A Way to Improve Luminescent Efficiency of Bis-Chalcone Derivatives

Article abstract of DOI:10.1155/2016/3608137

Chalcone related compounds have been reported as a poor luminescence molecule due to the quenching processes from the intramolecular torsional motions and cis-trans isomerization in the α,β-unsaturated ketone moiety. Despite this limitation, we found a wa

Full text of DOI:10.1155/2016/3608137

Hindawi Publishing Corporation
Journal of Chemistry
Volume 2016, Article ID 3608137, 8 pages
http://dx.doi.org/10.1155/2016/3608137
Research Article
A Way to Improve Luminescent Efficiency of
Bis-Chalcone Derivatives
Meng Guan Tay,1 Mee Hing Tiong,1 Ying Ying Chia,1
Suzie Hui Chin Kuan,1 and Zhi-Qiang Liu2
1Department of Chemistry, Faculty of Resource Science and Technology, Universiti Malaysia Sarawak,
94300 Kota Samarahan, Sarawak, Malaysia
2State Key Laboratory of Crystal Materials, Shandong University, 27 Shanda South Road, Jinan 250100, China
Correspondence should be addressed to Meng Guan Tay; mgtay@unimas.my
Received 30 April 2016; Accepted 20 June 2016
Academic Editor: Artur M. S. Silva
Copyright © 2016 Meng Guan Tay et al. is is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Chalcone related compounds have been reported as a poor luminescence molecule due to the quenching processes from the
intramolecular torsional motions and cis-trans isomerization in the ꢀ,ꢁ-unsaturated ketone moiety. Despite this limitation,
we found a way to improve the luminescent efficiency of our bis-chalcone derivative. In this project, two series of bis-
chalcone compounds have been synthesized through Claisen-Schmidt condensation by reacting terephthaldehyde or 2,5-
dimethoxyterephthaldehyde with the respective R-acetophenone [where R = H (1a and 2a) and ortho-hydroxy (1b and 2b)] in
1 : 2 mole ratio. e presence of a methoxy (OMe) substituent on the central phenyl ring of bis-chalcone has weakened the C=C
bond at the ꢀ,ꢁ-unsaturated ketone moiety of 2a and 2b. Interestingly, the OMe group has improved the emission efficiency of the
bis-chalcone; that is, the quantum yield of 1a in DCM solution was not able to be determined due to poor luminescence, but the
quantum yield of 2a in DCM solution was improved to 0.57. In addition, compound 2a also shows solvatochromism effect where
the ꢂmax emission shifed from 499 nm in nonpolar solvents (benzene) to 523 nm in polar solvents (acetonitrile). is work provides
another way to improve the emission efficiency of chalcone related compounds apart from using the complexation method which
has been reported before.
1. Introduction
of metal ions [8–14]. However, one of the main limitations
in the photophysical properties of chalcones is their weak
luminescent efficiency, which is due to quenching processes
from the intramolecular torsional motions and cis-trans
isomerization in the ꢀ,ꢁ-unsaturated ketone moiety [15, 16].
Unlike the biological properties, the photophysical prop-
erties of chalcone derivatives such as 2ꢀ-hydroxychalcones
have still not been fully understood. is could be the reason
for limited use of chalcone derivatives and complexes in
current green technology devices. D’Ale´o and his coworkers
(2012) found that the boron complexes with 2ꢀ-hydroxychal-
cone derivatives can increase the fluorescent efficiency from
0.02 to 0.79 by substituting different electron donor groups
at the 2ꢀ-hydroxychalcone moiety [17]. Herein, we report
two series of bis-chalcone derivatives (Scheme 1) in which
the emission efficiency also showed dramatic improvement
afer addition of the methoxy (OMe) moiety on the central
Chalcone and its derivatives have been known to exhibit
antimicrobial, antitumor, anti-HIV, antimalarial, anti-inflam-
matory, and anticarcinogenic activities [1–6]. e ꢀ,ꢁ-
unsaturated ketone (C=C-C=O) moiety in the chalcone
structure plays an important role in chalcone derivative
compounds’ biological activities. Selvi and coworkers (2012)
found that most of these biological effects are related to the
ability to create an electrophilic site that is then able to act as
a binding site for biological targets [7].
Apart from the biological activities, the photophysical
properties of chalcone derivatives also attracted considerable
attention from both chemists and physicists. For example,
chalcone derivatives have been reported in relation to non-
linear optics (NLO), photorefractive polymers, holographic
recording materials, and fluorescent probes for the sensing

2
Journal of Chemistry
R
Series
1
Compound
R
H
H
OCH3
R1
H
OH
H
R1
R
O
O
1a
1b
2a
O
OH−
EtOH
R1
+ 2
O
R1
2
R
2b
OCH3 OH
R
O
Scheme 1: Synthesis of bis-chalcones 1a−2b.
phenyl ring. is work provides another way to improve the
emission efficiency of chalcone related compounds apart
from using the complexation method as reported by D’Ale´o et
al. (2012). Compounds 1a and 1b were reported by a number
of researchers; however, the compounds were mainly used as
a starting material for other compounds’ synthesis and also
were studied concerning their biological activities [18–25],
yet, the photophysical properties of 1a and 1b were not the
main concern in these papers.
ethanol. e mixture was stirred for 5 min and added to
10 mL ethanolic solution of terephthaldehyde for the syn-
thesis of bis-chalcones 1a and 1b (0.67 g, 5 mmol) or
2,5-dimethoxyterephthaldehyde for the synthesis of bis-
chalcones 2a and 2b (0.20 g, 1 mmol). e mixture was stirred
vigorously for 24 h at room temperature. en, HCl (3.0 M)
was added dropwise until the mixture solution was neutral-
ized. e precipitated solid was filtered and then washed with
ethanol and hot water and dried under reduced pressure.
e solid was purified via recrystallization from the slow
diffusion of hexane into the DCM solution.
2. Materials and Methods
3-[4-(3-Oxo-3-pheylpro-penpyl)-phenyl]-1-phenyl-propenone,
1a [18–24, 30]. Yellow solid. Yield: 1.58 g, 93%. M.P.: 193.7–
195.4∘C. IR (KBr, cm−1): 1655 (vC=O), 1606 (vC=C), 1579 and
2.1. Characterizations. Melting point was measured using
open capillary in Stuart MP3 melting point apparatus.
UV-Vis spectra were recorded in dichloromethane (DCM)
or dimethyl sulfoxide (DMSO) solution with a Jasco V-
630 ultraviolet spectrophotometer. Infrared spectra were
recorded on KBr discs using ermo Scientific Nicolet iS10
Fourier-Transform Infrared Spectrophotometer in the range
1445 (vC=C, aromatic ring). 1H-NMR (500 MHz, CDCl ) ꢃ:
3
8.02 (d, 4H, J = 8 Hz, Ar-H), 7.80 (d, 2H, J = 16 Hz, CH=CH ,),
ꢁ
7.68 (s, 4H, Ar-H), 7.59 (t, 2H, J = 6 Hz, Ar-H), 7.57 (d, 2H,
J = 16 Hz, CH =CH), 7.51 (t, 4H, J = 7 Hz, Ar-H), 6.96 (t,
ꢂ
1
of 4000–370 cm−1 at room temperature. e H and 13C-
2H, J = 7 Hz, Ar-H). 13C-NMR (125 MHz, CDCl ) ꢃ: 189.9,
3
NMR spectra were recorded on a JEOL 500 MHz-NMR spec-
143.5, 138.0, 136.8, 133.0, 129.0, 128.7, 128.5 and 123.0. UV-Vis
trometer using DMSO-d and CDCl which were set at 2.50
6
3
(DCM) (ꢂmax/nm): 270 and 348. Anal. Cal. for C H O : C,
24 18
2
and 7.25 ppm as standard reference of the solvent. Elemental
analyses were performed using a ermo Scientific FLASH
2000 HT Elemental Analyser operated by Eager 300 sofware.
X-ray measurements for compound 1b were performed
on a Bruker SMART diffractometer equipped with a graphite
monochromated Mo Ka (ꢂ = 0.71073) radiation source and
a CCD detector. Frame integration was performed using the
program SAINT [28]. e structure was resolved using a
direct method provided by the program package SHELXTL-
97 and refined using full matrix least square against F2 for
all data [29]. All nonhydrogen atoms were refined anisotrop-
ically. All hydrogen atoms were introduced at idealized
positions and were allowed to refine isotropically.
85.18; H, 5.36; Found: C, 85.23; H, 5.37.
1-(2-Hydroxyphenyl)-3-{4-[3-(2-hydroxyphenyl)-3-oxo-pro-
penyl]-ꢄꢅℎꢆꢇꢈꢉ-propenone, 1b [25, 30]. Yellow solid. Yield:
1.45 g, 80%. M.P.: 235.4–236.9∘C. IR (KBr, cm−1): 3450 (vOH),
1638 (vC=O), 1606 (vC=C), 1567 and 1486 (vC=C, aromatic
ring). 1H-NMR (500 MHz, CDCl ) ꢃ: 12.74 (s, 2H, OH), 7.93
3
(d, 2H, J = 8 Hz, Ar-H), 7.92 (d, 2H, J = 15 Hz, CH=CH ), 7.73
ꢁ
(s, 4H, Ar-H), 7.71 (d, 2H, J = 15 Hz, CH =CH), 7.51 (t, 2H,
ꢂ
J = 6 Hz, Ar-H), 7.04 (d, 2H, J = 8 Hz, Ar-H), 6.97 (t, 2H, J =
7 Hz, Ar-H). 13C-NMR (125 MHz, DMSO-ꢊ6) ꢃ: 193.5, 143.5,
161.8, 143.7, 136.7, 136.4, 130.9, 129.7, 123.0, 120.8, 119.2 and
117.8. UV-Vis (DCM) (ꢂmax/nm): 285 and 383. Anal. Cal. for
C H O : C, 77.82; H, 4.90; Found: C, 77.85; H, 4.73.
24 18
4
2.2. Quantum Yield and Lifetime Measurements of Compound
2a. e fluorescence quantum yield of 2a in DCM solution
was measured using a calibrated integrating sphere (inner
diameter: 150 mm) from Edinburgh Instruments FLSP920
spectrometer. e lifetime of this compound was recorded
in FLS980 spectrometer using time-correlated single-photon
counting (TCSPC) method. e DCM solution of compound
2a was excited with pulsed laser diode at the wavelength of
376 nm in the lifetime measurement.
3-[4-(3-Oxo-3-pheylpropenpyl)-phenyl]-2,5-dimethoxyphenyl-
propenone, 2a. Yellowish green solid. Yield: 0.36 g, 80%. M.P.:
242.1–243.8∘C. IR (KBr, cm−1): 1639 (VC=O), 1577 (VC=C),
1564 & 1484 (VC=C, aromatic ring), 1180 (VOCH ). 1H-NMR
3
(500 MHz, DMSO-d6) ꢃ: 8.06 (d, 2H, J = 16 Hz, CH=CH ),
ꢁ
8.03 (d, 4H, J = 7 Hz, Ar-H), 7.72 (s, 2H, Ar-H), 7.67 (d, 2H, J =
16 Hz, CH =CH), 7.60 (t, 4H, J = 8 Hz, Ar-H), 7.53 (t, 2H, J =
ꢂ
8 Hz, Ar-H), 7.16 (d, 2H, J = 8 Hz, Ar-H), 3.96 (s, 6H, OCH ).
3
13C-NMR (125 MHz, DMSO-d6) ꢃ: 189.9, 152.8, 138.1, 133.3,
129.4, 129.0, 127.1, 123.7, 111.7, 110.6 and 57.3. UV-Vis (DCM)
(ꢂmax/nm): 268, 333 and 421. Anal. Cal. for C H O : C,
2.3. General Preparation Procedures of Bis-Chalcones 1a–2b.
10 mL of 10% KOH was added to a 125 mL conical flask that
contained a solution of R-acetophenone (2 eq. mol) [where
R = H (1a and 2a) and ortho-OH (1b and 2b)] in 20 mL
26 22
4
78.37; H, 5.57; Found: C, 77.75; H, 5.54.

Journal of Chemistry
3
76.8
74
72
70
68
66
64
62
60
58
56
54
52
50
48
469
561
692
503
867
1129
658
1234
1416
1438
1151
980
2930
3065
1271 1179 1026
1301
1368
1606
828
1341
758
3450
1486
1638
1208
1567
1578
46
45.0
4000.0 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 600 370.0
(cm−1
)
Figure 1: IR spectrum of compound 1b.
1-(2-Hydroxyphenyl)-3-{4-[3-(2-hydroxyphenyl)-3-oxo-pro-
penyl]-2,5-ꢊꢋꢌℎꢍꢅꢎꢏꢇꢄꢅℎꢆꢇꢈꢉ-propenone, 2b. Orange solid.
Yield: 0.36 g, 76%. M.P.: 252.6–253.4∘C. IR (KBr, cm−1): 3449
(vOH), 1633 (vC=O), 1578 (vC=C), 1561 and 1489 (vC=C,
aromatic ring), 1197 (vOCH ). 1H-NMR (500 MHz, CDCl )
(H ) with the coupling constant (J) value of 15-16 Hz (Fig-
ꢁ
ure 2). e large J value of these two protons clearly indicates
that compounds 1a–2b are in the trans-conformation. For the
13C-NMR spectrum, the carbonyl carbon (C=O) of the bis-
chalcones usually appears at the region of 189.9 to 194.1 ppm.
e presence of 2ꢀ-hydroxyl group at the wing phenyl rings
shifed the carbon resonance of C=O from 190 ppm for
compound 2a downfield by 4 ppm at 194 ppm for compound
2b. is is due to the formation of hydrogen bond in between
the 2ꢀ-hydroxyl and oxygen in the carbonyl groups.
3
3
ꢃ: 12.74 (s, 2H, OH), 7.93 (d, 2H, J = 8 Hz, Ar-H), 7.92 (d, 2H,
J = 15 Hz, CH=CH ), 7.73 (s, 2H, Ar-H), 7.71 (d, 2H, J = 15 Hz,
ꢁ
CH =CH), 7.51 (t, 2H, J = 6 Hz, Ar-H), 7.04 (d, 2H, J = 8 Hz,
ꢂ
Ar-H), 6.96 (t, 2H, J = 6 Hz, Ar-H). 13C-NMR (125 MHz,
CDCl ) ꢃ: 194.1, 163.6, 153.4, 140.1, 136.4, 129.7, 126.6, 122.4,
3
120.2, 118.8, 118.6, 112.2 and 56.3. UV-Vis (DCM) (ꢂmax/nm):
3.2. X-Ray Crystallography of Bis-Chalcone 1b. e molecular
structure of bis-chalcone 1b was previously reported by Gaur
and Mishra in 2013 [25]. e yellow crystal of bis-chalcone
1b was grown in DCM solution via slow diffusion in hexane
under ambient conditions. e molecular structure of bis-
chalcone 1b is shown in Figure 3 and the main crystallo-
graphic parameters are presented in Table 1. Bis-chalcone 1b
crystallized into monoclinic crystal system with the space
275, 350 and 445. Anal. Cal. for C H O : C, 72.55; H, 5.15;
Found: C, 71.79; H, 4.95.
26 22
6
3. Results and Discussion
3.1. Spectroscopic Analyses. e formation of bis-chalcones
can be represented by the presence of ꢀ,ꢁ-unsaturated ketone
(C=C-C=O) bands at 1633–1665 cm−1 for C=O and 1577–
1606 cm−1 for C=C in the IR spectra. e IR frequency of
C=O group is lower than the typical value (ca. 1700 cm−1)
because of the conjugation effect along the C=C-C=O moiety.
e presence of the electron donor and acceptor at the para-
and ortho-positions of the wing phenyl rings shifed the
energy of the carbonyl group and C=C aliphatic group. For
example, for bis-chalcone 1a, the C=O band was present at
the frequency of 1655 cm−1, but a lower frequency of C=O
band (ca. 1638 cm−1) was observed in bis-chalcone 1b, which
has ortho-OH as the substituent (Figure 1). In addition, the
presence of methoxy (OMe) substituent on the central phenyl
ring also shifs the IR frequency of C=C in bis-chalcones 2a
and 2b (1583–1578 cm−1) to a lower frequency compared to
compounds 1a and 1b (1606 cm−1). is is due to the electron
˚
group of P2 /ꢆ. e bond length of C6-C7 is about 1.325 A,
1
˚
which is close to the typical C=C bond (1.34 A). e single
bonds of C4-C5, C5-C6, and C7-C8 are in the range of
˚
1.459–1.467 A, which is relatively shorter than the typical
˚
single bond (1.54 A). is is due to the fact of the conju-
gated system present along the molecule [31]. On the other
hand, supporting the discussion of the 13C-NMR above, the
molecular structure of bis-chalcone 1b shows the presence of
intramolecular hydrogen bond in between phenolic hydro-
gen and the oxygen atom at C=O.
3.3. Photophysical Studies on Bis-Chalcone Compounds. e
photophysical data of bis-chalcones 1a–2b are shown in
Table 2, and the absorption spectra of bis-chalcones 1a and
2a in DCM are shown in Figure 4.
Two absorption bands located at 268–278 nm and 333–
383 nm were observed in bis-chalcones 1a–2b; however,
for bis-chalcones 2a-2b, an additional absorption band
was observed at about 421 nm, which corresponded to
donation from OCH group to the C=C aliphatic moiety
3
which consequently weakens the C=C bond.
e H and H protons of bis-chalcone appear as two
ꢂ
ꢁ
doublets in the ranges of 7.6–8.2 ppm (H ) and 7.5–7.8 ppm
ꢂ

4
Journal of Chemistry
5.0
4.0
3.0
2.0
1.0
0
13.0
12.0
11.0
10.0
9.0
8.0
7.0
6.0
5.0
Figure 2: 1H NMR spectrum of compound 1b.
O2
C3
O1
C5
C12
C7
C10
C9
C11
C1
C2
C4
C6
C8
C2
C8
C6
C4
C1
C9
C11
C10
C7
C3
C5
O1
O2
C12
Figure 3: Molecular structure of bis-chalcone 1b with the thermal ellipsoids plotted at 50% probability.
intramolecular charge transfer (ICT) from an ethylenic ꢐ
electron to a carbonyl ꢐ electron [31, 32]. e absorption
band at the range of 268 to 278 nm corresponded to the
the molecule [31]. Similar phenomena of absorption spectra
were also found in the papers reported by Si and his
coworkers in 2011 [13] and Tay et al. [33]. In the bis-chalcones
reported by Si et al., they claimed that the increase of the
absorption band 259 nm and the decrease of the band at
341 nm resulted from the [2ꢐ + 2ꢐ] cycloaddition of the
double bond in the chalcone unit to give a cyclobutane ring
[13].
∗
ꢐ ꢑ ꢐ transition in the aromatic ring. e absorption of this
transition normally appears at around 200–250 nm; however,
due to the conjugation effect of the carbonyl group and the
carbon-carbon double bond system with the aromatic ring,
∗
the ꢐ ꢑ ꢐ transition was shifed to a longer wavelength.
e presence of ortho-hydroxyl group at the wing phenyl
e emission spectra of bis-chalcones 1a-1b and 2a-2b are
∗
∗
rings has shifed the ꢐ ꢑ ꢐ and ꢆ ꢑ ꢐ transitions in
compounds 1b and 2b to a lower energy region (a longer
wavelength). is is because the electron donating nature of
the hydroxyl group has weakened the bond order of C=C and
shown in Figure 5. e emissions ꢂ
of bis-chalcones 2a
max
and 2b were shifed to a lower energy afer the addition of
the OMe group on the central phenyl ring. In general, bis-
chalcone compounds 1a, 1b, and 2b exhibited weak emission
as seen in the low signal versus noise emission spectra. Due
to this reason, we could not obtain the quantum yields and
lifetimes of these compounds even in less polar solvents, that
is, DCM. e quenching process in chalcones is normally due
to intramolecular torsional motions as well as the cis-trans
isomerization of the ꢀ,ꢁ-unsaturated ketone moiety [15, 16].
However, for compounds 1b and 2b, quenching could also
∗
C=O groups. Surprisingly, the ꢆ ꢑ ꢐ transition (ꢒ = ca.
22,000–26,000 mol−1 cm−1 dm3) is much stronger than the
∗
ꢐ ꢑ ꢐ transition (ca. 9,700–15,000 mol−1 cm−1 dm3) in all
the reported bis-chalcone compounds. is phenomenon can
be explained by the presence of extended conjugation C=C-
C=O chromophoric system in the bis-chalcone structure,
which resulted in greater delocalization of ꢐ electrons along

Journal of Chemistry
5
0.07
0.06
0.7
0.6
348.5 nm
333nm
n ꢁ ꢀ∗
421nm
n ꢁ ꢀ∗
ICT
ꢀ ꢁ ꢀ∗
268nm
0.04
0.4
0.2
0
ꢀ ꢁ ꢀ∗
270.5 nm
0.02
0
250
300
350
400
250
300
400
Wavelength (nm)
500
600
Wavelength (nm)
Figure 4: Absorption spectrum of bis-chalcones 1a (top) and 2a (bottom) in DCM.
Table 1: Summary of crystal data and structure refinement param-
eters of bis-chalcone 1b.
the singlet excited state. Comparing bis-chalcone 1a, the
emission efficiency of bis-chalcone 2a improves when there
is an OMe group on the central phenyl ring. Chalcone and
related compounds are generally known as poor emitters. e
introduction of an OMe group on the central phenyl ring in
compound 2a is considered another method to improve the
emission efficiency of chalcone compounds apart from the
method reported by D’Ale´o and his coworkers (2012) [17].
Compound
1b
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
C H O
370.38
24 18
4
296(2)
Monoclinic
P2 /n
1
3.4. Solvatochromism Study of Bis-Chalcone 2a. e solva-
tochromism study of bis-chalcone 2a was performed by
dissolving the compound in the following solvents: benzene,
tetrahydrofuran (THF), DCM, and acetonitrile (MeCN). e
˚
ꢓ (A)
4.9841(10)
27.0759(7)
6.9770(2)
90.00
˚
ꢔ (A)
˚
ꢕ (A)
ꢀ (∘)
ꢁ (∘)
emission ꢂ
changed from 499 nm (blue) in benzene to
523 nm (yelmloaxwish green) in MeCN (Figure 6), which indi-
cates that the excited molecule of bis-chalcone 2a has inter-
molecular interaction with the polar solvent molecules. It is
believed that intramolecular charge transfer occurred from
the OMe group on the central phenyl ring towards both sides
of the phenyl rings.
101.37(2)
90.00
ꢖ (∘)
3
˚
Volume (A )
923.05(4)
ꢗ
2
Density (calculated) (mg/m3)
Absorption coefficient (mm−1
Θ range for data collection (∘)
Reflections collected
1.333
)
0.090
3.07 to 25.87
2111
4. Conclusions
A method to improve the emission efficiency of bis-chalcone
has been found. By adding a methoxy group at the central
phenyl ring of bis-chalcone, the quantum yield of bis-
chalcone2a was improved to 0.57 in DCM solution, and it was
still emissive (Φꢃ = 0.40) in acetonitrile using Coumarin 307
as the reference. A solvatochromism study of bis-chalcone 2a
was performed and the emission ꢂmax increased from 499 nm
in benzene to 523 nm in MeCN.
Independent reflections
Data/restraints/parameters
1546
2111/0/129
ꢘ1 = 0.0394
Final ꢘ indices [ꢙ ꢚ 2ꢛ(ꢙ)]
ꢜꢘ2 = 0.1164
ꢘ1 = 0.0565
ꢘ indices (all data)
ꢜꢘ2 = 0.1326
be due to the intramolecular hydrogen bond, which can be
observed from the molecular structure of 1b in Figure 3.
Interestingly, bis-chalcone 2a was found to be highly
emissive at 505 nm with a quantum yield of 0.57 as well as life-
times of 2.44 and 4.04 ns in DCM solution. Apart from DCM,
this compound also shows intense emission in polar solvents,
that is, acetonitrile. e quantum yield in acetonitrile was
0.40 using Coumarin 307 as the reference [26, 27]. e
nanosecond lifetime indicates that emission originates from
Competing Interests
e authors declare that they have no competing interests.
Acknowledgments
e authors wish to thank the Ministry of Higher Educa-
tion, Malaysia, for the Fundamental Research Grant Scheme
[FRGS/SG01(01)/1067/2013(13)] for the financial support of

6
Journal of Chemistry
Table 2: Photophysical data for compounds 1a to 2b in solution state at room temperature.
Compound
ꢂ
a /nm (ꢒ/104 M−1 cm−1
270 (0.970)
348 (2.228)
278 (0.979)
383 (2.369)
268 (1.519)
)
ꢂ
em/nm
Φꢃ
ꢝꢃ/ns
Stokes shife/cm−1
abs
b
b
∼430
—
—
5500
1a
b
b
∼432
—
—
3000
1b
c
505
0.57
2.44 (15%)
4.04 (85%)
10200
d
2a
2b
333 (2.662)
421 (2.384)
275 (1.385)
350 (2.164)
445 (2.576)
0.40
b
b
b
—
—
—
—
aAll the UV data was recorded in DCM solution. bNot able to be determined due to very poor emission. cFluorescence quantum yield which was measured
in DCM solution using an integrating sphere. dFluorescence quantum yield which was measured in acetonitrile solution using Coumarin 307 as a reference
[26, 27]. eStokes shif was calculated based on ꢄmax abs − ꢄmax em.
1.2
1
1.2
1
0.8
0.6
0.4
0.2
0
0.8
0.6
0.4
0.2
0
390
440
490
540
590
640
690
350
400
450
500
550
Wavelength (nm)
Wavelength (nm)
1a
1b
2a
2b
Figure 5: Emission spectra of compounds 1a-1b (top) and 2a-2b (bottom) in DMSO.
1.2
1
0.8
0.6
0.4
0.2
0
450
500
550
600
650
Benzene THF
MeCN
DCM
Wavelength (nm)
Benzene
THF
DCM
MeCN
Figure 6: Solvatochromism study of bis-chalcone 2a.

Journal of Chemistry
7
this work. Mee Hing Tiong thanks the funding from MyBrain
15 Program for supporting his Master Scholarship. Meng
Guan Tay and Ying Ying Chia would like to thank Jo¨rn Nitsch
from the Julius-Maximilians-Universita¨t Wu¨rzburg for his
help in measuring the quantum yield and lifetime of 2a. Last
but not least, the authors also would like to thank Dr. Andrew
Crawford for proofreading this paper.
Research on Chemical Intermediates, vol. 37, no. 6, pp. 635–646,
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