T.W. Hudnall et al. / Journal of Fluorine Chemistry 131 (2010) 1182–1186
1185
and dichlorophenyl borane were purchased from Aldrich and
4.4.2. Synthesis of 3
used without further purification. Potassium hydrogen difluor-
ide (KHF2) was purchased from Alfa Aesar. Et2O and THF were
dried by reflux over Na/K. Toluene, hexane and dichloromethane
were dried by passing through a column charged with activated
alumina. Air-sensitive compounds were handled under a N2
atmosphere using standard Schlenk and glovebox techniques.
Elemental analyses were performed at Atlantic Microlab
(Norcross, GA). NMR spectra were recorded on a Varian Unity
Inova 400 FT NMR (399.59 MHz for 1H, 375.99 MHz for 19F,
128.19 MHz for 11B, 100.45 MHz for 13C) spectrometer at
A freshly prepared solution of 2 (prepared using 100 mg of 1) in
toluene (10 mL) was quickly eluted over a short plug of silica gel.
The solvent was removed under reduced pressure to afford an
orange-red residue which was recrystallized at ꢁ40 8C in EtOAc
(5 mL). The resulting red-orange microcrystalline solid was
collected by filtration and dried in vacuo to give 3 (69 mg, 97%
yield). 1H NMR (399.59 MHz, CDCl3):
d 2.18 (s, 6H, dipyrrin-CH3),
2.43 (s, 6H, dipyrrin-CH3), 2.65 (s, 3H, dipyrrin-CH3), 5.93 (s, 2H,
dipyrrin-CH), 7.07(m, 1H, phenyl-CH), 7.13 (t, 2H, 2J = 6.0 Hz,
phenyl-CH), 7.31 (d, 2H, 2J = 7.0 Hz, phenyl-CH), OH signal not
ambient temperature. Chemical shifts
d
are given in ppm, and
observed. . 13C NMR (100. 48 MHz, CDCl3):
d
16.47, 16.81, 17.77,
122.54, 126.51, 126.90, 131.65, 133.49, 140.54, 141.41, 154.34. B–C
peak not observed. 11B NMR (128.20 MHz, CDCl3):
0.97.
fluo = 512 nm (MeOH, = 69%). Anal. Calcd for C20H24BO1.5N2
are referenced against external Me4Si (1H, 13C), BF3ꢂEt2O (11B)
and CFCl3
(
19F).
d
l
F
4.2. Crystallographic measurements
(3ꢂ0.5H2O): C, 73.41; H, 7.39. Found: C, 73.77; H, 7.41.
The crystallographic measurement of 2 was performed using a
4.4.3. Synthesis of 4
Bruker APEX-II CCD area detector diffractometer, with a graphite-
˚
(l = 0.71073 A); and com-
A THF (5 mL) solution of 3 (50 mg, 0.157 mmol) was treated
with KHF2 (74 mg, 0.943 mmol) and stirred for 24 h. The reaction
mixture was then quenched with water (10 mL) and extracted
with dichloromethane (3ꢀ 5 mL). The organic layers were
combined, dried over MgSO4, and filtered. The solvent was
removed under reduced pressure and the residue was recrystal-
lized at ꢁ40 8C from EtOAc (5 mL) to afford 4 as a bright orange
crystalline solid (46 mg, 91% yield). 1H NMR (399.59 MHz, CDCl3):
monochromated Mo-K radiation
a
pounds 3 and 4 were measured using a Bruker SMART-97 CCD
instrument. Single crystals of 2 were obtained by slow evaporation
of a concentrated toluene solution under an atmosphere of N2.
Single crystals of 3 and 4 were grown from ethyl acetate at ꢁ40 8C.
In each case, a specimen of suitable size and quality was selected
and mounted onto glass fiber with apiezon grease. The structure
was solved by direct methods, which successfully located most of
the non-hydrogen atoms. Subsequent refinement on F2 using the
SHELXTL/PC package (version 5.1) allowed location of the
remaining non-hydrogen atoms.
d
2.15 (s, 6H, dipyrrin-CH3), 2.42 (s, 6H, dipyrrin-CH3), 2.66 (s, 3H,
dipyrrin-CH3), 5.94 (s, 2H, dipyrrin-CH), 7.10(t, 1H, 2J = 4.5 Hz,
phenyl-CH), 7.15 (t, 2H, 2J = 7.0 Hz, phenyl-CH), 7.31 (d, 2H,
2J = 7.0 Hz, phenyl-CH). 13C NMR (100. 48 MHz, CDCl3):
d 16.50,
16.81, 17.79, 122.49, 126.53, 126.92, 131.61, 133.51, 140.52,
4.3. UV–vis and fluorescence measurements
141.44, 154.38. B–C peak not observed. 19F NMR (375.97 MHz,
CDCl3):
d
ꢁ174.2 11B NMR (128.20 MHz, CDCl3):
d 2.51 (bs).
UV–vis spectra were recorded on an Ocean Optics USB4000
spectrometer with a Ocean Optics ISS light source. Steady state
emission spectra were collected at room temperature using a PTI
QuantaMaster 4 fluorescence spectrophotometer equipped with
a Model 810 PMT detector. The spectra of 3 and 4 were
lfluo = 512 nm (MeOH, F = 77%). Anal. Calcd for C20H22BFN2: C,
75.02; H, 6.93. Found: C, 74.95; H, 6.96.
5. Supplementary data
measured in MeOH with a substrate concentration of 10.5
The quantum yields were measured using fluorescein in a 0.1 M
NaOH solution.
mM.
Crystallographic data (as cif files) for 2, 3 and 4 have been
deposited with the Cambridge Crystallographic Data Centre
(deposition numbers CCDC 770591, 770592 and 770593 respec-
tively). Copies of the data can be obtained free of charge on
application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK, fax:
4.4. Synthesis
4.4.1. Synthesis of 2
Compound 1 (100 mg, 0.40 mmol) was dissolved in 5 mL
of a Et2O/hexanes (1:1, v:v) solvent mixture. To this solution,
NaH (20 mg, 0.83 mmol) was added slowly at room temperature
in a drybox. The suspension was stirred overnight in the
drybox then the solvent was removed in vacuo. The resulting
residue was extracted with hexanes, filtered, and the
solvent was again removed in vacuo. The sodium salt of 1
was then taken into a drybox, dissolved in toluene (10 mL) and
PhBCl2 (380 mg, 2.4 mmol) was added slowly which resulted in
the appearance of a green fluorescence. The solution was stirred
in the drybox overnight then filtered over Celite. Slow
Acknowledgments
Support by the National Science Foundation (CHE-0646916 and
CHE-0952912), the Welch Foundation (A-1423), Texas A&M
University (Davidson Professorship) and the Laboratory for
Molecular Simulation at Texas A&M University (software and
computation resources) is gratefully acknowledged.
References
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evaporation of the toluene produced
crystals of
(75 mg, 56% yield, not optimized). 1H NMR
(399.59 MHz, CDCl3): 1.93 (s, 6H, dipyrrin-CH3), 2.44 (s, 6H,
dipyrrin-CH3), 2.67 (s, 3H, dipyrrin-CH3), 5.97 (s, 2H, dipyrrin-
CH), 7.17–7.22 (m, 3H, phenyl-CH), 7.55 (d, 2H, 2J = 8.0 Hz,
a crop of dark red
2
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d
phenyl-CH). 13C NMR (100.48 MHz, CDCl3):
d
16.36, 16.73, 17.74,
122.60, 126.47, 126.93, 131.45, 133.29, 140.24, 141.38, 154.73.
B–C peak not observed. 11B NMR (128.20 MHz, CDCl3):
2.53.
d
Satisfactory elemental analysis could not be obtained for this
compound.
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