Synthesis and characterization of naphthalene diimide (NDI)-based near infrared chromophores with two-photon absorbing properties

Article abstract of DOI:10.1016/j.tet.2010.09.041

A new series of 2,7-bis-(2-ethylhexyl)-benzo[lmn][3,8]-phenanthroline-1,3, 6,8-tetraone (NDI) based pseudo-quadrupolar molecules (1-6) is presented and their two-photon absorption (2PA) cross-sections measured with the Z-scan method. The spectral properties of these compounds can be fine-tuned via modification of the donor segments. The corresponding 2PA cross-section (σ₂) values at the most readily available 800 nm excitation range from 229±15 to 1092±59 GM owing to differences in conjugation length and/or position of substitution.

Full text of DOI:10.1016/j.tet.2010.09.041

Tetrahedron 66 (2010) 8629e8634
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis and characterization of naphthalene diimide (NDI)-based near infrared
chromophores with two-photon absorbing properties
,
a,
Chao-Chen Lin a, Marappan Velusamy b, Hsien-Hsin Chou b, Jiann T. Lin b , Pi-Tai Chou
*
*
a Department of Chemistry, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan
b Institute of Chemistry, Academia Sinica, No. 128, Sec. 2, Academia Road, Taipei 115, Taiwan
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 30 July 2010
Received in revised form 8 September 2010
Accepted 10 September 2010
Available online 17 September 2010
A new series of 2,7-bis-(2-ethylhexyl)-benzo[lmn][3,8]-phenanthroline-1,3,6,8-tetraone (NDI) based
pseudo-quadrupolar molecules (1e6) is presented and their two-photon absorption (2PA) cross-sections
measured with the Z-scan method. The spectral properties of these compounds can be fine-tuned via
modification of the donor segments. The corresponding 2PA cross-section (s2) values at the most readily
available 800 nm excitation range from 229ꢀ15 to 1092ꢀ59 GM owing to differences in conjugation
length and/or position of substitution.
Keywords:
Ó 2010 Elsevier Ltd. All rights reserved.
Two-photon absorption
Naphthalene diimide
Near-IR emission
Pseudo-quadrupolar
1. Introduction
high s2 values, we report herein the synthesis and characterization
of naphthalene diimide (NDI) based DeAeD type molecules. In
Two-photon absorbing chromophores are of current research
interest due to their potential applications in photodynamic ther-
apy,1 scanning excitation microscopy,2 and three-dimensional op-
tical data storage,3 etc. In addition, bio-imaging techniques based
on two-photon absorption methods are superior to those based on
single-photon absorption4 owing to better in-depth penetration,
minimum cell damage, and higher spatial resolution.5 In recent
years, a wide array of donoreacceptoredonor (DeAeD) and
particular, they are strategically designed to be near-IR emitting
and capable of absorbing two-photons.
NDI has attracted much interest because of its thermal stability,
good electron accepting properties, and solution processability.10
Moreover, the electronic properties can be fine-tuned by in-
troducing substituents at either the naphthalene core or the
donorep-donor (Dep
-D) compounds6 have been synthesized to
attain high two-photon absorption cross-section (s2). The results of
structure property relationship studies reveal that s2 values in-
crease with increasing donor/acceptor strength, conjugation
length, and better planarity of the
p
center.7 In yet another ap-
proach, to expand the utility of two-photon absorbing materials in
areas, such as biomarkers and biomedical applications, it is favor-
able to develop chromophores with emission wavelength in the red
or near-IR region (e.g., 700e1200 nm); otherwise, the auto-
fluorescence of the cells would be interfering, especially in the
blue-green range. Previously, we reported dibutoxydi-benzo[a,c]
phenazine derivatives exhibiting promising s2 values.8 In contin-
uation of our efforts9 on the preparation of chromophores with
* Corresponding authors. Tel.: þ886 2 27898522; fax: þ886 2 27831237 (J.T.L.);
tel.: þ886 2 33663894; fax: þ886 2 23695208 (P.-T.C.); e-mail addresses: jtlin@
chem.sinica.edu.tw (J.T. Lin), chop@ntu.edu.tw (P.-T. Chou).
Fig. 1. Structures of compounds 1e6.
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.09.041

8630
C.-C. Lin et al. / Tetrahedron 66 (2010) 8629e8634
nitrogen atom of the imide group.11 The NDI containing materials
have been extensively used as organic field effect transistors,12
supramolecular assemblies,13 molecular switches,14 and sensors.15
In this work, we have successfully synthesized a series of two-
photon absorbing chromophores 1e6 (Fig. 1) that consist of triar-
ylamines and an NDI-based core of 2,7-bis-(2-ethylhexyl)-benzo
[lmn][3,8]-phenanthroline-1,3,6,8-tetraone acting as the electron
donors and acceptor, respectively.
Table 1
Photophysical and redox properties for compounds 1e6
labs (10ꢁ4
[nm]
e)
lem
Ff
Eox
[V]
Ered
[V]
HOMO/
LUMO
s2
a
a
a,b
c
c
d
[nm]
[%]
[GM]
(Egap) [eV]
1
590 (1.18)
400 (0.90)
340 (4.30)
306 (4.61)
673 (1.49)
400 (1.90)
368 (2.67)
620 (1.72)
400 (3.27)
371 (6.37)
302 (4.69)
606 (1.93)
400 (8.40)
388 (10.24)
310 (5.63)
616 (1.58)
400 (2.23)
343 (5.92)
310 (8.06)
614 (1.81)
400 (7.91)
390 (9.26)
312 (5.46)
741
0.23
þ0.57
ꢁ1.17
ꢁ1.53
5.36/
3.60
(1.76)
229
ꢀ15
2
3
N/A
776
d
þ0.38
þ0.48
ꢁ1.12
ꢁ1.51
5.17/
3.66
d
2. Results and discussions
2.1. Synthetic procedures
(1.51)
5.25/
3.62
0.02
þ0.45
þ1.05
ꢁ1.07
ꢁ1.49
982
ꢀ41
(1.63)
The synthetic routes of the titled compounds are depicted in
Scheme 1. In brief, bromination of 1,4,5,8-naphthalene tetracarbox-
ylic dianhydride using dibromocyanuric acid in concentrated sulfuric
acid led to the formation of the intermediate 2,6-dibromonaph-
thalene 1,4,5,8-tetracarboxylic dianhydride. 4,9-Dibromo-2,7-bis(2-
ethylhexyl)benzo[lmn]-[3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone
was then prepared by reacting 2-ethyl-hexyl amine in the presence
of acetic acid.16 Further Stille’s cross-coupling reaction of the
obtained dibromo compound with appropriate stannyl reagents
afforded the desired products in good yield (>65%).
4
5
6
780
787
766
0.08
0.03
0.03
þ0.37
þ0.90
ꢁ1.09
ꢁ1.53
5.17/
3.49
(1.67)
624
ꢀ27
þ0.23
þ0.80
ꢁ1.09
ꢁ1.50
5.03/
3.37
(1.66)
1092
ꢀ59
þ0.34
þ0.83
ꢁ1.05
ꢁ1.48
5.14/
3.43
(1.70)
651
ꢀ32
a
Measured in toluene.
e
: molar extinction coefficients.
lex¼500 nm. DCM (4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminos-
of 0.43, served as the reference.
b
O
O
Br
tyryl)-4H-pyran, lem¼615 nm) in MeOH, with
F
R
N
N
N
R
c
Measured in CH2Cl2. Potentials are quoted with reference to the internal ref-
O
O
O
O
erence, ferrocene (E1/2¼þ256 mV vs Ag/AgNO3).
DMF
N
Br
d
Averaged value of five replicas measured with the Z-scan method at 800 nm.
O
O
pep transition and the latter is of charge-transfer (CT) charac-
*
S
S
S
3, R =
2, R =
4, R =
1, R =
N
N
N
N
ter.8,16,17 The peak wavelength of the lowest energy absorption
attributable to the charge-transfer transition increases in the order
of 1<3<2, in consistent with the trend observed for 11,12-
dibutoxydibenzo[a,c]phenazine bridged amines.8 The combination
of diphenyl amino entity and thiophene ring constitutes a stronger
electron donor such that the HOMO of 2 is pushed to the highest
energyand accordingly the absorption onset is greatly red-shifted to
>825 nm. In comparison, non-coplanarity between the phenylene
ring plus thiophene and the NDI core results in less effective
interaction between the donor and the acceptor. Further replacing
the phenyl ring in 3 with fluorene or carbazole moieties, forming
4e6, the charge-transfer absorption profiles at >500 nm remain
approximately the same, indicating that the effective conjugation
length is not increased by simply extending the conjugation net-
work. The trend of the corresponding fluorescence spectra is con-
sistent with that observed in the absorption spectra. Note that the
emission quantumyields are relativelylowowing tothe operation of
energygap law.18 Generally, smaller S0eS1 energygap leads to better
overlap of the vibrational wavefunctions between S1 and S0 states
and hence accelerated internal conversion (IC), which leads to fast
nonradiative deactivation.
S
S
N
6, R =
5, R =
N
N
N
Scheme 1. Synthesis of compounds 1e6.
2.2. One-photon spectra and electrochemical studies
Absorption and emission spectra of compounds 1e6 are depicted
in Fig. 2 and Fig. S1 (see Supplementary data), respectively, and
pertinent data are summarized inTable 1. All the compounds exhibit
two major prominent absorption bands appearing at 380e387 nm
and 592e617 nm. The former one is ascribed to a localized aromatic
120000
1
2
100000
3
4
The electrochemical properties of compounds 1e6 are also
compiled in Table 1 while cyclic voltammograms and differential
pulse voltammograms of 1 and 4 are shown in Fig. 3. The two
reversible reduction waves observed correspond to the sequential
injection of electrons into the imides.19 Except for 1, all other
compounds exhibit two oxidation potentials originating from the
end-capping thiophene ring and the arylamine. The presence of
single oxidation wave in 1 likely stems from the absence of the
thiophene ring. The peak separation between the first and second
oxidation waves in 2 is much smaller than that in 3e5, implying
that electrons are less delocalized in 2 compared to others. The first
oxidation potential is used to calculate the highest occupied
molecular orbital (HOMO) energy level of the molecules (cf.
80000
5
6
60000
40000
20000
0
300
400
500
600
700
800
Wavelength (nm)
Fig. 2. Absorption spectra of compounds 1e6 in toluene at room temperature.

C.-C. Lin et al. / Tetrahedron 66 (2010) 8629e8634
8631
experimental results for compounds 1 and 5, and all the cross-
section values are tabulated in Table 1. The s2 values are in the order
of 1<4e6<3<5. Typically, the s2 value increases with conjugation
length and depends on the nature of the aryl spacer between the
donor and acceptor segments. Extended p-conjugation may result
in a greater density of population for both electronic and vibra-
tional states, providing more effective coupling channels between
ground and two-photon allowed states,23 the result of which would
in turn increase the 2PA cross-section. For 1 and 3, it can be seen
that extending the p-conjugation simply by adding one thiophene
ring significantly enhances the s2 value from 229 to 982 GM
(10ꢁ50 cm4 s photonꢁ1). As for the comparison among 3e6, for
which the effect of elongated conjugation is not significant, the
results may be rationalized by the theoretical expression of s2 in
Eq.1,1a
ꢀ ꢁ
2
p
h
n
2L4
1
G
s2ðmaxÞ
¼
Sfg
e20n2c2
Fig. 3. Cyclic voltammograms of 1 and 4 in CH2Cl2. Reference electrode: nonaqueous
Ag/AgNO3; supporting electrolyte: 0.1 M tetrabutylammonium hexafluorophosphate;
scan rate: 100 mV sꢁ1. The peaks of the lowest potential are due to internal ferrocene.
Inset: Differential pulse voltammograms of 1 and 4.
with
D
E
2
4
3
5
"
#
!
2
ꢀ
ꢁ
X
X
m2gim2if
Sfg
¼
¼
2þ
mgimif
Dmgf mgf
1
5
ꢂ
ꢃ
ꢂ
ꢃ
2
h
n
Egi ꢁ h
n
ferrocene 4.8 eV).20 These HOMO values along with the absorption
onset are then used to obtain the lowest unoccupied molecular
orbital (LUMO) energy levels21 listed in Table 1.
Egi ꢁ h
n
i
isf;g
(1)
where subscripts g, f and i denote the ground, final, and an assisting
intermediate state, respectively; stands for the amplitude of the
m
2.3. Two-photon absorption
transition dipole moment between the specified states; Dmgf is the
change in the static dipole moment in the final state relative to
the ground state; n represents the refractive index and L¼(n2þ2)/3.
In these pseudo-quadrupolar molecules, Dmgf is minimized and
the second term becomes dominant. In this study with 800 nm ex-
citation, the lowest lying charge-transfer transition centered around
600 nm serves as an intermediate state i to assist with 2PA. For 3 and
4, the one-photon extinction coefficients (see Fig. 2 and Table 1) of
the charge-transfer band remain much of the same, implying similar
mgi values. On the other hand, the absorption profiles <450 nm are
distinct, with 3<4 in the extinction coefficient, suggesting that the
varying s2 values may be resulting from different mif. It is worthy to
note that higher electronically excited states are often congested,
among which states with vanishing one-photon oscillator strengths
may be responsible for 2PA and act as the final state f in quadrupolar
molecules or nearly symmetric pseudo-quadrupolar ones.24 For in-
stance, it is calculated (Table S1, Chart S1, and Figures S2) that for
compound 3 at wavelengths below 408 nm, some states with os-
cillator strength <0.01 emerge (Table S2). As for compounds 4e6,
owing to their larger molecular frameworks, those states are found
beyond S10 and are not reported. Compound 6 (651 GM) has a similar
s2 value to 4, plausibly because the carbazolyl nitrogen does not
Two-photon absorption cross-sections (s2) of 1 and 3e6 in
toluene were determined by the open-aperture Z-scan method22
using the most readily available 800 nm Ti/Sapphire femtosecond
laser excitation. Compound 2 was not investigated because of its
overlapping one-photon absorption at 800 nm. Fig. 4 shows the
(a)
1.00
0.99
0.98
0.97
0.96
pulse energy = 1.50 μJ
β = 0.0118 cm GW-1
0.95
-7 -6 -5 -4 -3 -2 -1
0
1
2
3
4
5
6
7
Z (cm)
contribute
p-electron density to the spacer due to its meta-dispo-
(b)1.00
sition. On the other hand, 5 has a slightly higher s2 value (1092 GM).
Unlike 6, compound 5 possesses a diphenyl amino entity trans to the
carbazolyl nitrogen, which significantly increases the electron-do-
nating strength of the carbazoleeamine composite. This viewpoint
is further supported by the lowest oxidation potential for 5 among
all. Clearly, both the site of substitution and variation of the aryl
spaceraffect theefficiencyof chargeredistributionfromthe donorto
the acceptor. In addition, for compounds 3e6 with comparable
charge-transfer character, a general trend is observed that higher s2
value at 800 nm (5>3>6>4) is correlated to smaller one-photon
absorption extinction coefficient at 400 nm (4>6>3>5). In other
words, the two-photon allowed and one-photon forbidden states,
which contribute less to the UVevis absorption spectrum, are
pinpointed.
0.98
0.96
0.94
0.92
0.90
pulse energy = 1.25 μJ
β = 0.0300 cm GW-1
-7 -6 -5 -4 -3 -2 -1
0
1
2
3
4
5
6
7
Z (cm)
Fig. 4. Z-scan experimental data of compounds (a)
5 (1.21ꢂ10ꢁ3 M) in toluene with 800 nm excitation.
1
(2.15ꢂ10ꢁ3 M) and (b)
The s2 values at 800 nm in these compounds are relatively small
compared to 2PA chromophores with 11,12-dibutoxydibenzo[a,c]-

8632
C.-C. Lin et al. / Tetrahedron 66 (2010) 8629e8634
phenazine as the electron acceptor core.8 Nevertheless, their near-
IR emission provides better penetration. Conversely, these com-
pounds have larger s2 values than congeners with a 2,1,3-benzo-
thiazole core,6a suggesting the importance of a stronger acceptor in
enhancing the 2PA effect.
a 100 mL round-bottom flask. Under a nitrogen atmosphere,
a 10 mL of DMF was added and the contents were heated to 80 ꢃC
and maintained at this temperature for 12 h. After the reaction was
complete the reaction mixture was diluted with methanol. The
precipitate obtained was filtered, washed with methanol, and
dried. The residue was then purified by column chromatography on
silica gel using CH2Cl2/hexanes (1:3) mixture as the eluent to give 1
as a blue solid in 70% yield. FABMS (m/z): 976.4 [M]þ; 1H NMR
3. Conclusion
In conclusion, we have synthesized a new series of DeAeD type
compounds with NDI-based acceptor core and N,N-aryl amino
group terminal donors. Their photophysical properties can be fine-
tuned by playing on the nature, either length or position of sub-
stitution, of the conjugated spacers between donor and central
acceptor moieties. All these compounds show moderate to strong
2PA cross-sections (229e1092 GM) that are comparable to other
reported DeAeD type analogues. More importantly, the corre-
sponding emissions are all in the near-IR region (>740 nm). We
thus believe that the present system will serve as a building block
for developing materials suitable for two-photon imaging.
(CDCl3)
2H), 4.0e4.10 (m, 4H), 7.05e7.13 (m, 8H), 7.19e7.21 (m, 8H),
7.26e7.31 (m, 12H), 8.65 (s, 2H). 13C NMR (CDCl3)
: 10.9, 14.4, 23.4,
24.3, 28.9, 31.0, 38.1, 44.6, 122.3, 122.7, 123.9, 125.5, 125.7, 127.6,
129.7, 130.0, 133.8, 136.5, 147.5, 147.7, 148.4, 163.2, 163.4. Anal. Calcd
for C66H64N4O4: C, 81.12; H, 6.60; N, 5.73. Found: C, 81.03; H, 6.57;
N, 5.88.
d: 0.81e0.89 (m, 12H), 1.24e1.36 (m, 16H), 1.85e1.88 (m,
d
4.2.2. 4,9-Bis(5-(diphenylamino)thiophen-2-yl)-2,7-bis(2-ethylhexyl)
benzo[lmn][3,8] phenanthroline-1,3,6,8(2H,7H)-tetraone (2). Yield:
68%. FABMS (m/z): 988.41 [M]þ; 1H NMR (CDCl3)
d: 0.80e0.87 (m,
12H), 1.22e1.34 (m, 16H), 1.82e1.88 (m, 2H), 4.0e4.10 (m, 4H),
6.59e6.60 (d, 2H, J¼4.0 Hz), 7.07e7.10 (m, 4H), 7.23e7.24(m, 2H),
4. Experimental section
4.1. General procedures
7.27e7.32 (m, 16H), 8.71 (s, 2H). 13C NMR (CDCl3)
d: 10.6, 14.1, 23.0,
24.0, 28.7, 30.8, 37.8, 44.5,117.7, 121.1, 123.8, 124.2,124.9,127.3, 132.0,
136.2, 139.4, 147.3, 156.3, 162.9. Anal. Calcd for C62H60N4O4S2: C,
75.27; H, 6.11; N, 5.66. Found: C, 75.17; H, 6.07; N, 5.86.
Unless otherwise specified, all the reactions were performed
under nitrogen atmosphere using standard Schlenk techniques. All
solvents used were purified by standard procedures, or purged with
nitrogen before use. 1H NMR spectra were recorded on a Bruker
400 MHz spectrometer operating at 400.135 MHz. Absorption and
emission spectra were recorded on a Cary 50 probe UVevis spec-
trophotometer and an Edinburgh (FS920) fluorimeter, respectively.
All chromatographic separations were carried out on silica gel
(60 M, 230e400 mesh). Mass spectra (FAB) were recorded on
a VG70-250S mass spectrometer. Cyclic voltammetry experiments
were performed with a CH Instruments electrochemical analyzer.
All measurements were carried out at room temperature with
a conventional three electrode configuration consisting of a plati-
num working electrode, a platinum wire auxiliary electrode, and
a nonaqueous Ag/AgNO3 reference electrode. The E1/2 values were
determined as (EpaþEpc)/2, where Epa and Epc are the anodic and
cathodic peak potentials, respectively. The potentials are quoted
against the ferrocene internal standard. The solvent in all experi-
ments was CH2Cl2, and the supporting electrolyte was 0.1 M tet-
rabutylammonium hexafluorophosphate. Elementary analyses
were performed on a PerkineElmer 2400 CHN analyzer.
4.2.3. 4,9-Bis(5-(4-(diphenylamino)phenyl)thiophen-2-yl)-2,7-bis(2-
ethylhexyl)benzo[lmn][3,8] phenanthroline-1,3,6,8(2H,7H)-tetraone
(3). Yield: 75%. FABMS (m/z): 1140.47 [M]þ; 1H NMR (CDCl3)
d:
0.80e0.87 (m, 12H), 1.22e1.34 (m, 16H), 1.82e1.88 (m, 2H), 4.0e4.10
(m, 4H), 7.02e7.06 (m, 7H), 7.11e7.13 (m, 8H), 7.24e7.29 (m, 11H),
7.32e7.33 (d, 2H, J¼3.6Hz), 7.49e7.51 (d, 4H, J¼8.8Hz), 8.79(s,2H).13C
NMR (CDCl3) d: 11.1, 14.5, 23.5, 24.4, 29.0, 31.1, 38.2, 45.0, 122.8, 123.0,
123.7, 123.7, 125.2, 125.7, 127.2, 127.9, 128.1, 129.8, 130.7, 137.0, 139.5,
140.1, 147.8, 148.2, 148.3, 163.0, 163.1. Anal. Calcd for C74H68N4O4S2: C,
77.86; H, 6.00; N, 4.91. Found: C, 77.87; H, 6.00; N, 5.01.
4.2.4. 4,9-Bis(5-(7-(diphenylamino)-9,9-dihexyl-9H-fluoren-2-yl)
thiophen-2-yl)-2,7-bis(2-ethylhexyl)benzo[lmn][3,8]phenanthroline-
1,3,6,8(2H,7H)-tetraone (4). Yield: 70%. MALDI MS (m/z): 1655.38
[MþH]þ; 1H NMR (CDCl3)
d: 0.62e0.94 (m, 32H), 1.06e1.16 (m,
24H), 1.24e1.40 (m, 16H), 1.82e1.96 (m, 10H), 4.07e4.16 (m, 4H),
6.09e7.02 (m, 6H), 7.11e7.13 (m, 10H), 7.22e7.26 (m, 10H),
7.37e7.38 (d, 2H, J¼3.6 Hz), 7.43e7.44 (d, 2H, J¼3.6 Hz), 7.55e7.62
(m, 8H), 8.84 (s, 2H). 13C NMR (CDCl3)
d: 10.9, 14.3, 14.3, 22.8, 23.3,
24.0, 24.2, 28.9, 29.9, 30.9, 31.8, 38.0, 40.6, 44.9, 55.4, 119.4, 119.8,
120.3, 120.7, 122.8, 123.4, 123.8, 124.1, 125.2, 125.6, 127.8, 130.5,
132.2, 135.9, 136.8, 139.6, 140., 141.5, 147.7, 148.2, 149.0, 151.7, 152.7,
162.9. Anal. Calcd for C112H124N4O4S2: C, 81.31; H, 7.55; N, 3.39.
Found: C, 81.30; H, 7.56; N, 3.50.
4.2. Synthetic details and characterization
4,9-Dibromo-2,7-bis(2-ethylhexyl)benzo-[lmn][3,8]phenan-
throline-1,3,6,8(2H,7H)-tetraone, N,N-di-phenyl-4-(tributyl-stannyl)
aniline, N,N-diphenyl-5-(tributyl-stannyl)thio-phen-2-amine, N,
N-diphenyl-4-(5-(tributyl-stannyl)thiophen-2-yl)aniline, 9-ethyl-N,N
-diphenyl-7-(5-(tributylstannyl)thio-phen-2-yl)-9H-carbazol-2-
4.2.5. 4,9-Bis(5-(6-(diphenylamino)-9-ethyl-9H-carbazol-3-yl)thio-
phen-2-yl)-2,7-bis(2-ethylhexyl) benzo[lmn][3,8]phenanthroline-1,3,6,8
(2H,7H)-tetraone (5). Yield: 80%. FABMS (m/z): 1374.57 [M]þ; 1H
amine,
2-yl)-9H-fluoren-2-amine,
9,9-dihexyl-N,N-diphenyl-7-(5-(tributylstannyl)thiophen-
9-hexyl-N,N-diphenyl-7-(5-(tributyl-
NMR (CDCl3) d: 0.85e0.92 (m,12H),1.25e1.39 (m,16H),1.45e1.49 (m,
stannyl)-thiophen-2-yl)-9H-carbazol-2-amine were prepared by
adopting reported procedures.8,25 The final compounds 1e6 were
obtained with similar processes, for which an illustrative example is
given below for 1. Characterizations of compounds 2e6 are also
included.
6H), 1.91e1.94 (m, 2H), 4.05e4.12 (m, 4H), 4.35e4.37 (m, 4H), 6.94 (t,
4H, J¼6.7 Hz), 7.09e7.11 (m, 8H), 7.20e7.24 (m, 7H), 7.29e7.40 (m,
11H), 7.74e7.77 (m, 2H), 7.92 (s, 2H), 8.21e8.22 (m, 2H), 8.82 (s, 2H).
13C NMR (CDCl3)
d: 11.1, 14.4, 14.5, 23.5, 24.4, 29.0, 31.1, 38.2, 45.0,
109.4, 110.0, 118.7, 119.3, 122.1, 122.6, 122.8, 123.2, 123.6, 124.2, 124.8,
125.5, 125.7, 126.3, 127.9, 129.5, 130.9, 137.0, 138.0, 139.2, 140.1, 140.7,
149.1, 149.8, 163.1. Anal. Calcd for C90H82N6O4S2: C, 78.57; H, 6.01; N,
6.11. Found: C, 78.05; H, 6.08; N, 5.98.
4.2.1. 4,9-Bis(4-(diphenylamino)phenyl)-2,7-bis(2-ethylhexyl)benzo
[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone (1). 4,9-Dibromo-
2,7-bis(2-ethylhexyl)benzo[lmn]-[3,8]phenan-throline-1,3,6,8(2H,7H)-
tetraone (0.64 g, 1.0 mmol), N,N-diphenyl-4-(tributylstannyl)ani-
line (1.17 g, 2.2 mmol), and Pd(PPh3)2Cl2 (20 mg) were charged in
4.2.6. 4,9-Bis(5-(7-(diphenylamino)-9-hexyl-9H-carbazol-2-yl)thio-
phen-2-yl)-2,7-bis(2-ethylhexyl)benzo[lmn][3,8]phenanthroline-

C.-C. Lin et al. / Tetrahedron 66 (2010) 8629e8634
8633
1,3,6,8(2H,7H)-tetraone (6). Yield: 65%. FABMS (m/z): 1487.71 [M]þ;
1H NMR (CDCl3)
: 0.86e0.94 (m, 18H), 1.19e1.40 (m, 28H),
1.76e2.02 (m, 6H), 4.10e4.17 (m, 8H), 6.95e6.99 (m, 6H), 7.02e7.15
(m, 10H), 7.23e7.27 (m, 8H), 7.40e7.41 (d, 2H, J¼3.6 Hz), 7.46e7.53
(m, 4H), 7.58 (s, 2H), 7.9e7.99 (m, 4H), 8.85 (s, 2H). 13C NMR (CDCl3)
Bonne, A.; Sanden, B.; Astilean, S.; Baldeck, P. L.; Lemercier, G. Chem. Commun.
2009, 4590.
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d
d: 10.9, 14.2, 14.3, 22.7, 23.3, 24.2, 27.1, 28.9, 29.1, 30.9, 31.8, 38.0,
43.2, 44.9, 105.1, 106.1, 117.5, 117.9, 118.6, 120.3, 121.2, 122.6, 122.8,
123.3, 123.5, 124.2, 125.6, 127.8, 129.4, 130.6, 130.9, 136.8, 139.7,
139.9, 141.4, 142.5, 146.8, 148.4, 149.5, 162.9. Anal. Calcd for
C98H98N6O4S2: C, 79.10; H, 6.64; N, 5.65. Found: C, 79.00; H, 6.69; N,
6.00.
4. Reeve, J. E.; Collins, H. A.; Mey, K. D.; Kohl, M. M.; Thorley, K. J.; Paulsen, O.;
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4.3. Open-aperture Z-scan
The open-aperture Z-scan experiments were conducted with
the experimental setup and fitting procedures described in litera-
ture.22 In this study, a mode-locked Ti/Sapphire laser (Tsunami,
Spectra Physics) produced single Gaussian pulses, which were then
coupled to a regenerative amplifier that generated w180 fs, 1 mJ
pulses (800 nm, 1 kHz, Spitfire Pro, Spectra Physics). The pulse
energy, after proper attenuation, was reduced to 0.75e1.50 mJ and
the repetition rate was further reduced to 20 Hz. After passing
through an f¼30 cm lens, the laser beam was focused and passed
through
a 1.00 mm cell filled with the sample solution
(1.01ꢂ10ꢁ3e2.15ꢂ10ꢁ3 M) and the beam radius at the focal position
was 5.09ꢂ10ꢁ3 cm. When the sample cell was translated along the
beam direction (z-axis), the transmitted laser intensity was detec-
ted by a photodiode (PD-10, Ophir).
7. (a) Mongin, O.; Porre`s, L.; Charlot, M.; Katan, C.; Blanchard-Desce, M. Chem.
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The structures of the molecules were optimized using B3LYP/6-
31G . For each molecule, a number of possible conformations were
*
examined and the one with the lowest energy (i.e., global mini-
mum) was used. For the excited state, we employed the time-de-
pendent density functional theory (TDDFT) with the B3LYP
functional. All of them were performed with Q-Chem 3.0 soft-
ware.26 There exist a number of previous works that employed
TDDFT to characterize excited states with charge-transfer charac-
ter.27 In some cases underestimation of the excitation energies was
seen.27,28 Therefore, in the present work, we use TDDFT to char-
acterize the extent of the charge-shift and avoid drawing conclu-
sions from the excitation energy.
13. (a) Pantos, G. D.; Pengo, P.; Sanders, J. K. M. Angew. Chem., Int. Ed. 2007, 46, 194;
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Acknowledgements
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This work was financially supported by the National Science
Council of Taiwan, Academia Sinica, and National Taiwan University.
15. (a) Mukhopadhyay, P.; Iwashita, Y.; Shirakawa, M.; Kawano, S.; Fujita, N.;
Shinkai, S. Angew. Chem., Int. Ed. 2006, 45, 1592; (b) Lee, H. N.; Xu, Z.; Kim, S. K.;
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Supplementary data
Contained within are the emission spectra, details of the fitting
procedures for the z-scan method and quantum chemistry compu-
tation, as well as the 1H and 13C NMR spectra. Supplementary data
associated with this article can be found in online version, at
doi:10.1016/j.tet.2010.09.041. These data include MOL files and
InChIKeys of the most important compounds described in this article.
€
16. (a) Thalacker, C.; Roger, C.; Würthner, F. J. Org. Chem. 2006, 71, 8098; (b)
€
€
Chaignon, F.; Falkenstrom, M.; Karlsson, S.; Blart, E.; Odobel, F.; Hammarstrom,
L. Chem. Commun. 2007, 64.
17. (a) Chopin, S.; Chaignon, F.; Blart, E.; Odobel, F. J. Mater. Chem. 2007, 17, 4139; (b)
Velusamy, M.; Jutin Thomas, K. R.; Lin, J. T.; Wen, Y. S. Tetrahedron Lett. 2005, 46,
7647; (c) Justin Thomas, K. R.; Lin, J. T.; Velusamy, M.; Tao, Y.-T.; Chuen, C.-H.
Adv. Funct. Mater. 2004, 14, 83.
18. Siebrand, W. J. Chem. Phys. 1967, 47, 2411.
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