Novel bis-fused π-electron donors for organic metals: 2-(1,3-dithiol-2-ylidene)-5-(thiopyran-4-ylidene)-1,3,4,6-tetrathiapentalene

Article abstract of DOI:10.1021/jo9516244

Bis-fused π-electron donors composed of tetrathiafulvalene (TTF) and 2-(thiopyran-4-ylidene)-1,3-dithiole (TPDT), 2-(1,3-dithiol-2-ylidene)-5-(thiopyran-4-ylidene)-1,3,4,6-tetrathiapentalene (1a, TPDT-TTP), and its derivatives (1b-d, 2a-d) have been synthesized as donor components for organic conductors. An X-ray structure analysis of bis(methylthio)-1 (1c) revealed that the TPDT-TTP skeleton is almost planar except for the outer 1,3-dithiole ring, and that the crystal has a two-dimensional "θ-type" arrangement of molecules. The cyclic voltammograms of TPDT-TTPs exhibit four pairs of single-electron redox waves. The first oxidation potential (E₁) of 1a (+0.37 V vs SCE, in PhCN) is comparable to that of TTF (+0.35 V) and is higher by 0.1 V than that of TPDT (+0.27 V). The observed substituent effect on E₁ values suggests that the first one-electron oxidation mainly occurs in the 2-(thiopyran-4-ylidene)-1,3-dithiole (TPDT) moiety. On the other hand, on-site coulombic repulsion estimated from the E₂ - E₁ value is lower than in TTF and TPDT. MNDO MO calculations reveal that all the sulfur atoms in the 1,3-dithiole rings have the same phase in the HOMO, a condition necessary for realization of effective transverse intermolecular interaction. The present donors have produced many charge-transfer complexes and cation radical salts showing relatively high conductivity (σ_rt = 10^-1-10¹ S cm^-1), several of which display metallic temperature dependence.

Full text of DOI:10.1021/jo9516244

3650
J . Org. Chem. 1996, 61, 3650-3656
Novel Bis-F u sed π-Electr on Don or s for Or ga n ic Meta ls:
2-(1,3-Dith iol-2-ylid en e)-5-(th iop yr a n -4-ylid en e)-1,3,4,6-tetr a th ia p en ta len e
Yohji Misaki,* Hideki Fujiwara, and Tokio Yamabe*
Division of Molecular Engineering, Graduate School of Engineering, Kyoto University, Yoshida,
Kyoto 606-01, J apan
Received September 6, 1995X
Bis-fused π-electron donors composed of tetrathiafulvalene (TTF) and 2-(thiopyran-4-ylidene)-1,3-
dithiole (TPDT), 2-(1,3-dithiol-2-ylidene)-5-(thiopyran-4-ylidene)-1,3,4,6-tetrathiapentalene (1a ,
TPDT-TTP), and its derivatives (1b-d , 2a -d ) have been synthesized as donor components for
organic conductors. An X-ray structure analysis of bis(methylthio)-1 (1c) revealed that the TPDT-
TTP skeleton is almost planar except for the outer 1,3-dithiole ring, and that the crystal has a
two-dimensional “θ-type” arrangement of molecules. The cyclic voltammograms of TPDT-TTPs
exhibit four pairs of single-electron redox waves. The first oxidation potential (E1) of 1a (+0.37 V
vs SCE, in PhCN) is comparable to that of TTF (+0.35 V) and is higher by 0.1 V than that of TPDT
(+0.27 V). The observed substituent effect on E1 values suggests that the first one-electron oxidation
mainly occurs in the 2-(thiopyran-4-ylidene)-1,3-dithiole (TPDT) moiety. On the other hand, on-
site coulombic repulsion estimated from the E2 - E1 value is lower than in TTF and TPDT. MNDO
MO calculations reveal that all the sulfur atoms in the 1,3-dithiole rings have the same phase in
the HOMO, a condition necessary for realization of effective transverse intermolecular interaction.
The present donors have produced many charge-transfer complexes and cation radical salts showing
relatively high conductivity (σrt ) 10-1-101 S cm-1), several of which display metallic temperature
dependence.
In tr od u ction
of two or three TTF units.2e,7 The first condition is
essential in order to suppress the metal to insulator
transition at low temperature characteristic of the usual
one-dimensional metals.8 In fact, all of the TTF donors
that have afforded ambient superconductors so far have
satisfied this requirement. But the design and prepara-
tion of donor molecules that satisfy both of the principles
mentioned above are now of particular interest in the
search for new organic metals that are stable at low
temperature. Bis-fused TTF, 2,5-bis(1,3-dithiol-2-ylidene)-
1,3,4,6-tetrathiapentalene (BDT-TTP),9 is one of the most
promising donors. We have recently synthesized many
BDT-TTP derivatives,10 several of which have produced
metallic cation radical salts stable to low temperatures
(e4.2 K).10,11 In this context, bis-fused 1,3-dithiole donors
having different skeletons from TTF are also attractive
targets. 2-(Thiopyran-4-ylidene)-1,3-dithiole (TPDT),12
Recently, compounds that act as π-electron donors have
received considerable attention in the context of the
preparation of organic conductors.1,2 In particular, the
modification of tetrathiafulvalene (TTF) has been popular
because TTF and its derivatives have been structural
components of many organic superconductors.3 In gen-
eral, the modification of TTF has served one of two
purposes. The first is to increase the dimensionality of
conducting salts, which has usually been achieved by
introduction of alkylchalcogeno substituents onto the TTF
skeleton4 and/or the exchange of the sulfur atoms of TTF
with the larger chalcogenides such as selenium or tel-
lurium.5 The second goal has been to decrease on-site
coulombic repulsion in the dication state, which is
realized by the insertion of a π-electron spacer unit
between two 1,3-dithiole rings of TTF,2d,6 or by linkage
X Abstract published in Advance ACS Abstracts, May 1, 1996.
(1) Recent Proceedings of International Conferences: (a) Synthetic
Metals; Elsevier: New York, Park, Y. W.; Lee, H., Eds, 1995; Vols. 69-
71. (b) The Physics and Chemistry of Organic Superconductors; Saito,
G., Kagoshima, S., Eds.; Springer-Verlag: Berlin, Heidelberg, 1990.
(2) Reviews: (a) Krief, A. Tetrahedron 1986, 42, 1209. (b) Bryce,
M. R. Chem Soc. Rev. 1991, 20, 355. (c) Cowan, D. O.; McCullough,
R.; Bailey, A.; Lerstrup, K.; Talham, D.; Herr, D.; Mays, M. Phosphrous,
Sulfur, Silicon 1992, 67, 277. (d) Thomas, K.; Hansen, K.; Becher, J .
Adv. Mater. 1993, 5, 288. (e) Adam, M.; Mu¨llen, K. Adv. Mater. 1994,
6, 439.
(3) (a) Williams, J . M.; Ferraro, J . R.; Thorn, R. J .; Carlson, K. D.;
Geiser, U.; Wang, H. H.; Kini, A. M.; Whangbo, M.-H. Organic
Superconductors; Prentice Hall: New J ersey, 1992. (b) Ishiguro, T.;
Yamaji, K. Organic Superconductors; Springer-Verlag: Berlin, Heidel-
berg, 1990. (c) Bechgaard, K.; J e´rome, D. Sci. Am. 1982, 247, 50.
(4) (a) Saito, G.; Enoki, T.; Toriumi, K.; Inokuchi, H. Solid State
Commun. 1982, 42, 557. (b) Nakamura, T.; Iwasawa, S.; Nakano, H.;
Inoue, K.; Nogami, T.; Mikawa, H. Bull. Chem. Soc. J pn. 1987, 60,
365. (c) Suzuki, T.; Yamochi, H.; Srdanov, G.; Hinkelmann, K.; Wudl,
F. J . Am. Chem. Soc. 1989, 111, 3108. (d) Kato, R.; Kobayashi, H.;
Kobayashi, A. Synth. Met. 1991, 42, 2093. (e) Misaki, Y.; Nishikawa,
H.; Kawakami, K.; Uehara, T.; Yamabe, T. Tetrahedron Lett. 1992,
33, 4321.
(6) (a) Yamashita, Y.; Kobayashi, Y.; Miyashi, T. Angew. Chem., Int.
Ed. Engl. 1989, 28, 1052. (b) Takahashi, K.; Nihira, T.; Tomitani, K.
J . Chem. Soc., Chem. Commun. 1993, 1617. (c) Hansen, T. K.;
Lakshmikantham, M. V.; Cava, M. P.; Niziurski-Mann, R. E.; J ensen,
F.; Becher, J . J . Am. Chem. Soc. 1992, 114, 5035. (d) Benahmed-Gasmi,
A. S.; Fre`re, P.; Garrigues, B.; Gorgues, A.; J ubault, M.; Carlie, R.;
Texier, F. Tetrahedron Lett. 1992, 33, 6457. (e) Belyasmine, A.; Fre`re,
P.; Gorgues, A.; J ubault, M.; Duguay, G.; Hudhomme, P. Tetrahedron
Lett. 1993, 34, 4005. (f) Sugimoto, T.; Awaji, H.; Sugimoto, I.; Misaki,
Y.; Kawase, T.; Yoneda, S.; Yoshida, Z.; Kobayashi, T.; Anzai, H. Chem.
Mater. 1989, 1, 535.
(7) (a) Tatemitsu, H.; Nishikawa, E.; Sakata, Y.; Misumi, S. Synth.
Met. 1987, 19, 565. (b) Wolf, P.; Naarmann, H.; Mu¨llen, K. Angew.
Chem., Int. Ed. Engl. 1988, 27, 288. (c) Fourmigue, M.; Batail, P. J .
Chem. Soc., Chem. Commun. 1991, 1370. (d) J ørgensen, M.; Lerstrup,
K. A.; Bechgaard, K. J . Org. Chem. 1991, 56, 5684. (e) Tachikawa, T.;
Izuoka, A.; Kumai, R.; Sugawara, T.; Sugawara, Y. Solid State
Commun. 1992, 82, 19. (f) Iyoda, M.; Kuwatani, Y.; Ueno, N.; Oda, M.
J . Chem. Soc., Chem. Commun. 1992, 158. (g) Belyasmine, A.; Gorgues,
A.; J ubault, M.; Duguay, G. Synth. Met. 1991, 41-43, 2323. (h) Bryce,
M. R.; Marshallsay, G. J .; Moore, A. J . J . Org. Chem. 1992, 57, 4859.
(i) Iyoda, M.; Fukuda, M.; Yoshida, M.; Sasaki, S. Chem. Lett. 1994,
2369.
(8) Ferraris, J .; Cowan, D. O.; Walatka, V. J .; Perlstein, J . H. J .
Am. Chem. Soc. 1973, 95, 948.
(9) Schumaker, R. R.; Engler, E. M. J . Am. Chem. Soc. 1980, 102,
6652.
(5) (a) Engler, E. M.; Patel, V. V. J . Am. Chem. Soc. 1974, 96, 7376.
(b) McCullough, R. D.; Kok, G. B.; Lerstrup, K. A.; Cowan, D. O. J .
Am. Chem. Soc. 1987, 109, 4115.
S0022-3263(95)01624-0 CCC: $12.00 © 1996 American Chemical Society

Novel Bis-Fused π-Electron Donors for Organic Metals
Sch em e 1
J . Org. Chem., Vol. 61, No. 11, 1996 3651
Ch a r t 1
which possesses an unsymmetrical π-framework, is an
interesting donor because unsymmetrical donors are
available for the stabilization of metallic states at low
temperatures. In fact several unsymmetrical derivatives
of TTF, tetraselena- and diselenadithia-fulvalene have
produced superconducting cation radical salts.13 In this
article, we report the synthesis, structure, and electro-
chemical properties of various derivatives of 2-(1,3-
dithiol-2-ylidene)-5-(thiopyran-4-ylidene)-1,3,4,6-tetra-
thiapentalene (TPDT-TTP, 1a )14 which is a bis-fused
donor composed of TTF and TPDT. Furthermore, the
conducting properties of their charge-transfer (CT) com-
plexes and cation radical salts are described.
Resu lts a n d Discu ssion
Syn t h esis. The syntheses of TPDT-TTPs were
achieved as shown in Scheme 1. Treatment of a phos-
phorus reagent for a Wittig-Horner reaction (3)4e with
an equimolar amount of LDA in the presence of tetrahy-
drothiopyran-4-one (4) or 2,6-diphenyltetrahydrothiopy-
ran-4-one (5) in THF at -78 °C gave 1,3-dithiole-2-thione
6 or 7 in 67 and 85% yield, respectively. The reaction of
6, 7 with an excess of mercury(II) acetate in chloroform-
acetic acid (1:1, v/v) at room temperature afforded the
corresponding 1,3-dithiol-2-ones (8, 9) in the respective
yields of 92 and 90%. When the ketones 8, 9 were cross-
coupled with various 1,3-dithiole-2-thiones (10b-d ) in
neat triethyl phosphite at 80 °C, the corresponding
tetrahydro derivatives of 1 (11b-d ) and 2 (12b-d ) were
obtained in 40-73% yields. Dehydrogenation of 11 and
12 was carried out by treatment with an excess of DDQ
in refluxing xylene to give the target donors (1b-d and
2b-d ) in 59-98% yields. In the synthesis of TPDT
derivatives, the dehydrogenation was carried out by using
p-chloranil in refluxing benzene or toluene.12 Sandman
et al. had reported that the yield of bis(methoxycarbonyl)-
TPDT considerably decreased (84 f 10%) when DDQ was
used as a dehydrogenation reagent.12c However, it was
quantitatively obtained by DDQ dehydrogenation in our
case. The differing result of Sandman et al. and
ourselves is probably due to several differences in ex-
perimental conditions such as reaction temperature,
concentration of substrates, reaction time, etc. The
(10) (a) Misaki, Y.; Nishikawa, H.; Kawakami, K.; Koyanagi, S.;
Yamabe, T.; Shiro, M. Chem. Lett. 1992, 2321. (b) Misaki, Y.; Nish-
ikawa, H.; Yamabe, T.; Mori, T.; Inokuchi, H.; Mori. H.; Tanaka, S.
Chem. Lett. 1993, 729. (d) Misaki, Y.; Matsui, T.; Kawakami, K.;
Nishikawa, H.; Yamabe, T.; Shiro, M. Chem. Lett. 1993, 1337. (e)
Misaki, Y.; Nishikawa, H.; Kawakami, K.; Yamabe, T.; Mori, T.;
Inokuchi, H.; Mori, H.; Tanaka, S. Chem. Lett. 1993, 2073. (h) Misaki,
Y.; Kawakami, K.; Matsui, T.; Yamabe, T.; Shiro, M. J . Chem. Soc.,
Chem. Commun. 1994, 459.
(11) (a) Mori, T.; Inokuchi, H.; Misaki, Y.; Nishikawa, H.; Yamabe,
T.; Mori, H.; Tanaka, S. Chem. Lett. 1993, 2085. (b) Mori, T.; Misaki,
Y.; Yamabe, T. Bull. Chem. Soc. J pn. 1994, 67, 3187. (c) Misaki, Y.;
Fujiwara, H.; Yamabe, T.; Mori, T.; Mori, H.; Tanaka, S. Chem. Lett.
1994, 1653. (d) Mori, T.; Misaki, Y.; Fujiwara, H.; Yamabe, T. Bull.
Chem. Soc. J pn. 1994, 67, 2685. (e) Mori, T.; Misaki, Y.; Yamabe, T.;
Mori, H.; Tanaka, S. Chem. Lett. 1995, 549.
(12) (a) Sandman, D. J .; Fisher, A. P., III; Holmes, T. J .; Epstein,
A. J . J . Chem. Soc., Chem. Commun. 1977, 687. (b) Shiomi, Y.; Aso,
Y.; Otsubo, T.; Ogura, F. J . Chem. Soc., Chem. Commun. 1988, 822.
(c) Sandman, D. J .; Ceasar, G. P.; Fisher, A. P., III; Schramm, E.; Titus,
D. D.; Baker, A. D. Chem. Mater. 1989, 1, 421. (d) Otsubo, T.; Shiomi,
Y.; Imamura, M.; Kittaka, R.; Ohnishi, A.; Tagawa, H.; Aso, Y.; Ogura,
F. J . Chem. Soc., Perkin Trans. 2 1993, 1815.
(13) (a) Kikuchi, K.; Kikuchi, M.; Namiki, T.; Saito, K.; Ikemoto, I.;
Murata, K.; Ishiguro, T.; Kobayashi, K. Chem. Lett. 1987, 931. (b)
Papavassiliou, G. C.; Mousdis, G. A.; Zambounis, J . S. Synth. Met.
1988, 27, B379. (c) Zambounis, J . S.; Mayer, C. W.; Hauenstein, K.;
Hilti, B.; Hofherr, W.; Pfeiffer, J .; Bu¨rkle, M.; Rihs, G. Adv. Mater.
1992, 4, 33. (d) Kato, R.; Aonuma, S.; Okano, Y.; Sawa, H.; Tamura,
M.; Kinoshita, M.; Oshima, K.; Kobayashi, A.; Bun, K.; Kobayashi, H.
Synth. Met. 1993, 61, 199.
(14) Preliminary communications, Misaki, Y.; Fujiwara, H.; Yamabe,
T. J . Chem. Soc., Chem. Commun. 1993, 949.; Misaki, Y.; Fujiwara,
H.; Maruyama, T.; Yamabe, T. Synth. Met. 1995, 70, 1147.

3652 J . Org. Chem., Vol. 61, No. 11, 1996
Misaki et al.
F igu r e 1. Molecular structure of 1c with atomic numbering
scheme (a) and the side view (b); selected bond lengths (Å):
S(1)-C(4), 1.72(2); S(1)-C(6), 1.74(2); S(2)-C(1), 1.77(2); S(2)-
C(7), 1.75(2); S(3)-C(1), 1.76(2); S(3)-C(8), 1.73(2); S(4)-C(7),
1.75(2); S(4)-C(9), 1.77(2); S(5)-C(8), 1.75(1); S(5)-C(9), 1.76-
(2); S(6)-C(10), 1.77(2); S(6)-C(11), 1.75(1); S(7)-C(10), 1.76-
(2); S(7)-C(12), 1.75(2); S(8)-C(11), 1.77(2); S(8)-C(13), 1.76-
(2); S(9)-C(12), 1.75(1); S(9)-C(14), 1.74(3); C(1)-C(2), 1.36(2);
C(2)-C(3), 1.46(2); C(2)-C(5), 1.43(2); C(3)-C(4), 1.33(2);
C(5)-C(6), 1.33(2); C(7)-C(8), 1.33(2); C(9)-C(10), 1.33(2);
C(11)-C(12), 1.33(2).
unsubstituted derivatives 1a and 2a were obtained in 45
and 62% yields, respectively, by the demethoxycarbony-
lation of 1b and 2b with an excess (10 mol equiv) of
LiBr‚H2O in HMPA at 90 °C and then at 130 °C. All of
the donors are stable solids and considerably less soluble
in organic solvents than the corresponding TTF and
TPDT derivatives.
Molecu la r a n d Cr ysta l Str u ctu r es of 1c. From
among the newly prepared donors, single crystals of 1c
were obtained by recrystallization from CS2-benzonitrile,
and its molecular and crystal structures were determined
in an X-ray structure analysis.21 The molecular structure
is shown in Figure 1. The TPDT-TTP skeleton is almost
planar except for the outer 1,3-dithiole ring, which is
slightly tilted with a dihedral angle of 9.5°. The meth-
ylthio groups are bent upward from the molecular plane.
In the crystal 1c, molecules are stacked in a head-to-head
manner, while they are arranged in a head-to-tail man-
ner along the transverse direction (Figure 2a). The
present arrangement of molecules is similar to the donor
array in θ-(BEDT-TTF)2I3 which is a 2D metal showing
superconductivity at 3.6 K (Figure 2b).15 The interplanar
distance of the stack is 3.48 Å. There are S-S contacts
less than the sum of the van der Waals radii (3.70 Å) in
both the intra- and the interstack; S(5)-S(6), 3.68(2) Å
for the intrastack, S(2)-S(3), 3.63(2) Å for the interstack.
This result indicates that 1c is expected to produce two-
dimensional metals if it has the same arrangement in
the molecular complexes.16
F igu r e 2. Crystal structure of 1c: (a) viewed along a-axis;
(b) viewed along the molecular long axis, showing intermo-
lecular S-S contacts (e3.70 Å) with dotted lines; S(5)-S(6),
3.68(2) Å for I, S(2)-S(3), 3.63(2) Å for II.
F igu r e 3. Cyclic voltammogram of 2d in benzonitrile at 25
°C.
Electr och em ica l P r op er ties. The electrochemical
properties of TPDT-TTP derivatives were investigated by
cyclic voltammetry. Figure 3 shows the cyclic voltam-
mogram of 2d in benzonitrile. All the donors show four
pairs of redox waves, all of which correspond to single-
electron transfers, given that the peak current of each
step is almost the same, and that there are four redox-
active units (three 1,3-dithiole rings and one thiopyrane
one). The redox potentials are summarized in Table 1
together with those of the related compounds measured
under identical conditions. The first oxidation potential
(E1) of 1a (+0.37 V vs SCE) is lower by 0.07 V than that
(15) Kobayashi, H.; Kato, R.; Kobayashi, A.; Nishio, Y.; Kajita, K.;
Sasaki, W. Chem. Lett. 1986, 833.
(16) Though the array of donors in neutral state has not been well
correlated with that in a partially oxidized state, two-dimensional array
of neutral molecules has been expected to be available for construction
of two-dimensional conductors. For examples; (a) Kobayashi, H.;
Kobayashi, A.; Sasaki, Y.; Saito, G.; Inokuchi, H. Bull. Chem. Soc. J pn.
1986, 59, 301. (b) Martin, J . D.; Canadell, E.; Becker, J . Y.; Bernstein,
J . Chem. Mater. 1993, 5, 1199. (c) Batsanov, A. S.; Bryce, M. R.; Cooke,
G.; Heaton, J . N.; Howard, J . A. K. J . Chem. Soc., Chem. Commun.
1993, 1701. (d) Bryce, M. R.; Cooke, G.; Dhindsa, A. S.; Ando, D. J .;
Hursthouse, M. B. Tetrahedron Lett. 1992, 33, 1783.

Novel Bis-Fused π-Electron Donors for Organic Metals
J . Org. Chem., Vol. 61, No. 11, 1996 3653
Ta ble 1. Red ox P oten tia ls of 1, 2, a n d Th eir Rela ted
Com p ou n d s in P h CN (V vs SCE, 25 °C)
a
compound
E1
E2
E3
E4
E2 - E1
1a
1c
2a
2b
2c
2d
+0.37
+0.38
+0.35
+0.38
+0.36
+0.36
+0.44
+0.35
+0.28
+0.27
+0.50
+0.34
+0.60
+0.63
+0.58
+0.64
+0.61
+0.61
+0.62
+0.77
+0.69
+0.63
+0.80
+0.63
+0.94
+0.93
+0.89
+1.07
+0.89
+0.88
+1.05
+1.11
+1.10
+1.15
+1.30
+1.12
+1.18
+1.13
0.23
0.25
0.23
0.26
0.25
0.25
0.18
0.42
0.41
0.36
0.30
0.29
a
BDT-TTP
TTF
TPDT
13a
13b
13c
F igu r e 4. Atomic coefficients of TPDT-TTP in the HOMO (a)
and in the HOMO-1 (b). The radii of the circles are ap-
proximately proportional to the LCAO coefficients.
a
Irreversible step. Anodic peak potentials.
TTP decreases relative to that in TTF and TPDT by
delocalization of the two positive charges over the entire
molecule.
Ch a r t 2
Molecu la r Or bita l Ca lcu la tion . Molecular orbital
calculations on TPDT-TTP were carried out by the
semiempirical MNDO method using the Gaussian 90
program.18 The geometry was fully optimized assuming
that the symmetry was C2v. Figure 4 shows the HOMO
and the 2nd HOMO (HOMO-1) of TPDT-TTP. Thus, the
HOMO of TPDT-TTP is composed of those of TTF19 and
TPDT which interact in-phase with each other. In
contrast, HOMO-1 is constructed from an out-of-phase
interaction between the HOMOs of each TTF and TPDT
unit. In the HOMO of TPDT-TTP, all sulfur atoms in
the 1,3-dithiole rings have the same phase. Thus,
effective transverse intermolecular interaction is ex-
pected in its cation radical salts, which is an indispen-
sable requirement for realization of two-dimensional
electronic structures.
P r ep a r a tion a n d P r op er ties of Ch a r ge-Tr a n sfer
Com p lexes a n d Ca tion Ra d ica l Sa lts. Most TPDT-
TTP donors reacted with tetracyano-p-quinodimethane
(TCNQ) and tetra-n-butylammonium triiodide to give the
corresponding TCNQ complexes and I3 salts. The other
cation radical salts were prepared by an electrochemical
oxidation of the donor at a constant current in the
presence of the corresponding tetra-n-butylammonium
salt as electrolyte. The electrical conductivity of the
charge-transfer salts obtained was measured using the
four-probe technique with gold paste contacts. The
results are summarized in Table 2. The parent TPDT-
TTP (1a ) gave a highly conducting TCNQ complex and
an I3 salt, whose conductivities on compressed pellets
were high values of 37 and 6.0 S cm-1 at room temper-
ature, respectively. Unfortunately both salts showed
semiconductive temperature dependence of conductivity,
however, their activation energies (Ea) were very small
(ca. 0.02 eV), suggesting that their single crystals are
expected to exhibit metallic conductive behavior. Com-
pressed pellets of TCNQ and the I3 salt of 1c were poorly
conductive semiconductors compared to those of 1a . In
contrast, cation radical salts of 1c with octahedral anions
of BDT-TTP. The increase in donating ability is expected
to be perturbed by almost half, as in the case of TTF and
TPDT, because the number of redox-active sites (1,3-
dithiole rings) of BDT-TTP is twice those of TTF. How-
ever, the difference in the E1 values of 1a and BDT-TTP
is identical to that between TTF and TPDT. Such a
significant perturbation to the donating ability of the bis-
fused donor system indicates that the positive charge of
(TPDT-TTP)•+ lies on the TPDT moiety, not on the TTF.
The E1 value of diphenyl substituted TPDT-TTP (2a ) is
slightly lower by 0.02 V than that of 1a , suggesting an
enhancement of the donating ability by substitution of
weak electron-donating phenyl groups. In contrast, E1
values of 1a and 2a are comparable to that of TTF (+0.35
V), and are higher by ca. 0.1 V than those of TPDT (+0.28
V) and diphenyl-TPDT (13a , +0.27 V). Such a decrease
of donating ability upon fusion of two donors is also
observed in other bis-fused donors such as BDT-TTP and
DTEDT (2-(1,3-dithiol-2-ylidene)-5-(2-ethanediylidene-
1,3-dithiole)-1,3,4,6-tetrathiapentalene).17 Compounds 2
exhibit very weak substituent effects on E1 values. For
example, 2b which has strongly electron-withdrawing
methoxycarbonyl groups, has an E1 value higher by only
0.03 V than the unsubstituted derivative 2a , while the
corresponding TPDT 13b has a higher E1 value, by 0.3
V, than 13a . Thus, the donating ability of 2b is slightly
weaker than that of TTF and is superior to that of BEDT-
TTF (E1 ) +0.51 V). The results described in this section
suggest that the positive charge of (TPDT-TTP)•+ exists
primarily on the more donating TPDT part, and that the
weaker donating TTF moiety plays the role of a sulfur-
based substituent. This is consistent with the E1 value
of 2a being identical with that of 13c. The same situation
exists with DTEDT.17b On the other hand, the ∆E () E2
- E1) value of 1a (0.23 V) and 2a (0.23 V) is smaller by
ca. 0.13-0.19 V than those of TTF (0.42 V),TPDT (0.41
V) and 13a (0.36 V). This result strongly suggests that
the on-site coulombic repulsion in the dication of TPDT-
(PF6, AsF6, and SbF6) showed high conductivities (σrt
)
101 S cm-1). They exhibited metallic temperature de-
pendence near room temperature, and a metal to semi-
conductor transition was observed at 150-250 K (Figure
(18) Frisch, M. J .; Head-Gordon, M.; Trucks, G. W.; Foresman, J .
B.; Schlegel, H. B.; Defrees, D. J .; Fox, D. J .; Whiteside, R. A.; Seeger,
R.; Melius, C. F.; Baker, J .; Martin, R. L.; Kahn, L. R.; Stewart, J . J .
P.; Topiol, S.; Pople, J . A. Gaussian 90, Revision F, Gaussian, Inc:
Pittsburgh PA, 1990.
(17) (a) Misaki, Y.; Higuchi, N.; Fujiwara, H.; Yamabe, T.; Mori, T.;
Mori, H.; Tanaka, S. Angew. Chem., Int. Ed. Engl. 1995, 34, 1222. (b)
Misaki, Y.; Ohta, T.; Higuchi, N.; Fujiwara, H.; Yamabe, T.; Mori, T.;
Mori, H.; Tanaka, S. J . Mater. Chem. 1995, 5, 1571.
(19) Bøwadt, S.; J ensen, F. Synth. Met. 1989, 32, 179.

3654 J . Org. Chem., Vol. 61, No. 11, 1996
Misaki et al.
Ta ble 2. Electr ica l P r op er ties of TCNQ Com p lexes a n d
Ca tion Ra d ica l Sa lts of 1 a n d 2
Con clu sion
In summary, we have synthesized many derivatives
of bis-fused π-electron donors containing the TPDT
moiety. X-ray structure analysis of 1c reveals that the
crystal has a two-dimensional θ-type arrangement of
molecules. The CV data of TPDT-TTPs indicate that the
positive charge in (TPDT-TTP)•+ mainly lies on the TPDT
moiety. Several derivatives of TPDT-TTP afford metallic
cation radical salts. This is the first example of metallic
salts in which the donors possess the TPDT moiety. The
results described here indicate that fusion of two donor
units is a viable strategy for the formation of metallic
molecular complexes.
donor acceptor D:Aa
νCN
σ
rt, S cm-1 c
Ea, eV
0.019
0.021
0.009-0.032
b
1a
1c
TCNQ
I3
1:1
2:1
1:1
5:3
5:4
3:2
5:3
5:3
2:1
3:2
1:1
e
2196 37
6.0
1.8
TCNQ
ClO4
BF4
ReO4
PF6
AsF6
SbF6
I3
TCNQ
ClO4
BF4
PF6
2195
1.0 × 10-1 d 0.090
1.5d
0.067
0.14
TMI ) 170 K
TMI ) 150 K
TMI ) 250 K
0.064
TMI ) 230 K
0.11
0.026
0.15
0.15
TMI ) 230 K
0.036
0.034
0.062
0.056
0.039
1.3 × 10-2
53d
12d
16
4.0 × 10-1
1d
2196 13
2.8 × 10-1 d
e
e
20d
6.4 × 10-2 d
2.8 × 10-2 d
3.2
AsF6
I3
TCNQ
I3
TCNQ
I3
TCNQ
I3
e
Exp er im en ta l Section
4:1
4:3
3:2
7:4
5:3
4:3
5:4
4:3
Gen er a l. THF was freshly distilled under argon over
sodium and benzophenone prior to use. Triethyl phosphite
was distilled under argon by fractional distillation. Mixed
xylene was dried and distilled under argon over CaH2.
4,5-(Tetr a h yd r oth iop yr a n -4-ylid en em eth ylen ed ith io)-
1,3-d ith iole-2-th ion e (6). To a solution of 4,5-(diethoxyphos-
phinylmethylenedithio)-1,3-dithiole-2-thione (3) (1.34 g, 3.88
mmol) and tetrahydrothiopyran-4-one (4) (498 mg, 4.29 mmol)
in 140 mL of dry THF was added dropwise 0.5 M LDA (7.80
mL, 3.90 mmol) for 20 min at -78 °C under argon. The
resultant precipitate was filtered off and washed with water
and then with MeOH and dried in vacuo. The THF filtrate
was directly column chromatographed on silica gel with
dichloromethane as the eluent and evaporated. The residue
was column chromatographed again on silica gel with CS2 as
the eluent. Compound 6 (809 mg, 2.62 mmol) was totally
obtained as yellow microcrystals in 67% yield: mp 215 °C dec
(recrystallized from CS2-EtOH); IR (KBr) ν (cm-1) 1594, 1490
2a
2b
2c
2195
2183
2197
2.6 × 10-1
4.9 × 10-1
1.2 × 10-1
3.7 × 10-1
1.1
2.2 × 10-1
0.063
0.079
2d
I3
1.2 × 10-1
a
b
Determined based on elemental analyses. From IR spectra.
c Measured on a compressed pellet using the four-probe technique.
d
Measured on a single crystal. e Not determined because adequate
quantity of samples for elemental analyses could not be obtained.
1
(CdC), 1419, 1251, 1177, 1070 (C)S); H-NMR (CS2-CDCl3,
90 MHz) δ 2.76-2.38 (m, 8H); MS m/ z 308 (M+). Anal. Calcd
for C9H8S6: C, 35.04; H, 2.61; S, 62.35. Found: C, 34.92; H,
2.44; S, 62.50.
4,5-[(2,6-Diph en yltetr ah ydr oth iopyr an -4-yliden e)m eth -
ylen ed ith io]-1,3-d ith iole-2-th ion e (7). Compound 7 was
obtained in 85% by the similar method as mentioned above
from 3 and 2,6-diphenyltetrahydrothiopyran-4-one (5): orange
microcrystals; mp 237-238 °C dec (recrystallized from CS2-
EtOH); IR (KBr) ν (cm-1) 1600, 1513, 1490 (CdC), 1196, 1067
(C)S); 1H-NMR (CS2-acetone-d6, 90 MHz) δ 7.4-7.1 (m, 10H),
4.1-3.9 (m, 2H), 2.9-2.4 (m, 4H); MS m/ z 460 (M+). HRMS
m/ z Calcd for C21H16S6: 459.9576. Found: 459.9551.
4,5-(Tetr a h yd r oth iop yr a n -4-ylid en em eth ylen ed ith io)-
1,3-d ith iol-2-on e (8). To a solution of 6 (600 mg, 1.94 mmol)
in a mixture of chloroform (45 mL) and acetic acid (45 mL)
was added mercury(II) acetate (1.55 g, 4.86 mmol) under
argon, and the reaction mixture was stirred at room temper-
ature for 2 h. The resultant white precipitate was filtered off
and washed with CS2. The filtrate was washed five times with
water to remove acetic acid. The organic layer was dried over
Na2SO4 and evaporated. After chromatographic separation on
silica gel with CS2, 8 (521 mg, 1.78 mmol) was obtained as
greenish white microcrystals in 92% yield: mp 177 °C dec
(recrystallized from CS2-EtOH); IR (KBr) ν (cm-1) 1676
(CdO), 1590 (C)C), 1425, 1276; 1H-NMR (CS2-C6D6, 90M Hz)
δ 2.6-2.1 (m, 8H); MS m/ z 292 (M+). Anal. Calcd for C9H8-
OS5: C, 36.96; H, 2.76; S, 54.81. Found: C, 36.72; H, 2.65; S,
54.98.
F igu r e 5. Conducting behavior of metallic cation radical salts
of 1c.
5). The metal to semiconductor transition temperature
(TMI ) 250 K) of the SbF6 salt was higher than those of
the others due to the conductivity measurement being
taken on a compressed pellet. We believe that its TMI
becomes lower in a single crystal. On the other hand,
the TCNQ complex and I3 salt of 1d on compressed pellets
also displayed metallic conductivity down to ca. 230 K,
while most of the salts with tetrahedral and octahedral
anions showed low conductivities of 10-1-10-2 S cm-1 in
single crystals. Diphenyl-substituted derivatives 2 af-
forded poorly conducting TCNQ complexes and I3 salts
(σrt ) 10-1-101 S cm-1 on compressed pellets) compared
to the corresponding 1, all of which were semiconductors
with Ea values of 0.034-0.079 eV. It is noteworthy that
2b gave a relatively high conducting TCNQ complex and
I3 salt (σrt ) 10-1 S cm-1) in spite of the presence of
strongly electron-withdrawing methoxycarbonyl groups.
4,5-[(2,6-Diph en yltetr ah ydr oth iopyr an -4-yliden e)m eth -
ylen ed ith io]-1,3-d ith iol-2-on e (9). Compound 9 was ob-
tained in 90% by the similar method as mentioned above from
7: greenish white microcrystals; mp 179 °C dec (recrystallized
from CS2-EtOH); IR (KBr) ν (cm-1) 1683 (CdO), 1596, 1493
1
(C)C), 1450, 1253; H-NMR (CS2-C6D6, 90 MHz) δ 7.4-7.1
(m, 10H), 4.1-3.7 (m, 2H), 2.9-2.3 (m, 4H); MS m/ z 444 (M+).
HRMS m/ z Calcd for C21H16OS5: 443.9804. Found: 443.9674.
Anal. Calcd for C21H16OS5: C, 56.72; H, 3.63; S, 36.05.
Found: C, 56.53; H, 3.47; S, 35.81.

Novel Bis-Fused π-Electron Donors for Organic Metals
J . Org. Chem., Vol. 61, No. 11, 1996 3655
2-[4,5-Bis(m et h oxyca r b on yl)-1,3-d it h iol-2-ylid en e]-5-
(tetr a h yd r oth iop yr a n -4-ylid en e)-1,3,4,6-tetr a th ia p en ta -
len e (11b). Compound 8 (140 mg, 0.480 mmol) and 4,5-
bis(methoxycarbonyl)-1,3-dithiole-2-thione (10b) (252 mg, 1.01
mmol) was heated in triethyl phosphite (12 mL) at 80 °C under
argon for 2 h. After the reaction mixture was cooled to room
temperature, the resultant brown precipitate was filtered off,
washed with n-hexane, and then dried in vacuo. Further
purification could not be carried out because of its extremely
low solubility for the common solvents. Compound 11b (174
mg, 0.352 mmol) was obtained as dark brown powder in 73%
yield: mp 225 °C dec; IR (KBr) ν (cm-1) 1751, 1736 (CdO),
sample was obtained after recrystallization from chloroben-
zene: mp 217-218 °C dec; IR (KBr) ν (cm-1) 1746, 1721 (CdO),
1574 (C)C), 1434, 1250 (CsO); HRMS m/ z Calcd for
C16H10O4S7: 489.8623. Found: 489.8608; Anal Calcd for C16
H10O4S7: C, 39.16; H, 2.05. Found: C, 39.43; H, 2.14.
-
The other derivatives of 1 and 2 were obtained by the similar
procedure mentioned above.
2-[4,5-Bis(m eth ylth io)-1,3-d ith iol-2-ylid en e]-5-(th iop y-
r a n -4-ylid en e)-1,3,4,6-tetr a th ia p en ta len e (1c). Obtained
in 79% from 11c after column chromatography on silica gel
with CS2 as the eluent; orange platelike crystal: mp 183-184
°C dec (recrystallized from 1,2-dichloroethane); IR (KBr) ν
(cm-1) 1514, 1502 (CdC), 1421, 1295; UV (CHCl3) λ (nm) (log
ꢀ) 401 (4.06), 368 (4.34), 343 (4.38), 323 (4.36), 266 (4.15); 1H-
NMR (CS2-acetone-d6, 90M Hz) δ 6.12 (d, J ) 5.4 Hz, 4H),
2.40 (s, 6H); MS m/ z 466 (M+). Anal. Calcd for C14H10S9: C,
36.02; H, 2.16; S, 61.81. Found: C, 35.75; H, 2.14; S, 61.84.
1585 (C)C), 1439, 1269 (C-O); HRMS m/ z Calcd for C16H14
-
O4S7: 493.8936. Found: 493.8949.
The other derivatives of 11 and 12 were obtained by the
similar procedure mentioned above.
2-[4,5-Bis(m eth ylth io)-1,3-d ith iol-2-ylid en e]-5-(tetr a h y-
d r oth iop yr a n -4-ylid en e)-1,3,4,6-tetr a th ia p en ta len e (11c).
Obtained in 44% from 8 and 10c after column chromatography
on silica gel with CS2: reddish orange microcrystals; mp 183
2-(4,5-Eth ylen ed ith io-1,3-d ith iol-2-ylid en e)-5-(th iop y-
r a n -4-ylid en e)-1,3,4,6-tetr a th ia p en ta len e (1d ). Obtained
in 59% from 11d after column chromatography with hot CS2
as the eluent: yellowish brown microcrystals; mp 198 °C dec
°C dec (recrystallized from chlorobenzene); IR (KBr) ν (cm-1
)
1607, 1497 (CdC), 1421, 1318, 1272; 1H-NMR (CS2-C6D6, 90
MHz) δ 2.6-2.1 (m, 8H), 2.17 (s, 6H); MS m/ z 470 (M+). Anal.
Calcd for C14H14S9: C, 35.71; H, 3.00; S, 61.29. Found: C,
35.50; H, 2.75; S, 61.27.
(recrystallized twice from chlorobenzene); IR (KBr) ν (cm-1
)
1618, 1501 (CdC), 1415, 1292; 1H-NMR (CS2-C6D6, 270 MHz)
δ 5.87 (d, J ) 5.4 Hz, 4H), 2.92 (s, 4H); MS m/ z 464 (M+).
Anal. Calcd for C14H8S9: C, 36.18; H, 1.73. Found: C, 36.46;
H, 1.87.
2-(4,5-Eth ylen ed ith io-1,3-d ith iol-2-ylid en e)-5-(tetr a h y-
d r oth iop yr a n -4-ylid en e)-1,3,4,6-tetr a th ia p en ta len e (11d ).
Obtained in 51% from 8 and 10d after washing thoroughly
with CS2 in order to eliminate bis(ethylenedithio)tetrathia-
fulvalene as the homo-coupling product of 10d : reddish brown
microcrystals; mp 204 °C dec (recrystallized from o-dichlo-
robenzene); IR (KBr) ν (cm-1) 1598, 1551 (CdC), 1411, 1334,
1274; HRMS m/ z Calcd for C14H12S9: 467.8425. Found:
467.8460; Anal. Calcd for C14H12S9: C, 35.86; H, 2.58.
Found: C, 35.75; H, 2.69.
2-[4,5-Bis(m et h oxyca r b on yl)-1,3-d it h iol-2-ylid en e]-5-
(2,6-d ip h en yltetr a h yd r oth iop yr a n -4-ylid en e)-1,3,4,6-tet-
r a th ia p en ta len e (12b). Obtained in 70% from 9 and 10b
after column chromatography on silica gel with CS2-CH2Cl2
(v/v )1:1) as the eluent; dark brown powder; mp 202-203 °C
dec (recrystallized from CS2-EtOH); IR (KBr) ν (cm-1) 1733
(CdO), 1580, 1493 (C)C), 1432, 1257 (CsO); 1H-NMR (CS2-
acetone-d6, 270 MHz) δ 7.3-7.1 (m, 10H), 4.00-3.92 (m, 2H),
3.76 (s, 6H), 2.77-2.51 (m, 4H); MS m/ z 646 (M+). Anal. Calcd
for C28H22O4S7: C, 51.98; H, 3.43; S, 34.69. Found: C, 51.81;
H, 3.39; S, 34.87.
2-[4,5-Bis(m et h ylt h io)-1,3-d it h iol-2-ylid en e]-5-(2,6-d i-
p h en yltetr a h yd r oth iop yr a n -4-ylid en e)-1,3,4,6-tetr a th ia -
p en ta len e (12c). Obtained in 40% from 9 and 10c after
column chromatography on silica gel with CS2 as the eluent;
orange microcrystals; mp 200 °C dec (recrystallized from CS2-
EtOH); IR (KBr) ν (cm-1) 1596, 1492 (CdC), 1451, 1422, 1271;
1H-NMR (CS2-acetone-d6, 90 MHz) δ 7.4-7.1 (m, 10H), 4.08-
3.84 (m, 2H), 2.74-2.48 (m, 4H), 2.40 (s, 6H); MS m/ z 622
(M+). Anal. Calcd for C26H22S9: C, 50.12; H, 3.56; S, 46.32.
Found: C, 49.83; H, 3.71; S, 46.16.
2-(4,5-E t h ylen ed it h io-1,3-d it h iol-2-ylid en e)-5-(2,6-d i-
p h en yltetr a h yd r oth iop yr a n -4-ylid en e)-1,3,4,6-tetr a th ia -
p en ta len e (12d ). Obtained in 54% from 9 and 10d after
column chromatography on silica gel with CS2 as the eluent:
light pink microcrystals; mp 225 °C dec (recrystallized from
CS2-EtOH); IR (KBr) ν (cm-1) 1598, 1492 (CdC), 1451, 1409,
1285; 1H-NMR (CS2-acetone-d6, 270 MHz) δ 7.3-7.1 (m, 10H),
4.0-3.9 (m, 2H), 3.30 (s, 4H), 2.80-2.48 (m, 4H); MS m/ z 620
(M+). Anal. Calcd for C26H20S9: C, 50.29; H, 3.25; S, 46.47.
Found: C, 50.03; H, 3.02; S, 46.60.
2-[4,5-Bis(m et h oxyca r b on yl)-1,3-d it h iol-2-ylid en e]-5-
(2,6-d ip h en ylt h iop yr a n -4-ylid en e)-1,3,4,6-t et r a t h ia p en -
ta len e (2b). Obtained in 88% from 12b after column chro-
matography on silica gel with CS2-CH2Cl2 (v/v ) 1:1) as the
eluent: brown microcrystals; mp 181-182 °C dec (recrystal-
lized from CS2-EtOH); IR (KBr) ν (cm-1) 1720 (CdO), 1577,
1486 (C)C), 1431, 1239 (CsO); UV (CHCl3) λ (nm) (log ꢀ) 427
(4.35), 347 (4.19), 262 (4.47), 250 (4.48); 1H-NMR (CS2-C6D6,
90 MHz) δ 7.5-7.3 (m, 10H), 6.29 (s, 2H), 3.59 (s, 6H); MS
m/ z 642 (M+). Anal. Calcd for C28H18O4S7: C, 52.31; H, 2.82;
S, 34.91. Found: C, 52.26; H, 2.72; S, 34.88.
2-[4,5-Bis(m et h ylt h io)-1,3-d it h iol-2-ylid en e]-5-(2,6-d i-
p h en ylt h iop yr a n -4-ylid en e)-1,3,4,6-t et r a t h ia p en t a len e
(2c). Obtained in 98% from 12c after column chromatography
on silica gel with CS2 as the eluent: red microcrystals; mp
161 °C dec (recrystallized from CS2-EtOH); IR (KBr) ν (cm-1
)
1593, 1484 (CdC), 1443, 1303, 1233; UV (CHCl3) λ (nm) (log
1
ꢀ) 428 (4.37), 354 (4.27), 253 (4.51); H-NMR (CS2-C6D6, 90
MHz) δ 7.5-7.3 (m, 10H), 6.26 (s, 2H), 2.21 (s, 6H). Anal.
Calcd for C26H18S9: C, 50.45; H, 2.93; S, 46.62. Found: C,
50.05; H, 2.85; S, 46.66.
2-(4,5-E t h ylen ed it h io-1,3-d it h iol-2-ylid en e)-5-(2,6-d i-
p h en ylt h iop yr a n -4-ylid en e)-1,3,4,6-t et r a t h ia p en t a len e
(2d ). Obtained in 64% from 12d after column chromatography
on silica gel with CS2 as the eluent: reddish brown platelike
crystals; mp 191-192 °C dec (recrystallized from CS2-EtOH);
IR (KBr) ν (cm-1) 1594, 1484 (CdC), 1443, 1287, 1234; UV
(CHCl3) λ (nm) (log ꢀ) 430 (4.36), 356 (4.28) 340 (4.26), 250
(4.52); 1H-NMR (CS2-acetone-d6, 90 MHz) δ 7.6-7.2 (m, 10H),
6.30 (s, 2H), 3.34 (s, 4H); MS m/ z 616 (M+). Anal. Calcd for
C26H16S9: C, 50.62; H, 2.61; S, 46.77. Found: C, 50.50; H,
2.60; S, 46.72.
2-(1,3-Dith iol-2-yliden e)-5-(th iopyr an -4-yliden e)-1,3,4,6-
tetr a th ia p en ta len e (1a ). A mixture of 1b (95.6 mg, 0.195
mmol) and LiBr‚H2O (204 mg, 1.95 mmol) in HMPA (30 mL)
was vacuumed for 1 h to eliminate the trace of amines of the
solvent. The mixture was stirred at 90 °C for 1 h and then at
130°C for 1 h under bubbling argon gas. The reaction mixture
was cooled to room temperature and extracted for three times
with benzene. The organic layer was washed three times with
distilled water and dried over Na2SO4, and the solvent was
evaporated in vacuo. The residue was column chromato-
graphed on silica gel with CS2 as the eluent and recrystallized
from chlorobenzene to afford 1a (32.5 mg, 0.087 mmol) as
orange microcrystals in 45% yield: mp 200-201 °C dec; IR
(KBr) ν (cm-1) 1541, 1497 (CdC), 1296, 1205; UV (CHCl3) λ
2-[4,5-Bis(m et h oxyca r b on yl)-1,3-d it h iol-2-ylid en e]-5-
(th iop yr a n -4-ylid en e)-1,3,4,6-tetr a th ia p en ta len e (1b). A
solution of DDQ (153 mg, 0.676 mmol) in mixed xylene (30
mL) was added dropwise for 20 min to a solution of 11b (120
mg, 0.243 mmol) in mixed xylene (80 mL) at reflux under
argon. After additional 10 min, the hot reaction mixture was
filtered and the filtrate was ice-cooled. The resultant precipi-
tate was filtered off and washed with acetonitrile and n-hexane
and dried in vacuo. Compound 1b (99.1 mg, 0.202 mmol) was
obtained as brown solid in 83% yield. The analytically pure
1
(nm) (log ꢀ) 402 (4.04), 377 (4.30), 328 (4.37), 275 (4.08); H-
NMR (CS2-C6D6, 90 MHz) δ 6.75 (s, 2H), 5.86 (d, J ) 5.4 Hz,
4H); MS m/ z 374 (M+). HRMS m/ z Calcd for C12H6S7:

3656 J . Org. Chem., Vol. 61, No. 11, 1996
Misaki et al.
373.8514. Found: 373.8539. Anal Calcd for C12H6S7: C,
38.48; H, 1.61. Found: C, 38.75; H, 1.49.
generator. Cell constants were determined from 25 carefully
centered reflections in the range 20.33 < 2θ < 26.96°.
Intensity data were collected to a maximum 2θ value of 60.8°
by the ω-2θ scan technique. The total number of independent
reflections measured was 5546, of which 1413 were considered
to be observed [I > 3.00σ(I)]. The structure was solved by
direct methods (SHELXS86).20,21 The non-hydrogen atoms
were refined anisotropically. Hydrogen atoms were included
but not refined. The structure was refined by full-matrix least
squares to R ) 0.068, Rw ) 0.074.
Electr och em ica l Mea su r em en t. The cyclic voltammetry
system used in this experiment was composed of a Yanaco
polarographic analyzer Model P-1100, a Graphtec X-Y recorder
Model WX-1200. The measurement was performed in ben-
zonitrile containing 0.1 M tetra-n-butylammonium perchlorate
as a supporting electrolyte by use of platinum working and
counter electrodes, and a Yanaco saturated calomel electrode
(SCE) Model MR-P2A as reference electrode (scan rate: 50
mV/s).
2-(1,3-Dit h iol-2-ylid en e)-5-(2,6-d ip h en ylt h iop yr a n -4-
ylid en e)-1,3,4,6-tetr a th ia p en ta len e (2a ). Compound 2a
was obtained in 62% by the similar method as mentioned
above from 2b after column chromatography on silica gel with
CS2 as the eluent: reddish brown microcrystals; mp 169 °C
dec (recrystallized from CS2-EtOH); IR (KBr) ν (cm-1) 1596,
1507, 1485 (CdC), 1443, 1297, 1253; UV (CHCl3) λ (nm) (log
ꢀ) 430 (4.33), 350 (4.20), 252 (4.44); 1H-NMR (CS2-acetone-
d6, 90 MHz) δ 7.6-7.2 (m, 10H), 6.49 (s, 2H), 6.31 (s, 2H); MS
m/ z 526 (M+). Anal. Calcd for C24H14S7: C, 54.72; H, 2.68;
S, 42.60. Found: C, 54.98; H, 2.96; S, 42.68.
Gen er a l P r oced u r e for P r ep a r a tion of TCNQ Com -
p lexes a n d I3 Sa lt s. Hot solutions of donor molecule and
TCNQ or tetra-n-butylammonium triiodide in chlorobenzene
or 1,1,2-trichloroethane were mixed, and the resultant pre-
cipitate was collected by filtration. TCNQ complex was
washed with CS2 and CH3CN and dried in vacuo. I3- salt was
washed with CS2 and MeOH and dried in vacuo. The ratio of
donor and TCNQ or I3- was determined by elemental analysis.
Gen er a l P r oced u r e for P r ep a r a tion of Ca tion Ra d ica l
Sa lts. Cation radical salts of 1c and 1d were prepared by
electrochemical oxidation in chlorobenzene-ethanol (17:1, v/v)
at a constant current of 0.1-0.5 µA in the presence of the
corresponding tetra-n-butylammonium salts at 20 °C for 1c
and 50 °C for 1d for 1-3 weeks. The crystals obtained were
washed with EtOH and were air-dried at room temperature.
The ratio of donor and anion was determined by elemental
analysis.
Electr ica l Con d u ctivity Mea su r em en t. Electrical con-
ductivity with four-probe technique was measured on using
Huso Electro Chemical System HESS 994 Multi-channel four-
terminal conductometer. Electrical contacts were achieved
with a gold paste.
Ack n ow led gm en t. This work is partially supported
by Grant-in-Aid for Scientific Research No. 06243215
and No. 00063275 from the Ministry of Education,
Science, and Culture of J apan. One of the authors
(H.F.) is indebted to the J SPS Research Fellowships for
Young Scientists.
X-r a y Diffr a ction a l An a lysis of 1c. Crystal data: C14
-
H10S9, M ) 466.77, monoclinic, space group P21/c, a ) 5.21(8),
b ) 11.11(6), c ) 30.82(6) Å, â ) 92.0(6)°, V ) 1784(28) Å3, Z
) 4, Dc ) 1.737 g cm-3, Mo KR radiation, λ ) 0.71069 Å, µ )
11.10 cm-1, F(000) ) 952.00. A dark red plate crystal of
dimensions 0.94 × 0.16 × 0.03 mm crystallized from CS2-
benzonitrile was used for X-ray measurement at 293 K on a
Rigaku AFC7R diffractometer equipped with graphite mono-
chromated MoKR radiation and a 12 kW rotating anode
J O9516244
(20) Sheldrick, G. M. Crystallographic Computing 3; Oxford Uni-
versity Press: New York, 1985; p 175.
(21) The author has deposited atomic coordinates for this structure
with the Cambridge Crystallographic Data Centre. The coordinates
can be obtained, on request, from the Director, Cambridge Crystal-
lographic Data Centre, 12 Union Road, Cambridge, CB2 1EZ, UK.