Synthesis and optical properties, including two-photon absorption cross-sections, of differentially functionalized starburst-type π-conjugated molecules

Article abstract of DOI:10.1246/bcsj.82.1416

Differentially functionalized hexakis(p-substituted-phenylethynyl)benzene and hexakis[4-(p-substituted-styryl)- phenylethynyl]benzene derivatives with various (D_6h, D_3h, D_2h, and C_2v) symmetries were synthesized

Full text of DOI:10.1246/bcsj.82.1416

1416 Bull. Chem. Soc. Jpn. Vol. 82, No. 11, 1416–1425 (2009)
© 2009 The Chemical Society of Japan
Synthesis and Optical Properties, Including Two-Photon Absorption
Cross-Sections, of Differentially Functionalized Starburst-Type
³-Conjugated Molecules#
Kenji Kobayashi,*1 Yuto Kita,1 Motoyuki Shigeiwa,2 Satoru Imamura,2 and Shuuichi Maeda2
1Department of Chemistry, Faculty of Science, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529
2Mitsubishi Chemical Group Science and Technology Research Center, Inc.,
1000 Kamoshida, Aoba-ku, Yokohama 227-8502
Received June 2, 2009; E-mail: skkobay@ipc.shizuoka.ac.jp
Differentially functionalized hexakis(p-substituted-phenylethynyl)benzene and hexakis[4-(p-substituted-styryl)-
phenylethynyl]benzene derivatives with various (D6h, D3h, D2h, and C2v) symmetries were synthesized by Sonogashira
cross-coupling reactions. The optical properties of this starburst-type ³-conjugated system were investigated. Among
them, hexakis[4-(p-dioctylaminostyryl)phenylethynyl]benzene (5) showed the largest two-photon absorption cross-section
of ¤ = 818 GM at 800 nm, which was determined by open aperture Z-scan with 120 fs laser pulses in toluene solution.
Organic chromophores with large two-photon absorption
(TPA) cross-sections have potential applications in new
technologies,1 including three-dimensional (3-D) optical data
storage,2 two-photon optical power limiting,3 two-photon 3-D
microfabrication,2b,4 photodynamic therapy,5 and 3-D fluores-
cence imaging.6 The concept that intramolecular charge-trans-
fer, from the ends of a ³-conjugated system to the center or
vice versa, upon excitation is correlated with enhanced TPA
properties has been widely accepted for the design of molecules
with large TPA cross-sections.1 Molecular systems that have
been intensively investigated so far include quasilinear D-³-A
dipolar molecules,7 and quasilinear D-³-D, A-³-A, and
D-A-D quadrupolar molecules,1a,8 where D is a donor group,
A is an acceptor group, and ³ is a ³-conjugated bridge. As
extended systems, quasilinear D-³-A-³-D,9 D-A-³-A-D,
D-A-D-A-D, and D-D-A-D-D systems,10 tri-branched-octu-
polar systems,11 and tetra-branched-cruciform systems12 have
also been developed. It has been pointed out that expansion of
³-conjugation, as well as multichromophore systems, lead to
enhanced TPA abilities.
additional donors and/or acceptors with various symmetries
and extended ³-conjugation would significantly influence
optical properties in the starburst-type hexa(arylethynyl)-
benzene system. Here, we report the synthesis and optical
properties, including TPA cross-sections, of differentially
functionalized hexakis(p-substituted-phenylethynyl)benzene
derivatives 1-4 and hexakis[4-(p-substituted-styryl)phenyl-
ethynyl]benzene derivatives 5-13 (Chart 1). Among them,
hexakis[4-(p-dioctylaminostyryl)phenylethynyl]benzene
(5)
showed the largest TPA cross-section of ¤ = 818 GM at
800 nm, which was determined by open aperture Z-scan with
120 fs laser pulses in toluene solution.
Results and Discussion
Synthesis. The synthesis of hexakis(p-substituted-phenyl-
ethynyl)benzenes 2 and 3 with C2v and D3h symmetries,
respectively, has already been reported.15 Hexakis(p-dioctyl-
aminophenylethynyl)benzene (1), hexakis[4-(p-dioctylamino-
styryl)phenylethynyl]benzene (5), hexakis[4-(p-octylstyryl)-
phenylethynyl]benzene (6), and hexakis{4-[p-bis(p-octyl-
phenyl)aminostyryl]phenylethynyl}benzene (13) with D6h
symmetry were synthesized by the Sonogashira cross-coupling
reactions of hexabromobenzene with p-dioctylaminophenyl-
acetylene (14), 4-(p-dioctylaminostyryl)phenylacetylene (15),
4-(p-octylstyryl)phenylacetylene (16), and 4-[p-bis(p-
octylphenyl)aminostyryl]phenylacetylene (17), respectively
(Schemes 1a and 1b). 1,3,5-Tris(p-dioctylaminophenyl-
ethynyl)-2,4,6-tris[4-(p-octylstyryl)phenylethynyl]benzene (4)
with D3h symmetry was prepared by the Sonogashira coupl-
ing reaction of 1,3,5-tribromo-2,4,6-tris(p-dioctylaminophenyl-
ethynyl)benzene15 with 16 (Scheme 1c).
Hexa(phenylethynyl)benzene and 1,3,5-tris(p-dihexylamino-
phenylethynyl)-2,4,6-tris(p-nitrophenylethynyl)benzene
are
known to exhibit third-order and second-order nonlinear optical
properties, respectively.13 A multiannulene molecule with D3h
symmetry shows a large TPA cross-section.14 Previously, we
have reported the synthesis of differentially functionalized
hexakis(p-substituted-phenylethynyl)benzene derivatives with
D6h, D3h, and C2v symmetries by the Sonogashira cross-
coupling reaction of 1,3,5-tribromo-2,4,6-triiodobenzene with
one or two kinds of p-substituted-phenylacetylene(s).15 Major
advantages of the hexa(arylethynyl)benzene system are 1) the
ease of introducing six chromophores onto the benzene core
with various symmetries and 2) the high planarity of the
molecule efficiently forming the fully ³-conjugated starburst
system. We are interested in learning whether the presence of
The Sonogashira coupling reaction of 1,3,5-tribromo-2,4,6-
triiodobenzene15 with 3 equiv of 15 gave 1,3,5-tribromo-
2,4,6-tris[4-(p-dioctylaminostyryl)phenylethynyl]benzene (18)
and
1,3-dibromo-2,4,5,6-tetrakis[4-(p-dioctylaminostyryl)-
Published on the web November 10, 2009; doi:10.1246/bcsj.82.1416

K. Kobayashi et al.
Bull. Chem. Soc. Jpn. Vol. 82, No. 11 (2009) 1417
moiety with malononitrile (Scheme 2c).
1,2,4,5-Tetrakis[4-(p-dioctylaminostyryl)phenylethynyl]-3,6-
bis[4-(p-nitrostyryl)phenylethynyl]benzene (10) with D2h sym-
metry as a counterpart of 8 with C2v symmetry was synthesized
by the Sonogashira coupling reaction of 1,2,4,5-tetrabromo-
3,6-bis(trimethylsilylethynyl)benzene (27)16 with 15, followed
by desilylation, and subsequent coupling reaction with 4-
bromo-4¤-nitrostilbene (Scheme 3).
One-Photon Absorption Properties.
The one-photon
absorption spectral data of 1-13 and representative absorption
spectra are summarized in Table 1 and Figure 1, respectively.
The absorption maxima (-(1)max) were in the range from 399 to
464 nm in CHCl3. In a series of hexakis(p-substituted-phenyl-
ethynyl)benzene derivatives 1-3, -(1)
was red-shifted as
max
the number of end nitro groups was increased:15,17 1 (D6h) <
2 (C2v) < 3 (D3h).
By extension of the ³-conjugation with a styryl group,
(1)
-
of hexakis[4-(p-dioctylaminostyryl)phenylethynyl]-
max
benzene (5) was red-shifted by ca. 30 nm relative to that of
hexakis(p-dioctylaminophenylethynyl)benzene (1).8a,12a In
a
series of hexakis[4-(p-substituted-styryl)phenylethynyl]-
benzene derivatives with D6h symmetry, -(1)
showed red
max
shifts upon increasing the electron-donating ability of the end
functional groups: 6 (octyl) < 13 (bis(p-octylphenyl)amino) <
5 (dioctylamino).8a,15 The -(1)
of 4 showed a red shift
max
relative to 1 and 6, resulting from a combination of ³-
conjugation extension and electron-donating effect of the end
functional group. In marked contrast to a series of hexakis-
(p-substituted-phenylethynyl)benzene derivatives, -(1)
of
max
hexakis[4-(p-substituted-styryl)phenylethynyl]benzene deriva-
tives was slightly blue-shifted as the number of strong electron-
withdrawing groups was increased: 5 (D6h) ² 7 (C2v) ² 8
(C2v) > 10 (D2h) > 9 (D3h) in the combination of dioctylamino
and nitro groups, and 5 (D6h) > 11 (C2v) > 12 (D3h) in the
combination of dioctylamino and 2,2-dicyanoethenyl groups.
At this stage, the reason for this unusual result is not clear. In
all cases, no notable solvatochromism of -(1)max was observed,
although a slight red shift was observed as the dielectric
Chart 1. Structures of 1-13.
phenylethynyl]benzene (19) in 48% and 14% yields, respec-
tively (Scheme 2a). When 4 equiv of 15 was used under the
same conditions, 18, 19, and 1-bromo-2,3,4,5,6-pentakis[4-(p-
dioctylaminostyryl)phenylethynyl]benzene (20) were obtained
in 25%, 42%, and 6% yields, respectively. The Sonogashira
coupling reaction of building blocks 18 (D3h symmetry), 19
(C2v symmetry), and 20 (C2v symmetry) with 4-(p-nitrostyryl)-
phenylacetylene (21) produced 1,3,5-tris[4-(p-dioctylamino-
styryl)phenylethynyl]-2,4,6-tris[4-(p-nitrostyryl)phenylethynyl]-
benzene (9), 1,2,3,5-tetrakis[4-(p-dioctylaminostyryl)phenyl-
ethynyl]-4,6-bis[4-(p-nitrostyryl)phenylethynyl]benzene (8),
and 1,2,3,4,5-pentakis[4-(p-dioctylaminostyryl)phenylethyn-
yl]-6-[4-(p-nitrostyryl)phenylethynyl]benzene (7), respectively
(Scheme 2b). 1,3,5-Tris{4-[p-(2,2-dicyanoethenyl)styryl]phen-
ylethynyl}-2,4,6-tris[4-(p-dioctylaminostyryl)phenylethynyl]-
benzene (12) and 1,3-bis{4-[p-(2,2-dicyanoethenyl)styryl]-
phenylethynyl}-2,4,5,6-tetrakis[4-(p-dioctylaminostyryl)phenyl-
ethynyl]benzene (11) were prepared by the Sonogashira
coupling reaction of 4-[p-(1,3-dioxolan-2-yl)styryl]phenyl-
acetylene (22) with 18 and 19, respectively, followed by
hydrolysis of the acetal moiety of the resulting coupling
products, and subsequent reaction of the resulting aldehyde
constant of the solvents was increased.18 For 5, -(1)
was
max
changed as follows: hexane (425 nm) < toluene (440 nm) <
CHCl3 (443 nm) < THF (447 nm) < CH2Cl2 (450 nm).
One-Photon Fluorescence Properties. The one-photon
fluorescence spectral data of 1-13 and representative fluores-
cence spectra are summarized in Table 1 and Figure 2,
respectively. In both series of 1-4 and 5-13, derivatives with
nitro or 2,2-dicyanoethenyl groups were scarcely fluorescent,15
whereas the other derivatives were highly fluorescent. The
emission maxima (-emmax) of these derivatives were in the
range from 482 to 548 nm and showed relatively large Stokes
¹1
shifts in the range from 4040 to 4690 cm in CHCl3.
By extension of ³-conjugation with a styryl group, -emmax of
5 was red-shifted by 45 nm relative to that of 1. In a series of
hexakis[4-(p-substituted-styryl)phenylethynyl]benzene deriva-
tives with D6h symmetry, -em
showed red shifts upon
max
increasing the electron-donating ability of the end functional
groups: 6 (octyl) < 13 (bis(p-octylphenyl)amino) < 5 (dioctyl-
amino). Thus, a combination of ³-conjugation extension and
electron-donating effect of the end functional group provides
enhanced Stokes shifts except for 4. The fluorescence quantum

1418 Bull. Chem. Soc. Jpn. Vol. 82, No. 11 (2009)
Starburst-Type ³-Conjugated Molecules
Scheme 1. Synthesis of 1, 4, 5, 6, and 13. Reagents and conditions: (a) arylacetylenes (9-12 equiv), PdCl2(PPh3)2 (7-10 mol %), CuI
(14-20 mol %), PPh3 (14-20 mol %), Et3N, reflux.
yield (Φf) was also increased by extension of ³-conjugation
with a styryl group (1 < 5) and electron-donating effect of the
end functional group (7 ¹ 6 < 13 < 5). Among 1-13, com-
pound 5 showed the largest fluorescence quantum yield of 0.91
in toluene. In marked contrast to the absorption spectra, the
derivatives bearing dioctylamino or bis(p-octylphenyl)amino
groups showed a notable solvatochromism of the emission
as the dielectric constant of the solvents was increased (5,
13 vs. 6), indicative of a polar excited state that is stabilized
by polar solvents.17 The solvatochromism was especially
notable on extension of ³-conjugation with a styryl group (5
discussion of the structure-TPA properties cannot be made at
this stage because of no measurements at wavelengths other
than 800 nm, the following four items seem to be noteworthy
concerning TPA cross-sections in a series of hexakis(p-sub-
stituted-phenylethynyl)benzene derivatives 1-4 and hexakis[4-
(p-substituted-styryl)phenylethynyl]benzene derivatives 5-13.
Item 1: Among 1-13, hexakis[4-(p-dioctylaminostyryl)-
phenylethynyl]benzene (5) showed the largest TPA cross-
section of ¤ = 818 GM at 800 nm.23 The power density
dependence of transmittance of 5 is shown in Figure 4.
Item 2: TPA cross-sections would be enhanced as the
vs. 1). For 5, -em
and Stokes shift were changed as fol-
result of ³-conjugation extension with a styryl group:8a
1
max
lows: hexane (-emmax = 483 nm, Stokes shift = 2830 cm¹1) <
toluene (514 nm, 3270 cm¹1) < CHCl3 (548 nm, 4330 cm¹1) <
THF (594 nm, 5540 cm¹1) < CH2Cl2 (602 nm, 5610 cm¹1), as
shown in Figure 3.18,19
(¤ = 111 GM) < 5 (818 GM); 2 (175 GM) < 8 (396 GM); and
3 (135 GM) < 9 (275 GM).
Item 3: TPA cross-sections would be enhanced upon
increasing the electron-donating ability of the end functional
groups in a series of hexakis[4-(p-substituted-styryl)phenyl-
ethynyl]benzene derivatives with D6h symmetry:8a 6 (octyl,
¤ = 84 GM) < 13 (bis(p-octylphenyl)amino, 532 GM) < 5 (di-
octylamino, 818 GM).
Item 4: Although compounds 2, 3, and 7-12 with nitro or
2,2-dicyanoethenyl groups were scarcely fluorescent, they
showed moderate or good TPA cross-sections.
Two-Photon Absorption Cross-Sections. The two-photon
absorption (TPA) cross-sections of 1-13 at 800 nm were
determined by open aperture Z-scan with 120 fs laser pulses
in toluene solution.11f,20,21 The results are summarized in
Table 1. N,N-Diphenyl-7-[2-(4-pyridyl)ethenyl]-9,9-didecyl-
9H-fluoren-2-amine (AF-50) was used as a TPA benchmark.7
In contrast to two-photon fluorescence method,22 the open
aperture Z-scan technique is applicable to the TPA-measure-
ment of nonfluorescent compounds. All compounds studied in
this work have different absorption maxima, and would exhibit
the maximum TPA at different wavelengths. Although detailed
Conclusion
We have demonstrated the synthesis of differentially
functionalized hexakis(p-substituted-phenylethynyl)benzene

K. Kobayashi et al.
Bull. Chem. Soc. Jpn. Vol. 82, No. 11 (2009) 1419
Scheme 2. Synthesis of 7, 8, 9, 11, 12, 18, 19, and 20. Reagents and conditions: (a) 15 (3-4 equiv), PdCl2(PPh3)2 (2 mol %), CuI
(4 mol %), PPh3 (4 mol %), Et3N, reflux; (b) 21 (3-6 equiv), PdCl2(PPh3)2 (3-9 mol %), CuI (6-18 mol %), PPh3 (6-18 mol %),
Et3N-THF, reflux; (c) 22 (4-4.5 equiv), PdCl2(PPh3)2 (6-9 mol %), CuI (12-18 mol %), PPh3 (12-18 mol %), Et3N, reflux; (d) 1 M
HCl (12 equiv), THF, rt; (e) CH2(CN)2 (12 equiv), Et3N (25 mol %), PhCO2H (20 mol %), CH2Cl2, rt.
and hexakis[4-(p-substituted-styryl)phenylethynyl]benzene de-
Experimental
rivatives with various (D6h, D3h, D2h, and C2v) symmetries, and
General. Compounds 2 and 3 were synthesized according
presented a systematic approach to structure-optical property
to the literature.15 Et3N and THF were distilled from CaH2
investigations in this starburst-type ³-conjugated system. The
and sodium-benzophenone ketyl, respectively, under an argon
one-photon absorption and fluorescence properties and two-
atmosphere. The other solvents and all commercially available
photon absorption (TPA) cross-sections were significantly
affected by the combination of ³-conjugation extension and
reagents were used without any further purification. 1H and
13C NMR spectra were recorded at 400 and 100 MHz, respectively,
electron-donating effect of the end functional groups,8a as well
on a JEOL JNM-AL400 spectrometer. UV-vis spectra were
as by the donor number of them.14b In this system, hexakis[4-
measured on a Shimadzu UV-2450. Fluorescence spectra were
(p-dioctylaminostyryl)phenylethynyl]benzene (5) showed the
measured on a JASCO FP-6300. Recycle preparative GPC was
largest fluorescence quantum yield of 0.91 in toluene, and the
performed on a Japan Analytical Industry LC-9204 with poly-
largest TPA cross-section of ¤ = 818 GM at 800 nm, which was
determined by the open aperture Z-scan technique with 120 fs
laser pulses in toluene solution. Study on more detailed TPA
properties of this starburst-type ³-conjugated system is
currently underway in our laboratory.
styrene gel columns (JAIGEL 1H-40 and 2H-40).
Hexakis( p-dioctylaminophenylethynyl)benzene (1).
mixture of hexabromobenzene (88.2 mg, 0.160 mmol), PdCl2-
(PPh3)2 (11.2 mg, 0.016 mmol), CuI (6.1 mg, 0.032 mmol), and
PPh3 (8.4 mg, 0.032 mmol) under an argon atmosphere were added
To a

1420 Bull. Chem. Soc. Jpn. Vol. 82, No. 11 (2009)
Starburst-Type ³-Conjugated Molecules
Table 1. One- and Two-Photon Properties of 1-13 and AF-50
(1)
em
¹1
-
max/nm (log ¾)
CHCl3
-
max/nm (Φf)a)
Stokes shiftb)/cm
Compd
¤c)/GMd)
Toluene
Toluene
CHCl3
Toluene
CHCl3
1
408
415
489
503
4060
4220
111
(5.11)
429
(4.98)
453
(4.96)
419
(5.18)
440
(5.35)
398
(5.37)
440
(5.34)
402, 439
(5.14, 5.14)
398
(5.15)
425
(5.23)
436
(5.20)
426
(5.02)
433
(5.24)
433
(5.01)
464
(4.97)
425
(5.14)
443
(5.37)
399
(5.40)
441
(0.57)
nae)
(0.49)
na
2
na
na
na
na
175
135
123
818
84
3
4
na
na
498
513
(0.41)
548, 578
3790
3270
4250
3610
na
4040
4330
4320
na
5
514
(0.91)
479
(0.39)
523
(0.03)
na
6
482
(0.44)
na
7
516
396
275
357
371
365
532
45
(5.29)
8
406, 434
(5.27, 5.26)
401
(5.24)
426
(5.30)
439
(5.36)
433
na
na
na
9
na
na
na
10
11
12
13
AF-50
531
(0.02)
na
na
4700
na
na
na
na
na
na
na
na
(5.29)
434
(5.32)
506
(0.83)
545, 572
3330
4690
(5.23)
394
a) Fluorescence quantum yield relative to 9,10-bis(phenylethynyl)anthracene in cyclohexane (Φf = 1.00). b) ¦E =
1/-(1) ¹ 1/-emmax. c) Two-photon absorption cross-section at 800 nm which was determined by open aperture
max
Z-scan with 120 fs laser pulses in toluene solution. The experimental uncertainty of ¤ value amounts to «12%.
d) 1 GM = 1 © 10¹50 cm4 s photon¹1 molecule¹1. e) na: Not available.
Figure 1. One-photon absorption spectra of 1, 5, 6, and 13
in CHCl3 at 1 © 10¹5 M.
Et3N (10 mL) and then a solution of p-dioctylaminophenyl-
acetylene (14)15 (492 mg, 1.44 mmol) in Et3N (3 mL). The
resulting mixture was stirred at refluxing temperature for 24 h.
After evaporation of Et3N, the residue was triturated with hexane
and filtered. After evaporation of the filtrate, the residue was
Scheme 3. Synthesis of 10. Reagents and conditions: (a) 15
(7 equiv), PdCl2(PPh3)2 (10 mol %), CuI (20 mol %), PPh3
(20 mol %), Et3N, reflux; (b) n-Bu4NF (2 equiv), THF,
rt; (c) 4-bromo-4¤-nitrostilbene (12 equiv), Pd(PPh3)4
(10 mol %), CuI (20 mol %), Et3N-THF, reflux.
subjected to short-pass column chromatography on Al2O3 eluted
with CHCl3 followed by recycle preparative GPC to give 1
(243 mg, 72% yield). Deep red solid; mp <40 °C; 1H NMR
(CDCl3): ¤ 7.53 (d, J = 8.8 Hz, 12H), 6.61 (d, J = 8.8 Hz, 12H),
3.32 (t, J = 7.0 Hz, 24H), 1.68-1.58 (m, 24H), 1.41-1.29 (m,

K. Kobayashi et al.
Bull. Chem. Soc. Jpn. Vol. 82, No. 11 (2009) 1421
lene (15). To a mixture of NaH (60% in mineral oil, 0.910 g,
22.7 mmol) and 15-crown-5 (0.39 mL, 2.0 mmol) in THF (60 mL)
at 0 °C under an argon atmosphere was added a mixture of p-
(dioctylamino)benzaldehyde (5.24 g, 15.4 mmol) and diethyl p-
bromobenzylphosphonate24 (2.85 g, 15.4 mmol) in THF (30 mL)
at 0 °C.25 The resulting mixture was stirred at 0 °C to room
temperature for 24 h. After quenching with H2O at 0 °C, the
reaction mixture was extracted with Et2O. The organic layer was
washed with H2O and brine and dried over Na2SO4. After
evaporation of solvents, the residue was subjected to column
chromatography on silica gel eluted with hexane-CHCl3 (4:1) to
give trans-4-bromo-4¤-(dioctylamino)stilbene (9.42 g, 96% yield).
Pale yellow solid; 1H NMR (CDCl3): ¤ 7.43 (d, J = 8.5 Hz,
2H), 7.37 (d, J = 8.8 Hz, 2H), 7.33 (d, J = 8.5 Hz, 2H), 7.02 (d,
J = 16.2 Hz, 1H), 6.80 (d, J = 16.2 Hz, 1H), 6.62 (d, J = 8.8 Hz,
2H), 3.28 (t, J = 7.6 Hz, 4H), 1.65-1.55 (m, 4H), 1.35-1.20 (m,
20H), 0.90 (t, J = 6.6 Hz, 6H); 13C NMR (CDCl3): ¤ 148.0, 137.3,
131.6, 129.6, 127.8, 127.4, 124.0, 122.2, 119.9, 111.6, 51.0, 31.8,
29.5, 29.3, 27.3, 27.2, 22.6, 14.1.
Figure 2. One-photon fluorescence spectra of 1, 5, 6, and
13 in CHCl3 at 1 © 10¹6 M.
To
a mixture of trans-4-bromo-4¤-(dioctylamino)stilbene
(7.50 g, 15.0 mmol), PdCl2(PPh3)2 (95 mg, 0.23 mmol), CuI (43
mg, 0.45 mmol), and PPh3 (118 mg, 0.45 mmol) under an argon
atmosphere were added Et3N (40 mL), THF (40 mL), and tri-
methylsilylacetylene (3.4 mL, 24 mmol). The resulting mixture
was stirred at 50 °C for 15 h. After evaporation of Et3N, the residue
was triturated with CHCl3 and filtered. The filtrate was partitioned
between CHCl3 and H2O. The organic layer was washed with H2O
and brine and dried over Na2SO4. After evaporation of solvent, the
residue was subjected to column chromatography on silica gel
eluted with hexane-CHCl3 (5:1) to give trans-4-dioctylamino-4¤-
(trimethylsilylethynyl)stilbene (7.41 g, 96% yield). Yellow solid;
mp <40 °C; 1H NMR (CDCl3): ¤ 7.43 (d, J = 8.7 Hz, 2H), 7.39 (d,
J = 8.7 Hz, 2H), 7.38 (d, J = 8.8 Hz, 2H), 7.06 (d, J = 16.2 Hz,
1H), 6.84 (d, J = 16.2 Hz, 1H), 6.62 (d, J = 8.8 Hz, 2H), 3.29 (t,
J = 7.6 Hz, 4H), 1.60-1.56 (m, 4H), 1.33-1.31 (m, 20H), 0.92 (t,
J = 6.6 Hz, 6H), 0.27 (s, 9H); 13C NMR (CDCl3): ¤ 148.0, 138.6,
132.1, 129.9, 127.9, 125.6, 124.1, 122.7, 120.7, 111.5, 105.6, 94.3,
51.0, 31.8, 29.5, 29.3, 27.3, 27.2, 22.6, 14.1, 0.20.
Figure 3. One-photon fluorescence spectra of
5 (1 ©
10¹6 M) in (a) hexane, (b) toluene, (c) CHCl3, (d) THF,
and (e) CH2Cl2.
To a mixture of trans-4-dioctylamino-4¤-(trimethylsilylethynyl)-
stilbene (7.41 g, 14.4 mmol) and K2CO3 (1.98 g, 14.4 mmol) were
added MeOH (50 mL) and THF (100 mL). The resulting mixture
was stirred for 1 h at room temperature, and then filtered. After
evaporation of the filtrate, the residue was partitioned between
CHCl3 and H2O. The organic layer was washed with H2O and
brine and dried over Na2SO4. After evaporation of solvent, the
residue was recrystallized from EtOH to give 15 (5.24 g, 82%
yield). Pale yellow solid; mp <40 °C; 1H NMR (CDCl3): ¤
7.46-7.40 (m, 4H), 7.38 (d, J = 8.9 Hz, 2H), 7.06 (d, J = 16.2 Hz,
1H), 6.65 (d, J = 16.2 Hz, 1H), 6.63 (d, J = 8.5 Hz, 2H), 3.29 (t,
J = 7.6 Hz, 4H), 3.12 (s, 1H), 1.65-1.55 (m, 4H), 1.33-1.30 (m,
20H), 0.90 (t, J = 6.1 Hz, 6H); 13C NMR (CDCl3): ¤ 148.0, 139.0,
132.3, 130.2, 128.0, 125.7, 124.0, 122.6, 120.7, 111.5, 84.1, 77.3,
51.0, 31.8, 29.5, 29.3, 27.3, 27.2, 22.6, 14.1.
4-( p-Octylstyryl)phenylacetylene (16): When p-octylbenz-
aldehyde was used under similar conditions, 16 was obtained
in overall 58% yield. Pale yellow solid; mp 140 °C; 1H NMR
(CDCl3): ¤ 7.51-7.43 (m, 4H), 7.44 (d, J = 8.1 Hz, 2H), 7.19 (d,
J = 8.1 Hz, 2H), 7.13 (d, J = 16.3 Hz, 1H), 7.04 (d, J = 16.3 Hz,
1H), 3.14 (s, 1H), 2.63 (t, J = 7.7 Hz, 2H), 1.66-1.61 (m, 2H),
1.33-1.29 (m, 10H), 0.90 (t, J = 6.7 Hz, 3H); 13C NMR (CDCl3): ¤
143.1, 138.1, 134.4, 132.4, 129.9, 128.8, 126.8, 126.6, 126.2,
120.8, 83.8, 77.7, 35.8, 31.9, 31.4, 29.5, 29.31, 29.25, 22.7, 14.1.
Figure 4. Power density dependence of transmittance of
5 (1 © 10¹4 M) in toluene. The line is curve fitted by
Ti = {ln(1 + I0L¢)}/I0L¢.21
120H), 0.92 (t, J = 7.0 Hz, 36H); 13C NMR (CDCl3): ¤ 148.0,
133.2, 126.2, 111.2, 109.9, 99.7, 86.8, 51.0, 31.8, 29.5, 29.3, 27.3,
27.2, 22.7, 14.1. Anal. Calcd for C150H228N6: C, 85.16; H, 10.86;
N, 3.97%. Found: C, 84.95; H, 10.98; N, 3.88%.
Typical Procedure for the Synthesis of 4-( p-Substituted-
styryl)phenylacetylenes: 4-( p-Dioctylaminostyryl)phenylacety-

1422 Bull. Chem. Soc. Jpn. Vol. 82, No. 11 (2009)
Starburst-Type ³-Conjugated Molecules
4-[ p-Bis( p-octylphenyl)aminostyryl]phenylacetylene (17):
When p-bis(p-octylphenyl)aminobenzaldehyde was used under
similar conditions, 17 was obtained in overall 42% yield. Yellow
viscous oil; 1H NMR (CDCl3): ¤ 7.47 (d, J = 8.5 Hz, 2H), 7.43 (d,
J = 8.5 Hz, 2H), 7.35 (d, J = 8.7 Hz, 2H), 7.10-6.99 (m, 11H),
6.93 (d, J = 16.3 Hz, 1H), 3.12 (s, 1H), 2.57 (t, J = 7.7 Hz, 4H),
1.64-1.59 (m, 4H), 1.33-1.29 (m, 20H), 0.90 (t, J = 6.7 Hz, 6H);
13C NMR (CDCl3): ¤ 148.2, 145.0, 138.3, 138.0, 132.4, 130.0,
129.6, 129.2, 127.4, 126.0, 125.4, 124.7, 122.2, 120.4, 83.9, 77.7,
35.4, 31.9, 31.5, 29.5, 29.4, 29.3, 22.7, 14.1.
4-( p-Nitrostyryl)phenylacetylene (21): When p-nitrobenz-
aldehyde was used under similar conditions, 21 was obtained
in overall 69% yield. Yellow solid; mp 210-212 °C; 1H NMR
(CDCl3): ¤ 8.24 (d, J = 8.8 Hz, 2H), 7.64 (d, J = 8.8 Hz, 2H), 7.52
(s-like, 4H), 7.25 (d, J = 16.3 Hz, 1H), 7.16 (d, J = 16.3 Hz, 1H),
3.19 (s, 1H); 13C NMR (CDCl3): ¤ 146.9, 143.4, 136.6, 132.6,
127.4, 127.0, 126.8, 126.6, 124.1, 122.3, 83.4, 78.7.
12H), 7.12 (d, J = 16.2 Hz, 6H), 6.90 (d, J = 16.2 Hz, 6H), 6.64
(d, J = 8.7 Hz, 12H), 3.30 (t, J = 7.4 Hz, 24H), 1.62-1.56 (m,
24H), 1.34-1.31 (m, 120H), 0.91 (t, J = 6.6 Hz, 36H); 13C NMR
(CDCl3): ¤ 148.0, 138.8, 132.2, 130.0, 128.1, 127.2, 125.9, 124.3,
123.0, 121.1, 111.6, 99.9, 88.5, 51.1, 31.9, 29.5, 29.4, 27.4, 27.2,
22.7, 14.1. Anal. Calcd for C198H264N6: C, 87.17; H, 9.75; N,
3.08%. Found: C, 87.07; H, 9.72; N, 2.97%.
Hexakis[4-( p-octylstyryl)phenylethynyl]benzene (6): When
16 was used under similar conditions, 6 was obtained in 30%
yield. Yellow solid; mp 140 °C; 1H NMR (CDCl3): ¤ 7.38 (d,
J = 8.2 Hz, 12H), 7.34 (d, J = 8.2 Hz, 12H), 7.22 (d, J = 8.3 Hz,
12H), 7.07 (d, J = 8.1 Hz, 12H), 7.01 (d, J = 16.3 Hz, 6H), 6.92
(d, J = 16.3 Hz, 6H), 2.60 (t, J = 7.7 Hz, 12H), 1.64-1.60 (m,
12H), 1.36-1.27 (m, 60H), 0.93 (t, J = 6.6 Hz, 18H); 13C NMR
(CDCl3): ¤ 142.6, 137.1, 134.6, 132.3, 129.0, 128.7, 127.3, 126.7,
126.3, 126.2, 122.7, 99.3, 89.3, 35.9, 32.0, 31.5, 29.6, 29.4, 22.7,
14.1. Anal. Calcd for C150H162: C, 91.69; H, 8.31%. Found: C,
91.43; H, 8.49%.
4-[ p-(1,3-Dioxolan-2-yl)styryl]phenylacetylene (22): When
p-(1,3-dioxolan-2-yl)benzaldehyde was used under similar con-
ditions, 22 was obtained in overall 65% yield. Yellow solid; mp
Hexakis{4-[p-bis( p-octylphenyl)aminostyryl]phenylethynyl}-
benzene (13): When 17 was used under similar conditions, 13
1
1
176-179 °C; H NMR (CDCl3): ¤ 7.54 (d, J = 8.3 Hz, 2H), 7.51-
was obtained in 86% yield. Deep red solid; mp 75 °C; H NMR
7.45 (m, 6H), 7.15 (d, J = 16.4 Hz, 1H), 7.09 (d, J = 16.4 Hz, 1H),
5.84 (s, 1H), 4.18-4.11 (m, 2H), 4.10-4.03 (m, 2H), 3.14 (s, 1H);
13C NMR (CDCl3): ¤ 137.8, 137.6, 137.4, 132.4, 129.3, 128.3,
126.9, 126.6, 126.4, 121.1, 103.5, 83.7, 78.0, 65.3.
(CDCl3): ¤ 7.61 (d, J = 8.3 Hz, 12H), 7.48 (d, J = 8.3 Hz, 12H),
7.36 (d, J = 8.8 Hz, 12H), 7.13-6.95 (m, 72H), 2.58 (t, J = 7.7 Hz,
24H), 1.64-1.61 (m, 24H), 1.36-1.33 (m, 120H), 0.94 (t, J = 6.6
Hz, 36H); 13C NMR (CDCl3): ¤ 147.9, 145.1, 137.9, 137.7, 132.3,
130.2, 129.1, 127.5, 127.2, 126.2, 125.8, 124.7, 123.0, 122.4,
122.0, 99.6, 88.9, 35.4, 31.9, 31.6, 31.4, 29.5, 29.3, 22.7, 14.1.
Anal. Calcd for C270H312N6: C, 89.06; H, 8.64; N, 2.31%. Found:
C, 89.24; H, 8.80; N, 2.17%.
The Sonogashira Coupling Reaction of 1,3,5-Tribromo-
2,4,6-triiodobenzene with 15. To a mixture of 1,3,5-tribromo-
2,4,6-triiodobenzene15 (1.56 g, 2.25 mmol), 15 (4.00 g, 9.01 mmol;
4.0 equiv), PdCl2(PPh3)2 (31.6 mg, 0.045 mmol), CuI (17.2 mg,
0.090 mmol), and PPh3 (23.6 mg, 0.090 mmol) under an argon
atmosphere was added Et3N (80 mL). The resulting mixture was
stirred at refluxing temperature for 48 h. After evaporation of Et3N,
the residue was triturated with CHCl3 and filtered. The filtrate was
partitioned between CHCl3 and H2O. The organic layer was
washed with H2O and brine and dried over Na2SO4. After
evaporation of solvent, the residue was subjected to column
chromatography on Al2O3 eluted with hexane-CHCl3 (2.5:1)
followed by recycle preparative GPC to give 18 (1.08 g, 25%
yield), 19 (1.89 g, 42% yield), and 20 (0.31 g, 6% yield).
1,3,5-Tris( p-dioctylaminophenylethynyl)-2,4,6-tris[4-( p-octyl-
styryl)phenylethynyl]benzene (4).
To a mixture of 1,3,5-
tribromo-2,4,6-tris(p-dioctylaminophenylethynyl)benzene15 (46.8
mg, 0.035 mmol), 16 (100 mg, 0.32 mmol), PdCl2(PPh3)2 (2.2 mg,
0.003 mmol), CuI (1.2 mg, 0.006 mmol), and PPh3 (1.7 mg, 0.006
mmol) under an argon atmosphere was added Et3N (10 mL). The
resulting mixture was stirred at 70 °C for 20 h. After evaporation of
Et3N, the residue was triturated with CHCl3 and filtered. After
evaporation of the filtrate, the residue was subjected to column
chromatography on silica gel eluted with hexane-CHCl3 (2:1) and
then hexane-EtOAc (5:1) followed by recycle preparative GPC to
1
give 4 (33.7 mg, 47% yield). Red solid; mp 117-121 °C; H NMR
(CDCl3): ¤ 7.68 (d, J = 8.3 Hz, 6H), 7.53 (d, J = 8.3 Hz, 6H), 7.51
(d, J = 8.9 Hz, 6H), 7.49 (d, J = 8.2 Hz, 6H), 7.20 (d, J = 8.2 Hz,
6H), 7.17 (d, J = 16.3 Hz, 3H), 7.09 (d, J = 16.3 Hz, 3H), 6.61 (d,
J = 8.9 Hz, 6H), 3.32 (t, J = 7.9 Hz, 12H), 2.63 (t, J = 7.9 Hz,
6H), 1.64-1.56 (m, 18H), 1.35-1.30 (m, 90H), 0.92-0.87 (m,
27H); 13C NMR (CDCl3): ¤ 148.4, 143.0, 137.5, 134.6, 133.3,
132.2, 129.5, 128.8, 128.4, 127.2, 126.5, 126.3, 125.0, 122.7,
111.3, 108.9, 101.5, 98.2, 89.3, 86.3, 51.0, 35.8, 31.9, 31.8,
31.4, 29.5, 29.33, 29.26, 27.3, 27.2, 22.7, 14.1. Anal. Calcd for
When 3.0 equiv of 15 was used under the same conditions, 18
and 19 were obtained in 48% and 14% yields, respectively.
1,3,5-Tribromo-2,4,6-tris[4-( p-dioctylaminostyryl)phenyleth-
1
C
150H195N3: C, 88.31; H, 9.63; N, 2.06%. Found: C, 88.06; H,
ynyl]benzene (18): Red solid; mp <40 °C; H NMR (CDCl3):
9.82; N, 1.92%.
¤ 7.60 (d, J = 8.3 Hz, 6H), 7.48 (d, J = 8.3 Hz, 6H), 7.40 (d,
J = 8.8 Hz, 6H), 7.11 (d, J = 16.1 Hz, 3H), 6.88 (d, J = 16.1 Hz,
3H), 6.63 (d, J = 8.8 Hz, 6H), 3.30 (t, J = 7.5 Hz, 12H), 1.61-1.56
(m, 12H), 1.34-1.31 (m, 60H), 0.92 (t, J = 6.7 Hz, 18H); 13C NMR
(CDCl3): ¤ 148.1, 139.5, 132.1, 130.5, 128.1, 127.8, 127.6, 125.9,
124.1, 123.0, 119.9, 111.6, 100.1, 88.6, 51.1, 31.9, 29.5, 29.4,
27.4, 27.2, 22.7, 14.1. Anal. Calcd for C102H132Br3N3: C, 74.71; H,
8.11; N, 2.56%. Found: C, 74.42; H, 7.92; N, 2.33%.
1,3-Dibromo-2,4,5,6-tetrakis[4-( p-dioctylaminostyryl)phenyl-
ethynyl]benzene (19): Deep red solid; mp <40 °C; 1H NMR
(CDCl3): ¤ 7.63-7.56 (m, 8H), 7.50-7.41 (m, 16H), 7.13 (d,
J = 16.1 Hz, 3H), 7.11 (d, J = 16.1 Hz, 1H), 6.91 (d, J = 16.1 Hz,
3H), 6.89 (d, J = 16.1 Hz, 1H), 6.65 (d, J = 8.6 Hz, 8H), 3.31 (t,
J = 7.3 Hz, 16H), 1.63 (m, 16H), 1.36-1.33 (m, 80H), 0.94 (t,
J = 6.5 Hz, 24H); 13C NMR (CDCl3): ¤ 148.0, 139.3, 139.2, 139.1,
Typical Procedure for the Synthesis of Hexakis[4-( p-sub-
stituted-styryl)phenylethynyl]benzenes with D6h Symmetry:
Hexakis[4-( p-dioctylaminostyryl)phenylethynyl]benzene (5).
To a mixture of hexabromobenzene (168.4 mg, 0.305 mmol), 15
(1.64 g, 3.70 mmol), PdCl2(PPh3)2 (15.0 mg, 0.021 mmol), CuI
(8.1 mg, 0.043 mmol), and PPh3 (11.2 mg, 0.043 mmol) under an
argon atmosphere was added Et3N (25 mL). The resulting mixture
was stirred at refluxing temperature for 45 h. After evaporation of
Et3N, the residue was triturated with hexane and filtered. After
evaporation of the filtrate, the residue was subjected to column
chromatography on Al2O3 eluted with hexane-CHCl3 (2:1)
followed by recycle preparative GPC to give 5 (567 mg, 68%
yield). Deep red solid; mp 93-96 °C; 1H NMR (CDCl3): ¤ 7.61 (d,
J = 8.3 Hz, 12H), 7.47 (d, J = 8.3 Hz, 12H), 7.42 (d, J = 8.7 Hz,

K. Kobayashi et al.
Bull. Chem. Soc. Jpn. Vol. 82, No. 11 (2009) 1423
132.1, 130.3, 130.2, 128.4, 128.0, 127.6, 127.4, 125.9, 125.8,
124.5, 124.2, 122.7, 120.5, 120.1, 111.6, 101.2, 100.6, 99.9, 89.2,
88.4, 88.1, 51.0, 31.8, 29.8, 29.7, 29.5, 29.3, 27.3, 27.2, 22.7, 14.1.
Anal. Calcd for C134H176Br2N4: C, 80.36; H, 8.86; N, 2.80%.
Found: C, 80.10; H, 8.81; N, 2.65%.
1-Bromo-2,3,4,5,6-pentakis[4-( p-dioctylaminostyryl)phenyl-
ethynyl]benzene (20): Deep red solid; mp <40 °C; 1H NMR
(CDCl3): ¤ 7.61 (t, J = 8.8 Hz, 10H), 7.51-7.48 (m, 10H), 7.41 (d,
J = 8.8 Hz, 10H), 7.10 (d, J = 15.7 Hz, 5H), 6.89 (d, J = 15.7 Hz,
5H), 6.63 (d, J = 8.8 Hz, 10H), 3.29 (t, J = 7.6 Hz, 20H), 1.61 (m,
20H), 1.34-1.31 (m, 100H), 0.90 (t, J = 6.8 Hz, 30H); 13C NMR
(CDCl3): ¤ 147.9, 138.9, 138.8, 138.7, 132.4, 132.20, 132.18,
130.0, 129.9, 128.1, 127.7, 127.3, 127.2, 127.1, 125.9, 125.8,
124.3, 122.9, 121.1, 121.0, 120.8, 111.6, 100.4, 100.2, 99.2, 88.9,
88.6, 88.0, 51.1, 31.8, 31.7, 29.5, 29.3, 29.2, 27.4, 27.2, 22.6, 22.5,
14.1. Anal. Calcd for C166H220BrN5: C, 84.29; H, 9.37; N, 2.96%.
Found: C, 84.11; H, 9.55; N, 3.07%.
C
182H230N6O2: C, 86.27; H, 9.15; N, 3.32%. Found: C, 86.22; H,
9.38; N, 3.19%.
1,3,5-Tris[4-( p-dioctylaminostyryl)phenylethynyl]-2,4,6-tris-
{4-[ p-(1,3-dioxolan-2-yl)styryl]phenylethynyl}benzene
(23).
To a mixture of 18 (819 mg, 0.499 mmol), 22 (621 mg, 2.25 mmol),
PdCl2(PPh3)2 (35.0 mg, 0.045 mmol), CuI (19.0 mg, 0.100 mmol),
and PPh3 (26.2 mg, 0.100 mmol) under an argon atmosphere was
added Et3N (100 mL). The resulting mixture was stirred at
refluxing temperature for 42 h. After evaporation of Et3N, the
residue was triturated with CHCl3 and filtered. After evaporation of
the filtrate, the residue was subjected to column chromatography
on silica gel eluted with hexane-CHCl3 (1:7) followed by recycle
preparative GPC to give 23 (656 mg, 59% yield). Deep red solid;
1
mp 130 °C; H NMR (CDCl3): ¤ 7.60-7.52 (m, 18H), 7.48-7.38
(m, 24H), 7.17 (d, J = 16.1 Hz, 3H), 7.11 (d, J = 16.1 Hz, 3H),
7.09 (d, J = 16.1 Hz, 3H), 6.88 (d, J = 16.1 Hz, 3H), 6.62 (d,
J = 8.8 Hz, 6H), 5.84 (s, 3H), 4.18-4.12 (m, 6H), 4.11-4.07 (m,
6H), 3.30 (t, J = 7.6 Hz, 12H), 1.61-1.57 (m, 12H), 1.35-1.30
(m, 60H), 0.91 (t, J = 6.8 Hz, 18H); 13C NMR (CDCl3): ¤ 148.0,
138.7, 138.1, 137.23, 137.17, 132.3, 132.2, 129.9, 128.9, 128.7,
128.1, 127.5, 127.0, 126.9, 126.7, 126.5, 125.8, 124.2, 123.0,
122.8, 121.2, 111.6, 103.6, 100.0, 99.3, 89.1, 88.6, 65.3, 51.0,
31.9, 29.5, 29.4, 27.4, 27.2, 22.7, 14.1. Anal. Calcd for
1,3,5-Tris[4-( p-dioctylaminostyryl)phenylethynyl]-2,4,6-tris-
[4-( p-nitrostyryl)phenylethynyl]benzene (9). To a mixture of
18 (561 mg, 0.342 mmol), 21 (511 mg, 2.05 mmol), PdCl2(PPh3)2
(24.0 mg, 0.034 mmol), CuI (13.6 mg, 0.068 mmol), and PPh3
(17.9 mg, 0.068 mmol) under an argon atmosphere were added
Et3N (15 mL) and THF (50 mL). The resulting mixture was stirred
at 70 °C for 23 h. After evaporation of solvents, the residue was
triturated with CHCl3 and filtered. After evaporation of the filtrate,
the residue was subjected to column chromatography on Al2O3
eluted with hexane-CHCl3 (2:1) followed by recycle preparative
GPC to give 9 (288 mg, 39% yield). Deep red solid; mp 190 °C;
1H NMR (CDCl3): ¤ 7.84 (d, J = 8.2 Hz, 6H), 7.22-7.07 (m, 30H),
6.96 (d, J = 7.7 Hz, 6H), 6.87-6.68 (m, 9H), 6.55 (d, J = 16.1 Hz,
3H), 6.42 (d, J = 8.4 Hz, 6H), 3.27-3.15 (m, 12H), 1.62-1.48 (m,
12H), 1.39-1.26 (m, 60H), 0.92 (t, J = 6.6 Hz, 18H); 13C NMR
(CDCl3): ¤ 148.1, 146.3, 143.3, 137.8, 135.2, 132.5, 132.2, 132.1,
129.3, 127.9, 127.5, 126.7, 126.6, 126.1, 125.4, 124.3, 123.9,
123.5, 122.5, 121.7, 111.3, 99.3, 98.7, 90.1, 89.0, 50.8, 31.9, 29.5,
29.4, 29.3, 27.1, 22.7, 14.1. Anal. Calcd for C150H162N6O6: C,
83.99; H, 7.61; N, 3.92%. Found: C, 83.78; H, 7.87; N, 4.11%.
1,2,3,5-Tetrakis[4-( p-dioctylaminostyryl)phenylethynyl]-4,6-
bis[4-( p-nitrostyryl)phenylethynyl]benzene (8): The reaction
of 19 with 6 equiv of 21 under the same conditions gave 8 in 52%
C
159H177N3O6: C, 85.79; H, 8.01; N, 1.89%. Found: C, 85.53;
H, 8.29; N, 1.64%.
1,2,3,5-Tetrakis[4-( p-dioctylaminostyryl)phenylethynyl]-4,6-
tris{4-[ p-(1,3-dioxolan-2-yl)styryl]phenylethynyl}benzene (25):
The reaction of 19 with 4 equiv of 22 under the same condi-
1
tions gave 25 in 72% yield. Deep red solid; mp 80 °C; H NMR
(CDCl3): ¤ 7.65-7.51 (m, 32H), 7.41 (d, J = 8.2 Hz, 8H), 7.20 (d,
J = 16.1 Hz, 2H), 7.15 (d, J = 16.1 Hz, 2H), 7.12 (d, J = 16.1 Hz,
4H), 6.90 (d, J = 16.1 Hz, 4H), 6.63 (d, J = 8.8 Hz, 8H), 5.85 (s,
2H), 4.18-4.12 (m, 4H), 4.11-4.05 (m, 4H), 3.30 (t, J = 7.6 Hz,
16H), 1.63-1.53 (m, 16H), 1.34-1.30 (m, 80H), 0.91 (t, J = 6.8
Hz, 24H); 13C NMR (CDCl3): ¤ 147.9, 138.4, 138.1, 137.1, 136.9,
132.3, 129.7, 128.8, 128.6, 128.1, 127.4, 127.3, 126.9, 126.8,
126.7, 126.4, 125.8, 124.4, 123.1, 123.0, 121.4, 111.6, 103.6, 99.8,
99.2, 89.3, 88.8, 65.2, 51.0, 31.9, 29.5, 29.4, 27.4, 27.2, 22.7, 14.1.
Anal. Calcd for C172H206N4O4: C, 86.31; H, 8.67; N, 2.34%.
Found: C, 86.36; H, 8.96; N, 2.55%.
1,3,5-Tris[4-( p-dioctylaminostyryl)phenylethynyl]-2,4,6-tris-
[4-( p-formylstyryl)phenylethynyl]benzene (24). To a solution
of 23 (530 mg, 0.238 mmol) in THF (20 mL) under an argon
atmosphere was added 1 M HCl (2.8 mL). After being stirred at
room temperature for 17 h, the reaction mixture was neutralized
with aqueous Na2CO3 and extracted with CH2Cl2. The organic
layer was washed with H2O and brine and dried over Na2SO4.
After evaporation of solvents, the residue was subjected to column
chromatography on Al2O3 eluted with CH2Cl2 followed by recycle
preparative GPC to give 24 (338 mg, 68% yield). Deep red solid;
1
yield. Deep red solid; mp 165 °C; H NMR (CDCl3): ¤ 7.92 (d,
J = 8.6 Hz, 4H), 7.39-7.16 (m, 32H), 7.08 (d, J = 8.2 Hz, 4H),
6.99-6.47 (m, 20H), 3.28-3.22 (m, 16H), 1.62 (m, 16H), 1.36-
1.33 (m, 80H), 0.96-0.92 (m, 24H); 13C NMR (CDCl3): ¤ 147.9,
147.8, 146.2, 143.5, 137.8, 135.1, 132.7, 132.3, 129.3, 128.0,
127.5, 127.4, 127.0, 126.8, 126.7, 126.6, 125.9, 125.6, 124.4,
124.2, 124.1, 123.8, 123.0, 121.8, 111.5, 99.6, 99.4, 99.3, 98.7,
90.2, 89.2, 88.9, 50.9, 31.9, 29.6, 29.5, 29.4, 29.3, 27.4, 27.20,
27.15, 22.7, 14.1. Anal. Calcd for C166H196N6O4: C, 85.23; H,
8.44; N, 3.59%. Found: C, 85.05; H, 8.72; N, 3.82%.
1,2,3,4,5-Pentakis[4-( p-dioctylaminostyryl)phenylethynyl]-
6-[4-( p-nitrostyryl)phenylethynyl]benzene (7): The reaction of
20 with 3 equiv of 21 under the same conditions gave 7 in 54%
yield. Deep red solid; mp 117 °C; 1H NMR (CDCl3): ¤ 8.11 (d, J =
8.3 Hz, 2H), 7.56-7.52 (m, 14H), 7.41-7.39 (m, 22H), 7.18 (d,
J = 16.6 Hz, 1H), 7.11-7.05 (m, 6H), 6.91-6.84 (m, 5H), 6.62-
6.60 (m, 10H), 3.35-3.25 (m, 20H), 1.67-1.55 (m, 20H), 1.39-
1.26 (m, 100H), 0.92 (t, J = 6.8 Hz, 30H); 13C NMR (CDCl3): ¤
147.9, 146.5, 143.7, 138.4, 135.8, 132.8, 132.34, 132.30, 129.8,
129.7, 128.1, 127.3, 127.2, 126.93, 126.87, 126.5, 125.8, 124.3,
124.1, 124.0, 123.1, 121.5, 111.7, 99.8, 98.9, 88.9, 88.85, 88.79,
51.0, 31.9, 29.5, 29.4, 27.4, 27.2, 22.7, 14.1. Anal. Calcd for
1
mp 216-219 °C; H NMR (CDCl3): ¤ 9.89 (s, 3H), 7.71 (d, J =
8.3 Hz, 6H), 7.52-7.43 (m, 18H), 7.31-7.28 (m, 18H), 7.09 (d,
J = 16.1 Hz, 3H), 7.01-6.96 (m, 6H), 6.76 (d, J = 16.1 Hz, 3H),
6.55 (d, J = 8.8 Hz, 6H), 3.27 (t, J = 7.6 Hz, 12H), 1.64-1.55 (m,
12H), 1.40-1.28 (m, 60H), 0.92 (t, J = 6.8 Hz, 18H); 13C NMR
(CDCl3): ¤ 191.3, 148.0, 143.1, 138.2, 135.9, 135.1, 132.3, 131.6,
130.1, 129.5, 128.1, 127.6, 127.4, 126.95, 126.89, 126.7, 125.7,
124.0, 123.8, 122.9, 121.6, 111.5, 99.7, 98.9, 89.9, 88.9, 51.0,
31.9, 29.5, 29.4, 27.4, 27.2, 22.7, 14.1.
1,2,3,5-Tris[4-( p-dioctylaminostyryl)phenylethynyl]-4,6-tris-
[4-( p-formylstyryl)phenylethynyl]benzene (26): The hydroly-
sis of 25 under the same conditions gave 26 in 80% yield. Deep red

1424 Bull. Chem. Soc. Jpn. Vol. 82, No. 11 (2009)
Starburst-Type ³-Conjugated Molecules
solid; mp 140-142; 1H NMR (CDCl3): ¤ 9.93 (s, 2H), 7.77 (d,
J = 8.3 Hz, 4H), 7.57-7.46 (m, 16H), 7.38-7.34 (m, 20H), 7.16 (d,
J = 16.1 Hz, 2H), 7.08-7.00 (m, 6H), 6.85 (d, J = 16.1 Hz, 3H),
6.82 (d, J = 16.1 Hz, 1H), 6.61-6.57 (m, 8H), 3.30 (t, J = 7.3 Hz,
16H), 1.64-1.55 (m, 16H), 1.35-1.31 (m, 80H), 0.92 (t, J = 6.8
Hz, 24H); 13C NMR (CDCl3): ¤ 191.4, 147.9, 143.2, 138.3, 136.1,
135.1, 132.34, 132.30, 131.7, 130.2, 129.7, 128.1, 127.5, 127.2,
127.0, 126.9, 126.8, 125.8, 124.3, 123.8, 123.0, 122.8, 121.5,
111.6, 99.8, 99.7, 99.0, 89.8, 88.9, 51.0, 31.9, 29.6, 29.4, 27.4,
27.2, 22.7, 14.1.
drops of H2O. The resulting mixture was stirred at refluxing
temperature for 16 h. After evaporation of solvents, the residue was
triturated with hexane and filtered through celite. After evaporation
of the filtrate, the residue was reprecipitated with hexane-EtOH to
give 27 (1.32 g, 55% yield). White solid; mp 164 °C; 1H NMR
(CDCl3): ¤ 0.31 (s, 18H); 13C NMR (CDCl3): ¤ 128.9, 128.0,
108.3, 102.9, ¹0.4.
1,2,4,5-Tetrakis[4-( p-dioctylaminostyryl)phenylethynyl]-3,6-
bis(trimethylsilylethynyl)benzene (28).
To a mixture of 27
(113 mg, 0.193 mmol), 15 (600 mg, 1.35 mmol), PdCl2(PPh3)2
(13.6 mg, 0.019 mmol), CuI (7.4 mg, 0.039 mmol), and PPh3
(10.1 mg, 0.039 mmol) under an argon atmosphere was added
Et3N (15 mL). The resulting mixture was stirred at refluxing
temperature for 24 h. After evaporation of Et3N, the residue was
triturated with CH2Cl2 and filtered. After evaporation of the filtrate,
the residue was subjected to column chromatography on Al2O3
eluted with CH2Cl2 followed by recycle preparative GPC to give
28 (265 mg, 67% yield). Red solid; mp 150 °C; 1H NMR (CDCl3):
¤ 7.60 (d, J = 8.3 Hz, 8H), 7.50 (d, J = 8.3 Hz, 8H), 7.42 (d,
J = 8.8 Hz, 8H), 7.13 (d, J = 16.1 Hz, 4H), 6.90 (d, J = 16.1 Hz,
4H), 6.64 (d, J = 8.8 Hz, 8H), 3.30 (t, J = 7.6 Hz, 16H), 1.66-1.55
(m, 16H), 1.39-1.27 (m, 80H), 0.91 (t, J = 6.6 Hz, 24H), 0.39 (s,
18H); 13C NMR (CDCl3): ¤ 148.0, 139.0, 132.1, 130.2, 128.0,
127.6, 127.0, 125.8, 124.1, 122.7, 120.8, 111.5, 104.9, 101.7, 99.9,
88.0, 51.1, 31.8, 29.5, 29.3, 27.3, 27.2, 22.7, 14.1, 0.1. Anal. Calcd
for C144H194N4Si2: C, 84.89; H, 9.60; N, 2.75%. Found: C, 85.16;
H, 9.84; N, 2.86%.
1,3,5-Tris{4-[ p-(2,2-dicyanoethenyl)styryl]phenylethynyl}-
2,4,6-tris[4-( p-dioctylaminostyryl)phenylethynyl]benzene (12).
To a solution of 24 (100.6 mg, 0.045 mmol) in CH2Cl2 (2 mL)
were added benzoic acid (1.1 mg, 0.009 mmol), Et3N (1.6 ¯L,
0.011 mmol), and malononitrile (38.8 mg, 0.587 mmol). The
resulting mixture was stirred at room temperature for 4 h. After
evaporation of solvents, the residue was subjected to column
chromatography on Al2O3 eluted with CH2Cl2 followed by recycle
preparative GPC to give 12 (89 mg, 88% yield). Deep red solid;
1
mp 195 °C; H NMR (CDCl3): ¤ 7.59 (d, J = 8.3 Hz, 6H), 7.37-
7.33 (m, 21H), 7.17-7.12 (m, 18H), 6.93 (d, J = 15.6 Hz, 3H),
6.79 (d, J = 16.1 Hz, 3H), 6.76 (d, J = 16.1 Hz, 3H), 6.60 (d,
J = 15.6 Hz, 3H), 6.48 (d, J = 8.3 Hz, 6H), 3.29-3.21 (m, 12H),
1.62-1.53 (m, 12H), 1.38-1.27 (m, 60H), 0.93 (t, J = 6.8 Hz,
18H); 13C NMR (CDCl3): ¤ 158.5, 148.1, 143.5, 138.3, 135.7,
132.4, 131.4, 129.8, 129.5, 128.2, 127.8, 127.3, 126.9, 126.8,
126.6, 125.8, 124.1, 122.6, 121.5, 114.3, 113.3, 111.6, 99.7, 98.9,
90.3, 89.1, 80.5, 51.0, 32.1, 29.7, 29.6, 27.5, 27.3, 22.9, 14.1.
Anal. Calcd for C162H165N9: C, 86.94; H, 7.43; N, 5.63%. Found:
C, 86.65; H, 7.70; N, 5.85%.
1,2,4,5-Tetrakis[4-( p-dioctylaminostyryl)phenylethynyl]-3,6-
diethynylbenzene (29).
To a solution of 28 (202 mg, 0.099
mmol) in THF (10 mL) at room temperature under an argon
atmosphere was added a THF solution of n-Bu4NF (1.0 M, 200 ¯L,
0.200 mmol). After being stirred at room temperature for 40 min,
the reaction mixture was partitioned between CH2Cl2 and H2O.
The organic layer was washed with H2O and brine and dried over
Na2SO4. After evaporation of solvents, the residue was subjected
to column chromatography on Al2O3 eluted with CH2Cl2 to give
29 (184 mg, 98% yield). Red solid; mp <40 °C; 1H NMR (CDCl3):
¤ 7.60 (d, J = 8.3 Hz, 8H), 7.49 (d, J = 8.3 Hz, 8H), 7.42 (d,
J = 8.8 Hz, 8H), 7.12 (d, J = 16.1 Hz, 4H), 6.90 (d, J = 16.1 Hz,
4H), 6.64 (d, J = 8.8 Hz, 8H), 3.79 (s, 2H), 3.30 (t, J = 6.8 Hz,
16H), 1.66-1.56 (m, 16H), 1.39-1.25 (m, 80H), 0.91 (t, J =
6.6 Hz, 24H); 13C NMR (CDCl3): ¤ 148.0, 139.1, 132.2, 130.2,
128.03, 127.99, 126.4, 125.8, 124.1, 122.8, 120.6, 111.6, 100.2,
87.7, 86.6, 80.6, 51.1, 31.8, 29.5, 29.3, 27.3, 27.2, 22.7, 14.1.
1,2,4,5-Tetrakis[4-( p-dioctylaminostyryl)phenylethynyl]-3,6-
bis[4-( p-nitrostyryl)phenylethynyl]benzene (10). To a mixture
of 29 (152 mg, 0.080 mmol), trans-4-bromo-4¤-nitrostilbene
(293 mg, 0.964 mmol), Pd(PPh3)4 (9.3 mg, 0.008 mmol), and CuI
(3.1 mg, 0.016 mmol) under an argon atmosphere were added Et3N
(6 mL) and THF (9 mL). The resulting mixture was stirred at 70 °C
for 44 h. After evaporation of solvents, the residue was triturated
with CH2Cl2 and filtered. After evaporation of the filtrate, the
residue was subjected to column chromatography on Al2O3 eluted
with CH2Cl2 followed by recycle preparative GPC to give 10
1,3-Bis{4-[ p-(2,2-dicyanoethenyl)styryl]phenylethynyl}-2,4,5,6-
tetrakis[4-( p-dioctylaminostyryl)phenylethynyl]benzene (11).
The reaction of 26 with 10 equiv of malononitrile under the same
conditions gave 11 in 86% yield. Deep red solid; mp 160 °C;
1H NMR (CDCl3): ¤ 7.64 (d, J = 8.3 Hz, 4H), 7.48-7.38 (m, 18H),
7.35-7.21 (m, 22H), 7.10-6.67 (m, 10H), 6.61-6.56 (m, 6H), 6.50
(d, J = 8.8 Hz, 2H), 3.29-3.21 (m, 16H), 1.68-1.57 (m, 16H),
1.35-1.31 (m, 80H), 0.94-0.91 (m, 24H); 13C NMR (CDCl3): ¤
158.4, 148.0, 147.8, 143.5, 138.3, 135.7, 132.6, 132.3, 131.4,
129.6, 128.1, 127.8, 127.4, 127.3, 126.92, 126.88, 126.7, 125.8,
124.2, 124.15, 124.10, 122.8, 121.4, 114.2, 113.1, 111.5, 99.6,
98.9, 90.0, 88.9, 88.7, 80.2, 51.0, 50.9, 31.9, 29.6, 29.4, 27.44,
27.39, 27.23, 27.19, 22.7, 14.1. Anal. Calcd for C174H198N8: C,
87.02; H, 8.31; N, 4.67%. Found: C, 86.81; H, 8.55; N, 4.63%.
1,2,4,5-Tetrabromo-3,6-bis(trimethylsilylethynyl)benzene
(27).16a
To a solution of trimethylsilylacetylene (1.6 mL,
12 mmol) in THF (20 mL) at ¹78 °C under an argon atmosphere
was added a hexane solution of n-BuLi (1.6 M, 6.8 mL, 11 mmol).
After being stirred at ¹78 °C for 30 min and then at 0 °C for
15 min, to the resulting solution of lithium trimethylsilylacetylide
at 0 °C was added a solution of p-bromanil (2.12 g, 5.00 mmol) in
THF (30 mL). After being stirred at room temperature for 16 h, the
reaction mixture was quenched with saturated NH4Cl and then
extracted with Et2O. The organic layer was washed with H2O and
brine and dried over Na2SO4. After evaporation of solvents, the
residue was subjected to column chromatography on silica gel
eluted with hexane-EtOAc (5:1 to 1:1) to give 2,3,5,6-tetrabromo-
1,4-bis(trimethylsilylethynyl)-2,5-cyclohexadiene-1,4-diol (2.47 g,
80% yield). 1H NMR (CDCl3): ¤ 3.25 (s, 2H), 0.21 (s, 18H);
13C NMR (CDCl3): ¤ 127.6, 101.2, 93.6, 71.9, ¹0.6.
1
(34 mg, 18% yield). Deep red solid; mp 70 °C; H NMR (CDCl3):
¤ 8.01 (d, J = 8.8 Hz, 4H), 7.44-7.38 (m, 16H), 7.33-7.29 (m,
16H), 7.23 (d, J = 8.3 Hz, 4H), 7.09 (d, J = 16.1 Hz, 2H), 6.99 (d,
J = 16.1 Hz, 4H), 6.96 (d, J = 16.1 Hz, 2H), 6.79 (d, J = 16.1 Hz,
4H), 6.56 (d, J = 8.8 Hz, 8H), 3.28 (t, J = 7.1 Hz, 16H), 1.65-1.54
(m, 16H), 1.38-1.26 (m, 80H), 0.92 (t, J = 6.6 Hz, 24H); 13C NMR
(CDCl3): ¤ 147.9, 146.4, 143.6, 138.1, 135.5, 132.7, 132.34,
132.30, 129.5, 128.1, 127.3, 127.0, 126.9, 126.8, 126.3, 125.7,
To a mixture of the diol (2.55 g, 4.11 mmol) and SnCl2¢2H2O
under an argon atmosphere were added CH3CN (30 mL) and two

K. Kobayashi et al.
Bull. Chem. Soc. Jpn. Vol. 82, No. 11 (2009) 1425
124.2, 124.1, 124.0, 123.0, 121.7, 111.5, 99.6, 98.8, 90.2, 89.0,
51.0, 31.9, 29.5, 29.4, 27.4, 27.2, 22.7, 14.1. Anal. Calcd for
10 a) S. K. Lee, W. J. Yang, J. J. Choi, C. H. Kim, S.-J. Jeon,
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J. Fu, L. A. Padilha, A. Biesso, J. M. Hales, X. Zhan, K. Schmidt,
A. Ye, E. Zojer, S. Barlow, D. J. Hagan, E. W. Van Stryland, Y. Yi,
Z. Shuai, G. A. Pagani, J.-L. Brédas, J. W. Perry, S. R. Marder,
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Swiatkiewicz, P. N. Prasad, J. Phys. Chem. B 1999, 103, 10741.
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C
166H196N6O4: C, 85.23; H, 8.44; N, 3.59%. Found: C, 84.98; H,
8.70; N, 3.41%.
Supporting Information
1H NMR spectra and one-photon absorption and fluorescence
spectra of 1-13, and two-photon absorption measurement. This
material is available free of charge on the Web at: http://
www.csj.jp/journals/bcsj/.
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25 Cf. R. Baker, R. J. Sims, Synthesis 1981, 117.