A Single-Benzene-Based Fluorophore: Optical Waveguiding in the Crystal Form

Article abstract of DOI:10.1002/cplu.201900405

A single-benzene-based, blue-emissive diethyl 2,5-dihydroxyterephthalate (DDT) was prepared by Fischer esterification of 2,5-dihydroxyterephthalic acid (DHT) and ethanol. The strong fluorescence in both the solution and the solid state from such a simple framework stemmed from the push-pull structure of the electron-donating hydroxy groups and the accepting carbonyl groups, as well as structural planarity from intramolecular hydrogen bonds. The strong intermolecular hydrogen bonds enabled DDT to crystallize easily. The color CCD imaging technique showed efficient 1D optical waveguiding with a large optical loss coefficient of 0.15 dB/μm. DDT has potential application in optical sensors, photonic devices, and optoelectronic communication, because of its highly ordered structure and light-emitting ability.

Full text of DOI:10.1002/cplu.201900405

Accepted Article
Title: Single benzene-based fluorophore and optical waveguiding in its
crystal
Authors: Eunbee Cho, Jinho Choi, Seonyoung Jo, Dong-Hyuk Park,
Young Ki Hong, Dongwook Kim, and Taek Seung Lee
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: ChemPlusChem 10.1002/cplu.201900405
Link to VoR: http://dx.doi.org/10.1002/cplu.201900405
A Journal of
www.chempluschem.org

10.1002/cplu.201900405
ChemPlusChem
FULL PAPER
Single Benzene-Based Fluorophore and Optical Waveguiding in
Its Crystal
Eunbee Cho,+[a] Jinho Choi,+[b] Seonyoung Jo,[a] Dong-Hyuk Park,*[b] Young Ki Hong,*[c] Dongwook
Kim,[d] and Taek Seung Lee*[a]
Abstract:
A
single benzene-based, blue-emissive diethyl 2,5-
considered to be important in designing highly fluorescent molecules.
The strong intramolecular interaction allows the molecules to have a
planar structure and to generate an extended π-conjugated system
in the molecule, leading to high fluorescence.[12-14] In addition, strong
intermolecular interactions play an important role in fluorescence via
charge transfer.[15] Substituents in benzene that could induce
intramolecular hydrogen bonding often result in an effective emission
via an excited-state intramolecular proton transfer (ESIPT).[12,16,17] In
addition, it has been reported that fluorescence depends on the
packing structure of the fluorescent molecules. In general, most π-
conjugated molecules have limited fluorescence in their solid state
because the strong π-π interaction causes unexpected quenching,
known as aggregation-caused quenching (ACQ).[18-20] To supress
ACQ, it was reported that the intramolecular hydrogen bond was
introduced to lessen the ACQ to some degree, exhibiting desirable
fluorescence.[14,21] Therefore, the high fluorescence would be
maintained in the solid state, as long as the intramolecular
interaction is carefully controlled.
dihydroxyterephthalate (DDT) was prepared by Fischer esterification
of 2,5-dihydroxyterephthalic acid (DHT) and ethanol. The strong
fluorescence in both the solution and the solid state from such a
simple structure stemmed from the push-pull structure of the
electron-donating hydroxyl groups and the accepting carbonyl
groups, as well as structural planarity from intramolecular hydrogen
bonds. The strong intermolecular hydrogen bonds enabled DDT to
crystallize easily. The color CCD imaging technique showed efficient
1D optical waveguiding with a large optical loss coefficient of 0.15
dB/m, which has a potential application in optical sensor, photonic
device, and optoelectronic communication, because of its highly
ordered structure and light-emitting ability.
Introduction
Organic fluorescent molecules have attracted much interest because
of their potential applications in various fields such as optoelectronic
devices, bioimaging, and chemical sensors.[1-7] Benzene is one of
the effective units that form a π-conjugated system in an organic
fluorophore, and more than one benzene ring is required to extend
the π-conjugation length for visible light emission. However, organic
fluorophores with such a large conjugation usually have limited
solubility in common organic solvents.[8] As such, emissive small
molecules based on a single benzene have the advantage of high
solubility and easy synthesis because of their simple chemical
structures.
New communication techniques and devices can be created
using photons as information carrier manipulated at micro-to-nano
scale.[22,23] Organic materials are advantageous over conventional
inorganic materials in such fields, because of their cost-effectiveness,
easy molecular modification, flexibility and lightweight.[24] To attain
transmitting light both in active and passive modes, organic
materials should have highly ordered, crystalline structure to
transport photonic carriers.[25,26]
Herein, we synthesized DDT and its derivatives to investigate
their optical properties and optical waveguiding application. DDT had
two hydroxyl groups that were hydrogen-bonded inter- and
intramolecularly with carbonyl groups. The hydroxyl and carbonyl
groups acted as electron-donating and -withdrawing groups in the
benzene ring, respectively, affecting the high fluorescence of DDT.
The intramolecular hydrogen bond provided enhanced ring planarity,
resulting in the delocalization of electrons. It was revealed that the
presence of hydroxyl groups was essential for the fluorescence of
DDT, and thus this fluorescence of DDT was easily altered by the
protection and deprotection of the hydroxyl groups. It was found that
Benzene is
a simple structure so that its fluorescence
emission can be tuned depending on the substituents attached to
the single benzene.[9,10] For example, the presence of electron-
donating and -withdrawing groups in the benzene ring provided a
strong fluorescence by extending the π-conjugation induced by the
push-pull structure.[11] In addition, intra- and intermolecular
interactions including hydrogen bonding and the  interaction are
[a]
E. Cho, S. Jo, Prof. T. S. Lee
Organic and Optoelectronic Materials Laboratory, Department of
Organic Materials and Textile System Engineering, Chungnam
National University, Daejeon 34134, Korea
E-mail: tslee@cnu.ac.kr
[b]
[c]
[d]
J. Choi, Prof. D. –H. Park
Department Department of Applied Organic Materials Engineering,
Inha University, Incheon 22212, Korea
E-mail: donghyuk@inha.ac.kr
Prof. Y. K. Hong
Department of Physics, Gyeongsang National University, Jinju
52828, Korea
E-mail: ykhong@gnu.ac.kr
Prof. D. Kim
Department of Chemistry, Kyonggi University, Suwon 16227, Korea
+ These authors contributed equally.
Scheme 1. Synthesis of DDT and its derivatives. Inset photographs
Supporting information for this article is given via a link at the end of
the document.
were taken in their chloroform solutions under UV lamp (365 nm).
This article is protected by copyright. All rights reserved.

10.1002/cplu.201900405
ChemPlusChem
FULL PAPER
DDT easily and facilely crystallized, in which strong intermolecular
interactions including the - interaction and the hydrogen bond
between the molecules played an important role in crystal packing.
The resulting DDT crystal could serve as efficient 1D waveguide,
which can transmit light in active mode, because of the unique
optical property in its crystal form. It has been also reported that the
push-pull structure in a benzene ring including DDT was able to
of DDT did not originate from ESIPT. The fluorescence of ESIPT-
active molecules should vary according to the solvent polarity,
because of the alteration in intramolecular hydrogen bonding.[17,29,30]
The UV-vis spectra of DHT showed absorption at 375 nm,
similar to that of DDT (Fig. 1c). However, the fluorescence spectra of
DHT varied according to the solvent used (Fig. 1d). DHT showed
short wavelength emission (452 nm) in THF, but a distinctive long
wavelength emission was observed around 510 nm in DMF and
DMSO, which had higher dipole moments (3.96 and 3.86 D,
respectively) than THF (1.75 D). Moreover, the fluorescence spectra
in protic solvents such as ethanol and methanol differed from THF
and DMF, because the intramolecular hydrogen bond of DHT was
disturbed in the protic solvents. Thus, it might be concluded that
unlike DDT, the fluorescence of DHT dominantly resulted from
ESIPT.[31] The same phenomenon of ESIPT was found in salicylic
acid, which has half the DHT structure (a hydroxyl and a carboxylic
acid groups).[32] To ensure that the fluorescence of DDT was not
related to ESIPT, trifluoroacetic acid (TFA) was added to DDT to
protonate the hydroxyl groups of DDT in THF, indicating negligibly
small changes in UV-vis absorption and emission shift of DDT (Fig.
S1). Therefore, it was evident that ESIPT did not occur in the DDT
molecule.[16] 2,5-Bis(methylsulfonyl)-1,4-diaminobenzene showed
green emission that resulted from a push-pull structure, assisted by
an intramolecular hydrogen bonding interaction.[33] As such, we
supposed that DDT showed efficient fluorescence based on the
provide
strong
fluorescence
based
on
X-shaped
simple
tetrafunctionalities.[27]
They, however,
investigated
spectroscopic properties of DDT including UV-vis absorption,
emission, and fluorescence lifetime, because they thought that
stronger electron-donating diamine compound was more attractive
than DDT. We were to investigate the detailed origin of DDT
fluorescence in various solvents. Moreover, we conjectured such
hydroxyl groups would be helpful in rapid crystallization via
intermolecular hydrogen bond.
Results and Discussion
A blue-emissive fluorophore, DDT, was synthesized by the Fischer
esterification of DHT with ethanol (Scheme 1). After recrystallization
from ethanol, the synthesized DDT was a highly emissive needle-like
crystal. DDT has been reported as the intermediate for oxadiazole
derivatives, but its optical properties have been rarely studied.[28] To
investigate the main cause of fluorescence in DDT, the
spectroscopic properties of DDT were compared with those of DHT,
which was similar to DDT in structure, having two hydroxyl groups
adjacent to carbonyl groups, but DHT had carboxylic acid groups.
DDT showed UV absorption around 365 to 378 nm in various
solvents used, but the fluorescence emission was shown at 451 nm,
in which the solvent effect was not observed (Fig. 1a,b). No
significant difference in the emission wavelengths of DDT was found
in organic solvents with different polarity and thus the fluorescence
push-pull system by the presence of electron-donating and
-
withdrawing groups. DDT has two hydroxyl groups acting as donors
and two carbonyl groups acting as acceptors, which would meet the
requirement of the push-pull system in a single benzene.
To investigate the effect of the electron push-pull structure on
the optical properties of DDT, the optimized structures in the ground
and excited states were obtained by density functional theory (DFT)
calculations at the B3LYP/6-31G(d) level. DDT had a structure in
which electrons were mainly located in the central benzene ring in
the highest occupied molecular orbital (HOMO) level and were
evenly distributed throughout the molecule in the ester groups in the
lowest unoccupied molecular orbital (LUMO) level (Fig. S2a). The
HOMO-LUMO structure suggests that the push-pull system occurred
in a benzene ring. On the while, ethyl salicylate, which has half the
DDT structure (one hydroxyl and one ester group) showed intense
fluorescence, and its fluorescence varied according to the solvents
with different polarity (Fig. S3). The changes in the DDT
fluorescence were investigated to verify the presence of the
Fig. 2. (a) Fluorescence spectra and (b) photographs of DDT in chloroform
solution, film, and crystal (from left to right). Photographs were taken under UV
irradiation (365 nm).
Fig. 1. (a) UV-vis and (b) fluorescence spectra of DDT and (c) UV-vis and
(d) fluorescence spectra of DHT in various solvents. [DDT] = 0.07 mM;
[DHT] = 0.05 mM.
This article is protected by copyright. All rights reserved.

10.1002/cplu.201900405
ChemPlusChem
FULL PAPER
substitution effect of the hydroxyl groups. DDT-A and DDT-T were
synthesized, in which the hydroxyl groups were protected with the
acetyl and tert-butyloxycarbonly (t-Boc) groups, respectively
(Scheme 1). Upon protection, the UV-vis absorption was blue-shifted
(Fig. S4a) and the fluorescence of DDT-A and DDT-T was hardly
observed in the solutions (inset photographs in Scheme 1 and Fig.
S4b), and the relative quantum yields (QYs) of DDT-A and DDT-T
were found to be much lower than that of DDT (Table S1). It is
suggested that the hydroxyl groups were essential for the
fluorescence of DDT via electron-donation and intramolecular
hydrogen bonding. To strengthen electron-donating ability of the
hydroxyl groups in DDT, deprotonation from the hydroxyl groups was
performed using tetrabutylammonium fluoride (TBAF). The emission
wavelength was shifted to longer wavelength (562 nm) by the
formation of O– group (DDT-F-), which became a stronger donor in
the benzene ring (Fig. S5). Taking into account that the electron-
donating ability of oxygen anion is much higher than that of hydroxyl
group,[34,35] the long-wavelength emission band in DDT-F- could be
attributed to its phenolate anion species via facilitated intramolecular
charge transfer, as reported earlier.[36]
synthesized using the same method for DDT. As the number of alkyl
groups did not affect the electron-withdrawing ability of the ester
groups, the absorption and emission spectra of DT-Cn were the
same as those of DDT in chloroform (Fig. S6 and Table S2). The
electron distribution, band gap, and HOMO-LUMO levels of DT- C6
were almost identical to those of DDT, indicating that the effect of
the number of alkyl groups on optical properties was negligible (Fig.
S2b). DT-Cn crystals, however, tended to show a red shift in the
fluorescence emission wavelength, compared with those in solution
and film state (Fig. S6). It should be noted that such a red shift of the
emission wavelength became larger with a smaller n and was
maximized in DDT (25 nm of red shift). Among these derivatives,
DDT showed most rapid crystallization with largest crystal size. It
suggests that the alkyl group affected the crystal packing and, finally,
on the fluorescence wavelength of their crystals (Table S2).
DDT exhibited various fluorescence wavelengths depending
on its states including solution, film, and crystal, in which the blue
fluorescence was observed in its solution and film and greenish blue
emission was found in its crystal (Fig. 2). It appears that the red shift
of the fluorescence of crystalline DDT resulted from the
planarization-induced intermolecular interaction of the rings. To
verify the planarization, the crystal structure of DDT was determined
using a single crystal diffractometer (Fig. 3 and Table S3). DDT had
intramolecular hydrogen bonds (H3-O2; bond length: 1.906 Å)
between the oxygen atom at the carbonyl group and the hydrogen
To elucidate the effect of alkyl chain length of ester groups,
various numbers of alkyl groups were introduced to the C=O groups
in DDT. Dibutyl- (DT-C4), dihexyl- (DT-C6), dioctyl- (DT-C8), didecyl-
(DT-C10), and didodecyl 2,5-dihydroxyterephthalate (DT-C12) were
Fig. 4. Planar optical wave-guiding effects in 1D DDT crystal (designated
as solid rectangle). (a) Color CCD images of unguided and five
waveguided emissions in 1D DDT crystal with various distinct propagation
distances. Circled numbers denote incident laser positions, and dashed
ellipse indicates detector positions where guided PL spectra were
measured. Inset: Optical microscope image of the 1D DDT crystal. (b)
Comparison of unguided (black line) and waveguided fluorescence spectra
from (a). The unguided black line was out of range, but illustrated for
comparison. (c) Intensity ratio including single exponential fitting curve with
respect to the propagation distance. Excitation wavelength = 405 nm.
Fig. 3. Crystal structure of DDT: top view (a); molecular packing
structures along the crystallograpic b axis (b); and between b and c
axes. CCDC 128054 (DDT) contains the crystallographic data for this
paper. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre.
This article is protected by copyright. All rights reserved.

10.1002/cplu.201900405
ChemPlusChem
FULL PAPER
atom at hydroxyl group, which affected the planarization of the
molecule.[1] Moreover, strong intermolecular hydrogen bonds (H3-O2
Synthesis of DDT. 2,5-Dihydroxyterephthalic acid(DHT) (5 g, 25
mmol) was dissolved in ethanol (200 mL) charged in a three-necked
flask (500 mL) under argon atmosphere. Sulfuric acid (13 mL, 0.25
mol) was slowly added and then the mixture was stirred at 80 ℃ for
24 h. The mixture was cooled to room temperature and the
precipitate was isolated by filtration. The product was recrystallized
from ethanol. A greenish needle-like crystal was obtained (yield 5.52
in adjacent molecule; bond length: 2.348 Å) provided
a 
interaction-induced high crystallinity and enhanced fluorescence in
the crystalline state. The DDT crystal showed a herringbone packing
structure. The packing structure affected the crystal to have an
absolute QY of 34%, determined with an integrating sphere. It was
already reported that the molecular packing considerably affected
fluorescence efficiency.[37]
1
g, 87 %). H NMR (300 MHz, CDCl3):  = 10.1 (s, 2H), 7.4 (s, 2H),
4.4 (m, 4H), 1.4 ppm (t, 6H).
Different from conventional waveguiding phenomena observed
in optical fiber that satisfy total internal reflection of axially incident
photons, crystalline organic small molecular microstructures
exhibited planar optical waveguiding effects, which normally incident
photons were propagated laterally.37-40 The color CCD images show
optically active fluorescence waveguiding of 1D DDT crystal (Fig.
4a,b and Fig. S7). Bright blue luminescent spots in color CCD
images indicate excitation positions, which were moved from right
edge of the 1D DDT crystal to left designated positions (① to ⑤)
with distances of 2.2, 3.4, 4.6, 5.8, and 7.0 μm, respectively. All the
color CCD images show that internally waveguided photon energies
were re-emitted as pale blue lights at both edges, indicating an
important evidence of planar optical waveguiding effect. For
quantitative comparison, unguided and waveguided fluorescence
spectra were compared (Fig. 4c). The initial unguided fluorescence
spectrum as well as guided spectra (① to ⑤) were observed at
about 465 nm, suggesting that they reflected same emission colors
from the corresponding spots. However, the emission intensity of the
Synthesis of DDT-A. DDT (1 g, 3.9 mmol) was dissolved in
acetonitrile (60 mL) charged in a 100 mL three-necked flask. Acetic
anhydride (1.48 mL, 15.6 mmol) was added to the solution, and the
mixture was stirred at 80 ℃ for 10 min. Cesium carbonate (1.91 g,
5.85 mmol) was added to the mixture and then the mixture was
stirred for
4 h. After cooling, the solution was washed with
chloroform three times and with brine solution, and dried over
MgSO4. The solvent was evaporated to obtain crude product of
DDT-A. The crude product was recrystallized from ethyl acetate. The
colorless diamond-shaped crystal was obtained (yield 1.2 g, 89 %).
1H NMR (300 MHz, CDCl3):  = 7.7 (s, 2H), 4.3 (m, 4H), 2.3 (s, 6H),
1.3 ppm (t, 6H).
Synthesis of DDT-T. To a 250 mL three-necked flask was added
DDT (0.615 g, 2.4 mmol), di-tert-butyl dicarbonate (1.27 g, 5.82
mmol), and tetrahydrofuran (THF, 100 mL). DMAP (15 mg, 0.12
mmol) was added to the solution and then the mixture was stirred
overnight. The solution was poured into water and the precipitate
was isolated by filtration. A white powder was obtained (yield 1.03 g,
guided fluorescence spectra (Iguided
) gradually decreased with
increase in the propagation distances (d). The changes in the
intensity ratio (Iguided / Iunguided) as a function of d including single
exponential fitting curve can be described as: Iguided / Iunguided = Aexp(–
Rd), where A is a constant and R is an optical loss coefficient (Fig.
4d).25,40 The R value was determined to be 0.158 dB/μm, which was
comparable and even better than previous reports on the highly
crystalline organic microstructures (0.9~1.6 dB/mm).[25,26,38-41] The
1
94 %). H NMR (300 MHz, CDCl3):  = 7.8 (s, 2H), 4.3 (m, 4H), 1.5
(s, 18H), 1.4-1.3 ppm (t, 6H).
present work elucidates the related photophysics in
a simple
benzene-based, organic system, providing an important paradigm of
organic integrated photonics.
Synthesis of DT-Cn (n = 4, 6, 8, 10, and 12). DHT (1.0 g, 5.0
mmol) was dissolved in n-butanol (40 mL) for DT-C4 synthesis; in n-
hexanol (50 mL) for DT-C6 synthesis; in n-octanol (60 mL) for DT-C8
synthesis; in n-decanol (50 mL) for DT-C10 synthesis; in n-
dodecanol (70 mL) for DT-C12 synthesis in the presence of sulfuric
acid catalyst. Subsequent procedures are the same as those used
for the DDT synthesis. In the cases of DT-C8, DT-C10, DT-C12, the
crude product was purified by recrystallization from 1-propanol.
Conclusions
In summary, a single benzene fluorophore was prepared,
which showed high fluorescence both in solution and in the solid
state. According to photophysical and DFT studies, the fluorescence
of DDT originated from the presence of functional groups of electron-
withdrawing and -donating. Therefore, the presence of hydroxyl
groups was necessary to provide strong fluorescence of DDT. The
intermolecular hydrogen bonding in DDT was versatile so that DDT
showed rapid crystallization with unique packing, exhibiting strong
fluorescence in the solid state. Such fluorescence from crystallized
DDT showed successful optical waveguiding, indicating that DDT is
a promising candidate for optoelectronic transportation devices
Preparation of DDT crystals. Highly crystalline DDT was fabricated
by using solvent-assisted self-assembly method. Briefly, DDT was
dissolved in THF and the solution was drop-cast on a glass slide. As
vaporizing the solvent at room temperature, the nucleation as well as
self-assembly of DDT molecules occurred resulting in various forms
of DDT crystals. Among them, 1D DDT crystal was chosen to
investigate planar optical waveguiding phenomena.
Experimental Section
This article is protected by copyright. All rights reserved.

10.1002/cplu.201900405
ChemPlusChem
FULL PAPER
[14] Y. Yeo, S. Jo, S. J. Park, H. M. Kim, D. Kim, T. S. Lee, Chem. Commun.
2019, 55, 6747-6750.
Optical Waveguiding. Optical properties of 1D DDT crystal,
including color charge-coupled device (CCD) images and
fluorescence spectroscopy, were measured using a home-made
laser confocal microscope (LCM) system with high spatial resolution
(≤ 200 nm). In order to characterize planar optical waveguiding
effects, the LCM system should be modified as separating the
positions of the incident laser from those of the detector. Especially,
the irradiating positions of the incident laser were precisely
controlled with an aid of the piezoelectric 2D positioning system
(Albatross, Nanofocus Inc.). The excitation wavelength (ex) was set
to 405 nm for both luminescent color CCD images and fluorescence
spectra, which were recorded by GF-033C-IRF (Allied Vision) and
SR-303I-B (Andor), respectively. The power density of the incident
laser was carefully chosen to minimize photobleaching of the crystal
sample.
[15] Y. Zhan, L. Lin, M. Chen, L. Wu, ACS Appl. Mater. Interfaces 2018, 10,
33390-33398.
[16] P. Jagadesan, T. Whittemore, T. Beirl, C. Turro, P. L. McGrier, Chem.
Eur. J. 2017, 23, 917-925.
[17] B. Tang, H. Liu, F. Li, Y. Wang, H. Zhang, Chem. Commun. 2016, 52,
6577-6580.
[18] Y. Hong, J. W. Lam, B. Z. Tang, Chem. Soc. Rev. 2011, 40, 5361-5388.
[19] E. Zhao, Y. Chen, H. Wang, S. Chen, J. W. Lam, C. W. Leung, Y. Hong,
B. Z. Tang, ACS. Appl. Mater. Interfaces 2015, 7, 7180-7188.
[20] A. Mishra, R. K. Behera, P. K. Behera, B. K. Mishra, G. B. Behera,
Chem. Rev. 2000, 100, 1973-2129.
[21] T. Beppu, S. Kawata, N. Aizawa, Y. J. Pu, Y. Abe, Y. Ohba, H. Katagiri,
ChemPlusChem. 2014, 79, 536-545.
[22] R. Yan, D. Gargas, P. Yang, Nat. Photonics 2009, 3, 569-576.
[23] M. Law, D. J. Sirbuly, J. C. Johnson, J. Goldberger, R. J. Saykally, P.
Yang, Science 2004, 305, 1269-1273.
[24] D. O’Carroll, I. Lieberwirth, G. Redmond, Nat. Nanotechnol. 2007, 2,
180-184.
[25] W. Zhu, L. Zhu, Y. Zou, Y. Wu, Y. Zhen, H. Dong, H. Fu, Z. Wei, Q. Shi,
W. Hu, Adv. Mater. 2016, 28, 5954-5957.
Acknowledgements
[26] L. Catalano, P. Commins, S. Schramm, D. P. Karothu, R. Rezgui, K.
Hadef, P. Naumov, Chem. Commun. 2019, 55, 4921-4924.
[27] R. Huang, B. Liu, C. Wang, Y. Wang, H. Zhang, J. Phys. Chem. C 2018,
122, 10510-10518.
Financial support from the National Research Foundation
(NRF) of Korean government through Basic Science Research
Program (2018R1A2A2A14022019) is gratefully acknowledged.
[28] Y. S. Kim, W. H. Park, T. S. Lee, J. Nonlinear. Opt. Phys. 2004, 13,
613-618.
Keywords: benzene-based fluorophore • crystals • fluorescence
[29] M. Tian, J. Sun, Y. Tang, B. Dong, W. Lin, Anal. Chem. 2018, 90, 998-
1005.
spectroscopy • hydrogen bonds • optical waveguiding
[30] T. H. Kim, M. S. Choi, B. H. Sohn, S. Y. Park, W. S. Lyoo, T. S. Lee,
Chem. Commun. 2008, 20, 2364-2366.
[1]
[2]
[3]
[4]
[5]
[6]
B. Tang, C. Wang, Y. Wang, H. Zhang, Angew. Chem. Int. Ed. 2017, 56,
12543-12547.
[31] K. Jayaramulu, P. Kanoo, S. J. George, T. K. Maji, Chem. Commun.
2010, 46, 7906-7908.
M. Shimizu, Y. Takeda, M. Higashi, T. Hiyama, Angew. Chem. 2009,
121, 3707-3710.
[32] J. Goodman, L. E. Brus, J. Am. Chem. Soc. 1978, 100, 7472-7474.
[33] T. Beppu, K. Tomiguchi, A. Masuhara, Y. J. Pu, H. Katagiri, Angew.
Chem. Int. Ed. 2015, 54, 7332-7335.
S. G. Jo, D. H. Park, B. G. Kim, S. Seo, S. J. Lee, J. Kim, J. Kim, J. Joo,
J. Mater. Chem. C 2014, 2, 6077-6083.
S. Kim, D. H. Kim, J. Choi, H. Lee, S. Y. Kim, J. W. Park, D. H. Park,
Materials 2018, 11, 472.
[34] X. Zheng, W. Zhu, D. Liu, H. Ai, Y. Huang, Z. Lu, ACS Appl. Mater.
Interfaces 2014, 6, 7996-8000.
Y. Hu, X. Zhou, H. Jung, S. J. Nam, M. H. Kim, J. Yoon, Anal. Chem.
2018, 90, 3382-3386.
[35] Y. Luo, C. Li, W. Zhu, X. Zheng, Y. Huang, Z. Lu, Angew. Chem. Int. Ed.
2019, 58, 6280-6284.
M. Tian, J. Sun, Y. Tang, B. Dong, W. Lin, Anal. Chem. 2018, 90, 998-
1005.
[36] Y. Akae, H. Sogawa, T. Takata, Angew. Chem. Int. Ed. 2018, 57,
14832-14836.
[7]
[8]
D. Kim, J. Kim, T. S. Lee, Sens. Actuat. B: Chem. 2018, 264, 45-51.
M. D. Watson, A. Fechtenkötter, K. Müllen, Chem. Rev. 2001, 101,
1267-1300.
[37] K. Zhou, H. Dong, H. l. Zhang, W. Hu, Phys. Chem. Chem. Phys. 2014,
16, 22448-22457.
[38]
S. G. Jo, S. Kim, E. H. Cho, D. H. Lee, J. Kim, S. J. Lee, J. Joo, Chem.
Asian J. 2012, 7, 2768-2771.
[9]
A. C. Benniston, T. P. L. Winstanley, H. Lemmetyinen, N. V.
Tkachenko, R. W. Harrington, C. Wills, Org. Lett. 2012, 6, 1374-1377.
[39] E. H. Cho, B. G. Kim, S. Jun, J. Lee, D. H. Park, K. S. Lee, J. Kim, J.
Kim, J. Joo, Adv. Funct. Mater. 2014, 24, 3684-3691.
[10] L. Hintermann, K. Suzuki, Synthesis, 2008, 14, 2303-2306.
[11] S. J. Lord, H. l. D. Lee, R. Samuel, R. Weber, N. Liu, N. R. Conley, M.
A. Thompson, R. J. Twieg, W. E. Moerner, J. Phys. Chem. B 2010, 114,
14157-14167.
[40] M. P. Zhuo, Y. C. Tao, X. D. Wang, Y. Wu, S. Chen, L. S. Liao, L. Jiang,
Angew. Chem. Int. Ed. 2018, 57, 11300-11304.
[41] L. Catalano, D. P. Karothu, S. Schramm, E. Ahmed, R. Rezgui, T. J.
Barber, A. Famulari, P. Naumov, Angew. Chem. Int. Ed. 2018, 57,
17254-17258.
[12] S. Kim, S. Y. Park, Adv. Mater. 2003, 16, 1341-1344.
[13] Y. Okada, M. Sugai, K. Chiba, J. Org. Chem. 2016, 81, 10922-10929.
This article is protected by copyright. All rights reserved.

10.1002/cplu.201900405
ChemPlusChem
FULL PAPER
Entry for the Table of Contents (Please choose one layout)
Layout 1:
FULL PAPER
Fluorescence from so simple
structure? Unusual fluorescence
from single benzene-based diethyl
2,5-dihydroxyterephthalate (DDT)
was reported to investigate the
origin of the strong fluorescence in
solution and the solid. Facile and
rapid crystallization ability of DDT
enabled efficient 1D optical
waveguiding with a large optical
loss coefficient of 0.158 dB/m, in
which this organic crystal has a
potential application in organic
optical communication.
Eunbee Cho, Jinho Choi, Seonyoung
Jo, Dong-Hyuk Park,* Young Ki
Hong,* Dongwook Kim, Taek Seung
Lee*
Page No. – Page No.
Single Benzene-Based
Fluorophore and Optical
Waveguiding in Its Crystal
Layout 2:
FULL PAPER
Author(s), Corresponding Author(s)*
((Insert TOC Graphic here; max. width: 11.5 cm; max. height: 2.5 cm))
Page No. – Page No.
Title
Text for Table of Contents
This article is protected by copyright. All rights reserved.