Available online at www.sciencedirect.com Journal of Molecular Structure 889 (2008) 265–270 www.elsevier.com/locate/molstruc Synthesis and crystal structure of 5,12-diphenyl-6, 11-bis(thien-2-yl)tetracene Yanhui Hou a, Xiaoliu Chi b, Xiangjian Wan a, Yongsheng Chen a,* a Key Laboratory for Functional Polymer Materials and Center for Nanoscale Science and Technology, Institute of Polymer Chemistry, College of Chemistry, Nankai University, Weijin Road 94, Tianjin 300071, China b Department of Chemistry, Texas A&M University – Kingsville, Kingsville, TX 78363, USA Received 21 January 2008; received in revised form 9 February 2008; accepted 11 February 2008 Available online 19 February 2008 Abstract 5,12-Diphenyl-6,11-bis(thien-2-yl)tetracene (1) was prepared by reduction of 5,12-diphenyl-6,11-bis(thien-2-yl)-6,11-tetracenediol (3) 0 with NaBH3CN in the presence of weak Lewis acid ZnI2. A rearranged byproduct, 6,11-dihydro-5,12-diphenyl-6,6 -bis(thien-2-yl)-11, 110-dihydrotetracene (5), was also obtained under this condition. Treatment of compound 3 with HI or other strong Lewis acid led to rearrangement and afforded 5,12-diphenyl-6,60-bis(thien-2-yl)tetracene-11-one (4). The structures of compounds 1, 4 and 5 were confirmed by single crystal X-ray diffraction. The central tetracene rings of molecules 1 are twisted and assemble into arrays with slip parallel mol- ecules in the crystal structure. There is no p–p overlap among the tetracene rings or among the pendant phenyl rings and thienyl rings. Ó 2008 Elsevier B.V. All rights reserved. Keywords: Tetracene; Crystal structure; Synthesis; Rearrangement; Reduction 1. Introduction peculiar electronic and optoelectronic materials, which has been successfully used in many organic semi-conductor The polycyclic aromatic hydrocarbon (PAH), rubrene devices [13–15]. Herein we wish to report the synthesis of a (5,6,11,12-tetraphenyltetracene) has been widely investi- new thienyl substituted rubrene derivative, 5,12-diphenyl- gated for more than three decades [1,2]. Over past few 6,11-bis(dithien-2-yl)tetracene (1) (Chart 1). Although years, rubrene has offered one of the best materials for chemical structure of compound 1 is very similar to that organic electronic and optoelectronic devices due to its of rubrene, the synthesis procedure and the crystal struc- high mobility. And it has been successfully used in organic ture of 1 are obviously different from those of rubrene. light-emitting diodes (OLED) [3–5] and organic field-effect And two rearranged compounds were also obtained, unex- transistors (OFETs) [6–9]. For its wide variety of interest- pectedly. Their structures were all confirmed by the single ing properties, there has been an increasing interest in the crystal X-ray diffractions. synthesis of new specifically substituted rubrene derivatives in the last years. However, these rubrene derivatives were 2. Experimental mostly prepared by introduction of substituent on the pen- dant phenyl rings, rather than directly on the tetracene 2.1. General backbone ring [10–12]. As an electron-rich substituent, thi- enyl has been used as a popular building block for many NMR spectra were obtained on a Bruker AC-300 Spec- trometer (300-MHz) as CDCl3 solution using TMS as the internal standard. Elemental analyses were performed * Corresponding author. Tel.: +86 22 23500693; fax: +86 22 23499992. using a Thermo Electron FLASH/EA 1112 instrument. E-mail address: [email protected] (Y. Chen). Mass spectra were carried out on a Thermofinnigan LCQ 0022-2860/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2008.02.007 266 Y. Hou et al. / Journal of Molecular Structure 889 (2008) 265–270 for C38H24OS2: C, 81.40; H, 4.31; O, 2.85; S, 11.44%. S Found: C, 81.44; H, 4.26; O, 2.81; S, 11.49%. 2.2.3. 5,12-Diphenyl-6,11-bis(thien-2-yl)tetracene (1) and 6,11-dihydro-5,12-diphenyl- 6,60-bis(thien-2-yl)-11, 110-dihydrotetracene (5) S A suspension of diol 3 (0.64 g, 1.1 mmol), ZnI2 (1.01 g, 3.4 mmol) and NaBH3CN (0.69 g, 11 mmol) in 1,2-dichlo- roethane (10 mL) was refluxed (under argon and protected rubrene 1 from light) for 20 h. After cooling to room temperature, Chart 1. Chemical structures of rubrene and compound 1. dichloromethane (30 mL) was added and the solids were filtered off. The clear filtrated was washed with diluted Advantage mass spectrometer. All reagents are commer- HCl (3 M, 3 Â 30 mL) and dried (MgSO4), then concen- cially available and purified by standard methods prior to trated in vacuum. The residue was purified by column use. 6,11-Diphenyl-5,12-tetracenequinone (2) was synthe- chromatography (SiO2, eluent–hexanes) to give compound sized as described in the literature [16]. 1 (yield 57%) as red crystals and the byproduct 5 as white crystals (yield 30%). 1 Compound 1 was a red solid: Mp 248–250 °C. H NMR 2.2. Synthesis (400 MHz, CDCl3): d 7.57–7.54 (m, 2H), 7.42 (broad, 2H), 7.23–7.13 (m, 14H), 6.93 (broad, 2H), 6.73 (broad, 2H), + 2.2.1. 5,12-Diphenyl-6,11-bis(thien-2-yl)-6,11-tetracenediol (3) 6.44 (broad, 2H). MS (EI) m/z 544 (M ). Elemental anal- To 6,11-diphenyl-5,12-tetracenequinone (5.1 g, 12.5 mmol) ysis calcd for C38H24S2: C, 83.79; H, 4.44; S, 11.77%. in 150 ml dry THF at À78 °C under argon atmosphere, Found: C, 83.85; H, 4.47; S, 11.68%. 1 1 M 2-thienyllithium THF solution (30 mL) was added Compound 5 was a white solid: Mp 286–288 °C. H slowly. The mixture was allowed to slowly warm up to NMR (400 MHz, d-acetone): d 7.62–7.53 (m, 3H), room temperature and stirred overnight. The reaction 7.44–7.39 (m, 3H), 7.28 (t, J = 6.6 Hz, 1H), 7.17 was worked up with aqueous solution of saturated NH4Cl, (t, J = 7.4 Hz, 1H), 7.07–6.90 (m, 10H), 6.83 (d, J = and extracted with Et2O. The combined organic extracts 6.8 Hz, 2H), 6.65–6.60 (m, 4H), 3.86 (s, 2H). MS (EI) + were dried (MgSO4) and then concentrated in vacuum. m/z 546 (M ). Elemental analysis calcd for C38H26S2:C, The resulting solid was washed thoroughly with 4:1 hex- 83.48; H, 4.79; S, 11.73%. Found: C, 83.54; H, 4.75; S, anes–Et2O to give an off-white solid (yield 87%). Mp 172– 11.71%. 174 °C. 1H NMR (400 MHz, d-acetone): d 7.62 (d, J = 7.4 Hz, 2H), 7.48–7.45 (m, 4H), 7.31 (t, J = 7.4 Hz, 2.3. X-ray crystallography 2H), 7.20–7.19 (m, 2H), 7.09–6.98 (m, 8H), 6.65 (t, J = 4.3 Hz, 2H), 6.44 (d, J = 5.4 Hz, 2H), 6.22 (d, The diffraction-quality single crystals of 1, 4, 5 were J = 7.5 Hz, 2H), 5.62 (s, 2H). MS (EI) m/z 578 (M+). Ele- mounted on glass fibers in random orientation using mental analysis calcd for C38H26O2S2: C, 78.86; H, 4.53; O, epoxy-glue. Bruker SMART 1000 CCD automatic diffrac- 5.53; S, 11.08%. Found: C, 78.79; H, 4.51; O, 5.58; S, tometer was used for data collection at T = 294(2) K 11.12%. using graphite monochromated MoKa-radiation (k = 0.71073 A˚ ). The structures were solved by direct methods, and all non-hydrogen atoms were subjected to anisotropic 2.2.2. 5,12-Diphenyl-6,60-bis(thien-2-yl)tetracene-11-one (4) refinement by full-matrix least squares on F2 using the To a 50 mL Et2O solution of diol 3 (1.15 g, 2 mmol), SHELXTL package. More details on data collection and 57% HI water solution (50 mL) was added at room tem- structure calculation are summarized in Table 1. Crystallo- perature. The mixture was stirred for 0.5 h before addi- graphic data for all structures reported here have been tion of a saturated aqueous solution of sodium deposited with the Cambridge Crystallographic Data Cen- metabisulfite. The aqueous portion was extracted with tre; CCDC numbers are given in Table 1. Et2O, and the combined organic extracts immediately dried (MgSO4) and concentrated in vacuo to give a 3. Results and discussion red solid, which was recrystallized from CHCl3–acetone to give 4 as a bright red crystalline solid (yield 82%). 3.1. Synthesis 1 Mp 262–264 °C; H NMR (400 MHz, CDCl3): d 7.82 (d, J = 7.6 Hz, 1H), 7.64–7.51 (m, 4H), 7.45–7.43 The key intermediate, 5,12-diphenyl-6,11-bis(thien-2- (m, 2H), 7.39–7.29 (m, 2H), 7.21–7.18 (m, 3H), 7.08– yl)-6,11-tetracenediol (3), was synthesized, by the addition 7.06 (m, 4H), 7.02–6.97 (m, 2H), 6.71 (d, J = 3.7 Hz, of 5,12-diphenyl-6,11-tetracenequinone (2) with thienylli- 2H), 6.64 (t, J = 5.1 Hz, 2H), 6.57 (d, J = 8.1 Hz, 2H). thium (Scheme 1), and fully characterized. HI has been MS (ESI) m/z 561 (MH+). Elemental analysis calcd used widely to reduce tetracenediols for rubrene derivatives Y. Hou et al. / Journal of Molecular Structure 889 (2008) 265–270 267 Table 1 Experimental data for the X-ray diffraction studies of prepared compounds at 294(2) K 14 5 No.