Synthesis and two-photon absorption properties of star-shaped chromophores derived from functionalized fluorene units

Article abstract of DOI:10.1002/ejoc.201201236

A set of small star-shaped chromophores composed of three fluorene-based congeners have been synthesized and shown experimentally to possess strong and widely dispersed two-photon absorptivities in the visible to near-IR region under the irradiation of femtosecond and nanosecond laser pulses. In addition, the number of electron-donating fluorenyl units incorporated in the final structure was closely connected to the molecular two-photon activities of these model compounds. Effective optical power attenuation and stabilization behaviors of these dye molecules in the nanosecond time domain were also investigated. The results indicate that such a structural motif could be useful in the molecular design of strong two-photon absorbing material systems for quick-responding and broadband optical suppressing-related applications, particularly for laser pulses with long durations in the near-IR region. A set of star-shaped chromophores containing functionalized fluorene units were synthesized and shown to possess ascending two-photon absorptivities with the growth of their π systems. The observed effective optical power-limiting and stabilization behaviors in the nanosecond time domain indicate that these dye molecules have potential as broadband and quick-responding optical limiters. Copyright

Full text of DOI:10.1002/ejoc.201201236

FULL PAPER
DOI: 10.1002/ejoc.201201236
Synthesis and Two-Photon Absorption Properties of Star-Shaped
Chromophores Derived from Functionalized Fluorene Units
Tzu-Chau Lin,*[a] Che-Yu Liu,[a] Bor-Rong Huang,[a] Ja-Hon Lin,[b] Yu-Kai Shen,[b] and
Cheng-Yu Wu[b]
Keywords: Dendrimers / Multibranched pi systems / Two-photon absorption / Nonlinear optics / Chromophores /
Fluorescence
A set of small star-shaped chromophores composed of three
fluorene-based congeners have been synthesized and shown
experimentally to possess strong and widely dispersed two-
photon absorptivities in the visible to near-IR region under
the irradiation of femtosecond and nanosecond laser pulses.
In addition, the number of electron-donating fluorenyl units
incorporated in the final structure was closely connected to
the molecular two-photon activities of these model com-
pounds. Effective optical power attenuation and stabilization
behaviors of these dye molecules in the nanosecond time do-
main were also investigated. The results indicate that such a
structural motif could be useful in the molecular design of
strong two-photon absorbing material systems for quick-re-
sponding and broadband optical suppressing-related appli-
cations, particularly for laser pulses with long durations in
the near-IR region.
to a combination of several structural parameters such as
intramolecular charge-transfer efficiency and the effective
size of the π-conjugated domain within a molecule.[4–10] De-
pending on the application, photophysical properties in ad-
dition to a strong molecular 2PA may also be required of
designed molecules. For instance, to be utilized as an optical
power limiter that operates in a nanosecond regime, com-
pounds that have an extended excited-state lifetime may be
beneficial to the apparent nonlinear absorption because of
a two-photon-assisted excited-state absorption (2PA-as-
sisted ESA),[11] and, therefore, the effective optical power
attenuation would be enhanced. In searching for the con-
nection between structural parameters and nonlinear ab-
sorption properties in conjugated systems, we have been in-
terested in exploring the influence of the arrangement of
building units and the manner of substitution on the molec-
ular 2PA, as we construct multibranched π frameworks.
Herein, we present the synthesis of a new series of star-
shaped two-photon-active model chromophores 1–3, which
are derived from functionalized fluorene moieties, as well
as the initial investigations of their 2PA properties in the
femtosecond and nanosecond time domains.
Introduction
A two-photon absorption (2PA) process occurs when a
molecule is promoted from the ground state to an excited
state through the simultaneous absorption of two photons.
The theory of this nonlinear optical phenomenon was pre-
dicted by Maria Göppert-Mayer in 1931,[1] and the experi-
mental evidence for it came out about thirty years later,
when scientists observed the upconverted emission from
media under the irradiation of laser light with wavelengths
far from the linear absorption bands of the studied media.[2]
In the past fifteen years, the availability of stable and high
peak power lasers has triggered the momentum to explore
two-photon technologies. Many potential applications
based on 2PA in the emerging field of photonics and bio-
photonics have been proposed and explored including op-
tical power-limiting applications, frequency upconverted
lasing, 3D data storage, 3D microfabrication, nondestruc-
tive bioimaging and tracking, and two-photon-assisted
photodynamic therapy.[3] Organic compounds that exhibit
a large 2PA within the desired spectral region are of use in
these applications and, consequently, are in great demand.
So far, it has been realized that a molecular 2PA is related
Results and Discussion
[a] Photonic Materials Research Laboratory, Department of
Chemistry, National Central University,
The chemical structures and synthetic routes for the
studied model compounds are illustrated in Figure 1 and
Schemes 1 and 2, respectively. This model compound set
contains three multibranched congeners with the same ge-
neric structure, which has a nitrogen atom as the central
point of ramification to connect three electron-donating
branches of various sizes in their π framework. Compound
300 Jhong-Da Rd., Jhong-Li 32001, Taiwan
Fax: +886-3-4227664
E-mail: tclin@ncu.edu.tw
Homepage: http://140.115.43.2/index-eng.html
[b] Photonic Technology Laboratory, Department of Electro-
Optical Engineering, National Taipei University of Technology,
Taipei 10608, Taiwan
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201201236.
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Two-Photon Absorption of Star-Shaped Chromophores
1 is the smallest model chromophore, which uses (di- interesting to analyze the relationship between the molecu-
phenylamino)fluorene moieties as the branches, whereas lar 2PA and the π electrons added during the enlargement
compound 2 utilizes three fluorene units to form the inner of chromophore structure. Thus, we may elucidate either a
circle and incorporates six (diphenylamino)fluorene units at
the peripheries. On the basis of the same concept of struc-
tural expansion, compound 3 represents the largest model
chromophore and incorporates a total of nine fluorene
units in the inner circles and twelve (diphenylamino)fluor-
ene moieties at the peripheral positions. The molecular de-
sign of these chromophores originated from a simple at-
tempt to tentatively construct a set of symmetrically-substi-
tuted π frameworks with various numbers of attached elec-
tron-donating units. Therefore, upon light excitation, the re-
sulting fluorophores may possess a different extent of
charge transfer/redistribution, which in turn may be con-
nected to the molecular 2PA. Furthermore, it would be
Scheme 1. Synthesis for the central and peripheral parts of the final
model compounds.
Figure 1. Molecular structures of the studied model chromophores.
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beneficial or deleterious arrangement of each structural was found at approximately 400 nm (with εmax
≈
unit. On the other hand, the pendent alkyl chains on all 1.15ϫ105 cm–1 m–1 for 1, εmax ≈ 3.00ϫ105 cm–1 m–1 for 2,
fluorenyl moieties in these model chromophores are ex- and εmax ≈ 6.12ϫ105 cm–1 m–1 for 3). The model chromo-
pected to enhance the solubility in common organic sol- phore solutions also exhibited a strong two-photon-excited
vents, and this is an important parameter to be considered upconverted emission of purple-blue in color, which was
in the molecular design from either the aspect of experi- readily seen by the naked eye, even under the illumination
ments or applications. The synthetic procedures for these of an unfocused femtosecond laser beam at a low intensity
model dye molecules are relatively straightforward and level (λ ≈ 790 nm). Figure 3 illustrates the 2PA-induced
mainly involve consecutive functionalizations of the fluor- fluorescence spectra of compounds 1–3, and each inset
ene moiety and a Buchwald–Hartwig-type amination to
prepare the key intermediates and the final model com-
pounds (see Schemes 1 and 2). The syntheses for these key
intermediates and the final model compounds are described
in detail in the Exp. Sect.
Figure 2. (a) Linear absorption and (b) fluorescence spectra of
compounds 1–3 in solution phase (1ϫ10–6 m in THF).
Scheme 2. Synthetic procedures toward target model chromo-
phores.
Figure 2 illustrates the linear absorption and fluores-
Figure 3. Two-photon-excited fluorescence spectra of the studied
cence spectra of the studied dye molecules in solution phase
model chromophores. Insets: logarithmic plots of the power-
squared dependence of the 2PA-induced fluorescence intensity on
one-photon absorption (1PA) for these compounds the input intensity of these compounds in THF.
using THF (tetrahydrofuran) as the solvent. The intense
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Two-Photon Absorption of Star-Shaped Chromophores
curve in Figure 3 confirms that the 2PA process is the major
Using compound 1 as a reference point, Figure 4 shows
cause, in all cases, for the detected upconverted emission. that all of these model chromophores not only exhibit
To investigate and compare the dispersion of the 2PA be- nearly identical dispersion patterns of their two-photon ac-
havior of these dye molecules as a function of wavelength, tivities, but also show an ascending overall magnitude of
we conducted the degenerate two-photon-excited fluores- the 2PA from compounds 1 to 3. This feature indicates that
cence (2PEF) measurement in the near-IR regime (720– the gradual expansion of the π domain by attaching ad-
890 nm) using fluorescein (ca. 80 μm; in NaOH solution, ditional electron-donating units to the original trigonal
pH = 11) as the standard.[12,13] Figure 4 shows the mea- scaffold in compound 1 enhances the molecular 2PA with-
sured degenerate two-photon absorption spectra of these out shifting the major 2PA band of the dye system. Mole-
model compounds in THF, and the combined photophysi- cules with this property could be very beneficial to particu-
cal data are summarized in Table 1.
lar applications, when large multiphoton absorptivities
within a specific spectral region are required. Furthermore,
the observed increasing two-photon absorptivities within
the short wavelength region implies that for these com-
pounds the most accessible two-photon states are higher in
energy than those of the lowest allowed one-photon states.
Similar trends have been observed and reported previously
for other chromophore systems.[5a–5f,5i–5k,6a–6c,7d,8b,9c,10a–10f]
Additionally, for these model chromophores, analyzing the
relative increment of the observed overall magnitude of the
2PA within the studied spectral region has revealed that ex-
tending the size of the π system from compounds 1 to 2
leads to a larger promotion of the overall molecular 2PA.
However, further expansion of the π domain from com-
pounds 2 to 3 results in a comparatively smaller enhance-
ment of the overall 2PA. This feature indeed parallels the
trend of the relative incremental increase in the effective
π electron numbers[14] of these model chromophores (see
Figure 4 and Table 1), which indicates that during the mo-
lecular structure expansion from compounds 2 to 3, the
simultaneously added π electrons are not being utilized in
their full potential to promote a molecular 2PA. Therefore,
monotonically increasing the number of fluorene units and
using tertiary nitrogen atoms as the linkages in a molecule,
as demonstrated in this work, may not be the best method-
ology to enhance the molecular 2PA at the same level in
this dye system.
It is notable that the excited-state lifetimes of the studied
model chromophores are in the nanosecond range, which
implies that a significant excited-state population is retained
and, consequently, excited-state absorptions are possessed
during excitation by longer laser pulses. This is particularly
desirable with regards to optical power-limiting applica-
Figure 4. Measured degenerate two-photon absorption spectra of
model chromophores 1–3 (1ϫ10–4 m in THF) by 2PEF method
(with experimental error about 15%).
Table 1. Photophysical properties of the studied model compounds 1–3 in solution phase.
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tions in the nanosecond regime on the basis of 2PA-induced on the fact that a huge magnitude change in the input signal
excited-state absorptions (2PA-induced ESA), because the leads to only a small variation of output level.[15] This
effective three-photon absorption coefficient increases sig- means that a larger input power (or intensity) fluctuation
nificantly with the excited-state lifetime.[11f,11g] For this in- leads to a much smaller output fluctuation by passing
vestigation, to study the effective power-limiting perform- through a nonlinear absorptive medium such as the solu-
ance based on these model compounds, we utilized nanose- tion of model chromophore 3. The experimental results for
cond laser pulses at 720 nm as the representative probing the optical stabilization study based on the solution of com-
wavelength for the demonstration, because these model pound 3 are shown in Figure 6. The curves in parts a and
chromophores possess a comparatively stronger 2PA and b of this graphic are the instantaneous pulse energy changes
are theoretically expected to show better power-limiting in the input and output laser pulses at 720 nm, respectively.
properties at this wavelength. In our experiment, the non- For the purpose of comparison, the average levels for both
linear absorbing medium was a 1 cm path length solution the input and output signals were normalized to the same
of the studied dye in THF with concentration of 0.01 m. A value. The input pulses possess a relatively larger energy
tunable nanosecond laser system (an integrated Q-switched fluctuation as shown in Figure 6 (a), and after passing
Nd:YAG laser and OPO NT 342/3 from Ekspla) was em- through the solution of compound 3, a reduced fluctuation
ployed as an excitation laser light source to provide ca. 6 ns in the pulse energy is observed for the output signal as illus-
laser pulses with a controlled average pulse energy in the trated in Figure 6 (b).
range from ca. 0.02 to ca. 2 mJ and repetition rate of 10 Hz.
The laser beam was slightly focused onto the center of the
sample solution to obtain a nearly uniform laser beam ra-
dius within the whole cell path length, and the transmitted
laser beam from the sample cell was detected by an optical
power (energy) meter with a large detection area of ca.
25 mm in diameter. Figure 5 illustrates the measured power
attenuation performance based on these chromophore solu-
tions at ca. 720 nm. In this set of model compounds, com-
pound 3 displays a superior power restriction property at
720 nm in comparison to the other two analogues, and this
initial finding demonstrates the potential of using this
model fluorophore for broadband power-suppressing-re-
lated applications in the nanosecond regime.
Figure 6. (a) Measured instantaneous pulse energy fluctuations in
the input laser pulses and (b) measured instantaneous pulse energy
fluctuations in the output laser pulses. The repetition rate of the
laser pulses was 10 Hz, and the average input pulse energy level
was ca. 0.7 mJ.
Conclusions
Figure 5. Measured optical power-attenuation curves based on the
In summary, we have synthesized a new multipolar set of
sample solutions of compounds 1–3 under the excitation of nanose-
chromophores composed of three analogues with gradually
cond laser pulses at ca. 720 nm.
enlarged star-shaped skeletons containing functionalized
fluorene moieties. The initial experimental results indicate
On the other hand, the output/input curve shown in Fig- that these model fluorophores manifest strong and widely
ure 5 represents a characteristic type of optical control that dispersed two-photon absorptivities in the near IR-region.
is ideal for use in optical power (or intensity) stabilization. Tentative analysis of this model compound system for the
The principle of this type of optical stabilization is based correlation between molecular structure and the observed
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Two-Photon Absorption of Star-Shaped Chromophores
(200 mL) in a 500 mL three-neck flask. The resulting solution was
stirred and heated at reflux for 1 h. The entire system was then
cooled to room temp., and n-hexyl bromide (86.32 g, 0.52 mol) was
added. The reaction mixture was stirred and heated at reflux over-
night. After cooling to room temperature, the reaction mixture was
extracted with ethyl acetate and then washed with brine (2ϫ). The
combined organic layers were dried with anhydrous MgSO4 and
filtered, and then the solvent was removed by evaporation. The
crude product was purified by column chromatography on silica
overall 2PA behavior reveals that consecutively expanding
the size of π domain has a positive contribution on the en-
hancement of the 2PA. However, the first step of the struc-
tural expansion (from 1 to 2) offers a larger increment of
change in the overall molecular 2PA in comparison to the
second step of expansion in the π framework (from 2 to
3). This resembles the trend in the incremental increase in
effective π electron numbers upon the molecular size en-
largement. We also found that these model chromophores
gel (hexane) to afford the desired product (66.1 g, 87%) as a white
1
possess a strong nonlinear attenuation under the irradiation solid. H NMR (300 MHz, CDCl3): δ = 7.55–7.50 (d, J = 1.5 Hz,
2 H, HF), 7.502–7.501 (d, J = 8.4 Hz, 2 H, HC), 7.46–7.42 (dd, J1
of laser pulses working in the nanosecond regime, which
indicates that these compounds may have strong two-pho-
ton-assisted excited state absorptions within the studied
spectral region. The effective optical power-limiting/stabili-
= 1.5 Hz, J2 = 8.4 Hz, 2 H, HB), 1.937–1.882 (m, 4 H, Hb), 1.133–
1.032 (m, 12 H, He, Hd, Hc), 0.799–0.753 (t, 6 H, Hg), 0.631–0.602
(m, 4 H, Hf) ppm. 13C NMR (75 MHz, CDCl3): δ = 152.50 (CE),
139.01 (CD), 130.12 (CF), 126.15 (CC), 121.47 (CA), 121.05 (CB),
zation behaviors of these dendritic fluorophores also show
55.63 (Ca), 40.15 (Cb), 31.40 (Ce), 29.53 (Cd), 23.61 (Cc), 22.53 (Cf),
that such dye molecules are potential materials for broad-
band and quick-responding optical limiters/stabilizers
against laser lights with longer pulses.
13.95 (Cg) ppm. HRMS (FAB): calcd. for C25H32Br2 [M]+
490.0871; found 490.0870 [(79Br)(79Br)M]+, 492.0866 [(79Br)(81Br)-
M]+, 494.0850 [(81Br)(81Br)M]+.
7-Bromo-9,9-dihexyl-N,N-diphenyl-9H-fluoren-2-amine (7): A mix-
ture of compound 6 (50 g, 0.1015 mol), diphenylamine (18.9 g,
0.1118 mol), Pd2(dba)3 [0.93 g, 1.03 mmol, (dba = dibenzylidene-
acetone)], 2,2Ј-bis(diphenylphosphanyl)-1,1Ј-binaphthyl (BINAP,
1.895 g, 3.05 mmol), NaOtBu (13.65 g, 0.1421 mol), and toluene
(330 mL) was stirred and heated at 80 °C under nitrogen for 12 h.
The mixture was cooled to room temp. and then extracted with
brine/EA. The organic extract was dried and then concentrated by
a rotary evaporator. The residual brown oil (59 g) was transferred
to a column with silica gel (600 g, hexane) to afford the desired
compound 7 (31.78 g, 54%). 1H NMR (300 MHz, CDCl3): δ =
7.45–7.42 (d, J = 8.1 Hz, 1 H, H3), 7.418–7.368 (m, 3 H, H2, H8,
H11), 7.230–7.178 (m, 3 H, H9, H16), 7.128–7.083 (m, 5 H), 7.025–
6.940 (m, 4 H, H14), 1.86–1.80 (m, 4 H, Hb), 1.15–1.05 (m, 12 H,
Hc, Hd, He), 0.81–0.76 (t, J = 6.6 Hz, 6 H, Hg), 0.69–0.66 (m, 4 H,
Hf) ppm. 13C NMR (75 MHz, CDCl3): δ = 152.76 (C5), 151.67
(C12), 147.82 (C13), 147.49 (C10), 139.87 (C4), 135.00 (C7), 129.88
(C6), 129.13 (C15), 125.84 (C3), 123.84 (C14), 123.39 (C8), 122.58
(C16), 120.43 (C2), 120.35 (C1), 120.16 (C11), 118.99 (C9), 55.25
(Ca), 40.10 (Cb), 31.44 (Ce), 29.51 (Cd), 23.66 (Cc), 22.50 (Cf), 14.03
(Cg) ppm. HRMS (FAB): calcd. for C37H42BrN [M]+ 579.2501;
found 579.2501 [(79Br)M]+, 581.2507 [(81Br)M]+.
Experimental Section
General Methods: All commercially available reagents for the prep-
aration of the intermediates and targeted chromophores were ob-
tained from Aldrich Chemical Co. and, unless stated otherwise,
were used as received. THF was distilled from sodium benzophen-
one ketyl. 1H and 13C NMR spectroscopic data were recorded with
either a 200 or 300 MHz spectrometer and were referenced to TMS
or the residual CHCl3. For the NMR signal assignments, the repre-
sentative numbering schemes for the carbon and hydrogen atoms
in each intermediate and model chromophore are systematized and
illustrated in the Supporting Information. High resolution mass
spectroscopy was conducted with a Waters LCT ESI-TOF mass
spectrometer. MALDI-TOF MS spectra were obtained with a
Voyager DE-PRO mass spectrometer (Applied Biosystem,
Houston, USA). For the syntheses of the key intermediates and
the targeted model compounds, a series of functionalization steps
starting from purchased compound 4 were conducted.
2,7-Dibromo-9,9-dihexyl-9H-fluorene (5): Fluorene (4, 30 g,
0.18 mol) and zinc chloride (28.3 g, 0.21 mol) were dissolved in
acetic acid (200 mL), and then benzyltrimethylammonium tri-
bromide (BTMABr3, 73.8 g, 0.189 mol) was added. The resulting
solution was heated at reflux and stirred for 6 h. After the comple-
tion of reaction, NaHSO3 (aqueous) was added to neutralize the
excess amount of BTMABr3. The mixture was extracted with ethyl
acetate (300 mL) and then washed with brine (2ϫ300 mL). The
organic layer was filtered and dried with MgSO4. After filtration,
the solvent was removed in vacuo. The crude product was recrys-
tallized from ethyl acetate (EA)/methanol to afford the desired
product (50.3 g, 86%) as a white solid. 1H NMR (300 MHz,
CDCl3): δ = 7.623–7.620 (d, J = 0.9 Hz, 2 H, HF), 7.560–7.533 (d,
J = 8.1 Hz, 2 H, HC), 7.481–7.450 (dd, J1 = 0.9 Hz, J2 = 8.1 Hz, 2
H, HB), 3.802 (s, 2 H, NH2) ppm. 13C NMR (75 MHz, CDCl3): δ
= 144.68 (CE), 139.56 (CD), 130.02 (CF), 128.17 (CC), 121.07 (CB),
120.84 (CA), 36.45 (Ca, sp3-hybridized carbon) ppm. HRMS
(FAB): calcd. for C13H8Br2 [M]+ 321.8993; found 321.8994
[(79Br)(79Br)M]+, 323.8980 [(79Br)(81Br)M]+, 325.8968 [(81Br)(81Br)-
M]+.
9,9-Dihexyl-N2,N2-diphenyl-9H-fluorene-2,7-diamine (8): Com-
pound 7 (20 g, 0.0344 mol), CuI (8.2 g, 0.0344 mmol), and potas-
sium phthalimide (7.95 g, 0.0344 mmol) were combined with di-
methylacetamide (DMAc, 400 mL) in a 1000 mL three-neck flask,
and the resulting mixture was heated at reflux and stirred over-
night. After completion of reaction, the DMAc was removed in
vacuo first, and the resulting mixture was extracted (2ϫ) with a
mixture of ethyl acetate (250 mL)/brine (250 mL)/aqueous NH4OH
(100 mL). The combined organic layers were dried with MgSO4,
filtered, and concentrated in vacuo to obtain a dark yellow oil. To
this crude product were added hydrazine hydrate (1.25 g,
21.5 mmol) and methanol (100 mL), and the resulting solution was
heated at reflux and stirred for 6 h. After the completion of reac-
tion, the solvent was removed in vacuo, and the reaction mixture
was filtered to remove the white impurities. The filtrate was then
concentrated, and the resulting residue was purified by a short sil-
ica gel column (EA/hexane, 1:6) to obtain the target compound
(11.6 g, 65%) as a yellow oil. 1H NMR (300 MHz, CDCl3): δ =
2,7-Dibromo-9,9-dihexyl-9H-fluorene (6): Compound
0.2 mol) and NaOtBu (76.9 g, 0.8 mol) were combined with THF
5
(50.0 g, 7.438–7.386 (m, 2 H, H3, H8), 7.326–7.196 (m, 4 H, H14, H11),
7.114–7.06 (m, 5 H, H2, H11), 6.991–6.944 (m, 3 H, H6, H16), 6.61–
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6.59 (m, 2 H, H2, H9), 3.728 (s, 2 H, NH2), 1.817–1.763 (m, 4 H,
by column chromatography on silica gel (hexane/dichloromethane,
10:1) to afford the desired product (11.96 g, 90%) as a pale yellow
Hb), 1.116–1.049 (m, 12 H, Hc, Hd, He), 0.863–0.795 (t, J = 6.6 Hz,
6 H, Hg), 0.64 (m, 4 H, Hf) ppm. 13C NMR (300 MHz, CDCl3): δ solid. 1H NMR (300 MHz, CDCl3): δ = 8.300–8.266 (dd, J1
=
= 152.56 (C12), 151.14 (C5), 148.11 (C13), 145.42 (C10), 145.38 (C1), 2.1 Hz, J2 = 8.1 Hz, 1 H, HB), 8.241–8.234 (d, J = 2.1 Hz, 1 H,
137.26 (C7), 132.24 (C4), 129.01 (C15), 124.07 (C1), 123.26 (C16), HF,) 7.809–7.782 (d, J = 8.1 Hz, 1 H, HC) 7.683–7.656 (d, J =
121.97 (C14), 119.99 (C6), 119.94 (C9), 118.95 (C8), 113.92 (C2),
8.1 Hz, 1 H, HH), 7.575–7.569 (d, J = 1.8 Hz, 1 H, HK) 7.555–
109.76 (C3), 54.77 (Ca), 40.48 (Cb), 31.53 (Ce), 29.65 (Cd), 23.69 7.523 (dd, J1 = 1.8 Hz, J2 = 8.1 Hz, 1 H, HI), 2.1–1.8 (m, 4 H, Hb),
(Cc), 22.56 (Cf), 14.05 (Cg) ppm. HRMS (FAB): calcd. for 1.2–0.9 (m, 12 H, Hc, Hd, He), 0.8–0.7 (t, 6 H, Hg), 0.7–0.5 (m, 4
C37H44N2 [M + H]+ 516.3504; found 516.3505.
H, Hf) ppm. 13C NMR (75 MHz, CDCl3): δ = 154.28 (CA), 151.51
(CE), 147.33 (CL), 146.33 (CD), 137.64 (CG), 130.62 (CC), 126.47
(CF), 123.60 (CK), 123.31 (CH), 122.38 (CB), 119.86 (CJ), 118.18
(HI), 54.99 (Ca), 40.45 (Cb), 31.45 (Ce), 29.59 (Cd), 23.51 (Cc),
22.50, (Cf), 13.97 (Cg) ppm. HRMS (FAB): calcd. for C25H34O2N
[M + H]+ 458.1695; found 458.1690.
9,9-Dihexyl-9H-fluorene (9): Fluorene (4, 15.0 g, 0.09 mol), potas-
sium iodide (14.9 mg, 0.9 mmol), and NaOtBu (34.6 g, 0.36 mol)
were combined with THF (200 mL) in a 500 mL three-neck flask.
The resulting mixture was stirred and heated at reflux for 1 h. The
entire system was then cooled to room temp., and n-hexyl bromide
(38.8 g, 0.23 mol) was added. The mixture was stirred and heated
at reflux overnight. After cooling to room temperature, the reaction
mixture was diluted with ethyl acetate (250 mL), and the resulting
solution was washed with brine (2ϫ250 mL). The organic layer
was dried with anhydrous MgSO4 and filtered, and the solvent was
removed in vacuo. The crude product was then purified by column
chromatography on silica gel (hexane) to afford the desired product
7-Bromo-9,9-dihexyl-9H-fluoren-2-amine (12): Compound 11 (3 g,
6.54 mmol) was dissolved in ethyl acetate (40 mL), and then
SnCl2·2H2O (14.78 g, 65.4 mmol) was added. The mixture was
heated at reflux and stirred for 6 h. After completion of reaction,
NaHCO3 (aqueous solution, 200 mL) was added to quench the ex-
cess amount of SnCl2·2H2O. The mixture was diluted with ethyl
acetate (200 mL), and the resulting solution was washed with brine
(17.4 g, 60%) as a pale yellow liquid. 1H NMR (300 MHz, CDCl3): (2ϫ200 mL). The organic layer was dried with MgSO4 and then
δ = 7.709–7.678 (m, 2 H, HF), 7.350–7.234 (m, 6 H, HA, HB, HC), filtered. The solvent was removed by evaporation. The crude prod-
1.979–1.924 (m, 4 H, Hb), 1.110–1.015, (m, 12 H, Hc, Hd, He),
uct was purified by column chromatography on silica gel (hexane/
0.774–0.728 (t, J = 6.6 Hz, 6 H, Hg), 0.629–0.607 (m, 4 H, Hf) ppm.
EA, 8:1) to afford the desired product (1.99 g, 71%) as a pale yel-
13C NMR (75 MHz, CDCl3): δ = 150.63 (CE), 1141.05 (CD), 126.94 low solid. H NMR (300 MHz, CDCl3): δ = 7.418–7.359 (m, 4 H,
1
(CF), 126.63 (CC), 122.78 (CB), 119.59 (CA), 54.95 (Ca), 40.38 (Cb),
HC, HI, HK), 6.606–6.583 (m, 2 H, HB, HF), 3.654 (s, 2 H, NH2),
31.48 (Ce), 29.71 (Cd), 23.68 (Cc), 22.58 (Cf), 14.01 (Cg) ppm. 1.890–1.827 (m, 4 H, Hb), 1.2–0.9 (m, 12 H, Hc, Hd, He), 0.8–0.7
HRMS (FAB): calcd. for C25H34 [M]+ 334.2661; found 334.2665.
9,9-Dihexyl-2-nitro-9H-fluorene (10): Compound (15 g,
(t, J = 6.6 Hz, 6 H, Hg), 0.7–0.5 (m, 4 H, Hf) ppm. 13C NMR
(75 MHz, CDCl3): δ = 52.19 (CE), 151.97 (CA), 146.28 (CL), 131.10
(CD), 129.56 (CG), 125.68 (CC), 120.52 (CK), 119.54 (CJ), 118.90
(CI), 113.94 (CF), 109.43 (CB), 54.99 (Ca), 40.46 (Cb), 31.42 (Ce),
29.62 (Cd), 23.56 (Cc), 22.53, (Cf), 13.94 (Cg) ppm. HRMS (FAB):
calcd. for C25H34BrN [M + H]+ 428.4482; found 428.4361.
9
0.015 mol) was dissolved in acetic acid (200 mL). The resulting
solution was cooled to 10 °C over 10 min, and then nitric acid
(15 mL, 0.045 mmol) was added dropwise. After the addition, the
resulting solution was stirred at 10 °C for 15 min. NaOH (1 m aque-
ous solution, 100 mL) was added to neutralized the excess amount
of nitric acid. The mixture was diluted with ethyl acetate (200 mL),
and the resulting solution was washed with brine (2ϫ200 mL). The
organic layer was dried with anhydrous MgSO4 and then filtered,
and the solvent was removed in vacuo. The crude product was puri-
fied by column chromatography on silica gel (hexane/dichlorometh-
ane, 10:1) to afford the desired product (11.11 g, 71%) as a pale
yellow solid. 1H NMR (300 MHz, CDCl3): δ = 8.280–8.245 (dd, J1
= 2.1 Hz, J2 = 8.4 Hz, 1 H, HE), 8.206–8.199 (d, J = 2.1 Hz, 1 H,
HF) 7.807–7.779 (d, J = 8.4 Hz, 1 H, HC) 7.798–7.772 (m, 1 H,
2-Bromo-9,9-dihexyl-7-iodo-9H-fluorene (13): A mixture of com-
pound 12 (7 g, 16.3 mmol), HCl (12 n solution, 120 mL), water
(480 mL), and NaNO2 (2.24 g, 0.033 mol) in a 1000 mL three-neck
round-bottom flask was stirred at 0 °C for 1 h. A solution of potas-
sium iodide (10.8 g, 65.2 mmol) in water (30 mL) was added, and
then the entire system was stirred at room temperature overnight.
After completion of reaction, a saturated aqueous solution of
NaHSO3 (100 mL) was added, and the resulting mixture was ex-
tracted with ethyl acetate (180 mL) and washed with brine
(2ϫ100 mL). The organic phase was dried with anhydrous MgSO4,
HH), 7.440–7.368 (m, 3 H, HI, HJ, HK), 1979–1.924 (m, 4 H, Hb), and the solvent was removed in vacuo. The crude product was then
1.110–1.015, (m, 12 H, Hc, Hd, He), 0.774–0.727 (t, 6 H, Hg), 0.629– purified by column chromatography on silica gel (hexane) to afford
0.607 (m, 4 H, Hf) ppm. 13C NMR (75 MHz, CDCl3): δ = 152.17 the desired product (4.48 g, 51%) as a white solid. 1H NMR
(CD), 151.84 (CL), 147.55 (CA), 147.00 (CD), 138.60 (CF), 129.16
(CC), 127.27 (CK), 123.15(CH), 123.07 (CJ), 121.09 (CI), 119.67
(300 MHz, CDCl3): 7.65–7.63 (m, 2 H), 7.52–7.50 (m, 1 H), 7.45–
7.38 (m, 3 H), 1.93–1.87 (m, 4 H), 1.15–1.03 (m, 12 H), 0.80–0.75
(CF), 118.09 (CB), 55.54 (Ca), 39.97 (Cb), 31.33 (Ce), 29.44 (Cd), (m, 6 H), 0.60–0.53 (m, 4 H) ppm. 13C NMR (75 MHz, CDCl3): δ
23.60 (Cc), 22.43 (Cf), 13.86 (Cg) ppm. HRMS (FAB): calcd. for
C25H34O2N [M + H]+ 380.2590; found 380.2589.
= 152.56 (CL), 152.20 (CE), 139.54 (CG), 138.98 (CD), 135.95 (CK),
131.96 (CF), 130.05 (CH), 126.03 (CC), 121.56 (CJ), 121.34 (CI),
121.05 (CB), 93.04 (CA), 55.48 (Ca), 40.0 (Cb), 31.34 (Ce), 29.50
(Cd), 23.57 (Cb), 22.5 (Cf), 13.9 (Cg) ppm. HRMS (FAB): calcd. for
C25H32BrI [M + H]+ 428.4482; found 428.4361.
2-Bromo-9,9-dihexyl-7-nitro-9H-fluorene (11): Compound 10 (11 g,
0.029 mol) and zinc chloride (9.09 g, 0.067 mol) were combined
with acetic acid (150 mL) in a 500 mL three-neck flask, and then
BTMABr3 (23.8 g, 0.061 mmol) was added. The resulting mixture
was heated at reflux and stirred for 6 h. After completion of reac-
tion, NaHSO3 (aqueous solution, 200 mL) was added to quench
the excess amount of BTMABr3. The mixture was extracted with
ethyl acetate (200 mL) and washed with brine (2ϫ200 mL). The
organic layer was dried with MgSO4 and then filtered, and the sol-
vent was removed by evaporation. The crude product was purified
Tris(7-bromo-9,9-dihexyl-9H-fluoren-2-yl)amine (14): A mixture of
compound 12 (1.30 g, 4.11 mmol), compound 13 (3.85 g,
9.02 mmol), CuI (380 mg, 2.00 mmol), 1,10-phenanthroline
(360 mg, 2.00 mmol), and KOH (2.30 g, 40.99 mmol) in o-xylene
(10 mL) was added to a 250 mL three-neck flask, and the resulting
mixture was heated at 130 °C for 24 h under argon. The solution
was cooled to room temp. and then extracted (3ϫ) with a mixture
504
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© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2013, 498–508

Two-Photon Absorption of Star-Shaped Chromophores
of EA (100 mL)/brine (100 mL)/NH4OH (50 mL). The combined
organic layers were dried with anhydrous MgSO4. The solvent was
removed in vacuo by a rotary evaporator. The resulting residue was
purified by column chromatography on silica gel (hexane/CH2Cl2,
15:1) to provide compound 14 (2.14 g, 41.4%) as a yellow solid. 1H
NMR (300 MHz, CDCl3): δ = 7.520–7.469 (d, J = 8.4 Hz, 3 H,
HC), 7.479–7.451 (d, J = 8, 4 Hz, 3 H, HH) 7.469–7.418 (m, 6 H,
HI, HK) 7.220–7.213 (d, J = 2.1 Hz, 3 H, HF) 7.023–6.989 (dd, J1
NMR (75 MHz, [D6]acetone): δ = 152.44 (CL), 151.46 (C5, C12),
151.17 (CE), 147.68 (C13), 147.45 (C17), 146.28 (C10), 146.19 (C1),
139.96 (CG), 136.09 (C7), 135.86 (C4), 134.26 (CD), 129.62 (CI),
128.85 (C15), 125.62 (C8), 123.45 (C3), 123.11 (C14), 122.98 (C6),
122.27 (C19), 122.14 (C16), 120.42 (CH), 120.30 (CK), 119.75 (CF),
119.67 (C11), 119.34 (CJ), 119.17 (C9), 117.99 (C2), 117.14 (CB),
54.95 (CaЈ), 54.57 (Ca), 39.63 (Cb, CbЈ), 31.34 (Ce), 29.10 (Cd), 23.48
(Cc), 21.96 (Cf), 13.16 (Cg) ppm. HRMS (FAB): theoretical average
= 2.1 Hz, J2 = 8.1 Hz, 3 H) 1.941–1.789 (m, 12 H, Hb), 1.171–1.076 calcd. for C99H116BrN3 [M + H]+ 1428.9495; found 1428.9543.
(m, 36 H, He, Hd, Hc), 0.859–0.906 (t, J = 6.6 Hz, 18 H, Hg), 0.721–
N2-(9,9-Dihexyl-7-nitro-9H-fluoren-2-yl)-N2-[7-(diphenylamino)-9,9-
dihexyl-9H-fluoren-2-yl]-9,9-dihexyl-N7,N7-diphenyl-9H-fluorene-
2,7-diamine (17): Compound 11 (1.71 g, 3.74 mmol), compound 15
(3.8 g, 3.74 mmol), and NaOtBu (0.50 g, 5.24 mmol) were com-
bined with dry toluene (50 mL) in a 250 mL three-neck flask. To
the solution were quickly added Pd2(dba)3 (34.3 mg, 0.037 mol)
and P(tBu)3 (15.1 mg, 0.075 mmol). The resulting mixture was
stirred and heated at reflux for 4 h under argon. After completion
of reaction, the entire system was cooled to room temp. and diluted
with EA (100 mL), and the resulting mixture was washed with
brine (2ϫ100 mL). The organic layer was collected and dried with
MgSO4. After filtration, the solvent was removed by rotary evapo-
ration, and the crude mixture was purified by column chromatog-
raphy (CH2Cl2/hexane, 1:5) to afford 17 (3.59 g, 69%) as a yellow
0.597 (m, 12 H, Hf) ppm. 13C NMR (75 MHz, CDCl3): δ = 152.61
(CL), 151.67 (CE), 147.18 (CA), 139.99 (CG), 135.04 (CD), 129.94
(CK), 125.98 (CH), 123.02 (CI), 120.47 (CC), 120.35 (CF), 120.19
(CJ), 118.04 (CB), 55.36 (Ca), 40.24 (Cb), 31.63 (Ce), 29.64 (Cd),
23.83 (Cc), 22.59 (Cf), 14.07 (Cg) ppm. HRMS (FAB): calcd. for
C75H96Br3N [M + H]+ 1247.5093; found 1247.6011.
N2-[7-(Diphenylamino)-9,9-dihexyl-9H-fluoren-2-yl]-9,9-dihexyl-
N7,N7-diphenyl-9H-fluorene-2,7-diamine (15): Compound 7 (15 g,
29 mmol), compound 8 (16.9 g, 29 mmol), and NaOtBu (3.3 g)
were first combined with dry toluene (100 mL) in a 500 mL three-
neck flask, and to this were quickly added Pd2(dba)3 (133 mg,
0.145 mol) and P(tBu)3 (59 mg, 0.29 mmol). The resulting mixture
was stirred and heated at reflux for 4 h under argon. After comple-
tion of reaction, the entire system was cooled to room temp. and
diluted with EA (200 mL). The resulting mixture was washed with
brine (2ϫ200 mL). The organic layer was collected and dried with
1
powder. H NMR (300 MHz, [D6]acetone): δ = 8.299–8.293 (d, J
= 1.8 Hz, 1 H, HK), 8.260–8.226 (dd, J1 = 1.8 Hz, J2 = 8.1 Hz, 1
H, HI), 7.875–7.829 (d, J = 8.1 Hz, 1 H, HH), 7.847–7.801 (d, J =
MgSO4. After filtration, the solvent was removed by rotary evapo- 8.1 Hz, 1 H, HC), 7.675–7.621 (m, 4 H, H3, H8), 7.373–7.181 (m,
ration, and the crude residue was purified by column chromatog-
12 H, HB, HF, H11, H15), 7.111–7.001 (d, 18 H, H2, H6, H9, H14,
H16), 2.232–2.144 (m, 4 H, HbЈ), 2.192–1.862 (m, 8 H, Hb), 1.126–
1.118 (m, 36 H, He, HeЈ, Hd, HdЈ, Hc, HcЈ), 0.884–0.760 (m, 30 H,
raphy (THF/hexane, 1:20) to obtain 15 (21.1 g, 69%) as a brown
1
solid. H NMR (300 MHz, [D6]acetone): δ = 7.631–7.604 (d, J =
8.1 Hz, 2 H, H8), 7.613–7.586 (d, J = 8.1 Hz, 2H, H3), 7.319–7.313 Hg, HgЈ, Hf, HfЈ) ppm. 13C NMR (75 MHz, [D6]acetone): δ =
(d, J = 1.8 Hz, 2 H, H11), 7.301–7.248 (m, 8 H, H15), 7.154–7.148 153.36 (CJ), 151.56 (C5), 151.50 (C12), 150.97 (CG), 149.03 (CL),
(d, J = 1.8 Hz, 2 H, H6), 7.089–7.033 (m, 8 H, H14), 7.008–6.964
(m, 8 H, H16, H3, H6), 1.963–1.889 (m, 8 H, Hb), 1.203–1.117 (m,
24 H, Hc, Hd, He), 0.820–0.774 (t, J = 6.6 Hz, 12 H, Hg), 0.744–
147.60 (C13), 147.37 (CE), 146.43 (C10), 145.89 (CA), 145.67 (C1),
136.53 (C7), 135.77 (C4), 132.14 (CD), 128.81 (C15), 123.71 (C8),
123.32 (C3), 123.15 (C14), 132.01 (C6), 122.16 (C16), 121.89 (CH),
0.720 (m, 8 H, Hf) ppm. 13C NMR (75 MHz, [D6]acetone): δ = 121.22 (CC), 119.80 (C11, CK), 119.01 (C9), 118.82 (C2), 118.58
52.71 (C12), 152.22 (C5), 149.11 (C13), 146.82 (C10), 143.78 (C7),
(CF), 117.60 (CB), 115.53 (CI), 55.08 (CaЈ), 54.57 (Ca), 39.56 (Cb),
138.32 (C1), 134.43 (C4), 130.13 (C15), 125.00 (C8), 124.22 (C14), 39.25 (CbЈ), 31.10 (Ce, CeЈ), 29.32 (Cd, CdЈ), 23.47 (Cc), 23.36 (CcЈ),
123.25 (C16), 121.26 (C3), 120.86 (C11), 120.35 (C6), 117.80 (C9), 21.92 (Cf), 13.15 (Cg) ppm. HRMS (FAB): calcd. for C99H116N4O2
111.58 (C2), 55.74 (Ca), 41.36 (Cb), 32.47 (Ce), 29.68 (Cd), 24.79 [M + H]+ 1393.9177; found 1393.9221.
(Cc), 23.33 (Cf), 14.43 (Cg) ppm. HRMS (FAB): calcd. for
N2-(7-Amino-9,9-dihexyl-9H-fluoren-2-yl)-N2-[7-(diphenylamino)-9,9-
dihexyl-9H-fluoren-2-yl]-9,9-dihexyl-N7,N7-diphenyl-9H-fluorene-
2,7-diamine (18): Compound 17 (2.0 g, 1.43 mmol) and
C74H85N3 [M + H]+ 1015.6743; found 1015.6738.
N2-(7-Bromo-9,9-dihexyl-9H-fluoren-2-yl)-N2-[7-(diphenylamino)-9,9-
dihexyl-9H-fluoren-2-yl]-9,9-dihexyl-N7,N7-diphenyl-9H-fluorene-2,7- SnCl2·2H2O (3.23 g, 14.3 mmol) were dissolved in EA (15 mL), and
diamine (16): Compound 6 (1.76 g, 3.56 mmol), compound 15
(4.0 g, 3.94 mmol), and NaOtBu (0.48 g, 5.0 mmol) were combined
with dry toluene (48 mL) in a 250 mL three-neck flask. Pd2-
(dba)3 (32.3 mg, 39.4 μmol) and 1,1Ј-bis(diphenylphosphanyl)ferro-
cene (dppf, 16.4 mg, 0.107 mmol] were then added, and the re-
sulting mixture was stirred and heated at reflux for 12 h under ar-
gon. After completion of reaction, the entire system was cooled to
room temp. and then diluted with EA (200 mL). The resulting solu-
tion was washed with brine (2ϫ200 mL). The organic layer was
collected and dried with MgSO4. After filtration, the solvent was
removed by rotary evaporation, and the crude residue was purified
by column chromatography (CH2Cl2/hexane, 1:5) to afford 16
the resulting solution was stirred and heated at reflux for 6 h. To
the mixture was added a saturated aqueous solution of NaHCO3
(30 mL) to quench the excess amount of SnCl2·2H2O. The reaction
mixture was filtered, and the filtrate was then extracted (2ϫ) with
a mixture of EA (90 mL)/brine (200 mL). The combined organic
layers were dried with MgSO4. After filtration and removal of sol-
vent in vacuo, the crude product was purified by column
chromatography (EA/hexane, 1:8) to obtain 18 (1.37 g, 70%) as a
yellow solid. 1H NMR (300 MHz, [D6]acetone): δ = 7.648–7.620
(d, J = 8.4 Hz, 2 H, H3), 7.631–7.604 (d, J = 8.1 Hz, 2 H, H8),
7.523–7.496 (d, J = 8.1 Hz, 1 H, HC), 7.442–7.416 (d, J = 8.1 Hz,
1 H, HH), 7.323–7.295 (m, 8 H, H15), 7.244–7.237 (d, J = 2.1 Hz,
(3.05 g, 60.1 %) as a yellow powder. 1H NMR (300 MHz, [D6]- 2 H, H6), 7.185–7.179 (d, J = 1.8 Hz, 2 H, H11), 7.119–7.008 (m,
acetone): δ = 7.726–7.699 (d, J = 8.1 Hz, 1 H), 7.670–7.638 (m, 6
H), 7.512–7.479 (dd, J1 = 1.8 Hz, J2 = 8.1 Hz, 1 H), 7.324–7.272
16 H, H2, H9, H14, H16, HB, HF), 6.756–6.750 (d, J = 1.8 Hz, 1 H,
HK), 6.688–6.655 (dd, J1 = 1.8 Hz, J2 = 8.1 Hz, 1 H, HI), 4.746 (s,
(m, 11 H), 7.194–7.188 (d, J = 1.8 Hz, 2 H), 7.117–7.007 (m, 16 1 H, NH2), 2.011–1.798 (m, 12 H, Hb, HbЈ), 1.224–1.132 (m, 36 H,
H), 1.915–1.862 (m, 12 H, Hb, HbЈ), 1.126–1.111 (m, 36 H, Hc, HcЈ,
Hd, HdЈ, He, HeЈ), 0.899–0.785 (m, 30 H, Hg, HgЈ, Hf, HfЈ) ppm. 13
He, HeЈ, Hd, HdЈ, Hc, HcЈ), 0.891–0.791 (m, 30 H, Hg, HgЈ, Hf,
C
HfЈ) ppm. 13C NMR (75 MHz, [D6]acetone): δ = 151.72 (CL),
Eur. J. Org. Chem. 2013, 498–508
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505

T.-C. Lin et al.
FULL PAPER
151.40 (C5, C12), 150.41 (CE), 147.78 (C13), 147.69 (CJ), 146.72
(C10), 146.10 (C1), 144.77 (CA), 137.65 (CD), 136.40 (C7), 135.11
(C4), 130.02 (CG), 128.90 (C15), 123.59 (C3, C8), 123.44 (CC), 123.14
(C14), 122.14 (C16), 119.67 (C11), 119.62 (C6), 119.56 (C11), 118.85
(CF), 118.35 (CB), 117.09 (C9), 113.01 (CI), 54.60 (Ca), 54.22 (CaЈ),
40.23 (CbЈ), 39.79 (Cb), 31.32 (Ce, CeЈ), 29.46 (Cd, CdЈ), 23.58 (Cc,
CcЈ), 22.11 (Cf, CfЈ), 14.02 (Cg, CgЈ) ppm. HRMS (FAB): theoretical
average calcd. for C99H118N4 [M + H]+ 1365.0584; found
1365.0741.
HRMS (MALDI-TOF): calcd. for C111H126N4 [M]+ 1514.9983;
found 1515.0012.
Compound 2: Compound 14 (0.32 g, 0.26 mmol), compound 15
(0.861 g, 0.84 mmol), and NaOtBu (0.1 g, 1.08 mmol) were com-
bined with dry toluene (8 mL) in a high pressure tube. Then,
Pd2(dba)3 (3.51 mg, 3.84 μmol) and P(tBu)3 (1.6 mg, 7.7 μmol)
were added, and the reaction vessel was purged with argon and
sealed tightly. The resulting mixture was stirred and heated at reflux
for 12 h. After completion of reaction, the entire system was cooled
to room temperature. The reaction mixture was diluted with EA
(50 mL), and the resulting solution was washed with brine
(2ϫ50 mL). The organic layer was dried with MgSO4 and then
filtered. The crude mixture was purified by column chromatog-
raphy CH2Cl2/hexane, 1:5) to afford pure compound 2 (0.301 g,
28.8%) as a yellow powder. 1H NMR (300 MHz, C6D6): δ = 7.656–
7.608 (m, 12 H, H9, H11), 7.592–7.564 (d, J = 8.4 Hz, 3 H, HH)
7.575–7.548 (d, J = 8.4 Hz, 3 H, HC) 7.532–7.504 (d, J = 8.4 Hz,
6 H, H3), 7.408–7.381 (d, J = 8.4 Hz, 6 H, H8), 7.331–7.310 (m, 18
H, H6, H16), 7.240–7.208 (m, 24 H, H15), 7.133–7.080 (m, 30 H,
H14, H2), 6.886–6.838 (m 12 H, H18, HB, HF, HI), 1.918–1. 761H
(m, 36 H, HbЈ, Hb), 1.265–0.837 (m, 198 H, HcЈ, Hc, Hd, HdЈ, He,
HeЈ, HfЈ, Hf, Hg, HgЈ) ppm. 13C NMR (75 MHz, C6D6): δ = 152.57
(C5), 152.43 (C12, C21, C28), 148.65 (C13), 147.32 (C1, CA, CJ),
147.09 (C10), 136.84 (CD, CG), 136.62 (C7), 136.51 (C4), 129.55
(C15), 128.10 (C8), 124.24 (C14), 123.80 (CH), 123.69 (CH), 123.54
(C3), 122.82 (C16), 120.37 (C6, CF, CK), 119.87 (C11), 119.03 (CI),
118.92 (CB), 118.74 (C9) ppm. HRMS (MALDI-TOF): theoretical
average calcd. for C297H348N10 [M]+ 4058.1201; found 4058.1387.
N2-{7-[(7-{Bis[7-(diphenylamino)-9,9-dihexyl-9H-fluoren-2-yl]amino}-
9,9-dihexyl-9H-fluoren-2-yl)amino]-9,9-dihexyl-9H-fluoren-2-yl}-N2-
[7-(diphenylamino)-9,9-dihexyl-9H-fluoren-2-yl]-9,9-dihexyl-N7,N7-di-
phenyl-9H-fluorene-2,7-diamine (19): Compound 16 (1.2 g,
0.84 mmol), compound 18 (1.26 g, 0.92 mmol), NaOtBu (0.112 g,
1.17 mmol), Pd2(dba)3 (4 mg, 4.4 μmol), and P(tBu)3 (2 mg,
8.4 μmol) were combined with dry toluene (15 mL) in a 100 mL
brown three-neck flask. The resulting mixture was heated at reflux
and stirred for 6 h. After completion of reaction, the mixture was
washed with brine (50 mL) and then extracted with ethyl acetate
(50 mL). The organic layer was dried with MgSO4 and then fil-
tered. The solvent was removed in vacuo. The crude product was
purified by column chromatography on silica gel (ethyl acetate/hex-
1
ane, 1:15) to give the final purified product (1.54 g, ca. 67%). H
NMR (300 MHz, C6D6): δ = 7.662–7.633 (dd, J1 = 1.5 Hz, J2
=
8.1 Hz, 6 H, HC, H6), 7.588–7.561 (d, J = 8.1 Hz, 2 H, HH) 7.541–
7.514 (d, J = 8.1 Hz, 2 H, HF), 7.531–7.504 (d, J = 8.1 Hz, 4 H,
H3), 7.412–7.385 (d, J = 8.1 Hz, 4 H, H8), 7.349–7.316 (dd, J1
=
2.1 Hz, J2 = 8.1 Hz, 10 H, H16, HK), 7.270–7.215 (m, 20 H, H11,
H15), 7.135–7.083 (m, 18 H, H14, HB), 6.886–6.839 (m, 10 H, H2,
H9, HI), 5.356 (s, 1 H, amino hydrogen), 2.000–1.978 (m, 8 H, HbЈ),
1.858–1.766 (m, 16 H, Hb), 1.247–1.086 (m, 72 H, Hc, HcЈ, Hd, HdЈ,
He, HeЈ), 0.866–0.835 (m, 60 H, Hf, HfЈ, Hg, HgЈ) ppm. 13C NMR
(75 MHz, C6D6): δ = 152.61 (C5), 152.48 (C12, CE), 152.00 (CL),
148.72 (C13), 147.78 (C10), 147.11 (C1), 146.92 (CA), 142.65 (CJ),
137.30 (CD), 136.97 (C7), 136.44 (C4), 134.89 (CG), 129.61 (C15),
128.10 (C8), 124.29 (C14), 124.10 (CC), 123.47 (C3), 122.86 (C16),
120.56 (C11), 120.47 (C6) 120.40 (CK), 120.04 (CH), 119.96 (C2),
119.38 (C9), 118.63 (CF), 117.54 (CB), 112.29 (CI), 55.56 (CaЈ),
55.51 (Ca), 41.20 (CbЈ), 40.56 (Cb), 32.16 (CeЈ), 32.06 (Ce), 30.42
(CdЈ), 30.17 (Cd), 24.70 (CcЈ), 24.57 (Cc), 23.12 (CfЈ), 23.06 (Cf),
14.4 (Cg) ppm. HRMS (MALDI-TOF): calcd. for C198H233N7
[M]+ 2708.8447; found 2708.8523.
Compound 3: Compound 14 (0.189 g, 0.152 mmol), compound 19
(1.398 g, 0.516 mmol), NaOtBu (62.3 mg, 0.638 mmol), Pd2(dba)3
(5.7 mg, 6.22 μmol), and P(tBu)3 (2.0 mg, 9.9 μmol) with dry tolu-
ene (6 mL) were added to a high pressure tube. The reaction vessel
was purged with argon and sealed tightly. The entire system was
stirred at –110 °C for 12 h. After completion of reaction, the mix-
ture was cooled to room temperature and extracted (2ϫ) with a
mixture of brine (50 mL)/ethyl acetate (50 mL). The combined or-
ganic layers were dried with MgSO4 and then filtered. After re-
moval of the solvent, the crude residue was purified by column
chromatography on silica gel (CH2Cl2/hexane, 1:3) to give the final
1
purified product (0.402 g, 29%). H NMR (300 MHz, C6D6): δ =
7.659–7.611 (m, 24 H, H9, H11), 7.595–7.568 (d, J = 8.1 Hz, 9 H,
HCЈ, HH), 7.575–7.548 (d, J = 8.1 Hz, 9 H, HHЈ, HC) 7.532–7.505
(d, J = 8.1 Hz, 12 H, H3), 7.408–7.381 (d, J = 8.1 Hz, 12 H, H8),
7.475–7.437 (m, 3 H, HKЈ), 7.354–7.278 (m, 36 H, H16, H6), 7.237–
7.210 (m, 48 H, H15), 7.133–7.081 (m, 60 H, H2, H14), 7.042–7.015
(m, 6 H, HBЈ, HFЈ), 6.953–6.773, (m, 27 H, HI, HIЈ, HF, HK, HB)
1.915–1.764 (m, 84 H, Hb, HbЈ, HbЈЈ), 1.263–0.838 (m, 462 H, Hc,
HcЈ, HcЈЈ, Hd, HdЈ, HdЈЈ, He, HeЈ, HeЈЈ, Hf, HfЈ, HfЈЈ, Hg, HgЈ,
HgЈЈ) ppm. 13C NMR (75 MHz, C6D6): δ = 152.64 (C5, CE), 152.56
(CL, CEЈ), 152.51 (C12), 148.72 (C13), 147.40 (C1, CJ, CJЈ, CA, CAЈ),
147.17 (C10), 136.91 (C4, CGЈ), 136.69 (CDЈ, CG), 136.59 (C7, CDЈ),
129.62 (C15), 128.10 (C8), 124.32 (C14), 123.86 (CC, CCЈ), 123.80
(CH, CHЈ), 123.61 (C3), 122.89 (C16), 120.44 (C6), 119.94 (C11),
119.11 (CI, CIЈ), 119.04 (CB, CBЈ), 118.94 (C2), 118.82 (C9), 55.67
(CaЈЈ), 55.52 (Ca, CaЈ), 40.79 (CbЈЈ), 40.56 (Cb, CbЈ). 32.24 (CeЈЈ),
32.07 (Ce, CeЈ). 30.30 (CdЈЈ), 30.17 (Cd, CdЈ), 24.81 (CcЈЈ), 24.57 (Cc,
CcЈ), 23.14(CfЈЈ), 23.06 (Cf, CfЈ), 14.49 (CgЈЈ), 14.41 (Cg, CgЈ) ppm.
HRMS (MALDI-TOF): theoretical average calcd. for C669H792N22
[M + H]+ 9142.8896; found 9142.8555.
Compound 1: Compound 7 (0.95 g, 1.63 mmol), compound 15
(1.5 g, 1.48 mmol), and NaOtBu (0.199 g, 2.07 mmol) were com-
bined with dry toluene (10 mL) in a 50 mL three-neck flask. To the
solution were added Pd2(dba)3 (13.6 mg, 14.8 μmol) and P(tBu)3
(6.0 mg, 29.6 mmol), and the resulting mixture was stirred and
heated at reflux for 4 h under argon. After completion of reaction,
the entire system was cooled to room temperature, washed with
brine (50 mL), and extracted with ethyl acetate (2ϫ50 mL). The
combined organic layers were dried with MgSO4 and then filtered.
The crude mixture was purified by column chromatography (THF/
hexane, 1:20) to afford pure compound 1 (1.55 g, 69%) as a yellow
1
powder. H NMR (300 MHz, [D6]acetone): δ = 7.656–7.629 (d, J
= 8.1 Hz, 6 H, H3, H8), 7.303–7.250 (m, 15 H, H9, H15), 7.165–
7.159 (d, J = 1.8 Hz, 3 H, H6), 7.095–6.984 (m, 21 H, H2, H14,
H16), 1.920–1.797 (m, 12 H, Hb), 1.196–1.019 (m, 36 H, Hc, Hd,
He), 0.8–0.7 (t, J = 5.7 Hz, 18 H, Hg), 0.798–0.701 (m, 12 H,
Hf) ppm. 13C NMR (75 MHz, [D6]acetone): δ = 151.83 (C12),
148.10 (C5), 146.79 (C13, C10), 146.59 (C1), 136.59 (C7), 135.96 (C4),
129.25 (C15), 123.88 (C3), 123.50 (C16), 123.08 (C6), 122.52 (C14),
Supporting Information (see footnote on the first page of this arti-
120.10 (C8), 120.02 (C9), 119.62 (C2), 118.11 (C11), 54.96 (Ca), 40.06 cle): Representative numbering of carbon and hydrogen atoms for
(Cb), 31.56 (Ce), 29.43 (Cd), 23.91 (Cc), 22.37 (Cf), 13.58 (Cg) ppm. various structural units and optical experiment details.
506
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Eur. J. Org. Chem. 2013, 498–508

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F. Meng, A. Rebane, Y. Stepanenko, E. Nickel, C. W. Spangler,
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