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points, while no glass transition temperatures were observed.
Broad exothermic peaks, which are typical of cross-linking reac-
tions of acetylene groups, were observed in the DSC thermograms
of each of the compounds, centered at 377, 381, 367, and 385 °C for
3a–d, respectively (see Supplementary data).23 The TGA results
clearly indicate that all of the new compounds have good thermal
stability. The decomposition temperatures (Td) corresponding to
5% weight loss were measured as 346, 424, 412, and 445 °C for
3a–d, respectively, which are much higher than that of their car-
bon analog 4. This is consistent with the finding that thermal sta-
bility may be improved by increasing the molecular volume or
incorporating a heteroatom such as silicon.24
In conclusion, we have synthesized a series of new highly emis-
sive compounds consisting of a dibenzosilole core, ethynylene link-
ages, and various peripheral chromophoric units. These
compounds exhibit blue to green emissions with high fluorescence
quantum efficiencies in solution. They also display good optical
stabilities and high thermal stabilities. Further studies on the opto-
electronic properties of the present compounds as well as the
13. Lu, G.; Usta, H.; Risko, C.; Wang, L.; Facchetti, A.; Ratner, M. A.; Marks, T. J. J. Am.
Chem. Soc. 2008, 130, 7670.
14. Chen, R. F.; Fan, Q. L.; Zheng, C.; Huang, W. Org. Lett. 2006, 8, 203.
15. A typical procedure for the synthesis of compound 2b: n-BuLi (2.5 mol/L in
hexane, 7.0 mL, 17.5 mmol) was added over 45 min to a solution of 1 (5.0 g,
8.0 mmol) in dry THF (80 mL) dropwise at ꢀ90 °C. The reaction mixture was
stirred for further 2 h at ꢀ90 °C. Then dichlorodiphenylsilane (3.4 mL,
16.0 mmol) was added and the mixture was allowed to room temperature
for 0.5 h and gently refluxed for 6 h. After cooled to room temperature, the
reaction mixture was quenched with a saturated NH4Cl aqueous solution, and
extracted with chloroform. The organic layer was washed with brine, dried
over MgSO4, filtered, and concentrated under reduced pressure. The mixture
was purified by recrystallization from chloroform/ethanol to give 2b (3.0 g,
5.4 mmol) in 68% yield as colorless crystals, mp 266 °C (DSC data). Compound
2a: colorless crystals, 93% yield, mp 221 °C (DSC data). All the spectroscopic
data of 2a and 2b were identical to that reported.14
incorporation of ethynyl-linked dibenzosilole units into
gated polymers are underway in our laboratory.
p-conju-
16. For the synthesis of (4-ethynylphenyl)diphenylamine, see: McIlroy, S. P.; Cló,
E.; Nikolajsen, L.; Frederiksen, P. K.; Nielsen, C. B.; Mikkelsen, K. V.; Gothelf, K.
V.; Ogilby, P. R. J. Org. Chem. 2005, 70, 1134.
Acknowledgment
17. A typical procedure for the synthesis of compounds 3a–d: To a 25 mL flask was
charged with dibromodibenzosilole (0.54 mmol), Pd(PPh3)4 (62 mg,
0.054 mmol), and CuI (21 mg, 0.11 mmol). Then piperidine (6 mL) and
arylacetylene (1.62 mmol) were added. The mixture was stirred at 80 °C for
8 h. After concentrated, water (10 mL) was added and the mixture was
extracted with dichloromethane. The combined organic layers were washed
with brine (20 mL), dried over MgSO4, filtered, and concentrated under
The authors gratefully acknowledge the National Science Foun-
dation of China (NSFC, Nos. 50673094 and 20774102) for financial
support.
reduced pressure. The residue was purified by
a silica gel column
Supplementary data
chromatography to afford the title compound. Compound 3a: yield: 65%; 1H
NMR (400 MHz, acetone-d6): d 7.82 (s, 2H), 7.74 (s, 2H), 7.55 (d, J = 6.9 Hz, 4H),
7.41 (m, 6H), 4.03 (s, 6H), 0.46 (s, 6H); 13C NMR (100 MHz, acetone-d6): d 163.5,
150.4, 138.4, 132.2, 131.9, 129.4, 129.1, 124.8, 113.0, 105.5, 94.6, 87.6, 56.4, -
3.1; MS (EI) m/z (%): 470 (M+, 100%); Anal. Calcd for C32H26O2Si: C, 81.66; H,
5.57. Found: C, 81.44; H, 5.48. Compound 3b: yield: 59%; 1H NMR (400 MHz,
acetone-d6): d 7.98 (s, 2H), 7.87 (s, 2H), 7.73 (dd, J = 1.4, 7.7 Hz, 4H), 7.55 (dd,
J = 1.7, 7.7 Hz, 4H), 7.49–7.36 (m, 12H), 4.06 (s, 6H); 13C NMR (150 MHz,
acetone-d6): d 163.0, 150.4, 138.3, 135.3, 132.6, 131.3, 130.3, 128.5, 128.3,
127.8, 123.7, 112.7, 105.1, 94.1, 86.4, 55.6; MS (EI) m/z (%): 594 (M+, 100%);
Anal. Calcd for C42H30O2Si: C, 84.81; H, 5.08. Found: C, 84.80; H, 5.08;
Compound 3c: yield: 75%; 1H NMR (400 MHz, acetone-d6): d 8.03 (s, 2H), 7.91
(s, 2H), 7.76 (s, 8H), 7.73 (d, J = 7.5 Hz, 4H), 7.49–7.42 (m, 6H), 4.08 (s, 6H); 13C
NMR (100 MHz, acetone-d6): d 164.2, 151.8, 139.5, 136.2, 133.3, 132.8, 131.2,
130.2, 129.9, 129.2, 128.9, 126.4, 123.8, 113.0, 106.2, 93.6, 90.0, 56.6; MS (EI)
m/z (%): 730 (M+, 100%); Anal. Calcd for C44H28F6O2Si: C, 72.32; H, 3.86. Found:
C, 72.65; H, 3.58; Compound 3d: yield: 83%; 1H NMR (400 MHz, CDCl3): d 7.86
(s, 2H), 7.66 (d, J = 6.7 Hz, 4H), 7.44–7.35 (m, 12H), 7.28 (t, J = 7.7 Hz, 8H), 7.12
(d, J = 7.8 Hz, 8H), 7.06 (t, J = 7.4 Hz, 4H), 7.00 (d, J = 8.6 Hz, 4H), 4.08 (s, 6H);
13C NMR (100 MHz, CDCl3): d 162.6, 149.9, 147.9, 147.4, 138.8, 135.6, 132.7,
132.6, 130.3, 129.5, 128.4, 128.3, 125.1, 123.6, 122.5, 116.6, 113.3, 104.0, 95.1,
85.6, 56.2; MALDI-TOF: calcd: 928.3, found: 928.7; Anal. Calcd for
C66H48N2O2Si: C, 85.31; H, 5.21; N, 3.01. Found: C, 85.09; H, 5.38; N, 3.17.
18. Crystallographic data for 3b has been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication number CCDC
721777. Copies of the data may be obtained, free of charge, on application to
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax: +44(0)1223 336033 or
email: deposit@ccdc.cam.ac.uk).
Supplementary data (fluorescence spectra of 3a in different sol-
vent, 1H and 13C NMR spectra, TGA and DSC curves for all new com-
pounds) associated with this article can be found, in the online
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