Syntheses, characterization and fluorescent properties of two triethylene-glycol dicoumarin-3-carboxylates

Article abstract of DOI:10.1016/j.saa.2006.12.052

Two novel triethylene-glycol dicoumarin-3-carboxylates were synthesized and characterized by element analysis, ¹H NMR, FT-IR and UV-vis absorption spectra. The photoluminescent behaviors of triethylene-glycol dibenzo[5,6]coumarin-3-carboxylate doped in PMMA were discussed. These compounds exhibit strong blue emission under ultraviolet light excitation. Compared to coumarin-3-triethylene glycol diester, the absorption and emission spectra of benzo[5,6]coumarin-3-triethylene glycol diester was bathochromically shifted due to the larger conjugation of benzene moiety. These derivatives have potential possible to explore organic electroluminescent materials.

Full text of DOI:10.1016/j.saa.2006.12.052

Spectrochimica Acta Part A 68 (2007) 725–727
Syntheses, characterization and fluorescent properties of two
triethylene-glycol dicoumarin-3-carboxylates
Hui Zhanga, Tianzhi Yua,∗, Yuling Zhaob, Duowang Fana, Long Qiana,
Changhui Yanga, Kai Zhanga
a Key Laboratory of Opto-Electronic Technology and Intelligent Control, Lanzhou Jiaotong University, Ministry of Education, Lanzhou 730070, China
b School of Chemical and Biological Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China
Received 16 November 2006; received in revised form 26 December 2006; accepted 31 December 2006
Abstract
Two novel triethylene-glycol dicoumarin-3-carboxylates were synthesized and characterized by element analysis, 1H NMR, FT-IR and UV–vis
absorption spectra. The photoluminescent behaviors of triethylene-glycol dibenzo[5,6]coumarin-3-carboxylate doped in PMMA were discussed.
These compounds exhibit strong blue emission under ultraviolet light excitation. Compared to coumarin-3-triethylene glycol diester, the absorption
and emission spectra of benzo[5,6]coumarin-3-triethylene glycol diester was bathochromically shifted due to the larger conjugation of benzene
moiety. These derivatives have potential possible to explore organic electroluminescent materials.
© 2007 Elsevier B.V. All rights reserved.
Keywords: Coumarins; Triethylene glycol; UV–vis spectrum; Photoluminescence
1. Introduction
2. Experimental
Coumarins represent a class of organic compounds which
occur naturally in a number of plants. They are also well-known
for their considerable biological and medical activities, which
not only use in the treatment of brucellosis, rheumatic disease,
burns [1], but also possess anticancer, anticoagulant [2] and anti-
fungal activities [3]. In addition, coumarin and its derivatives
show sufficient fluorescence in the visible light range to be used
in colorants, laser dyes and nonlinear optical chromophores due
to high photostability, extended spectral range, quantum yield of
photoluminescence, good solubility and easy synthesis [2,4–6].
Since Tang et al. [7] first used 3-(2-benzothiazolyl)-7-
diethylaminocoumarin (coumarin 6) as a electroluminescent
(EL) material successfully, coumarin derivatives have attracted
much interest owing to their potential application in organic
light-emitting diodes (OLEDs), many efforts have been devoted
to explore new EL materials [8–10].
2.1. Materials and measurements
2-Hydroxy-l-(1-naphthaldehyde) was obtained from Acros
Organics. All other chemicals were analytical grade reagent.
IR spectra (400–4000 cm−1) were measured on a Shimadzu
IR Prestige-21 FT-IR spectrophotometer. C, H and N analyses
were obtained using an Elemental Vario-EL automatic elemental
1
analysis instrument. H NMR spectra were obtained on Unity
Varian-500 MHz. UV–vis absorption and fluorescence spectra
were recorded on a Shimadzu UV-2550 spectrometer and on a
Perkin-Elmer LS-55 spectrometer, respectively.
2.2. Preparations of coumarin-3-carboxylic acid and
benzo[5,6]coumarin-3-carboxylic acid
Synthetic routes and their structures are shown in Scheme 1.
Coumarin-3-carboxylic acid and benzo[5,6]coumarin-3-
carboxylic acid were synthesized from salicylaldehyde,
2-hydroxy-l-(1-naphthaldehyde) according to the procedure
described in literature [11], respectively.
In this study, two new triethyleneglycol coumarin-3-
carboxylates were synthesized, and the UV–vis spectra and
photoluminescence were investigated in detailed.
Benzo[5,6]coumarin-3-carboxylic acid (2). The solution of
14.10 g (0.082 mol) of 2-hydroxy-l-(1-naphthaldehyde), 14.4 g
(0.09 mol) of diethyl malonate, 60 ml of absolute ethanol, 1 ml
∗
Corresponding author. Tel.: +86 931 4956935; fax: +86 931 4938756.
E-mail address: ytz823@hotmail.com (T. Yu).
1386-1425/$ – see front matter © 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2006.12.052

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H. Zhang et al. / Spectrochimica Acta Part A 68 (2007) 725–727
Scheme 1. Synthetic scheme of the derivative of coumarin-3-carboxylic acid.
of piperidine and 10 drops of acetic acid was stirred at 80–90 ◦C
for 6 h. Then the mixture was poured into 100 ml of ice-water
mixture, and yellow precipitate was obtained. The precipitate
was filtered and washed with distilled water and 50% ethanol
solution, respectively. The product was dried under reduced
pressure, and purified with re-crystallization from 50% ethanol
solution, 10 g (50% yield) of brown crystals of the compound 1
was obtained.
Five grams of the compound 1, 3 g of NaOH were dissolved
into 30 ml of 95% ethanol and 20 ml of water, and the mixture
was refluxed with stirring for 2 h. After cooling to room temper-
ature, the mixture was poured into an aqueous solution of HCl
with vigorous stirring, and yellow precipitate was produced. The
precipitate was filtered, dried and recrystallized from acetic acid,
and yellow fibriform crystal compound 2 was obtained (yield
48%). m.p. 235–236 ◦C. IR (KBr pellet, cm−1): 3063,1752,
1669.
1
cm-1): 2911, 1752, 1606, 1129. H NMR (400 MHz, CDCl3,
δ, ppm): 3.734–3.753(d, 4H, b-H), 3.853–3.877 (t, 4H, a-H),
4.496–4.519 (t, 4H, c-H), 7.266–7.669 (m, 8H, Ar-H), 8.556 (s,
2H, d-H).
Triethylene-glycol dibenzo[5,6]coumarin-3-carboxylate (5).
Compound 5 was obtained from benzo[5,6]coumarin-3-
carboxylic acid and triethylene glycol following a procedure
similar to that described for compound 4. m. p. 173–175 ◦C.
IR (KBr pellet, cm−1): 2921, 1764, 1699, 1102. H NMR
1
(400 MHz, CDCl3, δ, ppm): 3.807–3.853(m, 4H, b-H),
3.925–4.004 (m, 4H, a-H), 4.557–4.623 (m, 4H, c-H),
7.267–8.229(m, 12H, Ar-H), 9.210 (s, 2H, d-H).
3. Results and discussion
3.1. UV–vis absorption spectra
Coumarin-3-carboxylic acid (3) were obtained following
a procedure similar to that described for compound 2. m.p.
184–187 ◦C. IR (KBr pellet, cm−1): 3435, 2927, 1734, 1636.
UV–vis absorption spectra of the compounds 4 and 5 in
diluted chloroform solutions are given in Fig. 1. We can see that
the absorption spectrum of the compound 4 shows absorptions
at λmax = 293 and 329 nm.
The two absorption peaks of the compound 5 were observed
at 336 and 376 nm, which were bathochromically shifted, com-
pared to the compound 4, it is suggesting that the conjugation
of benzocoumarin ring is larger than that of coumarin skeleton
in the compound 4. As a result, the red shift of absorption can
possibly occur.
2.3. Preparations of triethylene-glycol
dicoumarin-3-carboxylate (4) and triethylene-glycol
dibenzo[5,6]coumarin-3-carboxylate (5)
The synthetic strategies are described in Scheme 2.
2.27 g (0.015 mol) of triethylene glycol and 6.32 g
(0.030 mol) of coumarin-3-acyl chloride obtained by the reac-
tion of compound 3 with SOCl2 were dissolved into 30 ml
of pyridine. The mixture was stirred at 90 ◦C for 29 h. After
cooling to room temperature, the mixture was sedimentated by
95% ethanol. The precipitates was filtered, dried and recrys-
tallized from ethyl acetate to yield 2.35 g (32%) of white
crystals (4). m.p. 130 ◦C. Element analysis is found (calcu-
lated): C, 63.04% (63.16%); H, 4.42% (4.45%). IR (KBr pellet,
3.2. Fluorescence spectra
Fig. 2 shows emission fluorescence spectra of two coumarins
derivatives in dilute solutions. It is shown that the emission peaks
of two compounds appeared at around 406 and 438 nm, respec-
tively. The compound 5 exhibits bright blue emission with peak
Scheme 2. Synthetic route to the compounds 4 and 5.

H. Zhang et al. / Spectrochimica Acta Part A 68 (2007) 725–727
727
5 with PMMA were prepared by dissolving these components
with a certain molar ratios into acetone. The samples for photolu-
minescent spectroscopy were made by spin-coating the acetone
solutions onto clean quartz substrates. It was found that the emis-
sion spectral features of the compound in the systems change
with the molar ratios of the compound and PMMA. When the
molar ratio was lower 2, the emission peaks were located at
around 430 nm, and the relative intensities increase gradually
with increasing the molar ratios. When the ratio was higher
than 2, the emission peak was shifted to longer wavelength, and
the emission intensity was decreasing. These compounds are
the fluorescence dyes, the fluorescence intensity is intensively
quenched by concentration of the compounds, so it was found
that a self-quenching was occurred. On the other hand, the shape
of emission spetra is intensively affected by the intermolecular
interaction, thus may lead to change of the emission band with
increasing the molar ratios.
Fig. 1. UV–vis absorption spectra of the compounds 4(ꢀ) and 5(ꢁ) in chloro-
form (7.14 × 10−5 mol/l).
4. Conclusions
The novel coumarin derivatives were successfully synthe-
sized and the photophysical properties have been carried out.
With the benzene moiety, both the edge of absorption and emis-
sion spectra were shift to long wavelength side, emitting blue
light. Based on the results, the compounds 4 and 5 are poten-
tial candidates for use in opto- or optoelectronic blue-emitting
devices. Other characteristics of them will be studied in future.
Acknowledgement
Fig. 2. Fluorescence emission spectra of the compounds 4(ꢀ) and 5(ꢁ) in dilute
acetone solutions at room temperature. (C4 = 7.14 × 10−8 mol/l, λex = 333 nm,
C5 = 7.14 × 10−14 mol/l, λex = 345 nm.)
This work was financially supported by ‘Qing Lan’ talent
engineering funds (QL-06-01A) of the Lanzhou Jiaotong Uni-
versity.
at 438 nm, which was bathochromically shifted with respect to
that of 4 because of the larger conjugation of benzene moiety.
The photoluminescent behaviors of the compound 5 doped
in poly(methyl methacrylate) (PMMA) were investigated in
detailed as shown in Fig. 3. Mixed systems of the compound
References
[1] M. Walshe, J. Howarth, M.T. Kelly, R.O. Kennedy, M.R. Smyth, J. Pharm.
Biomed. Anal. 16 (1997) 319.
[2] B. Kovac, I. Novak, Spectrochim. Acta, Part A 58 (2002) 1483.
[3] S. Sardari, Y. Mori, K. Horita, R.G. Micetich, S. Nishibe, M. Daneshtalab,
Bioorg. Med. Chem. 7 (1999) 1933.
[4] R.F. Zhang, H.P. Zheng, J.C. Shen, Synth. Met. 106 (1999) 157.
[5] H. Ammar, S. Fery-Forgues, R.E. Gharbi, Dyes Pigments 57 (2003)
259.
[6] J. Preat, D. Jacquemin, E.A. Perpete, Chem. Phys. Lett. 415 (2005) 20.
[7] C.W. Tang, S.A. VanSlyke, C.H. Chen, J. Appl. Phys. 65 (1989) 3610.
[8] C.T. Chen, C.L. Chiang, Y.C. Lin, L.H. Chan, C.H. Huang, Z.W. Tsai, C.T.
Chen, Org. Lett. 5 (2003) 1261.
[9] M.T. Lee, C.K. Yen, W.P. Yang, H.H. Chen, C.H. Liao, C.H. Tsai, C.H.
Chen, Org. Lett. 6 (2004) 1241.
[10] S.A. Swanson, G.M. Wallraff, J.P. Chen, W.J. Zhang, L.D. Bozano,
K.R. Carter, J.R. Salem, R. Villa, J.C. Scott, Chem. Mater. 15 (2003)
2305.
[11] L.F. Tietze, U. Beifuss, in: B.M. Trost, I. Fleming, C.H. Heathcock (Eds.),
Comprehensive Organic Synthesis, vol. 2, Pergamon Press, Oxford, 1991,
p. 341.
Fig. 3. The emission spectral features of the compound 5 in the compound
5/PMMA systems (CPMMA = 5 mg/ml, λex = 345 nm).