High quantum yield and pH sensitive fluorescence dyes based on coumarin derivatives: Fluorescence characteristics and theoretical study

Article abstract of DOI:10.1039/c6ra05996a

The fluorescence coumarin derivatives were synthesized by an efficient one-pot, three-component reaction in 80-90% yields. These fluorescence dyes exhibited high fluorescent intensity and quantum yield where compound 4e, with p-methyl substituted on the phenyl ring, had the maximum fluorescence intensity and also the fluorescence quantum yield reached 0.83. These coumarin derivatives display different fluorescence in acidity and alkaline conditions and the fluorescent colour changed from blue to yellow-green when the pH of the solution turned from acidic to alkaline. The pH sensitive fluorescence properties of the coumarin derivatives showed a large shift from 441 to 538 nm in wavelength. Experimental results were confirmed with DFT and TDDFT calculations.

Full text of DOI:10.1039/c6ra05996a

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High Quantum Yield and pH sensitive Fluorescence dyes Based on
Coumarin Derivatives ：Fluorescence Characteristics and Theoretical
Study
Chao-jun Hua, Kan Zhang, Ming Xin, Ting Ying, Jian-rong Gao, Jian-hong Jia,
Yu-jin Li*
College of Chemical Engineering, Zhejiang University of Technology, Hangzhou
310014, People's Republic of China.
E-mail: lyjzjut@zjut.edu.cn
ABSTRACT The fluorescence coumarin derivatives were synthesised by an efficient
oneꢀpot, threeꢀcomponent reaction in 80ꢀ90% yields. These fluorescence dyes exhibited
high fluorescent intensity and quantum yield，which the compound 4e with pꢀmethyl
substituted on the phenyl ring had the maximum fluorescence intensity and also the
fluorescence quantum yield reached 0.83. These coumarin derivatives display the
different fluorescence in acidity and alkaline conditions and the fluorescent colour changed
from blue to yellowꢀgreen when the pH of solution turned acidic to alkaline. The pH
sensitive fluorescence properties of the coumarin derivatives showed larger shift from 441
to 538 nm in wavelength. Experimental results have been confirmed with DFT and TDDFT
calculations.
KEYWORDS: Fluorescent; Coumarin Derivatives; High Quantum Yield; Synthesis; DFT
calculations;
INTRODUCTION

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Coumarins consist of pyrone and benzene1 which are considered with versatile applications
in various fields of science and technology,2 such as perfume,3 cosmetic,4 as a disperse
dye,5 cationic dye,6 chargeꢀtransfer agent,7 solar energy collectors8 and potential application
in organic lightꢀemitting diodes (OLEDs)9etc. Besides, coumarin derivatives have played
an important role in medicinal chemistry such as the platelet inhibition agent, antithrombus
agent,10 hepatoprotective and so on.
Coumarins are the wellꢀknown laser dyes for the bluegreen spectral region11 whose
derivatives is one of the most favorable fluorophore groups to develop fluorescence agent12
because of its high quantum yields and high photostability.13 It was reported14 that the
electron donating groups in the 7ꢀposition and electronꢀwithdrawing groups in the
3ꢀposition can be able to enhance the fluorescence intensity of coumarins15 based on an
intramolecular charger transfer process.16 Among different coumarin dyes , Xu’s group
reported that the 7ꢀ(N,Nꢀdiethylamino)coumarinꢀ3ꢀaldehyde were selected as fluorophore
and ionphore for the construction of Cu2+ selective fluorescence sensors,17 and in 2006 Li’s
group reported the 7ꢀaminocoumarin derivatives dyes underwent change in their dipole
moment on excitation from the ground to the excited S1 state transition.18 Thus, these
molecules are found to be suitable sensors in investigating many physical and
physiochemical processes in the condensed phase,19 making use of their fluorescence
properties.
Optical methods20 via fluorescent imaging and sensing are attracting attention for pH
measurements due to its rapid response time,21 simplicity, nonꢀinvasiveness and a good
sensitivity.22 Currently, a large number of fluorescence sensors for pH measurement have

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been reported in the literature and are commercially available due to its extensive
applications. As an example, Liu23 published coumarin sensors have optical responses in
acid condition. Their studies disclosed that these coumarin derivatives could be used for
quantitative fluorescence imaging in the detection of intracellular pH by the formation of an
intramolecular charge transfer (ICT) platform in acidic environment, leading to colour
changes. In addition, Oliveira’s group24 designed a new ratiometric fluorescent pH coumarin
quinoline derivative sensor, whereas in acidic pH exhibits a strong fluorescence, being very
useful for monitoring pH variations from neutral to acidic conditions in living cells.
To the best of our work, a series of high fluorescence quantum yield coumarin derivatives
were synthesized in a very simple and facile economically cheap route which based on the
literature from Ahmed’ s group.25 And the optical properties were investigated in the different
conditions. There are high fluorescent intensity and quantum yield in DMSO. Moreover, we
describe the different phenomenon between acid and alkaline in DMSO. Besides, we were
using the DFT and TDDFT calculations to confirm the experimental results.
EXPERIMENTAL SECTION
General Methods.
All of the chemicals used in the current study were purchased from commercial vendors and
used as received without further purification, unless otherwise noted. All solvents were purified
and dried using standard methods prior to use. Nuclear magnetic resonance (1H, 13C) spectra
were recorded on a Bruker AM 500 spectrometer with chemical shifts reported as ppm at 500,
125 MHz, respectively, (in DMSO and TMS as the internal standard). Fluorescence spectra

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were obtained with a Fꢀ7000 Fluorescence Spectrophotometer in a solution of 1.0×10ꢀ5 mol/L.
UVꢀVis absorption spectra were measured on a UVꢀ2550. The absorption and emission studies
at different pH were all measured in DMSOꢀwater mixture (DMSO:H2O=9:1).
General Procedure for the Synthesis of 4-aminocoumarin.
A mixture of well powdered 4ꢀhydroxycoumarin (1.07 g, 0.0066 mol) and ammonium acetate
(7.87 g, 0.100 mol) was melted in an oil bath (max. 130 ºС) and stirred for 3 h. After cooling to
ambient temperature, water was added and the crude product was isolated as yellow crystals by
simple filtration. 4ꢀaminocoumarin was obtained by recrystallized from EtOH and water as
yellow crystals (0.98 g, 92.2%).25
General Procedure for the Synthesis of compound 4a-4e.
A mixture of benzaldehyde (0.106 g, 1 mmol), 1,3ꢀcyclohexanedione (0.112 g , 1 mmol) and
4ꢀaminocoumarin(0.161 g, 1 mmol) in acetic acid (6 mL) was stirred for 2ꢀ3 h at 110 ℃ and
complete reaction was detected by TLC analysis and then cooled to room temperature. Then,
the reaction mixture was washed with H2O (20 ml) and the crude product was recrystallized
from DMSO to give product 4a (0.295 g, 86.3 %) as light yellow solid.25
7ꢀphenylꢀ9,10,11,12ꢀtetrahydroꢀ6Hꢀchromeno[4,3ꢀb]quinolineꢀ6,8(7H)ꢀdione (4a)
Light yellow solid. Yield 86%. Mp 296ꢀ298 .1HꢀNMR (DMSO, 500 MHz)
δ (ppm): 9.76
(s,1H), 8.32 (d, J = 8.0 Hz, 1H), 7.62ꢀ7.65 (m, 1H), 7.44 (t, J = 7.5 Hz, 1H), 7.38 (d, J = 8.3
Hz, 1H), 7.11ꢀ7.24 (m, 4H), 7.09 (t, J = 7.2 Hz, 1H), 4.99 (s, 1H), 2.82ꢀ2.87 (m, 1H), 2.67ꢀ2.73
(m, 1H), 2.24ꢀ2.32 (m, 2H), 1.98ꢀ2.02 ( m, 1H), 1.87ꢀ1.88 (m, 1H). 13C NMR (DMSO, 125
MHz) δ (ppm): 194.93 (1C), 160.33 (1C), 152.02 (1C), 151.67 (1C), 145.90 (1C), 142.05 (1C),

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131.92 (1C), 128.02 (2C), 127.65 (2C), 126.18 (1C), 123.97 (1C), 122.93 (1C), 116.85
(1C),113.03 (1C), 111.86 (1C), 101.78 (1C), 36.66 (1C), 34.12 (1C), 26.37 (1C), 20.71 (1C).
7ꢀ(4ꢀnitrophenyl)ꢀ9,10,11,12ꢀtetrahydroꢀ6Hꢀchromeno[4,3ꢀb]quinolineꢀ6,8(7H)ꢀdione(4b).
1
Light yellow solid. Yield 90%. Mp 260ꢀ262 . HꢀNMR (DMSO,500 MHz)
δ
(ppm): 9.88 (s,
1H), 8.34ꢀ8.36 (m, 1H), 8.08ꢀ8.10 (m, 2H), 7.65ꢀ7.68 (m, 1H), 7.51ꢀ7.54 (m, 2H), 7.45ꢀ7.48 (m,
1H), 7.40 (t, J = 7.7 Hz, 1H), 5.11 (s, 1H), 2.87 (t, J=9.4Hz, 1H), 2.73 (t, J = 3.9 Hz, 1H),
2.27ꢀ2.33 (m, 2H), 1.98ꢀ2.02 (m, 1H), 1.88 (s, 1H). 13C NMR (DMSO, 125 MHz)
δ (ppm):
194.89 (1C), 160.21 (1C), 153.12 (1C), 152.31 (1C), 152.14 (1C), 145.94 (1C), 142.60 (1C),
132.22 (1C), 129.10 (2C), 124.06 (1C), 123.26 (2C), 123.12 (1C), 116.92 (1C), 112.83 (1C),
110.97 (1C), 100.63 (1C), 36.50 (1C), 34.96 (1C), 26.38 (1C), 20.61 (1C).
7ꢀ(4ꢀmethoxyphenyl)ꢀ9,10,11,12ꢀtetrahydroꢀ6Hꢀchromeno[4,3ꢀb]quinolineꢀ6,8(7H)ꢀdione(4c).
Light yellow solid. Yield 88%. Mp 276–278 . 1HꢀNMR (DMSO,500 MHz)
δ (ppm): 9.72 (s,
1H), 8.30ꢀ8.32 (m, 1H), 7.61ꢀ7.65 (m, 1H), 7.42ꢀ7.45 (m, 1H), 7.37 (t, J = 8.2 Hz, 1H),
7.13ꢀ7.14 (m, 2H), 6.75ꢀ6.77 (m, 2H), 4.93 (s, 1H), 3.66 (s, 3H), 2.81ꢀ2.86 (m, 1H), 2.65ꢀ2.72
(m, 1H), 2.24ꢀ2.32 (m, 2H), 1.98ꢀ2.03 (m, 1H), 1.84ꢀ1.90 (m, 1H). 13C NMR (DMSO, 125
MHz) δ (ppm): 194.90 (1C), 160.32 (1C), 151.98 (1C), 151.32 (1C), 141.74 (1C), 138.23 (1C),
131.80 (1C), 128.59 (3C), 123.91 (1C), 122.86 (1C), 116.79 (1C), 113.38 (2C), 113.05 (1C),
112.09 (1C), 102.06 (1C), 55.99 (1C), 36.67 (1C), 33.19 (1C), 26.33 (1C), 20.74 (1C).
7ꢀ(3ꢀchlorophenyl)ꢀ9,10,11,12ꢀtetrahydroꢀ6Hꢀchromeno[4,3ꢀb]quinolineꢀ6,8(7H)ꢀdione (4d).
Light yellow solid. Yield 82% . Mp 267–269 . 1HꢀNMR (DMSO,500 MHz)
δ (ppm): 9.82(s,
1H), 8.33ꢀ8.35 (m, 1H), 7.46 (s, 1H), 7.39ꢀ7.41 (m, 1H), 7.36ꢀ7.38 (m, 3H), 7.28(m, 1H), 5.26
(s, 1H), 2.85ꢀ2.88 (m, 1H), 2.68ꢀ2.72 (m, 1H), 2.29ꢀ2.33(m, 2H), 2.00ꢀ2.02 (m, 1H), 1.83 (s,

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1H). 13C NMR (DMSO, 125 MHz)
δ (ppm): 194.96 (1C), 160.30 (1C), 152.11 (1C), 149.12
(1C), 140.13 (1C), 133.39 (1C), 132.14 (1C), 131.21 (1C), 128.34 (1C), 126.83 (1C), 123.95
(1C), 121.08 (1C), 120.23 (1C), 116.82 (1C), 114.08 (1C), 113.04 (1C), 111.01 (1C), 101.09
(1C), 36.61 (1C), 33.93 (1C), 26.37 (1C), 20.65 (1C).
7ꢀ(pꢀtolyl)ꢀ9,10,11,12ꢀtetrahydroꢀ6Hꢀchromeno[4,3ꢀb]quinolineꢀ6,8(7H)ꢀdione(4e).
Light
yellow solid. Yield 83%. Mp 304–30
5
.1HꢀNMR (DMSO,500 MHz) δ (ppm) : 9.72 (s, 1H),
8.30ꢀ8.32 (m, 1H), 7.61ꢀ7.63 (m, 1H), 7.41ꢀ7.45 (m, 1H), 7.36 (t, J = 8.2 Hz, 1H ), 7.12 (d, J =
8.05 Hz, 2H), 7.00 (d, J = 7.95 Hz, 2H), 4.95 (s, 1H), 2.82ꢀ2.86 (m, 1H), 2.69ꢀ2.71 (m, 1H),
2.18ꢀ2.31 (m, 2H), 2.19 (s, 3H), 2.0ꢀ2.02 (m, 1H), 1.82ꢀ1.89 (m, 1H). 13C NMR (DMSO, 125
MHz) δ (ppm): 194.86 (1C), 160.28 (1C), 151.99 (1C), 151.40 (1C), 143.04 (1C), 141.87 (1C),
135.15 (1C), 131.81 (1C), 128.54 (2C), 127.52 (2C), 123.90 (1C), 122.87 (1C), 116.79 (1C),
113.02 (1C), 112.00 (1C), 101.91 (1C), 36.66 (1C), 33.66 (1C), 26.34 (1C), 20.72 (1C), 20.51
(1C).
Computational Methodology.
All the structure optimization were based on density functional theory (DFT) with B3LYP
functional and 6ꢀ311G basis set. For the fluorescence emission wavelength and the excitation
wavelength of the compounds was calculated with the timeꢀdependent density functional
theory (TDDFT). All these calculations were performed with Gaussian 09W.26
RESULTS AND DISCUSSION
As shown in Scheme 1, the coumarin fused dihydropyridine derivatives 4 were synthesized by
the efficient threeꢀcomponent reaction of 1,3ꢀcyclohexadione, arylaldehydes and the product 4
were obtained in 86 % (4a), 90 % (4b), 88 % (4c), 82 % (4d), 83 % (4e) yields, respectively.

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Paraꢀnitro substituent on the benzene unit have the largest yields (90%) of the desired product
was obtained. These compounds were all characterized by 1HꢀNMR and 13CꢀNMR.
Scheme 1. Synthesis of coumarin fused dihydropyridine derivatives 4.
UV-vis absorption and fluorescence emission spectra.
The absorption and fluorescence emission spectra of the coumarin fused dihydropyridine
derivatives 4 was detected and summarized in Fig. 1. The fluorescence properties of the
coumarin derivatives 4 were examined under different conditions such as: in different
organic solvents and the different pH.
Fig. 1. Left: Absorption spectra of compound 4c (1.0×10ꢀ5 mol/L) in different Solution (PMT
Voltage: 900 V). Right: Fluorescence emission spectra of compound 4c in different Solution
(PMT Voltage: 500 V).

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The solvent effect on the absorption and fluorescence properties of the
7ꢀ(4ꢀmethoxyphenyl)ꢀ9,10,11,12ꢀtetrahydroꢀ6Hꢀchromeno[4,3ꢀb]quinolineꢀ6,8(7H)ꢀdione(4
c) were examined (Fig. 1, Table 1). As shown in Fig. 1, the coumarin 4c showed a
maximum sharp absorption peak at approximately 308 nm accompanied a shoulder peak at
near 375 nm and were barely affected by solvent polarity. The molar absorption coefficient
(ε) of 4c underwent a slight change in different organic solvents and which in MeCN had
the highest value.
Obviously, the compound 4c shows the fluorescence emission wavelength at 438 nm with
375 nm as the excitation wavelength in the different organic solvents, excepted the slight
blue shift in CH3CN (410 nm). It’s worth noting that the fluorescence intensity of the
compound 4c is much higher in DMSO than other solvents and thus we can anticipate the
high fluorescence quantum yields in DMSO. Thus the Stokes shift is 63 nm in DMSO. So
we selected DMSO as its best solvent for the study on the fluorescent properties of the
compound 4.
Fig.2. Left: Absorption spectra of different compounds (1.0×10ꢀ5 mol/L) in DMSO (PMT
Voltage: 900 V). Right: Fluorescence emission spectra of different compounds 4a-4e in
DMSO (PMT Voltage: 600 V).
The absorption and fluorescence emission spectra of the compounds 4a-4e in DMSO were

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shown in Table 1 and Fig. 2. These compounds 4 showed the similar absorption, but a
slight change in intensity with in the different substituted on the phenyl ring. Similarly, the
fluorescence emission wavelength of 4 was at about 440 nm and showed a strong blue
fluorescence, but the intensity of the fluorescence was significantly different with the
different groups substituted on the phenyl ring of the coumarin fused dihydropyridine
derivatives 4. As shown in Fig. 2, the compound 4e with pꢀmethyl substituted on the phenyl
ring had the maximum fluorescence intensity and also the fluorescence quantum yield
reached 0.83. The compound 4a (H), 4c (4ꢀOMe), 4d (3ꢀCl) all had strong blue
fluorescence and the fluorescence quantum yield is respectively 0.41, 0.26, 0.60. It is worth
noting that compound 4e shows unexpected high fluorescence quantum yields (ΦF = 0.83)
than most of the fluorophores, and the Stokes shift of compound 4e is 75 nm. The
compound 4b with pꢀnitro substituted on the phenyl ring displayed the maximum of
absorption and the minimum of fluorescence intensity, so it’s fluorescence is weak and the
fluorescence quantum yield is only 0.014. In addition, through the TDꢀDFT calculation, the
HOMO–LUMO energy gap of compound 4b is largest, which make the transition hard to
happen. As shown in Table 1, the Stokes shift of the compound 4a, 4b, 4c, 4e, 4d
respectively were 72, 68, 80, 70, 75 nm in DMSO.
Table 1 Photophysical properties of compound 4a-4e.
compounds
λaabs(nm)
368
λaem(nm)
440
ε(Mꢀ1cmꢀ1)
14,000
Φa
SSb(nm)
72
F
0.41
4a
4b
373
441
18,700
0.014
68

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361
373
366
441
443
441
20,800
15,200
15,300
0.26
0.60
0.83
80
70
75
4c
4d
4e
aMeasurements were performed in DMSO solvent. Fluorescence quantum yields were measured with quinine
sulfate (ΦF=54.6% in 0.05 M H2SO4) as the reference. bStokes shift.
Fig. 3. Left: The absorption spectra of compound 4a with different pH (1.0×10ꢀ5 mol/L) in
DMSOꢀwater mixture (DMSO:H2O=9:1, PMT Voltage: 900 V). Right: Fluorescence
emission spectra of compound 4a (1.0×10ꢀ5 mol/L) with different pH in DMSOꢀwater
mixture (DMSO:H2O=9:1, PMT Voltage: 500 V).
Fig. 4. Left: Compound 4a (1.0×10ꢀ5 mol/L) under the visible light with different pH in
DMSOꢀwater mixture (DMSO:H2O=9:1). Right: Compound 4a (1.0×10ꢀ5 mol/L) under the
UV lamp (365 nm) with different PH in DMSOꢀwater mixture (DMSO:H2O=9:1).

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Fig. 5. Left: the absorption spectra of compound 4a-4e (1.0×10ꢀ5 mol/L) with pH=11. Right:
the fluorescence emission spectra of compound 4a-4e (1.0×10ꢀ5 mol/L) with pH=7 and
pH=11 in DMSOꢀwater mixture (DMSO:H2O=9:1, PMT Voltage: 550 V).
On the other hand, we also examined the absorption and fluorescence properties of the
compound 4 under the different pH from 2 to 12 in DMSOꢀwater mixture (DMSO:H2O=9:1).
As shown in Fig.3 and Fig.4 , the compound 4a exhibited the different property of the UVꢀvis
absorption and fluorescence spectra. A new absorption appeared at 455 nm which situated at
visible region as the pH value gradually increased from 7 to 12 in DMSOꢀwater mixture. It
can be seen intuitively, the solution was colorless under acidic condition and lower yellow
under basic condition. The fluorescence intensity of 4a was obviously larger in the alkaline
condition than in the acidic condition. The maximal emission wavelength of 4a had an
obvious red shift (103 nm) under the different pH conditions, which was displayed the blue
fluorescence in 450 nm under acidic condition (pH: 2~7) and the yellowꢀgreen fluorescence
in 553 nm under basic condition (pH: 7~12). This effect is brought about significant changes
in fluorescence color, blue in acid solution and yellow green in the alkaline environment (Fig.
4). Moreover, the substituted compound 4c-4e exhibited the same property accompanied by
the change of pH value and the maximal absorption wavelength displayed a red shift from

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375 nm to 450 nm with the solution from acid to alkaline. And then the fluorescence intensity
varied with the pH obviously and the fluorescence intensity reached a maximum when the pH
value of solution was reached to 11. However, the fluorescence emission wavelength of
compound 4b did not change significantly in alkaline condition. It happened due to the an
intermolecular charger transfer (ICT) process.27
DFT calculations: rationalize the excitation and emission spectra. Recently theoretical
calculations are becoming attractive for study of the fluorescence or molecular probes26. In
older to support our assumptions we made the compounds geometry optimizations using the
density functional theory (DFT) method as implemented in Gaussian 09W suits of the
program employing basis sets B3LYP/6ꢀ311G (see Fig.6.). There are shown the most stable
structures of compounds 4a-4e and indicated that the precursor of these compounds
containing a large conjugated system obviously.28 Therefore, It is useful for the fluorescence
properties.29 However, the benzene ring which at the bottom of the pyridine do not in the
same plane due to the steric effect of the carbonyl groups.

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Fig.6 Optimized geometry of the compounds 4aꢀ4e at B3LYP/6ꢀ311g level with Gaussian
09W.
TDꢀDFT calculations were performed at this study to further understand the mechanism of the
fluorescence intensity with different groups by the energy and charge transfer model (see
Fig.7 ). Besides, we calculated the fluorescence emission spectra and the HOMO–LUMO
energy gap30 by TDꢀDFT method as implemented(see Table 2). From this calculation, the
compound 4b is required more energy (ꢁE = 0.66 eV) to finish HOMOꢀLUMO transition and
the compound 4e is required least energy (ꢁE = 0.31 eV) to finish HOMOꢀLUMO transition on
the contrary. Therefore, the photochemical property of the compound 4b (ΦF = 0.014) is bad
than the compound 4e (ΦF = 0.83).

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Fig.7 Frontier molecular orbitals of compound 4b and 4e
Table 2. Calculation data of compound 4a-4e.
f e
compounds
λa
λb
λccal
λd
exp
Transition
character
Energy
gap
cal
exp
(nm)
(nm)
(nm)
(nm)
(eV)
0.44
0.66
0.44
0.39
0.31
450
473
455
447
459
440
441
441
443
441
372
375
368
373
367
368
373
361
373
366
0.0122 HOMO→LUMO
0.0093 HOMO→LUMO
0.0154 HOMO→LUMO
0.0189 HOMO→LUMO
0.0215 HOMO→LUMO
4a
4b
4c
4d
4e
b
atheoretical calculations basis sets B3LYP/6ꢀ311G without solution ( The calculated emission maximums ). λmax in DMSO
c
solvent (The experimental emission maximums). theoretical calculations basis sets B3LYP/6ꢀ311G without solution ( The
d
calculated absorption maximums ). λmax in DMSO solvent (The experimental absorption maximums). e Oscillator strength
coefficients.
CONCLUSIONS
The coumarin fused dihydropyridine derivatives were prepared by an efficient oneꢀpot,
threeꢀcomponent reaction and obtained in good yield. The optical properties detection indicated

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that these coumarin derivatives had excellent fluorescence with high fluorescent quantum yield
and exhibited significant emission change in fluorescence spectrum with the change of pH
value. TDꢀDFT calculations were performed at this study to support our experiment results.
Our findings will be useful for design of new pH probe fluorescent dyes with high fluorescent
quantum yield and the chemical sensors for detecting pH environment.
Acknowledgement
We gratefully acknowledge the financial supported by the Natural Science Foundation of China
(21176223) and the National Natural Science Foundation of Zhejiang (LY13B020016) and the
Key Innovation Team of Science and Technology in Zhejiang Province (2010R50018).
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High Quantum Yield and pH sensitive Fluorescence dyes Based
on Coumarin Derivatives ：Fluorescence Characteristics and
Theoretical Study
State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, Zhejiang University of
Technology, Hangzhou 310014, People’s Republic of China
ABSTRACT
The fluorescence coumarin derivatives were synthesised by an efficient one-pot,
three-component reaction in 80-90% yields. These fluorescence agents exhibited high
fluorescent intensity and quantum yield，which the compound 4e with p-methyl
substituted on the phenyl ring had the maximum fluorescence intensity and also the
fluorescence quantum yield reached 0.83. These coumarin derivatives display the
different fluorescence in acidity and alkaline conditions and the fluorescent colour
changed from blue to yellow-green when the pH of solution turned acidic to alkaline.
The pH sensitive fluorescence properties of the coumarin derivatives showed larger
shift from 441 to 538 nm in wavelength. Experimental results have been confirmed
with DFT and TDDFT calculations.
HN
O
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1