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This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.
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DOI: 10.1039/C5CC01668A
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Cite this: DOI: 10.1039/x0xx00000x
Received 00th January 2012, Accepted 00th January 2012
Cyano- and chloro-substituted coronene diimides as solution-processable electron-transporting semiconductors Chenhao Zhang, Ke Shi, Kang Cai, Jiajun Xie, Ting Lei, Qifan Yan, Jie-Yu Wang, Jian Pei* and Dahui Zhao*
DOI: 10.1039/x0xx00000x www.rsc.org/
3,4,9,10-Tetracyano- and tetrachlorocoronene-1,6,7,12-tetracarboxy diimides with low LUMO levels at -3.9 to -4.2 eV are developed. These molecules manifest potent n-type semiconductive capability in solution-processed field-effect transistors, with electron mobility up to 0.16 cm2 V-1 s-1 measured in the air. The device performances of analogous molecules elucidate the importance of side chain structures to the semiconductive properties.
Promoted by the promise of low-cost, large-area flexible electronic devices, solution-processed organic field-effect transistors (OFETs) are extensively studied over the past two decades.1 Compared with hole-transporting (p-type) organic semiconducting materials that handily demonstrate sufficient air stabilities, developing electrontransporting counterparts with high electron mobility still faces the challenge of improving the operational stability under ambient conditions.2 A practical approach effectively alleviating this problem is to create n-type organic semiconductors with sufficiently low LUMO. Hence, chemical designs of pertinent molecules commonly harness π-conjugated systems bearing electron-withdrawing functional groups, such as halogens, cyanide, carbonyl, etc.3 Polycyclic aromatic hydrocarbons (PAHs) are widely studied scaffolds for organic semiconductor applications, by virtue of their optimal chemical stability, tunable frontier orbital energy, and large planar polycyclic framework favourable for aromatic stacking interactions. PAHs functionalized with dicarboximide groups are accordingly appealing n-type semiconductor candidates.4 Among various PAH dicarboximides, naphthalene- and perylenetetracarboxy diimides (NDI & PDI) are most intensively investigated substrates. Their chloro- and cyano-substituted derivatives have demonstrated impressive electron mobility in OFET devices with fairly good airoperating stability.3f,5 As an analogue structure of naphthalene and perylene, coronene has an even larger -framework. However, Beijing National Laboratory for Molecular Sciences, Centre for Soft Matter Science and Engineering, the Key Laboratory of Polymer Chemistry and Physics of the Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China. E-mail: [email protected], [email protected]; Fax: +8610 62751708; Tel: +8610 62753973 † Electronic supplementary information (ESI) available: Syntheses, structure characterizations, and DFT calculations. See DOI: 10.1039/
This journal is © The Royal Society of Chemistry 2012
although electron-sufficient coronene derivatives have repeatedly been investigated as hole-transporting molecules, electron-deficient coronenes are much less explored as electron-transporting semiconductors.6 The reason is at the least partially related to the scarcity of synthetic methods for low-LUMO coronene structures.7 Recently, we developed an effective ICl-mediated annulation procedure and realized the syntheses of coronene-1,6,7,12tetracarboxy diimide (CDI) derivatives starting from PDIs.8 We see that the CDI derivatives produced from such reactions are suitable precursors for preparing CDIs with low-lying LUMO levels upon installing additional electron-pulling functional groups on the coronene skeleton. The resultant molecules with large frameworks are potentially excellent n-type semiconductors. Hence, we now seek suitable synthetic procedures to realize the syntheses of such electron-deficient CDIs and subsequently examine their seminconductive capabilities in OFETs. Specifically, using dichlorobis(trimethylsilyl)-functionalized CDI as the substrate, we successfully obtain tetrachloro- and tetracyano-substituted CDIs, as well as an analogue bearing mixed chloro- and cyano- substituents.8b The electrochemical characterizations confirm that all these newly prepared CDI derivatives possess low LUMOs at -3.9 to -4.2 eV. Moreover, the OFET studies prove that selected molecules are optimal solution-processable n-type semiconducting materials, offering impressive electron mobility under ambient conditions. Nonetheless, the single-crystal structure analysis of the tetracyanosubstituted CDI shows that in the solid state the “swallow-tailed” alkyl side groups positioned at the imide nitrogen atoms confer significant steric hindrance to the face-to-face stacking of the planar CDI skeletons. In combination with the recent study results on the influences of alkyl side chains over the device performance of organic semiconductors,9 we then employ 4-octyltetradecyl groups to replace the original -branched 1-hexylheptyl chains, in order to alleviate the steric hindrance. As a result, optimal electron mobility of 0.16 cm2∙V-1∙s-1 is achieved with such a side-chain modified tetracyano-CDI.
J. Name., 2012, 00, 1-3 | 1
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Journal Name 1a and Fig. S1). Their absorption band shapes are similar to those of previously reported CDI derivatives. The most intense peaks are observed around 350 nm, and a set of additional bands manifesting medium intensities emerge between 370 to 450 nm, while the S0-S1 transitions are shown at 450-520 nm with even smaller extinction coefficients.6 Compound 1 bearing four chloro- substituents shows the most red-shifted S0-S1 absorption. Corresponding transitions of 2a having four cyano- groups are noticeably blue shifted, while CDI 3 having mixed substituents displays intermediate S0-S1 energy. In the meanwhile, the S0-S1 extinction coefficients are attenuated significantly as the substitutents are switched from chloro- to cyano-, with 2a exhibiting small coefficient values of merely ~103 M-1 cm-1. TD-DFT simulated absorption spectra afforded a consistent trend with the experimental data (Table S2).
Scheme 1. Syntheses of 1, 2a/b and 3.
The synthetic approaches to chloro- and cyano-substituted CDIs 1-3 are shown in Scheme 1, with detailed procedures provided in ESI.† The reaction substrate dichlorobis(trimethylsilyl)-CDI (4a) was obtained according to the literature reported procedures8b and conveniently used as a syn/anti-isomer mixture,8,10 since the regioisomerism automatically disappears in the final products 1 and 2a with more symmetric structures. First, tetrachloro-substituted CDI 1 was successfully prepared from 4a via ipso-desilylation induced by latent [Cl]+-species introduced by t-BuOCl.11 With the stoichiometry of t-BuOCl being carefully controlled, the reaction proceeded smoothly to afford 1 at 75% yield. Through a similar procedure involving electrophilic iodination, facilitated by the reagent ICl, dichlorodiiodo-substituted CDI 5a could be obtained, which was also used as a regio-isomer mixture in the following reactions. With CuCN as a cyanide source, a copper-mediated cyanation was first attempted for synthesizing tetracyano-CDI 2a.3f,5c,12 Even though this reaction was carried out at a relatively high temperature of 120 °C for 24 h, only partial cyanation occurred. Namely, the iodogroups were selectively replaced by cyano, but the chlorine atoms remained intact. Thus, a mixture of anti/syn- isomers of dichlorodicyano-CDI 3 was afforded, at a moderate yield of 46%. In order to promote the reaction at the less reactive sites of chlorine, a palladium-catalyzed cyanation method was then employed.5b,13 Using a powerful Pd catalyst in situ generated from Pd2(dba)3 and 1,1’-bis-(diphenylphosphino)ferrocene (dppf), the desired product tetracyano-CDI 2a was achieved at 63% yield upon reacting 5a with CuCN at 105 °C for 2 days. Subsequently, the structures of CDIs 1, 2a, and 3 were all fully characterized and confirmed by 1H & 13C NMR spectroscopy, mass spectrometry, and elemental analyses (see ESI†). All these molecules showed adequate solubility in common organic solvents including chlorinated hydrocarbons, which greatly facilitated their OFET characterizations via the solution-cast devicefabrication method. The UV-vis absorption and fluorescence spectra of these chloroand cyano-substituted CDIs were collected in CH2Cl2 solutions (Fig.
2 | J. Name., 2012, 00, 1-3
Fig. 1 (a) UV-vis absorption spectra of 1, 2a/b and 3 in CH2Cl2 (inset showing enlarged region of 450-525 nm); (b) cyclic voltammograms recorded in CH2Cl2.
The three CDIs manifest well-resolved vibronic structures in the emission spectra (Fig. S1), all showing very small Stokes shifts of
ChemComm Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: C. Zhang, K. Shi, K. Cai, J. Xie, T. Lei, Q. Yan, J. Wang, J. Pei and D. Zhao, Chem. Commun., 2015, DOI:
This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.
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DOI: 10.1039/C5CC01668A
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Cite this: DOI: 10.1039/x0xx00000x
Received 00th January 2012, Accepted 00th January 2012
Cyano- and chloro-substituted coronene diimides as solution-processable electron-transporting semiconductors Chenhao Zhang, Ke Shi, Kang Cai, Jiajun Xie, Ting Lei, Qifan Yan, Jie-Yu Wang, Jian Pei* and Dahui Zhao*
DOI: 10.1039/x0xx00000x www.rsc.org/
3,4,9,10-Tetracyano- and tetrachlorocoronene-1,6,7,12-tetracarboxy diimides with low LUMO levels at -3.9 to -4.2 eV are developed. These molecules manifest potent n-type semiconductive capability in solution-processed field-effect transistors, with electron mobility up to 0.16 cm2 V-1 s-1 measured in the air. The device performances of analogous molecules elucidate the importance of side chain structures to the semiconductive properties.
Promoted by the promise of low-cost, large-area flexible electronic devices, solution-processed organic field-effect transistors (OFETs) are extensively studied over the past two decades.1 Compared with hole-transporting (p-type) organic semiconducting materials that handily demonstrate sufficient air stabilities, developing electrontransporting counterparts with high electron mobility still faces the challenge of improving the operational stability under ambient conditions.2 A practical approach effectively alleviating this problem is to create n-type organic semiconductors with sufficiently low LUMO. Hence, chemical designs of pertinent molecules commonly harness π-conjugated systems bearing electron-withdrawing functional groups, such as halogens, cyanide, carbonyl, etc.3 Polycyclic aromatic hydrocarbons (PAHs) are widely studied scaffolds for organic semiconductor applications, by virtue of their optimal chemical stability, tunable frontier orbital energy, and large planar polycyclic framework favourable for aromatic stacking interactions. PAHs functionalized with dicarboximide groups are accordingly appealing n-type semiconductor candidates.4 Among various PAH dicarboximides, naphthalene- and perylenetetracarboxy diimides (NDI & PDI) are most intensively investigated substrates. Their chloro- and cyano-substituted derivatives have demonstrated impressive electron mobility in OFET devices with fairly good airoperating stability.3f,5 As an analogue structure of naphthalene and perylene, coronene has an even larger -framework. However, Beijing National Laboratory for Molecular Sciences, Centre for Soft Matter Science and Engineering, the Key Laboratory of Polymer Chemistry and Physics of the Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China. E-mail: [email protected], [email protected]; Fax: +8610 62751708; Tel: +8610 62753973 † Electronic supplementary information (ESI) available: Syntheses, structure characterizations, and DFT calculations. See DOI: 10.1039/
This journal is © The Royal Society of Chemistry 2012
although electron-sufficient coronene derivatives have repeatedly been investigated as hole-transporting molecules, electron-deficient coronenes are much less explored as electron-transporting semiconductors.6 The reason is at the least partially related to the scarcity of synthetic methods for low-LUMO coronene structures.7 Recently, we developed an effective ICl-mediated annulation procedure and realized the syntheses of coronene-1,6,7,12tetracarboxy diimide (CDI) derivatives starting from PDIs.8 We see that the CDI derivatives produced from such reactions are suitable precursors for preparing CDIs with low-lying LUMO levels upon installing additional electron-pulling functional groups on the coronene skeleton. The resultant molecules with large frameworks are potentially excellent n-type semiconductors. Hence, we now seek suitable synthetic procedures to realize the syntheses of such electron-deficient CDIs and subsequently examine their seminconductive capabilities in OFETs. Specifically, using dichlorobis(trimethylsilyl)-functionalized CDI as the substrate, we successfully obtain tetrachloro- and tetracyano-substituted CDIs, as well as an analogue bearing mixed chloro- and cyano- substituents.8b The electrochemical characterizations confirm that all these newly prepared CDI derivatives possess low LUMOs at -3.9 to -4.2 eV. Moreover, the OFET studies prove that selected molecules are optimal solution-processable n-type semiconducting materials, offering impressive electron mobility under ambient conditions. Nonetheless, the single-crystal structure analysis of the tetracyanosubstituted CDI shows that in the solid state the “swallow-tailed” alkyl side groups positioned at the imide nitrogen atoms confer significant steric hindrance to the face-to-face stacking of the planar CDI skeletons. In combination with the recent study results on the influences of alkyl side chains over the device performance of organic semiconductors,9 we then employ 4-octyltetradecyl groups to replace the original -branched 1-hexylheptyl chains, in order to alleviate the steric hindrance. As a result, optimal electron mobility of 0.16 cm2∙V-1∙s-1 is achieved with such a side-chain modified tetracyano-CDI.
J. Name., 2012, 00, 1-3 | 1
ChemComm Accepted Manuscript
Published on 17 March 2015. Downloaded by University of California - San Francisco on 19/03/2015 01:58:32.
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Journal Name 1a and Fig. S1). Their absorption band shapes are similar to those of previously reported CDI derivatives. The most intense peaks are observed around 350 nm, and a set of additional bands manifesting medium intensities emerge between 370 to 450 nm, while the S0-S1 transitions are shown at 450-520 nm with even smaller extinction coefficients.6 Compound 1 bearing four chloro- substituents shows the most red-shifted S0-S1 absorption. Corresponding transitions of 2a having four cyano- groups are noticeably blue shifted, while CDI 3 having mixed substituents displays intermediate S0-S1 energy. In the meanwhile, the S0-S1 extinction coefficients are attenuated significantly as the substitutents are switched from chloro- to cyano-, with 2a exhibiting small coefficient values of merely ~103 M-1 cm-1. TD-DFT simulated absorption spectra afforded a consistent trend with the experimental data (Table S2).
Scheme 1. Syntheses of 1, 2a/b and 3.
The synthetic approaches to chloro- and cyano-substituted CDIs 1-3 are shown in Scheme 1, with detailed procedures provided in ESI.† The reaction substrate dichlorobis(trimethylsilyl)-CDI (4a) was obtained according to the literature reported procedures8b and conveniently used as a syn/anti-isomer mixture,8,10 since the regioisomerism automatically disappears in the final products 1 and 2a with more symmetric structures. First, tetrachloro-substituted CDI 1 was successfully prepared from 4a via ipso-desilylation induced by latent [Cl]+-species introduced by t-BuOCl.11 With the stoichiometry of t-BuOCl being carefully controlled, the reaction proceeded smoothly to afford 1 at 75% yield. Through a similar procedure involving electrophilic iodination, facilitated by the reagent ICl, dichlorodiiodo-substituted CDI 5a could be obtained, which was also used as a regio-isomer mixture in the following reactions. With CuCN as a cyanide source, a copper-mediated cyanation was first attempted for synthesizing tetracyano-CDI 2a.3f,5c,12 Even though this reaction was carried out at a relatively high temperature of 120 °C for 24 h, only partial cyanation occurred. Namely, the iodogroups were selectively replaced by cyano, but the chlorine atoms remained intact. Thus, a mixture of anti/syn- isomers of dichlorodicyano-CDI 3 was afforded, at a moderate yield of 46%. In order to promote the reaction at the less reactive sites of chlorine, a palladium-catalyzed cyanation method was then employed.5b,13 Using a powerful Pd catalyst in situ generated from Pd2(dba)3 and 1,1’-bis-(diphenylphosphino)ferrocene (dppf), the desired product tetracyano-CDI 2a was achieved at 63% yield upon reacting 5a with CuCN at 105 °C for 2 days. Subsequently, the structures of CDIs 1, 2a, and 3 were all fully characterized and confirmed by 1H & 13C NMR spectroscopy, mass spectrometry, and elemental analyses (see ESI†). All these molecules showed adequate solubility in common organic solvents including chlorinated hydrocarbons, which greatly facilitated their OFET characterizations via the solution-cast devicefabrication method. The UV-vis absorption and fluorescence spectra of these chloroand cyano-substituted CDIs were collected in CH2Cl2 solutions (Fig.
2 | J. Name., 2012, 00, 1-3
Fig. 1 (a) UV-vis absorption spectra of 1, 2a/b and 3 in CH2Cl2 (inset showing enlarged region of 450-525 nm); (b) cyclic voltammograms recorded in CH2Cl2.
The three CDIs manifest well-resolved vibronic structures in the emission spectra (Fig. S1), all showing very small Stokes shifts of
