Qian Miao

Engineering Thin Films of a Tetrabenzoporphyrin toward Efficient Charge-Carrier Transport: Selective Formation of a Brickwork Motif

Co-reporter:Kohtaro TakahashiBowen Shan, Xiaomin Xu, Shuaijun Yang, Tomoyuki Koganezawa, Daiki Kuzuhara, Naoki Aratani, Mitsuharu Suzuki, Qian MiaoHiroko Yamada

ACS Applied Materials & Interfaces March 8, 2017 Volume 9(Issue 9) pp:

Publication Date(Web):February 10, 2017

DOI:10.1021/acsami.6b13988

Tetrabenzoporphyrin (BP) is a p-type organic semiconductor characterized by the large, rigid π-framework, excellent stability, and good photoabsorption capability. These characteristics make BP and its derivatives prominent active-layer components in organic electronic and optoelectronic devices. However, the control of the solid-state arrangement of BP frameworks, especially in solution-processed thin films, has not been intensively explored, and charge-carrier mobilities observed in BP-based materials have stayed relatively low as compared to those in the best organic molecular semiconductors. This work concentrates on engineering the solid-state packing of a BP derivative, 5,15-bis(triisopropylsilyl)ethynyltetrabenzoporphyrin (TIPS-BP), toward achieving efficient charge-carrier transport in its solution-processed thin films. The effort leads to the selective formation of a brickwork packing that has two dimensionally extended π-staking. The maximum field-effect hole mobility in the resulting films reaches 1.1 cm2 V–1 s–1, which is approximately 14 times higher than the record value for pristine free-base BP (0.070 cm2 V–1 s–1). This achievement is enabled mainly through the optimization of three factors; namely, deposition process, cast solvent, and self-assembled monolayer that constitutes the dielectric surface. On the other hand, polarized-light microscopy and grazing-incident wide-angle X-ray diffraction analyses show that there remains some room for improvement in the in-plane homogeneity of molecular alignment, suggesting even higher charge-carrier mobilities can be obtained upon further optimization. These results will provide a useful basis for the polymorph engineering and morphology optimization in solution-processed organic molecular semiconductors.Keywords: brickwork packing; dip coating; organic thin-film transistors; polymorphism; self-assembled monolayers (SAMs); tetrabenzoporphyrin (BP);

A Twisted Nanographene Consisting of 96 Carbon Atoms

Co-reporter:Kwan Yin Cheung;Chi Kit Chan; Zhifeng Liu; Qian Miao

Angewandte Chemie International Edition 2017 Volume 56(Issue 31) pp:9003-9007

Publication Date(Web):2017/07/24

DOI:10.1002/anie.201703754

AbstractHerein we report synthesis, structure and properties of a new type of twisted nanographene, which contains an [8]circulene moiety in a polycyclic framework of 96 sp2 carbon atoms. The key steps in this synthesis are the Diels–Alder reaction of a macrocyclic diyne and the subsequent Scholl reaction forming the [8]circulene moiety. Two incompletely cyclized products were isolated from the Scholl reaction, providing insight into the cyclization of the strained octagon. This nanographene is twisted along two directions with end-to-end twists of 142.4° and 140.2° as revealed by X-ray crystallography, and is flexible at room temperature as found from the computational and experimental studies.

A Twisted Nanographene Consisting of 96 Carbon Atoms

Co-reporter:Kwan Yin Cheung;Chi Kit Chan; Zhifeng Liu; Qian Miao

Angewandte Chemie 2017 Volume 129(Issue 31) pp:9131-9135

Publication Date(Web):2017/07/24

DOI:10.1002/ange.201703754

AbstractHerein we report synthesis, structure and properties of a new type of twisted nanographene, which contains an [8]circulene moiety in a polycyclic framework of 96 sp2 carbon atoms. The key steps in this synthesis are the Diels–Alder reaction of a macrocyclic diyne and the subsequent Scholl reaction forming the [8]circulene moiety. Two incompletely cyclized products were isolated from the Scholl reaction, providing insight into the cyclization of the strained octagon. This nanographene is twisted along two directions with end-to-end twists of 142.4° and 140.2° as revealed by X-ray crystallography, and is flexible at room temperature as found from the computational and experimental studies.

Titelbild: A Twisted Nanographene Consisting of 96 Carbon Atoms (Angew. Chem. 31/2017)

Co-reporter:Kwan Yin Cheung;Chi Kit Chan; Zhifeng Liu; Qian Miao

Angewandte Chemie 2017 Volume 129(Issue 31) pp:9031-9031

Publication Date(Web):2017/07/24

DOI:10.1002/ange.201704990

Dreidimensionale Kohlenstoffstrukturen … mit negativer Krümmung sollen durch Einbindung von Sieben- und Achtecken in ein Graphit-Gitter zugänglich sein, die Synthese dieser Strukturen steht aber noch aus. In ihrer Zuschrift auf S. 9131 ff. beschreiben Q. Miao et al. ein neuartiges, verdrehtes Nanographen, das als Segment negativ gekrümmter Kohlenstoffstrukturen betrachtet werden kann. Das aus 96 sp2-hybridisierten Kohlenstoffatomen bestehende Nanographen ist in zwei Richtungen im Kristall verdreht.

Cover Picture: A Twisted Nanographene Consisting of 96 Carbon Atoms (Angew. Chem. Int. Ed. 31/2017)

Co-reporter:Kwan Yin Cheung;Chi Kit Chan; Zhifeng Liu; Qian Miao

Angewandte Chemie International Edition 2017 Volume 56(Issue 31) pp:8905-8905

Publication Date(Web):2017/07/24

DOI:10.1002/anie.201704990

Three-dimensional nanocarbon structures with negative curvature produced by embedding heptagons or octagons in the graphitic lattice have been proposed, but are yet to be synthesized. In their Communication on page 9003 ff., Q. Miao et al. describe a new type of twisted nanographene, which can be regarded as a segment containing structural information of such negatively curved nanocarbon structures. Consisting of 96 sp2 carbon atoms, this nanographene is twisted along two directions in the crystal.

Molecular design of n-type organic semiconductors for high-performance thin film transistors

Co-reporter:Bowen Shan, Qian Miao

Tetrahedron Letters 2017 Volume 58, Issue 20(Issue 20) pp:

Publication Date(Web):17 May 2017

DOI:10.1016/j.tetlet.2017.04.023

•Insights into two key factors for designing n-type organic semiconductors.•A survey of high-mobility n-type organic semiconductors.•Recent progress of n-channel organic thin film transistors.This digest aims to provide organic chemists with an overview of recent progress on n-type organic semiconductors for application in organic thin film transistors (OTFTs) with an emphasis on molecular design. Herein, we survey n-type organic semiconductors with field effect mobility of 1 cm2/Vs or higher in OTFTs after a brief introduction to the structure and operation of OTFTs and discussion of two key factors (frontier molecular orbitals and molecular packing) of organic semiconductors. On the basis of this survey, we finally reach conclusions on the current status of n-type organic semiconductors for OTFTs and provide an outlook for molecular design.Download high-res image (100KB)Download full-size image

From tetrabenzoheptafulvalene to sp2 carbon nano-rings

Co-reporter:Kwan Yin Cheung;Shuaijun Yang

Organic Chemistry Frontiers 2017 vol. 4(Issue 5) pp:699-703

Publication Date(Web):2017/05/03

DOI:10.1039/C6QO00828C

Herein we report a new strategy to construct nano-rings of sp2 carbon by taking advantage of the “C” shape of syn-tetrabenzoheptafulvalene. This strategy led to the successful synthesis of an sp2 carbon nano-ring containing a tetrabenzoheptafulvalene moiety fused with tetraphenylene. However, attempts to synthesize a more strained nano-ring of sp2 carbon using the same strategy only yielded an oxygen-bridged nano-ring with the step of aromatization being unsuccessful. Both the nano-rings were unambiguously characterized by X-ray crystallography.

Electron Mobility Exceeding 10 cm2 V1 s1 and Band-Like Charge Transport in Solution-Processed n-Channel Organic Thin-Film Transistors

Co-reporter:Xiaomin Xu;Yifan Yao;Bowen Shan;Xiao Gu;Danqing Liu;Jinyu Liu;Jianbin Xu;Ni Zhao;Wenping Hu

Advanced Materials 2016 Volume 28( Issue 26) pp:5276-5283

Publication Date(Web):

DOI:10.1002/adma.201601171

Benzo[4,5]cyclohepta[1,2-b]fluorene: an isomeric motif for pentacene containing linearly fused five-, six- and seven-membered rings

Co-reporter:Xuejin Yang, Xueliang Shi, Naoki Aratani, Théo P. Gonçalves, Kuo-Wei Huang, Hiroko Yamada, Chunyan Chi and Qian Miao

Chemical Science 2016 vol. 7(Issue 9) pp:6176-6181

Publication Date(Web):07 Jun 2016

DOI:10.1039/C6SC01795A

Benzo[4,5]cyclohepta[1,2-b]fluorene (5a), a new π-conjugated polycyclic hydrocarbon containing linearly fused six-, five-, six-, seven- and six-membered rings (C6–C5–C6–C7–C6), was designed and its stable derivatives 5b and 5c were synthesized. With 22 π electrons, 5a is an isomer of pentacene with quinoidal, dipolar ionic and diradical resonance forms. Molecules 5b and 5c were experimentally investigated with cyclic voltammetry, electronic absorption spectroscopy and X-ray crystallographic analysis, and theoretically studied by calculating the NICS value, diradical character and dipole moment. A comparison of 5a–c with pentacene and other pentacene analogues containing linearly fused five- or seven-membered rings was also conducted and discussed. It was found that 5b behaved as a p-type organic semiconductor in solution-processed thin film transistors with a field effect mobility of up to 0.025 cm2 V−1 s−1.

Extension of N-Heteroacenes through a Four-Membered Ring

Co-reporter:Dr. Shuaijun Yang;Bowen Shan;Dr. Xiaomin Xu;Dr. Qian Miao

Chemistry - A European Journal 2016 Volume 22( Issue 19) pp:6637-6642

Publication Date(Web):

DOI:10.1002/chem.201600918

Abstract

The synthesis of novel π-extended N-heteroacenes, which have a large tetraazaacene subunit and a quinoxaline subunit connected through a four-membered ring, is reported. They were studied with experimental and computational methods in comparison to the corresponding tetraazaacenes. As found from the DFT calculation, the four-membered ring is a better linker than a five-membered ring or a C−C single bond to extend N-heteroacenes for a new design of n-type semiconductors in terms of the spatial delocalization and energy level of LUMO as well as the reorganization energy. In solution-processed thin film transistors, the π-extended N-heteroacenes are found to function as n-type semiconductors with field effect mobility of up to 0.02 cm² V⁻¹ s⁻¹ under ambient conditions.

Monolayer Field-Effect Transistors of Nonplanar Organic Semiconductors with Brickwork Arrangement

Co-reporter:Liang Shan;Danqing Liu;Hao Li;Xiaomin Xu;Bowen Shan;Jian-Bin Xu

Advanced Materials 2015 Volume 27( Issue 22) pp:3418-3423

Publication Date(Web):

DOI:10.1002/adma.201500149

Aromatic Saddles Containing Two Heptagons

Co-reporter:Kwan Yin Cheung; Xiaomin Xu

Journal of the American Chemical Society 2015 Volume 137(Issue 11) pp:3910-3914

Publication Date(Web):March 5, 2015

DOI:10.1021/jacs.5b00403

Soluble derivatives of C70H26 (1a,b) and C70H30 (2a,b), two new saddle-shaped polycyclic arenes containing two heptagons, were successfully synthesized from saddle-shaped diketones (3a,b), whose carbonyl groups are the key in the reactions to extend the polycyclic π-framework. As found from the crystal structures, the polycyclic backbone of 1b has a deep saddle shape, while that of 2b is even more distorted because of the existence of two [4]-helicene moieties. On the basis of crystal structures, local aromaticity and nonplanarity of individual rings in the saddle-shaped π-backbone were analyzed, and were found to follow Clar’s rule in general. It was found that 1b and 3b behaved as p-type semiconductors in solution-processed thin film transistors while the amorphous films of 2b appeared insulating.

Synthesis, Molecular Packing, and Thin Film Transistors of Dibenzo[a,m]rubicenes

Co-reporter:Xiao Gu; Xiaomin Xu; Huiyan Li; Zhifeng Liu

Journal of the American Chemical Society 2015 Volume 137(Issue 51) pp:16203-16208

Publication Date(Web):December 11, 2015

DOI:10.1021/jacs.5b10687

We herein report an efficient synthesis of dibenzo[a,m]rubicene, a new member of nonplanar cyclopenta-fused polycyclic aromatic hydrocarbon, and its derivatives. It is found that the conformation and molecular packing of dibenzo[a,m]rubicenes in the solid state can be tuned by the substituting groups, and the silylethynylated derivatives of dibenzo[a,m]rubicenes function as p-type organic semiconductors in solution-processed thin film transistors with field effect mobility of up to 1.0 cm2 V–1 s–1.

Aggregation-induced emission and aggregation-promoted photochromism of bis(diphenylmethylene)dihydroacenes

Co-reporter:Zikai He, Liang Shan, Ju Mei, Hong Wang, Jacky W. Y. Lam, Herman H. Y. Sung, Ian D. Williams, Xiao Gu, Qian Miao and Ben Zhong Tang

Chemical Science 2015 vol. 6(Issue 6) pp:3538-3543

Publication Date(Web):03 Apr 2015

DOI:10.1039/C5SC00900F

Reported herein is a new class of pure polycyclic hydrocarbon molecules, designed through a novel aggregation-induced emission (AIE) strategy, with unexpected photochromic properties. The restriction of intramolecular motion was found as a comprehensive mechanism for the AIE effect. The photochromism mechanism study revealed that the photocyclization reaction of cis-stilbene, the molecular conformation in the single crystal and the tetracene backbone should contribute to the unique photo behavior. In particular, the fast responsive, photo-reversible and thermo-irreversible photochromic effect facilitated in the solid state opens a new field of aggregation-promoted photochromism.

Solution-Processed Ambipolar Organic Thin-Film Transistors by Blending p- and n-Type Semiconductors: Solid Solution versus Microphase Separation

Co-reporter:Xiaomin Xu, Ting Xiao, Xiao Gu, Xuejin Yang, Stephen V. Kershaw, Ni Zhao, Jianbin Xu, and Qian Miao

ACS Applied Materials & Interfaces 2015 Volume 7(Issue 51) pp:28019

Publication Date(Web):April 17, 2015

DOI:10.1021/acsami.5b01172

Here, we report solid solution of p- and n-type organic semiconductors as a new type of p–n blend for solution-processed ambipolar organic thin film transistors (OTFTs). This study compares the solid-solution films of silylethynylated tetraazapentacene 1 (acceptor) and silylethynylated pentacene 2 (donor) with the microphase-separated films of 1 and 3, a heptagon-embedded analogue of 2. It is found that the solid solutions of (1)x(2)1–x function as ambipolar semiconductors, whose hole and electron mobilities are tunable by varying the ratio of 1 and 2 in the solid solution. The OTFTs of (1)0.5(2)0.5 exhibit relatively balanced hole and electron mobilities comparable to the highest values as reported for ambipolar OTFTs of stoichiometric donor–acceptor cocrystals and microphase-separated p-n bulk heterojunctions. The solid solution of (1)0.5(2)0.5 and the microphase-separated blend of 1:3 (0.5:0.5) in OTFTs exhibit different responses to light in terms of absorption and photoeffect of OTFTs because the donor and acceptor are mixed at molecular level with π–π stacking in the solid solution.Keywords: ambipolar; microphase separation; organic semiconductors; organic thin film transistors; solid solution

Heptagons in Aromatics: From Monocyclic to Polycyclic

Co-reporter:Qian Miao

The Chemical Record 2015 Volume 15( Issue 6) pp:1156-1159

Publication Date(Web):

DOI:10.1002/tcr.201510009

Ten Years of N-Heteropentacenes as Semiconductors for Organic Thin-Film Transistors

Co-reporter:Qian Miao

Advanced Materials 2014 Volume 26( Issue 31) pp:5541-5549

Publication Date(Web):

DOI:10.1002/adma.201305497

Introducing N atoms to the pentacene backbone leads to N-heteropentacenes, whose properties can be tuned by changing the number, position and valence state of N atoms in the pentacene backbone. With a rapid development in recent years, N-heteropentacenes and their derivatives have arisen as a new family of organic semiconductors with high performance in organic thin-film transistors (OTFTs). This article reviews the research efforts of developing N-heteropentacenes into organic semiconductors starting from 2003 with emphasis on the work of the author's group since 2009. The structure–property relationship and design rationale are highlighted based on an overview of reported organic semiconductors of N-heteropentacenes.

Self-Assembled Monolayers of Cyclohexyl-Terminated Phosphonic Acids as a General Dielectric Surface for High-Performance Organic Thin-Film Transistors

Co-reporter:Danqing Liu;Zikai He;Yaorong Su;Ying Diao;Stefan C. B. Mannsfeld;Zhenan Bao;Jianbin Xu

Advanced Materials 2014 Volume 26( Issue 42) pp:7190-7196

Publication Date(Web):

DOI:10.1002/adma.201402822

Synthesis, solution-processed thin film transistors and solid solutions of silylethynylated diazatetracenes

Co-reporter:Xiaomin Xu, Bowen Shan, Sergii Kalytchuk, Minghua Xie, Shuaijun Yang, Danqing Liu, Stephen V. Kershaw and Qian Miao

Chemical Communications 2014 vol. 50(Issue 85) pp:12828-12831

Publication Date(Web):11 Jul 2014

DOI:10.1039/C4CC04627G

Silylethynylated diazatetracenes were synthesized in a more efficient way and applied as n-type semiconductors in solution-processed thin film transistors with an electron mobility of 0.65 cm2 V−1 s−1. Co-crystallization of these diazatetracenes with silylethynylated tetracene resulted in solid solutions, which exhibited interesting electrical and optical properties.

Ternary blend bulk heterojunction photovoltaic cells with an ambipolar small molecule as the cascade material

Co-reporter:Lei Ye, Hai Xia, Yubin Xiao, Jianbin Xu and Qian Miao

RSC Advances 2014 vol. 4(Issue 3) pp:1087-1092

Publication Date(Web):31 Oct 2013

DOI:10.1039/C3RA46105J

Here we demonstrate that the power conversion efficiency of a P3HT:PC61BM bulk heterojunction solar cell can be improved from 3.4% to 4.3% by adding 10% of a cyclopent[hi]aceanthrylene derivative (CPA), which is an ambipolar small-molecule semiconductor, to form a ternary blend BHJ solar cell. This enhanced power conversion efficiency arises from improvement of both short-circuit current and open-circuit voltage because the addition of CPA not only provides absorption complementary to that of P3HT, but also leads to longer charge carrier lifetime in the bulk heterojunction.

Heptagon-Embedded Pentacene: Synthesis, Structures, and Thin-Film Transistors of Dibenzo[d,d]benzo[1,2-a:4,5-a]dicycloheptenes

Co-reporter:Xuejin Yang;Danqing Liu; Qian Miao

Angewandte Chemie International Edition 2014 Volume 53( Issue 26) pp:6786-6790

Publication Date(Web):

DOI:10.1002/anie.201403509

Abstract

This study presents a new class of conjugated polycyclic molecules that contain seven-membered rings, detailing their synthesis, crystal structures and semiconductor properties. These molecules have a nearly flat C₆-C₇-C₆-C₇-C₆ polycyclic framework with a p-quinodimethane core. With field-effect mobilities of up to 0.76 cm² V⁻¹ s⁻¹ as measured from solution-processed thin-film transistors, these molecules are alternatives to the well-studied pentacene analogues for applications in organic electronic devices.

Heptagon-Embedded Pentacene: Synthesis, Structures, and Thin-Film Transistors of Dibenzo[d,d]benzo[1,2-a:4,5-a]dicycloheptenes

Co-reporter:Xuejin Yang;Danqing Liu; Qian Miao

Angewandte Chemie 2014 Volume 126( Issue 26) pp:6904-6908

Publication Date(Web):

DOI:10.1002/ange.201403509

Abstract

This study presents a new class of conjugated polycyclic molecules that contain seven-membered rings, detailing their synthesis, crystal structures and semiconductor properties. These molecules have a nearly flat C₆-C₇-C₆-C₇-C₆ polycyclic framework with a p-quinodimethane core. With field-effect mobilities of up to 0.76 cm² V⁻¹ s⁻¹ as measured from solution-processed thin-film transistors, these molecules are alternatives to the well-studied pentacene analogues for applications in organic electronic devices.

Conjugated macrocycles of phenanthrene: a new segment of [6,6]-carbon nanotube and solution-processed organic semiconductors

Co-reporter:Zikai He, Xiaomin Xu, Xing Zheng, Tian Ming and Qian Miao

Chemical Science 2013 vol. 4(Issue 12) pp:4525-4531

Publication Date(Web):23 Sep 2013

DOI:10.1039/C3SC52077C

Conjugated macrocycles can be equipped with interesting functions by having polycyclic aromatic hydrocarbon (PAH) building blocks that are larger than benzene. The building block explored herein is phenanthrene, which is connected with varied linkers leading to new trimeric conjugated macrocycles (1–4). The coronal macrocycle 1, whose π-backbone is a new segment of [6,6]-carbon nanotube, is synthesized from the flat macrocycle 2 by Lewis acid-catalyzed [4 + 2] benzannulation. This suggests a new strategy to synthesize π-extended nanorings from conjugated macrocycles that are more easily accessed. As found from a comparative study with focus on self-assembly and organic semiconductor behavior, flat or nearly flat conjugated macrocycles 2–4 function as p-type organic semiconductors in solution-processed thin film transistors. Their field effect mobility as measured from as-cast films is dependent on their ability of self-aggregation in solution.

Revisiting zethrene: synthesis, reactivity and semiconductor properties

Co-reporter:Liang Shan, Zhixiong Liang, Xiaomin Xu, Qin Tang and Qian Miao

Chemical Science 2013 vol. 4(Issue 8) pp:3294-3297

Publication Date(Web):07 Jun 2013

DOI:10.1039/C3SC51158H

Zethrene, a unique polycyclic aromatic hydrocarbon with formally fixed C–C double bonds, is predicted to have interesting properties and potential applications as an optical and electronic material. Here we report a novel synthesis of zethrene with improved yield, which presumably involves dinaphtho[10]-annulene as an unstable intermediate. With this convenient access to zethrene, we used zethrene as a p-type semiconductor in thin film transistors for the first time. It is found that Diels–Alder addition to the bay region of zethrene leads to new derivatives of benzo[pqr]naphtho[8,1,2-bcd]perylene, which behave as n-type organic semiconductors.

Ambipolar organic semiconductors from electron-accepting cyclopenta-fused anthracene

Co-reporter:Hai Xia, Danqing Liu, Xiaomin Xu and Qian Miao

Chemical Communications 2013 vol. 49(Issue 39) pp:4301-4303

Publication Date(Web):02 Aug 2012

DOI:10.1039/C2CC34992B

Reported here are a new group of cyclopent[hi]aceanthrylene derivatives, which have a cyclopentadiene moiety to accept electrons and thus function as ambipolar organic semiconductors in thin film transistors.

Self-Assembled Monolayers of Phosphonic Acids with Enhanced Surface Energy for High-Performance Solution-Processed N-Channel Organic Thin-Film Transistors

Co-reporter:Danqing Liu;Xiaomin Xu;Yaorong Su;Zikai He; Jianbin Xu; Qian Miao

Angewandte Chemie International Edition 2013 Volume 52( Issue 24) pp:6222-6227

Publication Date(Web):

DOI:10.1002/anie.201300353

Self-Assembled Monolayers of Phosphonic Acids with Enhanced Surface Energy for High-Performance Solution-Processed N-Channel Organic Thin-Film Transistors

Co-reporter:Danqing Liu;Xiaomin Xu;Yaorong Su;Zikai He; Jianbin Xu; Qian Miao

Angewandte Chemie 2013 Volume 125( Issue 24) pp:6342-6347

Publication Date(Web):

DOI:10.1002/ange.201300353

Curved Polycyclic Aromatic Molecules That Are π-Isoelectronic to Hexabenzocoronene

Co-reporter:Jiye Luo ; Xiaomin Xu ; Renxin Mao

Journal of the American Chemical Society 2012 Volume 134(Issue 33) pp:13796-13803

Publication Date(Web):July 25, 2012

DOI:10.1021/ja3054354

Reported here are two types of curved π-molecules that are π-isoelectronic to planar hexabenzocoronene (HBC) but are forced out of planarity either by an embedded seven-membered ring or by atom crowding at the fjord region. Embedding a heptagon in HBC leads to a novel saddle-shaped molecule 1, whose π-backbone is slightly less curved than the previously reported [7]circulene in terms of the average Gauss curvature, but surprisingly much more rigid than [7]circulene. Overcrowded fjord regions in novel derivatives of hexabenzoperylene (HBP) 2a,b lead to both chiral twisted and antifolded conformers. The successful synthesis of 1 and 2a,b is related to introducing alkoxyl groups to unprecedented positions of hexaphenylbenzenes. It is found that the red twisted isomer of 2b isomerizes at elevated temperature to the yellow anti-folded conformer. This finding along with the study on the thermodynamics and kinetics of the thermal isomerization has improved the early understandings on the conformation of HBP. In the crystals, 1 lacks π–π interactions between neighboring molecules, while twisted-2a exhibits both face-to-face and edge-to-face π–π interactions. Twisted-2b is found to function as a p-type semiconductor in thin film transistors, but the thin films of 1 appear insulating presumably due to lacking π–π interactions. By exploring three different types of curvatures in 1 and the two isomers of 2b, this study has revealed that the curvature of π-face plays a role in determining the frontier molecular orbital energy levels and π–π interactions and thus needs to be considered when one designs new organic semiconductors.

Induced crystallization of rubrene with diazapentacene as the template

Co-reporter:Danqing Liu, Zhefeng Li, Zikai He, Jianbin Xu and Qian Miao

Journal of Materials Chemistry A 2012 vol. 22(Issue 10) pp:4396-4400

Publication Date(Web):02 Feb 2012

DOI:10.1039/C2JM14941A

The poor crystallinity of rubrene in conventional films is a well-known obstacle limiting practical applications of rubrene in thin film transistors. Here we report a study on using 6,13-diazapentacene (DAP) as a template to induce crystallization of rubrene in thin film transistors. This study demonstrates that DAP is a suitable template molecule with negligible contribution to the conduction channel and leads to polycrystalline thin films of rubrene with field effect mobility as high as 0.68 cm2 V−1 s−1. This induced-crystallization strategy highly depends on a unique octadecylphosphonic acid (ODPA) bilayer-step surface, which is found to play important roles in controlling the growth of both DAP and rubrene.

Hydrogen-Bonded Dihydrotetraazapentacenes

Co-reporter:Zikai He, Danqing Liu, Renxin Mao, Qin Tang, and Qian Miao

Organic Letters 2012 Volume 14(Issue 4) pp:1050-1053

Publication Date(Web):January 31, 2012

DOI:10.1021/ol203404q

Three new members of N-heteropentacenes explored herein have adjacent pyrazine and dihydropyrazine rings at one end of the pentacene backbone. Interesting findings from this study include self-complementary N–H···N H-bonds in the solid state, solvent-dependent UV–vis absorption caused by H-bonding, and new p-type organic semiconductors with field effect mobility up to 0.7 cm2 V–1 s–1.

Highly Electron-Deficient Hexaazapentacenes and Their Dihydro Precursors

Co-reporter:Zikai He, Renxin Mao, Danqing Liu, and Qian Miao

Organic Letters 2012 Volume 14(Issue 16) pp:4190-4193

Publication Date(Web):August 2, 2012

DOI:10.1021/ol301854z

Novel silylethynylated N-heteropentacenes that have three adjacent pyrazine rings at the center of a pentacene backbone are reported. These hexaazapentacenes exhibit a record low energy level of lowest unoccupied molecular orbital (LUMO) for N-heteropentacenes and thus are able to oxidize dihydroanthracene to anthracene. Their synthetic precursors are the corresponding dihydrohexaazapentacenes, which exhibit interesting H-bonding.

Soluble and Stable N-Heteropentacenes with High Field-Effect Mobility

Co-reporter:Zhixiong Liang;Qin Tang;Jianbin Xu

Advanced Materials 2011 Volume 23( Issue 13) pp:1535-1539

Publication Date(Web):

DOI:10.1002/adma.201004325

The Position of Nitrogen in N-Heteropentacenes Matters

Co-reporter:Zhixiong Liang;Qin Tang;Renxin Mao;Danqing Liu;Jianbin Xu

Advanced Materials 2011 Volume 23( Issue 46) pp:5514-5518

Publication Date(Web):

DOI:10.1002/adma.201103759

Vapochromic and semiconducting solids of a bifunctional hydrocarbon

Co-reporter:Hai Xia, Danqing Liu, Kesheng Song and Qian Miao

Chemical Science 2011 vol. 2(Issue 12) pp:2402-2406

Publication Date(Web):15 Sep 2011

DOI:10.1039/C1SC00494H

This study explores a bifunctional hydrocarbon, which has two non-planar dibenzocycloheptatriene moieties linked by three cumulative C–C double bonds. This flexible conjugated molecule can adopt two conformations, namely, syn and anti, in its crystals. Of particular interest is that the molecule’s solids not only function as p-type semiconductors with field effect mobility of 0.02 cm2 V−1 S−1 but also exhibit vapochromic behavior with high selectivity. Upon selectively trapping specific volatile molecules, such as toluene and m-xylene, in the crystal lattice, the guest-free crystals of the syn conformer change to the clathrate crystals of the anti conformer accompanied by a change of color from red to orange. The unique combination of the two useful functions of this molecule can be attributed to its cycloheptatriene and cumulene moieties, both of which have rarely been used in building blocks for organic functional materials.

Switching of non-helical overcrowded tetrabenzoheptafulvalene derivatives

Co-reporter:Jiye Luo, Kesheng Song, Feng long Gu and Qian Miao

Chemical Science 2011 vol. 2(Issue 10) pp:2029-2034

Publication Date(Web):21 Jul 2011

DOI:10.1039/C1SC00340B

This study explores a series of non-helical overcrowded tetrabenzoheptafulvalene derivatives, which are different from the parent tetrabenzoheptafulvalene (1) by avoiding terminal C–C double bonds, detailing their synthesis, characterization and syn/antiisomerization. The most interesting findings from this study are that the syn and anti isomers of three overcrowded tetrabenzoheptafulvalene derivatives (3–5) can be switched by photo- and thermal isomerizations both in very high yields. The predominance of syn isomer in the photoisomerization has been explained with DFT calculations in terms of the arrangement of the excited- and ground-state potential energy surfaces. The less stable syn isomer of an overcrowded tetrabenzoheptafulvalene derivative thermally isomerizes to the corresponding anti isomer through seven-membered ring flipping, and the energy barrier of thermal isomerization is found to be directly related to the rigidity and crowdedness of the seven-membered rings. These findings suggest that overcrowded tetrabenzoheptafulvalene derivatives are promising building blocks for molecular switches and machines. In addition, the new synthesis and unambiguous characterization of hexabenzoheptafulvalene (4) have also led to correction of the previously claimed synthesis of hexabenzooctalene.

Single crystal n-channel field effect transistors from solution-processed silylethynylated tetraazapentacene

Co-reporter:Chengliang Wang, Zhixiong Liang, Yaling Liu, Xiaomu Wang, Ni Zhao, Qian Miao, Wenping Hu and Jianbin Xu

Journal of Materials Chemistry A 2011 vol. 21(Issue 39) pp:15201-15204

Publication Date(Web):01 Sep 2011

DOI:10.1039/C1JM13153B

Single crystals of TIPS-TAP were grown from solution using poor solvents. With gluing silver-films as source and drain electrodes, the crystals exhibited field-effect mobility up to 1.77 cm2 V−1s−1, which is one of the highest values reported for solution-processed n-channel single crystal OFETs.

High hole mobility of 1,2-bis[4′-(diphenylamino)biphenyl-4-yl]-1,2-diphenylethene in field effect transistor

Co-reporter:Zujin Zhao, Zhefeng Li, Jacky W. Y. Lam, Jose-Luis Maldonado, Gabriel Ramos-Ortiz, Yang Liu, Wangzhang Yuan, Jianbin Xu, Qian Miao and Ben Zhong Tang

Chemical Communications 2011 vol. 47(Issue 24) pp:6924-6926

Publication Date(Web):20 May 2011

DOI:10.1039/C1CC12011E

Triphenylamine-functionalized tetraphenylethene shows aggregation-induced emission feature with unity solid-state fluorescence efficiency. Its amorphous film can function in a p-type FET device with field effect mobility up to 2.6 × 10−3 cm2/Vs.

Induced Crystallization of Rubrene in Thin-Film Transistors

Co-reporter:Zhefeng Li;Jun Du;Qin Tang;Feng Wang;Jian-Bin Xu;Jimmy C. Yu

Advanced Materials 2010 Volume 22( Issue 30) pp:3242-3246

Publication Date(Web):

DOI:10.1002/adma.201000786

Induced Crystallization of Rubrene in Thin-Film Transistors (Adv. Mater. 30/2010)

Co-reporter:Zhefeng Li;Jun Du;Qin Tang;Feng Wang;Jian-Bin Xu;Jimmy C. Yu

Advanced Materials 2010 Volume 22( Issue 30) pp:

Publication Date(Web):

DOI:10.1002/adma.201090100

N-Type Organic Semiconductors Based on π-Deficient Pentacenequinones: Synthesis, Electronic Structures, Molecular Packing, and Thin Film Transistors

Co-reporter:Zhixiong Liang, Qin Tang, Jing Liu, Jinhua Li, Feng Yan, and Qian Miao

Chemistry of Materials 2010 Volume 22(Issue 23) pp:6438

Publication Date(Web):November 4, 2010

DOI:10.1021/cm102681p

Quinones are well-known as organic oxidizing reagents in organic synthesis and biological systems, but their ability of accepting electrons was rarely explored in connection with n-type organic semiconductors. Here, we report a comprehensive study on two groups of π-deficient pentacenequinones, fluorinated pentacenequinones and N-heteropentacenequinones, highlighting their electronic structures, molecular packing, and n-channel thin film transistors. It is found that replacing H atoms of pentacenequinone with F atoms or replacing C atoms with N can lower the lowest unoccupied molecular orbital (LUMO) energy level of pentacenequinone to yield n-type organic semiconductors with the field effect mobility up to higher than 0.1 cm2V−1s−1 in thin film transistors. A comparison between the two groups of quinones in terms of their electronic structures and molecular packing has led to interesting findings on the roles of electron-withdrawing moieties in tuning frontier molecular orbitals and π-stacking. Another interesting finding on the molecular packing is the quadruple weak hydrogen bonds, which link the neighboring π-stacks of quinones. This study suggests that π-deficient quinones would be a general design for n-type organic semiconductors.

N-heteroquinones: quadruple weak hydrogen bonds and n-channel transistors

Co-reporter:Qin Tang, Zhixiong Liang, Jing Liu, Jianbin Xu and Qian Miao

Chemical Communications 2010 vol. 46(Issue 17) pp:2977-2979

Publication Date(Web):05 Mar 2010

DOI:10.1039/C001215G

This study demonstrates that the easily synthesized N-heteroquinones, having unusual quadruple weak hydrogen bonds of a DDAA–AADD pattern, can function as n-type organic semiconductors in OTFTs with high electron mobility.

A Meaningful Analogue of Pentacene: Charge Transport, Polymorphs, and Electronic Structures of Dihydrodiazapentacene

Co-reporter:Qin Tang, Dieqing Zhang, Shenglong Wang, Ning Ke, Jianbin Xu, Jimmy C. Yu and Qian Miao

Chemistry of Materials 2009 Volume 21(Issue 7) pp:1400

Publication Date(Web):March 19, 2009

DOI:10.1021/cm9001916

6,13-Dihydro-6,13-diazapentacene (DHDAP) has two nitrogen atoms replacing two carbon atoms of pentacene, the leading organic semiconductor for organic thin film transistors (OTFTs). This report details a comprehensive investigation of DHDAP highlighting the relationship between charge transport, polymorphs, and electronic structures. Three crystalline polymorphs are found from the thin films of DHDAP according to their (001) spacing (layer periodicity). Our surprising finding is that the field effect mobility of DHDAP is extremely sensitive to the polymorphs with the “12.9 Å phase” yielding a mobility of 0.45 cm2 V−1 s−1, which is over 5000 times higher than those of the other two phases. This unusually large effect of the crystalline polymorph on charge transport can be understood in terms of molecular packing using the models developed by de Wijs and Brédas. The comparable field effect mobilities and highly relevant structures of DHDAP and pentacene imply that the common structural features shared by the two molecules may be key factors that benefit the electrical performance while the particular structural features of pentacene should be unimportant to the electrical properties. In this point of view, DHDAP is a meaningful analogue of pentacene allowing better understanding on the structure−property relationship of pentacene. The electronic structure of DHDAP is studied in comparison with that of pentacene using both computational and experimental methods. It is found that DHDAP has a delocalized HOMO with the energy level essentially the same as that of pentacene, although the HOMO−LUMO gap of DHDAP is significantly larger. The environmental stability of DHDAP suggests that a relatively high HOMO energy level does not necessarily lead to environmentally unstable organic semiconductors. These results may lead to better understanding on the structure−property relationship of organic semiconductors.

Benzenoid and Quinonoid Nitrogen-Containing Heteropentacenes

Co-reporter:Qin Tang;Jing Liu;Hoi Shan Chan Dr.

Chemistry - A European Journal 2009 Volume 15( Issue 16) pp:3965-3969

Publication Date(Web):

DOI:10.1002/chem.200900160

Aggregation-induced emission and aggregation-promoted photochromism of bis(diphenylmethylene)dihydroacenes

Co-reporter:Zikai He, Liang Shan, Ju Mei, Hong Wang, Jacky W. Y. Lam, Herman H. Y. Sung, Ian D. Williams, Xiao Gu, Qian Miao and Ben Zhong Tang

Chemical Science (2010-Present) 2015 - vol. 6(Issue 6) pp:NaN3543-3543

Publication Date(Web):2015/04/03

DOI:10.1039/C5SC00900F

Reported herein is a new class of pure polycyclic hydrocarbon molecules, designed through a novel aggregation-induced emission (AIE) strategy, with unexpected photochromic properties. The restriction of intramolecular motion was found as a comprehensive mechanism for the AIE effect. The photochromism mechanism study revealed that the photocyclization reaction of cis-stilbene, the molecular conformation in the single crystal and the tetracene backbone should contribute to the unique photo behavior. In particular, the fast responsive, photo-reversible and thermo-irreversible photochromic effect facilitated in the solid state opens a new field of aggregation-promoted photochromism.

Synthesis, solution-processed thin film transistors and solid solutions of silylethynylated diazatetracenes

Co-reporter:Xiaomin Xu, Bowen Shan, Sergii Kalytchuk, Minghua Xie, Shuaijun Yang, Danqing Liu, Stephen V. Kershaw and Qian Miao

Chemical Communications 2014 - vol. 50(Issue 85) pp:NaN12831-12831

Publication Date(Web):2014/07/11

DOI:10.1039/C4CC04627G

Silylethynylated diazatetracenes were synthesized in a more efficient way and applied as n-type semiconductors in solution-processed thin film transistors with an electron mobility of 0.65 cm2 V−1 s−1. Co-crystallization of these diazatetracenes with silylethynylated tetracene resulted in solid solutions, which exhibited interesting electrical and optical properties.

Ambipolar organic semiconductors from electron-accepting cyclopenta-fused anthracene

Co-reporter:Hai Xia, Danqing Liu, Xiaomin Xu and Qian Miao

Chemical Communications 2013 - vol. 49(Issue 39) pp:NaN4303-4303

Publication Date(Web):2012/08/02

DOI:10.1039/C2CC34992B

Reported here are a new group of cyclopent[hi]aceanthrylene derivatives, which have a cyclopentadiene moiety to accept electrons and thus function as ambipolar organic semiconductors in thin film transistors.

High hole mobility of 1,2-bis[4′-(diphenylamino)biphenyl-4-yl]-1,2-diphenylethene in field effect transistor

Co-reporter:Zujin Zhao, Zhefeng Li, Jacky W. Y. Lam, Jose-Luis Maldonado, Gabriel Ramos-Ortiz, Yang Liu, Wangzhang Yuan, Jianbin Xu, Qian Miao and Ben Zhong Tang

Chemical Communications 2011 - vol. 47(Issue 24) pp:NaN6926-6926

Publication Date(Web):2011/05/20

DOI:10.1039/C1CC12011E

Triphenylamine-functionalized tetraphenylethene shows aggregation-induced emission feature with unity solid-state fluorescence efficiency. Its amorphous film can function in a p-type FET device with field effect mobility up to 2.6 × 10−3 cm2/Vs.

N-heteroquinones: quadruple weak hydrogen bonds and n-channel transistors

Co-reporter:Qin Tang, Zhixiong Liang, Jing Liu, Jianbin Xu and Qian Miao

Chemical Communications 2010 - vol. 46(Issue 17) pp:NaN2979-2979

Publication Date(Web):2010/03/05

DOI:10.1039/C001215G

This study demonstrates that the easily synthesized N-heteroquinones, having unusual quadruple weak hydrogen bonds of a DDAA–AADD pattern, can function as n-type organic semiconductors in OTFTs with high electron mobility.

Revisiting zethrene: synthesis, reactivity and semiconductor properties

Co-reporter:Liang Shan, Zhixiong Liang, Xiaomin Xu, Qin Tang and Qian Miao

Chemical Science (2010-Present) 2013 - vol. 4(Issue 8) pp:NaN3297-3297

Publication Date(Web):2013/06/07

DOI:10.1039/C3SC51158H

Zethrene, a unique polycyclic aromatic hydrocarbon with formally fixed C–C double bonds, is predicted to have interesting properties and potential applications as an optical and electronic material. Here we report a novel synthesis of zethrene with improved yield, which presumably involves dinaphtho[10]-annulene as an unstable intermediate. With this convenient access to zethrene, we used zethrene as a p-type semiconductor in thin film transistors for the first time. It is found that Diels–Alder addition to the bay region of zethrene leads to new derivatives of benzo[pqr]naphtho[8,1,2-bcd]perylene, which behave as n-type organic semiconductors.

Induced crystallization of rubrene with diazapentacene as the template

Co-reporter:Danqing Liu, Zhefeng Li, Zikai He, Jianbin Xu and Qian Miao

Journal of Materials Chemistry A 2012 - vol. 22(Issue 10) pp:NaN4400-4400

Publication Date(Web):2012/02/02

DOI:10.1039/C2JM14941A

The poor crystallinity of rubrene in conventional films is a well-known obstacle limiting practical applications of rubrene in thin film transistors. Here we report a study on using 6,13-diazapentacene (DAP) as a template to induce crystallization of rubrene in thin film transistors. This study demonstrates that DAP is a suitable template molecule with negligible contribution to the conduction channel and leads to polycrystalline thin films of rubrene with field effect mobility as high as 0.68 cm2 V−1 s−1. This induced-crystallization strategy highly depends on a unique octadecylphosphonic acid (ODPA) bilayer-step surface, which is found to play important roles in controlling the growth of both DAP and rubrene.

Single crystal n-channel field effect transistors from solution-processed silylethynylated tetraazapentacene

Co-reporter:Chengliang Wang, Zhixiong Liang, Yaling Liu, Xiaomu Wang, Ni Zhao, Qian Miao, Wenping Hu and Jianbin Xu

Journal of Materials Chemistry A 2011 - vol. 21(Issue 39) pp:NaN15204-15204

Publication Date(Web):2011/09/01

DOI:10.1039/C1JM13153B

Single crystals of TIPS-TAP were grown from solution using poor solvents. With gluing silver-films as source and drain electrodes, the crystals exhibited field-effect mobility up to 1.77 cm2 V−1s−1, which is one of the highest values reported for solution-processed n-channel single crystal OFETs.

Conjugated macrocycles of phenanthrene: a new segment of [6,6]-carbon nanotube and solution-processed organic semiconductors

Co-reporter:Zikai He, Xiaomin Xu, Xing Zheng, Tian Ming and Qian Miao

Chemical Science (2010-Present) 2013 - vol. 4(Issue 12) pp:NaN4531-4531

Publication Date(Web):2013/09/23

DOI:10.1039/C3SC52077C

Conjugated macrocycles can be equipped with interesting functions by having polycyclic aromatic hydrocarbon (PAH) building blocks that are larger than benzene. The building block explored herein is phenanthrene, which is connected with varied linkers leading to new trimeric conjugated macrocycles (1–4). The coronal macrocycle 1, whose π-backbone is a new segment of [6,6]-carbon nanotube, is synthesized from the flat macrocycle 2 by Lewis acid-catalyzed [4 + 2] benzannulation. This suggests a new strategy to synthesize π-extended nanorings from conjugated macrocycles that are more easily accessed. As found from a comparative study with focus on self-assembly and organic semiconductor behavior, flat or nearly flat conjugated macrocycles 2–4 function as p-type organic semiconductors in solution-processed thin film transistors. Their field effect mobility as measured from as-cast films is dependent on their ability of self-aggregation in solution.

Benzo[4,5]cyclohepta[1,2-b]fluorene: an isomeric motif for pentacene containing linearly fused five-, six- and seven-membered rings

Co-reporter:Xuejin Yang, Xueliang Shi, Naoki Aratani, Théo P. Gonçalves, Kuo-Wei Huang, Hiroko Yamada, Chunyan Chi and Qian Miao

Chemical Science (2010-Present) 2016 - vol. 7(Issue 9) pp:NaN6181-6181

Publication Date(Web):2016/06/07

DOI:10.1039/C6SC01795A

Benzo[4,5]cyclohepta[1,2-b]fluorene (5a), a new π-conjugated polycyclic hydrocarbon containing linearly fused six-, five-, six-, seven- and six-membered rings (C6–C5–C6–C7–C6), was designed and its stable derivatives 5b and 5c were synthesized. With 22 π electrons, 5a is an isomer of pentacene with quinoidal, dipolar ionic and diradical resonance forms. Molecules 5b and 5c were experimentally investigated with cyclic voltammetry, electronic absorption spectroscopy and X-ray crystallographic analysis, and theoretically studied by calculating the NICS value, diradical character and dipole moment. A comparison of 5a–c with pentacene and other pentacene analogues containing linearly fused five- or seven-membered rings was also conducted and discussed. It was found that 5b behaved as a p-type organic semiconductor in solution-processed thin film transistors with a field effect mobility of up to 0.025 cm2 V−1 s−1.

From tetrabenzoheptafulvalene to sp2 carbon nano-rings

Co-reporter:Kwan Yin Cheung, Shuaijun Yang and Qian Miao

Inorganic Chemistry Frontiers 2017 - vol. 4(Issue 5) pp:

Publication Date(Web):

DOI:10.1039/C6QO00828C

Vapochromic and semiconducting solids of a bifunctional hydrocarbon

Co-reporter:Hai Xia, Danqing Liu, Kesheng Song and Qian Miao

Chemical Science (2010-Present) 2011 - vol. 2(Issue 12) pp:NaN2406-2406

Publication Date(Web):2011/09/15

DOI:10.1039/C1SC00494H

This study explores a bifunctional hydrocarbon, which has two non-planar dibenzocycloheptatriene moieties linked by three cumulative C–C double bonds. This flexible conjugated molecule can adopt two conformations, namely, syn and anti, in its crystals. Of particular interest is that the molecule’s solids not only function as p-type semiconductors with field effect mobility of 0.02 cm2 V−1 S−1 but also exhibit vapochromic behavior with high selectivity. Upon selectively trapping specific volatile molecules, such as toluene and m-xylene, in the crystal lattice, the guest-free crystals of the syn conformer change to the clathrate crystals of the anti conformer accompanied by a change of color from red to orange. The unique combination of the two useful functions of this molecule can be attributed to its cycloheptatriene and cumulene moieties, both of which have rarely been used in building blocks for organic functional materials.

Switching of non-helical overcrowded tetrabenzoheptafulvalene derivatives

Co-reporter:Jiye Luo, Kesheng Song, Feng long Gu and Qian Miao

Chemical Science (2010-Present) 2011 - vol. 2(Issue 10) pp:NaN2034-2034

Publication Date(Web):2011/07/21

DOI:10.1039/C1SC00340B

This study explores a series of non-helical overcrowded tetrabenzoheptafulvalene derivatives, which are different from the parent tetrabenzoheptafulvalene (1) by avoiding terminal C–C double bonds, detailing their synthesis, characterization and syn/antiisomerization. The most interesting findings from this study are that the syn and anti isomers of three overcrowded tetrabenzoheptafulvalene derivatives (3–5) can be switched by photo- and thermal isomerizations both in very high yields. The predominance of syn isomer in the photoisomerization has been explained with DFT calculations in terms of the arrangement of the excited- and ground-state potential energy surfaces. The less stable syn isomer of an overcrowded tetrabenzoheptafulvalene derivative thermally isomerizes to the corresponding anti isomer through seven-membered ring flipping, and the energy barrier of thermal isomerization is found to be directly related to the rigidity and crowdedness of the seven-membered rings. These findings suggest that overcrowded tetrabenzoheptafulvalene derivatives are promising building blocks for molecular switches and machines. In addition, the new synthesis and unambiguous characterization of hexabenzoheptafulvalene (4) have also led to correction of the previously claimed synthesis of hexabenzooctalene.

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