Molecular Electronics DOI: 10.1002/anie.201209706 Azaborine Compounds for Organic Field-Effect Transistors: Efficient Synthesis, Remarkable Stability, and BN Dipole Interactions** Xiao-Ye Wang, Hao-Ran Lin, Ting Lei, Dong-Chu Yang, Fang-Dong Zhuang, Jie-Yu Wang,* Si- Chun Yuan,* and Jian Pei* Organic semiconductors have attracted great attention during the past few decades for the development of next-generation electronics. [1] The incorporation of a B ÀN unit, which is isoelectronic to the C =C moiety, into p systems provides a novel approach in the molecular engineering of organic semiconductors. [2] BN substitution can change the electronic properties of p systems, [3] and afford additional intermolecu- lar dipole–dipole interactions. [4] Therefore, BN-incorporated semiconductors provide new opportunities for organic elec- tronics. Although significant progress has been made in azaborine chemistry, [5, 6] the construction of azaborine rings in large p scaffolds remains challenging. [7] Moreover, azaborine compounds are usually susceptible to moisture and oxygen, and their thermal decomposition temperatures are around 200 8C, thus limiting their promising applications as organic materials. [7] As a result, the charge-transport properties of azaborine compounds have rarely been investigated up to now. Only recently, Nakamura and co-workers reported a BN-fused polycyclic aromatic compound which exhibited higher intrinsic hole mobility than its carbon analog by time- resolved microwave conductivity measurements, [7f] implying that BN-substituted aromatics might outperform their carbon analogs in organic electronics. Nonetheless, electronic devices based on azaborine compounds have not yet been demon- strated. Herein, we synthesize two novel BN-substituted tetra- thienonaphthalene derivatives BN-TTN-C3 and BN-TTN-C6 through an efficient one-pot electrophilic borylation method (Scheme 1). Four thiophene rings are fused onto a BN- substituted naphthalene core to extend the p conjugated plane for intermolecular p–p stacking and charge-carrier transport. [8] Alkyl chains are attached to ensure good solubility and to tune the intermolecular interactions. [9] Our investigations indicate that the introduction of the fused thiophene rings effectively improves the aromaticity of the skeleton, and both molecules show excellent chemical and thermal stability. Importantly, organic field-effect transistors (OFETs) based on these two compounds are successfully fabricated, and high hole mobilities up to 0.15 cm 2 V À1 s À1 and on/off ratios over 10 5 are obtained from BN-TTN-C3, which represents the first example of applying azaborine com- pounds in organic electronic devices. Scheme 1 illustrates the synthetic route to BN-TTN-C3 and BN-TTN-C6. Commercially available 2-alkylthiophenes (1) were dimerized through an oxidative coupling reaction. [10] Monobromination of 2 gave compound 3, which was applied for the Buchwald–Hartwig coupling reaction. Ketimine 4 was hydrolyzed with aqueous HCl in THF to afford ammonium species 5, [11] which is more stable in air than its amino counterpart. This route is the most efficient one among various attempts to introduce amino groups onto thiophene derivatives. Subsequently, another Buchwald–Hartwig ami- nation between 3 and 5 produced compound 6. The electro- philic borylation approach was chosen to finish the final Scheme 1. Synthetic route to BN-TTN-C3 and BN-TTN-C6. Reagents and conditions: a) Ag 2 CO 3 , Pd(OAc) 2 , 2,2’-bipyridine, dioxane, reflux, 24 h; b) N-bromosuccinimide (NBS), CHCl 3 , HOAc, RT, 1 h; c) Ph 2 C = NH 2 Cl, Pd 2 dba 3 , 2,2’-bis(diphenylphosphino)-1,1’-binaphthyl (BINAP), tBuONa, toluene, 80 8C, 15 h; d) HCl (aq. 6 m), tetrahydrofuran (THF), RT, 10 minutes; e) 3, Pd(OAc) 2 , P(tBu) 3 , tBuONa, o-xylene, 120 8C, 12 h; f) BBr 3 , NEt 3 , ortho-dichlorobenzene (o-DCB), 180 8C, 12 h. [*] X.-Y. Wang, H.-R. Lin, T. Lei, D.-C. Yang, F.-D. Zhuang, Dr. J.-Y. Wang, Prof. J. Pei Beijing National Laboratory for Molecular Sciences Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education College of Chemistry and Molecular Engineering Peking University, Beijing 100871 (P. R. China) E-mail: wang-jieyu@163.com jianpei@pku.edu.cn Prof. S.-C. Yuan Department of Fundamental Science Beijing University of Agriculture Beijing 102206 (P. R. China) E-mail: ysc2007@sina.com [**] This work was supported by the Major State Basic Research Development Program (grant numbers 2009CB623601 and 2013CB933501) from the Ministry of Science and Technology and the National Natural Science Foundation of China. The authors thank Prof. Xiao-Yu Cao from Xiamen University for helpful discussions. Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/anie.201209706. A ngewandte Chemi e 3117 Angew. Chem. Int. Ed. 2013, 52, 3117 –3120  2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim