Research Article www.acsami.org
Synthesis, Crystal Analyses, Physical Properties, and Electroluminescent Behavior of Unsymmetrical Heterotwistacenes Bo Lv,† Jinchong Xiao,*,† Jian Zhou,‡ Xi Zhang,† Jingdan Duan,† Wenming Su,‡ and Jianwen Zhao*,‡ †
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College of Chemistry and Environmental Science, Key Laboratory of Chemical Biology of Hebei Province, Hebei University, Baoding 071002, P.R. China ‡ Printable Electronics Research Centre, Suzhou Institute of Nanotech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215123, P.R. China S Supporting Information *
ABSTRACT: Four novel unsymmetrical heteroacenes containing fivemembered heterocycles (OPyN, TPyN, TPyC, TPyO) have been synthesized and characterized. The formed molecules exhibited twisted structures, determined by crystal analysis and showed blue/green fluorescence in dichloromethane and in thin film. Compounds OPyN and TPyN were selectively used as active ingredients, and the fabricated devices displayed promising electroluminescent performance.
KEYWORDS: polycyclic aromatic hydrocarbons, twistacene, single crystal, optical property, electroluminescence
1. INTRODUCTION Well-defined polyclic aromatic hydrocarbons (PAHs) can not only shed light upon the structure−properties relationship but also provide more chance to impressively develop the organic electronics with excellent performance containing organic light emitting diodes, organic field effect transistors, nonlinear optical devices and photovoltaic cells.1−10 However, some detracting behaviors such as tedious separation, ease of oxidation, and photosensitivity made the linear all-carbon acenes hard to handle.11 To envisage the challenges, the researchers presented two methods to approach them. One method is to introduce the substituents such as phenyl, pyrenyl, arylthio, and triisopropylsilylethynyl (TIPS) groups.12−18 Another one is to incorporate heteroatoms and heterocycles into the main acene skeletons.19−30 Apparently, the optical properties can be easily controlled by the numbers, position, and classes of the heteroatoms and heterocyles. Moreover, the synthesis, solubility, and film-forming ability can also be facilely optimized. This stimulated us to design and synthesize the novel π-conjugated systems comprising heteroatoms and heterocycles and investigate their physical properties. Recently, a series of twistacenes have been prepared that emit blue, green, and red fluorescence in the group of Pascal, Wudl, Zhang, and our lab.31−39 In addition, the fabricated devices based on these molecules can exhibit promising electroluminescent behaviors. Herein, we are more interested in the preparation of heterocycle-functionalized twistacens. In this context, we have further succeeded in the synthesis of four novel acenes (OPyN, TPyN, TPyC, TPyO) containing five-membered rings (Scheme 1). The structure−property relationship was studied in a comparative manner. The © 2016 American Chemical Society
obtained molecules presented twisted structures, determined by the single crystal analyses. Compounds OPyN, TPyC, and TPyO emit strong blue fluorescence while TPyN emits green light in dichloromethane. In addition, molecules OPyN and TPyN were used as active ingredients, and the prepared devices exhibited promising electroluminescent performance.
2. RESULTS AND DISCUSSION 2.1. Synthesis. Schemes 2 and 3 depict the synthetic route to compounds OPyN, TPyN, TPyC, and TPyO. Compounds 1 and 5 were achieved according to the published method in our lab.40,41 Suzuki coupling between 1 and 2-nitrophenylboronic acid (2) gave the intermediate 3. As expected, subsequent intramolecular Cadogan reductive cyclization in the presence of triethyl phosphate in 1,2-dichlorobenzene (ODCB) should produce the fused isomers 4 and OPyN. In fact, compound OPyN was obtained in 80% yield, which might be assigned to high reactivity. To get the linear structure TPyN, dibromosubstituted derivative 5 was selected as the starting material. Under the similar reaction condition, 2-bromophenylboronic acid (6) was treated with 5 catalyzed by Pd(PPh3)4/K2CO3 in THF/H2O mixture to afford the precursor 7. The target product TPyN was subsequently obtained through the Donaghey’s process with Pd(OAc)2/PCy3/KOtBu in reflux toluene when 7 was treated with aniline (8). The preparation of compounds TPyC and TPyO is shown in Scheme 3. After a similar Suzuki reaction from 1 and 2Received: June 16, 2016 Accepted: July 6, 2016 Published: July 6, 2016 18998
DOI: 10.1021/acsami.6b07304 ACS Appl. Mater. Interfaces 2016, 8, 18998−19003
Research Article
ACS Applied Materials & Interfaces Scheme 1. Molecular Structures of TBH, OPyN, PPyN, TPyC, and TPyO
Scheme 2. Synthetic Route to OPyN and TPyN
(methoxycarbonyl)benzeneboronic acid pinacol ester (9), light yellow solid 10 was obtained in 55% yield. Note that direct condensation of 10 in the presence of H2SO4 or PPA failed to generate the desired intermediate 14. An alternative strategy was selected. First, compound 10 was hydrolyzed with NaOH in methanol/isopropanol solution to give 11, which was then reacted with N,N′-carbonyldiimidazole (12) to afford the precursor 13 in high yield. The formed compound 13 reacted with TiCl4 followed by reduction reaction by KOH/NH2NH2 in diethylene glycol solution to generate TPyC as a yellow solid. Next, selective Suzuki reaction between 5 and the commercially available 2-methoxyphenylboronic acid (15) produced 16 in 51% yield. After removal of methyl group treated with BBr3 in anhydrous dichloromethane, the Oarylation of the presented precursor 17 yielded the ringformation product TPyO. These resulting compounds could be soluble in common solvents such as dichloromethane, chlroform, o-dichlorobenzene (ODCB), THF and were purified by column chramotagraphy and characterized by FT-IR, 1H NMR, 13 C NMR spectroscopy, and MALDI-TOF/HR mass spectrometry (see the Supporting Information). The thermal gravimetric analyses displayed that compounds OPyN, TPyN, TPyC, and TPyO are stable up to 387 °C, 424 °C, 354 °C, and 420 °C, respectively (5% weight loss, Figure S1). Apparently, the all-carbon six-membered ring in TBH was replaced with five-membered rings in OPyN, TPyN, TPyC, and TPyO. The effects of atom type and position on their corresponding optoelectronic properties were investigated in a comparative manner and discussed in the following part. 2.2. Single Crystal. To determine the position of heteroatom and spacial arrangement, single crystals were grown by slow evaporation of dichloromethane/methanol
solution at room temperature. Fortunately, single crystals of compounds OPyN and TPyC, suitable for X-ray crystallography analysis, were obtained. The crystal structures and threedimensional packing models are depicted in Figure 1. Molecule OPyN (CCDC: 1481329) belonged to a monoclinic space group P21/c with unit cell parameters of a = 11.3862(9) Å, b = 15.7448 (12) Å, c = 20.8111 (18) Å, α = γ = 90°, and β = 90.4170(10)o. While, the space group of TPyC (CCDC: 1481330) presented an orthorhombic Pbca group with unit cell parameters of a = 12.2533 (11) Å, b = 21.9128 (19) Å, c = 27.684 (2) Å, and α = β = γ = 90°. Note that the obtained molecules OPyN and TPyC exhibited twisted configurations, and the angles between pyrene unit and the adjacent naphthalene moiety are 35.46° and 27.51°, respectively, which are larger than that of TBH (27.34°).42 The twisted structure might suppress the π−π stacking interaction in the solid state, as confirmed by their packing models (Figure 1b,d). 2.3. Optical Properties. The UV−vis absorption spectra were examined in dichloromethane and thin film as shown in Figure 2 and Figure S2 and Table S1. Compound OPyN showed the absorption bands at 435 and 352 nm with a shoulder peak at 411 nm. In comparison, its isomer TPyN 18999
DOI: 10.1021/acsami.6b07304 ACS Appl. Mater. Interfaces 2016, 8, 18998−19003
Research Article
ACS Applied Materials & Interfaces Scheme 3. Synthetic Route to TPyC and TPyO
glass slices presented broad structureless and slightly red-shifted peaks, in comparison with those in dichloromethane. The corresponding emission spectra also exhibited obvious bathochromic shift (Figure S2). 2.4. Electrochemical Behaviors. The electrochemical behaviors of the formed molecules were performed to examine the electronic structure by cyclic voltammetry in CH2Cl2/0.1 M NBu4PF6 at a Pt electrode (Figure 3). Ferrocene was used as an internal standard. TPyC showed the first reversible oxidation waves at 0.65 V, whereas the oxidation peaks of TPyO, OPyN, TPyN were observed at more negative potentials of 0.64 V, 0.54 V, and 0.44 V, respectively. The above-mentioned trend suggested that molecule TPyN containing nitrogen atom had greatest electron-donating ability. On the basis of the first oxidation potentials, the highest occupied molecular orbitals (HOMO) energy levels are observed to be −5.45 eV for TPyC, −5.44 eV for TPyO, −5.34 eV for OPyN, and −5.24 eV for TPyN, respectively.43 2.5. Electroluminescent Property. Thanks for high fluorescence quantum yield, the twisted and rigid structure,
presented the impressive red shift with the lowest energy peak centered at 460 nm, which might be attributed to the linear conjugation in TPyN. When nitrogen atoms were replaced with carbon and oxygen atoms, the as-formed molecules TPyC and TPyO featured the absorption peaks at 433/394/345 nm and 437/404/385/355/339 nm, respectively. Fluorescence spectra were also exhibited in Figure 2. Compounds OPyN, TPyC, and TPyO displayed high blue fluorescence in dichoromethane solution with maxima peaks at 455/475 nm, 446/472 nm, 456/ 479 nm, respectively. However, the linear molecule TPyN showed the bathochromic shift to 481/510 nm, which fell into the green-emission region. The quantum yields of compounds OPyN, TPyN, TPyC, and TPyO were determined to be 0.29, 0.32, 0.35, and 0.38, respectively, using 9,10-diphenylanthracene as a standard.27 Apparently, the absorption and emission spectra of these four compounds displayed significant blue-shift compared to those of the counterpart TBH, suggesting the inserting five-membered ring into skeleton of twistacene could affect the physical properties to a great extent. The absorption spectra of compounds OPyN-TPyO thin films dispersed on 19000
DOI: 10.1021/acsami.6b07304 ACS Appl. Mater. Interfaces 2016, 8, 18998−19003
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ACS Applied Materials & Interfaces
Figure 3. Cyclic voltammograms of compounds OPyN, TPyN, TPyC, and TPyO in 0.1 M n-TBAPF6/CH2Cl2 at a scan rate of 0.05 V s−1.
di(naphthalen-1-yl)-N4,N4′-diphenylbiphenyl-4,4′-diamine, CBP is 4,4′-di(9H-carbazol-9-yl)biphenyl, and BCP is 2,9dimethyl-4,7-diphenyl-1,10-phenanthroline in device B. The doping concentrations are 5%, 10% for OPyN in m-CBP and 3%, 5% for TPyN in CBP as shown in Figure 4. The turn Figure 1. X-ray single crystal structures of compounds OPyN (a), TPyC (c), and their corresponding packing patterns (b), (d).
Figure 4. Current density−voltage-luminance characteristics of OPyN (a) and TPyN (b).
on voltages with 1.0 cd/m2 brightness are 6.6 V (5% dopant) and 7.3 V (10% dopant) for OPyN and 11.5 V (3% dopant) and 11.8 V (5% dopant) for TPyN, respectively. Devices A and B can approach the maximum brightness of 1295 cd/m2 at 13 V and 416 cd/m2 at 25 V, respectively. These data suggested that device A presented higher performance than that of device B, and the increase of dopant concentration had a negligible effect on the luminescence. Device B displayed the electroluminescent spectra at 485/511 nm, correlating well with the fluorescence spectra in dichloromethane (481/510 nm) and thin film (487/514 nm). However, device A exhibited the spectra centered at 452/471 nm and additional peak at 585 nm, which might resulted from the oxidation of the terminal fivemembered heterocycle pyrrole in the presence of current. Apparently, the device performance was moderate and the optimization conditions are needed.
Figure 2. UV−vis absorption and fluorescence spectra of compounds OPyN, TPyN (a) and TPyC, TPyO (b). Insets show the fluorescence picture excited at 365 nm.
the electroluminescence devices based on compounds OPyN and TPyN as active candidates were fabricated. The devices were prepared with the configurations of ITO/TAPC(20 nm)/ m-CBP:OPyN(30 nm)/TPBi(50 nm)/Liq(2 nm)/Al for device A, ITO/NPB(70 nm)/CBP:TPyN(20 nm)/ BCP (20 nm)/Alq3(30 nm)/Liq(2 nm) for device B, where TAPC is 1,1bis[4-[N,N-di(p-tolyl)amino]phenyl]cyclohexane, m-CBP is 3,3-Bis(carbazol-9-yl)biphenyl, TPBi is 1,3,5-tris(1-phenyl-1Hbenzimidazol-2-yl)benzene in device A and NPB is N4,N4′19001
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(10) Schuler, B.; Collazos, S.; Gross, L.; Meyer, G.; Pérez, D.; Guitián, E.; Peñ a, D. From Perylene to a 22-Ring Aromatic Hydrocarbon in One-Pot. Angew. Chem., Int. Ed. 2014, 53, 9004− 9006. (11) Clar, E. Polycyclic Hydrocarbons; Academic Press: London, 1964. (12) Chun, D.; Cheng, Y.; Wudl, F. The Most Stable and Fully Characterized Functionalized Heptacene. Angew. Chem., Int. Ed. 2008, 47, 8380−8385. (13) Kaur, I.; Jazdzyk, M.; Stein, N. N.; Prusevich, P.; Miller, G. P. Design, Synthesis, and Characterization of a Persistent Nonacene Derivative. J. Am. Chem. Soc. 2010, 132, 1261−1263. (14) Kaur, I.; Jia, W.; Kopreski, R. P.; Selvarasah, S.; Dokmeci, M. R.; Pramanik, C.; McGruer, N. E.; Miller, G. P. Substituent Effects in Pentacenes: Gaining Control over HOMO−LUMO Gaps and Photooxidative Resistances. J. Am. Chem. Soc. 2008, 130, 16274− 16286. (15) Gao, X.; Hodgson, J. L.; Jiang, D.; Zhang, S. B.; Nagase, S.; Miller, G. P.; Chen, Z. Open-Shell Singlet Character of Stable Derivatives of Nonacene, Hexacene and Teranthene. Org. Lett. 2011, 13, 3316−3319. (16) Purushothaman, B.; Bruzek, M.; Parkin, S. R.; Miller, A. F.; Anthony, J. E. Synthesis and Structural Characterization of Crystalline Nonacenes. Angew. Chem., Int. Ed. 2011, 50, 7013−7017. (17) Miao, Q.; Chi, X.; Xiao, S.; Zeis, R.; Lefenfeld, M.; Siegrist, T.; Steigerwald, M. L.; Nuckolls, C. Organization of Acenes with a Cruciform Assembly Motif. J. Am. Chem. Soc. 2006, 128, 1340−1345. (18) Bruzek, M. J.; Anthony, J. E. Synthesis and Optical Properties of Dioxolane-Functionalized Hexacenes and Heptacenes. Org. Lett. 2014, 16, 3608−3610. (19) Jiang, W.; Li, Y.; Wang, Z. Heteroarenes as High Performance Organic Semiconductors. Chem. Soc. Rev. 2013, 42, 6113−6127. (20) Bunz, U. H. F.; Engelhart, J. U.; Lindner, B. D.; Schaffroth, M. Large N-Heteroacenes: New Tricks for Very Old Dogs? Angew. Chem., Int. Ed. 2013, 52, 3810−3821. (21) Tverskoy, O.; Rominger, F.; Peters, A.; Himmel, H. J.; Bunz, U. H. F. An Efficient Synthesis of Tetraazapentacenes. Angew. Chem., Int. Ed. 2011, 50, 3557−3560. (22) Engelhart, J. U.; Lindner, B. D.; Schaffroth, M.; Schrempp, D.; Tverskoy, O.; Bunz, U. H. F. Substituted Tetraaza- and Hexaazahexacenes and their N,N′-Dihydro Derivatives: Syntheses, Properties, and Structures. Chem. - Eur. J. 2015, 21, 8121−8129. (23) Mateo-Alonso, A. Pyrene-fused Pyrazaacenes: from Small Molecules to Nanoribbons. Chem. Soc. Rev. 2014, 43, 6311−6324. (24) Mateo-Alonso, A.; Kulisic, N.; Valenti, G.; Marcaccio, M.; Paolucci, F.; Prato, M. Facile Synthesis of Highly Stable Tetraazaheptacene and Tetraazaoctacene Dyes. Chem. - Asian J. 2010, 5, 482−485. (25) More, S.; Bhosale, R.; Mateo-Alonso, A. Low-LUMO PyreneFused Azaacenes. Chem. - Eur. J. 2014, 20, 10626−10631. (26) Ren, T.; Xiao, J.; Wang, W.; Xu, W.; Wang, S.; Zhang, X.; Chen, H.; Zhao, J.; Jiang, L. Synthesis, Crystal Structures, Optical Properties, and Photocurrent Response of Heteroacene Derivatives. Chem. - Asian J. 2014, 9, 1943−1949. (27) Wang, S.; Lv, B.; Cui, Q.; Ma, X.; Ba, X.; Xiao, J. Synthesis, Photophysics, and Self-Assembly of Furan-Embedded Heteroarenes. Chem. - Eur. J. 2015, 21, 14791−14796. (28) Xiao, J.; Tang, B.; Wong, J. I.; Liu, Y.; Wei, F.; Tan, K.; Teng, X.; Wu, Y.; Huang, L.; Kloc, C.; Boey, F.; Ma, J.; Zhang, H.; Yang, H.; Zhang, Q. Synthesis, Characterization, Self-assembly, and Physical Properties of 11-Methylbenzo[d]pyreno[4,5-b]furan. Org. Lett. 2011, 13, 3004−3007. (29) Li, Y.; Liu, T.; Liu, H.; Tian, M.; Li, Y. Self-assembly of Intramolecular Charge-transfer Compounds into Functional Molecular Systems. Acc. Chem. Res. 2014, 47, 1186−1198. (30) Zhou, C.; Li, Y.; Zhao, Y.; Zhang, J.; Yang, W.; Li, Y. Org. Lett. 2011, 13, 292−295. (31) Pascal, R. A., Jr Twisted Acenes. Chem. Rev. 2006, 106, 4809− 4819.
3. CONCLUSIONS In summary, we have designed and synthesized four novel fivemembered heterocycle-inserted twistacene derivatives, highlighting the influence of the heterocycle on their optoelectronic properties and thermal behaviors. Compounds OPyN and TPyN were used as dopants in multilayered OLEDs that exhibited appealing electroluminescent performance. Further studies exploring the functionality of the large symmetrical heterotwistacenes are on the way in our lab.
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.6b07304. The experimental procedures and additional spectra (PDF) Structural characterization data (CIF) Structural characterization data (CIF)
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AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected] (J.X.). *E-mail:
[email protected] (J.Z.). Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (21102031 and 21442010), the Natural Science Foundation of Hebei Province for Distinguished Young Scholar (Cultivation Project, B2015201183), the Natural Science Foundation of Hebei Province (B2014201007), and the Natural Science Foundation of Hebei University (2015JQY02).
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REFERENCES
(1) Bendikov, M.; Wudl, F.; Perepichka, D. F. Tetrathiafulvalenes, Oligoacenenes, and Their Buckminsterfullerene Derivatives: The Brick and Mortar of Organic Electronics. Chem. Rev. 2004, 104, 4891−4946. (2) Markiewicz, J. T.; Wudl, F. Perylene, Oligorylenes, and AzaAnalogs. ACS Appl. Mater. Interfaces 2015, 7, 28063−28085. (3) Pho, T. V.; Yuen, J. D.; Kurzman, J. A.; Smith, B. G.; Miao, M.; Walker, W. T.; Seshadri, R.; Wudl, F. N-Alkyldinaphthocarbazoles, Azaheptacenes, for Solution-Processed Organic Field-Effect Transistors. J. Am. Chem. Soc. 2012, 134, 18185−18188. (4) Brunetti, F. G.; Varotto, A.; Batara, N. A.; Wudl, F. Deconvoluted Fullerene” Derivatives: Synthesis and Characterization. Chem. - Eur. J. 2011, 17, 8604−8608. (5) Ball, M.; Zhong, Y.; Wu, Y.; Schenck, C.; Ng, F.; Steigerwald, M.; Xiao, S.; Nuckolls, C. Contorted Polycyclic Aromatics. Acc. Chem. Res. 2015, 48, 267−276. (6) Busby, E.; Berkelbach, T. C.; Kumar, B.; Chernikov, A.; Zhong, Y.; Hlaing, H.; Zhu, X. Y.; Heinz, T. F.; Hybertsen, M. S.; Sfeir, M. S.; Reichman, D. R.; Nuckolls, C.; Yaffe, O. Multiphonon Relaxation Slows Singlet Fission in Crystalline Hexacene. J. Am. Chem. Soc. 2014, 136, 10654−10660. (7) Anthony, J. E. Functionalized Acenes and Heteroacenes for Organic Electronics. Chem. Rev. 2006, 106, 5028−5048. (8) Anthony, J. E.; Facchetti, A.; Heeney, M.; Marder, S. R.; Zhan, X. n-Type Organic Semiconductors in Organic Electronics. Adv. Mater. 2010, 22, 3876−3892. (9) Pérez, D.; Peña, D.; Guitián, E. Aryne Cycloaddition Reactions in the Synthesis of Large Polycyclic Aromatic Compounds. Eur. J. Org. Chem. 2013, 2013, 5981−6013. 19002
DOI: 10.1021/acsami.6b07304 ACS Appl. Mater. Interfaces 2016, 8, 18998−19003
Research Article
ACS Applied Materials & Interfaces (32) Duong, H. M.; Bendikov, M.; Steiger, D.; Zhang, Q.; Sonmez, G.; Yamada, J.; Wudl, F. Efficient Synthesis of a Novel, Twisted and Stable, Electroluminescent “Twistacene. Org. Lett. 2003, 5, 4433− 4436. (33) Zhang, Q.; Divayana, Y.; Xiao, J.; Wang, Z.; Tiekink, E. R. T.; Doung, H. M.; Zhang, H.; Boey, F.; Sun, X.; Wudl, F. Synthesis, Characterization, and Bipolar Transporting Behavior of a New Twisted Polycyclic Aromatic Hydrocarbon: 1′4′-Diphenyl-naphtho-(2′.3′:1.2)pyrene-6′-nitro-7′-methyl Carboxylate. Chem. - Eur. J. 2010, 16, 7422− 7426. (34) Li, J.; Zhang, Q. Mono- and Oligocyclic Aromatic Ynes and Diynes as Building Blocks to Approach Larger Acenes, Heteroacenes, and Twistacenes. Synlett 2013, 24, 686−696. (35) Xiao, J.; Duong, H. M.; Liu, Y.; Shi, W.; Ji, L.; Li, G.; Li, S.; Liu, X.; Ma, J.; Wudl, F.; Zhang, Q. Synthesis and Structure Characterization of a Stable Nonatwistacene. Angew. Chem., Int. Ed. 2012, 51, 6094−6098. (36) Li, J.; Zhao, Y.; Lu, J.; Li, G.; Zhang, J.; Zhao, Y.; Sun, X.; Zhang, Q. Double [4 + 2] Cycloaddition Reaction to Approach a Large Acene with Even-number linearly Fused Benzene Rings: 6,9,16,19-Tetraphenyl-1.20,4.5,10.11,14.15-tetrabenzooctatwistacene. J. Org. Chem. 2015, 80, 109−113. (37) Li, Y.; Jia, Z.; Xiao, S.; Liu, H.; Li, Y. A Method for Controlling the Synthesis of Stable Twisted Two-dimensional Conjugated Molecules. Nat. Commun. 2016, 7, 11637. (38) Xiao, J.; Liu, Z.; Zhang, X.; Wu, W.; Ren, T.; Lv, B.; Jiang, L.; Wang, X.; Chen, H.; Su, W.; Zhao, J. Substituent Effects in Twisted Dibenzotetracene Derivatives: Blue Emitting Materials for Organic Light-Emitting Diodes. Dyes Pigm. 2015, 112, 176−182. (39) Xiao, J.; Malliakas, C. D.; Liu, Y.; Zhou, F.; Li, G.; Su, H.; Kanatzidis, M. G.; Wudl, F.; Zhang, Q. Clean Reaction” Strategy to Approach a Stable, Green Heptatwistacene Containing a Single Terminal Pyrene Unit. Chem. - Asian J. 2012, 7, 672−675. (40) Liu, Z.; Xiao, J.; Fu, Q.; Feng, H.; Zhang, X.; Ren, T.; Wang, S.; Ma, D.; Wang, X.; Chen, H. Synthesis and Physical Properties of the Conjugated Dendrons Bearing Twisted Acenes Used in Solution Processing of Organic Light-Emitting Diodes. ACS Appl. Mater. Interfaces 2013, 5, 11136−11141. (41) Lv, B.; Shen, X.; Xiao, J.; Duan, J.; Wang, X.; Yi, Y. Synthesis, Single Crystal, and Physical Properties of Asymmetrical Thiophene/ Selenophene-Fused Twistacenes. Chem. - Asian J. 2015, 10, 2677− 2682. (42) Xiao, J.; Liu, S.; Liu, Y.; Ji, L.; Liu, X.; Zhang, H.; Sun, X.; Zhang, Q. Synthesis, Structure, and Physical Properties of 5,7,14,16Tetraphenyl-8:9,12:13-bisbenzo-hexatwistacene. Chem. - Asian J. 2012, 7, 561−564. (43) Wood, J. D.; Jellison, J. L.; Finke, A. D.; Wang, L.; Plunkett, K. N. Electron Acceptors Based on Functionalizable Cyclopenta[hi]aceanthrylenes and Dicyclopenta[de,mn]tetracenes. J. Am. Chem. Soc. 2012, 134, 15783−15789.
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