Effect of Electron-Donating and Electron- Withdrawing Groups on their

Article pubs.acs.org/joc

Cite This: J. Org. Chem. XXXX, XXX, XXX−XXX

2,5-Diaryltellurophenes: Effect of Electron-Donating and ElectronWithdrawing Groups on their Optoelectronic Properties Noriyoshi Nagahora,* Shuhei Yahata, Shoko Goto, Kosei Shioji, and Kentaro Okuma* Department of Chemistry, Faculty of Science, Fukuoka University, Jonan-ku, Fukuoka 814-0180, Japan S Supporting Information *

ABSTRACT: The transformation of 1,2-bis(1-arylvinyl)ditellurides into 2,5-diaryltellurophenes by sequential ditelluride exchange and thermal intramolecular cyclization reactions is presented, and the optoelectronic properties of a series of 2,5diaryltellurophenes with both electron-donating and electron-withdrawing aryl substituents are disclosed. Furthermore, the multicolored emissive tellurophenes in solution at room temperature have been demonstrated.

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INTRODUCTION Synthetic routes to tellurophenes, i.e., the heavier homologues of thiophenes and selenophenes, have attracted substantial attention due to their unique properties.1−6 For instance, Seferos and co-workers have recently reported a π-extended polymer containing tellurophene or 2,2′-bitellurophene units that exhibit a narrow band gap (polymer A in Figure 1),7,8 and the preparation of 2,5-bifluorenyltellurophene B has also been achieved.9 Moreover, the low-band gap polymers containing tellurophene units were successfully synthesized.10−12 Soon thereafter, the synthesis of tellurophene-containing polymers C and D was reported, whose UV/vis absorption spectra exhibit large bathochromic shifts compared to those of the corresponding thiophene and selenophene derivatives.13,14 The groups of Shankar and Rivard have synthesized emissive tellurophene E (Figure 1),15 but although this tellurophene exhibited green phosphorescence in the solid-state or upon aggregation, emissive behavior in solution was not observed. Against this background, tellurophenes can be considered a useful platform for the development of photoelectronic molecular devices. The hitherto reported synthetic approaches to modify tellurophene frameworks can be broadly divided into the three categories: (i) reaction of 1,3-butadiynes with lithium (or sodium) tellurides, (ii) lithiation or stannylation of a parent tellurophene and subsequent cross-coupling with a transitionmetal complex, and (iii) treatment of metallacyclobutadienes with a divalent tellurium reagent. Since reports on the synthesis of tellurophene derivatives have been very limited over the last decades, investigations on such synthetic methods still remain scarce. Recently, we have disclosed the reactions of acetophenone hydrazones with tellurium tetrachloride, which afford 2,5diaryltellurophenes bearing a variety of aryl substituents; this unique and useful thermal transformation presents a new approach to tellurophene scaffolds.11 In order to fine-tune the optoelectronic properties of such π-conjugated tellurophene © XXXX American Chemical Society

molecules, we envisioned the following two strategies: (i) increasing the electron-donating/electron-withdrawing properties in these tellurophenes, which would be commensurate to the so-called, push−pull effect in dyes, wherein excitation involves an intramolecular charge transfer; this should result in a bathochromic shift of their UV/vis absorption and emission bands, and (ii) expanding their π-conjugated network may also lead to a bathochromic shift and enhanced molar extinction coefficients. Herein, we describe our research on the synthesis of 2,5-diaryltellurophenes that bear both electron-donating and electron-withdrawing groups. These 2,5-diaryltellurophenes were obtained from a thermal reaction of 1,2-bis(1-arylvinyl)ditellurides, and their experimentally observed optoelectronic properties could be rationalized on the basis of theoretical calculations.

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RESULTS AND DISCUSSION Synthesis of 2,5-Diaryltellurophenes with ElectronDonating and Electron-Withdrawing Groups. We synthesized four 2,5-diaryltellurophenes with differently substituted aryl groups, i.e., p-tolyl and p-anisyl (electron-donating), as well as p-nitrophenyl and p-cyanophenyl (electron-withdrawing). The synthetic route to tellurophenes 1ac−bd is based on exchange reactions of 1,2-bis(1-arylvinyl)ditellurides, followed by an intramolecular thermal cyclization (Scheme 1). Initially, the treatment of acetophenone hydrazones 2a−d with tellurium tetrachloride in the presence of 1,8-diazabicyclo[5.4.0]undec-7ene (DBU) afforded 1,2-bis(1-arylvinyl)ditellurides 3aa−dd in moderate yields, together with bis(1-arylvinyl)tellurides 4aa− dd (Scheme 2). When a 1:1 mixture of 3bb and 3dd in CDCl3 was left for 10 min at room temperature, ditelluride exchange product 3bd was detected by 1H NMR spectroscopy (Scheme 3 and Figure 2), which indicates that these ditellurides readily Received: November 16, 2017

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DOI: 10.1021/acs.joc.7b02906 J. Org. Chem. XXXX, XXX, XXX−XXX

Article

The Journal of Organic Chemistry

Figure 1. Previously reported tellurophene derivatives and polymers containing a tellurophene moiety.

Scheme 1. Synthetic Route to Tellurophenes 1ac−bd

Scheme 2. Reactions of Acetophenone Hydrazones 2a−d with TeCl4 in the Presence of DBU

Scheme 3. Ditelluride Exchange Reaction between 1,2-Bis(1-arylvinyl)ditellurides 3bb and 3dd

B


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The Journal of Organic Chemistry Table 1. Thermolysis of a 1:1 Mixture of 1,2-Bis(1arylvinyl)ditellurides 3aa−dd

entry 1 2 3 4

Figure 2. 1H NMR spectra of CDCl3 solutions of (a) 1,2-bis(panisylvinyl)ditelluride (3bb), (b) 1,2-bis(p-nitrophenylvinyl)ditelluride (3dd), and (c) a 1:1 mixture of 3bb and 3dd recorded after 10 min at room temperature.

substrates 3aa (R1 = Me) 3bb (R1 = OMe) 3aa (R1 = Me) 3bb (R1 = OMe)

products (yield [%])

3cc (R2 = CN) 3cc (R2 = CN)

1aa (21) 1bb (16)

1cc (22) 1cc (18)

1ac (47) 1bc (37)

3dd (R2 = NO2) 3dd (R2 = NO2)

1aa (12)

1dd (16)

1ad (46)

1bb (14)

1dd (18)

1bd (38)

The emission spectra of 1ac−bd in degassed CH2Cl2 at room temperature were recorded, as shown in Figure 5. Emission maxima were observed at 448 (1ac), 471 (1bc), 593 (1ad), and 643 nm (1bd), corresponding to blue (1ac and 1bc), yellow (1ad), and orange emission (1bd). The emission maxima and the estimated Stokes shifts increase monotonically in the order 1ac < 1bc < 1ad < 1bd, which is in good agreement with the bathochromic shifts of the absorption bands. Meanwhile, the fluorescence quantum yields (ΦF) of 1.8−2.3% were determined for 1ac−bd in CH2Cl2 at room temperature. We also noted that no significant change of the emission spectra of 1ac−bd under an O2 atmosphere was confirmed. Moreover, the lifetime of the emissive behavior of 1ad was also determined by the emission decay experiment. The emission decay curve of 1ad revealed that the lifetime is estimated to be 10 ns (Figure S2, in Supporting Information), which is in the range for fluorescence.20 It should be noted that such a fluorescence behavior for 2,5-diaryltellurophenes 1ac− bd in solution at room temperature is unique, as is the finetuning of their emission wavelength from blue to orange. Subsequently, we examined the emission profiles of 1ad, which bears the effective electron-donating and electronwithdrawing aryl groups, in solvents with different polarity indexes, including toluene, chloroform, acetone, and acetonitrile. The corresponding spectra are shown in Figure 6, and relevant data are summarized in Table S3 (Supporting Information). Interestingly, in contrast to the trend observed for the absorption, the emission maxima shifted to longer wavelengths with an increasing solvent polarity, thus exhibiting a general positive solvatochromism. The solvatochromic data for 1ad was analyzed in a Lippert−Mataga plot (Figure 7), which revealed a linear trend for this tellurophene, commensurate with a general solvent effect in the excited state. Overall, these observations indicate that the excited state of 1ad is relatively polar and significantly affected by solvent effects. Theoretical Investigations on 2,5-Diaryltellurophenes with Both Electron-Donating and Electron-Withdrawing Groups. To gain insight into their electronic structure,

undergo dynamic exchange reactions in solution at room temperature.17 We have recently demonstrated that the thermal reactions of 1,2-bis(1-arylvinyl)ditellurides afford 2,5-diarylditellurides in good yields.16 These results inspired us to explore the synthesis of 2,5-diarylditellurides with both electron-donating and electron-withdrawing groups. Thus, a thermolysis of a mixture of the ditellurides 3aa, 3cc, and 3ac (1:1:2) in DMF under reflux conditions afforded the desired tellurophene 1ac in 47% isolated yield, together with tellurophenes 1aa and 1cc in 21% and 22% isolated yields, respectively (after chromatographic separation; entry 1, Table 1). In a similar manner, the novel 2,5-diaryltellurophenes 1ad, 1bc, and 1bd were obtained in 37%, 46%, and 38% yields, respectively (entries 2−4, Table 1). The molecular structure of 1bc, which bears p-anisyl and p-cyanophenyl groups, was confirmed by single-crystal X-ray diffraction analysis (Figure 3). Consequently, we have established that ditelluride exchange followed by thermal cyclizations of 1,2-bis(1-arylvinyl)ditellurides affords 2,5-diaryltellurophenes that contain both electron-donating and electron-withdrawing groups. Optoelectronic Properties of 2,5-Diaryltellurophenes with Both Electron-Donating and Electron-Withdrawing Groups. In order to elucidate the electronic structure of 1ac− bd, their UV/vis absorption spectra were recorded in CH2Cl2 (Figure 4) and the corresponding photophysical data are summarized in Table 2. Absorption maxima with large absorption coefficients at 371 (1ac), 380 (1bc), 403 (1ad), and 413 nm (1bd) were observed and assigned to π−π* transitions of the 2,5-diaryltellurophene chromophore. Compared to those of previously reported 2,5-diarylthiophenes and 2,5-diarylselenophenes,18,19 the maxima of tellurophenes 1ac− bd were bathochromically shifted, indicating a narrower HOMO−LUMO gap. Moreover, the magnitude of the bathochromic shift (1ac < 1bc < 1ad < 1bd) depends on the push−pull effect of the substituents and results in the lowering of the HOMO−LUMO gap. C


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Figure 3. Molecular structure of tellurophene 1bc with thermal ellipsoids set to 50% probability. Selected bond lengths [Å] and angles [°]: Te(1)− C(1) 2.081(10), Te(1)−C(4) 2.079(10), C(1)−C(2) 1.360(14), C(3)−C(4) 1.360(14), C(2)−C(3) 1.420(16), C(1)−Te(1)−C(4) 82.8(4), C(2)−C(1)−Te(1) 108.8(8), C(3)−C(4)−Te(1) 109.7(8), C(4)−C(3)−C(2) 118.5(10), C(1)−C(2)−C(3) 120.1(10).

Figure 6. Emission spectra of 1ad in different solvents ([1ad] = 1.0 × 10−6 mol/L; λex = 410 nm). Figure 4. UV/Vis absorption spectra of 1ac (gray), 1bc (yellow), 1ad (blue), and 1bd (orange) in CH2Cl2 at room temperature.

Table 2. Photophysical Properties of Tellurophenes 1ac−bd absorption compound 1aa (R1 = R2 = Me) 1bb (R1 = R2 = OMe) 1cc (R1 = R2 = CN) 1dd (R1 = R2 = NO2) 1ac (R1 = Me, R2 = CN) 1bc (R1 = OMe, R2 = CN) 1ad (R1 = Me, R2 = NO2) 1bd (R1 = OMe, R2 = NO2) a

λmax [nm]

ε

emission λmax [nm]

349 358

18 800 20 400

a a

365 404

27 900 28 200

a a

371

23 000

380

Stokes shift [cm−1]

ΦF [%]

448

3990

2.3

19 800

471

5080

1.9

403

17 500

593

7950

1.8

413

27 600

643

8660

2.1

Figure 7. Lippert−Mataga plot for 1ad.

theoretical calculations were carried out on 1ac−bd and 1aa− dd. These structures were optimized using DFT methods implemented in Gaussian 09.21 We selected the B3LYP functional with 6-31G(d) (C, H, N, O) or LANL2DZ (Te) basis sets. The theoretically derived HOMOs and LUMOs of these tellurophenes are shown in Figures 8 and 9. Both the HOMOs and LUMOs of 1aa−dd are delocalized over the πorbitals of the molecules (Figure 8). In contrast, in the case of 1ac−bd, the HOMO is predominantly localized on the πorbitals of the tellurophene moiety and the electron-donating panisyl or p-tolyl group, whereas the LUMO is localized on the π*-orbital of the tellurophene unit and the electron-withdrawing p-cyanophenyl or p-nitrophenyl fragment (Figure 9). It can thus be concluded that the incorporation of substituents with electron-donating and electron-withdrawing groups in the tellurophene framework stabilizes the LUMO. Consequently, the HOMO−LUMO transitions in 1ac−bd are symmetryallowed ( f = 0.6316−0.8218) and exhibit a charge-transfer character, which is probably the reason for the experimentally observed susceptibility of the emission properties toward the solvent polarity.

The emissive in CH2Cl2 at room temperature was not detected.

Figure 5. Emission spectra of 1ac (gray), 1bc (yellow), 1ad (blue), and 1bd (orange) in CH2Cl2 at room temperature. Inset: photograph of CH2Cl2 solutions of 1ac−bd upon irradiation with UV light (λex = 365 nm).

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Figure 8. Theoretically calculated HOMOs and LUMOs (isovalue: 0.06) of 1aa−dd at the B3LYP/6-31G(d) (C, H, N, O) and B3LYP/LANL2DZ (Te) level of theory. Hydrogen atoms have been omitted for clarity (color code: carbon = gray; oxygen = red; nitrogen = blue; tellurium = orange). Green arrows represent the lowest-energy electron transitions with the corresponding oscillator strength calculated by TD-B3LYP/6-31G(d) (C, H, N, O) and TD-B3LYP/LANL2DZ (Te).

Figure 9. Theoretically calculated HOMOs and LUMOs (isovalue: 0.06) of 1ac−bd at the B3LYP/6-31G(d) (C, H, N, O) and B3LYP/LANL2DZ (Te) level of theory. Hydrogen atoms have been omitted for clarity (color code: carbon = gray; oxygen = red; nitrogen = blue; tellurium = orange). Green arrows represent the lowest-energy electron transitions with the corresponding oscillator strength calculated by TD-B3LYP/6-31G(d) (C, H, N, O) and TD-B3LYP/LANL2DZ (Te).

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internal standards for the 1H and 13C NMR spectra, respectively. The assignment of the signals was typically accomplished on the basis of 1D (homodecoupling and DEPT) and 2D (COSY, HMQC, and HMBC) NMR techniques. All 13C NMR experiments were performed using broad-band 1H decoupling unless otherwise stated. EI and ESITOF mass spectral data were obtained on a JEOL JMS-GCmateII and a JEOL JMS-T100CS spectrometer, respectively. Absorption and emission spectra were recorded on a JASCO V-550 UV/vis and a Hitachi F-7000 fluorescence spectrophotometer, respectively. Absolute quantum yields were obtained on a quantum efficiency measurement system QE-2000 by Otsuka Electronics. Elemental analysis was performed on a JM11 CHN corder by J-Science Lab. All melting points were determined on a Yanaco micromelting point apparatus or a Mettler Toledo MP90 melting point system and are uncorrected. Materials. All materials were purchased from chemical suppliers and used without further purification unless stated otherwise. All reactions were carried out under an inert atmosphere of argon or nitrogen. 1,2-Bis(1-p-tolylvinyl)ditelluride (3aa) and 2,5-diaryltellurophenes 1aa, 1bb, 1cc, and 1dd were prepared according to previously reported procedures.16 Synthesis of 1,2-Bis(1-p-tolylvinyl)ditelluride (3aa).16 A solution of 4′-methylacetophenone hydrazone (360 mg, 2.43 mmol) in CH2Cl2 (5 mL) was added to a suspension of TeCl4 (1.711 g, 6.35 mmol) and DBU (2.900 g, 19.05 mmol) in CH2Cl2 (15 mL) at room temperature. After stirring at room temperature for 2 h, water (30 mL) was added.

CONCLUSION We have successfully synthesized a series of novel 2,5diaryltellurophenes bearing both electron-donating and electron-withdrawing groups via dynamic ditelluride exchange followed by a thermal reaction of the thus obtained 1,2-bis(1arylvinyl)ditellurides. Their photophysical properties, including their emission behavior, have also been disclosed, and the precise tuning of the properties of these π-extended tellurophenes was achieved through the neighboring aryl groups. Specifically, the simultaneous introduction of both electron-donating and electron-withdrawing aryl groups in these tellurophenes resulted in a remarkable reduction of the HOMO−LUMO gap. The straightforward synthesis and unique properties of these π-electron systems containing a tellurophene core, constitute a powerful tool for the development of optoelectronic devices.

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EXPERIMENTAL SECTION

General. All solvents were purified by standard methods. Preparative thin-layer chromatography (PTLC) was performed on Merck silica gel 60 PF254. 1H NMR (400 MHz) and 13C NMR (101 Hz) spectra were recorded in CDCl3 on a Bruker Avance spectrometer using CHCl3 (δH = 7.26 ppm) and CDCl3 (δC = 77.0 ppm) as the E


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Anal. Calcd for C18H13NOTe: C, 55.88; H, 3.39; N, 3.62. Found: C, 55.70; H, 3.46; N, 3.49. Synthesis of 2-(p-Methylphenyl)-5-(p-nitrophenyl)tellurophene (1ad). A mixture of 1,2-bis(1-p-methylphenylvinyl)ditelluride (37 mg, 0.076 mmol) and 1,2-bis(1-p-nitrophenylvinyl)ditelluride (42 mg, 0.076 mmol) in DMF (3 mL) was stirred under reflux for 18 h and then allowed to cool to room temperature. All volatile substances were removed under reduced pressure, and the reaction mixture was separated by column chromatography on silica gel (CH2Cl2/hexane = 1:1, Rf = 0.50 for 1aa, Rf = 0.30 for 1ad, and Rf = 0.20 for 1dd) to afford 2,5-di(p-methylphenyl)tellurophene (1aa, 6.3 mg, 0.018 mmol, 12%), 2-(p-methylphenyl)-5-(p-nitrophenyl)tellurophene (1ad, 27 mg, 0.070 mmol, 46%), and 2,5-di(p-nitrophenyl)tellurophene (1dd, 20 mg, 0.024 mmol, 16%). 1ad: yellow solid; mp 245−246 °C; 1H NMR (CDCl3, 400 MHz) δ 2.37 (3H, s, CH3), 7.18 (2H, d, J = 8.0 Hz, ArH), 7.39 (2H, d, J = 8.0 Hz, ArH), 7.57 (2H, d, J = 8.8 Hz, ArH), 7.84 (1H, d, J = 4.4 Hz, ArH), 7.98 (1H, d, J = 4.4 Hz, ArH), 8.19 (2H, d, J = 8.8 Hz, ArH); 13C{1H} NMR (CDCl3, 101 MHz) δ 21.4 (CH3), 124.6 (CH), 126.9 (CH), 127.0 (CH), 129.9 (CH), 133.7 (CH), 136.8 (q-C), 137.0 (CH), 138.7 (q-C), 143.9 (q-C), 146.5 (qC), 146.7 (q-C), 152.9 (q-C); MS (EI+) m/z 393 (M+). Anal. Calcd for C17H13NO2Te: C, 52.24; H, 3.35; N, 3.58. Found: C, 51.92; H, 3.35; N, 3.51. Synthesis of 2-(p-Methoxyphenyl)-5-(p-nitrophenyl)tellurophene (1bd). A mixture of 1,2-bis(1-p-methoxyphenylvinyl)ditelluride (27 mg, 0.052 mmol) and 1,2-bis(1-p-nitrophenylvinyl)ditelluride (29 mg, 0.052 mmol) in DMF (3 mL) was stirred under reflux for 18 h and then allowed to cool to room temperature. All volatile substances were removed under reduced pressure, and the reaction mixture was separated by column chromatography on silica gel (CH2Cl2/hexane = 1:1, Rf = 0.35 for 1bb, Rf = 0.30 for 1bd, and Rf = 0.20 for 1dd) to afford 2,5-di(p-methoxyphenyl)tellurophene (1bb, 6.0 mg, 0.015 mmol, 14%), 2-(p-methoxyphenyl)-5-(p-nitrophenyl)tellurophene (1bd, 16 mg, 0.039 mmol, 38%), and 2,5-di(p-nitrophenyl)tellurophene (1dd, 8.0 mg, 0.019 mmol, 18%). 1bd: orange solid; mp 219−221 °C; 1H NMR (CDCl3, 400 MHz) δ 3.85 (3H, s, OCH3), 6.90 (2H, d, J = 8.8 Hz, ArH), 7.44 (2H, d, J = 8.8 Hz, ArH), 7.57 (2H, d, J = 8.8 Hz, ArH), 7.76 (1H, d, J = 4.4 Hz, ArH), 7.97 (1H, d, J = 4.4 Hz, ArH), 8.19 (2H, d, J = 8.8 Hz, ArH); 13C{1H} NMR (CDCl3, 101 MHz) δ 55.6 (CH3), 114.7 (CH), 124.6 (CH), 126.9 (CH), 128.2 (CH), 132.5 (q-C), 133.2 (CH), 137.0 (CH), 143.2 (qC), 146.51 (q-C), 146.65 (q-C), 152.6 (q-C), 160.1 (q-C); MS (EI+) m/z 409 (M+). Anal. Calcd for C17H13NO3Te: C, 50.18; H, 3.22; N, 3.44. Found: C, 49.88; H, 3.16; N, 3.52. X-ray Crystallographic Analysis of Tellurophene 1bc. Single crystals of tellurophene 1bc were obtained by slow recrystallization from a CH2Cl2/hexane solution at 4 °C. Intensity data were collected on a Rigaku Saturn CCD system with graphite-monochromated Mo Kα radiation (λ = 0.710 70 Å). The two independent molecules of 1bc in the asymmetric unit are depicted in Figure S1. Selected structural parameters and crystal data of 1bc are provided in Tables S1−S2, respectively. The structure was solved by direct method (SHELXT2014)22 and refined by full-matrix least-squares on F2 for all reflections (SHELXL-2014).23 All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were located following the AFIX instructions. The crystallographic data reported in this article have been deposited at the Cambridge Crystallographic Data Centre (CCDC) as supplementary publication no. CCDC-1815914. Copies of the data can be obtained free of charge via www.ccdc.cam.ac.uk/ conts/retrieving.html (or from the Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge, CB2 1EZ, UK; fax: + 44 1223 336033; or [email protected]).

The organic layer was extracted with CH2Cl2, dried over anhydrous sodium sulfate, and filtered. The filtrate was concentrated under reduced pressure and purified by column chromatography on silica gel (CH2Cl2/hexane = 1:1) to afford 1,2-bis(1-p-tolylvinyl)ditelluride (294 mg, 0.60 mmol, 49%) as a red/orange oil. Synthesis of 1,2-Bis(1-p-anisylvinyl)ditelluride (3bb). In a similar manner to the synthesis of 3aa, 1,2-bis(1-p-anisylvinyl)ditelluride was obtained in 43% as a red/orange oil. 3bb: 1H NMR (CDCl3, 400 MHz) δ 3.81 (CH3, s, 6H), 5.87 (CHH, s, 2H), 6.16 (CHH, s, 2H), 6.83 (ArH, d, J = 8.8 Hz, 4H), 7.37 (ArH, d, J = 8.8 Hz, 4H); 13C{1H} NMR (CDCl3, 101 MHz) δ 55.5 (CH3), 113.8 (CH), 120.1 (q-C), 125.9 (CH2), 129.3 (CH), 130.1 (q-C), 156.7 (q-C); HRMS (EI+) m/ z found 525.9434 [M+], calcd for C18H18O2130Te2 525.9431. Synthesis of 1,2-Bis(1-p-cyanophenylvinyl)ditelluride (3cc). In a similar manner to the synthesis of 3aa, 1,2-bis(1-p-cyanophenylvinyl)ditelluride was obtained in 41% as a red oil. 3cc: 1H NMR (CDCl3, 400 MHz) δ 5.97 (CHH, s, 2H), 6.17 (CHH, s, 2H), 7.47 (ArH, d, J = 8.4 Hz, 4H), 7.59 (ArH, d, J = 8.4 Hz, 4H); 13C{1H} NMR (CDCl3, 101 MHz) δ 111.9 (q-C), 118.2 (q-C), 118.7 (q-C), 128.7 (CH), 130.3 (CH2), 132.2 (CH), 147.3 (q-C); HRMS (EI+) m/z found 515.9121 [M+], calcd for C18H12N2130Te2 515.9125. Synthesis of 1,2-Bis(1-p-nitrophenylvinyl)ditelluride (3dd). In a similar manner to the synthesis of 3aa, 1,2-bis(1-p-nitrophenylvinyl)ditelluride was obtained in 45% as a red oil. 3dd: 1H NMR (CDCl3, 400 MHz) δ 6.02 (CHH, s, 2H), 6.20 (CHH, s, 2H), 7.49 (ArH, d, J = 8.8 Hz, 4H), 8.15 (ArH, d, J = 8.8 Hz, 4H); 13C{1H} NMR (CDCl3, 101 MHz) δ 117.7 (q-C), 123.7 (CH), 128.9 (CH), 130.9 (CH), 147.5 (q-C), 149.3 (q-C); HRMS (EI+) m/z found 555.8919 [M+], calcd for C16H12N2O4130Te2 555.8922. Synthesis of 2-(p-Methylphenyl)-5-(p-cyanophenyl)tellurophene (1ac). A mixture of 1,2-bis(1-p-methylphenylvinyl)ditelluride (29 mg, 0.059 mmol) and 1,2-bis(1-p-cyanophenylvinyl)ditelluride (30 mg, 0.059 mmol) in DMF (3 mL) was stirred under reflux for 18 h and then allowed to cool to room temperature. All volatile substances were removed under reduced pressure, and the reaction mixture was separated by column chromatography on silica gel (CH2Cl2/hexane = 1:1, Rf = 0.50 for 1aa, Rf = 0.30 for 1bc, and Rf = 0.20 for 1cc) to afford 2,5-di(p-methylphenyl)tellurophene (1aa, 9.0 mg, 0.025 mmol, 21%), 2-(p-methylphenyl)-5-(p-cyanophenyl)tellurophene (1ac, 21 mg, 0.056 mmol, 47%), and 2,5-di(p-cyanophenyl)tellurophene (1cc, 10 mg, 0.026 mmol, 22%). 1ac: pale yellow solid; mp 275−276 °C; 1H NMR (CDCl3, 400 MHz) δ 2.36 (3H, s, CH3), 7.17 (2H, d, J = 8.0 Hz, ArH), 7.38 (2H, d, J = 8.0 Hz, ArH), 7.53 (2H, d, J = 8.8 Hz, ArH), 7.61 (2H, d, J = 8.8 Hz, ArH), 7.81 (1H, d, J = 4.4 Hz, ArH), 7.92 (1H, d, J = 4.4 Hz, ArH); 13C{1H} NMR (CDCl3, 101 MHz) δ 21.4 (CH3), 110.6 (q-C), 119.1 (q-C), 126.9 (CH), 127.1 (CH), 129.9 (CH), 132.9 (CH), 133.6 (CH), 136.3 (CH), 136.9 (q-C), 138.5 (qC), 144.52 (q-C), 144.53 (q-C), 152.0 (q-C); MS (EI+) m/z 373 (M+). Anal. Calcd for C18H13NTe: C, 58.29; H, 3.53; N, 3.78. Found: C, 58.19; H, 3.52; N, 3.75. Synthesis of 2-(p-Methoxyphenyl)-5-(p-cyanophenyl)tellurophene (1bc). A mixture of 1,2-bis(1-p-methoxyphenylvinyl)ditelluride (42 mg, 0.080 mmol) and 1,2-bis(1-p-cyanophenylvinyl)ditelluride (41 mg, 0.080 mmol) in DMF (3 mL) was stirred under reflux for 18 h and then allowed to cool to room temperature. All volatile substances were removed under reduced pressure, and the reaction mixture was separated by column chromatography on silica gel (CH2Cl2/hexane = 1:1, Rf = 0.35 for 1bb, Rf = 0.30 for 1bc, and Rf = 0.20 for 1cc) to afford 2,5-di(p-methoxyphenyl)tellurophene (1bb, 10 mg, 0.026 mmol, 16%), 2-(p-methoxyphenyl)-5-(p-cyanophenyl)tellurophene (1bc, 23 mg, 0.059 mmol, 37%), and 2,5-di(pcyanophenyl)tellurophene (1cc, 11 mg, 0.029 mmol, 18%). 1bc: yellowish green solid; mp 256−257 °C; 1H NMR (CDCl3, 400 MHz) δ 3.84 (3H, s, OCH3), 6.90 (2H, d, J = 8.4 Hz, ArH), 7.42 (2H, d, J = 8.4 Hz, ArH), 7.52 (2H, d, J = 8.4 Hz, ArH), 7.61 (2H, d, J = 8.4 Hz, ArH), 7.73 (1H, d, J = 4.4 Hz, ArH), 7.91 (1H, d, J = 4.4 Hz, ArH); 13 C{1H} NMR (CDCl3, 101 MHz) δ 55.6 (CH3), 110.5 (q-C), 114.6 (CH), 119.1 (q-C), 127.1 (CH), 128.2 (CH), 129.9 (CH), 132.5 (qC), 132.9 (CH), 133.0 (CH), 136.3 (CH), 143.9 (q-C), 144.52 (q-C), 144.54 (q-C), 151.7 (q-C), 160.0 (q-C); MS (EI+) m/z 389 (M+).

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ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.7b02906. Copies of the 1H and 13C NMR spectra of all new compounds, X-ray diffraction analysis, photophysical data F


Article


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(20) Principles of Fluorescence Spectroscopy; Lakowicz, J. R., Ed.; Springer: New York, 2010. (21) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, Ö .; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09, revision C.01; Gaussian, Inc.: Wallingford, CT, 2009. (22) Sheldrick, G. M. Acta Crystallogr., Sect. C: Struct. Chem. 2015, 71, 3−8. (23) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found. Adv. 2015, 71, 3−8.

for tellurophene 1ad, and the results of the theoretical calculations (PDF) Crystallographic information for 1bc (CIF)

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Noriyoshi Nagahora: 0000-0002-9663-0677 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was partially supported by the Collaborative Research Program of the Institute for Chemical Research, Kyoto University (grant nos. 2016-96 and 2017-101) and the Grant-in-Aid for Scientific Research (C) (JP16K05709) from the Japan Society for the Promotion of Science. The authors are grateful to Professor T. Sasamori (Nagoya City University, Japan) for the analysis of the X-ray diffraction and to Professor Y. Nibu and Dr. Y. Yamada (Fukuoka University, Japan) for the analysis of the emission behavior.

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REFERENCES

(1) Rivard, E. Chem. Lett. 2015, 44, 730−736. (2) Chivers, T.; Laitinen, R. S. Chem. Soc. Rev. 2015, 44, 1725−1739. (3) Carrera, E. I.; Seferos, D. S. Macromolecules 2015, 48, 297−308. (4) Parke, S. M.; Boone, M. P.; Rivard, E. Chem. Commun. 2016, 52, 9485−9505. (5) Carrera, E. I.; Lanterna, A. E.; Lough, A. J.; Scaiano, J. C.; Seferos, D. S. J. Am. Chem. Soc. 2016, 138, 2678−2689. (6) Egalahewa, S.; Albayer, M.; Aprile, A.; Dutton, J. L. Inorg. Chem. 2017, 56, 1282−1288. (7) Jahnke, A. A.; Howe, G.; Seferos, D. S. Angew. Chem., Int. Ed. 2010, 49, 10140−10144. (8) McCormick, T. M.; Jahnke, A. A.; Lough, A. J.; Seferos, D. S. J. Am. Chem. Soc. 2012, 134, 3542−3548. (9) Jahnke, A. A.; Djukic, B.; McCormick, T. M.; Domingo, E. B.; Hellmann, C.; Lee, Y.; Seferos, D. S. J. Am. Chem. Soc. 2013, 135, 951−954. (10) Park, Y. S.; Wu, Q.; Nam, C.-Y.; Grubbs, R. B. Angew. Chem., Int. Ed. 2014, 53, 10691−10695. (11) He, G.; Kang, L.; Delgado, W. T.; Shynkaruk, O.; Ferguson, M. J.; McDonald, R.; Rivard, E. J. Am. Chem. Soc. 2013, 135, 5360−5363. (12) Park, Y. S.; Kale, T. S.; Nam, C.-Y.; Choi, D.; Grubbs, R. B. Chem. Commun. 2014, 50, 7964−7967. (13) Planells, M.; Schroeder, B. C.; McCulloch, I. Macromolecules 2014, 47, 5889−5894. (14) Al-Hashimi, M.; Han, Y.; Smith, J.; Bazzi, H. S.; Alqaradawi, S. Y. A.; Watkins, S. E.; Anthopoulos, T. D.; Heeney, M. Chem. Sci. 2016, 7, 1093−1099. (15) He, G.; Delgado, W. T.; Schatz, D. J.; Merten, C.; Mohammadpour, A.; Mayr, L.; Ferguson, M. J.; McDonald, R.; Brown, A.; Shankar, K.; Rivard, E. Angew. Chem., Int. Ed. 2014, 53, 4587−4591. (16) Okuma, K.; Yahata, S.; Nagahora, N.; Shioji, K. Chem. Lett. 2017, 46, 405−407. (17) Jin, Y.; Yu, C.; Denman, R. J.; Zhang, W. Chem. Soc. Rev. 2013, 42, 6634−6654. (18) Kirsch, G.; Prim, D.; Leising, F.; Mignani, G. J. Heterocycl. Chem. 1994, 31, 1005−1009. (19) Prim, D.; Joseph, D.; Kirsch, G. Phosphorus, Sulfur Silicon Relat. Elem. 1994, 91, 137−143. G


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