Synthesis and two-photon absorption property characterizations of small dendritic chromophores containing functionalized quinoxaliniod heterocycles

Article abstract of DOI:10.1002/chem.201202178

A series of star-shaped multi-polar chromophores (compounds 1-3) containing functionalized quinoxaline and quinoxalinoid (indenoquinoxaline and pyridopyrazine) units has been synthesized and characterized for their two-photon absorption (2PA) properties both in the femtosecond and the nanosecond time domain. Under our experimental conditions, these model fluorophores are found to manifest strong and wide-dispersed two-photon absorption in the near-infrared region. It is demonstrated that molecular structures with multi-branched π frameworks incorporating properly functionalized quinoxalinoid units would possess large molecular nonlinear absorptivities within the studied spectral range. Effective optical-power attenuation and stabilization behaviors in the nanosecond time domain of a selected representative dye molecule (i.e., compound 2) from this model compound set were also investigated and the results indicate that such structural motif could be a useful approach for the molecular design toward strong two-photon-absorbing material systems for quick-responsive and broadband optical-suppressing-related applications, particularly to confront long laser pulses. Copyright

Full text of DOI:10.1002/chem.201202178

FULL PAPER
DOI: 10.1002/chem.201202178
Synthesis and Two-Photon Absorption Property Characterizations of Small
Dendritic Chromophores Containing Functionalized Quinoxaliniod
Heterocycles
Tzu-Chau Lin,*[a] Ying-Hsuan Lee,[a] Che-Yu Liu,[a] Bor-Rong Huang,[a] Ming-Yu Tsai,[a]
Yu-Jhen Huang,[a] Ja-Hon Lin,*[b] Yu-Kai Shen,[b] and Cheng-Yu Wu[b]
Abstract: A series of star-shaped multi-
polar chromophores (compounds 1–3)
containing functionalized quinoxaline
and quinoxalinoid (indenoquinoxaline
and pyridopyrazine) units has been
synthesized and characterized for their
two-photon absorption (2PA) proper-
ties both in the femtosecond and the
nanosecond time domain. Under our
experimental conditions, these model
fluorophores are found to manifest
strong and wide-dispersed two-photon
absorption in the near-infrared region.
It is demonstrated that molecular struc-
tures with multi-branched p frame-
works incorporating properly function-
alized quinoxalinoid units would pos-
sess large molecular nonlinear absorp-
tivities within the studied spectral
range. Effective optical-power attenua-
tion and stabilization behaviors in the
nanosecond time domain of a selected
representative dye molecule (i.e., com-
pound 2) from this model compound
set were also investigated and the re-
sults indicate that such structural motif
could be a useful approach for the mo-
lecular design toward strong two-
photon-absorbing material systems for
quick-responsive and broadband opti-
cal-suppressing-related
applications,
Keywords: absorption · amination ·
particularly to confront long laser
pulses.
chromophores
·
heterocycles
·
nonlinear optics
Introduction
cluding optical power limiting, frequency upconverted
lasing, 3D data storage, 3D microfabrication, nondestructive
bioimaging and tracking, and two-photon-assisted photo-
A two-photon absorption (2PA) process occurs when a mol-
ecule is promoted from the ground state to an excited state
through simultaneous absorption of two photons. Although
the theory of this nonlinear optical phenomenon was pre-
dicted by Gçppert-Mayer in 1931,[1] its experimental evi-
dence came out about thirty years later when scientists ob-
served upconverted emission from media under irradiation
of laser light with wavelengths far from the linear absorp-
tion bands of the studied media.[2] In the past fifteen years,
the availability of high-peak power lasers has incited the
momentum to explore the two-photon technologies. Many
promising applications in the emerging field of photonics
and biophotonics based on a 2PA have been proposed in-
AHCTUNGTRENNUNG
dynamic therapy.[3] Because the commercially available ma-
terials do not provide sufficiently large 2PA to be of practi-
cal use in these applications, the need to develop new organ-
ic compounds that exhibit a strong 2PA within a specific
spectral region is consequently escalating. In the recent
decade researchers have put enormous efforts in exploring
the connection between the molecular structure and the
2PA by investigating various molecular systems with differ-
ent archetypes, including quasi-linear, multi-branched, and
dendritic geometries. The accumulated knowledge and expe-
rience has revealed that molecular 2PA is closely related to
both the intramolecular charge-transfer efficiency and the
effective size of the p-conjugation domain within a mole-
cule.[4–10] Among the aforementioned molecular architec-
tures, it has been experimentally revealed that chromo-
phores with branched p frameworks could manifest strong
multi-photon absorption[5d–f,i,6,7d,8a,b,f,9c,e–g,10–12] while retaining
the linear transparency over a wide spectral range[13] and
this is a beneficial feature especially for the broadband opti-
cal-control applications based on 2PA. On the other hand, a
branched structure also provides an access to incorporate
several 2PA-enhancing parameters into a single molecular
system and allows material chemists to optimize a dye mole-
cule that simultaneously combines various expected charac-
teristics for different specific applications. Moreover,
branched skeletons are potential building blocks for con-
[a] Prof. T.-C. Lin, Y.-H. Lee, C.-Y. Liu, B.-R. Huang, M.-Y. Tsai,
Y.-J. Huang
Photonic Materials Research Laboratory
Department of Chemistry, National Central University
Jhong-Li 32001 (Taiwan)
E-mail: tclin@ncu.edu.tw
[b] Prof. J.-H. Lin, Y.-K. Shen, C.-Y. Wu
Photonic Technology Laboratory
Department of Electro-Optical Engineering
National Taipei University of Technology
Taipei10608 (Taiwan)
E-mail: jhlin@ntut.edu.tw
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201202178.
Chem. Eur. J. 2013, 19, 749 – 760
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structing dendritic and/or supramolecular structures, which
are suggested as probable approaches to pursue fundamen-
tal limits of molecular 2PAs.[14] Following our continuous ef-
forts in searching new strategies toward highly efficient 2PA
materials, we have been interested in developing multi-
branched or dendritic organic structures with expanded p
systems that contains various types of heterocyclic moieties
and in exploring the structural parameters that may have
impacts on the 2PA properties.
In this paper, we report our studies of degenerate two-
photon absorption, upconverted emission, and effective op-
tical power-limiting properties of a newly synthesized multi-
branched model chromophore set by using high-peak power
IR laser pulses working in the femtosecond and nanosecond
time domain as the probing tools.
Results
Molecular structures and syntheses: The chemical structures
of the studied model compounds in the present work are il-
lustrated in Figure 1. Compound 1 is basically a three-
branched chromophore that uses a nitrogen atom as an elec-
tron-donating ramification center for the connection of
three identical 2,3-diphenylaminofluorenyl quinoxaline units
to construct a dendritic p framework. Compared with com-
pound 1, model compound 2 can be conceptually considered
Scheme 1. Synthetic routes toward key intermediates 7 and 12 (the yield
for each compound is indicated in parenthesis). DPPB=1,4-bis(diphenyl-
phosphino)butane; DBU=1,5-diazabicycloACTHNUTRGNEU[GN 5.4.0]undec-5-ene; dba=di-
benzylideneacetone; BINAP=2,2’-bis(diphenylphosphino)-1,1’-binaphth-
yl; DMAc=N,N-dimethylacetamide; EA=ethyl acetate.
Figure 1. Molecular structures of the studied model chromophores 1–3.
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Two-Photon Absorption of Small Dendritic Chromophores
as an expanded version of com-
FULL PAPER
pound
gated” heterocyclic units (i.e.,
indenoquinoxaline moieties)
1 because the “elon-
ACHTUNGTRENNUNG
were employed as the peripher-
al parts in this chromophore.
Differently, the structure of
compound 3 is built based on a
motif that uses pyridopyrazine
units to replace the benzopyr-
ACHTUNGTRENNUNGazine moieties (i.e., quinoxaline
units) in model compound 1 so
that the resulting structure can
be expected to possess more
heterocyclic characters and may
be an interesting subject to ex-
plore the connection between
this type of structural arrange-
ment and the molecular 2PA
behavior. The original molecu-
lar design strategies of these
chromophores were based on
the idea of incorporating elec-
tron-pulling heterocyclic units
into the branched molecular
structure so that the electronic
properties of the resulting fluo-
rophores may be altered and
tuned due to the existence of
heteroatoms and the whole
molecule will possess an ex-
tended p domain as well as
more pronounced multipolar
characters. Furthermore, the
pendent alkyl chains of all fluo-
renyl moieties in these model
chromophores are expected to
enhance the solubility in
Scheme 2. Synthetic procedures for the preparation of the primary intermediates with functionalized quinoxa-
linoid ring complexes (the yield for each compound is indicated in parenthesis).
common
organic
solvents,
which is another important
issue to be considered in the molecular design from both the
aspect of experiments and applications. The syntheses of the
target model compounds are relatively straightforward as il-
lustrated in Schemes 1–3, which mainly involve the prepara-
tion of the primary intermediates with the quinoxalinoid
ring complex structures (i.e., compounds 13, 14, 17, and 20)
followed by a series of appropriate functional group conver-
sions to provide the primary amines (i.e., compounds 15, 18,
and 21) for the consecutive Buchwald–Hartwig-type amina-
tion toward the final chromophores. For the construction of
each heterocyclic ring complex, the corresponding diamines
and diaryldiketone 7 are employed as the major synthons.
Among the selected diamines in this work, compound 12 is
not commercially available so that this key intermediate has
to be synthesized starting from compound 4 as outlined in
Scheme 1. As for the synthesis of compound 7, instead of
using our previous methodology to synthesize the diarylacet-
Scheme 3. Final coupling processes toward the target model chromo-
phores (the yield for each compound is indicated in parenthesis).
AHCTUNGTRENNUNG
ylene precursor 6,[10d] we have employed a recently devel-
oped one-step Sonogashira reaction protocol[15] to accom-
plish this precursor with saliently improved yield and then
utilized KMnO4 as the major oxidant to furnish the targeted
diketone 7. Once compounds 13, 14, 17, and 20 become
available, a series of functional group transformations are
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751

T.-C. Lin, J.-H. Lin et al.
performed to prepare the primary amines (i.e., compounds
15, 18, and 21 in Scheme 2) for the first-step Buchwald–
Hartwig amination to afford the secondary amines (i.e.,
compounds 16, 19, and 22 in Scheme 2). These secondary
amines are in turn used as the starting materials for the
second-step amination to prepare the tertiary amines (i.e.,
compounds 1–3) as the final model chromophores. It is
worthy to note that a different combination of the catalytic
tuitionally expected to show very limited solvatochromic
characters. Interestingly, these model fluorophores indeed il-
lustrate a strong solvent effect on their fluorescence proper-
ties including band positions and lifetimes as illustrated in
Figure 3 by using compound 2 as a representative for this
system (i.e., [Pd2ACHTUNGTRENNUNG(dba)3]–Xantphos) was employed for the
syntheses of compounds 3 and 22 in order to obtain higher
yields in our case. The detailed syntheses including the prep-
aration of the key intermediates and the final two-step cata-
lytic coupling reactions toward the targeted model fluoro-
phores are described in the Experimental Section.
Characterization of the optical properties
One-photon absorption (1PA) and fluorescence spectra
measurement: Linear absorption and fluorescence spectra of
the studied compounds in toluene (with a concentration of
1ꢁ10À6 m) are shown in Figure 2. The 1PA spectra were re-
~
Figure 3. Fluorescence spectra of compound 2 in various solvents (
=
*
^
toluene, =THF, =CH2Cl2); The color version of the spectra with a
photo that illustrates the distinct color change of compound 2 in the dif-
ferent solvents can be found in the Supporting Information (t1PA-FL =fluo-
rescence lifetime, t1PA-FL =1.22, 2.02, 3.01 ns in toluene, THF, CH2Cl2, re-
spectively; concentration of compound 2=1ꢁ10À6 m for all cases).
behavior. Similar properties have been observed from other
multi-polar chromophore systems and the symmetry-break-
ing phenomenon caused by electron–vibration coupling and
dipolar solvation effects were proposed to account for this
behavior.[5c,16]
Two-photon-excited fluorescence (2PEF) emission properties:
The studied model chromophores manifest strong two-
photon-excited upconversion emission, which can be easily
observed by naked eyes even under the illumination of a l
ꢀ790 nm unfocused femtosecond laser beam. Figure 4a il-
lustrates the 2PA-induced fluorescence spectra of the model
chromophores 1–3. Solutions of the samples in toluene were
freshly prepared at a concentration of 1ꢁ10À4 m for this
measurement and the excitation source utilized for this two-
photon-induced fluorescence study was obtained from a
mode-locked Ti:sapphire laser (Tsunami pumped with a
Millennia 10 W, Spectra-Physics) which delivers approxi-
mately 100 fs pulses with a repetition rate of 82 MHz and a
beam diameter of 2 mm. The intensity level of the excitation
beam was carefully controlled in order to avoid saturation
of the absorption and photodegradation. To minimize the
effect of re-absorption due to the relatively high concentra-
tion of the solutions used in this measurement, we have fo-
cused the excitation beam as close as possible to the wall of
the quartz cell (10 mmꢁ10 mm cuvette) so that only the
emission from the surface of the sample was recorded. It
can be seen in Figure 4a that for each model chromophore
the shape and spectral position of the measured 2PA-in-
duced emission is identical to its corresponding 1PA-induced
Figure 2. Linear absorption and fluorescence spectra (inset) of com-
pounds 1–3 in toluene (concentration of the sample in solution=1ꢁ
10À6 m; c=1, a=2, – · · =3).
corded by using a Shimadzu 3501 PC spectrophotometer
and the 1PA-induced fluorescence spectra were measured
by utilizing a Jobin–Yvon FluoroMax-4 spectrometer. All
these chromophores exhibit intense linear absorption in the
UV/Vis region with the lowest-energy peaks located at l=
452 (eꢀ1.25ꢁ105 cmÀ1 mÀ1), 469 (eꢀ2.91ꢁ105 cmÀ1 mÀ1), and
471 nm (eꢀ1.30ꢁ105 cmÀ1 mÀ1) for compounds 1–3, respec-
tively. The solutions of these compounds also emit intense
fluorescence under the irradiation of a common UV lamp
with blue-greenish color for compounds 1 and 2 and green-
yellowish color for compound 3, which is in agreement with
the measured emission spectra (see Figure 2, inset). From
the view point of the molecular structure, chromophores 1–3
possess symmetrical substitution patterns so that they are in-
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Two-Photon Absorption of Small Dendritic Chromophores
FULL PAPER
Figure 5. Measured degenerate two-photon absorption spectra of model
chromophores 1–3 by the 2PEF method in toluene at a concentration of
1ꢁ10À4 m (with an experimental error of ~15%; =1, =2, =3).
~
*
^
Table 1. Photophysical properties of the studied model chromophores 1–
3 in toluene.[a]
abs
max
[nm][b]
em
max
[nm][d]
[e]
l
e[c]
l
FF
t1PA-FL dm2 ax
[105 cmÀ1 mÀ1
]
[ns][f]
[GM][g]
Figure 4. a) Normalized two-photon-excited upconversion spectra of fluo-
rophores 1–3 in toluene at a concentration of 1ꢁ10À4 m; b)–d) are the
logarithmic plots of the power-squared dependence of the 2PA-induced
fluorescence intensity on the input intensity of these compounds in tol-
1
2
3
310, 365, 452 1.25
310, 364, 469 2.91
308, 366, 471 1.30
498
495
534
0.42
0.80
0.48
1.84
1.22
2.78
ca. 8950
ca. 13230
ca. 8500
~
[a] The concentration was 1ꢁ10À6 and 1ꢁ10À4 m for the 1PA-related and
the 2PA-related measurements, respectively. [b] One-photon absorption
maximum. [c] Molar absorption coefficient. [d] 1PA-Induced fluorescence
emission maximum. [e] Fluorescence quantum efficiency. [f] 1PA-Induced
fluorescence lifetime. [g] Maximum 2PA cross-section value (with an ex-
perimental error of approximately Æ15%); 1 GM=1ꢁ10À50 cm4 s per
photon molecule.
*
^
uene ( =1, slope=2.00 (b); =2, slope=2.01 (c); and =3, slope=
2.02 (d))
fluorescence band, which is shown in Figure 1. This result
implies that in our dye system the radiative relaxation pro-
ACHTUNGTRENNUNGcesses that occurred within the studied samples are from the
same final excited states regardless of the excitation
method.
vidual local 2PA maximum at different wavelengths with
2PA cross-section values of approximately 8950 GM at l=
790 nm for compound 1, approximately 13230 GM at l=
800 nm for compound 2, and approximately 8500 GM at l=
820 nm for compound 3.
The power-squared dependence of the 2PA-induced fluo-
rescence intensity on the excitation intensity of the studied
fluorophores was also examined. Figures 4b–d are logarith-
mic plots of the measured data and the results confirmed
that a 2PA process is responsible for the observed upcon-
verted fluorescence emissions in all cases.
Discussion
Degenerate two-photon absorption spectra measurement: The
distribution of the 2PA activities of the studied dye mole-
cules as a function of the wavelength was delineated in the
spectral region of l=720–890 nm by the degenerate two-
photon-excited fluorescence (2PEF) technique based on a
set-up very similar to that reported by Xu and Webb[17] (see
the Supporting Information). We have used fluorescein (ca.
80 mm in aqueous NaOH solution, pH 11) as standard for
this experiment.[17,18] Figure 5 shows the measured degener-
ate two-photon absorption spectra of the three model com-
pounds in toluene (at a concentration of 1ꢁ10À4 m) and the
combined photophysical data are summarized in Table 1. It
is notable that all the studied compounds exhibit strong 2PA
(d2 ꢁ800 GM) within the entire investigated spectral region.
Besides, each studied chromophore also possesses an indi-
From the measured photophysical properties of the studied
compounds in the present work, some features are notable.
1) Based on the observed linear absorption behaviors of
the studied chromophores and by using compound 1 as a
reference point, it can be noted that compound 2 exhibits a
saliently promoted linear absorption, although it remains
nearly the identical shape and spectral position to those of
compound 1, whereas compound 3 shows comparatively
smaller enhancement of the linear absorption and a red-
shifted lowest-energy band. These results imply that the in-
corporation of fluorene units into this molecular system (as
in the case of compound 2) is an effective approach to en-
hance the linear absorptivity without major shifting of the
absorption band, whereas the utilization of pyridine moie-
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753

T.-C. Lin, J.-H. Lin et al.
A
rangement in the case of this model compound set connects
to the molecular two-photon activities, our preliminary re-
sults show that such structural combination may help to pro-
mote the molecular 2PA. Another interesting issue that
needs to be further studied with respect to this multi-
branched model compound set is the importance of structur-
al coplanarity on the molecular 2PA behaviors and there-
fore, efforts toward realization of the structure–nonlinear
absorption properties by using quantum-mechanical analysis
of this chromophore system are needed, and such work is
underway currently.
case of compound 3) is useful for broadening the linear ab-
sorption spectral range by bathochromically pushing the
lowest-energy band. Besides, the observed solvatochromic
behaviors (see Table 1) suggest that the (relaxed) excited
states of these chromophores are highly dipolar.
2) The dispersion manner and relative magnitudes of the
2PA activities of the studied model chromophores within
the investigated spectral range follow similar pattern as they
possess in the linear absorption, that is, compound 2 pos-
ACHTUNGTRENNUNGsesses a distinctly hyperchromic and slightly bathochromic
2PA band, whereas compound 3 manifests a saliently red-
shifted 2PA band when compared with that of compound 1.
On the other hand, if one compares the measured 1PA and
2PA spectra of these fluorophores (see Figures 2 and 5), it
can be readily found that the peak positions of the two-
photon absorption maxima of the studied model chromo-
phores in Figure 5 are monotonically blue shifted (or at sig-
nificantly shorter wavelengths) compared to the wavelength
5) Based on the fact that the measured fluorescence emis-
sion spectra (shown in Figures 2 and 4) for each individual
model compound are nearly the same for one- and two-
photon excitations, one may conclude that in these cases,
the fluorescence emission is predominantly from the same
singlet state of each model chromophore.[19] On the other
hand, the medium-high quantum yield observed for com-
pound 2 also indicates that it could be an efficient frequency
upconverter for the biophotonic applications such as two-
photon-excited fluorescence microscopy.
position of twice of their lowest-energy linear absorption
1PA
max
peak (i.e., l2mPaAx <2l
for each studied compound). This im-
plies that the most accessible two-photon states are higher
in energy than those of the lowest allowed one-photon state of
these compounds. A similar observation has been reported
for many other multi-branched systems.[5a–f,i–k,6a–c,7d,8b,9c,g,10a–f]
Besides, the widely dispersed two-photon activities in the
near-IR spectral regime suggests that these model chromo-
phores could be potential candidate as broadband optical
power limiters when used against ultra-short laser pulses.
3) Compared with compound 1, the larger overall 2PA ac-
companied by an approximately 50% increased 2PA cross-
Effective optical power-limiting and stabilization performan-
ces in nanosecond regime: It is well known that an ideal op-
tical limiter is expected to show an intensity-dependent
transmission feature so that it can act like a transparent
medium when the incident intensity of light stays low and
once the input intensity rises up, the medium starts to regu-
late the transmitted output intensity to be always below a
certain maximum value before any optical saturation or
damage occurs. This feature makes optical limiters useful
for protecting human eyes and sensors against hazardous
sources of light. Additionally, this power-limiting phenomen-
on is also important for optical dynamic range compression
and noise suppression in signal processing as well as non-
section (i.e., dm2 ax(2)/d2
ACHTUNGTRENNUNG
may indicate that expanding the size of the p-conjugation
domain accomplished by elongating the p length of the het-
erocyclic ring complexes (i.e., from the quinoxaline units in
compound 1 to the indenoquinoxaline units in compound 2)
could be an effective approach toward enhanced molecular
nonlinear absorptivities in this molecular system. On the
other hand, the replacement of a carbon atom by a nitrogen
atom in the original quinoxaline moiety to form the pyrido-
pyrazine unit (as in the case of compound 3) seems to pro-
vide an efficient access to shift the molecular 2PA band
toward a longer wavelengths region without major diminish-
ing of the 2PA magnitude. These features are particularly
useful for the molecular design when either large 2PA at a
specific spectral range or a red-shifted 2PA band with a
fixed cross-section level is required for various applications.
4) From the molecular structures of model chromophores
1–3, it can be reasonably assumed that the p framework of
each compound may permit unsymmetrical charge transfer/
charge redistribution between the molecular termini and the
central part of the molecule under the excitation of light be-
cause all these p systems connect different electron-donating
units (at peripheral and central positions) with uneven elec-
tron-pushing strengths by various electron-deficient quinox-
alinoid rings within one molecule. Although at current stage
there is no clear understanding about how the structural ar-
AHCTUNGTRENNUNG
ty-dependent 2PA-induced excited-state absorption plays an
essential role for the observed large 2PA in various organic
systems under irradiation of nanosecond laser pulses,[20] and
the term “effective 2PA” is consequently used to describe
the apparent 2PA parameter measured in the nanosecond
time domain.[9b,20b] From the viewpoint of application, any
medium that exhibits strong apparent nonlinear absorption
by covering a wide spectral range could be very useful opti-
cal power attenuators against the laser pulses working in the
nanosecond time regime.[21]
In order to study the effective power-limiting performance
based on these model compounds, we have utilized nano-
AHCTUNGTREGsNNUN econd laser pulses for this investigation. As an example, we
select chromophore 2 as a representative for the demonstra-
tion because this model compound possesses a very strong
2PA around l=800 nm and is theoretically expected to
show a good power-limiting property at this wavelength. In
our experiment, the nonlinear absorbing medium was a sol-
ution of the studied dye in toluene with a path length of
1 cm and a concentration of 0.02m. A tunable nanosecond
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Two-Photon Absorption of Small Dendritic Chromophores
FULL PAPER
laser system (an integrated Q-switched Nd/YAG laser and
OPO/NT 342/3 from Ekspla) was employed as an excitation
laser light source to provide approximately 6 ns laser pulses
with a controlled average pulse energy in the range of ap-
proximately 0.02 to about 2 mJ and a repetition rate of
10 Hz for this study. The laser beam was slightly focused
onto the center of the sample solution in order to obtain a
nearly uniform laser beam radius within the whole cell and
the transmitted laser beam from the sample cell was detect-
ed by an optical power (energy) meter with a large detec-
tion area with a diameter of approximately 25 mm. Figure 6
Figure 7. a) Measured instantaneous pulse energy fluctuation of the input
laser pulses and b) measured instantaneous pulse energy fluctuation of
the output laser pulses. The repetition rate of the laser pulses was 10 Hz
and the average input pulse energy level was approximately 0.7 mJ.
Figure 6. Measured optical power attenuation curve based on the sample
solution of compound 2 under the excitation of a nanosecond laser pulses
at lꢀ800 nm.
pulse energy is observed for the output signal as illustrated
in Figure 7b.
Conclusion
illustrates the measured power-attenuation performance at l
ꢀ800 nm based on this chromophore solution. One can see
that compound 2 displays the superior power restriction
property at l=800 nm and this initial finding suggests the
potentiality of using this model fluorophore for broadband
power-suppressing-related applications in the nanosecond
regime.
We have characterized the degenerate two-photon-absorp-
tion-related properties both in the femtosecond and nano-
second regime of a newly synthesized multi-polar model
chromophore set with dendritic molecular structures based
on multi-substituted quinoxalinoid heterocyclic skeletons by
using two-photon-excited fluorescence and nonlinear trans-
mission techniques as probing tools. It is demonstrated that
chromophores with a branched skeleton based on the struc-
tural motif of a multi-substituted quinoxalinoid ring complex
can possess strong molecular 2PA in a specific spectral
region. In the present work it is also observed that model
compound 2 exhibits both an intense upconverted emission
when excited by a two-photon process and an effective opti-
cal power limiting/power stabilization against nanosecond
laser pulses. These observations may suggest that the qui-
On the other hand, the output/input curve shown in
Figure 6 represents a characteristic type of optical control,
which is ideal for the use in optical power (or intensity) sta-
bilization. The principle of this type of optical stabilization
is based on the fact that a huge magnitude change of the
input signal will lead to only a small variation of output
level.[22] This means that a larger input power (or intensity)
fluctuation will lead to a much smaller output fluctuation by
passing through a nonlinear absorptive medium such as the
solution of model chromophore 2. The experimental results
for the optical stabilization study based on the same sample
solution are shown in Figure 7. The curves in Figures 7a and
b are the instantaneous pulse energy changes of the input
and output laser pulses at l=800 nm. For the purpose of
comparison, the average levels for both the input and the
output signals were normalized to the same value. One can
see that the input pulses possess a relatively larger energy
fluctuation as shown in Figure 7a and after passing through
the solution of compound 2, a reduced fluctuation of the
AHCTUNGTREGnNNNU oxalinoid ring complexes utilized in this work could be
useful structural units for the construction of highly active
2PA chromophores for potential applications.
Experimental Section
General: All commercially available reagents for the preparation of the
intermediates and targeted chromophores were purchased from Aldrich
Chemical Co. or Alfa Aesar and were used as received, unless stated oth-
Chem. Eur. J. 2013, 19, 749 – 760
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
755

T.-C. Lin, J.-H. Lin et al.
erwise. 1H and 13C NMR spectra were recorded on a 300 MHz spectrom-
eter and referenced to TMS or residual CHCl3. The representative num-
bering of the carbon and hydrogen atoms of each intermediate and the
model chromophores for the NMR signal assignment are systematized
and illustrated in the Supporting Information. High-resolution mass spec-
trometry (HRMS) was conducted by using a Waters LCT ESI-TOF mass
spectrometer. MALDI-TOF MS spectra were obtained on a Voyager
DE-PRO mass spectrometer (Applied Biosystem, Houston, USA).
tracted with diethyl ether (40 mL) and the collected organic layer was
dried over MgSO4. After removing the solvent, the crude product was
obtained as dark brown solid. 2) NH2NH2·H2O (1.18 g, 20.3 mmol) was
added to a solution of the crude product from the first step in methanol
(80 mL). The resulting solution was stirred and heated to reflux for 6 h.
After cooling to room temperature, the reaction mixture was extracted
with ethyl acetate (3ꢁ30 mL) and the organic layer was dried over
MgSO4. After removing the solvent, the crude product was purified by
column chromatography on silica gel by using dichloromethane/hexane
(1:10) as eluent to give the final product as brown powder (4.53 g, ca.
52%). 1H NMR (300 MHz, CDCl3): d=7.42–7.36 (m, 4H; HB, HE, HD,
HG), 6.61–6.58 (m, 4H; HK, HI), 3.68 (s, 2H; NH2), 1.88–1.83 (m, 4H;
Hf), 1.04–1.03 (m, 12H; Hc, Hd, He), 0.76 (t, J=7.2 Hz, 6H; Ha),
0.60 ppm (s, 4H; Hb). 13C NMR (75 MHz, CDCl3): d=152.36 (CA),
152.14 (CL), 146.45 (CJ), 140.71 (CF), 131.27 (CG), 129.73 (CE), 125.84
(CH), 120.69 (CD), 119.70 (CB), 119.08 (CC), 114.10 (CK), 109.59 (CI),
55.15 (Cg’), 40.63 (Cf’), 31.59 (Ce’), 29.79 (Cd’), 23.73 (Cc’), 22.70 (Cb’),
14.11 ppm (Ca’); HRMS-FAB: m/z calcd for C25H34BrN: 428.4482
[M+H]+; found: 428.4361.
Photophysical methods: All linear optical properties of the subject model
compound were measured by corresponding spectrometers and the de-
tailed experimental conditions as well as the optical set-ups for the non-
linear optical property investigations are described in the Supporting In-
formation.
Synthesis: In Scheme 1, compounds 4 and 5 are shown to be the major
starting materials for the synthesis of the backbones of each intermedi-
ates and the model chromophores. These two compounds were obtained
in yields of approximately 80% for compound 4 and about 50% for com-
pound 5 by following established procedures.[9a] For the synthesis of other
key intermediates (compounds 6–22) and the targeted model compounds
(compounds 1–3), a series of functionalization steps starting from com-
pounds 4 and 5 has been conducted and is presented as the following:
N-(7-Bromo-9,9-dihexyl-9H-fluoren-2-yl)acetamide (9): Triethylamine
(1.2 g, 11.8 mmol), and acetic anhydride (1.2 g, 11.8 mmol) were added to
a solution of compound 8 (4.1 g, 9.8 mmol) in CH2Cl2 (30 mL). The re-
sulting mixture was stirred at room temperature for 4 h. The reaction
mixture was then extracted with ethyl acetate (3ꢁ30 mL) and the organic
layer was dried over MgSO4. After removing the solvent, the crude prod-
uct was purified by column chromatography on silica gel by using ethyl
acetate/hexane (1:5) as the eluent to give the final product as white
powder (4.05 g, ca. 92%). 1H NMR (300 MHz, CDCl3): d=8.02 (s, 1H;
NH), 7.63 (s, 1H; H2), 7.56 (d, J=8.1 Hz, 1H; H5), 7.45–7.40 (m, 4H; H4,
H8, H11, H9), 2.21 (s, 3H; H14), 1.93–1.88 (m, 4H; Hf), 1.03–1.01 (m, 12H;
Hc, Hd, He), 0.75 (t, J=7.2 Hz, 6H; Ha), 0.59 ppm (s, 4H; Hb); 13C NMR
(75 MHz, CDCl3): d=168.59 (sp2 carbon atom of the Ac group), 152.87
(CA), 151.50 (CL), 139.76 (CJ), 137.80 (CF), 136.23 (CG), 129.93 (CE),
126.06 (CH), 120.63 (CD), 120.54 (CB), 120.12 (CC), 118.65 (CI), 114.36
(CK), 55.53 (Cg’), 40.34 (Cf’), 31.51 (Ce’), 29.66 (Cd’), 24.69 (sp3 carbon
atom of the Ac group), 23.72 (Cc’), 22.59 (Cb’), 14.00 ppm (Ca’); HRMS-
FAB : m/z calcd for C27H35BrNO: 470.4848 [M+H]+; found: 470.2022.
7,7’-(Ethyne-1,2-diyl)bis(9,9-dihexyl-N,N-diphenyl-9H-fluoren-2-amine)
(6): 1,4-Bis(diphenylphosphino) butane (0.58 g, 1.37 mmol), and [PdCl2-
ACHTUNGTRENNUNG(PPh3)2] (0.05 g, 0.07 mmol) were added to a mixture of compound 5 (8 g,
0.013 mol) and acetylenedicarboxylic acid (0.76 g, 6.66 mmol) in DMSO
(15 mL). The resulting mixture was stirred at 1108C under an Ar atmo-
ACHTUNGTRENNUNGsphere for 8 h. After cooling the reaction mixture to the room tempera-
ture, methanol (ca. 5 mL) and cold hexane (ca. 5 mL) were added, the
solution was then stirred at 08C. After filtration, the crude solid product
was collected and recrystallized from methanol. The purified product was
obtained as yellow powder (6.04 g, ca. 85%). 1H NMR (300 MHz,
CDCl3): d=7.61 (d, J=8.1 Hz, 2H; H15), 7.59–7.51 (m, 6H; H12, H9, H14),
7.28 (t, J=7.2 Hz, 8H; H2), 7.16–7.13 (m, 10H; H10, H3), 7.07–7.04 (m,
6H; H6, H1), 1.95–1.86 (m, 8H; Hf), 1.15–1.10 (m, 24H; Hc, Hd, He),
0.88–0.85 (t, J=7.2 Hz, 12H; Ha), 0.62 ppm (s, 8H; Hb); 13C NMR
(75 MHz, CDCl3): d=152.43 (C16), 150.63 (C5), 147.86 (C4), 147.49 (C7),
141.10 (C11), 135.51 (C10), 130.60 (C15), 129.16 (C2), 125.69 (C9), 123.88
(C3), 123.40 (C12), 122.59 (C1), 120.64 (C6), 120.56 (C8), 119.01 (C13, C14),
99.49 (ethynyl carbon), 55.08 (Cg), 40.28 (Cf), 31.54 (Ce), 29.63 (Cd), 23.73
(Cc), 22.57 (Cb), 14.04 ppm (Ca); HRMS-FAB: m/z calcd for C76H84N2:
1024.6635 [M]+; found: 1024.6639.
N-(7-Bromo-9,9-dihexyl-3-nitro-9H-fluoren-2-yl)acetamide (10): HNO3
(4 g, 63.6 mmol) was added dropwise to a solution of compound 9 (3 g,
6.36 mmol) in acetone (10 mL) and acetic acid (30 mL). The resulting
mixture was stirred at 58C for 10 min. The reaction mixture was then ex-
tracted with ethyl acetate (3ꢁ30 mL) and the organic layer was dried
over MgSO4. After removing the solvent, the crude product was purified
by column chromatography on silica gel by using ethyl acetate/hexane
(1:10) as the eluent to give the final product as yellow powder (2.6 g, ca.
78%). 1H NMR (300 MHz, CDCl3): d=10.61 (s, 1H; NH), 8.81 (s, 1H;
H8), 8.47 (s, 1H; H11), 7.58 (d, J=8.1 Hz, 1H; H4), 7.51–7.48 (m, 2H; H5,
H2), 2.33 (s, 3H; H14), 2.02–1.94 (m, 4H; Hf), 1.05–1.04 (m, 12H; Hc, Hd,
He), 0.77 (t, J=7.2 Hz, 6H; Ha), 0.58–0.56 ppm (m, 4H; Hb); 13C NMR
(75 MHz, CDCl3): d=169.06 (sp2 carbon atom of the Ac group), 159.41
(CL), 152.77 (CA), 137.55 (CI), 135.79 (CJ), 135.66 (CF), 134.71 (CG),
130.62 (CE), 126.42 (CH), 122.41 (CD), 121.40 (CB), 116.63 (CC), 116.18
(CK), 55.56 (Cg’), 40.17 (Cf’), 31.41 (Ce’), 29.48 (Cd’), 25.83 (sp3 carbon
atom of the Ac group), 23.77 (Cc’), 22.52 (Cb’), 13.95 ppm (Ca’); HRMS-
FAB : m/z calcd for C27H35BrN2O3: 516.4824 [M+H]+; found: 516.1794.
1,2-Bis(7-(diphenylamino)-9,9-dihexyl-9H-fluoren-2-yl)ethane-1,2-dione
(7): KMnO4 (3.08 g, 0.195 mmol), NaHCO3 (0.41 g, 4.88 mmol), Ali-
quat 336 (0.045 g, 0.22 mmol), and H2O (20 mL) were added to a solution
of compound 6 (5 g, 4.88 mmol) in CH2Cl2 (25 mL). The resulting mix-
ture was stirred at room temperature for 12 h. Then, saturated aqueous
solution of NaHSO3 (50 mL) and HCl (1n, 20 mL) were added. The solu-
tion was then extracted with dichloromethane (50 mL) and the collected
organic layer was dried over MgSO4. After removing the solvent, the
crude product was purified by column chromatography on silica gel by
using dichloromethane/hexane (1:4) to give the final product as saffron-
yellow powder (3.64 g, ca. 71%). 1H NMR (300 MHz, CDCl3): d=8.03
(d, J=1.2 Hz, 2H; H12), 7.86 (dd, J1 =8.1 Hz, J2 =1.2 Hz, 2H; H15), 7.64
(d, J=8.1 Hz, 2H; H14), 7.63 (d, J=8.1 Hz, 2H; H9), 7.30–7.25 (m, 8H;
H2), 7.12–7.10 (m, 10H; H10, H3), 7.05–7.01 (m, 6H; H6, H1), 2.01–1.78
(m, 8H; Hf), 1.11–1.05 (m, 24H; Hc, Hd, He), 0.86–0.83 (m, 12H; Ha),
0.77 ppm (s, 8H; Hb); 13C NMR (75 MHz, CDCl3): d=195.19 (C17),
153.89 (C11), 151.34 (C7), 149.08 (C16), 147.83 (C5), 147.62 (C4), 133.85
(C13), 131.01 (C8), 130.99 (C9), 129.32 (C2), 124.48 (C3), 123.21 (C1),
122.77 (C15, C12), 121.86 (C14), 118.89 (C6), 118.11 (C10), 55.33 (Cg), 39.96
(Cf), 31.49 (Ce), 29.54 (Cd), 23.79 (Cc), 22.55 (Cb), 14.04 ppm (Ca);
HRMS-FAB: m/z calcd for C76H84N2O2: 1056.6533 [M]+; found:
1056.6627.
7-Bromo-9,9-dihexyl-3-nitro-9H-fluoren-2-amine (11): Sulfuric acid
(60%, 3.5 mL) was added to
a solution of compound 10 (2.5 g,
4.85 mmol) in methanol (25 mL) and the resulting mixture was stirred at
808C for 10 h. The reaction mixture was then extracted with ethyl acetate
(3ꢁ30 mL) and the organic layer was dried over MgSO4. After removing
the solvent, the crude product was purified by column chromatography
on silica gel by using ethyl acetate/hexane (1:8) as the eluent to give the
final product as yellow powder (2.14 g, ca. 93%). 1H NMR (300 MHz,
CDCl3): d=8.38 (s, 1H; HH), 7.50 (d, J=7.8 Hz, 1H; HE), 7.46 (dd, J1 =
7.8 Hz, J2 =1.5 Hz, 1H; HD), 7.39 (d, J=1.5 Hz, 1H; HB), 6.72 (s, 1H;
HK), 6.27 (s, 2H; NH2), 1.92–1.85 (m, 4H; Hf’), 1.07–1.05 (m, 12H; Hc’,
Hd’, He’), 0.78 (t, J=7.2 Hz, 6H; Ha’), 0.63–0.59 ppm (m, 4H; Hb’);
13C NMR (75 MHz, CDCl3): d=159.48 (CL), 151.33 (CA), 145.28 (CJ),
7-Bromo-9,9-dihexyl-9H-fluoren-2-amine (8): Two-step reaction: 1) Po-
tassium phthalACHTUNGTRENNUNGimide (3.76 g, 20.3 mmol) and CuI (3.76 g, 20.3 mmol)
were added to a solution of compound 4 (10 g, 20.3 mmol) in DMAc
(160 mL). The resulting solution was stirred and heated to reflux for
24 h. After cooling to room temperature, the reaction mixture was ex-
756
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ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 749 – 760

Two-Photon Absorption of Small Dendritic Chromophores
FULL PAPER
138.17 (CI), 131.29 (CF), 130.47 (CG), 130.23 (CE), 125.87 (CH), 120.86
(CD), 120.52 (CB), 116.42 (CC), 112.40 (CK), 55.44 (Cg’), 40.61 (Cf’), 31.26
(Ce’), 29.39 (Cd’), 23.59 (Cc’), 22.37 (Cb’), 13.78ppm (Ca’); HRMS-FAB:
m/z calcd for C25H33BrN2O2: 474.4457 [M+H]+; found: 474.1730.
silica gel by using ethyl acetate/hexane (1:3) as the eluent to give the
final product as yellow powder (1.15 g, ca. 97%). 1H NMR (300 MHz,
CDCl3): d=7.98 (d, J=8.7 Hz, 1H; HC), 7.51–7.49 (m, 8H; H9, H12, H13,
H15), 7.45 (d, J=8.4 Hz, 1H; HB), 7.27–7.19 (m, 8H; H2), 7.17 (d, J=
2.7 Hz, 1H; HF), 7.12–7.06 (m, 10H; H3, H6), 7.02–6.98 (m, 6H; H1, H8),
1.74–1.69 (m, 8H; Hf), 1.12–1.02 (m, 24H; Hc, Hd, He), 0.78 (t, J=7.2 Hz,
12H; Ha), 0.63 ppm (s, 8H; Hb); 13C NMR (75 MHz, CDCl3, tentative as-
signments based on calculates values): d=153.71 (CG), 152.62 (CH),
152.55 (C5), 150.47 (C16), 120.21 (C4), 147.94 (C11), 142.91 (CD), 141.27
(C7), 140.91 (CE), 137.82 (C10), 136.15 (CA), 135.73 (C14), 130.08 (CC),
129.09 (C2), 129.89 (C15), 124.25 (C12), 123.76 (C3), 123.39 (C9), 122.34
(C1), 122.71 (CF), 120.79 (C13), 119.18 (C6), 118.82 (C8), 107.85 (CB), 55.03
(Cg), 40.08 (Cf), 31.53 (Ce), 29.58 (Cd), 23.82 (Cc), 22.60 (Cb), 14.07 ppm
(Ca); HRMS-FAB: m/z calcd for C82H89N5: 1143.7118 [M]+; found:
1143.7111.
7-Bromo-9,9-dihexyl-9H-fluorene-2,3-diamine (12): SnCl2·2H2O (9.5 g,
42.2 mmol) was added to a solution of compound 10 (2 g, 4.2 mmol) in
ethyl acetate (40 mL) and stirred at 808C for 5 h. After cooling to room
temperature, a saturated aqueous solution of NaHCO3 (ca. 50 mL) was
added to the reaction mixture. The solution was then extracted with ethyl
acetate (3ꢁ30 mL) and the organic layer was dried over MgSO4. After
removing the solvent, the crude product was purified by column chroma-
tography on silica gel by using ethyl acetate/hexane (1:3) as the eluent to
give the final product as yellow powder (1.33 g, ca. 71%). 1H NMR
(300 MHz, CDCl3): d=7.37 (d, J=1.5 Hz, 1H; HB), 7.33 (dd, J1 =7.8 Hz,
J2 =1.5 Hz, 1H; HD), 7.26 (d, J=7.8 Hz, 1H; HE), 6.92 (s, 1H; HK), 6.60
(s, 1H; HH), 3.44 (s, 4H; NH2), 1.85–1.80 (m, 4H; Hf’), 1.03–1.01 (m,
12H; Hc’, Hd’, He’), 0.75 (t, J=7.2 Hz, 6H; Ha’), 0.64–0.62 ppm (m, 4H;
Hb’); 13C NMR (75 MHz, CDCl3): d=152.59 (CA), 142.93 (CL), 140.62
(CF), 135.19 (CJ), 133.41 (CI), 132.02 (CE), 129.37 (CD), 125.50 (CB),
119.39 (CG), 118.82 (CC), 110.61 (CH), 108.08 (CK), 54.52 (Cg’), 40.32 (Cf’),
31.34 (Ce’), 29.55 (Cd’), 23.52 (Cc’), 22.44 (Cb’), 13.85 ppm (Ca’).
7,7’-[6-({2,3-Bis[7-(diphenylamino)-9,9-dihexyl-9H-fluoren-2-yl]quinoxa-
lin-6-yl}amino)quinoxaline-2,3-diyl]bis(9,9-dihexyl-N,N-diphenyl-9H-flu-
oren-2-amine) (16): [Pd
(0.05 g, 0.54 mmol), and PAHCTNUGTRENNNUG
(dba)3] (2 mg, 0.002 mmol), sodium tert-butoxide
(tBu)3 (0.9 mg, 0.0045 mmol) were added to a
mixture of compounds 15 (0.51 g, 0.45 mmol), and 13 (0.54 g, 0.45 mmol)
in dry toluene (8 mL). The resulting mixture was stirred at 908C under
an Ar atmosphere for 12 h. After cooling to room temperature, H2O (ca.
100 mL) was added to the reaction mixture. The solution was then ex-
tracted with ethyl acetate (3ꢁ30 mL) and the organic layer was dried
over MgSO4. After removing the solvent, the crude product was purified
through column chromatography on silica gel by using THF/hexane
(1:10) as the eluent to give the final product as gray power (0.7 g, ca.
7,7’-(6-Bromoquinoxaline-2,3-diyl)bis(9,9-dihexyl-N,N-diphenyl-9H-fluo-
ren-2-amine) (13): A mixture of compound 7 (2 g, 1.9 mmol) and 4-bro-
mobenzene-1,2-diamine (0.39 g, 2.1 mmol) in CH3COOH (30 mL) was
heated to reflux under a N2 atmosphere for 6 h. After cooling to room
temperature, H2O (ca. 50 mL) was added to the reaction mixture. After
filtration, the crude solid product was collected and recrystallized from
methanol. The purified product was obtained as green-brownish powder
(2.3 g, 96.6%). 1H NMR (300 MHz, CDCl3): d=8.41 (d, J=2.1 Hz, 1H;
HF), 8.12 (d, J=8.7 Hz, 1H; HC), 7.82 (dd, J1 =8.7 Hz, J2 =2.1 Hz, 1H;
HB), 7.56–7.45 (m, 8H; H9, H12, H13, H15), 7.25–7.20 (m, 8H; H2), 7.10–
7.05 (m, 10H; H3, H6), 7.02–6.96 (m, 6H; H1, H8), 1.71–1.68 (m, 8H; Hf),
1.01–0.99 (m, 24H; Hc, Hd, He), 0.76 (t, J=7.2 Hz, 12H; Ha), 0.61 ppm (s,
8H; Hb). 13C NMR (75 MHz, CDCl3, tentative assignments based on cal-
culates values): d=154.78 (CG), 154.30 (CH), 152.63 (C5), 150.62 (C16),
147.89 (C4), 147.57 (C11), 141.95 (C7), 141.88 (CD), 141.66 (CE), 139.82
(C10), 136.95 (CF), 136.85 (CC), 135.33 (C15), 133.04 (C9), 131.36 (C12),
130.39 (CA), 129.15 (C3), 124.33 (C13), 123.90 (C2), 123.34 (C14), 122.59
(C1), 120.89 (C6), 119.02 (CB), 118.89 (C8), 55.09 (Cg), 40.09 (Cf), 31.53
(Ce), 29.57 (Cd), 23.83 (Cc), 22.60 (Cb), 14.07 ppm (Ca); HRMS-FAB: m/z
calcd for C82H87BrN4: 1206.6114 [M]+; found: 1206.6104.
1
68%). H NMR (300 MHz, CDCl3): d=8.16 (d, J=8.7 Hz, 2H; HC), 8.03
(s, 2H; HF), 7.63 (d, J=9 Hz, 2H; H22), 7.55–7.50 (m, 16H; H9, H12, H13,
H15), 7.26–7.22 (m, 16H; H2), 7.12–7.09 (m, 20H; H3, H6), 7.03–6.98 (m,
12H; H1, H8), 6.58 (s, 1H; NH), 1.71–1.68 (m, 16H; Hf), 1.11–1.02 (m,
48H; Hc, Hd, He), 0.73 (t, J=7.2 Hz, 24H; Ha), 0.64 ppm (s, 8H; Hb);
13C NMR (75 MHz, CDCl3, tentative assignments based on calculates
values): d=154.39 (CG), 152.59 (CH), 151.73 (C5), 150.56 (C16), 147.91
(C4), 147.33 (C11), 142.93 (CD), 142.50 (C10), 141.66 (CC), 141.29 (C9),
137.75 (CA), 136.45 (CD), 137.33 (C7), 135.54 (C15), 130.36 (C12), 129.12
(C2), 124.43 (C13), 123.82 (C3), 123.38 (C14), 122.49 (C1), 120.80 (C6),
119.13 (C8), 118.91 (CF), 112.11 (CB), 55.06 (Cg), 40.09 (Cf), 31.53 (Ce),
29.57 (Cd), 23.83 (Cc), 22.60 (Cb), 14.07 ppm (Ca); HRMS-FAB: m/z calcd
for C82H87BrN4: 2271.3970 [M]+; found: 2271.4028.
7,7’-(8-Bromo-10,10-dihexyl-10H-indeno
ACHTUNGTRENNUNG
bis(9,9-dihexyl-N,N-diphenyl-9H-fluoren-2-amine) (17):
A
7,7’-(6-Nitroquinoxaline-2,3-diyl)bis(9,9-dihexyl-N,N-diphenyl-9H-fluo-
ren-2-amine) (14): A mixture of compound 7 (2 g, 1.9 mmol) and 4-nitro-
benzene-1,2-diamine (0.29 g, 2.1 mmol) in CH3COOH (30 mL) was
heated to reflux under a N2 atmosphere for 6 h. After cooling to room
temperature, H2O (ca. 50 mL) was added to the reaction mixture. After
filtration, the crude solid product was collected and recrystallized from
methanol. The purified product was obtained as green-brownish powder
(2.01 g, ca. 90%). 1H NMR (300 MHz, CDCl3): d=9.09 (s, 1H; HF), 8.51
(dd, J1 =8.7 Hz, J2 =2.1 Hz, 1H; HB), 8.30 (d, J=8.7 Hz, 1H; HC), 7.65–
7.52 (m, 8H; H9, H12, H13, H15), 7.28–7.22 (m, 8H; H2), 7.13–7.09 (m,
10H; H3, H6), 7.04–6.99 (m, 6H; H1, H8), 1.79–1.74 (m, 8H; Hf), 1.11–
0.95 (m, 24H; Hc, Hd, He), 0.79 (t, J=7.2 Hz, 12H; Ha), 0.64–0.63 ppm
(m, 8H; Hb); 13C NMR (75 MHz, CDCl3, tentative assignments based on
calculates values): d=156.80 (CG), 156.20 (CH), 152.68 (C5), 150.69 (C16),
147.80 (C4), 147.54 (C11), 143.52 (C7), 142.71 (CD), 142.51 (CE), 139.79
(C10), 136.16 (CF), 134.95 (CC), 130.48 (C15), 129.17 (C9), 125.48 (C12),
124.37 (CA), 123.98 (C3), 123.22 (C13), 122.89 (C2), 122.24 (C14), 121.02
(C1), 119.03 (C6), 118.95 (CB), 118.82 (C8), 55.12 (Cg), 40.09 (Cf), 31.53
(Ce), 29.57 (Cd), 23.83 (Cc), 22.60 (Cb), 14.07 ppm (Ca).
compound 7 (2 g, 1.9 mmol) and compound 12 (0.93 g, 2.1 mmol) in
CH3COOH (30 mL) was heated to reflux under a N2 atmosphere for
12 h. After cooling to room temperature, the reaction mixture was ex-
tracted with ethyl acetate (3ꢁ30 mL) and the organic layer was dried
over MgSO4. After removing the solvent, the crude product was purified
by column chromatography on silica gel by using THF/hexane (1:15) as
the eluent to give the final product as yellow powder (2.44 g, ca. 88%).
1H NMR (300 MHz, CDCl3): d=8.44 (s, 1H; HH), 8.10 (s, 1H; HK), 7.93
(dd, J1 =3 Hz, J2 =1.8 Hz, 1H; HD), 7.60–7.52 (m, 8H; H9, H12, H13, H15),
7.43–7.42 (m, 2H; HE, HB), 7.27–7.22 (m, 8H; H2), 7.13–7.08 (m, 10H;
H3, H6), 7.03–6.98 (m, 6H; H1, H8), 2.13–2.10 (m, 4H; Hf), 1.71–1.68 (m,
8H; Hf’), 1.10–1.04 (m, 36H; Hc, Hc’, Hd, Hd’, He, He’), 0.81–0.66 ppm (m,
30H; Ha, Ha’, Hb, Hb’); 13C NMR (75 MHz, CDCl3, tentative assignments
based on calculates values): d=153.58 (C16), 153.16 (CN), 152.94 (CM),
152.67 (C5), 150.67 (CA), 150.59 (CL), 147.98 (C4), 147.51 (CF), 142.90
(CJ), 141.65 (CI), 141.38 (CG), 141.29 (C11), 138.78 (C7), 137.56 (C14),
137.49 (C14'), 135.60 (C10), 130.70 (CB), 129.42(CE), 129.37(C2),
129.22(C12), 126.55 (C25), 124.51 (C15), 124.55 (C3), 123.93 (CK), 123.46
(CC), 122.61 (C1), 122.47 (C13), 120.92 (C6), 119.16 (C9), 119.06 (C8),
118.54 (CH), 55.22 (Cg), 55.10 (Cg'), 41.44 (Cf), 40.16 (Cf'), 31.60 (Ce, Ce'),
29.77 (Cd), 29.65 (Cd'), 23.89 (Cc, Cc'), 22.68 (Cb), 22.61 (Cb'), 14.14 (Ca),
14.01 ppm (Ca'); MALDI-TOF: m/z calcd for C101H115BrN4: 1463.8305
[M+H]+; found: 1463.8384.
7,7’-(6-Aminoquinoxaline-2,3-diyl)bis(9,9-dihexyl-N,N-diphenyl-9H-fluo-
ren-2-amine) (15): SnCl2·2H2O (2.3 g, 10.2 mmol) was added to a solution
of compound 14 (1.2 g, 1.02 mmol) in ethyl acetate (20 mL). The result-
ing mixture stirred at 808C for 5 h. After cooling to room temperature, a
saturated aqueous solution of NaHCO3 (ca. 30 mL) was added to the re-
action mixture. The solution was then extracted with ethyl acetate (3ꢁ
30 mL) and the organic layer was dried over MgSO4. After removing the
solvent, the crude product was purified by column chromatography on
7,7’-(8-Amino-10,10-dihexyl-10H-indenoACHTNUGTRNEUNG[1,2-g]quinoxaline-2,3-diyl)-
bis(9,9-dihexyl-N,N-diphenyl-9H-fluoren-2-amine) (18): Two-step reac-
tion: 1) Potassium phthalimide (0.25 g, 1.37 mmol) and CuI (0.26 g,
Chem. Eur. J. 2013, 19, 749 – 760
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
757

T.-C. Lin, J.-H. Lin et al.
1.37 mmol) were added to a solution of compound 17 (2 g, 1.37 mmol) in
DMAc (20 mL). The resulting solution was stirred and heated to reflux
for 24 h. After cooling to room temperature, the reaction mixture was ex-
tracted with ethyl ether (50 mL) and the collected organic layer was
dried over MgSO4. After removing the solvent, the crude product was
obtained as dark brown solid. 2) NH2NH2·H2O (0.08 g, 1.37 mmol) was
added to a solution of the crude product from the first step in methanol
(60 mL). The resulting solution was stirred and heated to reflux for 6 h.
After cooling to room temperature, the reaction mixture was extracted
with ethyl acetate (3ꢁ30 mL), and the organic layer was dried over
MgSO4. After removing the solvent, the crude product was purified by
column chromatography on silica gel by using THF/hexane (1:6) as the
eluent to give the final product as brown powder (1.2 g, ca. 62%).
1H NMR (300 MHz, CDCl3): d=8.27 (s, 1H; HH), 8.04 (s, 1H; HK), 7.74
(d, J=7.8 Hz, 1H; HE), 7.60–7.54 (m, 8H; H9, H12, H13, H15), 7.31–7.25
(m, 8H; H2), 7.17–7.12 (m, 10H; H3, H6), 7.07–7.02 (m, 6H; H1, H8),
6.79–6.73 (m, 2H; HD, HB), 3.97 (s, 2H; NH2), 2.15–2.11 (m, 4H; Hf),
1.79–1.76 (m, 8H; Hf’), 1.14–1.03 (m, 36H; Hc, Hc’, Hd, Hd’, He, He’), 0.83–
0.71 ppm (m, 30H; Ha, Ha’, Hb, Hb’); 13C NMR (75 MHz, CDCl3, tentative
assignments based on calculates values): d=153.53 (C16), 153.41 (CN),
152.92 (CM), 152.55 (C5), 151.80 (C19), 150.48 (CA), 150.39 (CL), 147.88
(C4), 147.25 (C23), 144.73 (CC), 141.62 (CI), 141.20 (CG, C11), 140.58 (C7),
137.80 (C14), 137.72 (C14'), 135.65 (C10), 130.62 (C12), 129.09 (C2), 125.46
(CE), 124.36 (C15), 123.76 (C3), 123.37 (C13), 123.76 (CK), 122.44 (C1),
121.71 (C13), 120.74 (C6), 119.12 (C9), 118.92 (C8), 115.66 (CH), 114.55
(CD), 109.10 (CB), 54.99 (Cg), 54.83 (Cg'), 41.55 (Cf), 40.09 (Cf'), 31.52 (Ce,
Ce'), 29.77 (Cd), 29.57(Cd'), 23.82 (Cc, Cc'), 22.59 (Cb, Cb'), 14.06 (Ca),
13.96 ppm (Ca');.
0.65 ppm (s, 8H; Hb, Hb’); 13C NMR (75 MHz, CDCl3, tentative assign-
ments based on calculates values): d=157.20 (CG), 156.13 (CF), 154.57
(CC), 152.80 (C16), 152.70 (C16'), 150.83 (C5), 150.65 (C5'), 148.28 (CB),
147.88 (C4), 142.66 (CE), 142.55 (C11), 139.31 (C7), 136.31 (C14), 136.25
(C14'), 136.03 (CD), 135.19 (C10), 135.11 (C10'), 129.72 (C12), 129.22 (C2),
129.00 (C12'), 124.37 (C15), 124.36 (C15'), 124.01 (C3), 123.33 (C13), 122.72
(C1), 121.04 (C6), 120.44 (CA), 119.23 (C9), 118.90 (C8), 118.68 (C9'), 55.30
(Cg), 55.13 (Cg'), 40.23 (Cf), 40.11 (Cf'), 31.64 (Ce), 31.58 (Ce'), 29.61 (Cd,
Cd'), 23.91 (Cc), 23.83 (Cc'), 22.66 (Cb, Cb'), 14.13 ppm (Ca, Ca'); HRMS-
FAB : m/z calcd for C81H86BrN5: 1210.4870 [M]+; found: 1210.5282.
7,7’-(7-Aminopyrido
yl-9H-fluoren-2-amine) (21): Two-step reaction: 1) Potassium phthal-
AHCTUNGERTGiNNUN mide (0.15 g, 0.83 mmol) and CuI (0.16 g, 0.83 mmol) was added to a sol-
ACHTUNGTREN[NUNG 2,3-b]pyrazine-2,3-diyl)bis(9,9-dihexyl-N,N-diphen-
ution of compound 20 (1 g, 0.83 mmol) in DMAc (10 mL). The resulting
solution was stirred and heated to reflux for 24 h. After cooling to room
temperature, the reaction mixture was extracted with diethyl ether
(50 mL) and dried over MgSO4. After removing the solvent, the crude
product was obtained as dark brown solid. 2) NH2NH2·H2O (0.05 g,
0.83 mmol) was added to a solution of the crude product from the first
step in methanol (50 mL). The resulting solution was stirred and heated
to reflux for 6 h. After cooling to room temperature, the reaction mixture
was extracted with ethyl acetate (3ꢁ30 mL) and the organic layer was
dried over MgSO4. After removing the solvent, the crude product was
purified by column chromatography on silica gel by using THF/hexane
(1:4) as the eluent to give the final product as brown powder (0.49 g, ca.
1
53%). H NMR (300 MHz, CDCl3): d=8.74 (d, J=2.7 Hz, 1H; HB), 7.79
(s, 1H; HE), 7.71 (dd, J1 =7.8, J2 =0.9 Hz, 1H; H13), 7.63 (d, J=7.8 Hz,
1H; H12), 7.56 (q, J=2.7 Hz, 2H; H9, H9’), 7.50 (d, J=8.1 Hz, 1H; H12’),
7.51–7.48 (m, 3H; H13, H15, H15’), 7.29–7.24 (m, 8H; H2), 7.15–7.11 (m,
10H; H3, H6), 7.08–7.02 (m, 6H; H1, H8), 4.37 (s, 2H; NH2), 1.87–1.72
(m, 8H; Hf, Hf’), 1.08–1.04 (m, 24H; Hc, Hc’, Hd, Hd’, He, He’), 0.79 (t, J=
7.2 Hz, 12H; Ha, Ha’), 0.62 ppm (s, 8H; Hb, Hb’); 13C NMR (75 MHz,
CDCl3, tentative assignments based on calculates values): d=155.10
(CG), 152.55 (CC), 152.40 (CF), 150.59 (C16), 150.30 (C16'), 147.83 (C4),
147.42 (C5), 147.32 (C5'), 146.19 (CB), 144.16 (CA), 141.45 (CD), 141.72
(C11), 141.45 (C11'), 137.32 (C14), 137.13 (C14'), 136.80 (C7), 135.53 (C10),
135.35 (C10'), 129.42 (C12), 129.22 (C3), 128.80 (C12'), 124.34 (C15), 124.22
(C15'), 123.79 (C2), 123.31 (C13), 122.49 (C1), 120.79 (C6), 119.12 (C9),
118.99 (C8), 118.38 (C9'), 114.74 (CE), 55.13 (Cg), 54.94 (Cg'), 40.18 (Cf),
40.00 (Cf'), 31.54 (Ce), 31.48 (Ce'), 29.58 (Cd, Cd'), 23.81 (Cc), 23.83 (Cc'),
22.66 (Cb, Cb'), 14.13 ppm (Ca, Ca'); MALDI-TOF: m/z calcd for
C81H88N6: 1145.6056 [M]+; found: 1145.7183.
7,7’-[8-({2,3-Bis[7-(diphenylamino)-9,9-dihexyl-9H-fluoren-2-yl]-10,10-di-
hexyl-10H-indeno
indeno[1,2-g]quinoxaline-2,3-diyl]bis(9,9-dihexyl-N,N-diphenyl-9H-fluo-
ren-2-amine) (19): [Pd2A(dba)3] (2.3 mg, 0.0025 mmol), sodium tert-butox-
ide (0.06 g, 0.6 mmol), and P(tBu)3 (1.1 mg, 0.05 mmol) were added to a
ACHTUNGTRENNUNG[1,2-g]quinoxalin-8-yl}amino)-10,10-dihexyl-10H-
ACHTUNGTRENNUNG
CHTUNGTRENNUNG
AHCTUNGTRENNUNG
mixture of compounds 18 (0.7 g, 0.5 mmol), and 17 (0.73 g, 0.5 mmol) in
dry toluene (15 mL). The resulting mixture was stirred at 908C under an
Ar atmosphere for 12 h. After cooling to room temperature, H2O (ca.
100 mL) was added to the reaction mixture. The solution was extracted
with ethyl acetate (3ꢁ30 mL) and the organic layer was dried over
MgSO4. After removing the solvent, the crude product was purified
through column chromatography on silica gel by using THF/hexane
(1:10) as the eluent to give the final product as yellow powder (0.86 g,
62%). 1H NMR (300 MHz, CDCl3): d=8.32 (s, 1H; HH), 8.06 (s, 1H;
HK), 7.85 (d, J=8.1 Hz, HD), 7.64–7.51 (m, 8H; H9, H12, H13, H15), 7.27–
7.22 (m, 8H; H2), 7.13–7.09 (m, 12H; H3, H6, HB, HE), 7.03–6.99 (m, 6H;
H1, H8), 6.32 (s, 2H; NH), 2.17–2.15 (m, 4H; Hf), 1.75–1.69 (m, 8H; Hf’),
1.13–1.04 (m, 36H; Hc, Hc’, Hd, Hd’, He, He’), 0.79–0.65 ppm (m, 30H; Ha,
Ha’, Hb, Hb’); 13C NMR (75 MHz, CDCl3, tentative assignments based on
calculates values): d=153.51 (CN), 153.25 (C16), 152.64 (C5), 152.30 (CM),
150.62 (CA), 150.53 (CL), 147.97 (C4), 147.38 (CF), 144.20 (CC), 143.63
(CJ), 141.63(CG), 141.40 (CI,C7), 140.90 (C11), 137.76 (C14), 137.68 (C14'),
135.69 (C10), 133.22 (CE), 129.19 (C2), 128.98 (C12), 124.44 (C15), 123.87
(C3), 123.45 (CK), 122.55 (C1), 122.05 (C13), 120.86 (C6), 119.19 (C9),
119.04 (C8), 117.56 (CH), 116.57 (CD), 111.54 (CB), 55.10 (Cg, Cg'), 41.67
(Cf), 40.18 (Cf'), 31.74 (Ce), 31.62 (Ce'), 29.93 (Cd), 29.66 (Cd'), 24.12 (Cc,
Cc'), 22.69 (Cb), 22.61 (Cb'), 14.15 (Ca), 14.07 ppm (Ca'); MALDI-TOF:
m/z calcd for C202H231N9: 2782.8352 [M+H]+; found: 2783.8430.
7,7’-[6-({2,3-Bis[7-(diphenylamino)-9,9-dihexyl-9H-fluoren-2-yl]pyrido-
AHCTUNGTRENNUNG
CTHUNGTRENNUNG
sodium tert-butoxide (0.07 g, 0.68 mmol), Xantphos (5.2 mg, 0.009 mmol)
were added to a mixture of compounds 21 (0.65 g, 0.57 mmol) and 20
(0.82 g, 0.68 mmol) in dry toluene (15 mL). The resulting solution was
stirred at 908C under an Ar atmosphere for 12 h. After cooling to room
temperature, H2O (ca. 100 mL) was added to the reaction mixture. The
solution was extracted with ethyl acetate (3ꢁ30 mL) and the organic
layer was dried over MgSO4. After removing the solvent, the crude prod-
uct was purified through column chromatography on silica gel by using
THF/hexane (1:4) as the eluent to give the final product as orange
powder (0.92 g, 71.4%). 1H NMR (300 MHz, CDCl3): d=9.27 (s, 1H;
HB), 8.57 (d, J=2.7 Hz, 1H; HE), 7.81 (s, 1H; H15), 7.74 (d, J=8.4 Hz,
1H; H12), 7.63 (d, J=7.8 Hz, 1H; H12’), 7.59–7.44 (m, 5H; H13, H13’, H9,
H9’, H15’), 7.32–7.25 (m, 8H; H2), 7.18–7.11 (m, 10H; H3, H6), 7.07–7.02
(m, 7H; H1, H8, NH), 1.82–1.76 (m, 8H; Hf, Hf’), 1.06–1.04 (m, 24H; Hc,
Hc’, Hd, Hd’, He, He’), 0.81 (t, J=7.2 Hz, 12H; Ha, Ha’), 0.48 ppm (s, 8H;
Hb, Hb’); 13C NMR (75 MHz, CDCl3, tentative assignments based on cal-
culates values): d=155.77 (CG), 154.11 (CF), 152.59 (CC), 150.66 (C16),
150.48 (C16'), 148.43 (CB), 147.80 (C4), 147.51 (C5), 147.43 (C5'), 145.64
(CA), 142.05 (C11), 141.87 (C11'), 138.97 (C7), 136.81 (C10), 136.71 (C10'),
136.40 (CD), 135.34 (C14), 135.30 (C14'), 129.49 (C12), 129.09 (C3), 124.38
(C15), 124.23 (C15'), 123.81 (C2), 123.27 (C13), 122.50 (C1), 120.84 (C6),
119.23 (C9), 118.92 (C8), 118.57 (C9'), 117.82 (CE), 55.12 (Cg), 55.05 (Cg'),
40.11 (Cf), 40.01 (Cf'), 31.53 (Ce), 31.48 (Ce'), 29.52 (Cd, Cd'), 23.71 (Cc),
7,7’-(7-BromopyridoACHTUNGTRENNUNG[2,3-b]pyrazine-2,3-diyl)bis(9,9-dihexyl-N,N-diphen-
yl-9H-fluoren-2-amine) (20): A mixture of compound 7 (2 g, 1.9 mmol)
and 5-bromopyridine-2,3-diamine (0.29 g, 2.1 mmol) in CH3COOH
(30 mL) was heated to reflux under a N2 atmosphere for 6 h. After cool-
ing to room temperature, H2O (ca. 50 mL) was added to the reaction
mixture. After filtration, the crude solid product was collected and re-
crystallized from methanol. The purified product was obtained as green-
1
brownish powder (1.98 g, ca. 90%). H NMR (300 MHz, CDCl3): d=9.16
(d, J=1.8 Hz, 1H; HB), 8.72 (d, J=1.8 Hz, 1H; HE), 7.81 (s, 1H; H15),
7.70 (d, J=8.1 Hz, 1H; H12), 7.63 (d, J=7.8 Hz, 1H; H12’), 7.59–7.48 (m,
5H; H13, H13’, H9, H9’, H15’), 7.30–7.25 (m, 8H; H2), 7.19–7.11 (m, 10H;
H3, H6), 7.07–7.02 (m, 6H; H1, H8), 1.86–1.72 (m, 8H; Hf, Hf’), 1.15–1.06
(m, 24H; Hc, Hc’, Hd, Hd’, He, He’), 0.79 (t, J=7.2 Hz, 12H; Ha, Ha’),
758
www.chemeurj.org
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 749 – 760

Two-Photon Absorption of Small Dendritic Chromophores
FULL PAPER
23.54 (Cc'), 22.66 (Cb, Cb'), 14.13 ppm (Ca, Ca'); MALDI-TOF: m/z calcd
for C163H174N10: 2274.1927 [M]+; found: 2275.2559.
(CC), 150.54 (C5'), 147.87 (C4), 147.75 (CC), 147.36 (C7), 142.49 (C11),
142.30 (C11'), 136.39 (C10), 136.30 (CE), 136.19 (C10'), 135.31 (C14), 135.16
(C14'), 129.69 (C12), 129.20 (C3), 129.00 (CA), 124.40 (C15), 123.97 (C2),
123.31 (C13), 122.67 (C1), 121.03 (C6), 119.11 (CB), 118.92 (C9), 118.76
(C8), 118.68 (C9'), 55.28 (Cg), 55.14 (Cg'), 40.24 (Cf), 40.08 (Cf'), 31.64
(Ce), 31.58 (Ce'), 29.56 (Cd, Cd'), 23.81 (Cc), 23.63 (Cc'), 22.62 (Cb, Cb'),
14.13 ppm (Ca, Ca'); MALDI-TOF: m/z calcd for C245H260N4: 3401.7797
[M]+; found: 3401.8647.
Compound 1: [Pd
(0.035 g, 0.38 m mol), and PAHCTNUGTRENNNUG
(dba)3] (1.41 mg, 0.0014 mmol), sodium tert-butoxide
(tBu)3 (0.63 mg, 0.0032 mmol) were added to
a mixture of compounds 16 (0.7 g, 0.31 mmol) and 13 (0.37 g, 0.31 mmol)
in dry toluene (8 mL). The resulting solution was stirred at 908C under
an Ar atmosphere for 12 h. After cooling to room temperature, of H2O
(ca. 100 mL) was added to the reaction mixture. The solution was ex-
ACHTUNGTRENNUNGtracted with ethyl acetate (3ꢁ30 mL) and the organic layer was dried
over MgSO4. After removing the solvent, the crude product was purified
through column chromatography on silica gel by using THF/hexane
(1:10) as the eluent to give the final product as yellow powder (0.84 g, ca.
Acknowledgements
1
81%). H NMR (300 MHz, CDCl3): d=8.20 (d, J=9.3 Hz, 3H; HC), 8.02
(d, J=2.7 Hz, 3H; HF), 7.76 (dd, J1 =9.3, J2 =2.7 Hz, 3H; HB), 7.62–7.49
(m, 24H; H9, H12, H13, H15), 7.29–7.22 (m, 24H; H2), 7.15–7.10 (m, 30H;
H3, H6), 7.56–6.99 (m, 18H; H1, H8), 1.74 (s, 24H; Hf), 1.06–1.01 (m,
72H; Hc, Hd, He), 0.81–0.67 (m, 36H; Ha), 0.63 ppm (s, 24H; Hb);
13C NMR (75 MHz, CDCl3, tentative assignments based on calculates
values): d=154.56 (CG), 154.08 (CH), 152.65 (C5), 150.58 (C16), 147.93
(C4), 147.64 (CA), 147.43 (C11), 142.33 (C7), 141.70 (CD), 141.55 (CE),
138.86 (C10), 137.38 (CF), 137.21 (CC), 135.51 (C15), 135.49 (C9), 130.50
(C12), 129.17 (C3), 127.94 (CB), 125.55 (C13), 124.37 (C2), 123.87 (C14),
123.41 (C1), 120.86 (C6), 119.08 (C8), 55.09 (Cg), 40.11 (Cf), 31.57 (Ce),
29.57 (Cd), 23.84 (Cc), 22.62 (Cb), 14.12 ppm (Ca); MALDI-TOF: m/z
calcd for C246H261N13: 3399.7916 [M]+; found: 3399.8914.
T.C.L. and group members acknowledge the financial support from the
National Science Council of Taiwan (NSC) under Grant No. 99-2113M-
006-MY2. J.H.L. and group members acknowledge the financial support
from the National Science Council of Taiwan (NSC) under Grant No.
NSC 99-2112M-027-001-MY3.
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C. Katan, L.-O. Palsson, A. Beeby, J. A. Mosely, H. M. Kaiser, D.
Kaufmann, W.-Y. Wong, M. Blanchard-Desce, T. B. Marder, Chem.
Eur. J. 2009, 15, 198–208; k) F. Terenziani, V. Parthasarathy, A. Pla-
Quintana, T. Maishal, A.-M. Caminade, J.-P. Majoral, M. Blanchard-
Compound 2: [Pd
(0.033 g, 0.34 m mol), and PAHCTNUGTRENNNUG
(dba)3] (1.31 mg, 0.0013 mmol), sodium tert-butoxide
(tBu)3 (0.58 mg, 0.0029 mmol) were added to
a mixture of compounds 19 (0.8 g, 0.29 mmol) and 17 (0.42 g, 0.29 mmol)
in dry toluene (10 mL). The resulting solution was stirred at 908C under
an Ar atmosphere for 12 h. After cooling to room temperature, H2O (ca.
100 mL) was added to the reaction mixture. The solution was extracted
with ethyl acetate (3ꢁ30 mL) and the collected organic layer was dried
over MgSO4. After removing the solvent, the crude product was purified
through column chromatography on silica gel by using THF/hexane
(1:10) as the eluent to give the final product as yellow power (0.87 g, ca.
69%). 1H NMR (300 MHz, CDCl3): d=8.45 (s, 1H; HH), 8.18 (s, 3H;
HK), 7.92 (d, J=8.1 Hz, 3H; HD), 7.72–7.59 (m, 24H; H9, H12, H13, H15),
7.50–7.48 (m, 6H; HE, HB), 7.34–7.29 (m, 24H; H2), 7.21–7.18 (m, 30H;
H3, H6), 7.09–7.05 (m, 18H; H1, H8), 2.26–2.22 (m, 12H; Hf), 1.84–1.78
(m, 24H; Hf’), 1.21–1.04 (m, 108H; Hc, Hc’, Hd, Hd’, He, He’), 0.81–
0.75 ppm (m, 90H; Ha, Ha’, Hb, Hb’); 13C NMR (75 MHz, CDCl3, tentative
assignments based on calculates values): d=153.60 (C16), 153.41 (CN),
153.03 (CM), 152.68 (C5), 150.67 (CA), 150.59 (CL), 148.25 (CJ), 148.01
(C4), 147.47 (CF), 143.79 (CC), 141.52 (CI), 141.13 (C11, C7), 137.75 (C14),
137.68 (C14'), 135.69 (C10), 135.18 (CE), 129.22 (C2), 128.98 (C12), 124.49
(C15), 123.92 (C3), 123.49 (CK), 122.60 (C1), 122.24 (C13), 120.91 (C6),
119.21 (C9), 119.08 (C8, CH ), 118.26 (CD), 117.34 (CB), 55.36 (Cg), 55.10
(Cg'), 41.49 (Cf), 40.23 (Cf'), 31.86 (Ce, Ce'), 29.89 (Cd), 29.65 (Cd'), 23.89
(Cc, Cc'), 22.68 (Cb), 22.61 (Cb'), 14.18 ppm (Ca, Ca'); MALDI-TOF: m/z
calcd for C303H345N13: 4170.0685 [M]+; found: 4170.2090.
Compound 3: [Pd2ACHTUNGTRENNUNG(dba)3] (1.27 mg, 0.0014 mmol), sodium tert-butoxide
(0.05 g, 0.47 mmol), and Xantphos (3.8 mg, 0.0065 mmol) were added to
a mixture of compounds 22 (0.9 g, 0.4 mmol) and 20 (0.57 g, 0.47 mmol)
in dry toluene (15 mL). The resulting mixture stirred at 908C under an
Ar atmosphere for 12 h. After cooling to room temperature, H2O (ca.
100 mL) was added to the reaction mixture. The solution was extracted
with ethyl acetate (3ꢁ30 mL) and the organic layer was dried over
MgSO4. After removing the solvent, the crude product was purified
through column chromatography on silica gel by using THF/hexane (1:4)
as the eluent to give the final product as orange powder (0.71 g, ca.
1
53%). H NMR (300 MHz, CDCl3): d=9.20 (d, J=3 Hz, 1H; HB), 8.36
(d, J=3 Hz, 1H; HE), 7.78 (s, 1H; H15), 7.66 (d, J=8.1 Hz, 1H; H12), 7.60
(d, J=7.8 Hz, 1H; H12’), 7.58–7.49 (m, 5H; H13, H13’, H9, H9’, H15’), 7.30–
7.23 (m, 8H; H2), 7.16–7.09 (m, 10H; H3, H6), 7.08–7.01 (m, 6H; H1, H8),
1.82–1.68 (m, 8H; Hf, Hf’), 1.07–1.04 (m, 24H; Hc, Hc’, Hd, Hd’, He, He’),
0.70 (t, J=7.2 Hz, 12H; Ha, Ha’), 0.62 ppm (s, 8H; Hb, Hb’); C NMR
(75 MHz, CDCl3, tentative assignments based on calculates values): d=
13
157.21 (CG), 156.43 (CF), 152.80 (C16), 152.70 (C16'), 150.73 (C5), 150.67
Chem. Eur. J. 2013, 19, 749 – 760
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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Received: June 20, 2012
Revised: September 18, 2012
Published online: November 21, 2012
760
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Chem. Eur. J. 2013, 19, 749 – 760