2
40
Y. Kai et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 118 (2014) 239–243
fluorosis; nephrotoxic changes; skeletal fluorosis and urolithiasis
7–10], especially Sodium Fluoride (NaF), which can influence vari-
Synthesis of compound 3 (4-methoxy-N-butyl-1,8-naphthalimide)
Compound 2 (5.4 g, 16.3 mmol) and CH ONa (7.0 g, 130 mmol)
were added to 50 mL CH OH. After refluxing in a nitrogen atmo-
sphere for 8 h, remove the solvent and purify the solid by column
chromatography. Compound 3 was obtained as yellow needles in
80% yield.
[
3
ous cell signaling process, inhibit the formation of biological mate-
rials and induce apoptosis in mammalian cells at high concentration
for long time [11–13]. Thus novel methods with high selectivity and
sensitivity for detecting of fluorides ion, particularly NaF, is more
and more important in chemical and biological systems.
3
Among the various methods, fluorescent probes are remarkable
due to their apparent advantages over other methods such as rap-
idness, simplicity and high sensitivity [14–16]. Recently, a variety
of fluorogenic chemosensors showing absorbance or fluorescence
Synthesis of compound 4 (4-hydroxy-N-butyl-1,8-naphthalimide)
4-methoxy-N-butyl-1, 8-naphthalimide (4.0 g, 14.1 mmol) and
100 mL HI (57%) was stirred and refluxed for 5 h. After cooling
and filtration, yellow compound 4 were obtained in 85% yield. 1
H
À
changes upon binding with F have been reported [17–20]. How-
NMR (300 MHz, DMSO) 0.94 (t, J = 14.7 Hz, 3H), 1.30–1.42 (m,
2H), 1.55–1.65 (m, 2H), 4.01 (t, J = 14.7 Hz, 2H), 7.14 (d,
J = 8.1 Hz, 1H), 7.73 (d, J = 15.6 Hz, 1H), 8.32 (d, J = 8.1 Hz, 1H),
8.43 (d, J = 7.2 Hz, 1H), 8.50 (d, J = 8.4 Hz, 1H), 11.81 (s, 1H).
ever, almost all probes detecting fluoride only by the changes in
fluorescence intensity and fluoride concentration [21] are easy to
be disturbed in the quantitative detection by many factors such
as variabilities in excitation and emission efficiency; sample envi-
ronments and probe distribution. Due to the remarkable character-
istic in eliminating most or all ambiguities by self-calibration of
two emission bands [22], ratiometric measurement is one of the
best choices to detect fluoride ion. In this paper, we describe the
design and synthesis of a novel ratiometric fluorescent chemodos-
imeter 5 based on the internal change transfer (ICT) mechanism.
Recently, Zhu and co-workers demonstrated in detail a novel ratio-
metric fluorescent probe for palladium species with an obvious
feature of blue-to-green emission color change [23]. They chose
Synthesis of probe 5
A mixture of compound 4 (0.5 g, 1.86 mmol), tert-Butyldiphe-
nylchlorosilane (0.68 g, 2.2 mmol), imidazole (0.163 g, 2.4 mmol)
3
in 10 mL dry CHCl were stirred overnight at room temperature.
Removing the solvent under the vacuum condition at the end of
the reaction. The raw product was purified by column chromatog-
1
raphy. Compound 5 was obtained as yellow solid in 82% yield. H
NMR (300 MHz, CDCl
3
) 0.94 (t, J = 14.7 Hz, 3H), 1.20–1.24 (m,
9
6
8
1
3
1
1
5
H), 1.37–1.49 (m, 2H), 1.65–1.70 (m, 2H), 4.13 (t, J = 15 Hz, 2H),
4
-hydroxy-1,8-naphthalimide as the fluorophore because of its
.61 (d, J = 8.4 Hz, 1H), 7.71–7.80 (m, 5H), 7.35–7.48 (m, 6H),
.15 (d, J = 8.1 Hz, 1H), 8.63 (d, J = 7.2 Hz, 1H), 8.76 (d, J = 8.4 Hz,
desirable spectral performances and outstanding ICT structure.
This strategy inspired us to design ratiometric fluorescent probes
based on 4-hydroxy-1,8-naphthalimide (Scheme 1, 4) to detect
fluoride. As illustrated in Scheme 2 (see ESI), a silyl ether was intro-
1
3
3
H), C NMR (300 MHz, CDCl ) 13.82, 19.73, 20.38, 26.50, 29.68,
0.25, 40.06, 114.46, 115.52, 122.81, 125.47, 126.06, 128.17,
28.83, 130.53, 131.07, 131.49, 132.79, 135.29, 157.40, 163.85,
À
32 3
C H33NO
Si [M+H]+
duced as the reaction site for F [24,25], because of the high affinity
64.55. MS (ESI positive) calcd. for
08.2308, found 508.2312. Detailed procedures are described in
À
À
of F for silicon, with the reaction of F with 5, the Si–O band
would be break and as a result compound 4, 4-hydroxy-1,8-naph-
thalimide would be released, with longer wavelength fluorescence
owing to the stronger electron-donor ability of oxygen anion.
Scheme 1 and characterizations are shown in ESI.
.
Method
Experimental
À
À
À
À
2À
Stock solutions (10 mM) of the anions of F , Cl , Br , I , SO
,
4
À
2À
2À
2
4 4
H PO ; HPO and CO3 were prepared in ultra-pure water. Stock
Materials
solutions of chemodosimeter 1 (1 mM) were prepared in DMSO.
Test solutions were prepared by diluting stock solution by DMSO
and buffer solution (9:1, v/v). When test the spectrum properties,
placing 3 mL of the chemodosimeter test solution into a test tube
and adding an appropriate each ion test solution. The fluorescence
spectra were obtained 6 h after various analytes addition at room
temperature (other than time-dependent experiments) by excita-
tion at 413 nm. The excitation and emission slit widths were 3 nm.
Potassium fluoride dihydrate was supplied by shanghai jingc-
hun reagent Co., Ltd., with mass fraction purity of 98% and used
without further purification. Organic solvents purchased from
shanghai lingfeng chemical reagent Co., Ltd. were all analytical re-
agent grade. Water used in experiment was double distilled water.
All other inorganic salt used in this work were of analytical reagent
grade and used without purification.
Instrumental analysis
The UV–vis spectum measurements were performed with a
UV–vis spectrophotometer (Unico UV-2800H) equipped with
1
.0 cm quartz cells. Fluorescence was recorded on a spectrofluo-
rimeter (Shimadzu RF-5301PC) equipped with 1.0 cm quartz cell.
Synthesis of probe
Synthesis of compound 2 (4-bromo-N-butyl-1,8-naphthalic
anhydride)
4
-Bromo-1,8-naphthalic anhydride (10 g, 36 mmol) and 1-ami-
nobutane (3.7 g, 50.7 mmol) were added to 40 mL acetic acid. After
stirring and refluxing in a nitrogen atmosphere for 5 h, the reaction
mixture was cooled to room temperature and poured into a mix-
ture of ice and water (200 mL) then yellow solid was precipitated.
The mixed solution was filtered and recrystallized from ethanol to
give 8.6 g light gray needles in a yield of 72%.
Scheme 1. synthesis of fluorescent probe.