Download PDF
Synlett 2007(20): 3145-3148  
DOI: 10.1055/s-2007-1000815
LETTER
© Georg Thieme Verlag Stuttgart · New York

Synthesis and Optical Properties of Ethynylene-Linked Starburst Oligofluorene Based on Hexahexyltruxene

Qing-Quan Chena, Feng Liua, Zhun Maa, Bo Penga, Wei Wei*a, Wei Huang*b
a State Key Laboratory for Advanced Photonic Materials & Devices, Fudan University, Shanghai 200433, P. R. of China
Fax: +86(21)55664170; e-Mail: iamww@fudan.edu.cn;
b Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications, Nanjing 210003, P. R. of China
e-Mail: wei-huang@njupt.edu.cn;
Further Information

Publication History

Received 3 September 2007
Publication Date:
21 November 2007 (online)

    Permissions and Reprints All articles of this category

Abstract

New monodisperse starburst oligofluorene derivatives, which contain 5,5′,10,10′,15,15′-hexahexyltruxene as the central core linked with oligo(9,9′-dihexylfluorene) as the arms through ethynylene bridge are presented. All these compounds were prepared via Sonogashira reaction. Their molecular structures were confirmed by NMR, MALDI-TOF MS spectrometry and elementary analysis. The fluorescence spectra showed that introduction of ethynylene linker showed that the optical properties of the starburst oligofluorenes were modified. Both the absorption and the fluorescence peaks were found to be red-shifted.

Key words

ethynylene linker - oligofluorene - truxene - starburst - Sonogashira reaction

12

Synthesis of 2,7,12-Triethynyl-5,5′,10,10′,15,15′-hexa­-hexyltruxene (2) 2,7,12-Tribromo-5,5′,10,10′,15,15′-hexahexyltruxene (5.42 g, 5 mmol), Pd(PPh3)2Cl2 (197.5 mg, 0.25 mmol), and CuI (47.5 mg, 0.25 mmol) were mixed with toluene-Et3N (30 mL/15 mL). Trimethylsilyl acetylene (1.80 g, 18 mmol) was slowly added to the mixture at r.t. The reaction temperature was then slowly increased and the reactant was refluxed for 24 h. The solvent was stripped off under reduced pressure. The residue was purified by column chromatography on a silica gel column, eluting with PE as the eluent to afford 2,7,12-tris[(trimethylsilyl)ethynyl]-5,5′,10,10′,15,15′-hexa­-hexyltruxene (1).
MeOH (30 mL) and aq KOH (4 mL, 20%) were added at r.t. to a stirred solution of compound 1 (2.54 g, 2.50 mmol) in THF (50 mL). The reactant was left at r.t. for 10 h. It was then poured into H2O (20 mL) and extracted three times with Et2O. The combined organic extracts were dried over anhyd MgSO4 and then filtered. The solvent was stripped off, and then refined using a silica gel column with PE as the eluent to give 2.09 g (yield 91%) of 2,7,12-triethynyl-5,5′,10,10′,15,15′-hexahexyltruxene (2) as a yellow solid.
Compound 1: 1H NMR (400 MHz, CDCl3): δ = 8.27 (1 H, d, J = 8.0 Hz), 7.53 (1 H, s), 7.52 (1 H, d, J = 8.4 Hz), 2.89-2.82 (2 H, m), 2.08-2.06 (2 H, m), 0.93-0.76 (12 H, m), 0.60 (6 H, t, J = 14.4 Hz), 0.48-0.36 (4 H, m), 0.31 (9 H, s) ppm.
Compound 2: 1H NMR (400 MHz, CDCl3): δ = 8.30 (1 H, d, J = 8.0 Hz), 7.58 (1 H, d, J = 1.6 Hz), 7.55 (1 H, d, J = 8.0 Hz), 3.19 (1 H, s), 2.91-2.84 (2 H, m), 2.09-2.01 (2 H, m), 0.93-0.78 (12 H, m), 0.60 (6 H, t, J = 14.4 Hz), 0.49-0.40 (4 H, m) ppm. 13C NMR (100 MHz, CDCl3): δ = 153.77, 146.29, 140.87, 138.11, 130.61, 126.06, 124.65, 120.11, 84.63, 77.64, 55.99, 37.09, 31.66, 29.60, 22.46, 14.06, 24.09 ppm.

13

Synthesis of Compounds D1-D3; Typical Procedure Compound 2 (91.9 mg, 0.10 mmol), compound 3 (or 4, 5; 0.45 mmol), Pd(PPh3)4 (18.0 mg), and CuI (3.0 mg) were combined in degassed toluene (25 mL) and DIPEA (10 mL). The reaction mixture was stirred at 70 °C for 48 h, and then cooled to r.t. The solvent was stripped off under reduced pressure. The residue was purified by column chromatog­-raphy on a silica gel column, eluting with PE and CH2Cl2 (20:1) as the eluent to afford the products D1-D3.
Compound D1: 1H NMR (400 MHz, CDCl3): δ = 8.38 (1 H, d, J = 8.4 Hz), 7.72-7.59 (6 H, m), 7.37-7.32 (3 H, m), 3.74-3.69 (2 H, m), 3.00-2.93 (2 H, m), 2.16-1.98 (4 H, m), 1.37-0.48 (44 H, m) ppm. 13C NMR (100 MHz, CDCl3): δ = 153.90, 151.24, 151.02, 146.08, 141.677, 140.66, 140.44, 138.24, 130.86, 130.10, 127.74, 127.10, 126.17, 125.44, 124.78, 123.10, 121.68, 121.38, 120.22, 119.90, 91.21, 90.38, 56.05, 55.39, 40.71, 37.25, 31.795, 31.75, 29.99, 29.70, 24.19, 23.97, 22.86, 22.53, 14.26, 14.13 ppm. MALDI-TOF MS: m/z = 1918.1 [M+], 1832.9 [M - C6H13]+. Anal. Calcd for C144H186: C, 90.22; H, 9.78. Found: C, 89.34; H, 9.87.
Compound D2: 1H NMR (400 MHz, CDCl3): δ = 8.42 (1 H, d, J = 8.4 Hz), 7.82-7.64 (12 H, m), 7.40-7.31 (3 H, m), 3.03-2.98 (2 H, m), 2.16-2.00 (10 H, m), 1.35-0.52 (66 H, m) ppm. 13C NMR (100 MHz, CDCl3): δ = 153.94, 152.04, 151.73, 151.36, 151.23, 146.12, 141.40, 141.30, 140.97, 140.69, 140.55, 140.48, 139.85, 138.30, 131.00, 130.15, 127.27, 127.03, 126.49, 126.30, 126.26, 125.49, 124.81, 123.16, 121.72, 121.66, 121.47, 120.48, 120.13, 119.97, 91.31, 90.55, 56.10, 55.56, 55.41, 40.70, 40.60, 37.30, 31.77, 31.70, 29.97, 29.92, 29.73, 24.23, 24.02, 22.85, 22.80, 22.54, 14.24, 14.14 ppm. MALDI-TOF MS: m/z = 2917.4 [M+], 2831.3 [M - C6H13]+. Anal. Calcd for C219H282: C, 90.25; H, 9.75. Found: C, 90.00; H, 9.80.
Compound D3: 1H NMR (400 MHz, CDCl3): δ = 8.41 (1 H, d, J = 8.0 Hz), 7.85-7.63 (18 H, m), 7.39-7.32 (3 H, m), 2.02-2.97 (2 H, m), 2.24-1.95 (14 H, m), 1.29-0.63 (88 H, m) ppm. 13C NMR (100 MHz, CDCl3): δ = 153.94, 152.05, 152.00, 151.69, 151.36, 151.22, 146.12, 141.39, 141.27, 141.00, 140.83, 140.70, 140.56, 140.48, 140.38, 140.13, 139.88, 138.29, 131.00, 130.14, 127.21, 127.01, 126.48, 126.40, 126.25, 123.14, 121.74, 121.66, 121.46, 120.49, 120.20, 120.10, 119.98, 119.94, 91.30, 90.56, 86.92, 86.41, 85.12, 56.10, 55.39, 55.56, 40.70, 40.60, 37.31, 31.77, 31.70, 31.67, 29.92, 29.97, 29.88, 29.72, 24.06, 22.85, 22.79, 22.54, 14.24, 14.13 ppm. MALDI-TOF MS: m/z = 3827.4 [M - C6H13]+. Anal. Calcd for C292H378: C, 90.26; H, 9.74. Found: C, 90.12, H, 9.95.