Polymer Preprints 2007, 48(2), 64-65 SYNTHESIS AND CHARACTERISATION OF CARBAZOLE CONTAINING UNSYMMETRICAL BENZOPERYLENES Vajiravelu Sivamurugan and Suresh Valiyaveettil* Department of Chemistry National University of Singapore 3 Science Drive 3 Singapore, 117 543 Introduction Hyper branched planar benzene molecules such as coronene, benzo[ghi]perylene and perylene and other polycyclic aromatic analogs are promising semi-conducting organic compounds. 1 In particular the synthesis of substituted unsymmetrical polycyclic aromatic hydrocarbons is more attractive due to their enhanced electronic properties than corresponding symmetrical analog. 2 Among the electro active molecules the carbazole derivatives are strong electron-hole transporting molecules. Materials containing carbazole moieties are having xerographic, 3 photorefractive 4 and light-emitting applications 5 due to their superior charge-transport properties. These hyper- branched planar polyphenylene molecules with hydrophobic long alkyl chain could prevent the formation of aggregates, exhibit stable emission spectrum and improve solubility. 6 Our continued interest in the developing of non- symmetrical disk shaped molecules 7a and conjugated polymers 7b that can self- assemble through non-covalent interactions. Here we report the synthesis of n- dodecyl group bearing carbazole unit substituted novel unsymmetrical benzo[ghi]perylene molecules (CBP 1 and CBP 2). N R1 R2 C12H25 C12H25 C12H25 R 1 = R 2 = C 12 H 25 - CBP 1 R 1 = R 2 = Br - CBP 2 Experimental Materials. All chemicals and reagents were purchased from Aldrich, Fluka and Lanchaster and used as such without any further purification. All the reactions were accomplished in distilled anhydrous solvents under inert atmosphere. Instrumentation. The NMR spectral data of all synthesized samples were recorded on a Bruker ACF 300 spectrometer operating at 300 and 75.5 MHz for 1 H and 13 C nuclei respectively using CDCl 3 solvent and TMS as internal standard. Molecular weight of the target molecules was determined by MALDI-TOF using Applied Biosciences Voyager System 4134 and -cyano-4-hydroxy cinnamic acid as a matrix under reflector mode of operation. The absorbance and fluorescence spectra were recorded on a Shimadzu 3101 PC spectrophotometer and RF-5301PC Shimadzu spectrofluorophotometer respectively in THF solvent under normalized concentration. Synthesis of PBC 1 (5a) and PBC 2(5b): 1-(N-n-dodecyl-3- carbazoyl) acetylene (4) (81.58 mg, 0.2260 mmol) and 3a (160 mg, 0.1512 mmol) or 3b (100 mg, 0.1141 mmol) in diphenylether (1.5 mL) was refluxed under an atmosphere of N 2 for 18h. After cooling to room temperature, MeOH was added and the brownish oil was separated and it was further purified by column chromatography over SiO 2 (10% CH 2 Cl 2 /n-Hexane) to afford pure products. PBC 1 as a fluorescent yellow oil (180 mg, 60%). 1 H NMR(300 MHz, CDCl 3 ). 1 H NMR (300 MHz, CDCl 3 ). 7.63 (s, 1H, Ar-H), 7.28-7.22 (m, 6H, Ar-H), 7.04-6.89 (m, 8H, Ar-H), 6.67 -6.57 (m, 8H, Ar-H), 4.15-4.10 (t, 2H, N-CH 2 ), 2.44-2.27 (m, 2H, N-CH 2 -CH 2 ), 1.47-0.78 (m, 100H, n-dodecyl) . 13 CNMR (75 MHz, CDCl 3 ) 141.1, 140.5, 139.5, 139.4, 139.3, 131.6, 131.5, 131.4, 129.8, 129.7, 128.1, 127.5, 126.9, 126.5, 123.2, 123.0, 118.8, 107.4, 77.4, 77.0, 76.5, 42.5 (N-CH 2 ), 35.5 (N-CH 2 -CH 2 ), 31.9, 31.3, 31.2, 29.7, 29.7, 29.6, 29.6, 29.5, 29.5, 29.4, 29.3, 28.9, 28.8, 27.3, 22.7, 14.1. MS (MALDI-TOF) m/z 1388.17 (100%) [M+] (calcd for C 102 H 149 N, 1389), Calculated for C 102 H 149 N C, 88.18, H, 10.81, N, 1.01 %. Found C, 88.60, H, 11.36, N, 1.25% PBC 2 as a yellow oil (110 mg, 60%). 1 H NMR (300 MHz, CDCl 3 ) 7.90 (s, 1H, Ar-H) 7.56 (s, 1H, Ar-H), 7.31-7.01 (m, 6H, Ar-H), 6.98-6.91 (m, 8H, Ar-H), 6.69-6.56 (m, 8H, Ar-H), 4.18-4.03 (t, 2H, N-CH 2 ), 1.35-1.23 (m, 2H, N-CH 2 -CH 2 ), 1.19-1.17 (m, 10H, Ar-CH 2 ), 0.90-0.76 (m, 86H, n-dodecyl). 13 CNMR (75 MHz, CDCl 3 ) 156.0, 155.8, 155.7, 155.6, 155.1, 154.4, 146.3, 144.2, 140.5, 139.6, 139.4, 138.6, 138.4, 138.1, 131.5, 131.2, 131.1, 129.9, 129.3, 124.1, 122.1, 118.9, 77.3, 76.9, 76.4, 41.2 (N-CH 2 ), 36.0 (N-CH 2 - CH 2 ), 34.6, 31.8, 31.5, 31.1, 29.6, 29.5, 29.4, 29.4, 29.3, 29.2, 28.9, 26.8, 25.2, 22.7, 22.5, 22.5, 20.6, 18.6, 14.0, 11.3. MS (MALDI-TOF) m/z 1209.18 (100%) [M+] (calcd for C 78 H 99 NBr 2 , 1210.20), Calculated for C 78 H 99 NBr 2 C, 77.40, H, 8.24, N, 1.16 % ; found C, 77.65, H, 8.56, N, 1.25% Synthesis of CBP 1 and CBP 2: To a solution of PBC 1 (85 mg, 0.0615 mmol) or PBC 2 (85 mg, 0.07022 mmol) in anhydrous dichloromethane (200 mL) taken in a flame dried flask, FeCl 3 (798 mg, 4.92 mmol) dissolved in nitromethane (8 mL) was added dropwise. The reaction mixture was purged under a constant stream of N 2 . After stirring for 45 min, large excess of methanol was added to quench the reaction. The precipitated solid was filtered washed with methanol, redissolved in dichloromethane and purified by column chromatography (SiO 2 , 30% CH 2 Cl 2 /Hexane) to affords fluorescent yellow oil (CBP 1) (60 mg, 75%) and affords an orange solid (CBP 2) (68 mg, 78%) respectively. CBP 1: 1 H NMR (300 MHz, CDCl 3 ) 7.26-7.22 (d, 2H, Ar-H) 7.18-7.00 (m, 4H, Ar-H), 6.95-6.90 (m, 4H, Ar-H), 6.88-6.84 (m, 4H, Ar-H), 4.93-4.78 (t, 2H, N-CH 2 ), 2.20-2.18 (m, 4H, N-CH 2 -CH 2 ), 1.49-1.18 (m, 4H, Ar-CH 2 ), 0.80-0.76 (m, 84H, n-dodecyl). 13 CNMR (75 MHz, CDCl 3 ) 150.0, 139.9, 135.7, 129.7, 129.6, 127.1, 126.5, 125.5, 118.7, 118.6, 118.5, 118.4, 118.4, 108.1, 77.4, 77.0, 76.5, 43.4 (N-CH 2 ), 37.1, 34.2, 33.7, 33.4, 32.7, 31.9, 31.4, 30.3, 30.1, 30.0, 29.6, 29.3, 27.0, 22.6, 19.7, 19.6, 14.1. MS (MALDI-TOF) m/z 1380.11 (100%) [M+] (calcd for C 102 H 141 N, 1381.10). Calculated for C 102 H 141 N C, 88.70, H, 10.29, N, 1.01 %. Found C, 89.09, H, 10.46, N, 1.15%. CBP 2: 1 H NMR (300 MHz, CDCl 3 ) 8.19 (s, 1H, Ar-H), 7.71-49 (m, 4H, Ar- H), 7.49-7.18 (m, 4H, Ar-H), 7.04-6.92 (m, 4H, Ar-H), 4.24-4.09 (m, 2H, N- CH 2 ), 2.35-2.28 (m, 4H, N-CH 2 -CH 2 & Ar-CH 2 ), 1.18-0.78 (m, 84H, N- dodecyl). 13 CNMR (75 MHz, CDCl 3 ) 146.1, 145.0, 140.5, 139.3, 138.4, 138.3, 137.7, 137.6, 137.6, 136.4, 133.3, 132.8, 131.6, 131.2, 129.7, 127.1, 120.6, 118.8, 42.5 (N-CH 2 ), 37.4, 36.7, 31.9, 31.1, 30.9, 30.1, 29.7, 29.6, 29.5, 29.3, 29.0, 28.9, 28.9, 28.8, 26.7, 22.7, 14.1, 14.0, 10.0. MS (MALDI- TOF) m/z 1202.47 (100%) [M+] (calcd for C 78 H 91 NBr 2 , 1201.10) Calculated for C 78 H 91 NBr 2 C, 77.92, H, 7.63, N, 1.16 % ; found C, 77.65, H, 7.93, N, 1.03%. Results and Discussion The Diels-Alder cycloaddition reaction is selected as a convenient approach to obtain hyper-branched polyphenylene with high yield. The cycloaddition reaction of terminal as well as bisubstituted alkyne with cyclopentadienone affords benzo[ghi]perylene and coronene precursor in quantitative yield. In the present investigation hyperbranched polyphenylenes such as PBC 1 and PBC 2 have been obtained by using high temperature [4]+[2] Diels-Alder cycloaddition of N-dodecyl carbazole functionalized terminal alkyne (2) with n-dodecyl substituted tetraphenylcyclopentandienone (1) in diphenylether which gives 60 - 50% yield in 18h reaction time at 260 C. It is interesting to note that the terminal alkynes are most reactive and high yielding than bisubstituted alkynes. The non-symmetrically substituted cyclopentadienones are most interesting molecule and which can be used as a building block in novel polycyclic aromatic syntheses. These molecules can be easily co-planarised using oxidation (cyclodehydrogenation) reactions as reported by earlier literature. Our target molecules CBP 1 and CPB 2 were obtained in 55% and 76% yield, respectively, by oxidative cyclisation (coplanarisation) of corresponding PBC 1 and PBC 2 using FeCl 3 as a catalyst (Scheme 1).