New anthracene derivatives as triplet acceptors for efficient green-to-blue low-power upconversion

Article abstract of DOI:10.1002/cphc.201300571

Three new anthracene derivatives [2-chloro-9,10-dip-tolylanthracene (DTACl), 9,10-dip-tolylanthracene-2-carbonitrile (DTACN), and 9,10-di(naphthalen-1-yl)anthracene-2-carbonitrile (DNACN)] were synthesized as triplet acceptors for low-power upconversion. Their linear absorption, single-photon-excited fluorescence, and upconversion fluorescence properties were studied. The acceptors exhibit high fluorescence yields in DMF. Selective excitation of the sensitizer Pd^IIoctaethylporphyrin (PdOEP) in solution containing DTACl, DTACN, or DNA-CN at 532 nm with an ultralow excitation power density of 0.5 W cm^-2 results in anti-Stokes blue emission. The maximum upconversion quantum yield (Φ_UC=17.4 %) was obtained for the couple PdOEP/DTACl. In addition, the efficiency of the triplet-triplet energy transfer process was quantitatively studied by quenching experiments. Experimental results revealed that a highly effective acceptor for upconversion should combine high fluorescence quantum yields with efficient quenching of the sensitizer triplet. Three against three: Organic acceptors are used for triplet-triplet-annihilation upconversion and upconversion quantum yields of up to 17.4 % are observed. The efficient triplet-triplet-annihilation upconversion is attributed to an efficient quenching of the sensitizer triplet and the high fluorescence quantum yields.

Full text of DOI:10.1002/cphc.201300571

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DOI: 10.1002/cphc.201300571
New Anthracene Derivatives as Triplet Acceptors for
Efficient Green-to-Blue Low-Power Upconversion
Zuo-Qin Liang,[a] Bin Sun,[a] Chang-Qing Ye,[a] Xiao-Mei Wang,*[a] Xu-Tang Tao,[b]
Qin-Hua Wang,[c] Ping Ding,[a] Bao Wang,[a] and Jing-Jing Wang[a]
Three new anthracene derivatives [2-chloro-9,10-dip-tolyl-
anthracene (DTACl), 9,10-dip-tolylanthracene-2-carbonitrile
(DTACN), and 9,10-di(naphthalen-1-yl)anthracene-2-carbonitrile
(DNACN)] were synthesized as triplet acceptors for low-power
upconversion. Their linear absorption, single-photon-excited
fluorescence, and upconversion fluorescence properties were
studied. The acceptors exhibit high fluorescence yields in DMF.
Selective excitation of the sensitizer PdIIoctaethylporphyrin
(PdOEP) in solution containing DTACl, DTACN, or DNA-CN at
532 nm with an ultralow excitation power density of
0.5 WcmÀ2 results in anti-Stokes blue emission. The maximum
upconversion quantum yield (FUC =17.4%) was obtained for
the couple PdOEP/DTACl. In addition, the efficiency of the trip-
let–triplet energy transfer process was quantitatively studied
by quenching experiments. Experimental results revealed that
a highly effective acceptor for upconversion should combine
high fluorescence quantum yields with efficient quenching of
the sensitizer triplet.
1. Introduction
Upconversion, that is, the processes of short-wavelength radia-
tion from long-wavelength light sources, has been intensively
studied due to its potential application in fields such as photo-
voltaics,[1,2] photocatalysis,[3] biological imaging and sensing,[4–7]
and photodynamic therapy of cancer.[8–10] A few techniques for
upconversion have been well established, such as the two-
photon absorption in organic molecules[11,12] and the sequen-
tial energy transfer upconversion in rare-earth ion-doped
glasses.[13,14] Both need either a high power density (usually in
the order of kWcmÀ2 and MWcmÀ2) and/or a coherent excita-
tion source. The extreme conditions limit the application of
these upconversion techniques. Recently, a new method for
upconversion, based on sensitized triplet–triplet annihilation
(TTA), emerged as a promising wavelength-shifting technology.
The excitation density required for TTA upconversion is quite
low. The energy density of a few mWcmÀ2 is sufficient to pro-
duce efficient upconverted photons, and the excitation does
not need to be coherent. Thus, it is possible to use solar light
as the excitation source for TTA upconversion.
TTA upconvesion requires a triplet sensitizer and an acceptor
to accomplish the cascade processes of light-harvesting, triple–
triplet energy transfer (TTET), TTA, and upconverted fluores-
cence emission. Over the past few years, tremendous advances
have been made on the development of sensitizers by utilizing
various heavy metal complexes, involving RuII polyimine com-
plexes,[15–17] PtII/PdII porphyrin complexes,[18–22] PtII acetylide
complexes,[23,24] and cyclometalated IrIII complexes.[25] Many ex-
periments indicate that triplet sensitizers with intense absorp-
tion of visible light, and long triplet-excited-state lifetimes are
helpful to improve the TTA upconversion efficiency. Besides,
some organic chromophores, which show intersystem crossing
between the singlet state and the triplet state without heavy
metal atoms, were selected as the triplet sensitizers.[27–29]
Compared to the development of triplet sensitizers, much
less attention has been paid to the development of triplet ac-
ceptors.[30–33] To date, triplet acceptors are limited to a few
commercially available compounds. In the process of TTA up-
conversion, the sensitizer absorbs light and transfers it to the
acceptor. Then, the singlet excited state of the acceptor decays
radiatively leading to upconversion fluorescence. Photophysi-
cal properties of the acceptor thus also crucially influence the
upconversion quantum yield. It is necessary for the develop-
ment of new triplet acceptors to understand the common re-
quirement for them. In this paper, we report three new anthra-
cene derivatives, namely 2-chloro-9,10-dip-tolylanthracene
(DTACl), 9,10-dip-tolylanthracene-2-carbonitrile (DTACN), and
9,10-di(naphthalen-1-yl)anthracene-2-carbonitrile (DNACN), as
organic triplet acceptors for low-power upconversion.
PdIIoctaethylporphyrin (PdOEP) was used as triplet sensitizer.
The structures of the sensitizer and the acceptors employed in
[a] Dr. Z.-Q. Liang, B. Sun, Dr. C.-Q. Ye, Prof. X.-M. Wang, P. Ding, B. Wang,
J.-J. Wang
Jiangsu Key Laboratory for Environment Function Materials
School of Chemistry, Biology and Material Engineering
Suzhou University of Science and Technology
Suzhou, 215009 (PR China)
Fax: (+86)512-68326615
E-mail: wangxiaomei@mail.usts.edu.cn
[b] Prof. X.-T. Tao
State Key Laboratory of Crystal Materials, Shandong University
Jinan, 250100 (PR China)
[c] Prof. Q.-H. Wang
Institute of Modern Optical Technologies
Key Lab of Advanced Optical Manufacturing Technologies
of Jiangsu Province and Key Lab of Modern Optical Technologies
of Education Ministry of China
Soochow University, Suzhou, 215006 (PR China)
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the energy upconvesion system are shown in Figure 1. Their
linear absorption, single-photon-excited fluorescence, and TTA
upconversion fluorescence properties were studied. A high up-
conversion quantum yield (FUC) of 17.4% was obtained for the
Figure 1. Chemical structures of the sensitizer and the acceptors.
couple PdOEP/DTACl upon excitation at 532 nm with an ultra-
low excitation power density of 0.5 WcmÀ2. It was found that
for an acceptor to be highly effective, it should combine high
fluorescence quantum yield with efficient quenching of the
sensitizer triplet.
2. Results and Discussion
The sensitizer PdOEP was prepared according to a method re-
ported in the literature.[34] The synthetic strategies for the ac-
ceptors (DTACl, DTACN, and DNACN) are depicted in Scheme 1.
DTACl was obtained by the nucleophilic addition of lithiated
bromomethylbenzene to 2-chloroanthraquinone followed re-
duction. DTACN was prepared by the Rosenmund–Brawn reac-
tion between DTACl and CuCN in N-methyl pyrrolidone (NMP).
The synthetic route to obtain DNACN was almost the same as
that of DTACN, with the only difference being the use of
2-bromonaphthalene.
Scheme 1. Synthetic routes to DTACl, DTACN, and DNACN.
quinine sulfate as standard. The fluorescence quantum yields
of compounds DTACl, DTACN, and DNACN are found to be
0.70, 0.53, and 0.65, respectively. Key photophysical data of the
acceptors are listed in Table 1.
To investigate their photophysical properties, the absorption
and fluorescence spectra of PdOEP, DTACl, DTACN, and DNACN
were measured in DMF solution (1ꢁ10À6 m), as shown in
Figure 2. The sensitizer PdOEP exhibits characteristic absorp-
tion bands at 511 and 544 nm corresponding to the Q-band
and 354 nm, which corresponds to the Soret band. Upon exci-
tation at 511 nm, PdOEP produces a singlet fluorescence at
550 nm with a shoulder peak and long-lived triplet phosphor-
escence at 663 nm. The absorption spectrum of DTACl shows
the characteristic vibronic pattern of an isolated anthracene
group at about 359, 380, and 400 nm in DMF, as shown in Fig-
ure 2a. For DTACN and DNACN the characteristic vibronic pat-
tern is observed as well, and their longest absorption bands
are centered at 416 nm. Compared with the longest absorption
band of DTACl, the bands of DTACN and DNACN are red-shift-
ed by 16 nm. The redshift of the absorption spectra of DTACN
and DNACN is due to the strong electron-withdrawing ability
of the cyano group. The fluorescence spectra of the three ac-
ceptors are gradually red-shifted, as can be seen by their emis-
sion bands, which are centered at 441 nm (DTACl), 446 nm
(DTACN), and 452 nm (DNACN). The fluorescence quantum
yields of the three acceptors in DMF were measured by using
TTA upconversion is strongly dependent on the experimen-
tal conditions, such as the concentration of the acceptors.
Thus, the relationship between upconversion intensity and
concentration of the acceptors was studied. Figure 3 shows
the dependence of upconversion fluorescence intensity on the
relative concentration of the acceptor/sensitizer upon excita-
tion at 532 nm (2.33 eV) with a power density of 0.5 WcmÀ2 in
degassed DMF. For the PdOEP/DTACl system, a blue emission
appears at 444 nm (2.79 eV), resulting in a net energy shift of
0.46 eV between the excitation wavelength and the emitted
photons. The upconversion fluorescence intensity continues to
increase with the concentration of DTACl up to a maximum of
5ꢁ10À4 m, after which a small decrease in the upconverted
emission intensity was observed. At the same time, the emis-
sion intensity of PdOEP at 663 nm gradually weakens. In con-
trast, the emission of PdOEP at about 550 nm is not quenched
at all in the presence of DTACl. This is because the triplet excit-
ed state, instead of the singlet excited state of the sensitizer, is
involved in the TTET process. PdOEP/DTACN and PdOEP/
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Figure 2. Normalized linear absorption (a) and single-photon-excited fluores-
cence (b) of PdOEP, DTACl, DTACN, and DNACN in DMF.
DNACN systems also exhibited a blue emission upon excitation
at 532 nm, as shown in Figure 3b and c. Their upconversion
fluorescence spectra reveal the same trends as observed for
the PdOEP/DTACl system. A compilation of anti-Stokes energy
shifts is shown in Table 1. Excitation at 532 nm of the sensitizer
or the acceptors alone did not produce the blue emission
band in the range of 400–532 nm. The blue upconversion fluo-
rescence is very similar to the fluorescence spectrum of the
corresponding acceptor. Therefore, the emission at 400–
532 nm should be ascribed to the TTA upconversion process.
It is interesting to note that upon increasing the acceptors’
concentration, the phosphorescence of PdOEP was slightly
quenched, but the upconverted fluorescence was enhanced
significantly. According to the photophysics of the TTA upcon-
version, the quenched phosphorescence emission area should
be at least twofold that of the upconverted fluorescence emis-
sion.[23,35] It was thus considered that non-emission of the sen-
sitizer at the triplet excited state is involved in the TTET pro-
cess. Zhao et al. have developed a series of organic sensitizers
Figure 3. Dependence of upconversion fluorescence intensity on the relative
concentrations of the acceptors DTACl (a), DTACN (b), and DNACN (c) at
fixed concentration of the sensitizer PdOEP (1ꢁ10À5 m) upon excitation at
532 nm with a power density of 0.5 WcmÀ2 in degassed DMF.
based on boron-dipyrromethane (BODIPY) that showed non-
emissive triplet excited states but effective upconversion capa-
bility.[28,29] Chow et al. reported the sensitizer 2,4,5,7-tetraiodo-
6-hydroxy-3-fluorone (TIHF), which shows no phosphorescence
at room temperature but also ideal upconversion properties.[27]
Therefore, it is possible to use weakly phosphorescent or non-
phosphorescent compounds as
triplet sensitizers for TTA upcon-
version, as long as the triplet ex-
Table 1. Photophysical parameters of the acceptors DTACl, DTACN, and DNACN.
cited state of these compounds
max
[b]
[c]
Compound
lab
lem
F[a]
Ksv
FUC
EemÀEex
can be efficiently populated
upon photoexcitation.
[nm]
[nm]
[%]
[eV][d]
DTACl
DTACN
DNACN
400
416
416
441
446
452
0.70
0.53
0.65
8.9ꢁ104
1.0ꢁ105
7.1ꢁ104
17.4
16.7
12.7
0.46
0.45
0.41
Figure 4 displays the depend-
ence of the upconversion quan-
tum yield on the concentration
of the acceptors at a constant
concentration (1ꢁ10À5 m) of the
[a] Fluorescence quantum yields. [b] Stern–Volmer quenching constants. [c] Upconversion quantum yields.
[d] em=emission peak; ex=excitation peak.
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cess is DTACN>DTACl>DNACN. In contrast, the upconversion
quantum yield follows the order DTACl>DTACN>DNACN. It is
revealed that the enhanced upconversion quantum yield does
not simply result from the differences in quenching efficiency.
The singlet excited state of the acceptor decays radiatively,
leading to to upconversion fluorescence. Therefore, a good ac-
ceptor should have a high fluorescence quantum yield.
Measuring the fluorescence quantum yield, we found the fol-
lowing order DTACl>DNACN>DTACN. It is believed that
DTACl’s increased fluorescence quantum yield with respect to
DTACN is mainly responsible for the moderate increase in up-
conversion efficiency. Compared to DNACN, the high upcon-
version quantum yield of DTACN is proposed to be due to its
efficient quenching constants. These results manifest that large
Stern–Volmer quenching constant and high fluorescence quan-
tum yields for the acceptors are crucial for the improvement of
upconversion efficiency.
Figure 4. Dependence of the upconversion quantum yield on the relative
concentration of the acceptors at a constant concentration (1ꢁ10À5 m) of
the sensitizer upon excitation at 532 nm with a power density at 0.5 WcmÀ2
.
sensitizer. The upconversion quantum yield measurements of
DTACl, DTACN, and DNACN in DMF were measured against
rhodamine 6G in methanol with an excitation wavelength of
532 nm according to the literature.[35] The upconversion quan-
tum yield of DTACl increases with increasing concentration.
When the concentration is 5ꢁ10À4 m, the upconversion quan-
tum yield reaches its maximum (17.4%). Increasing the concen-
tration further, leads to weaker quantum yields. This is because
the increase in DTACl concentration renders the encounter of
the sensitizer and the acceptor more likely, which enhances
the yields of the energy transfer process.[36] However, when the
concentration of DTACl exceeds the threshold value of
5ꢁ10À4 m, the upconversion fluorescence is partly suppressed
due to the concentration quenching effect. Similar results were
obtained across the DTACN and DNACN concentration profiles.
The maximum upconversion quantum yields for DTACN and
DNACN are 16.7 and 12.7%, respectively.
Selective excitation of PdOEP (1ꢁ10À5 m) in the presence of
DNACN (1ꢁ10À4 m) in degassed DMF with lex =532 nm at vari-
ous incident excitation powers ranging from 1.03 to
7.23 WcmÀ2 resulted in the upconverted fluorescence of
DNACN (Figure 6a). Analysis of the sensitized upconverted in-
tegrated emission intensity of DNACN as a function of the inci-
dent light intensity is shown in Figure 6b. These data were
normalized to the highest integrated emission intensity, as well
as to the highest incident power. The solid line passing
The TTET process between the sensitizer and the acceptors
was quantitatively studied by the photoluminescence quench-
ing of the sensitizer PdOEP, with the acceptors as quenchers.
The Stern–Volmer quenching curves were constructed, as
shown in Figure 5. Stern–Volmer analysis yields quenching con-
stants of 8.9ꢁ104, 1.0ꢁ105, and 7.1ꢁ104 for DTACl, DTACN,
and DNACN, respectively. Thus, the efficiency of the TTET pro-
Figure 6. a) Upconverted emission intensity of DNACN following the selec-
tive excitation of PdOEP (lex =532 nm), measured as a function of incident
power intensity. b) Normalized integrated emission intensity data from part
(a), plotted as a function of the normalized incident power intensity of the
laser. Inset: Double-logarithmic plot of the normalized upconverted emission
of DNACN.
Figure 5. Stern–Volmer analyses of the PdOEP triplet quenching by the ac-
ceptors upon excitation at 532 nm with a power density at 0.5 WcmÀ2
.
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Experimental Section
through the data points represents the best quadratic fit (c2)
to the data, illustrating the nonlinear nature of anti-Stokes
emission process. The double logarithm plot in the inset of
Figure 6b yields a straight line with a slope of 1.8 confirming
the quadratic dependence of the sensitized annihilation pro-
cess. The integrated upconverted fluorescence intensity of
DTACl and DTACN measured as a function of the incident laser
power was also evaluated. Their upconverted fluorescence is
proportional to the square of the incident light power at
532 nm.
All reagents and materials used for the synthesis were commercial
available. Dry tetrahydrofuran (THF) was freshly distilled over
sodium prior to use. All other reagents were used as received. The
1H NMR and 13C NMR spectra were recorded at 258C on a Bruker
Avance 400 MHz spectrometer. Elemental analyses were performed
on an Elementar Vario EL-III instrument. UV/Vis absorption spectra
were recorded on a Varian Cary 50 spectrophotometer. Fluores-
cence measurements were carried out with a Hitachi F-4500 fluo-
rescence spectrometer equipped with a 150 W Xe lamp.
The photon upconversion can be easily visualized in the
PdOEP/DTACl, PdOEP/DTACN, and PdOEP/DNACN systems with
a commercial green laser pointer (lex =532 nm, peak power
<5 mW). Figure 7 shows the photograph of the upconverted
fluorescence in degassed DMF solution containing PdOEP and
DTACl. The naked eye image illustrates that low power is
indeed realized in these chromophore mixtures.
A diode-pumped solid-state laser (emission wavelength: 532 nm)
was used as the excitation source for the TTA upconversion. The
laser power was measured with a photodiode detector. For the up-
conversion experiments, the mixed solution of the triplet sensitizer
and the acceptor was degassed for at least 30 min with N2. Then
the solution was excited with the laser. The upconverted fluores-
cence was observed with a PR655 SpectraScan colorimeter.
Synthesis of 2-chloro-9,10-dip-tolyl-9,10-dihydroanthracene-9,10-
diol: Under a N2 atmosphere at À788C, 1.6m tBuLi (25.0 mL,
62.0 mmol) was added dropwise to a mixture of 1-bromo-4-meth-
ylbenzene (5.50 mL, 41.0 mmol) and 40 mL dried THF. After the ad-
dition, stirring was continued for 30 min. At À40~À508C, a solu-
tion of 2-chloroanthraquinone (5.00 g, 30.8 mmol) in 60 mL THF
was injected through a syringe. The turbid solution changed from
white to wine red. The mixture was allowed to warm to room tem-
perature and maintained for 24 h. The reaction mixture was added
to a saturated aqueous solution of NH4Cl (120 mL). The organic sol-
vent was evaporated, and the suspension was extracted with ethyl
acetate. The organic extracts were washed by water and brine, and
dried by anhydrous magnesium sulfate. Removing of the solvents
afforded a yellow oil, which was used without further purification.
Synthesis of 2-chloro-9,10-dip-tolylanthracene (DTACl): 2-chloro-
9,10-dip-tolyl-9,10-dihydroanthracene-9,10-diol (4.05 g, 9.0 mmol),
sodium phosphinate monohydrate (16.6 g, 157 mmol), and potassi-
um iodide (15.8 g, 95.0 mmol) in acetic acid (40 mL) were refluxed
at 1208C for 3 h. After the mixture was cooled, water was added
to it. The crude solid product was filtered and washed with water.
The crude product was recrystallized using acetic acid to give
Figure 7. Photographs of the emission of PdOEP alone and the upconverted
fluorescence of PdOEP/DTACl. the excitation source was a commercial green
laser pointer (lex =532 nm).
1
a light yellow solid. Yield (3.27 g, 50.6%). H NMR (CDCl3, 400 MHz)
3. Conclusions
d=2.54 (d, 6H, J=3.2 Hz), 7.20–7.23 (m, 1H), 7.31–7.43 (m, 10H),
7.65–7.71 ppm (m, 4H). 13C NMR (CDCl3, 100 MHz) d=21.39, 21.41,
125.18, 125.23, 125.47, 125.99, 127.02, 127.13, 128.21, 129.00,
129.20, 129.30, 130.13, 130.39, 130.68, 131.01, 131.10, 131.11,
135.28, 135.50, 136.39, 137.34, 137.38, 137.47 ppm. Elemental anal-
ysis calc. for C28H21Cl: C, 85.59; H, 5.39; Cl, 9.02. Found: C, 85.62; H,
5.52; Cl, 8.86.
The linear absorption, single-photon-excited fluorescence and
TTA upconversion fluorescence properties of three acceptors
have been studied. These acceptors exhibited high fluores-
cence yields in DMF. The upconversion properties of PdOEP/
DTACl, PdOEP/DTACN, and PdOEP/DNACN were investigated as
a function of acceptor concentration. Selective excitation of
the dye cocktail at 532 nm with ultralow excitation power den-
sity of 0.5 WcmÀ2 resulted in anti-Stokes blue emission from
the acceptors. The highest FUC =17.4% was obtained for the
couple PdOEP/DTACl. In addition, the efficiency of the TTET
process was quantitatively studied by quenching experiments.
It has been found that upconversion quantum yield does not
simply result from the differences in quenching efficiency.
Highly effective acceptors for upconversion should combine
high fluorescence quantum yields with efficient quenching of
the sensitizer triplet. It is important to note that the green-to-
blue photon upconversion can be easily visualized in the three
sensitizer/acceptor systems investigated here with a commer-
cial green laser pointer.
Synthesis of 9,10-dip-tolylanthracene-2-carbonitrile (DTACN):
A three-necked flask was charged with DTACl (0.72 g, 1.80 mmol),
CuCN (0.97 g, 10.8 mmol), and NMP (30 mL) under N2 atmosphere.
After the reaction mixture was refluxed for 24 h, the mixture was
allowed to cool to 708C. Then FeCl3 (5.80 g, 35.8 mmol) in concen-
trated hydrochloric acid (10 mL) was added. The mixture was
stirred at 708C for 3 h. The reaction mixture was filtered, and the
residue was washed by water and dried under vacuum. The crude
product was purified by flash column chromatography over silica
using petroleum/dichloromethane (v/v=6:1) as eluent to give
a yellowlish green solid. Yield (0.46 g, 66.7%). 1H NMR (CDCl3,
400 MHz) d=2.56 (d, 6H, J=3.6 Hz), 7.32–7.45 (m, 12H), 7.74–7.80
(m, 2H), 8.16 ppm (s, 1H). 13C NMR (CDCl3, 100 MHz) d=21.40,
108.23, 119.74, 123.80, 126.00, 126.59, 127.20, 127.50, 128.51,
128.60, 129.34, 129.44, 129.92, 130.85, 131.01, 131.02, 131.86,
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[9] A. Karotki, M. Khurana, J. R. Lepock, B. C. Wilson, Photochem. Photobiol.
2006, 82, 443–452.
[10] L. Cheng, C. Wang, Z. Liu, Nanoscale 2013, 5, 23–37.
[11] W. Denk, J. H. Strickler, W. W. Webb, Science 1990, 248, 73–76.
[12] X. M. Wang, F. Jin, Z. G. Chen, S. Q. Liu, X. H. Wang, X. M. Duan, X. T. Tao,
M. H. Jiang, J. Phys. Chem. C 2011, 115, 776–784.
[13] F. Auzel, Chem. Rev. 2004, 104, 139–174.
[14] X. Y. Huang, S. Y. Han, W. Huang, X. G. Liu, Chem. Soc. Rev. 2013, 42,
173–201.
[15] T. N. Singh-Rachford, A. Nayak, M. L. Muro-Small, S. Goeb, M. J. Therien,
F. N. Castellano, J. Am. Chem. Soc. 2010, 132, 14203–14211.
[16] G. Bergamini, P. Ceroni, P. Fabbrizi, S. Cicchi, Chem. Commun. 2011, 47,
12780–12782.
[17] W. Hu, S. M. Ji, W. T. Wu, J. Y. Shao, H. M. Guo, T. D. James, J. Z. Zhao,
Chem. Eur. J. 2012, 18, 4953–4964.
[18] P. E. Keivanidis, S. Baluschev, T. Miteva, G. Nelles, U. Scherf, A. Yasuda, G.
Wegner, Adv. Mater. 2003, 15, 2095–2098.
[19] S. Baluschev, P. E. Keivanidis, G. Wegner, J. Jacob, A. C. Grimsdale, K.
Mꢂllen, T. Miteva, A. Yasuda, G. Nelles, Appl. Phys. Lett. 2005, 86,
061904.
134.39, 134.87, 134.89, 137.68, 137.73, 137.98, 138.97 ppm. Elemen-
tal analysis calc. for C29H21N: C, 90.86; H, 5.48; N, 3.65. Found: C,
91.01; H, 5.57; N, 3.54.
Synthesis
of
9,10-di(naphthalen-1-yl)anthracene-2-carbonitrile
(DNACN): Analogous procedure as for the preparation of DTACN,
but starting from 2-bromonaphthalene (6.40 g, 31.0 mmol). DNACN
was obtained as a yellow solid. Yield (0.32 g, 65.3%). 1H NMR
(CDCl3, 400 MHz) d=7.34–7.44 (m, 3H), 7.58-7.66 (m, 6H), 7.76-7.83
(m, 3H), 7.93–7.98 (m, 4H), 8.03–8.07 (m, 2H), 8.12 (t, J=8.0 Hz,
2H), 8.18 ppm (s, 1H). 13C NMR (CDCl3, 100 MHz) d=29.70, 53.41,
108.61, 119.52, 124.14, 126.29, 126.61, 126.76, 126.88, 127.26,
127.55, 127.98, 128.02, 128.11, 128.16, 128.35, 128.48, 128.56,
128.65, 128.95, 129.08, 129.98, 130.26, 130.32, 130.96, 131.91,
132.95, 133.05, 133.33, 133.39, 134.77, 134.91, 135.39, 137.76 ppm.
Elemental analysis calc. for C35H21N: C, 92.28; H, 4.65; N, 3.07.
Found: C, 92.54; H, 4.72; N, 2.74.
[20] V. Yakutkin, S. Aleshchenkov, S. Chernov, T. Miteva, G. Nelles, A. Chepra-
kov, S. Baluschev, Chem. Eur. J. 2008, 14, 9846–9850.
[21] R. R. Islangulov, J. Lott, C. Weder, F. N. Castellano, J. Am. Chem. Soc.
2007, 129, 12652–12653.
[22] T. N. Singh-Rachford, J. Lott, C. Weder, F. N. Castellano, J. Am. Chem. Soc.
2009, 131, 12007–12014.
[23] Q. T. Li, H. M. Guo, L. H. Ma, W. H. Wu, Y. F. Liu, J. Z. Zhao, J. Mater. Chem.
2012, 22, 5319–5329.
[24] H. Y. Sun, H. M. Guo, W. T. Wu, X. Liu, J. Z. Zhao, Dalton Trans. 2011, 40,
7834–7841.
[25] J. F. Sun, W. H. Wu, J. Z. Zhao, Chem. Eur. J. 2012, 18, 8100–8112.
[26] J. Z. Zhao, S. M. Ji, H. M. Guo, RSC Adv. 2011, 1, 937–950.
[27] H. C. Chen, C. Y. Hung, K. H. Wang, H. L. Chen, W. S. Fann, F. C. Chien,
P. L. Chen, T. J. Chow, C. P. Hsu, S. S. Sun, Chem. Commun. 2009, 4064–
4066.
Acknowledgements
The authors are grateful to the National Natural Science Founda-
tion of China (50973077, 51273141), the Natural Science Founda-
tion of JiangSu Province Education Committee (11KJA430003),
the Project of Person with Ability of Jiangsu Province (2010-xcl-
015), the Priority Academic Program Development of Jiangsu
Higher Education Institutions (PAPD), the Project of Science and
Technology of Suzhou (SYG201204), and the Opening Project of
Key Lab of Advanced Optical Manufacturing Technologies of
Jiangsu Province (KJS1102) for financial supports.
[28] W. H. Wu, H. M. Guo, W. T. Wu, S. M. Ji, J. Z. Zhao, J. Org. Chem. 2011, 76,
7056–7064.
Keywords: anthracene
·
fluorescence
·
Stern–Volmer
[29] W. H. Wu, J. Z. Zhao, J. F. Sun, S. Guo, J. Org. Chem. 2012, 77, 5305–
5312.
quenching constants · triplet acceptors · upconversion
[30] T. N. Singh-Rachford, F. N. Castellano, Inorg. Chem. 2009, 48, 2541–2548.
[31] T. N. Singh-Rachford, A. Haefele, R. Ziessel, F. N. Castellano, J. Am. Chem.
Soc. 2008, 130, 16164–16165.
[32] S. Baluschev, V. Yakutkin, T. Miteva, G. Wegner, T. Roberts, G. Nelles, A.
Yasuda, S. Chernov, S. Aleshchenkov, A. Cheprakov, New J. Phys. 2008,
10, 013007.
[33] A. Turshatov, D. Busko, Y. Avlasevich, T. Miteva, K. Landfester, S. Balu-
schev, ChemPhysChem 2012, 13, 3112–3115.
[34] J. L. Sessler, A. Mozaffari, M. R. Johnson, Org. Synth. 1992, 70, 242.
[35] T. N. Singh-Rachford, F. N. Castellano, Coord. Chem. Rev. 2010, 254,
2560–2573.
[1] A. Rapaport, J. Miliez, M. Bass, A. Cassanho, H. Jenssen, J. Disp. Technol.
2006, 2, 68–78.
[2] Y. Y. Cheng, B. Fꢂeckel, R. W. MacQueen, T. Khoury, R. G. C. R. Clady, T. F.
Schulze, N. J. Ekins-Daukes, M. J. Crossley, B. Stannowski, K. Lips, T. W.
Schmidt, Energy Environ. Sci. 2012, 5, 6953–6959.
[3] R. S. Khnayzer, J. Blumhoff, J. A. Harrington, A. Haefele, F. Deng, F. N.
Castellano, Chem. Commun. 2012, 48, 209–211.
[4] D. R. Larson, W. R. Zipfel, R. M. Williams, S. W. Clark, M. P. Bruchez, F. W.
Wise, W. W. Webb, D. R. Larson, Science 2003, 300, 1434–1436.
[5] Q. Liu, B. R. Yin, T. S. Yang, Y. C. Yang, Z. Shen, P. Yao, F. Y. Li, J. Am.
Chem. Soc. 2013, 135, 5029–5037.
[36] Y. C. Simon, C. Weder, J. Mater. Chem. 2012, 22, 20817–20830.
[6] L. Wang, R. Yan, Z. Huo, L. Wang, J. Zeng, J. Bao, X. Wang, Q. Peng, Y. Li,
Angew. Chem. 2005, 117, 6208–6211; Angew. Chem. Int. Ed. 2005, 44,
6054–6057.
Received: June 17, 2013
[7] L. Cheng, K. Yang, M. W. Shao, S. T. Lee, Z. Liu, J. Phys. Chem. C 2011,
115, 2686–2692.
Revised: August 13, 2013
[8] J. Shan, X. Qin, N. Yao, Y. Ju, Nanotechnology 2007, 18, 445607.
Published online on && &&, 2013
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemPhysChem 0000, 00, 1 – 7
&
6
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These are not the final page numbers!

ARTICLES
Three against three: Organic acceptors
are used for triplet–triplet-annihilation
upconversion and upconversion quan-
tum yields of up to 17.4% are observed.
The efficient triplet–triplet-annihilation
upconversion is attributed to an effi-
cient quenching of the sensitizer triplet
and the high fluorescence quantum
yields.
Z.-Q. Liang, B. Sun, C.-Q. Ye, X.-M. Wang,*
X.-T. Tao, Q.-H. Wang, P. Ding, B. Wang,
J.-J. Wang
&& – &&
New Anthracene Derivatives as Triplet
Acceptors for Efficient Green-to-Blue
Low-Power Upconversion
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemPhysChem 0000, 00, 1 – 7
&
7
&
ÞÞ
These are not the final page numbers!