The synthesis of difluoro and dimethyl derivatives of 2,6- Bis(dicyanomethylene)-2,6-dihydro-4H-cyclopenta[2,1-b:3,4-b′] -dithiophen-4-one (CPDT-TCNQ) and the conducting properties of the metallic salts based on the dimethyl derivative

Article abstract of DOI:10.1246/bcsj.77.1487

In order to investigate how the sheet-like network along the side-by-side direction constructed by the strong inter-column S...N and O...H atom-atom contacts influences the stability of the metallic state of novel one-dimensional metallic anion radical salts of 2,6-bis(dicyanomethylene)-2,6- dihydro-4H-cyclopenta[2,1-b:3,4-b′]dithiophen-4-one (CPDT-TCNQ), the 3,5-difluoro (F₂CPDT-TCNQ) and 3,5-dimethyl (Me₂CPDT-TCNQ) derivatives of CPDT-TCNQ, not possessing hydrogen atoms at the 3,5-positions to construct the inter-column O...H contacts, have been synthesized. The anion radical salts, Me₄X(Me₂CPDT-TCNQ)₂ (X = P and As), showed a metallic temperature dependence of the resistivity from room temperature down to around 240 K and 200 K, respectively, whereas Me ₄X(Me₂CPDT-TCNQ)₂ (X = N and Sb) were semiconducting. The metal-insulator transition temperatures (T_M1) of Me₄X(Me₂CPDT-TCNQ)₂ (X = P and As) are significantly higher than those of MX₄(CPDT-TCNQ)₂ (X = P and As). Moreover, the extent of destabilization of the metallic state is much more significant in Me₄N(Me₂CPDT-TCNQ)₂, since MeN₄(CPDT-TCNQ)₂ is metallic down to 130 K. Although electric conduction can not occur along the side-by-side direction in either salt of CPDT-TCNQ and Me₂CPDT-TCNQ, these facts suggest that the two-dimensional sheet-like molecular network along the a-axis may contribute to stabilize the one-dimensional metallic states of the anion radical salts of CPDT-TCNQ.

Full text of DOI:10.1246/bcsj.77.1487

ꢀ 2004 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 77, 1487–1497 (2004) 1487
The Synthesis of Difluoro and Dimethyl Derivatives of 2,6-
Bis(dicyanomethylene)-2,6-dihydro-4H-cyclopenta[2,1-b:3,4-b0]-
dithiophen-4-one (CPDT-TCNQ) and the Conducting Properties
of the Metallic Salts Based on the Dimethyl Derivative
ꢀ;1;2
Takehiro Chonan1 and Kazuko Takahashi
1Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578
2Center for Interdisciplinary Research, Tohoku University, Sendai 980-8578
Received January 5, 2004; E-mail: tkazuko@cir.tohoku.ac.jp
In order to investigate how the sheet-like network along the side-by-side direction constructed by the strong inter-
column S N and O H atom–atom contacts influences the stability of the metallic state of novel one-dimensional metallic
ꢁꢁꢁ
ꢁꢁꢁ
anion radical salts of 2,6-bis(dicyanomethylene)-2,6-dihydro-4H-cyclopenta[2,1-b:3,4-b0]dithiophen-4-one (CPDT-
TCNQ), the 3,5-difluoro (F2CPDT-TCNQ) and 3,5-dimethyl (Me2CPDT-TCNQ) derivatives of CPDT-TCNQ, not pos-
sessing hydrogen atoms at the 3,5-positions to construct the inter-column O H contacts, have been synthesized. The
ꢁꢁꢁ
anion radical salts, Me4X(Me2CPDT-TCNQ)2 (X = P and As), showed a metallic temperature dependence of the resis-
tivity from room temperature down to around 240 K and 200 K, respectively, whereas Me4X(Me2CPDT-TCNQ)2 (X = N
and Sb) were semiconducting. The metal–insulator transition temperatures (TMI) of Me4X(Me2CPDT-TCNQ)2 (X = P
and As) are significantly higher than those of MX4(CPDT-TCNQ)2 (X = P and As). Moreover, the extent of destabiliza-
tion of the metallic state is much more significant in Me4N(Me2CPDT-TCNQ)2, since MeN4(CPDT-TCNQ)2 is metallic
down to 130 K. Although electric conduction can not occur along the side-by-side direction in either salt of CPDT-TCNQ
and Me2CPDT-TCNQ, these facts suggest that the two-dimensional sheet-like molecular network along the a-axis may
contribute to stabilize the one-dimensional metallic states of the anion radical salts of CPDT-TCNQ.
Since the discovery of one-dimensional metallic behavior of
the tetracyano-p-quinodimethane (TCNQ)-tetrathiafulvalene
(TTF) complex,1 a great deal of investigation has been devoted
towards the synthesis of a variety of ꢀ-acceptors and ꢀ-donors
with the aim of developing novel organic molecular metals or
organic superconductors. However, the investigations on the
molecular design and synthesis of ꢀ-acceptor molecules for
organic conductors have been almost limited to those con-
cerning TCNQ, N,N0-dicyano-p-quinone diimine (DCNQI)
and M(dmit)2 (dmit = 1,3-dithiole-2-thioxo-4,5-dithiolato)
families.2–4 In recent years, oligothiophene-TCNQs5 were syn-
thesized to decrease on-site Coulomb repulsion in the dianion
state and were expected to increase intermolecular interactions
ene)-2,6-dihydro-4H-cyclopenta[2,1-b:3,4-b0]dithiophen-4-one
(CPDT-TCNQ: 1)8 incorporating three electron-accepting
groups in one molecule. CPDT-TCNQ has a fairly high elec-
tron-accepting ability (E1 ¼ þ0:04 V vs SCE in CH2Cl2)
red
and was reduced in three reversible one-electron transfer steps
to the trianion radical state. The single crystalline anion radical
salts of CPDT-TCNQ, namely, Me4X(CPDT-TCNQ)2 (X = N,
P, and As) exhibited the metallic temperature dependence of
the resistivity. In the crystal structures of the three anion radical
salts which are isostructural compounds, CPDT-TCNQ mole-
cules stack along the b-axis dimerizing weakly in the stacking
columns, as shown in Fig. 1(a). The acceptor columns are
strongly connected along the side-by-side direction by the four
ꢀ
ꢀ
by means of S S contacts of the thiophene rings. However, un-
S N (3.04–2.97 A) and two O H (3.25–3.28 A) atom–atom
ꢁꢁꢁ ꢁꢁꢁ
ꢁꢁꢁ
fortunately, the oligothiophene-TCNQs do not easily form met-
allic conducting complexes and their electron-accepting abili-
ties are relatively low. On the other hand, heterophene-extend-
ed [3]radialene type acceptors gave single crystalline charge-
transfer (CT) complexes with tetrathiafulvalene (TTF) and with
tetrathiatetracene (TTT) showing metallic properties in which
the conducting carrier of the TTF complex was proven to be
electrons.6 It has also been reported that the dibromo derivative
of the thieno[3,2-b]thienoquinonoid isologue of N,N0-dicyano-
quinone diimine (DCNQI) formed a metallic CT complex with
TTF.7
contacts (Fig. 1(b)), constructing a sheet-like molecular net-
work along the a-axis. However, these salts have an extremely
one-dimensional metallic electronic structure along the stack-
ing b-axis, because the ꢀ-electron densities on the peripheral
S and O atoms in the LUMO (lowest unoccupied molecular or-
bital) of the CPDT-TCNQ molecule are very low. In this case,
electrical conduction can not occur along the a-axis. The one-
dimensional metallic salts showed second order type metal–in-
sulator (MI) transitions under ambient pressure at 130, 165, and
185 K accompanied by the superlattice formation of (a, 2b, c),
(2a, b, c), and (2a, b, c) for the Me4N, Me4P, and Me4As salts,
respectively.9 Thus the origins of the metal–insulator transi-
tions have been considered to be the 2kF CDW for the Me4N
In 1998, we reported successful synthesis of a novel hetero-
phene-TCNQ type acceptor, namely, 2,6-bis(dicyanomethyl-
Published on the web August 6, 2004; DOI 10.1246/bcsj.77.1487

1488 Bull. Chem. Soc. Jpn., 77, No. 8 (2004)
Difluoro and Dimethyl Derivatives of CPDT-TCNQ
radical salts of Me2CPDT-TCNQ. The substitutional effects
of the fluorine and methyl groups on the electron-accepting
ability of the new acceptors, F2CPDT-TCNQ and Me2CPDT-
TCNQ are also revealed.
(a)
o
c
Results and Discussion
b
Synthesis. F2CPDT-TCNQ (2) was synthesized through the
route depicted in Scheme 1. 3,4-Dibromothiophene (4) was first
mono-lithiated with butyllithium at ꢂ78 ꢃC and then allowed to
react with 4-bromo-3-thiophenecarbaldehyde (5)10 to give the
methanol 6 in 70% yield. The ketone 7, prepared from 6 by ox-
idation with chromium trioxide in acetic acid, was allowed to
react with ethylene glycol in the presence of a catalytic amount
of p-toluenesulfonic acid in benzene to produce the 4,40-dibro-
mo ketal 8 in 98% yield. The 4,40-difluoro ketalꢃ9 was prepared
by dilithiation of 8 with butyllithium at ꢂ78 C in THF and
subsequent fluorination of the resulting dilithio derivative with
N-fluorobenzenesulfonimide (NFBS) in 49% yield. Iodination
of 9 with N-iodosuccinimide (NIS) occurred selectively at the
ꢁ-positions of the fluorine atoms giving the 5,50-diiodo deriva-
tive 10 in 89% yield. Then, the compound 10 was dilithiated
with butyllithium at ꢂ78 ꢃC, and the resulting 5,50-dilithio de-
rivative was submitted to the reaction with trimethylsilyl chlo-
ride (TmsCl) to give the 5,50-bis(trimethylsilyl) derivative 11 in
69% yield. The desired cyclopentadithiophene derivative 12
was obtained by the intra-molecular Ullman coupling reaction
of the 2,20-dilithio derivative ofꢃ11, generated by dilithiation of
11 with t-butyllithium at ꢂ78 C, with CuCl2 in THF. Treat-
ment of 12 with NIS in a mixture of acetic acid and chloroform
(1:1, v/v) at room temperature afforded the 2,6-diiodo deriva-
tive 13 in 91% yield. The compound 13 was then allowed to
react with sodium dicyanomethanide, prepared in situ from
malononitrile and sodium hydride, in refluxing THF containing
a catalytic amount of tetrakis(triphenylphosphine)palladium
[Pd(PPh3)4],11 followed by oxidation with aqueous bromine
to give 2,6-bis(dicyanomethylene)-4-ethylenedioxy-3,5-difluo-
ro-2,6-dihydro-4H-cyclopenta[2,1-b:3,4-b0]dithiophene (EO-
F2CPDT-TCNQ: 14) in 68% yield. When 14 was treated with
70% perchloric acid in dichloromethane, F2CPDT-TCNQ (2)
was obtained in 19% yield as a violet powder. F2CPDT-TCNQ
is air-stable and much more soluble than CPDT-TCNQ (1) in
polar organic solvents such as dichloromethane and acetoni-
trile.
(b)
S2
N2
S1
C11
O1
S1
N2
O1
C11
S2
Fig. 1. Crystal structures of Me4N(CPDT-TCNQ)2: (a) pro-
jection onto the bc-plane and (b) side-by-side hetero atom
contacts among the CPDT-TCNQ molecules.
O
NC
NC
CN
CN
S
S
CPDT-TCNQ: 1
O
R
R
NC
NC
CN
CN
S
S
R=F: F2CPDT-TCNQ: 2
R=Me: Me2CPDT-TCNQ: 3
Chart 1. Chemical structural formulas of CPDT-TCNQ,
F2CPDT-TCNQ, and Me2CPDT-TCNQ.
salt, and the 4kF CDW for the Me4P and Me4As salts. Although
the electrical conduction can not occur along the a-axis, the
crystal structurre consisting of strong intercolumn S N and
O H atom–atom contacts along the a-axis can influence the
Me2CPDT-TCNQ (3) was synthesized starting from the 4,40-
dibromo ketal 8 according to the route shown in Scheme 2. The
dibromo ketal 8 was dilithiated with 2 molar amounts of butyl-
lithium at ꢂ78 ꢃC in THF and then allowed to react with excess
methyl iodide to give the 4,40-dimethyl derivative 15 in 99%
yield. Direct iodination of 15 was achieved by treatment with
NIS at room temperature in a mixture of acetic acid and chloro-
form (1:1, v/v) to give the 5,50-diiodo derivative 16 in 78%
yield. The diiodo derivative 16 was first dilithiated with butyl-
lithium at ꢂ78 ꢃC and then treated with trimethylsily chloride
at ꢂ78 ꢃC to give 17 in 87% yield. The 2,20-dilithio derivative
of 17, prepared by lithiation of 17 with t-butyllithium at ꢂ78
ꢃC, was allowed to react with CuCl2 to produce the cyclopenta-
dithiophene derivative, which was subsequently desilylated
without purification with tetrabutylammonium fluoride (TBAF)
in THF to give 18 in 79% yield. The 2,6-diiodo derivative 19,
ꢁꢁꢁ
ꢁꢁꢁ
stability of the one-dimensional metallic state and influence
the MI transition temperature of the anion radical salts of
CPDT-TCNQ. Therefore, examination into the electric con-
ducting behavior of the anion radical salts of the 3,5-disubsti-
tuted derivatives of CPDT-TCNQ appears to be very helpful
in evaluating the effect of the structural two-dimensional
sheet-like network on the stability of the one-dimensional met-
allic state of these salts, since the anion radical salts of 3,5-di-
substituted CPDT-TCNQs can not construct the sheet-like net-
work along the a-axis due to the lack of the inter-column O H
ꢁꢁꢁ
contacts. To this end, we have now synthesized the 3,5-difluoro
and 3,5-dimethyl derivatives of CPDT-TCNQ, namely,
(F2CPDT-TCNQ: 2) and (Me2CPDT-TCNQ: 3), respectively
(Chart 1), and clarified the conducting properties of the anion

T. Chonan et al.
Bull. Chem. Soc. Jpn., 77, No. 8 (2004) 1489
O
1) BuLi
in THF
H
OH
S
Br
Br
O
O
Br
Br
Br
Br
Br
Br
HO(CH2)2OH /TsOH
in Benzene
CrO3
Br CHO
in AcOH
S
S
S
S
S
S
2)
3) H3O+
5
S
6
4
7
8
1) BuLi
1) BuLi
in THF
O
O
O
O
O
O
NIS
AcOH -CHCl3
in THF
F
F
F
F
F
F
I
I
Tms
Tms
2) TmsCl
2) NFBS
S
S
S
S
S
S
10
11
9
1) CH2(CN)2, NaH /
O
O
F
1) t-BuLi
O
O
F
F
F
NIS
AcOH-CHCl3
in THF
[Pd(PPh3)4] in THF
I
I
Tms
Tms
S
S
S
S
2) CuCl2
2) Br2 / H2O
12
13
O
O
O
F
F
F
F
70% HClO4
in CH2Cl2
NC
CN
CN
NC
NC
CN
CN
S
S
NC
S
S
2
EO-F2CPDT -TCNQ: 14
Scheme 1. Synthetic route of F2CPDT-TCNQ: 2.
O
O
O
O
1) BuLi
1) BuLi
in THF
O
O
O
O
Br
Br
H3C
H3C
Tms
CH3
Tms
CH3
H3C
I
CH3
I
in THF
NIS
S
S
in AcOH-CHCl3
2) CH3I
S
S
S
S
S
S
2) TmsCl
8
15
16
17
1) CH2(CN)2, NaH /
[Pd(PPh3)4] in THF
1) t-BuLi
in Ether
O
O
S
O O
O
O
S
CH3
CN
H3C
NC
H3C
CH3
I
H3C
CH3
NIS
in AcOH-CHCl3
I
S
2) CuCl2
S
2) Br2 / H2O
S
NC
CN
S
3) TBAF in THF
18
19
20
O
O
O
CH3
H3C
NC
70% HClO4
in CH2Cl2
CN
S
S
NC
CN
S
S
3
21
Scheme 2. Synthetic route of Me2CPDT-TCNQ: 3.
prepared by direct iodination of 18 with NIS, was allowed to
react with sodium dicyanomethanide in the presence of a cata-
lytic amount of [Pd(PPH3)4] in THF,11 followed by oxidation
with aqueous bromine to give 2,6-bis(dicyanomethylene)-
4-ethylenedioxy-3,5-dimethyl-2,6-dihydro-4H-cyclopenta[2,1-
b:3,4-b0]dithiophene (EO-Me2CPDT-TCNQ: 20) in 46% yield.
Deketalation of 20 was subsequently carried out by a reaction
with 70% perchloric acid in dichloromethane to give
(Me2CPDT-TCNQ) (3) as a violet powder in 84% yield.
Me2CPDT-TCNQ is stable in the solid state and soluble in
polar solvents such as dichloromethane, acetonitrile, THF,
and acetone.
The attempted synthesis of F2CPDT-TCNQ (2) and
Me2CPDT-TCNQ (3) starting from 4-ethylenedioxy-4H-cyclo-
penta[2,1-b:3,4-b0]dithiophene (21) was unsuccessful, since
direct or indirect 3,5-difluorination and 3,5-dimethylation of
the 2,6-dibromo or the 2,6-bis(trimethylsilyl) derivatives of
21 were unsuccessful.
Electronic Spectra and Redox Properties. The new ac-
ceptors, F2CPDT-TCNQ (2) and Me2CPDT-TCNQ (3) exhibit

1490 Bull. Chem. Soc. Jpn., 77, No. 8 (2004)
Difluoro and Dimethyl Derivatives of CPDT-TCNQ
ꢀ
ilar to the mother CPDT-TCNQ, as shown in Fig. 2. Both the
two intense ꢀ–ꢀ absorption maxima in the visible region sim-
F2CPDT-TCNQ (14) and EO-Me2CPDT-TCNQ (20) are
reduced in a two-step one-electron transfer process affording
the radical anions and dianions, the third one-electron transfer
at ꢂ1:27 and ꢂ1:43 V in F2CPDT-TCNQ and Me2CPDT-
TCNQ, respectively, should correspond to the reduction of
the carbonyl group at the central five-membered ring. The re-
duction potentials are listed in Table 1. The first half-wave re-
first (E1 = 531 nm (log " ¼ 4:47)) and the second (E2 = 500
ꢀ
nm (log " ¼ 4:37)) ꢀ–ꢀ absorptiom maxima of Me2CPDT-
TCNQ (3) showed bathochromic shifts of 11 nm from those
of 1 (E1 = 520 nm (log " ¼ 4:93), E2 = 489 nm (log " ¼
4:74)),8b while the first and the second absorptiom maxima of
F2CPDT-TCNQ (2) (E1 = 511 nm (log " ¼ 4:69), E2 = 483
nm (log " ¼ 4:50)) showed hypsochromic shifts of 9 and 6
nm, respectively, from those of 1. The bathochromic shifts in
3 are reasonable considering that the ꢀ-HOMO energy level
of 3 is destabilized by the introduction of the two electron-do-
nating methyl groups, resulting in a decrease in the HOMO–
LUMO energy splitting. The hypsochromic shift in 2 can be as-
cribed to the stabilization of the ꢀ-HOMO of 2 by the introduc-
tion of two electron-withdrawing fluorine atoms, resulting in an
increase in the HOMO–LUMO energy splitting. According to
MNDO PM-3 calculations, the HOMOs of 2 and 3 lie 0.13
eV lower and 0.15 eV higher in energy than the HOMO of 1,
red
duction potential E1 of EO-F2CPDT-TCNQ is more positive
by 0.11 V than that of EO-CPDT-TCNQ. The same trend is ob-
red
served in the E1 of 2,5-difluorotetracyano-p-quinodimethane
red
(F2TCNQ) (E1 ¼ 0:300 V vs SCE in MeCN),13 which is 0.16
red
red
V more positive than the E1 of TCNQ (E1 ¼ 0:17 V vs
SCE in MeCN).14 This fact indicates that the two fluorine atoms
in EO-F2CPDT-TCNQ contribute to the increase in the elec-
tron-accepting ability of the terminal dicyanomethylene
groups. On the other hand, the E1red of F2CPDT-TCNQ is more
negative by 0.08 V than that of CPDT-TCNQ, while the third
(a)
ꢀ
respectively.12 The absorption coefficients of the two ꢀ–ꢀ ab-
sorptiom maxima in the visible region decrease in the order of
1 > 2 > 3, suggesting that the coplanar conformation may be
preferred in this order. However, it is suggested that deviation
from the coplanar conformation is not so significant in the
3,5-disubstituted acceptor molecules, 2 and 3, since even the
dimethyl derivative 3 still has large absorption coefficients
(log " ¼ 4:47 (E1) and 4.37 (E2)).
10 µA
The electrochemical reduction of F2CPDT-TCNQ and
Me2CPDT-TCNQ occurred in three consecutive reversible
one-electron transfer processes, as shown in the cyclic voltam-
mograms listed in Fig. 3, affording stable radical anions,
dianions, and radical trianions. By considering that both EO-
+0.5
0.0
−0.5
−1.0
−1.5
V vs. SCE
(b)
5.0
10 µA
1
4.5
4.0
ε
3.5
3
3.0
2
2.5
+0.5
0.0
−0.5
−1.0
−1.5
V vs. SCE
2.0
250 300 350 400 450 500 550 600 650
Fig. 3. Cyclic voltammograms of (a) F2CPDT-TCNQ and
(b) Me2CPDT-TCNQ (1.0 mM solution with 0.1 M TBAP
in dichloromethane under argon at room temperature in
scan rate: 50 mV sꢂ1).
λ
/ nm
Fig. 2. UV–vis spectra of CPDT-TCNQ: 1, F2CPDT-
TCNQ: 2, and Me2CPDT-TCNQ: 3 in dichloromethane.
Table 1. Reduction PotentialsaÞ and Related Electrochemical Data of Acceptors
red
red
red
red
red
Compound
E1
E2
E3
ꢁE (E1 ꢂ E2
)
log Ksem
CPDT-TCNQ
F2CPDT-TCNQ
Me2CPDT-TCNQ
þ0:04
ꢂ0:04
ꢂ0:10
ꢂ0:27
ꢂ0:27
ꢂ0:33
ꢂ1:43
ꢂ1:27
ꢂ1:43
0.31
0.23
0.23
5.26
3.90
3.90
EO-CPDT-TCNQ
EO-F2CPDT-TCNQ
EO-Me2CPDT-TCNQ
ꢂ0:14
ꢂ0:03
ꢂ0:25
ꢂ0:37
ꢂ0:24
ꢂ0:36
—
—
—
0.23
0.21
0.11
3.90
3.56
1.87
a) V vs SCE, 50 mV sꢂ1, 1.0 mM in CH2Cl2.

T. Chonan et al.
Bull. Chem. Soc. Jpn., 77, No. 8 (2004) 1491
Table 2. Galvanostatic Electrochemical Reduction in Acetone and Conducting Properties of Anion Radical Salts of Me2CPDT-TCNQ
bÞ
bÞ
cÞ
dÞ
TMI
Electrolyte
Current
/mA
Period
/day
Cation
Form
C:AaÞ
ꢃCN
/cmꢂ1
ꢃCO
/cmꢂ1
ꢄr.t.
ꢄmax
T
ꢄmax
/S cmꢂ1
/S cmꢂ1
/K
/K
Me4NBF4
0.3
0.3
0.3
0.3
11
11
11
11
Me4N
Me4P
Me4As
Me4Sb
Neutral
Needle
Needle
Needle
Needle
1:2
1:2
1:2
1:2
2179
2193
2193
2189
2212
1707
1711
1711
1711
1720
0.27
12.5
84.3
71.8
—
13.0
88.1
—
—
281
254
—
—
Me4PClO4
Me4AsClO4
Me4SbClO4
ca. 240
ca. 185
—
a) Determined by the elemental analysis. b) Measured by the four probe method on a polycrystalline solid. c) The temperature showing
the maximum conductivity. d) The metal–insulator transition temperature.
red
half-wave reduction potential E3 of F2CPDT-TCNQ is more
positive by 0.16 V than that of CPDT-TCNQ. This evidence in-
102
2.5
dicates that the two fluorine atoms of F2CPDT-TCNQ contrib-
ute to the increase in the electron-accepting ability of the cen-
2.0
ρ
1.5
1.0
tral carbonyl group rather than the terminal dicyanomethylene
groups. This may be reasonable since the fluorine atoms are lo-
cated at the ꢂ-positions of the ꢁ,ꢂ-unsaturated carbonyl group.
The first reduction potentials of Me2CPDT-TCNQ and EO-
Me2CPDT-TCNQ are more negative by 0.14 and 0.11 V than
those of CPDT-TCNQ and EO-CPDT-TCNQ, respectively.
This can be ascribed to the destabilization of the energy levels
of the ꢀ-LUMOs of Me2CPDT-TCNQ and EO-Me2CPDT-
TCNQ by the introduction of the electron donating 3,5-dimeth-
yl groups. The steric hindrance of the two methyl groups in
EO-Me2CPDT-TCNQ appears to be significant since the ꢁE
3.0 3.5 4.0 4 5.0 5.5
T−1 / 10−3 K−1
101
ρ
100
200
220
240
T / K
260
280
300
Fig. 4. Temperature dependence of the resistivity for
Me4N(Me2CPDT-TCNQ)2.
red
(E1 ꢂ E2red) value as well as the log Ksem value15 of EO-
Me2CPDT-TCNQ is remarkably small, as shown in Table 1.
red
consisting of a bundle of several needles. As a consequence, the
conductivities were measured by the four probe method on the
polycrystalline solids.
Indeed, the ꢁE (E1 ꢂ E2red) value (0.31) as well as the
log Ksem value (5.26) of CPDT-TCNQ is very large, indicating
that the anion radical of CPDT-TCNQ is thermodymanically
very stable due to the widespread delocalization of the unpaired
electron over all of the extremely planar molecule.8 The ꢁE
As shown in Table 2, the Me4P, Me4As, and Me4Sb salts
showed fairly high room temperature conductivities, although
the conductivity of the Me4N salt is not so high. The ꢃCN fre-
quencies of the four salts appeared at 2179–2193 cmꢂ1, which
are lower wavenumber by 33–19 cmꢂ1 than that of neutral
Me2CPDT-TCNQ (2212 cmꢂ1). The ꢃCO frequencies of the
salts also appeared at a lower wavemumber region than that
of neutral Me2CPDT-TCNQ (1720 cmꢂ1). Although we have
no data on the ꢃCN and ꢃCO frequencies of the fully ionic
Me2CPDT-TCNQ dianion, the Me4P and Me4As salts should
at least exist in a partial CT state, since these salts showed
metallic behavior as described below.
The resistivity of the polycrystalline Me4N salt showed a
semiconducting temperature dependence from room tempera-
ture down to 193 K, as shown in Fig. 4. However, the activation
energy obtained by the Arrhenius plot (Ea ¼ 51 meV in the
temperature region) is fairly small.
red
(E1 ꢂ E2red) values as well as the log Ksem values of
F2CPDT-TCNQ and Me2CPDT-TCNQ are relatively small
when compared with those of CPDT-TCNQ, indicating that
the extent of the delocalization of the unpaired electron is less
in the anion radicals of the 3,5-disubstituted derivatives than
in the anion radical of unsubstituted CPDT-TCNQ, probably
due to the less planar conformations of the 3,5-disubstituted
derivatives. However, the deviation from the coplanarity in
F2CPDT-TCNQ and Me2CPDT-TCNQ seems to not be so
significant as that in EO-Me2CPDT-TCNQ, since the log Ksem
values of F2CPDT-TCNQ (3.90) and Me2CPDT-TCNQ
(3.90) are more than twice as large as that of EO-Me2CPDT-
TCNQ (1.87).
Conducting Properties of Anion Radical Salts.
Me2CPDT-TCNQ formed anion radical salts on conventional
electrochemical crystallization in acetone in the presence of
an electrolyte under a constant current by using an H-type cell.
The conditions of the electrochemical crystallization are shown
in Table 2. We have obtained four anion radical salts with the
molecular formula Me4X(Me2CPDT-TCNQ)2 (X = N, P, As,
and Sb). The stoichiometries and room temperature conductiv-
ities as well as the ꢃCN and ꢃCO frequencies of the salts are also
summarized in Table 2. In spite of many efforts to find out the
conditions to grow single crystals of good quality, we have not
succeeded in preparing large size single crystals for crystallo-
graphic analysis, but rather have obtained polycrystalline solids
On the other hand, as described above, the resistivity of
Me4P(Me2CPDT-TCNQ)2 showed a metallic temperature de-
pendence from room temperature down to around 283 K, and
the conductivity reached a maximum value of 13.0 S cmꢂ1 at
T
¼ 281 K, as shown in Fig. 5. After passing through the
ꢄmax
maximum, the metallic state became unstable and transferred
to the first semiconducting phase with Ea1 ¼ 18 meV in the
temperature region from 230 K down to 170 K, and then trans-
ferred to the second semiconducting phase with Ea2 ¼ 67 meV
in the temperature region from 120 K down to 85 K. The acti-
vation energies were obtained from the Arrhenius plots of the
temperature dependence of the resistivity, as shown in Fig. 6.

1492 Bull. Chem. Soc. Jpn., 77, No. 8 (2004)
Difluoro and Dimethyl Derivatives of CPDT-TCNQ
101
100
101
7.9
1.4
254 K
1.2
7.8
281 K
100
ρ
ρ
7.7
1.0
250 260 270 280 290 300
200 220 240 260 280 300
ρ
T / K
ρ
T / K
10−1
10−2
10−1
50
50
100
150
200
250
300
100
150
200
250
300
T / K
T / K
Fig. 7. Temperature dependence of the resistivity for
Me4As(Me2CPDT-TCNQ)2.
Fig. 5. Temperature dependence of the resistivity for
Me4P(Me2CPDT-TCNQ)2.
1
0
2
1
0
−1
−2
ρ
ρ
−1
−3
Ea = 67 meV
Ea = 81 meV
−2
−3
−4
Ea = 21 meV
Ea = 18 meV
−5
2
4
6
8
10
12
2
4
6
8
10
12
T
−1 / 10−3 K−1
T
−1 / 10−3 K−1
Fig. 8. Arrhenius plot of the temperature dependence of the
resistivity for Me4As(Me2CPDT-TCNQ)2.
Fig. 6. Arrhenius plot of the temperature dependence of the
resistivity for Me4P(Me2CPDT-TCNQ)2.
101
The temperature dependence of the resistivity of Me4As-
(Me2CPDT-TCNQ)2 is shown in Fig. 7. It is also metallic from
room temperature down to around 240 K, and the conductivity
2
0
reached a maximum value of 88.1 S cmꢂ1 at T
¼ 254 K.
100
−2
ꢄmax
ρ
The activation energy of the first semiconducting phase ob-
tained by the Arrhenius plot was Ea1 ¼ 21 meV in the temper-
ature region from 210 K down to 180 K. The activation energy
of the second semiconducting phase is Ea2 ¼ 81 meV in the
temperature region from 150 K down to 100 K, as shown in
Fig. 8.
−4
8
2
4
6
10 12
−1 / 10−3 K−1
ρ
T
10−1
10−2
The resistivity of Me4Sb(Me2CPDT-TCNQ)2 exhibited a
semiconducting temperature dependence from room tempera-
ture down to 85 K, as shown in Fig. 9. The activation energy
obtained by the Arrhenius plot was Ea ¼ 72 meV in the temper-
ature region from room temperature down to 110 K.
50
100
150
200
250
300
T / K
Fig. 9. Temperature dependence of the resistivity for
Me4Sb(Me2CPDT-TCNQ)2.
Me4X(CPDT-TCNQ)2 (X = P and As) also have the first in-
sulating phase, adjacent to the metallic phase, with a small ac-
tivation energy, and the second insulating phase with a relative-
ly large activation energy at lower temperature regions.16
Therefore, the profiles of the existence of the first and second
insulating phases, and the small and large activation energies
of the respective phases in Me4X(Me2CPDT-TCNQ)2 (X = P
and As) closely resemble the cases of Me4X(CPDT-TCNQ)2
(X = P and As). Moreover, it has already been proven that
the CPDT-TCNQ molecule has a very strong tendency to main-
tain its characteristic molecular packing motif shown in Fig. 1
in the crystal structure of anion radical salts, even when the size
or structure of the cation changes.17 Moreover, ꢀAO coeffi-
cients as well as the bonding and antibonding orbital symmetry
in the LUMO of Me2CPDT-TCNQ obtained from MNDO PM-
3 calculations closely resemble those of CPDT-TCNQ. There-
fore, although the crystal structures of Me4X(Me2CPDT-
TCNQ)2 (X = N, P, As, and Sb) have not been determined,
we can speculate that these salts may have a similar molecular
packing motif as those of Me4X(CPDT-TCNQ)2 (X = N, P, As,
and Sb), respectively, except for the sheet-like network along
the side-by-side direction, which should disappear in the salts
of the 3,5-dimethyl derivative due to the lack of the inter-
column O H contacts.
The resistivity of Me4N(Me2CPDT-TCNQ)2 showed a semi-
conducting temperature dependence from room temperature,
ꢁꢁꢁ

T. Chonan et al.
Bull. Chem. Soc. Jpn., 77, No. 8 (2004) 1493
decoupling and two-dimensional carbon–proton chemical shift
correlation experiments. FT-IR spectra were recorded on a
HORIBA FT-300 spectrometer with a KBr disk method. Mass
spectra were recorded on a JEOL HX-100 or a HITACHI M-
2500S spectrometer. Electronic absorption spectra were recorded
on a HITACHI U-3210 spectrometer. The cyclic voltammograms
were taken on a BAS CV-50W under argon atmosphere at room
temperature. The conductivities of the anion radical salts were
measured by the four-probe method on using a YOKOGAWA
7651 programmable direct current source and a KEITHLEY
2001 digital multimeter unit on a polycrystalline solid. Gold wires
(10 or 15 mm diameter) were attached to the polycrystalline solid
with carbon paste.
even though Me4N(CPDT-TCNQ)2 is metallic down to 130 K.
Therefore, the metallic state of Me4N(Me2CPDT-TCNQ)2 is
significantly destabilized compared with that of Me4N-
(CPDT-TCNQ)2. On the other hand, the destabilization of the
metallic state is not so significant in Me4P(Me2CPDT-TCNQ)2
and Me4As(Me2CPDT-TCNQ)2, since the conductivity of both
of these salts showed a metallic temperature dependence,
although the T
of Me4P(Me2CPDT-TCNQ)2 was higher
of
ꢄmax
by 61 K than that of Me4P(CPDT-TCNQ)2 and the T
ꢄmax
Me4As(Me2CPDT-TCNQ)2 was higher by 79 K than that of
Me4As(CPDT-TCNQ)2. It seems difficult to explain why the
metallic state of Me4N(Me2CPDT-TCNQ)2 is significantly
more destabilized than the metallic states of Me4X-
(Me2CPDT-TCNQ)2 (X = P and As) only based on the differ-
ence in the quality of the crystals, since all three of these poly-
crystalline samples of the Me2CPDT-TCNQ salts exhibit a
metallic luster and are similar in shape under a microscope.
The MI transition mechanisms have been proven to be a 2kF
CDW instability for Me4N(CPDT-TCNQ)2 and 4kF CDW in-
stabilities for Me4X(CPDT-TCNQ)2 (X = P and As).9 The pa-
rameter for determing either the 2kF or 4kF CDW grawings for
the CPDT-TCNQ salts has been ascribed to the degree of dime-
rization, since strong dimerization enhances the effect of the
Coulomb interaction, which enhances the 4kF CDW instability.
Therefore, from the fact that the metallic state of the Me4N salt
is significantly less stable than the metallic states of the Me4P
and Me4As salts, it may be possible to speculate that the origin
of the MI transition in Me4N(Me2CPDT-TCNQ)2 may be 2kF
CDW instability, which occurred at around room temperature,
and the origins of the MI transitions in Me4X(Me2CPDT-
TCNQ)2 (X = P and As) may be 4kF CDW, because the 4kF
CDW instability is generally much less common than the 2kF
CDW instability. Although we cannot deduce any critical con-
clusions at this stage due to the lack of crystal structural data of
Me4X(Me2CPDT-TCNQ)2 (X = N, P, and As), the conducting
properties of Me4X(Me2CPDT-TCNQ)2 (X = N, P, and As)
suggest that these salts may have a similar molecular packing
motif as those of Me4X(CPDT-TCNQ)2 (X = N, P, and As),
and the one-dimensional metallic states may be destabilized
by the lack of the inter-column sheet-like network along the
side-by-side direction. In this case, the extent of the destabiliza-
tion would be much more significant in Me4N(Me2CPDT-
TCNQ)2, if the origin of the MI transition of the Me4N salt
is a 2kF CDW instability. Preparations of single crystals in
good quality and determination of the crystal structures are in
progress.
Bis(4-bromo-3-thienyl)methanol (6). To a hexane solution of
butyllithium (1.66 M (1 M = 1 mol dmꢂ3) solution, 4.40 mL, 7.30
ꢃ
mmol) cooled at ꢂ78 C, a solution of 3,4-dibromothiophene (4)
(1.72 g, 7.11 mmol) in anhydrous ether (12 mL) was added drop-
wise with stirring at ꢂ78 ꢃC over a period of 1 min and this reac-
tion mixture was stirred for 30 min at ꢂ78 ꢃC under argon atmos-
phere. To this was added dropwise a solution of 4-bromo-3-thio-
phenecarbaldehyde (5)10 (1.4ꢃ3 g, 7.46 mmol) in anhydrous ether
(6 mL) with stirring at ꢂ78 C over a period of 5 min, and this
reaction mixture was stirred for 30 min at ꢂ78 ꢃC. After being
warmed to room temperature, the reaction mixture was poured into
1 M hydrochloric acid and extracted with ether. The ether extract
was washed with water and then brine, and was then dried over
Na2SO4. Solvent evaporation from the extract gave a residue
(2.59 g), which was chromatographed on basic alumina by eluting
with ether to give a yellow oil (5.23 g, 4.79 mmol, 70%): 1H NMR
(CDCl3, 200 MHz) ꢅ 7.31 (2H, d, J2;5 ¼ 3:5 Hz, H-5), 7.18 (2H,
dd, J2;5 ¼ 3:5 Hz, J2;CHOH ¼ 0:7 Hz, H-2), 5.95 (1H, dd, JCH,OH
¼
4:3 Hz, J2;CHOH ¼ 0:7 Hz, CHOH), 2.50 (1H, d, JCH,OH ¼ 4:3 Hz,
OH); 13C NMR (CDCl3, 150 MHz) ꢅ 141.5 (C-3), 124.1 (C-2),
124.0 (C-5), 110.4 (C-4), 67.5 (CHOH); IR (neat) 3564, 3320,
3111, 2925, 2875, 1518, 1425, 1377, 1352, 1284, 1261, 1157,
1041, 1003, 962, 881, 852, 802, 768, 714, 658 cmꢂ1; HRMS (EI,
110 eV) m=z 351.8232 (Mþ) (Calcd for C9H6Br2OS2: 351.8227).
Found: C, 30.44; H, 1.98; Br, 44.95%. Calcd for C9H6Br2OS2:
C, 30.53; H, 1.71; Br, 45.13%.
Bis(4-bromo-3-thienyl) Ketone (7). To a solution of 6 (1.94 g,
5.47 mmol) in acetic acid (20 mL) was added dropwise a solution
of chromium trioxide (547 mg, 5.47 mmol) disolved in the mixture
of acetic acid (10 mL) and water (4 mL) with stirring at room tem-
perature over a period of 30 min. Then the reaction mixture was
stirred for 6 h at room temperature. The reaction mixture was ex-
tracted with ether. The ether extract was washed successively with
an aqueous NaHCO3 solution, water, and then brine, and was then
dried over Na2SO4. Solvent evaporation from the extract gave a
dark yellow oil (1.85 g), which was chromatographed on silica
gel by eluting with toluene to give bis(4-bromo-3-thienyl) ketone
(7) (1.76 g, 5.00 mmol, 92%) as pale yellow plates: mp 84–85
ꢃC; 1H NMR (CDCl3, 200 MHz) ꢅ 7.77 (2H, d, J2;5 ¼ 3:5 Hz, H-
2), 7.38 (2H, d, J5;2 ¼ 3:5 Hz, H-5); 13C NMR (CDCl3, 150
MHz) ꢅ 182.3 (CO), 139.3 (C-3), 134.1 (C-2), 125.5 (C-5),
110.6 (C-4); IR (KBr) 3097, 1672, 1637, 1485, 1415, 1365,
1340, 1257, 1219, 1134, 1038, 957, 879, 854, 808, 766, 688, 648
cmꢂ1; MS (DEI, 70 eV) m=z (rel intensity) 354 (Mþ + 4,
34.48), 352 (Mþ + 2, 60.97), 350 (Mþ, 30.40), 273 (Mþ + 2 ꢂ
Br, 71.42), 271 (Mþ ꢂ Br, 64.86), 192 (Mþ ꢂ 2Br, 45.19), 191
(C5H2BrOS + 2, 100), 189 (C5H2BrOS, 97.7); HRMS m=z
349.8068 (Mþ) (Calcd for C9H4Br2OS2: 349.8070). Found: C,
31.11; H, 1.42; Br, 45.07%. Calcd for C9H4Br2OS2: C, 30.70; H,
Experimental
General. All synthetic reactions were carried out under an ar-
gon atmosphere. All chemicals and solvents were dried well and
solvents were freshly distilled before use. Column chromatography
was carried out with silica gel (150–425 mm). Melting points were
determined with a Yanagimoto micro melting point apparatus MP-
J3, and are not corrected. Elemental analyses were performed at the
Instrumental Analysis Center for Chemistry, Tohoku University.
1H NMR spectra and 13C NMR spectra were recorded on a Bruker
AC-200P spectrometer or AM-600 spectrometer and chemical
shifts are recorded in ꢅ relative to tetramethylsilane as an internal
standard. Chemical shift assignments were confirmed through spin

1494 Bull. Chem. Soc. Jpn., 77, No. 8 (2004)
Difluoro and Dimethyl Derivatives of CPDT-TCNQ
1.15; Br, 45.39%.
with chloroform. The chloroform extract was washed successively
with aqueous Na2SO3, water, and then brine, and was then dried
over Na2SO4. Solvent evaporation from the extract gave a crude
product (469 mg), which was chromatographed on silica gel by
eluting with toluene to give 2,2-bis(4-fluoro-5-iodo-3-thienyl)-
1,3-dioxolane (10) as colorless plates (428 mg, 89%): mp 117–
118 ꢃC; 19F NMR (CDCl3, 188 MHz) ꢅ ꢂ119:7 (d, JH,F ¼ 4:1
2,2-Bis(4-bromo-3-thienyl)-1,3-dioxolane (8). A solution of 7
(1.65 g, 4.67 mmol), p-toluenesulfonic acid (89 mg, 0.47 mmol),
and ethylene glycol (2.60 mL, 46.6 mmol) in benzene (50 mL)
was heated to reflux under a Dean–Stark head for 5 days under ar-
gon atmosphere. After being cooled to room temperature, the reac-
tion mixture was poured into aqueous NaHCO3 and extracted with
benzene. The benzene extract was washed with water and then
brine, and was then dried over Na2SO4. Solvent evaporation from
the extract gave a crude product, which was chromatographed on
basic alumina by eluting with toluene to give pure 2,2-bis(4-bro-
mo-3-thienyl)-1,3-dioxolane (8) (1.81 g, 4.57 mmol, 98%) as col-
orless prisms: mp 170.0–170.5 ꢃC; 1H NMR (CDCl3, 200 MHz) ꢅ
7.51 (2H, d, J2;5 ¼ 3:70 Hz, H-2), 7.27 (2H, d, J5;2 ¼ 3:70 Hz, H-
5), 4.16 (4H, s, OCH2CH2O); 13C NMR (CDCl3, 150 MHz) ꢅ
138.5 (C-3), 126.8 (C-2), 125.2 (C-5), 109.1 (C-4), 105.4 (OCO),
65.3 (OCH2CH2O); IR (KBr) 3107, 2981, 2937, 2881, 2852,
1545, 1510, 1466, 1408, 1192, 1159, 1092, 1043, 1007, 951,
885, 858, 806, 727, 658 cmꢂ1; UV (MeCN) ꢆ/nm (log ") 250.1
(sh, 3.89), 245.4 (3.96), 227.6 (sh, 3.82); MS (DEI, 70 eV) m=z
(rel intensity) 398 (Mþ + 4, 17.77), 396 (Mþ + 2, 29.25), 394
(Mþ, 15.04), 317 (Mþ + 2 ꢂ Br, 7.15), 315 (Mþ ꢂ Br, 7.15),
191 (C5H2BrOS + 2, 100), 189 (C5H2BrOS, 87); HRMS m=z
393.8329 (Mþ) (Calcd for C11H8Br2O2S2: 393.8332). Found: C,
33.31; H, 2.13; S, 16.00; Br, 40.22%. Calcd for C11H8Br2O2S2:
C, 33.35; H, 2.04; S, 16.19; Br, 40.34%.
1
Hz); H NMR (CDCl3, 600 MHz) ꢅ 7.52 (2H, d, JH,F ¼ 5:0 Hz,
H-2), 4.14 (4H, s, OCH2CH2O); 13C NMR (CDCl3, 150 MHz) ꢅ
157.3 (C-4), 130.2 (C-3), 128.3 (C-2), 102.9 (OCO), 65.7
(OCH2CH2O), 55.5 (C-5); IR (KBr) 3132, 2956, 2887, 1556,
1450, 1398, 1203 1178, 1153, 1059, 1030, 1007, 964, 945, 850,
787, 768, 737, 708 cmꢂ1; HRMS (EI, 110 eV) m=z 525.7864
(Mþ) (Calcd for C11H4F2I2O2S2: 525.7867). Found: C, 24.98; H,
0.91; I, 48.18%. Calcd for C11H4F2I2O2S2: C, 25.21; H, 0.77; I,
48.43%.
2,2-Bis(4-fluoro-5-trimethylsilyl-3-thienyl)-1,3-dioxolane
(11). To a solution of 10 (424 mg, 0.806 mmol) in anhydrous THF
(25 mL) was added dropwise a hexane solution of butyllithium
ꢃ
(1.59 M solution, 1.05 mL, 1.67 mmol) with stirring at ꢂ78 C
under argon atmosphere. Then this reaction mixture was stirred
ꢃ
at ꢂ78 C for 30 min. To this was added dropwise trimethylsilyl
chloride (0.410 mL, 3.22 mmol) at ꢂ78 ꢃC, and this resulting
ꢃ
reaction mixture was stirred at ꢂ78 C for 1 h. After warming to
room temperature, the reaction mixture was poured into aqueous
NaHCO3 and extracted with ether. The ether extract was washed
successively with water and then brine, and was then dried over
Na2SO4. Solvent evaporation from the dried extract gave a residue,
which was chromatographed on silica gel by eluting with a mixture
of toluene–hexane (1:1, v/v) to give pure 2,2-bis(4-fluoro-5-tri-
methylsilyl-3-thienyl)-1,3-dioxolane (11) as colorless plates (232
2,2-Bis(4-fluoro-3-thienyl)-1,3-dioxolane (9). To a solution of
8 (300 mg, 0.757 mmol) in anhydrous THF (5 mL) was added
dropwise a hexane solution of butyllithium (1.66 M solution,
1.00 mL, 1.66 mmol) with stirring at ꢂ78 C under argon atmos-
ꢃ
phere, and this reaction mixture was stirred for 30 min at ꢂ78 ꢃC.
To this was added dropwise a solution of N-fluorobenzenesulfoni-
mide (NFBS) (573 g, 1.82 mmol) in anhydrous THF (6 mL) at ꢂ78
ꢃC over a period of 10 min, and then this reaction mixture was stir-
red for 1 h at ꢂ78 ꢃC. After a mixture of water (1 mL) and THF (1
mL) was added to the reaction mixture at ꢂ78 ꢃC, this resulting re-
action mixture was warmed to room temperature, then poured into
aqueous Na2SO3, and then extracted with ether. The ether extract
was washed with water and then brine, and was then dried over
Na2SO4. Solvent evaporation from the extract gave a crude product
(243 mg), which was chromatographed on silica gel by eluting with
toluene to give colorless crystals (161 mg, 78%). Further recrystal-
lization from ethanol gave 2,2-bis(4-fluoro-3-thienyl)-1,3-dioxo-
lane (9) as colorless plates (89 mg, 43%): mp 107–108 ꢃC;
19F NMR (CDCl3, 188 MHz) ꢅ ꢂ129:4 (br.d, JH,F ¼ 3:2 Hz);
ꢃ
mg, 69%): mp 72–73 C; 19F NMR (CDCl3, 188 MHz) ꢅ ꢂ120:1
(d, JH,F ¼ 3:4 Hz); 1H NMR (CDCl3, 200 MHz) ꢅ 7.42 (2H, d,
JH,F ¼ 3:5 Hz, H-2), 4.13 (4H, s, OCH2CH2O), 0.31 (18H, s,
SiMe3); IR (KBr) 3114, 2956, 2893, 1549, 1439, 1400, 1252,
1192, 1171, 1066, 984, 947, 872, 841, 758, 719, 694, 638, 613,
513 cmꢂ1; MS (DEI, 70 eV) m=z (rel intensity) 420 (Mþ + 2,
5.49), 419 (Mþ + 1, 8.22), 418 (Mþ, 27.29), 403 (Mþ ꢂ Me,
15.25), 245 (Mþ ꢂ C4HFSSiMe3, 100); HRMS (EI, 110 eV)
m=z 418.0739 (Mþ) (Calcd for C17H24F2O2S2Si2: 418.0724).
Found: C, 48.52; H, 5.99%. Calcd for C17H24F2O2S2Si2: C,
48.77; H, 5.78%.
4-Ethylenedioxy-3,5-difluoro-2,6-bis(trimethylsilyl)-4H-cy-
clopenta[2,1-b:3,4-b0]dithiophene (12). To an anhydrous THF (8
mL) solution of 11 (125 mg, 0.299 mmol) was added dropwise t-
butyllithium (1.64 M pentane solution, 0.44 mL, 0.656 mmol) with
stirring at ꢂ78 ꢃC under argon atmosphere. After the reaction mix-
ture was stirred for 30 min at ꢂ78 ꢃC under argon atmosphere, cop-
per(II) chloride (212 mg, 1.58 mmol) was added and then the reac-
tion mixture was stirred for another 30 min at ꢂ78 ꢃC. After being
warmed to room temperature, the reaction mixture was stirred for 3
h at room temperature. The inorganic precipitate was removed by
filtration through a glass disk and the filtrate was poured into aque-
ous NaHCO3 and then extracted with ether. The ether extract was
washed with water and then brine, and then was dried over
Na2SO4. Solvent evaporation gave a residue (123 mg), which
was chromatographed on silica gel by eluting with a mixture of tol-
uene–hexane (1:2, v/v) to give 12 as colorless plates (51 mg, 41%):
mp 146–147 ꢃC; 19F NMR (CDCl3, 188 MHz) ꢅ ꢂ124:5 (s);
1H NMR (CDCl3, 200 MHz) ꢅ 0.32 (18H, s, SiMe3), 4.28 (4H, s,
OCH2CH2O); IR (KBr) 2956, 2895, 1506, 1460, 1396, 1250,
1221, 1182, 1105, 1012, 991, 974, 949, 845, 760 cmꢂ1; MS
1H NMR (CDCl3, 200 MHz) ꢅ 7.29 (2H, dd, JH,H ¼ 3:8 Hz, JH,F
¼
3:8 Hz, H-2), 6.72 (2H, dd, JH,H ¼ 3:8 Hz, JH,F ¼ 1:0 Hz, H-5),
4.14 (4H, s, OCH2CH2O); 13C NMR (CDCl3, 150 MHz) ꢅ 155.0
(C-4), 130.5 (C-3), 123.3 (C-2), 105.1 (C-5), 104.0 (OCO), 65.5
(OCH2CH2O); IR (KBr) 3113, 3068, 1562, 1456, 1410, 1203,
1144, 1086, 1055, 1028, 1003, 947, 928, 827, 742, 690, 633,
592, 565 cmꢂ1; UV (MeCN) ꢆ/nm (log ") 238.8 (4.02), 226.0
(sh, 3.99); HRMS (EI, 110 eV) m=z 273.9933 (Mþ) (Calcd for
C11H8F2O2S2: 273.9934). Found: C, 47.89; H, 3.10%. Calcd for
C11H8F2O2S2: C, 48.16; H, 2.94%.
2,2-Bis(4-fluoro-5-iodo-3-thienyl)-1,3-dioxolane (10). To a
solution of 9 (250 mg, 0.91 mmol) in a mixture of chloroform
(10 mL) and acetic acid (10 mL) was added NIS (450 mg, 2.00
mmol) with stirring at room temperature under argon atmosphere.
Then, this resulting reaction mixture was stirred for 2 h at 60 C.
After cooling to room temperature, the reaction mixture was pour-
ed into aqueous NaHCO3, and the resulting solution was extracted
ꢃ

T. Chonan et al.
Bull. Chem. Soc. Jpn., 77, No. 8 (2004) 1495
(DEI, 70 eV) m=z (rel intensity) 419 (Mþ + 3, 5.05), 418 (Mþ + 2,
19.78), 417 (Mþ + 1, 29.35), 416 (Mþ, 100); HRMS (EI, 110 eV)
m=z 416.0564 (Mþ) (Calcd for C17H22F2O2S2Si2: 416.0568).
Found: C, 48.78; H, 5.42%. Calcd for C17H22F2O2S2Si2: C,
49.01; H, 5.32%.
Na2SO4. Solvent evaporation from the extract gave a crude product
(9.3 mg), which was chromatographed on silica gel by eluting
with dichloromethane to give 2,6-bis(dicyanomethylene)-3,5-di-
fluoro-2,6-dihydro-4H-cyclopenta[2,1-b:3,4-b0]dithiophen-4-one
(F2CPDT-TCNQ: 2) as a violet powder (4.0 mg, 37.6%): mp > 300
ꢃC; 19F NMR (CDCl3, 188 MHz) ꢅ ꢂ112:7 (s); IR (KBr) 2216,
1722, 1576, 1510, 1460, 1342, 1286, 1221, 1142, 1078, 1016,
889 cmꢂ1; UV–vis (CH2Cl2) ꢆ/nm (log ") 511 (4.69), 483
(4.50), 448 (sh, 4.03), 353 (2.62), 337 (2.65), 304 (2.46), 288
(2.52); HRMS (EI, 110 eV) m=z 353.9487 (Mþ) (Calcd for
C15F2N4OS2: 353.9481). Found: C, 50.77; N, 15.97%. Calcd for
C15F2N4O2S2: C, 50.85; N, 15.81%.
4-Ethylenedioxy-3,5-difluoro-2,6-diiodo-4H-cyclopenta[2,1-
b:3,4-b0]dithiophene (13). To a solution of 12 (120 mg, 0.288
mmol) in a mixture of anhydrous chloroform (6 mL) and acetic
acid (6 mL) was added NIS (143 mg, 0.636 mmol) with stirring
at room temperature under argon atmosphere. Then, this resulting
reaction mixture was stirred for 2 h at room temperature, and was
then poured into aqueous Na2SO3. The resulting mixture was ex-
tracted with chloroform. The chloroform extract was washed suc-
cessively with aqueous NaHCO3, water, and then brine, and was
then dried over Na2SO4. Solvent evaporation gave a crude product,
which was chromatographed on silica gel by eluting with a mixture
of toluene–hexane (1:1, v/v) to give pure 4-ethylenedioxy-3,5-
difluoro-2,6-diiodo-4H-cyclopenta[2,1-b:3,4-b0]dithiophene (13)
as yellow needles (141 mg, 93.4%): mp 258–259 ꢃC (decomp);
19F NMR (CDCl3, 188 MHz) ꢅ ꢂ124:0 (s); 1H NMR (CDCl3,
200 MHz) ꢅ 4.27 (4H, s, OCH2CH2O); IR (KBr) 1527, 1452,
2,2-Bis(4-methyl-3-thienyl)-1,3-dioxolane (15). To a solution
of 8 (500 mg, 1.262 mmol) in anhydrous THF (20 mL) was added
dropwise a hexane solution of butyllithium (1.54 M solution, 1.72
mL, 2.649 mmol) with stirring at ꢂ78 ꢃC under argon atmosphere.
ꢃ
Then this reaction mixture was stirred for 30 min at ꢂ78 C. To
this was added dropwise methyl iodide (0.39 mL, 889 mg, 6.265
mmol) at ꢂ78 ꢃC, and this reaction mixture was stirred for 1 h
at ꢂ78 ꢃC. After a mixture of water (1 mL) and THF (2 mL)
was added to the reaction mixture at ꢂ78 ꢃC, the reaction mixture
was warmed to room temperature, then poured into aqueous
Na2SO3 and extracted with ether. The ether extract was washed
with aqueous NaHCO3, water, and then brine, and was then dried
over Na2SO4. Solvent evaporation from the dried extract gave col-
orless fine crystals (358 mg), which were chromatographed on sili-
ca gel by eluting with toluene to give 2,2-bis(4-methyl-3-thienyl)-
1,3-dioxolane (15) as colorless plates (333 mg, 99%): mp 141–142
ꢃC; 1H NMR (CDCl3, 600 MHz) ꢅ 7.27 (2H, d, J2;5 ¼ 3:3 Hz, H-2),
6.88 (2H, dq, J5;2 ¼ 3:3 Hz, J5,Me ¼ 1:0 Hz, H-5), 4.07 (4H, s,
OCH2CH2O), 2.12 (6H, d, JMe,5 ¼ 1:0 Hz, Me); 13C NMR (CDCl3,
150 MHz) ꢅ 140.4 (C-4), 136.7 (C-3), 125.0 (C-2), 122.8 (C-5),
107.0 (OCO), 64.7 (OCH2CH2O), 15.3 (Me); IR (KBr) 3122,
3097, 2931, 2883, 1456, 1375, 1205, 1171, 1146, 1049, 984,
949, 922, 864, 822, 700 cmꢂ1; UV (MeCN) ꢆ/nm (log ") 241.8
(4.02); MS (DEI, 110 eV) m=z (rel intensity) 268 (Mþ + 2,
5.95), 267 (Mþ + 1, 8.91), 266 (Mþ, 52.06), 169 (Mþ ꢂ C5H5S,
100); HRMS (EI, 110 eV) m=z 266.0435 (Mþ) (Calcd for
C13H14O2S2: 266.0435). Found: C, 58.60; H, 5.25%. Calcd for
C13H14O2S2: C, 58.62; H, 5.30%.
1240, 1213, 1092, 1028, 999, 945, 916, 843, 573, 544 cmꢂ1
;
HRMS (EI, 110 eV) m=z 523.7705 (Mþ) (Calcd for
C11H4F2I2O2S2: 523.7711). Found: C, 24.92; H, 0.96; I, 48.22%.
Calcd for C11H4F2I2O2S2: C, 25.21; H, 0.77; I, 48.43%.
2,6-Bis(dicyanomethylene)-4-ethylenedioxy-3,5-difluoro-2,6-
dihydro-4H-cyclopenta[2,1-b:3,4-b0]dithiophene (EO-F2CPDT-
TCNQ: 14). To a suspension of sodium hydride (60 wt %, 18.0
mg, 0.450 mmol) in anhydrous THF (1 mL) was added dropwise
a solution of malononitrile (15.0 mg, 0.227 mmol) in anhydrous
THF (1 mL) at room temperature under argon atmosphere. Then,
this reaction mixture was stirred for 10 min at room temperature.
To this were added successively a solution of 13 (30.0 mg,
0.0572 mmol) in anhydrous THF (1 mL) and [Pd(PPh3)4] (13.0
mg, 0.0112 mmol). This reaction mixture was heated at reflux
for 4 h and then cooled to room temperature with stirring. The re-
action mixture was poured into a mixture of bromine (0.2 mL) and
water (20 mL). Then, this resulting mixture was poured into aque-
ous Na2SO3 water and extracted with dichloromethane. The di-
chloromethane extract was washed successively with aqueous
NaHCO3, water, and then brine, and was then dried over Na2SO4.
Solvent evaporation from the dried extract gave a crude product,
which was chromatographed on silica gel by eluting with dichloro-
methane to give pure 2,6-bis(dicyanomethylene)-4-ethylenedioxy-
3,5-difluoro-2,6-dihydro-4H-cyclopenta[2,1-b:3,4-b0]dithiophene
(EO-F2CPDT-TCNQ: 14) as a violet powder (15.6 mg, 68%): mp
2,2-Bis(5-iodo-4-methyl-3-thienyl)-1,3-dioxolane (16). To a
solution of 15 (1000 mg, 3.754 mmol) in a mixture of chloroform
(40 mL) and acetic acid (40 mL) was added NIS (1860 mg, 8.267
mmol) with stirring at room temperature under argon atmosphere.
Then this reaction mixture was stirred for 3 h at room temperature.
The reaction mixture was then poured into aqueous Na2SO3, and
the resulting solution was extracted with chloroform. The chloro-
form extract was washed successively with aqueous NaHCO3, wa-
ter, and brine, and was then dried over Na2SO4. Solvent evapora-
tion from the dried extract gave a reddish oil (1944 mg), which was
chromatographed on silica gel by eluting with a mixture of toluene
and hexane (1:1, v/v) to give 2,2-bis(5-iodo-4-methyl-3-thienyl)-
1,3-dioxolane (16) as colorless plates (1557 mg, 80%): mp 121–
122 ꢃC; 1H NMR (CDCl3, 600 MHz) ꢅ 7.45 (2H, s, H-2), 4.06
(4H, s, OCH2CH2O), 2.08 (6H, s, Me); 13C NMR (CDCl3, 150
MHz) ꢅ 140.8 (C-3), 139.7 (C-4), 129.8 (C-2), 105.8 (OCO),
77.6 (C-5), 64.8 (OCH2CH2O), 17.5 (Me); IR (KBr) 3101, 2885,
1535, 1448, 1429, 1375, 1190, 1167, 1147, 1053, 1024, 987,
947, 914, 843, 781, 706 cmꢂ1; UV (MeCN) ꢆ/nm (log ") 247.8
(4.25); MS (DEI, 110 eV) m=z (rel intensity) 520 (Mþ + 2,
4.02), 519 (Mþ + 1, 7.65), 518 (Mþ, 45.27), 295 (Mþ ꢂ C5H4IS,
100); HRMS (EI, 110 eV) m=z 517.8367 (Mþ) (Calcd for
ꢃ
1
> 300 C; 19F NMR (CDCl3, 188 MHz) ꢅ ꢂ123:9 (s); H NMR
(CDCl3, 200 MHz) ꢅ 4.37 (4H, s, OCH2CH2O); IR (KBr) 2222,
1693, 1639, 1514, 1383, 1288, 1211, 1182, 1032, 997, 941
cmꢂ1; MS (DEI, 70 eV) m=z (rel intensity) 400 (Mþ + 2,
12.18), 399 (Mþ + 1, 22.12), 398 (Mþ, 100), 354 (F2CPDT-
TCNQþ, 17.87); HRMS (EI, 110 eV) m=z 397.9749 (Mþ) (Calcd
for C17H4F2N4O2S2: 397.9744). Found: C, 51.08; H, 1.24; N,
13.83%. Calcd for C17H4F2N4O2S2: C, 51.26; H, 1.01; N, 14.06%.
2,6-Bis(dicyanomethylene)-3,5-difluoro-2,6-dihydro-4H-cy-
clopenta[2,1-b:3,4-b0]dithiophen-4-one (F2CPDT-TCNQ: 2).
To a solution of 14 (12.0 mg, 0.0301 mmol) in dichloromethane
(4 mL) was added 70% perchloric acid (1 mL) at 0 ꢃC. After vig-
orous stirring at room temperature for 6 h, the reaction mixture was
poured into ice-water. The resulting mixture was extracted with
dichloromethane. The dichloromethane extract was washed with
aqueous NaHCO3, water, and then brine, and was then dried over

1496 Bull. Chem. Soc. Jpn., 77, No. 8 (2004)
Difluoro and Dimethyl Derivatives of CPDT-TCNQ
C13H12I2O2S2: 517.8369). Found: C, 29.97; H, 2.57; I, 48.71%.
Calcd for C13H12I2O2S2: C, 30.13; H, 2.33; I, 48.98%.
(rel intensity) 266 (Mþ + 2, 12.14), 265 (Mþ + 1, 16.78), 264
(Mþ, 100); HRMS (EI, 110 eV) m=z 264.0287 (Mþ) (Calcd for
C13H12O2S2: 264.0279). Found: C, 58.83; H, 4.66%. Calcd for
C13H12O2S2: C, 59.06; H, 4.58%.
2,2-Bis(4-methyl-5-trimethylsilyl-3-thienyl)-1,3-dioxolane
(17). To a solution of 16 (1500 mg, 2.895 mmol) in anhydrous
THF (60 mL) was added dropwise a hexane solution of butyllithi-
um (1.54 M hexane solution, 4.25 mL, 6.375 mmol) with stirring at
4-Ethylenedioxy-2,6-diiodo-3,5-dimethyl-4H-cyclopenta[2,1-
b:3,4-b0]dithiophene (19). To a solution of 18 (590 mg, 2.232
mmol) in a mixture of anhydrous chloroform (30 mL) and acetic
acid (30 mL) was added NIS (1105 mg, 4.911 mmol) with stirring
at room temperature under argon atmosphere. Then, this reaction
mixture was stirred for 2 h at room temperature, and then was pour-
ed into aqueous Na2SO3. The resulting mixture was extracted with
chloroform. The chloroform extract was washed successively with
aqueous NaHCO3, water, and brine, and was then dried over
Na2SO4. Solvent evaporation from the dried extract gave a crude
product, which was chromatographed on silica gel by eluting with
toluene to give pure 4-ethylenedioxy-2,6-diiodo-3,5-dimethyl-4H-
cyclopenta[2,1-b:3,4-b0]dithiophene (19) as yellow needless (878
mg, 76.2%): mp 184–185 ꢃC (decomp); 1H NMR (CDCl3, 200
MHz) ꢅ 4.36 (4H, s, OCH2CH2O), 2.18 (6H, s, Me); IR (KBr)
2891, 1718, 1512, 1417, 1373, 1315, 1196, 1149, 1082, 1026,
980, 951, 795, 737, 596 cmꢂ1; MS (DEI, 110 eV) m=z (rel intensi-
ty) 518 (Mþ + 2, 12.09), 517 (Mþ + 1, 16.51), 516 (Mþ, 100);
HRMS (EI, 110 eV) m=z 515.8214 (Mþ) (Calcd for C13H10I2O2S2:
515.8212). Found: C, 30.19; H, 2.17; I, 48.94%. Calcd for
C13H10I2O2S2: C, 30.25; H, 1.95; I, 49.17%.
ꢃ
ꢂ78 C under argon atmosphere. Then this reaction mixture was
stirred at ꢂ78 ꢃC for 30 min. To this was added dropwise trimeth-
ylsilyl chloride (1.47 mL, 1258 mg, 11.582 mmol) at ꢂ78 ꢃC, and
then this reaction mixture was stirred at ꢂ78 ꢃC for 30 min. After
warming to room temperature, the reaction mixture was poured in-
to aqueous Na2SO3 and was then extracted with ether. The ether
extract was washed successively with aqueous NaHCO3, water
and then brine, and was then dried over Na2SO4. Solvent evapora-
tion from the dried extract gave pale yellow crystals (1228 mg),
which were chromatographed on silica gel by eluting with a mix-
ture of toluene–hexane (1:1, v/v) to give pure 2,2-bis(4-methyl-5-
trimethylsilyl-3-thienyl)-1,3-dioxolane (17) as colorless plates
(1052 mg, 88%): mp 130–131 ꢃC; 1H NMR (CDCl3, 200 MHz)
ꢅ 7.41 (2H, s, H-2), 4.07 (4H, s, OCH2CH2O), 2.21 (6H, s, Me),
0.32 (18H, s, SiMe3); IR (KBr) 3120, 2954, 2893, 2879, 1525,
1452, 1406, 1375, 1360, 1250, 1184, 1159, 1063, 1041, 968,
837, 781, 752, 710, 688, 629 cmꢂ1; MS (DEI, 70 eV) m=z (rel in-
tensity) 412 (Mþ + 2, 6.84), 411 (Mþ + 1, 11.04), 410 (Mþ,
31.23), 395 (Mþ ꢂ Me, 13.40), 241 (Mþ ꢂ C8H13SSi, 100);
HRMS (EI, 110 eV) m=z 410.1214 (Mþ) (Calcd for
C19H30O2S2Si2: 410.1226). Found: C, 55.34; H,7.61%. Calcd for
C19H30O2S2Si2: C, 55.56; H, 7.36%.
2,6-Bis(dicyanomethylene)-4-ethylenedioxy-3,5-dimethyl-
2,6-dihydro-4H-cyclopenta[2,1-b:3,4-b0]dithiophene (EO-Me2-
CPDT-TCNQ: 20). To a suspension of sodium hydride (60 wt
%, 62.0 mg, 0.450 mmol) in anhydrous THF (5 mL) was added
dropwise a solution of malononitrile (51.0 mg, 0.772 mmol) in an-
hydrous THF (5 mL) at room temperature under argon atmosphere.
Then, the reaction mixture was stirred for 10 min at room temper-
ature. To this were added successively a solution of 19 (100.0 mg,
0.194 mmol) in anhydrous THF (5 mL) and [Pd(PPh3)4] (45.0 mg,
4-Ethylenedioxy-3,5-dimethyl-4H-cyclopenta[2,1-b:3,4-b0]-
dithiophene (18). To a solution of 17 (700 mg, 1.704 mmol) in
anhydrous ether (70 mL) was added dropwise t-butyllithium
(1.47ꢃM pentane solution, 2.55 mL, 3.749 mmol) with stirring at
ꢂ78 C under argon atmosphere. After the reaction mixture was
ꢃ
stirred for 30 min at ꢂ78 C under argon atmosphere, copper(II)
ꢃ
chloride (1833 mg, 13.633 mmol) was added, and then this reaction
mixture was stirred for another 30 min at ꢂ78 ꢃC. After being
warmed to room temperature, the reaction mixture was stirred
for 3 h at room temperature. The inorganic precipitate was re-
moved by filtration through a glass disk. Then the filtrate was pour-
ed into water and extracted with ether. The ether extract was wash-
ed successively with aqueous NaHCO3, water, and then brine, and
was then dried over Na2SO4. Solvent evaporation from the dried
extract gave crude 4-ethylenedioxy-3,5-dimethyl-2,6-bis(trimeth-
ylsilyl)-4H-cyclopenta[2,1-b:3,4-b0]dithiophene as a reddish oil
(638 mg), which was used in the following reaction without further
purification. To an anhydrous THF (40 mL) solution of crude 4-
ethylenedioxy-3,5-dimethyl-2,6-bis(trimethylsilyl)-4H-cyclopenta-
[2,1-b:3,4-b0]dithiophene (638 mg, ca. 1.56 mmol) was added
dropwise a THF solution of tetrabutylammonium fluoride (TBAF:
1.0 M THF solution containing 5% water, 3.12 mL). After stirring
for 2 h at room temperature, the reaction mixture was poured into
aqueous NaHCO3 and then extracted with ether. The ether extract
was washed with water and then brine, and was then dried over
Na2SO4. Solvent evaporation from the dried extract gave a crude
product (450 mg), which was chromatographed on silica gel by
eluting with toluene to give pure 4-ethylenedioxy-3,5-dimethyl-
4H-cyclopenta[2,1-b:3,4-b0]dithiophene (18) as colorless needles
(309 mg, 75%): mp 138–139 ꢃC (decomp); 1H NMR (CDCl3,
200 MHz) ꢅ 6.67 (2H, q, J2,Me ¼ J5,Me ¼ 1:0 Hz, H-2, 6), 4.33
(4H, s, OCH2CH2O), 2.25 (6H, d, J2,Me ¼ J5,Me ¼ 1:0 Hz, Me);
IR (KBr) 3095, 2952, 2891, 1522, 1435, 1383, 1325, 1211, 1165,
1076, 1020, 980, 949, 843, 715 cmꢂ1; MS (DEI, 110 eV) m=z
0.0389 mmol). The reaction mixture was stirred at 50 C for 2 h,
and then stirred for 2 h at the refluxing temperature. After cooling
to room temperature, the reaction mixture was poured into a mix-
ture of bromine (0.5 mL) and water (20 mL). Then, the resulting
mixture was poured into aqueous Na2SO3 and extracted with di-
chloromethane. The dichloromethane extract was washed with
aqueous NaHCO3, water, and brine, and was then dried over
Na2SO4. Solvent evaporation from the dried extract gave a crude
product, which was chromatographed on silica gel by eluting with
dichloromethane to give pure 2,6-bis(dicyanomethylene)-4-ethyl-
enedioxy-3,5-dimethyl-2,6-dihydro-4H-cyclopenta[2,1-b:3,4-b0]-
dithiophene (EO-Me2CPDT-TCNQ: 20) as a violet powder (34.8
mg, 45.8%): mp > 300 C; H NMR (CDCl3, 200 MHz) ꢅ 4.46
(4H, s, OCH2CH2O), 2.49 (6H, s, Me); IR (KBr) 2214, 1496,
1439, 1383, 1346, 1269, 1244, 1174, 1066, 1034, 1009, 989,
951, 874 cmꢂ1; HRMS (EI, 110 eV) m=z 390.0251 (Mþ) (Calcd
for C19H10N4O2S2: 390.0245). Found: C, 58.52; H, 2.44;N,
14.19%. Calcd for C19H10N4O2S2: C, 58.45; H, 2.58; N, 14.35%.
2,6-Bis(dicyanomethylene)-3,5-dimethyl-2,6-dihydro-4H-cy-
clopenta[2,1-b:3,4-b0]dithiophen-4-one (Me2CPDT-TCNQ: 3).
To a solution of 20 (35.0 mg, 0.0896 mmol) in dichloromethane
(70 mL) was added 70% perchloric acid (35 mL) with stirring at
10 ꢃC. The reaction mixture was warmed to 20 ꢃC, and then stirred
at 20ꢃC for 24 h. The reaction mixture was poured into ice-water,
and then was extracted with dichloromethane. The dichlorometh-
ane extract was washed with aqueous NaHCO3, water, and then
brine, and was then dried over Na2SO4. Solvent evaporation from
the dried extract gave a crude product (29.7 mg), which was chro-
ꢃ
1

T. Chonan et al.
Bull. Chem. Soc. Jpn., 77, No. 8 (2004) 1497
S. Hunig and P. Erk, Adv. Mater., 3, 225 (1991).
matographed on silica gel by eluting with dichloromethane to give
pure 2,6-bis(dicyanomethylene)-3,5-dimethyl-2,6-dihydro-4H-cy-
clopenta[2,1-b:3,4-b0]dithiophen-4-one (Me2CPDT-TCNQ: 3) as
a violet powder (26.2 mg, 84.4%): mp > 300 ꢃC; 1H NMR (CDCl3,
200 MHz) ꢅ 2.75 (6H, s, Me); IR (KBr) 2958, 2922, 2854, 2362,
2212, 1720, 1496, 1377, 1329, 1263, 1200, 1101, 1022, 874
cmꢂ1; UV–vis (CH2Cl2) ꢆ/nm (log ") 531 (4.47), 500 (4.37),
476 (sh, 4.10), 362 (2.84), 346 (2.92), 278 (3.41), 269 (3.47);
HRMS (EI, 110 eV) m=z 345.9986 (Mþ) (Calcd for C17H6N4OS2:
345.9983). Found: C, 58.77; H, 1.87; N, 15.89%. Calcd for
C17H6N4OS2: C, 58.95; H, 1.75; N, 16.17%.
¨
4
T. Otsuka, A. Kobayashi, Y. Miyamoto, J. Kiuchi, N.
Wada, E. Ojima, H. Fujiwara, and H. Kobayashi, Chem. Lett.,
2000, 732; T. Otsuka, A. Kobayashi, Y. Miyamoto, J. Kikuchi,
S. Nakamura, N. Wada, E. Fujiwara, H. Fujiwara, and H.
Kobayashi, J. Solid State Chem., 159, 407 (2001); R. Kato, Kotai
Butsuri, 28, 141 (1993).
5
K. Yui, Y. Aso, T. Otsubo, and F. Ogura, J. Chem. Soc.,
Chem. Commun., 1987, 1816; K. Yui, Y. Aso, T. Otsubo, and F.
Ogura, Bull. Chem. Soc. Jpn., 62, 1539 (1989).
6
K. Takahashi and S. Tarutani, J. Chem. Soc., Chem. Com-
Me4N(Me2CPDT-TCNQ)2. Black needles, mp > 300 ꢃC; IR
(KBr) 2179, 1707, 1460, 1419, 1379, 1313, 1215, 1161, 1149 1083
mun., 1994, 519; K. Takahashi and S. Tarutani, Adv. Mater.,
1995, 639; K. Takahashi and S. Tarutani, Synth. Met., 70, 1165
(1995); S. Tarutani, T. Mori, H. Mori, S. Tanaka, and K.
Takahashi, Chem. Lett., 1997, 627.
cmꢂ1
. Found: C, 59.33; H, 3.37; N, 16.27%. Calcd for
C38H24N9O2S4: C, 59.51; H, 3.15; N, 16.44%.
Me4P(Me2CPDT-TCNQ)2. Black needles, mp > 300 ꢃC; IR
(KBr) 2193, 2175, 1711, 1462, 1421, 1379, 1321 (br), 1275, 1213,
1122 (br), 1080, 982 cmꢂ1. Found: C, 58.08; H, 3.35; N, 13.96%.
Calcd for C38H24N8O2S4P: C, 58.22; H, 3.09; N, 14.29%.
Me4As(Me2CPDT-TCNQ)2. Black needles, mp > 300 ꢃC; IR
(KBr) 2193, 2173, 1711, 1462, 1421, 1379, 1321 (br), 1273, 1211,
1115 (br), 1076, 930 cmꢂ1. Found: C, 54.95; H, 3.21; N, 13.28%.
Calcd for C38H24N8O2S4As: C, 55.13; H, 2.92; N, 13.54%.
Me4Sb(Me2CPDT-TCNQ)2. Black needles, mp > 300 ꢃC; IR
(KBr) 2189, 2168, 1711, 1460, 1415, 1379, 1317, 1277, 1211,
1167, 1132 (br), 1115 (br), 1078, 993, 908, 866 cmꢂ1. Found: C,
51.91; H, 3.02; N, 12.57%. Calcd for C38H24N8O2S4Sb: C, 52.18
H, 2.77; N, 12.81%.
7
Schnering, J.-U. von Schutz, S. Soderholm, H.-P. Werner, and
E. Gunther, S. Hunig, K. Peters, H. Rieder, H. G. von
¨ ¨
¨
¨
H. C. Wolf, Angew. Chem., Int. Ed. Engl., 29, 204 (1990).
a) K. Takahashi and S. Tarutani, Chem. Commun., 1998,
8
1233. b) S. Tarutani and K. Takahashi, Bull. Chem. Soc. Jpn.,
77, 463 (2004).
9 J. Yamaura, R. Kato, H. Tajima, S. Tarutani, and K.
Takahashi, Synth. Met., 103, 2212 (1999).
10 S. Gronowitz, P. Moses, A.-B. Hornfeldt, and R.
¨
Hakansson, Ark. Kemi, 17, 165 (1961).
11 M. Uno, K. Seto, and S. Takahashi, J. Chem. Soc., Chem.
Commun., 1984, 932; M. Uno, K. Seto, M. Sasuda, W. Ueda,
and S. Takahashi, Tetrahedron Lett., 26, 1553 (1985).
12 The destabilization extent of the LUMO level of 3 is about a
half of the destabilization extent of the HOMO level of 3. Howev-
er, the half-wave reduction potentials obtained by cyclic voltam-
metry are much more reliable to know the energy levels of the
LUMOs.
We thank Professor Tatsuro Imakubo and Dr. Takashi
Shirahata of the Institute of Physical and Chemical Research
(RIKEN), Wako, Saitama, Japan for their helpful MO calcula-
tions and for calculating the activation energies.
13 G. Saito and J. P. Ferraris, J. Chem. Soc., Chem. Commun.,
1979, 1027.
14 R. C. Wheland and J. L. Gilson, J. Am. Chem. Soc., 98,
3916 (1976); R. C. Wheland, J. Am. Chem. Soc., 98, 3926 (1976).
References
1
J. Ferraris, D. O. Cowan, V. J. Walatka, and J. H. Perlstein,
J. Am. Chem. Soc., 95, 948 (1973).
R. C. Wheland, J. Am. Chem. Soc., 98, 3926 (1979); R. C.
15 K. Deuchert and S. Hunig, Angew. Chem., Int. Ed. Engl.,
¨
2
17, 875 (1978); S. Hunig, Pure Appl. Chem., 62, 395 (1990); M.
¨
Wheland and J. L. Gilson, J. Am. Chem. Soc., 98, 3916 (1976); A.
Andrieux, P. M. Chaikin, C. Duroure, D. Je’rome, C. Weyl,
K. Bechgaad, and J. R. Anderson, J. Phys., 40, 1199 (1979); H.
Urayama and G. Sato, Synth. Met., 19, 469 (1987).
Horner and S. Hunig, Angew. Chem., Int. Ed. Engl., 16, 410 (1977).
16 S. Tarutani, J. Yamaura, K. Takahashi, and R. Kato, Solid
State Commun., 123, 251 (2002).
17 J. Yamaura, M. Fujiwara, R. Kato, T. Chonan, and K.
Takahashi, Synth. Met., 120, 913 (2001).
¨
3
A. Aumuller, P. Erk, G. Klebe, S. Hunig, J. U. von Schutz,
¨ ¨ ¨
and H.-P. Werner, Angew. Chem., Int. Ed. Engl., 25, 740 (1986);