Efficient modification of pyrene-derivative featuring third-order nonlinear optics via the click post-functionalization

Article abstract of DOI:10.1016/j.tetlet.2013.06.121

A series of pyrene derivatives featuring nonplanar structures of N,N-didodecylanilino-substituted donor and TCNE/TCNQ adduct acceptors have been efficiently synthesized via formal [2+2] cycloaddition. As the efficient click by TCNE and TCNQ, the products show strong charge-transfer (CT) bands in the visible (near-IR region), potent redox activities, and related photophysical properties. UV/vis spectra and electrochemical studies show that the CT properties of these systems are readily tunable by strong cyano acceptor introduction on the nucleophile, which have a larger effect on the lowest unoccupied molecular orbital (LUMO). In particular, compared with the adduct of TCNE, the product clicked with TCNQ possessed a stronger D-A conjugation and bulkier π spacers. The TCNQ product also has a larger third-order nonlinear optical property which was characterized by Z-scan experiments. This could point to potentially interesting applications of the new pyrene derivatives in optoelectronic devices and develop the new modification process for the design of different pyrene-based molecular electronic devices.

Full text of DOI:10.1016/j.tetlet.2013.06.121

Tetrahedron Letters 54 (2013) 4859–4864
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Efficient modification of pyrene-derivative featuring third-order
nonlinear optics via the click post-functionalization q
a
a
a
a,b,
Zhaokui Jin a, Dong Wang a, , Xiangke Wang , Pengxia Liang , Yongsheng Mi , Huai Yang
⇑
⇑
a School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, PR China
b Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of pyrene derivatives featuring nonplanar structures of N,N-didodecylanilino-substituted donor
and TCNE/TCNQ adduct acceptors have been efficiently synthesized via formal [2+2] cycloaddition. As the
efficient click by TCNE and TCNQ, the products show strong charge-transfer (CT) bands in the visible
(near-IR region), potent redox activities, and related photophysical properties. UV/vis spectra and electro-
chemical studies show that the CT properties of these systems are readily tunable by strong cyano accep-
tor introduction on the nucleophile, which have a larger effect on the lowest unoccupied molecular
orbital (LUMO). In particular, compared with the adduct of TCNE, the product clicked with TCNQ pos-
Received 11 March 2013
Revised 20 May 2013
Accepted 24 June 2013
Available online 4 July 2013
Keywords:
Click chemistry
[2+2] Cycloaddition
Donor–acceptor systems
Pyrene derivative
sessed a stronger D–A conjugation and bulkier
p spacers. The TCNQ product also has a larger third-order
nonlinear optical property which was characterized by Z-scan experiments. This could point to poten-
tially interesting applications of the new pyrene derivatives in optoelectronic devices and develop the
new modification process for the design of different pyrene-based molecular electronic devices.
Ó 2013 The Authors. Published by Elsevier Ltd. All rights reserved.
Third-order nonlinear optical
Introduction
Two major reasons that account for the superiority of pyrene
are the significant formation of discotic chromophore leading to
The design of molecules for application in organic electronics is
multi-parameter challenge. The promising materials must
p-stacking and the tendency to form excimers, which seem to be
a
a promising candidate for nonlinear optical materials. The pres-
ence of electron-rich or electron-poor units is important and per-
mits the fine-tuning of the optical properties while also
influencing the charge carrier mobility.1 However, it is costly and
time-consuming to make the modifications on the pyrene cores
with a variety of energy levels due to the required tedious chemo-
synthesis and purification processes.
involve both the optimization of the functional units and the com-
bination of molecular and bulk properties suitable for the specific
application.1,2
p-Conjugated systems possess characteristically
large electronic polarizabilities, and it is reasonable to expect con-
jugated molecules to possess substantial hyperpolarizabilities.3,4 In
addition, it has been generally accepted that donor and acceptor
terminal sets separated by a
v
p
-conjugated system exhibit large
Innovative [2+2] cycloaddition of strong electron acceptors,
such as tetracyanoethene (TCNE) and 7,7,8,8-tetracyano-quino-
dimethane (TCNQ) to electron-rich alkynes,7,8 followed by retro-
electrocyclization, provides efficient access to nonplanar push–pull
chromophores featuring intense intramolecular charge-transfer
(CT) and high third-order optical nonlinearities.9 These transfor-
mations are generally fast, high-yielding, catalyst-free, 100%
atom-economic, and the resulting products can be easily purified
by precipitation or washing. Therefore, it is an admirable
combination that develops a post-functionalization approach with
alkyne-acceptor click chemistry aid of the synthesis of extraordi-
nary pyrene derivatives.
(3) values.5 This provides inspiration for the rational design of
structural motifs that are promising for third-order nonlinear
optics. There are many representative examples of conjugated
materials, including symmetric polymethines, polyenes, and
porphyrins.6 However, the present conjugated nonlinear optical
materials display several disadvantages such as complex fabrica-
tion and chemical instability. It is still significantly crucial to
develop new nonlinear optical molecular with donor–acceptor
(D–A)-substituted characteristics via simple and efficient routes.
Herein, we described such a reaction between TCNE/TCNQ and
N,N-didodecylanilino (NNA)-substituted alkynes, giving access to a
new class of low-molecular-weight pyrene derivatives revealing
high third-order optical nonlinearities. Our approach opens a
q
This is an open-access article distributed under the terms of the Creative
Commons Attribution-NonCommercial-No Derivative Works License, which per-
mits non-commercial use, distribution, and reproduction in any medium, provided
the original author and source are credited.
⇑
new platform of D-
p-A systems that contained a centered acceptor
Corresponding authors. Tel./fax: +86 10 62333969.
E-mail address: wangdong_ustb@foxmail.com (D. Wang).
and peripheral multidonors in contrast to conventional linear type
0040-4039/$ - see front matter Ó 2013 The Authors. Published by Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2013.06.121

4860
Z. Jin et al. / Tetrahedron Letters 54 (2013) 4859–4864
of D-
p
-A compounds. They included NNA donor and 1,1,4,4-
Synthesis methods
tetracyanobuta-1,3-diene (TCBD) acceptor moieties, and were
prepared by quite short and high-yielding synthetic routes. The no-
vel and instructive examples of pyrene derivatives could become
third-order nonlinear materials.
4,40,400,4000-(Pyrene-1,3,6,8-tetrayltetrakis(ethyne-2,1-diyl))tetrakis
(N,N-didodecylaniline) (PT)
To a degassed solution of dry Et3N/THF (1:1, 15 mL), 1,3,6,8-
tetrabromopyrene (as compound 1 in supporting information,
0.50 g, 0.97 mmol) and N,N-didodecyl-4-ethynylaniline (2.64 g,
5.82 mmol) were added and the mixture degassed under Ar. Cat-
alytic agents Pd(PPh3)2Cl2 (13.62 mg, 0.019 mmol) and CuI
(7.39 mg, 0.039 mmol) were then added, and the reaction mixture
was stirred overnight at 80 °C under Ar. The solvent was then re-
moved under reduced pressure, and the crude product was puri-
fied by column chromatography (silica gel, petroleum ether/
dichloromethane 6:1) to afford PT as an orange solid (1.33 g,
0.66 mmol, 68%). 1H NMR (400 MHz, CDCl3): d = 8.68 (4H, s),
8.31 (2H, s), 7.53 (d, J = 8.4 Hz, 8H), 6.63 (d, J = 8.4 Hz, 8H), 3.29
(16H, m), 1.60 (16H, s), 1.28 (144H, m), 0.89 (24H, m) ppm.
13C NMR (100 MHz, CDCl3): d = 147.7, 132.6, 132.2, 130.5, 125.9,
124.0, 119.0, 110.9, 108.5, 96.9, 85.6, 50.5, 31.3, 29.0, 28.8, 26.6,
22.1, 13.6 ppm. FT-IR (KBr): 2923, 2853, 2192, 1607, 1592,
1519, 1459, 1375, 1261, 1184, 1066, 809 cmꢁ1. MALDI-TOF-MS
(dithranol): m/z: calcd for C144H222N4: 2007.75 g molꢁ1, found:
2009.5 g molꢁ1 [MH]+. Elemental analysis calcd (%) for
Materials and methods
Material details
All the reagents were purchased as reagent grade from com-
mercial sources (Aldrich) and used without further purification.
Triethylamine (TEA) and tetrahydrofuran (THF) were distilled and
purged with argon before use. A Bruker DMS-400 spectrometer
was used to record the 1H NMR and 13C NMR spectra at 298 K.
CDCl3 was the solvent for NMR and chemical shifts relative to tet-
ramethyl silane (TMS) at 0.00 ppm are reported in parts per million
(ppm) on the d scale. The resonance multiplicity was described as s
(singlet), d (doublet), and m (multiplet). MALDI-TOF negative ion-
ization mass spectra were recorded on a Shimadzu spectrometer,
using dithranol as matrix. Elemental analyses were performed at
institute of chemistry Chinese academy of sciences, with a Flash
EA 1112 instrument. All UV–visible spectra were recorded on a
JASCO V-570 spectrophotometer. FT-IR spectroscopy was recorded
on a Perkin Elmer LR-64912C spectrophotometer. Differential
scanning calorimetry (DSC) analyses were performed on a Perkin
Elmer Pyris 6 instrument.
C144H222N4 (2007.75): C 86.08, H 11.14, N 2.79; found: C 86.03,
H 11.19, N 2.78
3,30,300-(8-(1,1,4,4-Tetracyano-3-(4-(didodecylamino)phenyl)
buta-1,3-dien-2-yl)pyrene-1,3,6-triyl)tris(2-(4-(didodecylamino)
phenyl)buta-1,3-diene-1,1,4,4-tetracarbonitrile) (PTE)
TCNE (0.038 g, 0.30 mmol) was added to a solution of PT (0.10 g,
0.050 mmol) in dichloromethane (15 mL), and the mixture was
stirred for one hour at room temperature. Evaporation of the sol-
vent and column chromatography (silica gel; dichloromethane)
afforded the desired products (0.11 g, 0.044 mmol, 89%). 1H NMR
(400 MHz, CDCl3):d = 8.77 (4H, s), 7.97 (2H, s), 7.71 (8H, s), 6.71
(8H, s), 3.37 (16H, s), 1.62 (16H, s), 1.27 (144H, m), 0.85 (24H, m)
ppm. 13C NMR (100 MHz, CDCl3): d = 161.6, 153.4, 132.4, 129.7,
125.4, 114.2, 112.9, 111.0, 110.5, 95.2, 67.9, 51.6, 31.8, 29.53,
29.47, 29.2, 27.3, 26.9, 25.5, 22.6, 14.0 ppm. FT-IR (KBr): 2925,
2853, 2215, 1602, 1533, 1492, 1417, 1340, 1292, 1184, 993,
Electrochemical tests
The redox properties of PT, PTE, and PTQ were investigated by
cyclic voltammetry (CV) in CH2Cl2 (1 ꢀ 10ꢁ5 M, 0.1 M nBu4NPF6, all
potentials versus the ferricinium/ferrocene couple (Fc+/Fc)). Cyclic
voltammetric (CV) measurements were carried out in a conven-
tional three-electrode cell using Glassy Carbon working electrodes
of 2 mm diameter, a platinum wire counter electrode, and a Ag/
AgCl reference electrode on a computer-controlled CHI 660C
instrument at room temperature. The energy levels were calcu-
lated using the Ferrocene (Fc) value of ꢁ4.8 eV with respect to
the vacuum level, which was defined as zero. The measured oxida-
tion potential of Fc (vs Ag/AgCl) was 0.18 V. Therefore, the HOMO
energy (EHOMO) levels of the products could be calculated by the
equation EHOMO ¼ e½EonsetðoxÞ ꢁ E1=2;Fc þ 4:8Vꢂ and the LUMO en-
809 cmꢁ1. MALDI-TOF-MS (dithranol): m/z: calcd for C168H222N20
:
2519.80 g molꢁ1, found: 2521.3 g molꢁ1 [MH]+. Elemental analysis
calcd (%) for C168H222N20 (2519.80): C 80.02, H 8.87, N 11.11;
found: C 80.12, H 8.79, N 11.09.
ergy (ELUMO) levels could be estimated by the equation
2,20,200,2000-(1,10,100,1000-(Pyrene-1,3,6,8-tetrayl)tetrakis(2-(4-
(dicyanomethylene)cyclohexa-2,5-dienylidene)-2-(4-
ELUMO ¼ e½EonsetðredÞ ꢁ E1=2;Fc þ 4:8Vꢂ, where E1/2,Fc stands for the
half-wave potential of Fc/Fc+.10
(didodecylamino)phenyl)ethan-1-yl-1-ylidene))
tetramalononitrile (PTQ)
Nonlinear optical measurements
TCNQ (0.061 g, 0.30 mmol) was added to a solution of PT
(0.10 g, 0.050 mmol) in dichlorobenzene (15 mL), and the mixture
was stirred for one hour at 100 °C. Evaporation of the solvent un-
der reduced pressure and column chromatography (silica gel;
dichloromethane) afforded the desired products (0.13 g,
0.047 mmol, 94%).1H NMR (400 MHz, CDCl3): d = 8.49 (4H, s),
7.71 (2H, s), 7.53 (8H, s), 7.27 (8H, s), 6.60 (16H, s), 3.30 (16H, s),
1.55 (16H, s), 1.24 (144H, m), 0.85 (24H, m) ppm. 13C NMR
(100 MHz, CDCl3): d = 157.5, 151.7, 135.9, 134.9, 133.2, 130.2,
127.4, 125.2, 114.3, 112.7, 65.2, 51.3, 31.6, 29.3, 29.0, 27.2, 26.7,
22.3, 13.8 ppm. FT-IR (KBr): 2924, 2853, 2204, 1596, 1521,
1465, 1398, 1362, 1261, 1181, 1094, 802 cmꢁ1. MALDI-TOF-MS
(dithranol): m/z: calcd for C192H238N20: 2823.92 g molꢁ1, found:
2825.2 g molꢁ1 [MH]+. Elemental analysis calcd (%) for
The nonlinear optical properties’ (NLO) response of molecular
PT, PTE, and PTQ was measured by means of Z-scan technique,
employing 20 ps laser pulses at 532 nm delivered by a mode-
locked Nd:YAG laser (EKSPLA PL2143B). The linearly polarized la-
ser beam was focused with a 200 mm focal length lens and the
sample was moved across the focus by means of a computer con-
trolled micrometric translation stage. The beam waist at the focus
was typically 20
5
lm and the pulse energy, after suitable atten-
uation, was in the range 0.2–0.5
l
J. Z-scan is a relatively simple
experimental technique allowing for the simultaneous determina-
tion of the real and imaginary parts of the third-order susceptibil-
ity
v
(3).11 All of the samples were measured at 10ꢁ6 M solution in
tetrahydrofuran solvent (specpure). The solvent itself does not
show any third-order nonlinearity under our experimental
conditions.
C192H238N20 (2825.2): C 81.60, H 8.49, N 9.91; found: C 81.75,
H 8.36, N 9.89.

Z. Jin et al. / Tetrahedron Letters 54 (2013) 4859–4864
4861
Scheme 1. Reagents and conditions: (a) TCNE, dichloromethane, rt, 1 h; (b) TCNQ, dichlorobenzene, 100 °C, 1 h.
Results and discussion
Synthesis
The stable and soluble nonplanar push–pull chromophores can
be obtained by the TCNE and TCNQ additions. It motivated us to
conjugate them into pyrene core to improve the solubility of the
conjugation sphere and enhance its electron uptake capacity.
When the strong donors were further conjugated, the resulting
push–pull chromophores underwent efficient intramolecular
charge transfer (CT) interactions and possessed high third-order
optical nonlinearities.12,13 Hence, alkynylpyrene derivative PT that
consisted of pyrene as an acceptor moiety, N,N-didodecyl aniline as
a peripheral donor moiety and an ethynyl group as a bridge was
first prepared for clicked precursor. Then, the new D–A-substituted
PTE and PTQ were obtained in nearly quantitative yield (89–94%)
by [2+2] cycloaddition between TCNE/TCNQ and N,N-didodecylan-
ilino-substituted alkynes PT (see Scheme 1 and Supplementary
Fig. S1), followed by an electrocyclic ring opening of the initially
formed cyclobutenes. The proposed structures and properties of
the compounds were characterized and evaluated with NMR,
MALDI-TOF-MS, EA, FTIR, UV/vis, CV, DFT, and NLO. The relation-
ship between the physical, optical properties and their molecular
structures were investigated in detail.
Figure 1. UV/vis spectral changes of PT upon titration with TCNE (0–1.0 equiv) in
CH2Cl2 at 25 °C. The inserts show the color changes before TCNE titration (a) and
after complete TCNE titration (b).
shown in Fig. 1, new CT bands appeared at 400–500 nm and 600–
700 nm, and increased with the increasing amount of the TCNE, fi-
nally leading to completely reddish-brown solutions. The presence
of the isosbestic points at 348 and 426 nm for PTE indicated no
side reactions during the TCNE click reaction. The position of most
intense CT bands (at 490 nm) was obvious red-shifted compared
with the precursor PT (at 319 nm) during the experiments, sug-
gesting intense interactions between the donor and acceptor. The
UV/vis spectral changes of PT upon titration with TCNQ show a
Photophysical properties
The photophysical properties of organic materials are essential
parameters that provide important information on the conforma-
tion and electronic structure. The titration experiments of PT with
TCNE and TCNQ were monitored by UV/vis spectroscopy, firstly. As

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Z. Jin et al. / Tetrahedron Letters 54 (2013) 4859–4864
polyene chain, but also enhance the intramolecular charge transfer
that may influence the nonlinear response.
Electrochemistry properties
As is well known, the levels of HOMO and LUMO are sensitive to
organic materials structure properties.19 Further characterization
with electrochemical method and density functional theory (DFT)
calculations was discussed. The electrochemical gap decreased
steadily from 1.79 eV (PT) to 0.69 eV (PTQ) (see Table 1). This de-
crease was a consequence of an increase in the D–A conjugation for
the different acceptor introduced, which is in good agreement with
energy-gap trends obtained from the lowest UV/vis absorption val-
ues. The first oxidation potential at +0.42 V for PTQ was smaller
red
than that for PTE (+0.53 V), and the first reduction potential (Eon
)
at ꢁ0.27 V was also lower than that for PTE (ꢁ0.44 V) owing to the
p-conjugated enhancement between the expanded quinoid ring
and the core. Low HOMO levels and narrow energy gaps suggest
that all compounds are promising strong electronic transition.20
Molecular orbital plots of simplified structures of PT and PTQ (cal-
culated with the Gaussian98 suite of programs at the B3LYP/6-
Figure 2. UV/vis absorption spectra of PT, PTE, and PTQ in CH2Cl2 (10ꢁ5 M) under
room temperature.
31G⁄ level of DFT) are shown in Fig. 3, with N(C12H25 2
) groups
replaced with NMe2.21 It is obvious that the HOMO and LUMO of
PT both localize at the central pyrene ring. The plots of PTQ indi-
cate that most of the highest occupied molecular orbital (HOMO)
density lies on the ‘donor’ end of each chromophore, and much
of the lowest unoccupied molecular orbital (LUMO) density lies
on the ‘acceptor’ end. These results give good evidence of the intra-
molecular charge-transfer nature of the HOMO–LUMO transitions,
and thus, the optical data should provide useful information about
their potential as nonlinear optical materials.
similar pattern to the TCNE, but only a distinct red-shifted was ob-
served in the absorption maxima values (see Supplementary
Fig. S2).
Subsequently, the UV/vis absorption spectra were shown in
Fig. 2. All derivatives displayed a characteristic pattern of multiple
absorption bands and revealed intense CT bands between 300 and
600 nm. The TCBD-substituted PTE and TCNQ adduct PTQ showed
the end-absorptions (kmax) around 640 nm and 752 nm respec-
tively, which were significantly bathochromically shifted com-
pared to the kmax-value of their parental nonacceptor
chromophore PT (528 nm). Both clicked products with end-
absorptions reaching into the near infrared indicated the intensity
Nonlinear optical properties
In investigations of the third-order nonlinear optical properties,
of
p-conjugation between donor and acceptor, which, in turn,
the third-order susceptibility
v(3) of PT, PTE, and PTQ were mea-
should lower the LUMO energy of the acceptor. Similarly, Bures
et al. indicated that smaller optical gaps were obtained by reducing
the efficiency of D–A conjugation through introduction of extended
spacers.14–16 Compared to the TCBD-substituted derivative PTE,
the lowest-energy CT absorption of PTQ was red-shifted to ca.
750 nm (the right-hand shoulder of the absorption) due to a slight
reduction in D–A conjugation efficiency and enhancement in the
sured by means of Z-scan technique. Supplementary Fig. S4
showed the open Z-scan curve of PTE and exhibited the classic sat-
urable absorption (SA) behavior. There was no obvious signal in
PTE’s closed Z-scan measurement (with an aperture). By contrast,
PT displayed neither nonlinear absorption nor nonlinear refraction,
but PTQ had both nonlinear absorption (Fig. 4 A) and nonlinear
refraction (Fig. 4 B), and exhibited SA behavior and positive nonlin-
ear refractive index respectively. A plausible explanation to this ef-
fect could be attributed to the existence of CT interactions between
the NNA donor and the introduced acceptor that were not entirely
present in the case of PT. Moreover, compared to PTE, PTQ had a
weaker D-A conjugation, which donor and acceptor were separated
by larger spacers, and the energy levels of HOMO and LUMO
resembled with those in the free components so as to a smaller
p–
p⁄ interaction, caused by the substituent of the conjugated quin-
oid character. On the other hand, PTQ and PTE exhibited a very
low-intensity charge-transfer band around 600–800 nm, explained
by the lack of linear charge-transfer pathways from the donors to
the acceptors.17 The higher-energy
p–
p⁄ transition of PTQ and
PTE was red-shifted from 402 to 490 nm due to the intramolecular
CT interaction between the different acceptor and NNA parts.9,18
Overall, the obtained results confirm that the introduction of TCBD
and TCNQ-adduct acceptors can not only increase the D–A conju-
gated extent which communicate through their connecting
optical gap. At the same time, the insertion of large
might influence the polarizability of the pyrene core
p
spacers
-cloud,
p
Table 1
Physical and electrochemical properties of compounds PT, PTE, and PTQ
a
d
e
kabs (nm)
emax
Eg (eV)
Eg (eV)
Energy levels (eV)
ox
on
c
ox
on
c
Materials
Tm (°C)
E
(eV)
E
(eV)
(L molꢁ1 cmꢁ1
)
HOMO
LUMO
PT
PTE
PTQ
192
220
238
319b, 408, 528
296, 490b, 640
402b, 526, 752
56332
49394
118494
0.24
0.53
0.42
ꢁ1.55
ꢁ0.44
ꢁ0.27
1.79
0.97
0.69
2.13
1.21
0.93
ꢁ4.86
ꢁ5.15
ꢁ5.04
ꢁ3.07
ꢁ4.18
ꢁ4.35
a
b
c
Measured by DSC at a rate of 10 °C/min.
The strongest absorption wavelength measured in CH2Cl2 solution.
Onset potentials measured in CH2Cl2, 1 ꢀ 10ꢁ5 M, Bu4NPF6 (0.1 M), 295 K, scan rate = 40 mv/s, versus ferrocene/ferrocenium (Fc/Fc+).
d
e
Band gap calculated from the energy level of cyclic voltammograms.
Band gap estimated from the onset wavelength of optical absorption in CH2Cl2 solution.

Z. Jin et al. / Tetrahedron Letters 54 (2013) 4859–4864
4863
Figure 3. Molecular orbital distributions for PT, PTQ, and energy levels estimated by density functional theory (DFT) calculations.
prepared to show unique patterns in photophysics. The investiga-
tion added a new aspect to pyrene conjugation, in which the inten-
sity of the donor–acceptor interaction played a key role, and the
use of TCNE and TCNQ click reagents with difference electron-
withdrawing intensity enabled new intramolecular CT interactions
which were unambiguously elucidated by UV/vis spectra and CV
measurements. Furthermore, Z-scan results demonstrated that
the strong D-A conjugation and large
p spacers decreased the opti-
cal gap and forcefully enhanced third-order optical nonlinearities
of the push–pull pyrene derivative. This approach provides a sim-
ple method for functional modification on pyrene and opens the
door to the design of novel optoelectronic switching molecular de-
vices via special click reaction.
Acknowledgments
This work was supported by National Natural Science Fund for
Distinguished Young Scholar (Grant No. 51025313); National
Natural Science Foundation (Grant No. 51103010, 51173003);
Specialized Research Fund for Doctoral Program of Higher
Education of China (Grant No. 20110006120002).
Figure 4. Z-scan data of (A) open and (B) closed apertures of PTQ.
contributing directly to strongly enhance third-order optical non-
linear response.12,13,3 Indeed, such CT interactions have already
been shown to affect changes in other physical properties such
as absorption and the electrochemical potential. It was worth
Supplementary data
Supplementary data (experimental details of the compound PT;
CV curves of compounds PT, PTE, PTQ; UV/vis spectra changes of
PT upon titration with TCNQ; Measurement of third-order nonlin-
ear optical and parameters calculation) associated with this article
can be found, in the online version, at http://dx.doi.org/10.1016/
j.tetlet.2013.06.121.
noticing that compound PTQ showed a
v(3)-value of the order of
8.30 ꢀ 10ꢁ21 m2Vꢁ2, which was ꢃ40 times larger than the third-
order susceptibility of fused silica (1.9 ꢀ 10ꢁ21 m2Vꢁ2) and was
comparable to other potent NLO chromophores.7,12,22 To the best
of our knowledge, few materials have been reported to date about
pyrene derivatives that have a high third-order susceptibility. The
properties of the compound PTQ that we developed make it very
attractive in the view of application in integrated nonlinear optical
devices.
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Z. Jin et al. / Tetrahedron Letters 54 (2013) 4859–4864
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