Synthesis of bis(phenazasiline) compounds and their application for TFT as a model of phenazasiline-containing polymers

Article abstract of DOI:10.1246/bcsj.20100077

New bis(phenazasiline) compounds were prepared and a thin film transistor (TFT) device containing bis(phenazasiline) derivatives was fabricated. The bis(phenazasiline)s, prepared from 2-bromo-8-methylphenazasiline, were effective materials for TFT. Obtained bis(phenazasiline) derivatives were considered to be model compounds of phenazasiline-containing polymers in the prediction of TFT properties.

Full text of DOI:10.1246/bcsj.20100077

1282 Bull. Chem. Soc. Jpn. Vol. 83, No. 10, 1282–1284 (2010)
Short Articles
strates for the extension fixation of DNA.14 However, it seems
that there have been no reports about the transistor properties of
phenazasiline-containing compounds.
Synthesis of Bis(phenazasiline)
Compounds and Their Application
for TFT as a Model of
We therefore planned to make thin film transistor (TFT)
devices using a phenazasiline-containing polymer by a solution
casting method. However, solubility of the polymer some-
times becomes a problem when the devices are prepared by
casting. In order to investigate the effect of the polymer’s
phenazasiline unit on transistor properties, we synthesized two
new bis(phenazasiline) derivatives, (bis(7,9,10,10-tetramethyl-
9,10-dihydro-9-aza-10-silaanthracen-2-yl) (P-P) and 2,5-
bis(7,9,10,10-tetramethyl-9,10-dihydro-9-aza-10-silaanthracen-
2-yl)thiophene (P-T-P)), which are model compounds of phen-
azasiline-containing polymers (poly(9-methyl-10,10-dioctyl-
Phenazasiline-Containing Polymers
Hideki Hayashi,*1 Makoto Murase,1
Take-aki Koizumi,2 Koya Ohara,3
Takeshi Miyabayashi,4 and Masahiko Kojima1
1Nagoya Municipal Industrial Research Institute,
9,10-dihydro-9-aza-10-silaanthracene-2,7-diyl)
(PPhenaz)9
3-4-41 Rokuban, Atsuta-ku, Nagoya 456-0058
and poly(9-methyl-10,10-dioctyl-9,10-dihydro-9-aza-10-sila-
anthracene-2,7-diyl-alt-thiophene-2,5-diyl) (PAR)13) as shown
in Scheme 1. Herein we report the chemical and TFT properties
of P-P and P-T-P. In addition, we describe the transistor
properties of the films made of the phenazasiline-containing
polymers.
Bis(phenazasiline) derivatives, P-P and P-T-P, were synthe-
sized by the coupling reaction of monobromophenazasiline,
P-Br, as shown in Scheme 2.
2Chemical Resources Laboratory, Tokyo Institute
of Technology, 4529 Nagatsuta, Midori-ku,
Yokohama 226-8503
3Tsuchiya Co., LTD., 22-4 Higashi-namiki-kita,
Yama-machi, Chiryu 472-0006
4Brother Industries, LTD., 2-1 Naeshiro-cho, Mizuho-ku,
Nagoya 467-0841
P-Br was prepared as shown in Scheme 2a. Bromination of
4-methyldiphenylamine by N-bromosuccinimide (NBS) gave
2,2¤,4-tribromo-4¤-methyldiphenylamine (1). 1 was treated with
NaH, and then reacted with iodomethane to give N-methylated
compound 2. Dilithiation of 2 using n-butyllithium in diethyl
ether followed by the addition of dichlorodimethylsilane
produced P-Br. Two bis(phenazasiline) derivatives, P-P and
P-T-P, were synthesized by Ni(0)-promoted dehalogenative
condensation and Pd-catalyzed cross-coupling reaction, respec-
tively (Scheme 2b).
Received March 15, 2010
E-mail: hayashi.hideki@nmiri.city.nagoya.jp
New bis(phenazasiline) compounds were prepared and
a thin film transistor (TFT) device containing bis(phenaza-
siline) derivatives was fabricated. The bis(phenazasiline)s,
prepared from 2-bromo-8-methylphenazasiline, were effec-
tive materials for TFT. Obtained bis(phenazasiline) deriva-
tives were considered to be model compounds of phen-
azasiline-containing polymers in the prediction of TFT
properties.
model compounds
polymers
C8H17
Me
N
C8H17
Si
N
Me
Me
Si
N
Me
Si
Me
Me
Me
n
Me
PPhenaz9)
P-P
Me
Diphenylamines with a bridging structure are interesting as
functional materials. Phenazasiline (=9,10-dihydro-9-aza-10-
silaanthracene), which has a Si-bridged diphenylamine frame-
work, is one of these materials. Phenazasiline derivatives are
potentially useful as a hole transporting layer for electro-
luminescent (EL) devices1 and antioxidants.2 Phenazasiline-
containing polyesters and polyamides possess high thermal
stability.3 Previously, Casalbore-Miceli and co-workers have
synthesized phenazasiline homopolymers by electrochemical
oxidation of trimethylphenazasiline, and examined their elec-
trochromic behavior.4-8 Although several phenazasiline-con-
taining polymers have been reported, they had only methyl
substituent on the N atom and phenyl3 or methyl4-8 substituents
on the Si atom.
Recently, we have prepared phenazasiline-containing poly-
mers with various substituents on the N and Si atoms by
organometallic polycondensation using the corresponding
dibromophenazasiline to obtain structurally well-defined ³-
conjugated polymers.9-11 We have also investigated their
application as hole transport layers of EL devices,9 electro-
chromic devices,12 functional additives for resin,13 and sub-
C8H17
C8H17
Si
Me
Me
Me
Me
Si
N
Me
Si
N
Me
S
S
N
n
Me
P-T-P
Me
PAR13)
Me
Scheme 1. Bis(phenazasiline) compounds and relative
polymers.
(a) preparation of P-Br
Me
Me
1) NaH
2) MeI
76%
Me
Me
1) 2 n-BuLi
Br
Br
Br
MeN
Br
Me
2) Me2SiCl2
3 NBS
89%
HN
MeN
Si
HN
52%
Me
Br
P-Br
Br
Br
1
2
(b) preparation of bis(phenazasiline)s
Ni(cod)2 + bpy
64%
Me
Me
P-P
Me
Si
Br
29Si NMR: -22.06
N
Me
Me3Sn
, Pd(PPh3)4
SnMe3
49%
P-T-P
29Si NMR: -21.97
S
P-Br
29Si NMR: -21.62
Scheme 2.
Published on the web October 5, 2010; doi:10.1246/bcsj.20100077

H. Hayashi et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 10 (2010) 1283
Table 1. Transistor Properties of the Devices
(e)
(a)
(c) (b) (d)
Run
No.
Device Method of film Mobility ON-OFF
Compound
¹1
typea)
formationb) /cm2 V¹1 s
ratio
¹5
¹5
¹4
¹5
¹6
¹5
¹4
1
2
3
4
5
6
7
8
P-P
P-P
P-P
P-T-P
P-T-P
P-T-P
PPhenaz
PAR
bc
bc
tc
bc
bc
tc
vacuum
cast
vacuum
vacuum
cast
vacuum
cast
cast
2.91 © 10
1.09 © 10
1.22 © 10
1.04 © 10
1.86 © 10
2.06 © 10
1.71 © 10
104.03
102.73
104.89
102.17
101.24
104.42
102.83
300
400
Wavelength/ nm
500
bc
bc
c)
c)
®
®
Figure 1. Absorption spectra of (a) P-P, (b) P-T-P,
(c) PPhenaz, (d) PAR, and (e) P-Br in CHCl3.
a) bc: bottom-contact type, tc: top-contact type. b) vacuum:
vacuum-deposited, cast: cast from 1,2-dichloroethane. c)
Transistor properties were not observed.
C15
C9
TFT was fabricated by using bis(phenazasiline) compounds
P-P and P-T-P. The transistor properties of the devices are
summarized in Table 1. P-P and P-T-P showed p-type
transistor properties. Comparing Runs 1 and 2 (for P-P) and
Runs 4 and 5 (for P-T-P), the properties of the devices
produced by vacuum deposition were better than those of the
devices made by casting in both cases, and this tendency was
the same as previously reported results.16 From a comparison
between Runs 1 and 3 (For P-P) and between Runs 4 and 6
(for P-T-P), the TFT properties of the top-contact device are
better than those of the bottom-contact one, and this tendency
was the same as previously reported.17 As shown in Table 1,
the TFT properties of the P-P device were better than those of
the P-T-P device. This agreed with the tendency in conduc-
tivity of an electrochemically doped cast film of relative
N1
C3
C4
C10
C8
C2
C1
C11
C5
C6
Br1(C16*)
C7
Si1
C13
C12
C16(Br1*)
C14
Figure 2. P-Br with 50% ORTEP drawing ellipsoidal level.
C16 and Br1 were disordered.
As shown in Scheme 2b, the 29Si{1H} NMR spectra of P-P
and P-T-P showed signals in almost the same region as that of
P-Br. Their 1H and 13C{1H} NMR spectra also supported these
structures.
polymers (PPhenaz (17 S cm )
¹1 15 and PAR (1.8 S cm¹1)13). As
Figure 1 shows the absorption spectra of P-P, P-T-P,
PPhenaz, PAR, and P-Br in a CHCl3 solution. The -max
based on ³-³* transition of P-P appears at 339 nm (Figure 1a),
shown in Figure 3, XRD patterns of films of P-P and P-T-P
suggest that crystallinity of the film seems to also affect the
transistor properties in the case of bis(phenazasiline) com-
pounds.
which is longer than that of monophenazasiline P-Br (-max
=
295 nm, Figure 1e). Similarly, the -max of P-T-P (379 nm,
Figure 1b) is observed at a longer wavelength than that of
P-Br. On the other hand, -max of P-P and P-T-P in CHCl3
appeared at a shorter wavelength than those of corresponding
polymers, PPhenaz (364 nm, Figure 1c) and PAR (405 nm,
Figure 1d). These results suggest that the differences of
absorption -max derive from the effective ³-conjugation
system. Figure 1 also suggested that from comparison between
P-P and P-T-P, the introduction of a thienylene unit makes
As described above, P-P and P-T-P showed p-type transistor
properties. Accordingly, phenazasiline-containing polymers are
also expected to show transistor properties. Therefore, TFT
devices were fabricated using phenazasiline-containing poly-
mers by solution casting. As shown in Figure 3c, the obtained
PPhenaz film was amorphous.
The transistor properties of the polymer-using devices are
summarized in Table 1. The PPhenaz-based device showed
transistor properties, whereas the PAR-based device did not. In
short, the transistor properties of the PPhenaz device were
better than those of the PAR device. This difference in the
transistor properties between PPhenaz and PAR agreed with
the tendencies of P-P and P-T-P. Transistor properties of
phenazasiline homopolymer seem to be improved by extension
of ³-conjugation.
In conclusion, we report the preparation of P-P and P-T-P as
model compounds of phenazasiline-containing polymers. We
also found that phenazasiline-containing compounds are useful
materials for construction of TFT devices. We successfully
investigated the relationship between the degree of polymer-
ization and transistor properites of phenazasiline-containing
materials. We believe that phenazasiline-containing materials’
transistor properties could be improved by molecular design.
-
longer. This relationship was the same as that of the
max
corresponding polymers PPhenaz and PAR.
To investigate the structure of phenazasiline unit of P-P and
P-T-P, the molecular structure of P-Br was determined by
X-ray crystallography. Figure 2 shows the ORTEP drawing of
P-Br, showing P-Br’s bent structure between two benzene
units whose dihedral angle is 154.7(3)°. On the other hand, the
sum of the angles around N1 of P-Br is 358.6(7)°, showing that
the surroundings of the N atom have a planar structure. These
values are almost the same as those of dibromotrimethyl-
phenazasiline, 151.23 and 358.5°, respectively.15 The flatness
around the N atom in P-Br strongly suggested the expansion of
³-conjugation through the N atom, even though the two
benzene rings in P-Br form a bent structure.

1284 Bull. Chem. Soc. Jpn. Vol. 83, No. 10 (2010)
© 2010 The Chemical Society of Japan
123.42, 122.90, 122.59, 115.08, 114.98, 38.19, 20.45, ¹1.97.
Anal. Found: C, 71.4; H, 6.2; N, 4.1; S, 5.6%. Calcd for
C36H38N2SSi2¢0.9H2O: C, 71.7; H, 6.7; N, 4.6; S, 5.3%.
We thank Dr. Hiroki Fukumoto of Chemical Resources
Laboratory, Tokyo Institute of Technology for XRD analysis of
cast films of phenazasiline-containing compounds. Part of this
research was supported by the regional consortium R&D
projects and the regional innovation R&D projects of the
Ministry of Economy, Trade and Industry (METI).
(a)
(b)
(c)
(d)
0
10
20
30
40
Supporting Information
2θ /degree (Cu Kα)
Experimental details of the preparation of 1, 2, P-Br, P-P,
and P-T-P, and crystallographic data of P-Br, and of the
fabrication of TFT with phenazasiline-containing compounds
are shown. Optical data of P-Br, P-P, P-T-P, PPhenaz, and
PAR are also shown. This material is available free of charge
on the Web at: http://www.csj.jp/journals/bcsj/.
Figure 3. XRD patterns of (a) P-P, (b) PPhenaz, and (c)
P-T-P cast film on a polyimide substrate. XRD pattern of
the polyimide substrate was shown in (d) for comparison.
Experimental
Reagent. 2,5-Bis(trimethylstannyl)thiophene,18 PPhenaz
(Mw = 4.3 © 103, Mw/Mn = 1.6),15 and PAR (Mw = 4.4 © 103,
Mw/Mn = 1.4)13 were prepared by the reported method. Other
chemicals were used as purchased.
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Preparation Data of Bis(7,9,10,10-tetramethyl-9,10-di-
hydro-9-aza-10-silaanthracen-2-yl) (P-P): P-P was obtained
1
as a colorless powder. H NMR (400 MHz, CDCl3): ¤ 7.7-6.9
(m, 12H), 3.55 (s, 6H), 2.34 (s, 6H), 0.45 (s, 12H).
13C{1H} NMR (400 MHz, CDCl3): ¤ 149.88, 148.69, 133.58,
132.71, 131.30, 130.66, 129.23, 128.32, 123.34, 122.98,
115.06, 114.86, 38.10, 20.44, ¹1.99. Anal. Found: C, 74.3;
H, 6.9; N, 5.2%. Calcd for C32H36N2Si2¢0.6H2O: C, 74.5; H,
7.3; N, 5.4%.
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dihydro-9-aza-10-silaanthracen-2-yl)thiophene (P-T-P): P-
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CDCl3): ¤ 7.7-6.9 (m, 14H), 3.54 (s, 6H), 2.34 (s, 6H), 0.47
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