Novel coumarin fluorescent dyes: Synthesis, structural characterization and recognition behavior towards Cu(II) and Ni(II)

Article abstract of DOI:10.1016/j.dyepig.2011.05.011

A series of novel coumarin dyes (3-12) were designed and synthesized. The structures of the dyes were characterized by IR, ¹H NMR, ¹³C NMR, ¹⁹F NMR, MS and single crystal X-ray diffraction. 3-(2-Benzoylhydrazonotrifluoroethyl)-7-(N,N-diethylamino)coumarin (11) could recognize Cu²⁺ and Ni²⁺ selectively in aqueous solution. Upon addition of Cu²⁺ or Ni²⁺ to 11 a blue shift or a bathochromatic shift of the absorption band was observed while the emission band blue-shifted with decrease in the fluorescence intensity. Upon addition of Cu²⁺ the color of the solution of 11 changed from orange to red. The results showed that 11 could be used as an optical chemosensor of Cu ²⁺ and Ni²⁺.

Full text of DOI:10.1016/j.dyepig.2011.05.011

Dyes and Pigments 91 (2011) 309e316
Contents lists available at ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Novel coumarin fluorescent dyes: Synthesis, structural characterization
and recognition behavior towards Cu(II) and Ni(II)
*
Hongqi Li , Li Cai, Jinxing Li, Yixin Hu, Pingping Zhou, Jiming Zhang
Key Laboratory of Science & Technology of Eco-Textile, Ministry of Education, College of Chemistry, Chemical Engineering and Biotechnology,
Donghua University, Shanghai 201620, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of novel coumarin dyes (3e12) were designed and synthesized. The structures of the dyes were
characterized by IR, 1H NMR, 13C NMR, 19F NMR, MS and single crystal X-ray diffraction. 3-(2-
Benzoylhydrazonotrifluoroethyl)-7-(N,N-diethylamino)coumarin (11) could recognize Cu2þ and Ni2þ
selectively in aqueous solution. Upon addition of Cu2þ or Ni2þ to 11 a blue shift or a bathochromatic shift
of the absorption band was observed while the emission band blue-shifted with decrease in the fluo-
rescence intensity. Upon addition of Cu2þ the color of the solution of 11 changed from orange to red. The
Received 23 March 2011
Received in revised form
6 May 2011
Accepted 13 May 2011
Available online 27 May 2011
results showed that 11 could be used as an optical chemosensor of Cu2þ and Ni2þ
.
Keywords:
Fluorescent
Coumarin
Dye
Ó 2011 Elsevier Ltd. All rights reserved.
Recognition
Cu(II) ion
Ni(II) ion
1. Introduction
coumarin dyes. Herein we report the synthesis, structural charac-
terization and recognition behavior towards metal ions of the dyes.
Coumarins have been widely used in the fields of biology, medi-
cine, perfumes, cosmetics, and fluorescent dyes [1e3]. The structure
of benzopyrone has many advantages including high fluorescence
quantum yield, large Stokes shift, excellent light stability, and low
toxicity [4e6]. Coumarin derivatives have been used as fluorescent
probes of pH [7,8], for detection of nitric oxide [9], nitroxide [10], and
hydrogen peroxide [11,12]. Moreover, coumarin derivatives have
served as good chemosensors of anions including cyanide [13e16],
fluoride [17], pyrophosphate [18], acetate, benzoate, and dihy-
drogenphosphate [19] as well as various metal ions comprised of
Cu(II) [20e22], Zn(II) [23,24], Ni(II) [25], Hg(II) [26e28], Pb(II) [29],
Mg(II) [30], Fe(III) [31], and Ag(I) [32,33]. Several systems containing
coumarin exhibited simultaneous sensitivity towards two or three
different metal ions, e.g. Ca(II) and Mg(II) [34], Ni(II) and Co(II) [35],
Cu(II) and Hg(II) [36], Cu(II)/Ni(II)/Cd(II) [37], Zn(II)/Cd(II)/Pb(II) [38],
or Ni(II)/Pd(II)/Ag(I) [39].
2. Experimental section
2.1. Materials and instruments
All chemicals and solvents employed in this study were of
analytical grade and were used as received unless other statements.
Benzoylhydrazine and 4,4,4-trifluoroacetoacetate were obtained
from Bangcheng Chemicals Co. Ltd (China). Other chemicals were
purchased from Sinopharm Chemical Reagent Co. Ltd. Melting
points were determined on a WRS-2A capillary melting apparatus
and the quoted temperatures were uncorrected. 1H NMR, 13C NMR
and 19F NMR spectra were recorded on a Bruker AM 400 spec-
trometer. CDCl3 was used as solvent and chemical shifts recorded
were internally referenced to Me4Si (0 ppm). IR spectra were
obtained on a Thermo Electron Corporation Nicolet 380 FT-IR
spectrophotometer. Mass spectra were obtained on an Agilent
6000 LCeMS instrument (ESI, pos mode, 70e1000 amu). Fluores-
cence spectra were recorded on a Hitachi F-4500 spectrofluorom-
eter. UVeVis spectra were recorded on a JASCO V530 spectrometer.
X-Ray crystal strcture was measured on a Bruker Smart CCD
diffractometer by using Mo Ka radiation at 293 K.
In continuation to our interest in study on fluorescent coumarin
dyes [40], we have designed and synthesized a series of novel
* Corresponding author. Tel.: þ86 21 67792594; fax: þ86 21 67792608.
E-mail address: hongqili@dhu.edu.cn (H. Li).
0143-7208/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2011.05.011

310
H. Li et al. / Dyes and Pigments 91 (2011) 309e316
2.2. Synthesis of compound 1
132.94 (PheC), 136.15 (PheC), 140.36 (PheC), 146.70 (]CeNH),
152.51 (]CeN), 154.76 (q, C]N, J ¼ 31 Hz), 157.69 (]CeO), 158.15
A mixture of 4-diethylaminosalicylaldehyde (1.93 g, 10 mmol),
ethyl trifluoroacetoacetate (2.02 g, 11 mmol) and piperidine (4 mg,
0.05 mmol) in EtOH (50 mL) was refluxed for 5 h. After evaporation
to remove solvent, the resulted solid was washed with water and
purified by column chromatography on silica gel (petroleum ether/
ethyl acetate, 70:1, v/v) to give 1a (3.3 g, 92%) as lemon yellow solid.
Mp 92e93 ꢀC. IR (KBr): 3442, 2982, 1673, 1605, 1524, 1222, 1197,
(OeC]O). 19F NMR (376 MHz, CDCl3):
(ESI): m/z 449.2 (Mþ þ 1).
d
¼ ꢁ66.13 (s, 3F, CF3). MS
2.4.2. 3-(4-Methoxyphenylhydrazonotrifluoroethyl)-7-
(N,N-diethylamino)coumarin (4)
Obtained as orangeered acicular crystal from 2a and 4-
methoxyphenylhydrazine hydrochloride in 76% yield. Mp:
1174, 1099 cmꢁ1
.
1H NMR (400 MHz, CDCl3):
d
¼ 1.19 (t, 6H,
154e156 ꢀC. IR (KBr)
n
¼ 3367, 2989, 1688, 1582, 1458, 1236, 1142,
J ¼ 7.2 Hz, CH3), 1.37 (t, 3H, J ¼ 7.2 Hz, CH3), 3.32e3.44 (m, 4H, CH2),
4.32 (q, 2H, J ¼ 7.2 Hz, CH2), 6.27 (s, 1H, CH), 6.30 (d, 1H, J ¼ 2.4 Hz,
CH), 7.04 (d, 1H, J ¼ 8.4 Hz, CH), 7.70 (s, 1H, CH), 7.73 (s, 1H, OH). 13C
1051, 1027 cmꢁ1
;
1H NMR (400 MHz, CDCl3):
d
¼ 1.25 (t, 6H, CH3,
J ¼ 7.2 Hz), 3.47 (q, 4H, CH2, J ¼ 7.2 Hz), 3.93 (s, 3H, OCH3), 6.54 (d,1H,
CH, J ¼ 2.4 Hz), 6.66 (dd,1H, CH, J ¼ 2.4 and 8.8 Hz), 6.84 (dd, 2H, CH,
J ¼ 2.0 and 6.8 Hz), 7.09 (dd, 2H, CH, J ¼ 2.0 and 6.8 Hz), 7.35 (d,1H, CH,
J ¼ 8.8 Hz), 7.82 (s, 1H, CH), 8.27 (s, 1H, NH). 13C NMR (CDCl3,
NMR (100 MHz, CDCl3):
d
¼ 12.57 (CH3), 14.19 (CH3), 44.77 (NCH2),
61.51 (OCH2), 95.61 (PheC), 95.95 (PheC), 97.32 (PheC), 106.10
(PheC), 106.35 (PheC), 106.73 (PheC), 131.10 (CF3), 140.01 (PheC),
152.64 (]CeN), 155.10 (CeOH), 167.65 (C]O); 19F NMR (376 MHz,
100 MHz):
d
¼ 12.41 (CH3), 45.10 (CH2), 55.63 (OCH3), 96.94 (PheC),
107.71 (PheC), 109.86 (PheC), 114.58 (PheC), 115.27 (PheC), 123.37
(q, CF3, J ¼ 266.6 Hz), 128.33 (PheC), 130.26 (PheC), 137.52 (PheC),
146.29 (]CeNH), 152.17 (]CeN), 155.10 (]CeOCH3), 155.86 (q, C]
N, J ¼ 31.8 Hz), 157.24 (]CeO), 159.51 (OeC]O). 19F NMR (376 MHz,
CDCl3):
d
¼ ꢁ87.40 (s, 3F, CF3). MS (ESI): m/z 360.2 (Mþ þ 1).
Compound 1b was obtained by the above-mentioned procedure
as colorless block crystal in 82% yield. Mp: 87e89 ꢀC. IR (KBr)
n
¼ 3447, 1684, 1625, 1572, 1454, 1184, 1168, 1155, 1090, 1020 cmꢁ1
;
CDCl3):
d
¼ ꢁ64.25 (s, 3F, CF3). MS (ESI): m/z 434.2 (Mþ þ 1).
MS (ESI): m/z 311.1 (Mþ þ 23).
2.3. Synthesis of compound 2
2.4.3. 3-(4-Bromophenylhydrazonotrifluoroethyl)-7-
(N,N-diethylamino)coumarin (5)
Obtained as yellow solid from 2a and 4-bromophenylhydrazine
A mixture of chromene 1a (1.80 g, 5 mmol) and TsOH$H2O
(10 mg, 0.05 mmol) in chlorobenzene (50 mL) was refluxed for 4 h.
After evaporation to remove solvent, the residue was purified by
column chromatography on silica gel (petroleum ether/ethyl
acetate, 20:1, v/v) to give 2a (1.42 g, 91%) as yellow solid. Mp
125e127 ꢀC. IR (KBr): 3435, 2986, 1736, 1675, 1619, 1566, 1152, 1176,
hydrochloride in 92% yield. Mp: 162e164 ꢀC. IR (KBr)
n
¼ 3446,
1736, 1654, 1623, 1560, 1454, 1250, 1184,1135, 1099, 1057 cmꢁ1. 1H
NMR (400 MHz, CDCl3):
d
¼ 1.26 (t, 6H, CH3, J ¼ 7.2 Hz), 3.47 (q, 4H,
CH2, J ¼ 7.2 Hz), 6.52 (d, 1H, CH, J ¼ 2.4 Hz), 6.67 (dd, 1H, CH, J ¼ 2.4
and 8.8 Hz), 7.03e7.06 (m, 2H, CH), 7.34e7.38 (m, 3H, CH), 7.84 (s,1H,
CH), 8.47 (s, 1H, NH). 13C NMR (CDCl3, 100 MHz):
d
¼ 12.42 (CH3),
1136, 1082 cmꢁ1
.
1H NMR (400 MHz, CDCl3):
d
¼ 1.26 (t, 6H,
45.17 (CH2), 96.93 (PheC), 107.66 (PheC), 110.05 (PheC), 115.69
(PheC), 120.39 (q, CF3, J ¼ 278.7 Hz), 128.56 (PheC), 130.44 (PheC),
132.06 (PheC), 133.26 (PheC), 142.76 (]CeNH), 146.43 (]CeN),
152.36 (]CeOCH3), 154.43 (q, C]N, J ¼ 41.7 Hz), 157.31 (]CeO),
J ¼ 7.2 Hz, CH3), 3.50 (q, 4H, J ¼ 7.2 Hz, CH2), 6.47 (d, 1H, J ¼ 2.4 Hz,
CH), 6.66 (dd, 1H, J ¼ 2.4 and 9.2 Hz, CH), 7.41 (d, 1H, J ¼ 9.2 Hz, CH),
8.38 (s, 1H, CH). 13C NMR (100 MHz, CDCl3):
d
¼ 12.47 (CH3), 45.48
(CH2), 96.80 (PheC), 108.02 (PheC), 109.37 (PheC), 110.52 (PheC),
132.65 (CF3), 150.56 (PheC), 150.58 (PheC), 154.54 (PheC), 157.37
(]CeN), 159.31 (OC]O), 178.47 (C]O). 19F NMR (376 MHz, CDCl3):
159.61 (OeC]O). 19F NMR (376 MHz, CDCl3):
MS (ESI): m/z 484.2 (Mþ þ 1).
d
¼ ꢁ64.44 (s, 3F, CF3).
d
¼ ꢁ72.47 (s, 3F, CF3). MS (ESI): m/z 314.1 (Mþ þ 1).
2.4.4. 3-(4-Fluorophenylhydrazonotrifluoroethyl)-7-
(N,N-diethylamino)coumarin (6)
Compound 2b was obtained similarly as pale grayish yellow
solid in 88% yield. Mp: 95e96 ꢀC. IR (KBr)
n
¼ 3447,1684,1647,1568,
Obtained as yellow solid from 2a and 4-fluorophenylhydrazine
1454, 1184, 1168, 1152, 1017 cmꢁ1; MS (ESI): m/z 243.1 (Mþ þ 1).
2.4. General synthesis of the target compounds (3e10)
hydrochloride in 95% yield. Mp: 148e150 ꢀC. IR (KBr)
n
¼ 3446,
2982, 1696, 1624, 1518, 1418, 1294, 1180, 1133, 1094 cmꢁ1. 1H NMR
(400 MHz, CDCl3):
d
¼ 1.25 (t, 6H, CH3, J ¼ 7.2 Hz), 3.47 (q, 4H, CH2,
J ¼ 7.2 Hz), 6.53 (d, 1H, CH, J ¼ 2.0 Hz), 6.67 (dd, 1H, CH, J ¼ 2.0 and
8.8 Hz), 6.96e7.00 (m, 2H, CH), 7.09e7.12 (m, 2H, CH), 7.36 (d, 1H,
CH, J ¼ 8.8 Hz), 7.84 (s, 1H, CH), 8.40 (s, 1H, NH). 13C NMR (CDCl3,
Phenylhydrazine hydrochloride compound (1 mmol), compound
2a (1 mmol) and TsOH$H2O (1 mg, 0.005 mmol) were mixed in
chlorobenzene (20 mL) and then heated to reflux. Reactions were
usually completed within 0.5e4 h. The solvent was removed by
evaporation and the residue was purified bycolumn chromatography
on silica gel (petroleum ether/ ethyl acetate, 10:1, v/v).
100 MHz):
d
¼ 12.41 (CH3), 45.13 (CH2), 96.88 (PheC), 107.14
(PheC), 107.63 (PheC), 109.96 (PheC), 115.15 (PheC), 115.90
(PheC), 117.20 (PheC), 120.55 (q, CF3, J ¼ 271.2 Hz), 123.15 (PheC),
129.15 (PheC), 130.38 (PheC), 139.90 (PheC), 146.36 (]CeNH),
152.28 (]CeN), 155.31 (q, C]N, J ¼ 40.5 Hz), 157.27 (]CeO),
2.4.1. 3-(2-Nitrophenylhydrazonotrifluoroethyl)-7-
(N,N-diethylamino)coumarin (3)
159.59 (C]O). 19F NMR (376 MHz, CDCl3):
d
¼ ꢁ64.37 (s, 3F, CF3),
ꢁ62.76 (s, 1F, PheF). MS (ESI): m/z 422.2 (Mþ þ 1).
Obtained as brick red acicular crystal from 2a and 2-
nitrophenylhydrazine hydrochloride in 92% yield. Mp: 144e146 ꢀC.
2.4.5. 3-(4-Methylphenylhydrazonotrifluoroethyl)-7-
(N,N-diethylamino)coumarin (7)
IR (KBr)
n
¼ 3318, 3093, 2987, 2940, 2912,1742,1610,1584,1450,1500,
1333, 1197, 1174, 1099, 1146, 1047 cmꢁ1. 1H NMR (400 MHz, CDCl3):
Obtained as yellow solid from 2a and 4-methylphenylhydrazine
d
¼ 1.26 (t, 6H, CH3, J ¼ 7.2 Hz), 3.48 (q, 4H, CH2, J ¼ 7.2 Hz), 6.56 (d,1H,
hydrochloride in 94% yield. Mp: 161e162 ꢀC. IR (KBr)
n
¼ 3446,
CH, J ¼ 2.4 Hz), 6.67 (dd,1H, CH, J ¼ 2.4 and 8.8 Hz), 6.96e6.99 (m,1H,
CH), 7.35 (d, 1H, CH, J ¼ 8.8 Hz), 7.61 (m, 1H, CH), 7.83 (s, 1H, CH),
7.97e8.00 (m, 1H, CH), 8.14e8.16 (m, 1H, CH), 11.07 (s, 1H, NH). 13C
1695, 1623, 1518, 1457, 1244, 1178, 1133, 1105 cmꢁ1
(400 MHz, CDCl3):
.
1H NMR
d
¼ 1.25 (t, 6H, CH3, J ¼ 7.2 Hz), 2.29 (s, 3H, CH3),
3.47 (q, 4H, CH2, J ¼ 7.2 Hz), 6.53 (d, 1H, CH, J ¼ 2.4 Hz), 6.67 (dd, 1H,
CH, J ¼ 2.4 and 8.8 Hz), 7.04 (d, 2H, CH, J ¼ 8.6 Hz), 7.08 (d, 2H, CH,
J ¼ 8.6 Hz), 7.35 (d, 1H, CH, J ¼ 8.8 Hz), 7.82 (s, 1H, CH), 8.29 (s, 1H,
NMR (CDCl3, 100 MHz):
106.05 (PheC), 107.37 (PheC), 109.73 (PheC), 116.60 (PheC), 120.47
(PheC), 121.39 (q, CF3, J ¼ 263.7 Hz), 125.81 (PheC), 130.31 (PheC),
d
¼ 12.47 (CH3), 45.17 (CH2), 97.34 (PheC),
NH). 13C NMR (CDCl3, 100 MHz):
d
¼ 12.41 (CH3), 45.13 (CH2), 96.92

H. Li et al. / Dyes and Pigments 91 (2011) 309e316
311
(PheC), 107.32 (PheC), 107.66 (PheC), 109.82 (PheC), 114.00
(PheC), 123.32 (PheC), 126.75 (q, CF3, J ¼ 201.9 Hz), 129.68 (PheC),
130.27 (PheC), 131.37 (PheC), 136.36 (PheC), 141.22 (PheC), 146.34
(]CeNH), 152.16 (]CeN), 154.49 (q, C]N, J ¼ 24 Hz), 157.25 (]
(20 mL) was refluxed for 2 h. The solvent was removed by evapora-
tion and the residue was purified by column chromatography on
silica gel (petroleum ether/ethyl acetate, 10:1, v/v) to give 11 (0.42 g,
97%) as golden solid. Mp 148e150 ꢀC. IR (KBr): 3446,1707,1654,1617,
1584, 1450, 1262, 1176, 1135, 1078 cmꢁ1. 1H NMR (400 MHz, CDCl3):
CeO), 159.46 (C]O). 19F NMR (376 MHz, CDCl3):
CF3). MS (ESI): m/z 418.3 (Mþ þ 1).
d
¼ ꢁ64.39 (s, 3F,
d
¼ 1.26 (t, 6H, CH3, J ¼ 7.2 Hz), 3.48 (q, 4H, CH2, J ¼ 7.2 Hz), 6.55 (d,1H,
CH, J ¼ 2.4 Hz), 6.70 (dd, 1H, CH, J ¼ 2.4 and 9.2 Hz), 7.39 (d, 1H, CH,
J ¼ 9.2 Hz), 7.44e7.46 (m, 1H, CH), 7.48 (s, 1H, CH), 7.52e7.55 (m, 2H,
CH), 7.91e7.92 (m, 2H, CH), 7.94 (s, 1H, NH). 13C NMR (100 MHz,
2.4.6. 3-(2-Chlorophenylhydrazonotrifluoroethyl)-7-(N,N-
diethylamino)coumarin (8)
Obtained as orangeered columnar crystal from 2a and 2-
chlorophenylhydrazine hydrochloride in 96% yield. Mp:
CDCl3):
d
¼ 12.41 (CH3), 45.25 (CH2), 96.79e110.51 (PheC), 127.20
(CF3), 128.64e132.41 (PheC),146.97 (C]N),153.03 (OeC]O),157.55
150e152 ꢀC. IR (KBr)
n
¼ 3446, 1652, 1636, 1558, 1454, 1136,
(NeC]O). 19F NMR (376 MHz, CDCl3):
(ESI): m/z 432.3 (Mþ þ 1).
d
¼ ꢁ64.29 (s, 3F, CF3). MS
1127,1102, 1053 cmꢁ1. 1H NMR (400 MHz, CDCl3):
d
¼ 1.24 (t, 6H, CH3,
J ¼ 7.2 Hz), 3.46 (q, 4H, CH2, J ¼ 7.2 Hz), 6.54 (d, 1H, CH, J ¼ 2.4 Hz),
6.66 (dd,1H, CH, J ¼ 2.4 and 8.8 Hz), 6.88e6.90 (m,1H, CH), 7.24e7.27
(m, 2H, CH), 7.36 (d,1H, CH, J ¼ 8.8 Hz), 7.61e7.63 (m,1H, CH), 8.86 (s,
2.6. Synthesis of 3-(2-hydroxyphenyliminotrifluoroethyl)-7-
(N,N-diethylamino)coumarin (12)
1H, CH), 8.82 (s, 1H, NH). 13C NMR (CDCl3, 100 MHz):
d
¼ 12.41 (CH3),
45.11 (CH2), 96.99 (PheC), 106.73 (PheC), 107.56 (PheC), 109.94
(PheC), 115.19 (PheC), 118.84 (PheC), 120.28 (q, CF3, J ¼ 283.6 Hz),
122.03 (PheC), 127.85 (PheC), 128.10 (q, C]N, J ¼ 34.4 Hz), 129.14
(PheC), 130.42 (PheC), 139.71 (PheC), 146.33 (]CeNH), 152.40 (]
CeN), 157.38 (]CeO), 159.07 (C]O). 19F NMR (376 MHz, CDCl3):
A mixture consisting of 2a (0.31 g, 1 mmol), 2-aminophenol
(0.11 g, 1 mmol) and TsOH$H2O (1 mg, 0.005 mmol) in chloroben-
zene (20 mL) was refluxed for 6 h. The solvent was removed by
evaporation and the residue was purified by column chromatog-
raphy on silica gel (petroleum ether/ethyl acetate, 10:1, v/v) to give
12 (0.38 g, 94%) as greenish-yellow crystal. Mp: 145e146 ꢀC. IR
d
¼ ꢁ64.62 (s, 3F, CF3). MS (ESI): m/z 438.2 (Mþ þ 1).
(KBr)
n
¼ 3446, 2974, 1697, 1620, 1593, 1486, 1250, 1188, 1168,
1082 cmꢁ1. 1H NMR (400 MHz, CDCl3):
d
¼ 1.20e1.24 (m, 6H, CH3),
2.4.7. 3-(3-Chlorophenylhydrazonotrifluoroethyl)-7-(N,N-
diethylamino)coumarin (9)
3.41e3.46 (m, 4H, CH2), 6.49e6.51 (m, 1H, CH), 6.62e6.64 (m, 2H,
CH), 6.74e6.76 (m, 2H, CH), 6.81 (s, 1H, CH), 6.82e6.83 (m, 1H, CH),
7.35e7.38 (m, 1H, CH), 8.06 (s, 1H, OH). 13C NMR (CDCl3, 100 MHz):
Obtained as orange acicular crystal from 2a and 3-chloro-
phenylhydrazine hydrochloride in 88% yield. Mp: 186e187 ꢀC. IR
(KBr)
n
¼ 3446, 3282, 2974, 2925, 1694, 1598, 1516, 1418, 1244, 1175,
d
¼ 12.39 (CH3), 45.00 (CH2), 96.83 (PheC), 107.77 (PheC), 108.28
1134, 1060 cmꢁ1. 1H NMR (400 MHz, CDCl3):
d
¼ 1.26 (t, 6H, CH3,
(PheC),109.65 (PheC),110.16 (PheC),112.17 (PheC),120.33 (PheC),
122.45 (PheC), 124.03 (q, CF3, J ¼ 272.8 Hz), 130.16 (PheC), 144.72
(PheC), 146.41 (q, C]N, J ¼ 95.3 Hz), 148.28 (]CeN), 151.95 (]
CeO), 156.90 (CeOH), 160.71 (OeC¼O). 19F NMR (376 MHz, CDCl3):
J ¼ 7.2 Hz), 3.48 (q, 4H, CH2, J ¼ 7.2 Hz), 4.48 (s, 1H, NH), 6.55 (d, 1H,
CH, J ¼ 2.4 Hz), 6.68 (dd, 1H, CH, J ¼ 2.4 and 9.2 Hz), 6.90e6.93 (m,
1H, CH), 6.97e7.00 (m, 1H, CH), 7.16e7.18 (m, 1H, CH), 7.20e7.22 (m,
1H, CH), 7.37 (d, 1H, CH, J ¼ 9.2 Hz), 7.85 (s, 1H, CH). 13C NMR (CDCl3,
d
¼ ꢁ84.75 (s, 3F, CF3). MS (ESI): m/z 405.2 (Mþ þ 1).
100 MHz):
d
¼ 12.41 (CH3), 45.16 (CH2), 96.93 (PheC), 106.99
(PheC), 107.63 (PheC), 110.05 (PheC), 112.29 (PheC), 114.22
(PheC), 121.91 (PheC), 123.12 (q, CF3, J ¼ 102 Hz), 126.76 (q, C]N,
J ¼ 22.8 Hz), 130.18 (PheC), 130.45 (PheC), 135.10 (PheC), 144.80
(PheC), 146.41 (]CeNH), 152.38 (]CeN), 157.32 (]CeO), 159.59
3. Results and discussion
3.1. Synthesis and structural characterization of coumarins 3e12
(C]O). 19F NMR (376 MHz, CDCl3):
d
¼ ꢁ64.41 (s, 3F, CF3). MS (ESI):
The novel coumarin dyes 3e12 were synthesized by a three-step
protocol, as shown in Scheme 1 and Scheme 2. Knoevenagel
condensation between 4-diethylaminosalicylaldehyde and ethyl
trifluoroacetoacetate catalyzed by piperidine (5 mol%) in ethanol
for 5 h did not produce trifluoroacetylcoumarin 2a directly. Instead
2-hydroxyl-2-trifluoromethyl-3-ethoxycarbonyl-7-(N,N-dieth-
ylamino)-2H-1-chromene (1a) was obtained in 92% yield, which
upon treatment with TsOH$H2O (2 mol%) in chlorobenzene to
afford coumarin 2a in 91% yield. Compound 1b and 2b were
prepared similarly and the results were in good accordance with
m/z 437.11 (Mþ).
2.4.8. 3-(2,4-Dimethylphenylhydrazonotrifluoroethyl)-7-
(N,N-diethylamino)coumarin (10)
Obtained as yellow solid from 2a and 2,4-dimethylphenyl-
hydrazine hydrochloride in 88% yield. Mp: 159e160 ꢀC. IR (KBr)
n
¼ 3448,1701,1623,1521,1454,1254,1160,1139,1061 cmꢁ1.1H NMR
(400 MHz, CDCl3):
d
¼ 1.25 (t, 6H, CH3, J ¼ 7.2 Hz), 2.19 (s, 3H, CH3),
2.23 (s, 3H, CH3), 3.47 (q, 4H, CH2, J ¼ 7.2 Hz), 6.55 (d, 1H, CH,
J ¼ 2.4 Hz), 6.68 (dd, 1H, CH, J ¼ 2.4 and 8.8 Hz), 6.88 (dd, 1H,
CH, J ¼ 2.0 and 8.0 Hz), 6.96 (d, 1H, CH, J ¼ 2.0 Hz), 7.02 (d, 1H, CH,
J ¼ 8.0 Hz), 7.35 (d, 1H, CH, J ¼ 8.8 Hz), 7.81 (s, 1H, CH), 8.23 (s, 1H,
O
NH). 13C NMR (CDCl3, 100 MHz):
d
¼ 12.41 (CH3), 19.03 (CH3), 19.96
CHO
O
O
OEt
CF3
N
H
(CH3), 45.10 (CH2), 96.93 (PheC), 107.68 (PheC), 109.81 (PheC),
111.43 (PheC), 115.39 (PheC), 123.51 (q, CF3, J ¼ 108.5 Hz), 124.07
(PheC),127.74 (PheC),130.25 (PheC),137.45 (PheC),138.82 (PheC),
141.46 (PheC), 146.35 (]CeNH), 152.14 (]CeN), 155.60 (q, C]N,
J ¼ 24.9 Hz), 157.26 (]CeO), 159.45 (C]O). 19F NMR (376 MHz,
+
F3C
OEt
R
O
R
OH
OH
1a: R = NEt2, 92%
1b: R = H, 82%
¼ ꢁ64.33 (s, 3F, CF3). MS (ESI): m/z 432.3 (Mþ þ 1).
O
O
CDCl3):
d
CF3
TsOH
2.5. Synthesis of 3-(2-benzoylhydrazonotrifluoroethyl)-7-(N,N-
diethylamino)coumarin (11)
R
O
2a: R = NEt2, 91%
2b: R = H, 88%
A mixture consisting of 2a (0.31 g,1 mmol), benzhydrazide (0.14 g,
1 mmol) and TsOH$H2O (1 mg, 0.005 mmol) in chlorobenzene
Scheme 1. Synthesis of coumarins 2.

312
H. Li et al. / Dyes and Pigments 91 (2011) 309e316
O
O
CF3
CF3
N
R
RNH2
Et2N
O
Et2N
O
O
2a
3-12
NH
NH
NH
NH
F
NH
NO2
R =
OMe
Br
Me
3 (92%)
4 (76%)
5 (92%)
6 (95%)
7 (94%)
NH
NH
NH
NH
Cl
Me
OH
O
Cl
Me
9 (88%)
8 (96%)
10 (88%)
11 (97%)
12 (94%)
Scheme 2. Synthesis of the coumarin dyes 3e12.
those reported in the literature [41]. Finally, the novel coumarin
dyes (3e12) were prepared from coumarin 2a and compounds
containing an amino group with chlorobenzene as the solvent in
good to excellent yields.
The chemical structures of coumarin 3e12 were fully charac-
terized by 1H NMR, 13C NMR, 19F NMR, IR and mass spectrum. All of
the data in the spectra were in good accordance with the structures.
Single crystals of coumarin 3 suitable for X-ray crystal diffraction
measurement were obtained by slow evaporation of a solution of 3
in 1:1 petroleum ether and ethyl acetate. X-Ray data for crystals of 3
were collected by graphite-monochromatized Mo Ka radiation at
293 K and the crystal data and experimental details for compound 3
were summarized in Table 1. The structure was solved by direct
methods and refined by full-matrix least-squares with anisotropic
temperature factors for the non-hydrogen atoms. The hydrogen
atoms bonded to the carbon atoms were assigned based on the
expected bonding geometry. The hydrogen atoms were refined iso-
tropically in the final least-squares cycles.
The crystal structure and molecular packing of coumarin 3 were
showed in Fig. 1 and Fig. 2, respectively. It can be seen that the
benzopyrone skeleton in the molecule is essentially planar. The
molecule adopts a trans configuration about both the central C]C
olefinic bond and the C]N imine bond. Molecules of compound 3
are packed in a face-to-face arrangement and form a layered stack.
CCDC-824461 contains the supplementary crystallographic data for
this paper. These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/data_request/cif.
Table 1
Crystal data and experimental details for coumarin 3.
3.2. UVeVis absorption spectra of the novel compounds
Empirical formula
Formula weight
C21H18F3 N4O4
447.39
Temperature
Wavelength
Crystal system, space group
Unit cell dimensions
293 (2) K
0.71073 Å
Orthorhombic, P2 (1)2 (1)2 (1)
a ¼ 7.942 (4) Å,
UVeVis absorption spectra of compounds 1a, 2a, 9, 11 and 12 in
EtOH were measured and showed in Fig. 3. The maximum absorption
a
¼ 90ꢀ
b ¼ 12.473 (6) Å,
c ¼ 20.670 (9) Å,
2047.7 (16) Å3
4, 1.451 mg/m3
0.120 mmꢁ1
924
b
¼ 90ꢀ
¼ 90ꢀ
g
Volume
Z, Calculated density
Absorption coefficient
F (000)
Crystal size
Theta range for data collection
Limiting indices
0.12 ꢂ 0.10 ꢂ 0.08 mm
2.56e25.00ꢀ
ꢁ9 <¼ h <¼ 9, ꢁ12 <¼ k <¼ 14,
ꢁ24 <¼ l <¼ 15
9627/3615 [R (int) ¼ 0.0746]
99.9%
Reflections collected/unique
Completeness to
Absorption correction
Max. and min. transmission
Refinement method
q
¼ 26.00
None
0.9904 and 0.9857
Full-matrix least-squares on F2
3615/0/292
Data/restraints/parameters
Goodness-of-fit on F2
1.004
Final R indices [I > 2
R indices (all data)
Absolute structure parameter
Extinction coefficient
s
(I)]
R1 ¼ 0.0584, wR2 ¼ 0.1132
R1 ¼ 0.1135, wR2 ¼ 0.1386
0.8 (14)
0.0070 (13)
Largest diff. peak and hole
0.227 and ꢁ0.202 e.Åꢁ3
Fig. 1. Crystal structure of compound 3.

H. Li et al. / Dyes and Pigments 91 (2011) 309e316
313
Fig. 2. View of the molecular packing in coumarin 3.
wavelength of compounds 1a, 2a, 9,11 and 12 was 392, 398, 405, 413
and 399 nm, respectively. The remarkable bathochromatic shift of the
maximum absorption wavelengths of compounds 1a, 2a, 9,11 and 12
relative to the maximum absorption wavelength at 275 nm of
coumarin without substitution was attributed to the formation of the
pushepull system based on the electron-donating diethylamino
group and the electron-withdrawing trifluoroethyl substituent in the
compounds.
were showed in Fig. 4. It can be found that compound 1a and 2a
exhibited strong fluorescence intensity while coumarin 9, 11 and 12
showed relatively weak fluorescence intensity. The fluorescence
emission wavelengths of the new compounds were around 460 nm,
except for coumarin 11 undergoing a bathochromatic shift to
a wavelength of about 490 nm.
For the new compounds 1a, 2a, 9, 11 and 12, the fluorescence
quantum yield, which is defined as the ratio of the number of
photons of light emitted from a photoluminescent sample to those
absorbed by the sample and can be calculated by the following
equation for an unknown sample (Vu) was studied.
3.3. Emission spectra and fluorescence quantum yields
of the coumarins
Fluorescence emission spectra of compounds 1a, 2a, 9, 11 and 12
in EtOH were measured at an excitation wavelength of 370 nm and
Blank
1#
a
2#
3#
4#
5#
6#
7#
8#
9#
0.6
0.5
0.4
0.3
0.2
0.1
0
1
1a
0.8
2a
0.6
0.4
9
11
12
0.2
0
300
350
400
450
500
550
600
300
350
400
450
500
550
Wavelength (nm)
Wavelength(nm)
b
Blank
1#
2#
3#
4#
5#
6#
7#
8#
Fig. 3. UVeVis absorption spectra of 1a, 2a, 9, 11 and 12 in EtOH (20 uM).
4000
3500
3000
2500
2000
1500
1000
500
2000
1a
1500
1000
500
0
2a
9
9#
11
12
0
300 350 400 450 500 550 600 650 700
Wavelength (nm)
300 350 400 450 500 550 600 650 700
Fig. 5. Absorption (a) and emission (lex ¼ 411 nm) (b) spectra of 11 upon addition of
different metal ions (1 equiv to 11). Experimental conditions: 2 ꢂ 10ꢁ5 mol/L 11,
0.1 mol/L HEPES buffer in EtOH/H2O (9:1, v/v), pH ¼ 7.16. 1#: Mg2þ; 2#: Zn2þ; 3#:
Wavelength(nm)
Fig. 4. Emission (lex ¼ 370 nm) spectra of 1a, 2a, 9, 11 and 12 in EtOH (20 uM).
Ca2þ; 4#: Cu2þ; 5#: Ni2þ; 6#: Hg2þ; 7#: Co2þ; 8#: Fe3þ; 9#: Al3þ
.

314
H. Li et al. / Dyes and Pigments 91 (2011) 309e316
The maximum absorption wavelength of coumarin 11 was
Fu As
Fs
$ $
Fu
¼
505 nm and its maximum excitation and emission wavelength
were 411 and 492 nm, respectively. The addition of different metal
ions induced varied changes in both the absorption and emission
spectra of 11. Addition of Cu2þ or Ni2þ brought marked changes to
both the absorption and emission spectra of 11 while other metal
ions did not cause distinct change in the spectra of 11. Upon addi-
tion of Cu2þ to 11 the absorption peak blue-shifted from 420 nm to
373 nm and the emission band shifted from 492 nm to 471 nm with
decrease in the fluorescence intensity. In the case of Ni2þ, upon
addition of Ni2þ to 11 a bathochromatic shift of the absorption peak
from 420 nm to 478 nm was observed. Meanwhile the fluorescence
intensity decreased drastically. The color of 11 in EtOH/H2O (9:1,
v/v) was orange and after addition of Cu2þ the color of the solution
changed to red obviously. However, the color of the solution of 11
remained basically unchanged upon addition of other metal ions.
These results indicated that coumarin 11 showed effective selec-
Fs Au
wherein A is the absorbance at the excitation wavelength, F is the
area under the fluorescence curve and Vs is the quantum yield of
the standard. Subscripts s and x refer to the standard and sample,
respectively. The above data should be obtained under identical
conditions. In the study 9,10-diphenylanthracene was chosen as the
standard, with its fluorescence quantum yield Vs being 1.000.
Compound 1a and 2a had relatively high fluorescence quantum
yield of 0.194 and 0.269, respectively. Among the derivatives of
coumarin 2a, compound 11 afforded a relatively high fluorescence
quantum yield of 0.185 while coumarin 9 and 12 showed very low
fluorescence quantum yield of 0.009 and 0.023, respectively.
3.4. Spectroscopic recognition of coumarin 11 towards metal ions
tivity for Cu2þ and Ni2þ over other metal ions including Mg2þ, Zn2þ
Ca2þ, Hg2þ, Co2þ, Fe3þ and Al3þ
,
.
The recognition behavior of coumarin 11 towards various metal
ions was investigated. The fluorescence titration experiments were
performed in 0.1 mol/L HEPES buffer solution (EtOH/H2O ¼ 9:1, v/v,
pH ¼ 7.16) at an excitation wavelength of 411 nm. The slit of both
excitation and emission was 5.0 nm. The changes in the absorption
(a) and emission (b) spectra of coumarin 11 upon addition of equal
In order to further inquire into the spectral characteristics of
coumarin 11 upon addition of Cu2þ and Ni2þ, influences of the
amount of Cu2þ and Ni2þ (0.1e1 equivalent to L) on the absorption
and emission spectra of 11 were measured and showed in Fig. 6 and
Fig. 7, respectively. With the gradual addition of Cu2þ to 11, the
absorption band at 420 nm decreased gradually in intensity and
a new absorption peak at 373 nm was developed (Fig. 6a).
equivalent of different metal ions including Mg2þ, Zn2þ, Ca2þ, Cu2þ
Ni2þ, Hg2þ, Co2þ, Fe3þ and Al3þ were showed in Fig. 5.
,
2.5
a
2
1.5
0.6
0.5
0.4
0.3
0.2
0.1
0
1
0.5
0
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
1
2+
Equivalent of Cu
300
350
400
450
500
550
600
Wavelength (nm)
1.2
1.1
1
b
max
0.9
0.8
0.7
0.6
0.5
4000
3500
3000
2500
2000
1500
1000
500
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
1
2+
Equivalent of Cu
0
300
350
400
450
500
550
600
650
700
Wavelength (nm)
Fig. 6. Absorption (a) (inset: plot of absorbance ratio (372 nm/420 nm) versus equivalent of Cu2þ) and emission (lex ¼ 411 nm) (b) (inset: plot of fluorescence intensity ratio
(471 nm/492 nm) versus equivalent of Cu2þ) spectra of 11 upon addition of Cu2þ (0.1e1 equivalent to 11). Experimental conditions: 2 ꢂ 10ꢁ5 mol/L 11, 0.1 mol/L HEPES buffer in
EtOH/H2O (9:1, v/v), pH ¼ 7.16.

H. Li et al. / Dyes and Pigments 91 (2011) 309e316
315
a
0.6
0.5
0.4
0.3
0.2
0.1
0
300
350
400
450
500
550
600
Wavelength (nm)
b
4000
3000
2000
1000
0
300 350 400 450 500 550 600 650 700
Wavelength (nm)
Fig. 7. Absorption (a) (inset: plot of absorbance ratio (478 nm/420 nm) versus equivalent of Ni2þ) and emission (lex ¼ 411 nm) (b) (inset: plot of relative fluorescence intensity at
492 nm versus equivalent of Ni2þ) spectra of 11 upon addition of Ni2þ (0.1e1 equivalent to 11). Experimental conditions: 2 ꢂ 10ꢁ5 mol/L 11, 0.1 mol/L HEPES buffer in EtOH/H2O (9:1,
v/v), pH ¼ 7.16.
Meanwhile the maximum emission wavelength shifted from
492 nm to 471 nm gradually (Fig. 6b).
References
Remarkable influences of Ni2þ on the absorption and emission
spectra of 11 were also observed, as shown in Fig. 7a and b. The
gradual addition of Ni2þ to 11 resulted in significant fluorescence
quenching and a bathochromatic shift of the absorption peak from
420 nm to 478 nm. The interaction between 11 and Cu2þ or Ni2þ
enhanced the fluorescence quenching and the bonding between 11
and Cu2þ or Ni2þ and led to the changes in the absorption and
emission spectra. Therefore 11 could be used as an optical chemo-
sensor for Cu2þ and Ni2þ with high sensitivity.
[1] Starcevic S, Brozic P, Turk S, Cesar J, Lanisnik Rizner T, Gobec S. Synthesis and
biological evaluation of (6- and 7-phenyl) coumarin derivatives as selective
nonsteroidal inhibitors of 17-hydroxysteroid dehydrogenase type 1. J Med
Chem 2011;54:248e61.
[2] Lodeiro C, Lippolis V, Mameli M. From macrocyclic ligands to fluorescent
molecular sensors for metal ions: recent results and perspectives. Macrocyclic
Chem; 2010:159e212.
[3] Danko M, Szabo E, Hrdlovic P. Synthesis and spectral characteristics of fluo-
rescent dyes based on coumarin fluorophore and hindered amine stabilizer in
solution and polymer matrices. Dyes Pigm 2011;90:129e38.
[4] Zhou S, Jia J, Gao J, Han L, Li Y, Sheng W. The one-pot synthesis and fluori-
metric study of 3-(20-benzothiazolyl)coumarins. Dyes Pigm 2010;86:123e8.
[5] Sato S, Suzuki M, Soma T, Tsunoda M. Synthesis and properties of
umbelliferone-nitroxide radical hybrid compounds as fluorescence and spin-
label probes. Spectrochim Acta A 2008;70:799e804.
4. Conclusions
[6] Singh Raushan K, Mandal T, Balasubramanian N, Cook G, Srivastava DK.
Coumarin -suberoylanilide hydroxamic acid as
determining binding affinities and off-rates of histone deacetylase inhibitors.
Anal Biochem 2011;408:309e15.
a fluorescent probe for
A series of novel coumarin dyes (3e12) were designed and
synthesized in high yields by a three-step protocol. 3-(2-Benzoyl-
hydrazono-trifluoroethyl)-7-(N,N-diethylamino)coumarin (11) was
found to be able to recognize Cu2þ and Ni2þ selectively in aqueous
solution. Upon addition of Cu2þ or Ni2þ to 11 a blue shift or a bath-
ochromatic shift of the absorption band was observed while the
emission band blue-shifted with decrease in the fluorescence
intensity. Upon addition of Cu2þ, the color of the solution of 11
changed from orange to red. The results showed that 11 could serve as
[7] Hong SW, Jo WH. A fluorescence resonance energy transfer probe for sensing
pH in aqueous solution. Polymer 2008;49:4180e7.
[8] Saleh N, Al-Soud YA, Nau WM. Novel fluorescent pH sensor based on
coumarin with piperazine and imidazole substituents. Spectrochim Acta A
2008;71:818e22.
[9] Hirano T, Hiromoto K, Kagechika H. Development of
a library of 6-
arylcoumarins as candidate fluorescent sensors. Org Lett 2007;9:1315e8.
[10] Aliaga C, Juárez-Ruiz JM, Scaiano JC, Aspée A. Hydrogen-transfer reactions
from phenols to TEMPO prefluorescent probes in micellar systems. Org Lett
2008;10:2147e50.
an optical chemosensor of Cu2þ and Ni2þ
.

316
H. Li et al. / Dyes and Pigments 91 (2011) 309e316
[11] Du L, Li M, Zheng S, Wang B. Rational design of a fluorescent hydrogen
peroxide probe based on the umbelliferone fluorophore. Tetrahedron Lett
2008;49:3045e8.
[28] Kim HJ, Park JE, Choi MG, Ahn S, Chang SK. Selective chromogenic and fluo-
rogenic signalling of Hg2þ ions using a fluoresceinecoumarin conjugate. Dyes
Pigm 2009;84:54e8.
[12] Ý LD, Ý NN, Li M, Wang B. A fluorescent hydrogen peroxide probe based on
a ‘click’ modified coumarin fluorophore. Tetrahedron Lett 2010;51:1152e4.
[13] Kim HJ, Ko KC, Lee JH, Lee JY, Kim JS. KCN sensor: unique chromogenic and
turn-on fluorescent chemodosimeter: rapid response and high selectivity.
Chem Commun 2011;47:2886e8.
[14] Lee JH, Jeong AR, Shin IS, Kim HJ, Hong JI. Fluorescence turn-on sensor for cyanide
based on a cobalt(II)-coumarinylsalen complex. Org Lett 2010;12:764e7.
[15] Kim GJ, Kim HJ. Doubly activated coumarin as a colorimetric and fluorescent
chemodosimeter for cyanide. Tetrahedron Lett 2010;51:185e7.
[16] Lee KS, Kim HJ, Kim GH, Shin I, Hong JI. Fluorescent chemodosimeter for
selective detection of cyanide in water. Org Lett 2008;10:49e51.
[17] Li J, Lin H, Cai Z, Lin H. A novel coumarin-based switching-on fluorescent and
colorimetric sensor for Fꢁ. J Lumin 2009;129:501e5.
[18] Kim MJ, Swamy KMK, Lee KM, Jagdale AR, Kim Y, Kim SJ, et al. Pyrophosphate
selective fluorescent chemosensors based on coumarineDPAeCu(II)
complexes. Chem Commun; 2009:7215e7.
[19] Upadhyay KK, Mishra RK, Kumar A, Zhao J, Prasad R. Self assembled pseudo
double helix architecture and anion sensing behavior of a coumarin based ICT
probe. J Mol Struct 2010;963:228e33.
[29] Roussakis E, Pergantis SA, Katerinopoulos HE. Coumarin-based ratiometric
fluorescent indicators with high specificity for lead ions. Chem. Commun;
2008:6221e3.
[30] Capitán-Vallvey LF, Fernández-Ramos MD, Lapresta-Fernánde A, Brunet E,
Rodríguez-Ubis JC, Juanes O. Magnesium optical one-shot sensor based on
a coumarin chromoionophore. Talanta 2006;68:1663e70.
[31] Yao J, Dou W, Qin W, Liu W. A new coumarin-based chemosensor for Fe3þ in
water. Inorg Chem. Commun 2009;12:116e8.
[32] Huang S, He S, Lu Y, Wei F, Zeng X, Zhao L. Highly sensitive and selective
fluorescent chemosensor for Agþ based on
conjugate. Chem. Commun 2011;47:2408e10.
a coumarineSe2N chelating
[33] Sakamoto H, Ishikawa J, Osuga H, Doi K, Wada H. Highly silver ion selective
fluorescent ionophore: fluorescent properties of polythiazaalkane derivatives
bearing 8-(7-hydroxy-4-methyl)coumarinyl moiety in aqueous solution and
in liquideliquid extraction systems. Analyst 2010;135:550e8.
[34] Komatsu H, Miki T, Citterio D, Kubota T, Shindo Y, Kitamura Y, et al. Single
molecular multianalyte (Ca2þ, Mg2þ) fluorescent probe and applications to
bioimaging. J Am Chem. Soc 2005;127:10798e9.
[35] Lin W, Yuan L, Cao Z, Feng J, Feng Y. Fluorescence enhancement of coumar-
inequinoline by transition metal ions: detection of paramagnetic Ni2þ and
Co2þ. Dyes Pigm 2009;83:14e20.
[20] Kim MH, Jang HH, Yi S, Chang SK, Han MS. Coumarin-derivative-based off-on
catalytic chemodosimeter for Cu2þ ions. Chem Commun; 2009:4838e40.
[21] Chandrasekhar V, Bag P, Pandey MD. Phosphorus-supported multidentate
coumarin-containing fluorescence sensors for Cu2þ. Tetrahedron 2009;65:
9876e83.
[36] He G, Zhang X, He C, Zhao X, Duan C. Ratiometric fluorescence chemosensors
for copper(II) and mercury(II) based on FRET systems. Tetrahedron 2010;66:
9762e8.
[22] Jang YJ, Moon BS, Park MS, Kang BG, Kwon JY, Hong JSJ, et al. New cavitand
derivatives bearing four coumarin groups as fluorescent chemosensors for
Cu2þ and recognition of dicarboxylates utilizing Cu2þ complex. Tetrahedron
Lett 2006;47:2707e10.
[37] Lin W, Yuan L, Cao X, Tan W, Feng Y. A coumarin-based chromogenic sensor
for transition-metal ions showing ion-dependent bathochromic shift. Eur J
Org Chem.; 2008:4981e7.
[38] Kulatilleke CP, de Silva SA, Eliav Y. A coumarin based fluorescent photoin-
duced electron transfer cation sensor. Polyhedron 2006;25:2593e6.
[39] Santos HM, Pedras B, Tamayo A, Casabó J, Escriche LB, Covelo JL, et al. New
chemosensors based on thiomacrocycle-containing coumarin-343 fluo-
roionophor: X-ray structures and previous results on the effect of cation
binding on the photophysical properties. Inorg Chem. Commun 2009;12:
1128e34.
[23] Upadhyay KK, Mishra RK. Zn2þ specific colorimetric receptor based on
coumarin. Bull Chem Soc Jpn 2010;83:1211e5.
[24] Lim NC, Brückner C. DPA-substituted coumarins as chemosensors for zinc(II):
modulation of the chemosensory characteristics by variation of the position of
the chelate on the coumarin. Chem Commun; 2004:1094e5.
[25] Wang BY, Liu XY, Hu YL, Su ZX. Synthesis and photophysical behavior of
a water-soluble coumarin-bearing polymer for proton and Ni2þ ion sensing.
Polym Int 2009;58:703e9.
[40] Peng X, Li H. Synthesis and fluorescence spectra of triazolylcoumarin fluo-
rescent dyes. J Donghua Univ (Eng Ed) 2009;26:26e30.
[26] Ma W, Xu Q, Du J, Song B, Peng X, Wang Z, et al. A Hg2þ-selective chemo-
dosimeter based on desulfurization of coumarin thiosemicarbazide in
aqueous media. Spectrochim Acta A 2010;76:248e52.
[41] Chizhov DL, Sosnovskikh VY, Pryadeina MV, Burgart YV, Saloutin VI,
Charushin VN. The first synthesis of 4-unsubstituted 3-(trifluoroacetyl)
coumarins by the Knoevenagel condensation of salicylaldehydes with ethyl
trifluoroacetoacetate followed by chromeneecoumarin recyclization. Synlett;
2008:281e5.
[27] Lee DN, Kim GJ, Kim HJ. A fluorescent coumarinylalkyne probe for the selective
detection of mercury(II) ion in water. Tetrahedron Lett 2009;50:4766e8.