Synthesis and photophysical properties of five-membered ring π-conjugated materials based on bisthiazol-2-yl-amine and their metal complexation studies

Article abstract of DOI:10.1016/j.tet.2010.09.087

Poly(5,5′-(2-hexyldecyl)-bisthiazol-2-yl-amine) (PBTA) is prepared by nickel(0) mediated Yamamoto-type coupling. The photoluminescence (PL) spectrum of PBTA in THF solution displays pure blue emission with a peak centered at 444 nm without any shoulder peaks and the HOMO and LUMO values for PBTA are estimated to be 5.11 and 2.90 eV, respectively. In addition, we have synthesized a novel bisthiazol-2-yl-amine (BTA)-cored donor-acceptor (D-A) chromophore system, namely 5-(4-(diphenylamino)phenyl)-N-(5-(4-(diphenylamino)phenyl) thiazol-2-yl)-N-octylthiazol-2-amine (2-TPA-BTA) in which the electron-donating (D) moiety is triphenylamine group and the electron-withdrawing (A) unit is thiazole group. Furthermore, in this report, we present the complexation studies of both the BTA and 2-TPA-BTA chromophores with Cu(II) and Pd(II), respectively. The crystal structures are established by single-crystal X-ray diffraction analysis. These studies not only provide the general photophysical principles of the materials based on BTA moiety but also encourage progress toward realizing the full potential of its hybrid metal-organic frameworks.

Full text of DOI:10.1016/j.tet.2010.09.087

Tetrahedron 66 (2010) 9440e9444
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis and photophysical properties of five-membered ring
p-conjugated
materials based on bisthiazol-2-yl-amine and their metal complexation studies
*
Junghoon Lee, Jonggi Kim, Gyoungsik Kim, Changduk Yang
Interdisciplinary School of Green Energy, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, South Korea
a r t i c l e i n f o
a b s t r a c t
Poly(5,50-(2-hexyldecyl)-bisthiazol-2-yl-amine) (PBTA) is prepared by nickel(0) mediated Yamamoto-
type coupling. The photoluminescence (PL) spectrum of PBTA in THF solution displays pure blue
emission with a peak centered at 444 nm without any shoulder peaks and the HOMO and LUMO values
for PBTA are estimated to be 5.11 and 2.90 eV, respectively. In addition, we have synthesized a novel
bisthiazol-2-yl-amine (BTA)-cored donoreacceptor (DeA) chromophore system, namely 5-(4-(diphe-
nylamino)phenyl)-N-(5-(4-(diphenylamino)phenyl)thiazol-2-yl)-N-octylthiazol-2-amine (2-TPA-BTA) in
which the electron-donating (D) moiety is triphenylamine group and the electron-withdrawing (A) unit
is thiazole group. Furthermore, in this report, we present the complexation studies of both the BTA and
2-TPA-BTA chromophores with Cu(II) and Pd(II), respectively. The crystal structures are established by
single-crystal X-ray diffraction analysis. These studies not only provide the general photophysical prin-
ciples of the materials based on BTA moiety but also encourage progress toward realizing the full po-
tential of its hybrid metaleorganic frameworks.
Article history:
Received 27 August 2010
Received in revised form 27 September 2010
Accepted 27 September 2010
Available online 8 October 2010
Keywords:
Bisthiazol-2-yl-amine
Conjugated materials
Donoreacceptor molecules
Metal complexes
Polythiazoles
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
the synergistic effects between the two can enhance and induce
their outstanding properties. Although such a structural chromo-
A study of organic materials with delocalized
p
-electrons as
phore of two thiazole units bridged by a nitrogen atom, namely
bisthiazol-2-yl-amine (BTA) was prepared in 1956,25 to the best of
our knowledge, the structural properties as well as the metalation
have not been evaluated yet.
With the hope of clarifying the detailed properties and the po-
tential applications of BTA-based materials, herein we report the
synthesis and characterization of a semiconducting polymer, i.e.,
poly(5,50-(2-hexyldecyl)-bisthiazol-2-yl-amine) (PBTA) as well as
electronic semiconductors has blossomed into a mature field over
the last six decades.1 Considerable effort has been made for the
design and synthesis of functional
polymers whose electronic properties can be modulated with ex-
ternal stimuli.2e9 In this regard, five-membered ring
-conjugated
p-conjugated oligomers and
p
materials have especially attracted attention due to their potential
use as components for electronic applications.10e17 Among them,
thiazole containing the electron-withdrawing imine nitrogen in
place of the carbon atom at the 3-position of thiophene is an in-
a
p-conjugated donoreacceptor single molecule (5-(4-(diphenyl-
amino)phenyl)-N-(5-(4-(diphenylamino)phenyl)thiazol-2-yl)-N-
octylthiazol-2-amine, 2-TPA-BTA) containing electron-donating
triphenylamine and electron-accepting thiazole units (see Fig. 1).
Besides, features unique to BTA-cored metaleorganic hybrid mate-
rials, illustrating the changed coordination sites and geometries as
a function of the different metals, such as Cu(II) and Pd(II), are pre-
sented for usage in optical or electronic devices in the future.
teresting building block for
p-conjugated materials because of its
attractive properties such as stable n-doping and metal complex
forming ability.18e24
There exists another family of p-conjugated polymers in which
pz orbitals of nitrogen can contribute to the conjugation, such as
polyaniline (PANI) and polyazomethines. Such polymers show
distinctly different chemistry when compared to other well-known
p-conjugated systems, such as polyacetylene, poly-p-phenylene,
and polythiophene.
These points have attracted our attention to chemically combine
the thiazole unit and nitrogen atom in a single architecture so that
N
N
*
*
N
N
n
S
S
N
R
N
N
S
S
N
R
R:2-hexyldecyl
R: octyl
PBTA
2-TPA-BTA
Fig. 1. Molecular structure of PBTA and 2-TPA-BTA.
* Corresponding author. Tel.: þ82 52 217 2920; fax: þ82 52 217 2909; e-mail
address: yang@unist.ac.kr (C. Yang).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.09.087

J. Lee et al. / Tetrahedron 66 (2010) 9440e9444
9441
2. Results and discussion
2.3. Complexation studies
2.1. Poly(5,50-(2-hexyldecyl)-bisthiazol-2-yl-amine) (PBTA)
Conjugated metallooligomers consisting of metals or metal
clusters coordinated to multifunctional organic ligands not only
offer unprecedented levels of permanent porosity in the context of
crystalline materials but also lie at the forefront of contemporary
materials research because their modular nature combines nano-
scale porosity with enormous diversity of structure/property.35 Up
to now, tremendous progress has been made toward the de-
velopment of the conjugated metallooligomers, however novel
hybrid metaleorganic materials still need to realize their potential
as well as intrinsic properties.
The synthesis of material based on bisthiazole (poly(5,50-(2-
hexyldecyl)-bisthiazol-2-yl-amine), (PBTA)) was carried out as
depicted in Scheme 1. Bisthiazol-2-yl-amine (1, BTA) was synthe-
sized from chloroacetaldehyde and dithiobiuret in 60% isolated
yield.25 N-alkylation of 1 with 2-hexyl-1-decyl bromide generated
(2-hexyldecyl)-bisthiazol-2-yl-amine (2), which was brominated
using NBS to give bis-(5-bromo-thiazol-2-yl)-(2-hexyldecyl)-amine
(3). Poly(5,50-(2-hexyldecyl)-bisthiazol-2-yl-amine) (PBTA) was
prepared by Yamamoto-type polycondensation. PBTA has limited
solubility in common organic solvents (THF, toluene, chloroform,
etc.) due to the rigid nature of bisthiazole units in the main back-
bone. For the THF-soluble part, GPC analysis of PBTA exhibits a Mn
value of 5.7ꢀ103 g/mol with a polydispersity of 2.2 (THF, PS
standards).
BTA-based materials have the potential to bind transition-metal
ions, which can be used to tune their electronic, electrochemical,
and physical properties. Therefore, the coordination of metal cen-
ters directly to the BTA unit is undertaken. The reaction of BTA with
Cu(II) triflate gave a copper complex BTAeCu in THF solution at
room temperature (Scheme 2). It was difficult for BTAeCu to be
spectroscopically characterized by 1H NMR, 13C NMR or Field De-
sorption Mass Spectrometry (FD-MS). The NMR spectra of in-
organic compounds are often more complicated than simple
organics due to additional splitting from NMR active nuclei. It was
found that BTAeCu is paramagnetic, which was confirmed by
electron paramagnetic resonance (EPR) spectroscopy (see SI). X-ray
diffraction can provide the most unambiguous characterization of
such complexes. X-ray structural analysis of BTAeCu reveals two
BTA units complexed to a copper and a distorted tetrahedral ge-
ometry around the copper (Fig. 2 top). In further studies on com-
plexation behavior, Pd(II)Cl2(PhCN)2 was reacted with BTA and
a orange single crystal was obtained by slow diffusion of ether into
a N,N-dimethylformamide solution of the Pd(II) complex BTAePd
and analyzed by X-ray crystallography. In contrast, the resulting
data displays one BTA unit coordinated to one palladium and
a square-planar geometry around the palladium (the bottom of
Fig. 2). On the basis of our metal complex studies, a detailed in-
vestigation of various metals complexation on the polymer PBTA as
well as their conductivity in progress and will reported in a future
paper.
Scheme 1. Synthetic route to poly(5,50-(2-hexyldecyl)-bisthiazol-2-yl-amine) (PBTA)
and 5-(4-(diphenylamino)phenyl)-N-(5-(4-(diphenylamino)phenyl)thiazol-2-yl)-N-oc-
tylthiazol-2-amine (2-TPA-BTA).
2.2. BTA-cored pushepull architecture
Alternating donoreacceptor chain structures have allowed the
optical, redox, and electroluminescent properties to be tuned over
a wide range.26e33 To establish a new conjugated donoreacceptor
semiconductor based on BTA as the electron acceptor chromo-
phore, a straightforward synthesis toward BTA-cored pushepull
single skeleton is performed through the selection of triphenyl-
amine units as p-excessive building blocks.
Firstly, BTA was alkylated at nitrogen using 1-bromooctane
(yield¼95%) and subsequently brominated using NBS to give bis-
(5-bromo-thiazol-2-yl)-octyl-amine (4) as previously mentioned
(yield¼97%). 4-Bromo-triphenylamine was converted into 4-(4,4,5,5-
tetramethyl-1,3,2-dioxaborolan-2-yl)triphenylamine (5) by lithiation
and subsequent reaction with 2-isopropoxy-4,4,5,5-tetramethyl-
1,3,2-dioxaborolane. The synthesis of 5-(4-(diphenylamino)phenyl)-
N-(5-(4-(diphenylamino)phenyl)thiazol-2-yl)-N-octylthiazol-2-
amine (2-TPA-BTA) as the target donoreacceptor molecule by
using 4 and 5 was successful via Suzuki coupling34 under Pd
(PPh3)4/K2CO3 in isolated overall yield 30% (Scheme 1).
Scheme 2. Cu(II) and Pd(II) complexes with BTA and 2-TPA-BTA, respectively.
2.4. Photophysical properties
The UVevis absorption and photoluminescence (PL) spectra of
PBTA in dilute THF solution are shown in Fig. 3.The absorption of
PBTA has a distinct absorption band with a maximum at 390 nm

9442
J. Lee et al. / Tetrahedron 66 (2010) 9440e9444
BTA
1.0
0.8
0.6
0.4
0.2
0.0
BTA-Cu
BTA-Pd
350
400
450
Wavelength (nm)
Fig. 4. UVevis absorption spectra of BTA, BTAeCu, BTAePd, 2-TPA-BTA, 2-TPA-
BTAeCu, and 2-TPA-BTAePd in DMSO solution.
Fig. 2. X-ray crystal structure of (top) BTAeCu and (bottom) BTAePd. (a) top view (it is
colorized by elements) (b) side view and (c) packing projection. It is colorized by el-
ements, respectively. The solvents are omitted for clarity.
3. Conclusion
In efforts to develop five-member heterocyclic polymer based on
bisthiazole building block, poly(5,50-(2-hexyldecyl)-bisthiazol-2-yl-
amine) (PBTA) has been prepared by nickel(0) mediated Yamamoto-
type coupling. PBTA shows a pure blue emission maximum at
444 nm and its HOMO and LUMO levels are estimated to be 5.11 and
2.90 eV, respectively. The bisthiazol-2-yl-amine (BTA) unit has co-
ordination sites to bind metals, which allows us to study the prop-
erties of the metaleorganic hybrid materials and compare them
with the parent materials. Metal complexes with (Cu(II) and Pd(II))
are synthesized, which exhibits paramagnetic behavior. The crystal
structure of the Cu(II) complex BTAeCu with BTA comprises BTA and
copper in a 2:1 ratio with tetrahedral geometry around the copper
while the Pd(II) complex BTAePd displays a 1:1 ratio with square-
planar geometry. Besides, from the interesting donoreacceptor
1.0
0.8
0.6
0.4
0.2
0.0
1.0
0.8
0.6
0.4
0.2
0.0
300
400
500
600
700
Wavelength (nm)
concept,
5-(4-(diphenylamino)phenyl)-N-(5-(4-(diphenylamino)
phenyl)thiazol-2-yl)-N-octylthiazol-2-amine (2-TPA-BTA) compris-
ing thiazole representing n-type unit and triphenylamine repre-
senting p-type unit is prepared. This work marks the first attempt
has been made to use the conjugated metal hybrid strategy to build
conjugated material containing BTA units. These studies provide
a basis for understanding the photophysical properties of metal-
organic based BTA, which in turn will guide the design of new ma-
terials based on BTA that find application as the active materials in
electronic and photonic devices in the future.
Fig. 3. UVevis absorption and photoluminescence (lexc¼370 nm) of PBTA in THF
solution.
without any vibronic features. The PL spectrum of PBTA in solution
shows a blue emission region with a maximum at 444 nm and
a shoulder peak at 471 nm. The position of the emission maximum
is very close to that of a semiladder-type poly(pentaphenylene)
(445 nm),36,37 which is one of the best candidates as blue emitters
in PLEDs.
Cyclic voltammetry (CV) against Ag/Agþ was employed to in-
vestigate the redox behavior of PBTA.38 This film deposited on
a platinum plate electrode was scanned both positively and nega-
tively in 0.1 M anhydrous acetonitrile solution of tetrabutyl-
ammonium perchlorate (Bu4NClO4), using a platinum wire as the
counter electrode and Ag/AgCl (0.1 M) as the reference electrode
(see Supplementary data). The oxidation onset was determined to
be 0.71 V and estimating the band gap from the absorption onset,
the HOMO and LUMO energy levels of PBTA are found to be ꢁ5.11
and ꢁ2.90 eV, respectively.
4. Experimental section
4.1. General
All solvents were purified and freshly distilled prior to use
according to literature procedures. Commercially available mate-
rials were used as received unless noted. 1H NMR and 13C NMR
spectra were recorded on a Varian VNRS 600 MHz (Varian USA)
spectrophotometer using CDCl3 as solvent and tetramethylsilane
(TMS) as the internal standard. UVevis-NIR spectra were taken on
Cary 5000 (Varian USA) spectrophotometer. Photoluminescence
spectra were recorded on a Cary Eclipse (Varian USA), using a xenon
arc lamp as excitation source and a photomultiplier tube as de-
tector system. Number-average (Mn) and weight average (Mw)
molecular weights, and polydispersity index (PDI) of the polymer
products were determined by gel permeation chromatography
(GPC) with Agilent 1200 HPLC Chemstation using a series of mono
disperse polystyrene as standards in THF (HPLC grade) at 308 K.
Mass spectrometry and elemental analysis were performed by HCT
Basic System (Bruker, Germany) and Flash 200 (Thermo Scientific,
Netherlands), respectively. Cyclic voltammetry (CV) measurements
The optical properties of the metal free compound BTA and
metal complexes (BTAeCu and BTAePd) were investigated in
dimethylsulfoxide (DMSO) solution by UVevis spectroscopy. As
depicted in Fig. 4, the absorption bands of BTA are broad with
a maximum centered at 339 nm, which can be clearly attributed to
a pep transition. In contrast, both the complexes of BTAeCu and
*
BTAePd reveal an absorption peak centered at 352 nm and
shoulder peaks at 362 and 372 nm, respectively. The downhill shift
in UVevis spectra of metalated derivatives (BTAeCu and BTAePd)
is attributed to more extended conjugation systems in the metal
complex due to their increased planarity.

J. Lee et al. / Tetrahedron 66 (2010) 9440e9444
9443
were performed on Solartron SI 1287 with a three-electrode cell in
a 0.1 M tetrabutylammonium perchlorate (Bu4NClO4) solution in
acetonitrile at a scan rate of 50 mV/s at room temperature under
argon. A silver wire, a platinum wire, and a platinum plate were
used as the reference electrode, counter electrode, and working
electrode, respectively.
2H), 6.86 (d, J¼3.63 Hz, 2H), 4.26 (t, J¼7.82 Hz, 2H),1.87 (td, J¼15.56,
7.65, 7.65 Hz, 2H), 1.51e1.16 (m, 10H), 0.87 (t, J¼6.70, 6.70 Hz, 3H).
13C NMR (CDCl3, 150.9 MHz):
d 162.80, 137.92, 110.91, 52.70, 31.52,
28.99, 28.93, 26.55, 22.37, 13.83. MS (ESI mode)¼295.30 (Mþꢃ). El-
emental analysis: calculated for C14H21N3S2: C, 56.91; H, 7.16; N,
14.22; S, 21.70; found: C, 56.78; H, 7.29; N, 14.34; S, 21.98.
4.1.1. (2-Hexyldecyl)-bisthiazol-2-yl-amine (2). To a solution of 1
(1.0 g, 5.46 mmol) in 20 mL of N,N-dimethylformamide was added
K2CO3 (1.13 g, 8.17 mmol, 1.5 equiv) and 2-hexyl-1-decyl bromide
(2.0 g, 6.54 mmol, 1.2 equiv) and refluxed at 120 ꢂC overnight. The
cooled mixture was extracted with diethyl ether, washed with brine,
andthendried overMgSO4. Thecrudeproductwaschromatographed
on silica using 0e10% ethylacetate in hexane as eluent. Isolated
yield¼0.75 g (34%) as a yellow liquid. 1H NMR (CDCl3, 600 MHz):
4.1.5. Bis-(5-bromo-thiazol-2-yl)-octyl-amine (4). A mixture of octyl-
bisthiazol-2-yl-amine (2.5 g, 8.46 mmol), N-bromosuccinimide (3.3,
18.37 mmol, 2.2 equiv), and chloroform (25 mL) was stirred at room
temperature for 24 h under argon. The mixture was then extracted
into ether, washed with brine, and dried. The crude product was
chromatographed on silica using 0e10% ethylacetate in hexane as
eluent. Isolated yield¼3.7 g (97%) as a yellow oil. 1H NMR (CDCl3,
600 MHz):
d
7.34 (s, 2H), 4.21e4.07 (m, 2H), 1.81 (td, J¼15.43, 7.69,
d
7.44 (d, J¼3.60 Hz, 2H), 6.85 (d, J¼3.60 Hz, 2H), 4.27 (d, J¼7.59 Hz,
7.69 Hz, 2H),1.51e1.17 (m,10H), 0.88 (t, J¼6.72, 6.72 Hz, 3H).13C NMR
2H), 2.22e2.10 (m,1H),1.31e1.20 (m, 24H), 0.87 (t, J¼6.82 Hz, 6H).13C
(CDCl3, 150.9 MHz): d 161.69, 138.37, 100.45, 51.90, 31.51, 28.94,
NMR (CDCl3,150.9 MHz):
d
163.61,137.76,110.96, 56.55, 35.63, 31.63,
28.90, 26.48, 22.37, 13.85. MS (ESI mode): 452.90 (Mþꢃ). Elemental
analysis: calculated for C13H18Br2N3S2: C, 37.10; H, 4.23; Br, 35.26; N,
9.27; S, 14.15; found: C, 36.87; H, 4.51; N, 9.41; S, 14.27.
31.23, 29.69, 29.36, 29.04, 26.14, 22.42, 13.87. MS (ESI mode)¼407.70
(Mþꢃ). Elemental analysis: calculated for C22H37N3S2: C, 64.81; H,
9.15; N, 10.31; S, 15.73; found: C, 65.03; H, 9.29; N, 10.14; S, 15.58.
4.1.6. 4-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)triphenylamine
(5). To (4-bromo-phenyl)-diphenyl-amine (2.0 g, 6.17 mmol) in
a 250 mL Schlenk flask, 30 mL of anhydrous THF is added and
cooled to ꢁ78 ꢂC in an acetone/dry ice bath. To this, 5.78 mL of
1.6 M n-butyllithium (1.5 equiv) is added slowly and stirred for
30 min. Then 2.14 mL of 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-
dioxaborolane (1.7 equiv) is added and slowly allowed to warm to
room temperature. The reaction is stirred overnight and then
quenched with saturated salt, the product is then extracted into
ether, washed with brine, and dried. The crude product was chro-
matographed on silica gel eluted with 0e10% ethylacetate in hex-
ane. Isolated yield¼91.6% as a yellow oily liquid. 1H NMR (CDCl3,
4.1.2. Bis-(5-bromo-thiazol-2-yl)-(2-hexyldecyl)-amine (3). A mix-
ture of
2 (0.637 g, 1.56 mmol) N-bromosuccinimide (0.596,
3.354 mmol, 2.15 equiv) and chloroform (15 mL) was stirred at room
temperature for 24 h under argon. The mixture was then extracted
into ether, washed with brine, and dried. The crude product was
chromatographed on silica using 0e10% ethylacetate in hexane as
eluent. Isolated yield¼0.58 g (65%) as a yellow oil. 1H NMR (CDCl3,
600 MHz):
d
7.32 (s, 2H), 4.11 (d, J¼7.65 Hz, 2H), 2.20e2.11 (m, 1H),
1.32e1.21 (m, 24H), 0.90 (t, J¼6.7 Hz, 6H). 13C NMR (CDCl3,
150.9 MHz):
d 162.25, 138.20, 100.16, 55.49, 35.40, 31.43, 30.97,
29.44, 29.02, 28.83, 25.89, 22.23,13.68. MS (ESI mode)¼565.10 (Mþꢃ).
Elemental analysis: calculated for C22H35Br2N3S2: C, 46.73; H, 6.24;
Br, 28.26; N, 7.43; S, 11.34; found: C, 46.87; H, 6.31; N, 7.41; S, 11.14.
600 MHz):
d
7.75 (d, J¼7.93 Hz, 2H), 7.37e7.26 (m, 5H), 7.18 (d,
J¼7.20 Hz, 4H), 7.11 (d, J¼7.31 Hz, 3H), 1.40 (s, 12H). 13C NMR (CDCl3,
150.9 MHz):
d 150.38, 147.18, 135.67, 129.09, 128.98, 124.76, 123.95,
4.1.3. Poly(5,50-(2-hexyldecyl)-bisthiazol-2-yl-amine)
(PBTA). Bis
123.15, 122.45, 121.59, 83.31, 24.66. MS (ESI mode): 371.20 (Mþꢃ).
Elemental analysis: calculated for C24H26BNO2: C, 77.64; H, 7.06; B,
2.91; N, 3.77; O, 8.62; found: C, 77.89; H, 7.25; N, 3.75.
(cyclooctadiene)nickel (589.0 mg, 2.17 mmol, 2.4 equiv), cyclo-
octadiene (266.0 mL, 2.17 mmol, 2.4 equiv), and 2,20-bipyridine
(335 mg, 2.17 mmol, 2.4 equiv) were dissolved in anhydrous toluene
(7 mL) and anhydrous N,N-dimethylformamide (7 mL) in a Schlenk
flask in a glovebox. The mixture was heated at 60 ꢂC with stirring
under argon for 20 min to generate the catalyst, and then a solution
of the dibromide 3 (512 mg, 0.905 mmol) in anhydrous toluene
(10 mL) was added. The reaction was heated 75 ꢂC for 3 days. Then
a mixture of toluene (4 mL) and bromobenzene (0.10 mL) was added
and the mixture was heated at 75 ꢂC for an additional 12 h. This was
then poured into a mixture of methanol and concentrated NH4OH
(1:1, 300 mL) and stirred for 4 h and filtered. The precipitated solid
was washed with methanol (200 mL) and subjected Soxhlet ex-
traction for 2 days in acetone. Isolated yield of PBTA¼230 mg (63%).
GPC analysis Mn¼5.71ꢀ103 g/mol, Mw¼6.02ꢀ103 g/mol, and D¼2.22
(against PS standard). Only soluble portion was measured by GPC.
Elemental analysis: calculated for C22H35N3S2: C, 65.14; H, 8.70; N,
10.36; S, 15.81; found: 65.05; H, 8.99; N, 10.14; S, 15.58.
4.1.7. 5-(4-(Diphenylamino)phenyl)-N-(5-(4-(diphenylamino)phe-
nyl)thiazol-2-yl)-N-octylthiazol-2-amine (2-TPA-BTA). The boronic
ester 5 (0.81 g, 2.18 mmol), 4 (0.4 g, 0.88 mmol) were dissolved in
THF (20 mL) in a 100 mL Schlenk flask. To this solution were added
aqueous 2 M K2CO3 solution (10 mL). The solution was purged with
argon for 20 min, and the tetrakis(triphenylphosphine)palladium
(61 mg, 0.06 equiv) was added and the reaction was heated with
stirring at 85 ꢂC. The reaction was followed by TLC and after 2 days
was worked up. The cooled mixture was extracted with diethyl
ether, and the extract was washed with brine and then dried over
MgSO4. The crude product so obtained was purified by chroma-
tography on silica with 0e30% dichloromethane in hexane as elu-
ent and more purified by recrystallization from THF in EtOH to
afford 0.23 g (33.4%) of the title compound as yellow powders. 1H
NMR (CDCl3, 600 MHz):
d
7.49 (s, 2H), 7.31 (d, J¼8.60 Hz, 4H), 7.18
(dd, J¼10.36, 5.24 Hz, 8H), 7.10e6.84 (m, 16H), 4.49e4.04 (m, 2H),
2.04e1.65 (m, 2H), 1.51e1.20 (m, J¼54.59 Hz, 10H), 0.80 (t, J¼6.47,
4.1.4. Octyl-bisthiazol-2-yl-amine. To a mixture solution of 1 (4.0 g,
21.85 mmol) and NaH (60% in oil, 1.2 equiv) in 25 mL of N,N-dime-
thylformamide at room temperature was added 1-octylbromide
(1.2 equiv) dropwise under argon. This solution was stirred at room
temperature for 12 h. The mixture was then extracted into ether,
washed with brine, and dried. The crude product was chromato-
graphed on silica gel eluting with 0e10% ethylacetate in hexane.
Isolated yield¼3.12 g (48.4%, first fraction) as yellow solid and 3.01
(46.5% second fraction) as a yellow liquid. The first fraction was used
6.47 Hz, 3H). 13C NMR (CDCl3, 150.9 MHz):
d 160.69, 147.39, 147.27,
131.19, 129.31, 126.79, 125.60, 124.50, 123.71, 123.15, 31.77, 29.27,
29.18, 26.93, 26.80, 22.61, 14.08. MS (ESI mode): 781.30 (Mþꢃ). El-
emental analysis: calculated for C50H47N5S2: C, 76.79; H, 6.06; N,
8.95; S, 8.20; found: C, 76.99; H, 6.25; N, 8.15; S, 8.37.
4.1.8. Cu(II) complex of BTA (BTAeCu). To a solution of BTA (0.5 g,
2.7 mmol) in THF (30 mL) was added copper(II) triflate (1.0 equiv)
solution in THF (30 mL) and stirred for 15 h at room temperature.
for the next step. 1H NMR (CDCl3, 600 MHz):
d
7.45 (d, J¼3.62 Hz,

9444
J. Lee et al. / Tetrahedron 66 (2010) 9440e9444
Precipitated product was filtered, washed with THF, and dried.
Isolated yield¼20.1% as a purple solid. The product was dissolved in
N,N-dimethylformamide, and diethyl ether was diffused into the
solution, forming a mixture of purple crystals precipitate.
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Acknowledgements
This work was supported by Basic Science Research Program
through the National Research Foundation of Korea (NRF) funded
by the Ministry of Education, Science and Technology (2010-
0002494) and the National Research Foundation of Korea Grant
funded by the Korean Government (MEST) (2010-0019408) (2010-
0026916) and (MEST) (NRF-2009-C1AAA001-2009-0092950) .
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