2
Q. WU ET AL.
have used a meso-(4-formylphenyl)BODIPY for the
Cys/Hcy detection, and have found 3-(4-formylstyrene)
BODIPY unable to react with Cys and Hcy under various
temperature and pH conditions.
Herein, we report the synthesis of a series of
3-formylBODIPYs 2a–2e through the DDQ oxidation of
3-methyl substituent and their photophysical propertis.
These 3-formylBODIPYs 2a–2d showed remarkable
fluorescence enhancement with a dramatic color change
from light orange to yellowish green upon the addition of
Cys in methanol-HEPES buffer.
2H), 1.41 (s, 3H), 1.32 (s, 3H), 1.02 (t, J = 7.0 Hz, 6H).
13C NMR (75 MHz, CDCl3): d, ppm 186.0, 165.8, 160.5,
143.8, 142.3, 139.8, 137.5, 137.0, 136.1, 134.5, 132.7,
129.2, 126.7, 114.8, 55.4, 17.6, 17.1, 14.4, 14.1, 13.6,
12.5, 10.7. HRMS (EI): m/z calcd. for C24H28BF2N2O2
[M +H]+ 425.2206, found 425.2207. HRMS (EI): m/z calcd.
for C24H27BFN2O2 [M – F]+ 405.2144, found 405.2144.
3-FormylBODIPY 2b was synthesized according to
the above procedure described for 2a in 50% yield (39 mg).
1H NMR (300 MHz, CDCl3): d, ppm 10.41 (s, 1H),
7.53 (s, 3H), 7.31 (s, 2H), 2.71 (q, J = 7.5 Hz, 2H), 2.66
(s, 3H), 2.36 (q, J = 7.3 Hz, 2H), 1.36 (s, 3H), 1.27 (s,
3H), 1.03 (t, J = 6.9 Hz, 6H). 13C NMR (75 MHz,
CDCl3): d, ppm 186.1, 166.1, 143.8, 142.1, 139.9,
137.7, 137.1, 135.7, 134.7, 134.6, 129.5, 127.9, 17.6,
17.1, 14.4, 14.1, 13.7, 12.3, 10.5. HRMS (EI): m/z
calcd. for C23H26BF2N2O [M + H]+ 395.2101, found
395.2102. HRMS (EI): m/z calcd. for C23H25BFN2O
[M – F]+ 375.2039, found 375.2037.
EXPERIMENTAL
General
Reagents were purchased as reagent-grade and used
without further purification unless otherwise stated.
Solvents were used as received from communercial
suppliers unless noted otherwise. Double distilled water
was used for spectra detection. Methanol was HPLC grade
withoutfluorescentimpurities.Allreactionswereperformed
in oven-dried or flame-dried glassware unless otherwise
stated, and were monitored by TLC using 0.25 mm silica
gel plates with UV indicator (60F–254). 1H and 13C NMR
are obtained on a 300 MHz NMR spectrometer at room
temperature. Chemical shifts (d) are given in ppm relative
3-FormylBODIPY 2c was synthesized according
to the above procedure described for 2a in 47% yield
1
(43 mg). H NMR (300 MHz, CDCl3): d, ppm 10.40 (s,
1H), 7.52–7.44 (m, 3H), 2.73 (d, J = 7.3 Hz, 2H), 2.69
(s, 3H), 2.39 (d, J = 7.2 Hz, 2H), 1.47 (s, 3H), 1.39 (s,
3H), 1.07 (t, J = 7.1 Hz, 6H). 13C NMR (75 MHz,
CDCl3): d, ppm 185.8, 167.6, 142.4, 140.4, 138.1, 137.0,
135.4, 134.7, 133.1, 132.7, 131.6, 130.7, 129.2, 128.8,
17.6, 17.2, 14.4, 14.1, 14.0, 11.1, 9.3. HRMS (EI): m/z
calcd. for C23H24B35Cl2F2N2O [M + H]+ 463.1321, found
463.1315.HRMS(EI):m/zcalcd.forC23H24B35Cl37ClF2N2O
[M + H]+ 465.1292, found 465.1282. HRMS (EI): m/z
calcd. for C23H24B37Cl2F2N2O [M + H]+ 467.1262, found
467.1251. HRMS (EI): m/z calcd. for C23H23B35Cl2FN2O
[M – F]+ 443.1259, found 443.1256. HRMS (EI): m/z
calcd. for C23H23B35Cl37Cl FN2O [M – F]+ 445.123, found
445.122. HRMS (EI): m/z calcd. for C23H23B37Cl2FN2O
[M – F]+ 447.12, found 447.1192.
1
to CDCl3 (7.26 ppm for H and 77 ppm for 13C) or to
internalTMS (0 ppm for 1H). UV-visible absorption spectra
were recorded on a Shimadzu UV2450 spectrophotometer
(190–900 nm scan range). Fluorescence emission spectra
were recorded on a Hitachi F-4600 FL Spectrophotometer.
Stock solutions of amino acids were prepared in distilled
water. The stock solutions for BODIPYs 2 (1 mM) were
prepared in anhydrous methanol, and were used to prepare
the methanol-HEPES buffer (45 mM, pH = 7.2, v/v = 1/1)
solution.
3-FormylBODIPY 2d was synthesized according
to the above procedure described for 2a in 47%
yield (52 mg). 1H NMR (300 MHz, CDCl3): d,
ppm 10.35 (s, 1H), 7.13 (d, J = 7.5 Hz, 2H), 7.02 (d,
J = 8.0 Hz, 2H), 4.17 (s, 2H), 3.89 (s, 2H), 3.74 (s, 2H),
3.69 (s, 2H), 3.64 (s, 2H), 3.54 (s, 2H), 3.36 (s, 3H), 2.67
(d, J = 7.5 Hz, 2H), 2.61 (s, 3H), 2.32 (d, J = 7.2 Hz,
2H), 1.37 (s, 3H), 1.29 (s, 3H), 0.99 (t, J = 6.0 Hz, 6H).
13C NMR (75 MHz, CDCl3): d, ppm 186.1, 165.8, 159.8,
143.9, 142.3, 139.8, 137.5, 137.0, 136.1, 134.5, 132.6,
129.1, 126.8, 115.5, 71.9, 70.9, 70.7, 70.6, 69.7, 67.6,
59.0, 17.6, 17.1, 14.3, 14.0, 13.6, 12.5, 10.7. HRMS (EI):
m/z calcd. for C30H40BF2N2O5 [M + H]+ 557.2993, found
557.2990. HRMS (EI): m/z calcd. for C30H39BFN2O5
[M – F]+ 537.2931, found 537.2927.
Synthesis
FormylBODIPY 2a. To a degassed solution of
1a (82 mg, 0.2 mmol) in 8 mL THF/H2O (v/v = 100/1) was
dropwisely added a solution of DDQ (180 mg, 0.8 mmol)
in 2 mL THF at 0°C. The reaction temperature was slowly
raised to room temperature and the reaction mixture was
left stirred overnight. The reaction was quenched by adding
20 mL of water. The resulting mixture was extracted by
50 mL of dichloromethane and washed with water. Organic
layers were combined, dried over anhydrous Na2SO4,
filtered, and evaporated under vacuum to get the crude
product. The crude product was further purified using
column chromatography (silica gel, hexane/EtOAc = 6/1,
v/v) to give the desired BODIPY 2a in 48% yield (41 mg).
1H NMR (300 MHz, CDCl3): d, ppm 10.39 (s, 1H), 7.17 (d,
J = 9.0 Hz, 2H), 7.04 (d, J = 6.0 Hz, 2H), 3.89 (s, 3H), 2.71–
2.68 (d, J = 9 Hz, 2H), 2.64 (s, 3H), 2.36 (d, J = 9.0 Hz,
Fluorescence quantum yields determination
Relative fluorescence quantum efficiencies were
obtained by comparing the areas under the corrected
Copyright © 2016 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2016; 20: 2–12