L·mol–1·cm–1, respectively.

More importantly, this family of symmetrical diketopyrrolopyrrole dyes is fluorescent characteristic from orange to dark red, showing the double peak characteristic emissions at 547–709 nm. Fluorescence emissions of dyes 1 and 7 can be found at λmax = 547 and 665 nm, indicating a remarkable bathochromic shift of 118 nm,

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where dye 7 exhibits a bigger Stokes shift than dye 1 bearing no substituent at 5,5’-positions of furan rings. In particular, compound 6 presents the extraordinarily strong peaks at 624 and 674 nm with the fluorescence quantum yield (Φs) of 88% (rhodamine B Φstd = 65%, Supporting Information for details). Also, the conjugated

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diketopyrrolopyrrole molecules 1–7 have large molar absorption coefficients (εmax > 22 000 L·mol–1·cm–1) and high quantum yields (Φs > 27%) owing to the intramolecular

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push-pull structures.

[please insert Fig. 1 here] [please insert Table 1 here]

3.2. Aggregation-induced behaviors Considering that the strong fluorescence responses for the diketopyrrolopyrrole dyes in their dichloromethane solutions, both the photophysical behaviors in aqueous mixtures and those in the aggregated state have been investigated as shown in Fig. 2 and

Fig.

SI8–14.

As

what

can

be

seen

in

Fig.

2a,

the

4-(9H-carbazol-9-yl)phenyl-extended compound 6 has the highest quantum yields in 6

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this family (λmax = 603 nm in THF solution). As the water volume fractions (fw) increases, the molar absorption coefficients decreases at first (fw = 0–40%), then a new band at 640 nm is observed with a bathochromic shift of 37 nm (fw = 50–90%). Simultaneously, the high-energy absorption peak λmax shows a bathochromic shift from

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341 to 351 nm. With the addition of fw, the emission bands decreased due to aggregation-caused quenching (ACQ) effect [53–55], while the emission peaks show

a tiny red-shift from 620 to 624 nm as depicted in Fig. 2b. The picture of the THF/H2O mixtures with different fw ranging from 0% to 90% was shown in Fig. 2c. In THF

solutions (fw = 0%), dye 6 exhibits a purple color. However, when fw = 90%, the

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quenching percentage is about 100% and the color of the mixtures alters to blue, indicating an interestingly solvatochromic phenomenon.

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To investigate the ACQ effect, fluorescence emission intensities of dyes 1−7 versus the variation of fw are summarized in Fig. 3 (see the Supporting Information for details). It is interesting that different ACQ behaviors are observed based on the fast/slow effect of water volume fractions. When the water content is below 70%, the emission peak at 544 nm slowly decreased without significant change in dye 1. However, the fluorescence intensity sharply decreased when fw > 70% was added. Dye 2 shows analogous ACQ characteristic as that of compound 1. Differently, when

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a small amount of water (fw = 0–40%) was added, the emission peak of dye 5 fastly decreased. Quantitatively speaking, the quenching percentage is 98% when fw = 50% based on the intensity of dye 5 at 635 nm. Therefore, according to the fast/slow effect, compounds 6 and 7 exhibit similar ACQ behaviors as that of dye 5. It might be not

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only owing to the small solubility of triarylamino-functionalized dyes 5–7 in the corresponding THF/water mixtures, but also because of fluorescence quenching in the

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aggregated states, resulting in this fast ACQ phenomenon. [please insert Fig. 2 here] [please insert Fig. 3 here]

3.3. Thermal Stabilities

Thermal stability of π-conjugated dyes is an important parameter for impacting on the device performance. Td10 (10% weight-loss temperature) data released by the TGA measurements shows that seven furan decorated diketopyrrolopyrrole dyes have a good thermal durability. As shown in Fig. 4, the Td10 values for dyes 1−7 are from 7

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217 to 415 °C. Also, the thienyl- and pyridyl-functionalized derivatives 3 and 4 show higher heat resistance compared with no substituent furan-based diketopyrrolopyrrole dyes 1 and 2. In particular, the Td10 values for the triarylamino-extended compounds 5−7 are above 412 °C, indicating excellent thermal stability, which is consistent with

[please insert Fig. 4 here]

3.4. Electrochemical Properties

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our previous reported triarylamino chromophores [36].

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To study the redox activity and the relative energy level, the electrochemical behavior of furan-based diketopyrrolopyrrole dyes was recorded by the cyclic

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voltammetry measurements (CV, see Supporting Information for details). The onset reduction was measured relative to the Fc+/Fc couple, where an energy level of –4.40 eV versus vacuum was assumed [56,57]. Reduction onset potentials (Eredonset), half-wave potentials (E1/2) and HOMO/LUMO energy levels are summarized in Table 1. As illustrated in Fig. 5 and Fig. SI15, the well-defined oxidation and reduction peaks have been shown for all compounds in the CV measurements. As seen in Fig. 5b, the resultant oxidation E1/2 potentials for dye 4 are 0.66 and 0.98 V,

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respectively, while those reduction potentials are –0.98 and –1.26 V, respectively, which shows reversible redox response. In addition, compound 7 exhibits a reduction wave at E1/2 = −0.84 V, indicating the enough good electrochemical activity, which unit.

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may suggest the proof of the existence of the stable radical anion for triphenylamine

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[please insert Fig. 5 here]

3.5. Density Function Theory (DFT) Computations

To further show the essential distinction, DFT studies are carried out where the

fixed atom coordinates of dyes 1–7 are used for the HOMO and the LUMO gap (energy gap) computations. As depicted in Fig. 6, the HOMO–LUMO gaps for 2,5-dimethylpyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione and the methyl counterpart of

dye 1 are 3.35 and 2.50 eV, respectively, which indicate that the introduction of two furan groups on the 3,6-positions of diketopyrrolopyrrole ring can greatly decrease the 8

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HOMO–LUMO gaps. DFT results given in Table 1 reveal that the theoretical energy gaps for the counterparts of dye 2–4 and 7 are 2.44, 2.22, 2.15 and 2.11 eV, respectively, which are analogous to the result of electronic absorption spectra. Similarly, compared with compound 1, introducing the different electron-withdrawing

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or electron-donating groups on the 5,5’-position of furan rings not only can further decrease the HOMO–LUMO gaps, but also might finely tune the electronic structures in this case.

As shown in Fig. 7, according to the CV measurements and DFT computations from the theoretical and experimental perspectives, further analyses of the UV–Vis

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onset absorptions reveal that there are two respective linear relationships not only between the experimentally electrochemical and optical energy gaps (Egopt), but also

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between the theoretically calculated and optical ones for the furan-containing diketopyrrolopyrrole hybrids. On the one hand, the electrochemical energy gaps (Egec) underestimate the optical ones; while DFT calculated HOMO–LUMO energy gaps (Egcalcd) overestimate the optical ones. On the other hand, the linear relationships should prove that three types of energy gaps are in good agreement and mutual authentication. However, Egopt is in better agreement with Egcalcd. In spite of the numerical uncertainty, theoretical calculations can become a better and more powerful

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tool to guide the synthesis of future furan-based diketopyrrolopyrrole molecules. [please insert Fig. 6 here] [please insert Fig. 7 here]

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4. Conclusion

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In summary, we have prepared successfully a family of furan-based diketopyrrolopyrrole chromophores having different donor/acceptor chromophores. All of these furan-containing molecules have the same π-extended unit and different

pyridyl, thienyl and triarylamino tails with various intramolecular D–π–A–π–D or

A–π–A–π–A structures. Moreover, absorption and emission spectral studies reveal

that dyes 1–7 show extraordinarily large molar absorption coefficients (εmax = 22 400–120 000 L·mol–1·cm–1) and high luminescence quantum yields (Φs = 27–88%) by using rhodamine B as standard. It is interesting to mention that different ACQ behaviors are observed based on the fast/slow effect. Also, the electrochemical results demonstrate that these compounds exhibit excellent electrochemical activities, and the 9

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TGA studies indicate that the triarylamino-extended compounds 5−7 have good thermal stabilities. Finally, the theoretical and experimental studies reveal that there are two respective linear relationships not only between the electrochemical and optical energy gaps, but also between the calculated and optical ones for the

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furan-containing diketopyrrolopyrrole hybrids, which should prove that three types of energy gaps are in good agreement and mutual authentication. All the targeted chromophores

exhibit

potential

applications

optoelectronic devices.

luminescent

materials

and

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Acknowledgments

in

We acknowledge the National Natural Science Foundation of China (Nos.

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21501097 and 21473092), the Natural Science Foundation of Jiangsu Province (No. BK20150890), the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (No. 15KJB150021), the Jiangsu Specially-Appointed Professor Program (No. R2013T08) and the Startup Foundation for Introducing Talent of NUIST for financial aids. Meanwhile, this work was supported by A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), Jiangsu Joint Laboratory of Atmospheric Pollution Control, and

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Jiangsu Engineering Technology Research Center of Environmental Cleaning Materials.

Appendix A. Supplementary data

H NMR, CV, aggregation-induced absorption and emission spectra and

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1

luminescence quantum yield details for all furan decorated diketopyrrolopyrrole dyes

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are included. Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.molstruc.2017.

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Scheme 1. Synthetic routes for furan decorated diketopyrrolopyrrole dyes 1−7.

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Normalized UV−Vis absorption spectra (a) and fluorescence emission (b)

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dichloromethane solutions at room temperature with the same

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Fig. 2.

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UV–Vis absorption spectra (a), fluorescence emission spectra excited at 495 nm (b) and their visual photographs (c) for dye 6 in THF/water mixtures with the same concentration of 1.0 × 10–5 mol·L–1 and different

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water volume fractions (fw).

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Fig. 3.

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Line charts of fluorescence emission intensities of dyes 1−7 versus the compositions of aqueous mixtures at room temperature with the same

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concentration of 1.0 × 10–5 mol·L–1.

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Thermograms of furan decorated diketopyrrolopyrrole dyes 1−7.

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Fig. 5.

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Cyclic voltammograms of dyes 1 (a), 4 (b), 5 (c) and 7 (d) in dry CH2Cl2 (1.0 × 10–3 mol·L–1) containing 0.1 M Bu4NPF6 as the supporting electrolyte, AgCl/Ag as the reference electrode, Au as the working

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The potential was externally calibrated against the ferrocenium/ferrocene

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Fig. 6.

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Molecular orbital amplitude plots of HOMO and LUMO energy levels of the methyl counterparts of furan decorated diketopyrrolopyrrole dyes

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1−7 at the B3LYP/6-31G* level.

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Fig. 7.

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Energy gap correlation among optical, CV and computational data; Y-axis: electrochemical energy gaps (black) and DFT calculated

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HOMO–LUMO energy gaps (red).

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furan-based diketopyrrolopyrrole dyes 1−7.

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Table 1. UV–Vis absorption and fluorescence emission data, optical, electrochemical and calculated HOMO–LUMO energy gaps (Eg) for

λem (Фsa) [nm] 547, 591 (0.66)

Stokes shift [cm–1] 340

Td10b [°C] 273

Eredonsetc [V] −1.13

ELUMOd [eV] −3.27

EHOMOe [eV] −5.48

Egoptf [eV] 2.21

Egecg [eV] 1.73

Egcalcdh [eV] 2.50

2

510 (38 400), 552 (69 300)

564, 609 (0.69)

386

217

−1.11

−3.29

−5.47

2.18

1.70

2.44

3

546 (53 300), 593 (85 600)

609, 659 (0.48)

443

385

−1.01

−3.39

−5.40

2.01

1.60

2.22

4

560 (56 400), 607 (85 400)

625, 676 (0.27)

474

372

−0.90

−3.50

−5.46

1.96

1.46

2.15

5

571 (60 300), 621 (111 000)

643, 697 (0.65)

551

415

−0.73

−3.67

−5.59

1.92

1.31

2.18

6

557 (51 500), 605 (88 000)

624, 674 (0.88)

503

412

−0.93

−3.47

−5.44

1.97

1.55

2.16

7

582 (70 400), 630 (120 000)

665, 709 (0.32)

835

414

−0.70

−3.70

−5.56

1.86

1.30

2.11

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UV–Vis λmax (εmax) [nm (L·mol–1·cm–1)] 498 (22 400), 537 (38 600)

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Photoluminescence quantum yields by using rhodamine B as standard. 10% Weight-loss temperature. c Reduction onset potentials determined from CV. d Calculated from ELUMO = − (Eredonset + 4.40). e Calculated from EHOMO = ELUMO − Egopt. f Optical energy gaps determined from the UV–Vis absorptions in their dichloromethane solutions. g Electrochemical energy gaps determined from CV onset potentials. h The geometries are calculated by B3LYP method and 6-31G* basis set. b

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Highlights Structure-performance relationship for five red fluorescent dyes is done.




Aggregation-induced fluorescence of all compounds has been explored.




Excellent thermal stability of triarylamino-extended chromophores is described.




Energy gap correlation among optical, electrochemical and computational data is made.

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