Spitler et al.
M) and the solution purged for 30 min with bubbling Ar. Pd(PPh3)4
(0.03 equiv per transformation) and CuI (0.06 equiv per transforma-
tion) were then added, and the solution was purged another 20 min.
Trimethylsilylacetylene (TMSA, 1.5 equiv per transformation unless
otherwise noted) was injected, and the solution was stirred at 65
°C for 12-48 h under an Ar atmosphere. Upon completion, the
mixture was concentrated, rediluted with CH2Cl2, and filtered
through a pad of silica gel. The solvent was removed in vacuo,
and the crude material was carried on to the next step without further
purification.
General Alkyne Coupling Procedure C. The tetrayne product
from procedure B was dissolved in THF (0.04 M) and purged for
30 min with bubbling Ar. Acceptor haloarene (3 equiv per
transformation unless otherwise noted) was dissolved in iPr2NH/
THF (1:1, 0.7 M) with KOH (aq, 50 wt %, 20 equiv) and purged
for 30 min with bubbling Ar. Pd(PPh3)4 (0.03 equiv per transforma-
tion) and CuI (0.06 equiv per transformation) were added to the
second solution, which was then purged another 20 min. The
protected donor alkyne was added under an Ar atmosphere via slow
injection over 8 h to the acceptor haloarene solution. The mixture
was stirred at 65 °C for 8-12 h. Upon completion, the mixture
was concentrated, rediluted with CH2Cl2, and filtered through a
pad of silica gel. The solvent was removed in vacuo, and the crude
material was purified by column chromatography.
chomatographed on silica gel (99:1 CH2Cl2/MeOH) to yield 1 (236
mg, 17%) as a dark red oil. 1H NMR (CDCl3): δ 8.92 (d, J ) 5.8
Hz, 2H), 7.73 (t, J ) 8.0 Hz, 2H), 7.66 (s, 2H), 7.60 (d, J ) 8.0
Hz, 2H), 7.42 (d, J ) 9.2 Hz, 4H), 7.35 (t, J ) 5.8 Hz, 2H), 6.59
(d, J ) 9.2 Hz, 4H), 3.30 (t, J ) 7.5 Hz, 8H), 1.59 (quin, J ) 6.9
Hz, 8H), 1.38 (sext, J ) 7.0 Hz, 8H), 0.97 (t, J ) 7.0 Hz, 12H).
13C NMR (CDCl3): δ 150.3, 148.6, 143.5, 136.5, 135.1, 133.5,
128.0, 126.9, 123.6, 123.2, 111.4, 108.6, 98.3, 94.1, 87.7, 86.3,
51.0, 29.6, 20.6, 14.3. IR (NaCl): ν 3041, 2192, 1605, 1601, 1518
cm-1. MS (APCI): m/z ([isotope]) 735.0 (M+, 100). UV (CH2Cl2)
λmax (log ꢀ): 389 (4.45), 435 (sh, 4.32). Em λmax: 547.
TFA Titration of 1-9. Solutions of 1-9 (35 µL, ∼250 µM)
were dissolved in spectrophotometric-grade MeOH (UV cutoff 204
nm) in four-sided quartz spectrophotometry cuvettes. Trifluoroacetic
acid was diluted to concentrations ranging from 10-5 to 0.8 M in
10 mL MeOH. 2 mL aliquots were added to each solution of 1-9.
The solutions were capped and shaken, and the fluorescence spectra
were then taken immediately.
Zinc Chloride Complexation to 1-9. Solutions of 1-9 (3.5
mL, ∼0.4 mM) were dissolved in spectrophotometric-grade CH2-
Cl2 (UV cutoff 250 nm) in four-sided quartz spectrophotometry
cuvettes. ZnCl2 (0.5 M) in THF was diluted to 0.01 M with CH2-
Cl2, and between 0.10 and 100 equiv were injected via microsyringe.
The solutions were capped and shaken, and the UV and fluorescence
spectra were then taken immediately.
Aluminum Chloride Addition to 1-9. Solutions of 1-9 (3.5
mL, ∼25 µM) were dissolved in spectrophotometric-grade MeOH
(UV cutoff 204 nm) in four-sided quartz spectrophotometry
cuvettes. Anhydrous AlCl3 (0.021 g, 0.16 mmol) was dissolved in
anhydrous MeOH (100 mL). Between 1 and 100 equiv of this
0.0016 M Al(III) solution were injected into the solutions of 1-9
via microsyringe. The solutions were capped and shaken, and the
fluorescence spectra were then taken immediately.
Silver Triflate Addition to 1. A solution of 1 (3.5 mL, ∼12
µM) was dissolved in spectrophotometric-grade CH2Cl2 (UV cutoff
250 nm) in a four-sided quartz spectrophotometry cuvette. Anhy-
drous AgOTf (0.0063 g, 0.025 mmol) was dissolved in anhydrous
CH2Cl2 (10 mL) with vigorous sonication for 30 min. Between 0.2
and 70 equiv of this 0.0025 M Ag(I) solution were injected into
the solution of 1 via microsyringe. The solutions were capped and
shaken, and the fluorescence spectra were then taken immediately.
Addition of Excess Metal Salts to TAEBs 1, 5, and 9. Solutions
of 1, 5, and 9 (5 mL, ∼60 µM) were dissolved in spectrophoto-
metric-grade CH2Cl2 (UV cutoff 250 nm) in 2 dram glass vials.
Solid portions of each metal salt (at least 100 equiv each) were
added to the vials. The vials were capped, shaken, and then
sonicated for 1 h. The supernatant solutions were decanted from
remaining solids (where applicable) into new vials, and the solutions
were visualized under a high-intensity 365 nm lamp (Figure 16).
Solutions containing no ion, ZnCl2, and AlCl3 were poured into
four-sided quartz spectrophotometry cuvettes, and the spectra were
taken.
1,2-Dibromo-4,5-bis[(4′-N,N-dibutylaminophenyl)ethynyl]-
benzene (21). 1,2-Dibromo-4,5-diiodobenzene29 (630 mg, 1.29
mmol) was reacted with donor alkyne 164a (798 mg, 2.65 mmol)
using general procedure A. The crude material was chromato-
graphed on silica gel (4:1 hexanes/CH2Cl2) to yield 21 (622 mg,
1
70%) as a yellow oil. H NMR (CDCl3): δ 7.71 (s, 2H), 7.39 (d,
J ) 8.8 Hz, 4H), 6.57 (d, J ) 8.8 Hz, 4H), 3.29 (t, J ) 7.5 Hz,
8H), 1.58 (quin, J ) 6.3 Hz, 8H), 1.37 (sext, J ) 7.6 Hz, 8H),
0.96 (t, J ) 7.6 Hz, 12 H). 13C NMR (CDCl3): δ 148.6, 135.6,
132.4, 128.9, 123.0, 112.5, 108.4, 97.7, 85.2, 51.0, 29.7, 20.6, 14.3.
IR (NaCl): ν 2197, 1602, 1606, 1519 cm-1. MS (APCI): m/z
([isotope]) 762.8 (M[79Br81Br] + THF, 15), 760.8 (M[79Br79Br] +
THF, 26), 692.7 (M+[81Br81Br], 55), 690.8 (M+[79Br81Br], 100),
688.7 (M+[79Br79Br], 48).
1,3-Dibromo-4,6-bis[(4′-N,N-dibutylaminophenyl)ethynyl]-
benzene (22). 1,3-Dibromo-4,6-diiodobenzene30 (355 mg, 0.73
mmol) was reacted with donor alkyne 16 (450 mg, 1.49 mmol)
using general procedure A. The crude material was chromato-
graphed on silica gel (4:1 hexanes/CH2Cl2) to yield 22 (446 mg,
89%) as a red oil. 1H NMR (CDCl3): δ 7.81 (s, 1H), 7.63 (s, 1H),
7.38 (d, J ) 9.0 Hz, 4H), 6.58 (d, J ) 9.0 Hz, 4H), 3.29 (t, J ) 7.8
Hz, 8H), 1.57 (quin, J ) 8.7 Hz, 8H), 1.35 (sext, J ) 7.6 Hz, 8H),
0.96 (t, J ) 7.6 Hz, 12H). 13C NMR (CDCl3): δ 148.6, 135.6,
134.0, 133.4, 125.9, 123.8, 111.4, 108.1, 97.4, 85.3, 51.0, 29.6,
20.6, 14.3. IR (NaCl): ν 2197, 1602, 1560, 1514, cm-1. MS
(APCI): m/z ([isotope]) 692.7 (M+[81Br81Br], 58), 691.7 (M+[13C79-
Br81Br], 40), 690.8 (M+[79Br81Br], 100), 688.7 (M+[79Br79Br], 45).
1,4-Dibromo-2,5-bis[(4′-N,N-dibutylaminophenyl)ethynyl]-
benzene (17). 1,4-Dibromo-2,5-diiodobenzene30 (1.41 g, 2.89
mmol) was reacted with donor alkyne 16 (2.00 g, 6.63 mmol) using
general procedure A. The crude material was chromatographed on
silica gel (4:1 hexanes/CH2Cl2) to yield 17 (1.77 g, 89%) as a red
oil. Spectral data match those previously reported.31
Acknowledgment. We thank the National Science Founda-
tion (CHE-0414175) for financial support. E.L.S. and L.D.S.
acknowledge the NSF for IGERT fellowships (DGE-0114419).
We thank Prof. O. H. Griffith for use of the fluorescence
spectrophotometer and Prof. U. H. F. Bunz for helpful sugges-
tions and for sharing results prior to publication.
1,2-Bis[(4′-N,N-dibutylaminophenyl)ethynyl]-4,5-bis(2-py-
ridylethynyl)benzene (1). TMSA (625 mg, 6.37 mmol) was
coupled to 21 (1.50 g, 2.17 mmol) using general procedure B. The
resulting red oil was coupled to 2-bromopyridine (1.96 g, 12.38
mmol) using general procedure C. The crude material was
Supporting Information Available: Experimental details and
spectral data of 2-9; copies of 1H NMR spectra for 1-9, 21, and
22; computational details; and emission spectra of 1-9 titrated with
TFA or complexed with ZnCl2 or AlCl3. This material is available
(29) Miljanic, O. S.; Vollhardt, K. P. C.; Whitener, G. D. Synlett 2003,
29-32.
(30) Goldfinger, M. B.; Crawford, K. B.; Swager, T. M. J. Am. Chem.
Soc. 1997, 119, 4578-4593.
(31) Tovar, J. D.; Swager, T. M. J. Organomet. Chem. 2002, 653, 215-
222.
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96 J. Org. Chem., Vol. 72, No. 1, 2007