Novel selenocycle-fused TTF-type of electron donors forming conducting molecular complexes: Bis(ethyleneseleno)tetrathiafulvalene (BES-TTF), diselenolotetrathiafulvalene (DS-TTF), and bis(ethyleneseleno)tetraselenafulvalene (BES-TSF)

Article abstract of DOI:10.1021/jo981024f

The title selenocycle-fused tetrathiafulvalene derivatives (BES-TTF and DS-TTF) and tetraselenafulvalene derivative (BES-TSF) have been synthesized as novel electron donors, and their conducting molecular complexes have been studied. Although DS-TTF formed only semiconducting complexes, BES-TTF and BES-TSF gave metallic complexes with various electron acceptors, such as TCNQ, ClO₄^-, PF₆^-, and AsF₆^-. Among them, the TCNQ complex of BES-TSF showed an extraordinarily high room-temperature conductivity of 2700 ± 500 S cm^-1, which is of the highest class for a molecular complex. The complexes of BES-TTF underwent a typical metal-to-insulator transition at low temperature, characteristic of one-dimensional organic metals. On the other hand, complexes of BES-TSF were less temperature-dependent and remained highly conducting, even down to cryogenic temperature. The different behaviors of the three donors are discussed on the basis of the crystal structures of their representative complexes as elucidated by X-ray crystallographic analyses.

Full text of DOI:10.1021/jo981024f

J . Org. Chem. 1998, 63, 8865-8872
8865
Novel Selen ocycle-F u sed TTF -Typ e of Electr on Don or s F or m in g
Con d u ctin g Molecu la r Com p lexes:
Bis(eth ylen eselen o)tetr a th ia fu lva len e (BES-TTF ),
Diselen olotetr a th ia fu lva len e (DS-TTF ), a n d
Bis(eth ylen eselen o)tetr a selen a fu lva len e (BES-TSF )
Tetsuya J igami, Kazuo Takimiya, and Tetsuo Otsubo*
Department of Applied Chemistry, Faculty of Engineering, Hiroshima University,
Higashi-Hiroshima 739-8527, J apan
Yoshio Aso
Institute for Fundamental Research of Organic Chemistry, Kyushu University, Hakozaki, Higashi-ku,
Fukuoka 812-8581, J apan
Received May 29, 1998
The title selenocycle-fused tetrathiafulvalene derivatives (BES-TTF and DS-TTF) and tetrasel-
enafulvalene derivative (BES-TSF) have been synthesized as novel electron donors, and their
conducting molecular complexes have been studied. Although DS-TTF formed only semiconducting
complexes, BES-TTF and BES-TSF gave metallic complexes with various electron acceptors, such
-
as TCNQ, ClO4-, PF6-, and AsF6
. Among them, the TCNQ complex of BES-TSF showed an
extraordinarily high room-temperature conductivity of 2700 ( 500 S cm-1, which is of the highest
class for a molecular complex. The complexes of BES-TTF underwent a typical metal-to-insulator
transition at low temperature, characteristic of one-dimensional organic metals. On the other hand,
complexes of BES-TSF were less temperature-dependent and remained highly conducting, even
down to cryogenic temperature. The different behaviors of the three donors are discussed on the
basis of the crystal structures of their representative complexes as elucidated by X-ray crystal-
lographic analyses.
In tr od u ction
endowed with increased bandwidth and enhanced di-
mensionality owing to stronger heteroatomic interac-
tions.5 In this connection, the heretofore unknown
selenocyclic analogues of BET-TTF and DT-TTF, bis-
(ethyleneseleno)tetrathiafulvalene (BES-TTF) and dise-
lenolotetrathiafulvalene (DS-TTF), are of great interest.
Moreover, bis(ethyleneseleno)tetraselenafulvalene (BES-
TSF) is expected to be a more promising electron donor.
Concerning selenophene-annulated TTF derivatives, there
have been two reports on symmetrical DS-TTF6 and
selenolo-bisTTF;7 however, the former described no com-
plex, and the latter described only a conducting complex
with TCNQ. We now report the synthesis and properties
of the three selenocycle-fused TTF-type electron donors
and their conducting complexes.8
Since the discovery of numbers of superconductors
based on bis(ethylenedithio)tetrathiafulvalene (BEDT-
TTF),1 much attention has centered on the heterocycle-
fused modifications of TTF-type electron donors.2 The
fused heterocyclic rings play a considerably important
role in the intermolecular interactions and, accordingly,
conductivities of the derived charge-transfer complexes.
Bis(ethylenethio)tetrathiafulvalene (BET-TTF) and dithi-
enotetrathiafulvalene (DT-TTF), developed early by En-
gler’s group,3 may have been among such potential
heterocycle-fused TTF donors, but their complexes were
studied only with TCNQ. Recently Rovira and co-
workers have reported that BET-TTF behaves as a
superior electron donor, forming metallic radical cation
salts.4 It is well-known that replacement of the sulfur
atoms of TTF donors with selenium is one of the most
promising modifications for searching for novel potential
electron donors, because the incorporated selenium atoms
can serve to make advantageous organic metals that are
(4) (a) Rovira, C.; Veciana, J .; Santalo´, N.; Tarre´s, J .; Cirujeda, J .;
Molins, E.; Llorca, J .; Espinosa, E. J . Org. Chem. 1994, 59, 3307-
3313. (b) Tarre´s, J .; Santalo´, N.; Mas, M.; Molins, E.; Veciana, J .;
Rovira, C.; Yang, S.; Lee, H.; Cowan, D. O. Chem. Mater. 1995, 7,
1558-1567. (c) Rovira, M. C.; Novoa, J . J .; Tarre´s, J .; Rovira, C.;
Veciana, J .; Yang, S.; Cowan, D. O.; Canadell, E. Adv. Mater. 1995, 7,
1023-1027. (d) Rovira, C.; Veciana, J .; Tarre´s, J .; Molins, E.; Mas,
M.; Cowan, D. O.; Yang, S. Synth. Met. 1995, 70, 883-886. (e) Ribera,
E.; Rovira, C.; Veciana, J .; Laukhin, V. N.; Canadell, E.; Vidal-Gancedo,
J .; Molins, E. Synth. Met. 1997, 86, 1993-1994. (f) Rovira, C.; Tarre´s,
J .; Ribera, E.; Veciana, J .; Canadell, E.; Molins, E.; Mas, M.; Laukhin,
V.; Doublet, M.-L.; Cowan, D. O.; Yang, S. Synth. Met. 1997, 86, 2145-
2146.
(5) Cowan, D.; Kini, A. In The Chemistry of Organic Selenium and
Tellurium; Patai, S., Ed.; J ohn Wiley & Sons: New York, 1987; Vol.
2, Chapter 12.
(6) Ketcham, R.; Ho¨rnfeldt, A.-B.; Gronowitz, S. J . Org. Chem. 1984,
49, 1117-1119.
(7) Wang, C.; Ellern, A.; Becker, J . Y.; Bernstein, J . Adv. Mater.
1995, 7, 644-646.
* To whom correspondence should be addressed (tel, +81-824-24-
7733; fax, +81-824-22-7191; E-mail, otsubo@ipc.hiroshima-u.ac.jp).
(1) For a comprehensive review on organic superconductors, see:
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
(Including Fullerenes): Synthesis, Structure, Properties, and Theory;
Prentice Hall: New J ersey, 1992.
(2) For excellent reviews on the structural modifications of TTF,
see: (a) Schukat, G.; Richter, A. M.; Fangha¨nel, E. Sulfur Rep. 1987,
7, 155-240. (b) Schukat, G.; Fangha¨nel, E. Sulfur Rep. 1993, 14, 245-
390. (c) Schukat, G.; Fangha¨nel, E. Sulfur Rep. 1996, 18, 1-294.
(3) Engler, E. M.; Patel, V. V.; Andersen, J . R.; Schumaker, R. R.;
Fukushima, A. A. J . Am. Chem. Soc. 1978, 100, 3769-3776.
10.1021/jo981024f CCC: $15.00 © 1998 American Chemical Society
Published on Web 11/10/1998

8866 J . Org. Chem., Vol. 63, No. 24, 1998
J igami et al.
Sch em e 1a
a
Reagents and conditions: (i) n-BuLi, TMEDA, THF, -70 °C;
(ii) S, 0 °C; (iii) CS2, -85 °C; (iv) Se powder, then MeI, 0 °C; (v)
HCl (aq), acetone/MeOH, rt; (vi) TsCl, pyridine, 0 °C; (vii) NaI,
DMF, 80 °C; (viii) P(OMe)3, reflux.
Sch em e 2a
Resu lts a n d Discu ssion
a
Reagents and conditions: (i) DDQ, toluene, reflux; (ii) P(OMe)3,
reflux; (iii) (MeO)2SO2, 80 °C, then HBF4 (aq), 0 °C; (iv) NaHSe,
MeOH, rt; (v) P(OMe)3, benzene, reflux.
Syn th esis. Based on the general synthetic strategy
of TTF molecules, the key intermediates for the syntheses
of BES-TTF and DS-TTF are 5,6-dihydroselenolo[2,3-d]-
1,3-dithiole-2-thione (7) and selenolo[2,3-d]-1,3-dithiole-
2-thione (8), respectively. Although the reported syn-
theses of similar sulfur intermediates for BET-TTF and
DT-TTF involve the construction of the 1,3-dithiole-2-
thione ring by conventional methods starting with thio-
lan-2-one3 or thiolan-3-one,4a these methods are not
suitable for the synthesis of the present system, because
the corresponding starting selenocyclic materials are not
readily accessible. Instead, we have developed a conve-
nient route which involves the construction of the 1,3-
dithiole-2-thione ring via cyclization reaction of a termi-
nal acetylene with sulfur and carbon disulfide,9 followed
by the construction of the selenocyclic ring, as shown in
Scheme 1. Thus, commercially available tetrahydropy-
ranyl (THP)-protected 3-butyn-1-ol (1) was treated with
n-BuLi at -70 °C in THF to generate the lithium
acetylide, which was successively reacted with elemental
sulfur and carbon disulfide. The resulting vinyl anion 2
was then reacted with selenium and subsequently
quenched by addition of methyl iodide to give THP-
protected 4-(2-hydroxyethyl)-5-methylseleno-1,3-dithiole-
2-thione (3) in 56% yield. After the THP protecting group
was removed by treatment with dilute hydrochloric acid
(88% yield), the resulting alcohol 4 was converted into
the tosylate 5 in 89% yield. The second ring formation
was achieved by a unique transalkylation reaction from
5 via a hypervalent selenium intermediate 6 promoted
by sodium iodide in DMF, giving rise to the key inter-
mediate 7 in high yield (90%). The conventional desul-
furization self-coupling of 7 promoted by trimethyl phos-
phite gave BES-TTF in 21% yield.
The precursor 8 of DS-TTF was readily prepared in
87% yield by dehydrogenation of 7 with DDQ in refluxing
toluene (Scheme 2). The subsequent self-coupling reac-
tion of 8 gave DS-TTF in 13% yield. The poor yield of
the coupling reaction was fairly improved to 42% by
alternatively using the corresponding selone 9, which was
obtained from 8 by a well-established procedure (84%).
The above synthetic method for BES-TTF and DS-TTF
was also found to be successfully applicable to the syn-
theses of the sulfur counterparts, BET-TTF and DT-TTF,
as shown in Scheme 3. Although the overall yield is
nearly equal, this new approach complements the preced-
ing two methods3,4a in terms of a large preparative scale.
The synthesis of BES-TSF was performed by a modi-
fied method, as shown in Scheme 4. Successive treat-
ment of 1 with elemental selenium, carbon diselenide,
again selenium, and finally methyl iodide similarly gave
THP-protected 4-(2-hydroxyethyl)-5-methylseleno-1,3-
diselenole-2-selone (15) in 70% yield. Differently from
BES-TTF, however, the subsequent approach from 15 to
BES-TSF failed because of the instability of the inter-
mediate, 5,6-dihydroselenolo[2,3-d]-1,3-diselenole-2-selone
(16). Alternatively, 15 was prior to the second ring
formation, coupled to the TSF derivative 17 in 93% yield;
after the THP group was deprotected by dilute hydro-
chloric acid (94% yield), the resulting diol 18 was
converted into the ditosylate 19 in 95% yield, which was
then subjected to the transalkylation reaction to give
BES-TSF in 39% yield.
(8) A preliminary report on BES-TTF and DS-TTF appeared:
J igami, T.; Takimiya, K.; Aso, Y.; Otsubo, T. Chem. Lett. 1997, 1091-
1092.
(9) (a) Mayer, R.; Gebhardt, B. Chem. Ber. 1964, 97, 1298. (b) Engler,
E. M.; Patel, V. V. J . Org. Chem. 1975, 40, 387. (c) Takimiya, K.;
Morikami, A.; Otsubo, T. Synlett 1997, 319-321.
Molecu la r Str u ctu r es. As seen in the case of the
sulfur analogues,3,4a BES-TTF, DS-TTF, and BES-TSF

TTF- and TSF-Type Electron Donors
J . Org. Chem., Vol. 63, No. 24, 1998 8867
Sch em e 3a
F igu r e 1. Molecular structure of trans-BES-TSF.
Ta ble 1. Ha lf-Wa ve Oxid a tion P oten tia ls (V)a
donor
E1/2(1)
E1/2(2)
∆E
BES-TTF
BET-TTF
DS-TTF
DT-TTF
BES-TSF
TTF
0.32
0.36
0.38
0.46
0.47
0.34
0.60
0.49
0.66
0.68
0.71
0.79
0.74
0.71
0.98
0.78
0.34
0.32
0.33
0.33
0.27
0.37
0.38
0.29
DB-TTF
TSF
a
Cyclic voltammetry was carried out at a scan rate of 400 mV
s-1 with Pt working and counter electrodes and an Ag/AgCl
reference electrode in 10-3 mol dm-3 benzonitrile solution contain-
ing 10-1 mol dm-3 tetrabutylammonium perchlorate as supporting
electrolyte.
a
Reagents and conditions: (i) n-BuLi, TMEDA, THF, -70 °C;
(ii) S, 0 °C; (iii) CS2, -85 °C; (iv) MeSCN, 0 °C; (v) HCl (aq),
acetone/MeOH, rt; (vi) TsCl, pyridine, 0 °C; (vii) NaI, DMF, 120
°C; (viii) DDQ, toluene, reflux; (ix) P(OMe)3, reflux.
but its structural confirmation by an X-ray crystal-
lographic analysis was fruitless because the crystal was
found to comprise orientationally disordered molecules.
Cyclic Volta m m etr y. The cyclic voltammetry of
BES-TTF, DS-TTF, and BES-TSF showed two reversible,
one-electron redox waves. The half-wave oxidation po-
tentials are summarized together with those of the
related compounds in Table 1. BES-TTF has slightly
lower oxidation potentials than TTF and BET-TTF,
indicating the enhancement of its electron-donating
ability by fusion of the dihydroselenolo rings. This is the
case with the electron-donating ability of BES-TSF
relative to TSF. The fused selenolo rings of DS-TTF, on
the contrary, serve to heighten the oxidation potentials.
This is in harmony with a general tendency that the
fusion of aromatic rings to TTF leads to weaken its donor
ability, as exemplified by the oxidation potentials of DT-
TTF and dibenzotetrathiafulvalene (DB-TTF). However,
Sch em e 4a
a
Reagents and conditions: (i) n-BuLi, TMEDA, THF, -70 °C;
(ii) Se, 0 °C; (iii) CSe2, Se, -70 °C; (iv) MeI, 0 °C; (v) P(OMe)3,
benzene, reflux; (vi) HCl (aq), THF/MeOH, rt; (vii) TsCl, pyridine,
0 °C; (viii) NaI, DMF, 80 °C.
consist of a mixture of two structural isomers with
different symmetry, i.e., cis (C2v) and trans (C2h). This
was confirmed by the observation of two kinds of signals
(1:1 integral ratio) with slightly different chemical shifts
for the methylene protons in the 1H NMR spectra of BES-
TTF and BES-TSF; however, the isomeric selenophene
proton signals of DS-TTF were indistinguishable. The
isomeric separation of BES-TTF and DS-TTF with chro-
matographic and fractional crystallization techniques
failed, whereas recrystallization of the isomeric mixture
of BES-TSF from chlorobenzene gave two kinds of
crystals, reddish orange plates and dark red needles,
which corresponded to each of the structural isomers.
Both isomers are stable in the crystal state, but readily
convertible into each other in solution.10 An X-ray
crystallographic analysis confirmed the reddish orange
plate to be the trans isomer, as shown in Figure 1. From
this, it follows that the dark red needle is the cis isomer,
the perturbation effect of the fused selenolo rings is not
so marked, since the aromaticity of selenophene is not
so large as those of benzene and thiophene; thus, DS-
TTF still stays in a strong class of electron donors.
Molecu la r Com p lexes. BES-TTF formed crystalline
molecular complexes with TCNQ by a diffusion method
and with inorganic anions, such as ClO4-, PF6-, and
AsF6-, by an electrocrystallization method. The proper-
ties of the resulting complexes are summarized together
with those of the complexes of the other donors in Table
2. The TCNQ complex shows a high conductivity of 150
S cm-1 at room temperature. In variable-temperature
measurements, the conductivity increases with lowering
temperature, reaches a maximum (270 S cm-1) at 110
K, where a typical metal-to-insulator transition observed
for the TTF-TCNQ family11 occurs, and then falls mono-
(10) Souizi, A.; Robert, A.; Batail, P.; Ouahab, L. J . Org. Chem. 1987,
52, 1610-1611.
(11) Etemad, S.; Penney, T.; Engler, E. M.; Scott, B. A.; Seiden, P.
E. Phys. Rev. Lett. 1975, 34, 741-744 and references therein.

8868 J . Org. Chem., Vol. 63, No. 24, 1998
Ta ble 2. Con d u ctivities of Molecu la r Com p lexes of BES-TTF , DS-TTF , a n d BES-TSF a
J igami et al.
donor
acceptor
TCNQ
appearance
D:Ab
σ
rt (S cm-1
)
remark
metallic
metallic
metallic
metallic
semiconductive (Ea ) 0.064 eV)
semiconductive
metallic
metallic
metallic
Tmaxc (K) σmax (S cm-1
)
σ4.2K (S cm-1
)
BES-TTF
BES-TTF
BES-TTF
BES-TTF
DS-TTF
black needles
black plates
black plates
1:1
2:1
2:1
2:1
1:1
1:1
1:1
150
280
200
60
110
110
240
50
270
530
240
150
6.4 × 10-2
<10-4
<10-4
1.7
-
ClO4
-
PF6
-
AsF6
black plates
TCNQ
black needles
black needles
black plates
red brown leaflets
red brown leaflets
0.2
-
DS-TTF
ClO4
5 × 10-5
2700
100
BES-TSF
BES-TSF
BES-TSF
TCNQ
40
50
9800
190
4700
140
11
-
ClO4-
3:2:1(PhCl)d
2:1:1(PhCl)d
AsF6
100
100
110
a
b
Conductivities were measured on a single crystal with a four-probe method. Determined on the basis of elemental analyses or X-ray
crystallographic analyses. c Temperature for the highest conductivity. Additional inclusion of a chlorobenzene from solvent.
d
BES-TSF‚TCNQ is comparable to or more than these
values. A comparison with the conductivity of HMTSF‚
TCNQ15 (1391-2178 S cm-1) suggests contribution of the
outer selenium atoms of BES-TSF to the high conductiv-
ity. As the temperature is lowered, the conductivity rises
steadily and reaches a maximum at around 40 K, which
is about 3 times as large as the room-temperature value.
With further cooling, the conductivity drops gradually,
but still remains higher, even at 4.2 K, than the room-
-
temperature value (see also Figure 2). The ClO4 and
-
AsF6 complexes of BES-TSF show room-temperature
conductivities, whose magnitudes are similar to those of
the radical cation salts of BES-TTF, but also less tem-
perature-dependent and highly conducting down to cryo-
genic temperature. This low-temperature, semimetallic
behavior is reminiscent of similar behavior previously
F igu r e 2. Normalized resistance vs temperature plots for the
complexes of BES-TTF (a-c) and BES-TSF (d-f) with accep-
found for the TNAP12 and TCNQ15 complexes of HMTSF.
tors: (a) ClO4, (b) TCNQ, (c) AsF6, (d) AsF6, (e) ClO4, (f) TCNQ.
The plots are displaced upward successively by 0.5 F/Frt unit
from the bottom plot.
tonically at further lower temperatures (Figure 2). The
radical cation salts also show high conductivities with
similar temperature-dependent behavior. The magni-
Cr ysta l Str u ctu r es of Molecu la r Com p lexes. To
understand the different conductivity behaviors of the
tude of these conductivities is roughly close to that for
the complexes of BET-TTF.4 This indicates that, against
molecular complexes of the three present donors, the
our expectation, BES-TTF exerts no selenium substitu-
crystal structures of their representative complexes,
(BES-TTF)2‚AsF6, DS-TTF‚TCNQ, and BES-TSF‚TCNQ,
were elucidated by X-ray crystallographic analyses. The
crystal structure of the (BES-TTF)2‚AsF6 complex com-
prises segregated stacking columns along the b-axis; the
donor molecules, trans-rich in 70% and disordered in
30%, are stacked in a zigzag fashion with alternate
tion effect on the formation of its conducting complexes.
In contrast to BES-TTF, DS-TTF formed semiconduct-
ing complexes with TCNQ and ClO4-. The room-tem-
perature conductivity (0.20 S cm-1) of the TCNQ complex
is much lower, by an order of 103 in magnitude, than the
-
value of BES-TTF‚TCNQ. In addition, the ClO4 salt
shows a poor conductivity of 10-5 S cm-1. These results
average intervals of 3.62 and 3.65 Å (Figure 3a). This
suggest different crystal structures between the DS-TTF
crystal structure is essentially isostructural to that of
complexes and the above BES-TTF complexes (vide
(BET-TTF)2‚AsF6 reported by Rovira and co-workers.4b
However, there are subtle differences in intermolecular
infra).
BES-TSF, like BES-TTF, formed metallic complexes
interactions between the two structures: the average
with TCNQ, ClO4-, and AsF6-. In particular, the BES-
stacking distances of the BES-TTF salt are a little greater
than those (3.55 and 3.62 Å) of the BET-TTF salt. In
TSF‚TCNQ complex shows a remarkably high room-
temperature conductivity of 2700 ( 500 S cm-1 (10
addition, nonbonded S‚‚‚S contacts (3.79, 3.65, and 3.78
samples). Although great interest has been placed on
Å) between the neighboring BES-TTF donors in the
the discovery of novel superconductors based on the TTF
transverse direction are a little greater than the corre-
family, the development of molecular complexes with the
sponding contacts (3.51, 3.56, 3.58, and 3.62 Å) of the
highest conductivities under ambient conditions is also
very important. The room-temperature conductivities of
(12) Bechgaard, K.; J acobsen, C. S.; Andersen, N. H. Solid State
molecular complexes, even superconductive ones, are still
very low as compared to those of the metal elements and
rarely exceed 103 S cm-1. To the best of our knowledge,
the highest conductivities of molecular complexes ever
reported have been for HMTSF‚TNAP (2400 ( 600 S
cm-1),12 TTeF‚TCNQ (2200 ( 300 S cm-1),13 and (DMET)2‚
Au(CN)2 (2500 S cm-1).14 The present conductivity of
Commun. 1978, 25, 875-879.
(13) Cowan, D. O.; Mays, M. D.; Kistenmacher, T. J .; Poehler, T.
O.; Beno, M. A.; Kini, A. M.; Williams, J . M.; Kwok, Y.-K.; Carlson, K.
D.; Xiao, L.; Novoa, J . J .; Whangbo, M.-H. Mol. Cryst. Liq. Cryst. 1990,
181, 43-58.
(14) Kikuchi, K.; Kikuchi, M.; Namiki, T.; Saito, G.; Ikemoto, I.;
Murata, K.; Ishiguro, T.; Kobayashi, K. Chem. Lett. 1987, 931-934.
(15) Bloch, A. N.; Cowan, D. O.; Bechgaard, K.; Pyle, R. E.; Banks,
R. H.; Poehler, T. O. Phys. Rev. Lett. 1975, 34, 1561-1564.

TTF- and TSF-Type Electron Donors
J . Org. Chem., Vol. 63, No. 24, 1998 8869
F igu r e 3. Crystal structure of (BES-TTF)2‚AsF6: (a) a-axis
projection and (b) interstacking contacts. Selected nonbonded
interactions are (i) 3.95, (ii) 4.01, (iii) 3.62, and (iv) 3.57 Å.
F igu r e 5. Crystal structure of BES-TSF‚TCNQ: (a) a-axis
projection and (b) c-axis projection. Selected nonbonded inter-
actions are (i) 3.02, (ii) 3.10, (iii) 3.87, (iv) 3.67, and (v) 3.84 Å.
F igu r e 4. Crystal structure of DS-TTF‚TCNQ: Se‚‚‚Se con-
tacts (3.80 Å) are depicted by dotted lines.
BET-TTF salt. However, the BES-TTF complex benefits
from additional Se‚‚‚Se contacts (3.95 and 4.01 Å) be-
tween the dihydroselenolo rings along the stacking
direction (Figure 3a) and close Se‚‚‚S contacts (3.57 and
3.62 Å) along the transverse direction (Figure 3b). A
balance between the two opposing factors for the inter-
molecular interaction of the BES-TTF system as a whole
accounts for no selenium substitution effect for the BES-
TTF complexes.
The crystal structure of the DS-TTF‚TCNQ complex
is characterized by a mixed-stacking arrangement, where
the donor and acceptor molecules are alternately stacked
with sliding and at intervals of 3.5 Å along the c-axis
(Figure 4). This unfavorable arrangement is responsible
for the low conductivity; the value (0.2 S cm-1) is,
however, rather marked for a mixed-stacking molecular
complex, and in fact, much higher, by 2 orders of
magnitude, than that (10-3 S cm-1) of the DT-TTF‚TCNQ
complex, which was also estimated to take a mixed-
stacking crystal structure.3 This is best understood by
the presence of nonbonded Se‚‚‚Se interactions (3.80 Å)
between the donor molecules of neighboring columns
along the a-axis.
the c-axis (69.7° for BES-TTF and 56.9° for TCNQ). An
important feature of this crystal structure is that the
donor molecules strongly interact with the neighboring
molecules in a side-by-side arrangement: the selenium
atom of the TSF moiety of BES-TSF has a short trans-
verse Se‚‚‚Se contact (3.84 Å) with that of another BES-
TSF and a Se‚‚‚N contact (3.10 Å) with the nitrogen atom
of the TCNQ acceptor (Figure 5b). In addition, the outer
selenium atom, though locationally disordered, has short
contacts either with the selenium atoms of the TSF
moiety (3.67 and 3.87 Å) or with the nitrogen atom of
the acceptor (3.02 Å). This kind of arrangement mode is
quite different from that of the less conducting HMTSF-
TCNQ complex with transverse Se‚‚‚N interactions.16 It
is thus understandable that the high conductivity of BES-
TSF‚TCNQ is induced by strong heteroatomic interac-
tions not only along the stacking direction but also along
the transverse direction, which are enhanced by the
additional outer selenium atoms of BES-TSF.
Con clu sion
Among the present selenocycle-fused electron donors
developed, BES-TTF and BES-TSF have turned out to
be superior electron donors, forming various metallic
molecular complexes. Although the complexes of BES-
TTF undergo a typical metal-to-insulator transition at
The crystal structure of the BES-TSF‚TCNQ complex
with an unusually high conductivity was confirmed to
adopt segregated stacking columns (Figure 5a). The
BES-TSF molecules are uniformly stacked with sliding
and at intervals of 3.65 Å along the c-axis, and the TCNQ
molecules at intervals of 3.30 Å. The planes of both
components are tilted in opposite directions relative to
(16) Phillips, T. E.; Kistenmacher, T. J .; Bloch, A. N.; Cowan, D. O.
J . Chem. Soc., Chem. Commun. 1976, 334-335.

8870 J . Org. Chem., Vol. 63, No. 24, 1998
J igami et al.
extracted with CH2Cl2, and the extract was washed with 1 N
hydrochloric acid and then with brine and dried (MgSO4). After
concentration, column chromatography of the residue on silica
gel (CH2Cl2) followed by recrystallization from hexane/CHCl3
gave 4.0 g (89%) of 5 as yellow fine needles: mp 84-85 °C; 1H
NMR (CDCl3) δ 2.30 (s, 3H), 2.45 (s, 3H), 3.09 (t, J ) 5.9 Hz,
2H), 4.16 (t, J ) 5.9 Hz, 2H), 7.36 (d, J ) 8.3 Hz, 2H), and
7.72 (d, J ) 8.3 Hz, 2H); 13C NMR (CDCl3) δ 11.0, 21.6, 30.6,
67.9, 123.6, 127.6, 129.9, 131.8, 142.9, 145.4, and 213.0; MS
m/z 426 (M+); IR (KBr) 1063 cm-1 (CdS). Anal. Calcd for
low temperature, complexes of BES-TSF show semime-
tallic behavior down to cryogenic temperature. It is
noteworthy that the TCNQ complex of BES-TSF has an
extraordinarily high room-temperature conductivity of
2700 ( 500 S cm-1, which is of the highest class for a
molecular complex.
Exp er im en ta l Section
C
13H14O3S4Se: C, 36.70; H, 3.32. Found: C, 36.47; H, 3.29.
5,6-Dih yd r oselen olo[2,3-d ]-1,3-d ith iole-2-th ion e (7). A
Gen er a l. Melting points are uncorrected. Nuclear mag-
netic resonance spectra were measured at 400 MHz for H and
1
100 MHz for 13C with TMS as internal reference. Mass
spectral data were obtained using an electron impact ioniza-
tion procedure (70 eV). The molecular ion peaks of the
selenium-containing compounds showed a typical selenium
isotropic pattern. Elemental analyses were performed by Mr.
Hideaki Iwatani, Microanalytical Laboratory in Department
of Applied Chemistry, Faculty of Engineering, Hiroshima
University. All chemicals and solvents are of reagent grade
and were purified by conventional methods. All reactions were
carried out under a nitrogen atmosphere with dry solvents.
2-(3-Butynyloxy)tetrahydro-2H-pyran (1) was purchased from
Aldrich. Selenium powder17 and carbon diselenide18 were
prepared according to the literature procedures.
4-Meth ylselen o-5-[2-(tetr a h yd r op yr a n -2-yloxy)eth yl]-
1,3-d ith iole-2-th ion e (3). To a solution of 1 (3.1 mL, 20
mmol) and TMEDA (6.0 mL, 40 mmol) in THF (120 mL) was
added a solution of n-BuLi in hexane (1.54 M, 14 mL) at -70
°C, and the solution was stirred at the same temperature for
30 min. After addition of sulfur (640 mg, 20 mmol), the
mixture was warmed to 0 °C over a period of 1 h and stirred
for 2 h at the same temperature. The solution was again
cooled to -85 °C, and MeOH (80 mL, 2 mol), carbon disulfide
(1.2 mL, 20 mmol), and selenium powder (1.6 g, 20 mmol) were
successively added. The reaction mixture was warmed to 0
°C over a period of 2 h, stirred for 1 h, and quenched with
methyl iodide (1.25 mL, 20 mmol). After addition of water
(30 mL), the mixture was extracted with CH2Cl2, and the
extract was washed with brine and dried (MgSO4). After
concentration, column chromatography of the residue on silica
gel with CH2Cl2 gave 3.99 g (56%) of 3 as a yellow oil. An
analytical sample was obtained by further purification with
preparative GPC using CHCl3 as eluent: 1H NMR (CDCl3) δ
1.5-1.9 (m, 6H), 2.32 (s, 3H), 3.07 (m, 2H), 3.52 (m, 2H), 3.78
(m, 1H), 3.91 (m, 1H), and 4.62 (br t, J ) 3.3 Hz, 1H); 13C
NMR (CDCl3) δ 10.9, 19.2, 25.3, 30.4, 32.1, 62.1, 65.8, 98.8,
121.7, 146.8, and 214.7; MS m/z 356 (M+); IR (neat) 1063 cm-1
(CdS). Anal. Calcd for C11H16O2S3Se: C, 37.18; H, 4.54.
Found: C, 37.42; H, 4.39.
4-(2-Hyd r oxyeth yl)-5-m eth ylselen o-1,3-d ith iole-2-th i-
on e (4). A mixture of 3 (6.2 g, 17.5 mmol), 2 N hydrochloric
acid (20 mL), methanol (100 mL), and acetone (100 mL) was
stirred at rt for 12 h. Water (150 mL) was introduced, and
the mixture was extracted with CH2Cl2. The extract was
washed with brine, dried (MgSO4), and then concentrated. The
residue was subjected to column chromatography (silica gel,
9:1 CH2Cl2/AcOEt) to give 4.2 g (88%) of 4 as a yellow oil.
Further purification with preparative GPC gave an analytical
sample: 1H NMR (CDCl3) δ 1.84 (br s, 1H), 2.34 (s, 3H), 3.04
(t, J ) 5.9 Hz, 2H), and 3.84 (t, J ) 5.9 Hz, 2H); 13C NMR
(CDCl3) δ 11.0, 34.4, 61.7, 122.2, 146.2, and 214.3; MS m/z 272
(M+); IR (neat) 1059 (CdS) and 3400 cm-1 (OH). Anal. Calcd
for C6H8OS3Se: C, 26.57; H, 2.97. Found: C, 26.59; H, 2.94.
4-Met h ylselen o-5-(2-t osyloxyet h yl)-1,3-d it h iole-2-t h i-
on e (5). To a solution of 4 (2.9 g, 10.7 mmol) in pyridine (18
mL) was added tosyl chloride (4.1 g, 21 mmol) at 0 °C. After
being stirred for 12 h, the mixture was poured into ice-
containing 1 N hydrochloric acid (20 mL). The mixture was
mixture of 5 (3.03 g, 7.13 mmol) and NaI (2.14 g, 14.2 mmol)
in DMF (30 mL) was heated at 80 °C for 0.5 h. Water (30
mL) was added to the cooled mixture, which was then
extracted with CS2, and the extract was successively washed
with water and brine and finally dried (MgSO4). After
concentration, column chromatography of the residue on silica
gel with CS2 followed by recrystallization from hexane/CHCl3
gave 1.54 g (90%) of 7 as yellow needles: mp 117-117.5 °C;
1H NMR (CDCl3) δ 3.16 (t, J ) 7.8 Hz, 2H) and 3.84 (t, J )
7.8 Hz, 2H); 13C NMR (CDCl3) δ 30.4, 35.0, 125.7, 135.9, and
216.8; MS m/z 240 (M+); IR (KBr) 1053 cm-1 (CdS). Anal.
Calcd for C5H4S3Se: C, 25.10; H, 1.69. Found: C, 25.34; H,
1.67.
5,5′,6,6′-Tetr a h yd r o-∆2,2′-biselen olo[2,3-d ]-1,3-d ith iole
(BES-TTF ). A solution of 7 (1.35 g, 5.64 mmol) in trimethyl
phosphite (22 mL) was heated under reflux for 2 h. After
concentration, the residue was purified by column chroma-
tography on silica gel with CS2 followed by recrystallization
from toluene to give 251 mg (21%) of BES-TTF as reddish
1
orange needles: mp 209-210 °C dec; H NMR of the 1:1 cis
and trans isomeric mixture (CS2/CDCl3) δ 2.86 and 2.87 (each
t, J ) 7.8 Hz, 4H) and 3.78 (t, J ) 7.8 Hz, 8H); MS m/z 414
(M+). Anal. Calcd for C10H8S4Se2: C, 28.99; H, 1.95. Found:
C, 29.13; H, 1.99.
Selen olo[2,3-d ]-1,3-d ith iole-2-th ion e (8). A solution of
7 (82 mg, 0.34 mmol) and DDQ (160 mg, 0.70 mmol) in toluene
(5 mL) was refluxed for 20 h. After evaporation of the solvent,
the residue was purified by column chromatography on silica
gel with CH2Cl2 followed by recrystallization from hexane/
CHCl3 to give 70 mg (87%) of 8 as yellow prisms: mp 150-
150.5 °C; 1H NMR (CDCl3) δ 7.30 (d, J ) 5.8 Hz, 1H) and 8.29
(d, J ) 5.8 Hz, 1H); 13C NMR (CDCl3) δ 122.2, 132.7, 135.1,
140.3, and 216.0; MS m/z 238 (M+); IR (KBr) 1063 cm-1 (Cd
S). Anal. Calcd for C5H2S3Se: C, 25.32; H, 0.85. Found: C,
25.37; H, 0.84.
Selen olo[2,3-d ]-1,3-d ith iole-2-selon e (9). A mixture of
8 (69 mg, 0.29 mmol) and dimethyl sulfate (0.4 mL) was stirred
at 80 °C for 0.5 h. With cooling to 0 °C in an ice bath, 42%
fluoroboric acid (1 mL) was added, and the resulting mixture
was stirred for 5 min. To the reaction mixture were succes-
sively added anhydrous acetic acid (1 mL) and ethyl ether (10
mL). The resulting yellow precipitate was collected by filtra-
tion, washed with ethyl ether, and then dried in vacuo. It was
added in one portion to a solution of sodium hydrogenselenide
generated from NaBH4 (25 mg, 0.65 mmol) and selenium
powder (30 mg, 0.38 mmol) in MeOH (2 mL) at 0 °C. The
resulting mixture was stirred for 1 h at rt and then poured
into water (5 mL). The product was extracted with CH2Cl2,
and the extract was washed with brine and dried (MgSO4).
After concentration, column chromatography of the residue on
silica gel with CS2 followed by recrystallization from hexane/
CHCl3 gave 69 mg (84%) of 9 as orange needles: mp 160-161
1
°C; H NMR (CS2/CDCl3) δ 7.29 (d, J ) 5.8 Hz, 1H) and 8.37
(d, J ) 5.8 Hz, 1H); 13C NMR (CS2/CDCl3) δ 121.4, 135.8, 136.9,
145.0, and 204.4; MS m/z 286 (M+); IR (KBr) 932 cm-1 (Cd
Se). Anal. Calcd for C5H2S2Se2: C, 21.14; H, 0.71. Found:
C, 21.15; H, 0.72.
∆
2,2′-Biselen olo[2,3-d ]-1,3-d ith iole (DS-TTF ). A solution
of 9 (294 mg, 1.0 mmol) and trimethyl phosphite (0.4 mL) in
benzene (6 mL) was refluxed for 1 h. After concentration, the
residue was purified by column chromatography on silica gel
with CS2 and subsequent recrystallization from toluene to give
90 mg (42%) of DS-TTF as golden yellow leaflets: mp 237-
(17) Cornelissen, J . P.; Haasnoot, J . G.; Reedijk, J .; Faulmann, C.;
Legros, J .-P.; Cassoux, P.; Nigrey, P. J . Inorg. Chim. Acta 1992, 202,
131-139.
(18) Pan, W.-H.; Fackler, J . P., J r. In Inorganic Syntheses; Fackler,
J . P., J r., Ed.; J ohn Wiley & Sons: New York, 1982; Vol. 21, p 6-11.

TTF- and TSF-Type Electron Donors
J . Org. Chem., Vol. 63, No. 24, 1998 8871
237.5 °C with dec; 1H NMR (CS2/CDCl3) δ 7.00 (d, J ) 5.7 Hz,
2H) and 7.86 (d, J ) 5.7 Hz, 2H); MS m/z 412 (M+). Anal.
Calcd for C10H4S4Se2: C, 29.27; H, 0.98. Found: C, 29.29; H,
0.96.
4-Meth ylselen o-5-[2-(tetr a h yd r op yr a n -2-yloxy)eth yl]-
1,3-d iselen ole-2-selon e (15). To a mixture of 1 (1.57 mL,
10 mmol) and TMEDA (3.0 mL, 20 mmol) in THF (80 mL)
cooled to -70 °C was added a hexane solution of n-BuLi (1.54
M, 6.5 mL), and the solution was stirred at the same temper-
ature for 30 min. Selenium (790 mg, 10 mmol) was added in
one portion, and the reaction mixture was warmed to 0 °C over
a period of 2 h and stirred for additional 2 h. Then the mixture
was cooled again to -90 °C, and selenium powder (790 mg,
10 mmol) was added. To the mixture was slowly added a THF
(20 mL) solution of carbon diselenide (0.64 mL, 10 mmol) over
a period of 1 h, while the temperature was maintained around
-70 °C, and then the mixture was warmed to 0 °C over a
period of 1 h. The mixture was quenched by MeI (0.70 mL,
11 mmol) and stirred for an additional 1 h. After water (50
mL) was added, the mixture was extracted with CH2Cl2, and
the extract was washed with water and brine, dried (Na2SO4),
and concentrated. The residue was subjected to column
chromatography on silica gel with CH2Cl2 to afford 3.47 g (70%)
of 15 as a red oil: 1H NMR (CDCl3) δ 1.5-1.9 (m, 6H), 2.34 (s,
3H), 3.15 (m, 1H), 3.27 (m, 1H), 3.50 (m, 2H), 3.80 (m, 1H),
3.92 (m, 1H), and 4.63 (br t, J ) 3.4 Hz, 1H); 13C NMR (CDCl3)-
δ 11.9, 19.1, 25.2, 30.3, 34.8, 62.1, 65.9, 98.8, 129.1, 157.5, and
212.8; MS m/z 496 (M+); IR (neat) 903 cm-1 (CdSe). Anal.
Calcd for C11H16O2Se4: C, 26.63; H, 3.25. Found: C, 26.58;
H, 3.24.
4,4′(5′)-Bis(m eth ylselen o)-5,5′(4′)-bis[2-(tetr a h yd r op y-
r a n -2-yloxy)eth yl]tetr a selen a fu lva len e (17). A solution of
15 (1.5 g, 3.0 mmol) and trimethyl phosphite (1.1 mL, 9 mmol)
in benzene (14 mL) was refluxed for 2 h. After evaporation of
the solvent, the residue was purified by column chromatog-
raphy on silica gel with CH2Cl2 to give 1.18 g (93%) of 17 as a
red oil: 1H NMR (CDCl3) δ 1.5-1.9 (m, 12H), 2.252 (isomer
2.255) (s, 6H), 2.95 (m, 4H), 3.48 (m, 4H), 3.85 (m, 4H), and
4.63 (br t, J ) 3.4 Hz, 2H); 13C NMR (CDCl3) δ 10.9 (isomer
11.0), 19.2, 25.4, 30.5, 35.0, 62.0, 66.3, 98.6 (isomer 98.8), 114.1
(isomer 114.3), and 140.3 (isomer 140.4); MS m/z 836 (M+).
Anal. Calcd for C22H32Se6O4: C, 31.67; H, 3.87. Found: C,
31.80; H, 3.87.
Alternatively, the coupling reaction of 8 in trimethyl phos-
phite under reflux for 2 h gave DS-TTF in 13% yield.
4-Meth ylth io-5-[2-(tetr a h yd r op yr a n -2-yloxy)eth yl]-1,3-
d ith iole-2-th ion e (10). To a solution of 1 (6.28 mL, 40 mmol)
and TMEDA (6.04 mL, 40 mmol) in THF (150 mL) was added
a solution of n-BuLi in hexane (1.61 M, 26.1 mL) at -70 °C,
and the solution was stirred at the same temperature for 30
min. After addition of sulfur (1.28 g, 40 mmol), the mixture
was warmed to 0 °C over a period of 1 h and stirred for 2 h.
Into the solution, again cooled to -85 °C, were successively
added carbon disulfide (2.53 mL, 42 mmol) and methyl
thiocyanate (4.1 mL, 60 mmol). The reaction mixture was
warmed to 0 °C over a period of 2 h and stirred for 1 h. After
being quenched with water (100 mL), the mixture was
extracted with CH2Cl2, and the extract was washed with brine
and dried (MgSO4). After concentration, chromatography of
the residue on silica gel with CH2Cl2 gave 9.55 g (77%) of 10
as a yellow oil. An analytical sample was obtained by further
purification with preparative GPC using CHCl3 as eluent: 1H
NMR (CDCl3) δ 1.5-1.9 (m, 6H), 2.40 (s, 3H), 3.07 (m, 2H),
3.52(m, 1H), 3.79 (m, 1H), 3.91 (m, 1H), and 4.63 (br t, J )
3.4 Hz, 1H); 13C NMR (CDCl3) δ 19.2, 20.5, 25.3, 30.3, 30.6,
62.1, 65.7, 98.8, 131.7, 146.6, and 212.6; MS m/z 308 (M+); IR
(neat) 1065 cm-1 (CdS). Anal. Calcd for C11H16O2S4: C, 42.83;
H, 5.23. Found: C, 42.96; H, 5.29.
4-(2-H yd r oxye t h yl)-5-m e t h ylt h io-1,3-d it h iole -2-t h i-
on e (11). Compound 11 was obtained as a yellow solid in 99%
yield from 10 by the same procedure as described for the
1
preparation of 4: mp 33-33.5 °C; H NMR (CDCl3) δ 1.72 (s,
1H), 2.44 (s, 3H), 3.03 (t, J ) 6.1 Hz, 2H), and 3.84 (t, J ) 6.1
Hz, 2H); 13C NMR (CDCl3) δ 20.5, 32.9, 61.6, 132.3, 145.8, and
212.2; MS m/z 224 (M+); IR (neat) 3400 (OH) and 1061 cm-1
(CdS). Anal. Calcd for C6H8OS4: C, 32.12; H, 3.59. Found:
C, 32.10; H, 3.54.
4-Me t h ylt h io-5-(2-t osyloxye t h yl)-1,3-d it h iole -2-t h i-
on e (12). The tosylation of 11 to 12 was accomplished in 80%
yield by the same procedure as described for the preparation
of 5: yellow needles from hexane/CHCl3; mp 61-62 °C; 1H
NMR (CDCl3) δ 2.40 (s, 3H), 2.45 (s, 3H), 3.08 (t, J ) 6.0 Hz,
2H), 4.16 (t, J ) 6.0 Hz, 2H), 7.37 (d, J ) 8.2 Hz, 2H), and
7.73 (d, J ) 8.2 Hz, 2H); 13C NMR (CDCl3) δ 20.2, 21.6, 29.0,
67.8, 127.7, 129.9, 131.9, 133.6, 142.3, 145.4, and 210.7; MS
m/z 378 (M+); IR (neat) 1071 cm-1 (CdS). Anal. Calcd for
4,4′(5′)-Bis(2-h yd r oxyeth yl)-5,5′(4′)-bis(m eth ylselen o)-
tetr a selen a fu lva len e (18). A mixture of 17 (382 mg, 0.46
mmol), 2 N hydrochloric acid (0.2 mL), methanol (6 mL), and
THF (10 mL) was stirred at rt for 12 h. Water (12 mL) was
introduced, and then the mixture was extracted with CH2Cl2.
The extract was washed with brine, dried (MgSO4), and then
concentrated. The residue was washed with a small amount
of CH2Cl2 to give 288 mg (94%) of 18 as a reddish brown
1
C
13H14O3S5: C, 41.25; H, 3.75. Found: C, 41.29; H, 3.72.
solid: mp 110-112 °C; H NMR (CDCl3) δ 2.24 (s, 6H), 2.86
5,6-Dih ydr oth ien o[2,3-d]-1,3-dith iole-2-th ion e (13). Com-
(t, J ) 5.9 Hz, 4H), and 3.75 (t, J ) 5.9 Hz, 4H); MS m/z 668
(M+); IR (KBr) 3300 cm-1 (OH). Anal. Calcd for C12H16O2-
Se6: C, 21.64; H, 2.42. Found: C, 21.55; H, 2.37.
pound 12 was converted in 64% yield to 13 by the same
procedure as described for the preparation of 7, except that
the mixture was heated at 120 °C for 2 h: yellow needles from
hexane/CHCl3; mp 116-117 °C (lit.3 mp 110-111 °C); 1H NMR
(CDCl3) δ 3.09 (t, J ) 7.7 Hz, 2H) and 3.75 (t, J ) 7.7 Hz, 2H);
MS m/z 192 (M+).
Th ien o[2,3-d ]-1,3-d ith iole-2-th ion e (14). Conversion of
13 to 14 was carried out in 60% yield by the same procedure
as described for the preparation of 8: red needles from hexane/
CHCl3; mp 130.5-131 °C (lit.3 mp 125-125.5 °C); 1H NMR
(CDCl3) δ 7.09 (d, J ) 5.4 Hz, 1H) and 7.67 (d, J ) 5.4 Hz,
1H); MS m/z 190 (M+).
4,4′(5′)-Bis(m eth ylselen o)-5,5′(4′)-bis[2-(tosyloxy)eth yl]-
tetr a selen a fu lva len e (19). To a solution of 18 (890 mg, 1.34
mmol) in pyridine (9 mL) was added tosyl chloride (1.53 g, 8.04
mmol) at 0 °C. After being stirred for 12 h, the resulting
mixture was poured into ice-containing 1 N HCl solution (5
mL). The precipitate was collected by filtration and washed
with a small amount of MeOH to give 1.24 g (95%) of 19 as a
light red solid: mp 155 °C dec; 1H NMR (CDCl3) δ 2.21 (s,
6H), 2.43 (s, 6H), 2.93 (t, J ) 6.2 Hz, 4H), 4.09 (t, J ) 6.2 Hz,
4H), 7.29 (d, J ) 8.3 Hz, 4H), and 7.75 (d, J ) 8.3 Hz, 4H).
Anal. Calcd for C26H28O6S2Se6: C, 32.05; H, 2.90. Found: C,
32.07; H, 2.95.
5,5′,6,6′-Tetr ah ydr o-∆2,2′-bith ien o[2,3-d]-1,3-th iole (BET-
TTF ). Compound 13 was coupled with trimethyl phosphite
to BET-TTF in a manner similar to that described for BES-
TTF (17% yield): reddish orange crystals from toluene; mp
196-197 °C with dec (lit.3 trans mp 195-196 °C, cis mp 184-
186 °C; lit.4a mp 191-193 °C dec); 1H NMR (CS2/CDCl3) δ 2.826
(isomer 2.833) (t, J ) 8.1 Hz, 4H) and 3.72 (t, J ) 8.1 Hz, 4H);
MS m/z 320 (M+).
5,5′,6,6′-Te t r a h yd r o-∆2,2′-b ise le n olo[2,3-d ]-1,3-se le -
n ole (BES-TSF ). A mixture of 19 (1.24 g, 1.27 mmol) and
NaI (762 mg, 5.08 mmol) in DMF (25 mL) was stirred at 80
°C for 0.5 h. The reaction mixture was poured into water (50
mL), and the precipitate was collected by filtration, washed
with small amount of MeOH, and dried in vacuo. The brown
solid was recrystallized from PhCl to give 295 mg (39%) of
BES-TSF as a mixture of two kinds of crystals. For the trans
∆
2,2′-Bith ien o[2,3-d ]-1,3-th iole (DT-TTF ). Compound 14
was coupled with trimethyl phosphite to DT-TTF in a similar
manner as described for BES-TTF (22% yield): golden orange
leaflets from toluene; mp 228-229 °C (lit.3 mp 214-215 °C;
lit.4a mp 213-214 °C dec); 1H NMR (CS2/CDCl3) δ 6.85 (d, J )
5.1 Hz, 2H) and 7.28 (d, J ) 5.1 Hz, 2H); MS m/z 316 (M+).
1
isomer: reddish orange plates; mp 205-207 °C with dec; H
NMR (CS2/CDCl3) δ 2.88 (t, J ) 7.8 Hz, 4H) and 3.69 (t, J )
7.8 Hz, 4H); MS m/z 604 (M+). For the cis isomer: dark red
needles; mp 199-201 °C dec; 1H NMR (CS2-CDCl3) δ 2.87 (t,

8872 J . Org. Chem., Vol. 63, No. 24, 1998
J igami et al.
J ) 7.8 Hz, 4H) and 3.69 (t, J ) 7.8 Hz, 4H); MS m/z 604
(M+). Anal. Calcd for C10H8Se6: C, 19.95; H, 1.34. Found:
C, 20.13; H, 1.20.
Com p lexa tion . The TCNQ complexes of BES-TTF and DS-
TTF were prepared by a conventional diffusion method using
acetonitrile as solvent, while that of BES-TSF was obtained
by gradual growth of the crystals from an interface between a
carbon disulfide solution of the donor and an acetonitrile
solution of the acceptor. All the radical cation salts were
tometer or a Rigaku AFC7R diffractometer with graphite-
monochromated Cu KR radiation (λ ) 1.5418 Å) or Mo KR
radiation (λ ) 0.7107 Å), respectively. The intensity data were
measured using the ω-2θ scan technique. The structures
were solved by direct methods or Patterson methods and
refined by full-matrix least-squares techniques with anisotro-
pic temperature factors for the non-hydrogen atoms.
Ack n ow led gm en t. This work was partially sup-
ported by a Grant-in-Aid for Scientific Research from
the Ministry of Education, Science, Sports and Culture
of J apan.
prepared by electrocrystallization under galvanostatic condi-
tions (0.5-1.0 µA) in the presence of n-Bu4N+X- (X- ) ClO4
,
-
PF6-, and AsF6-) as the supporting electrolyte. The most
suitable solvent was chlorobenzene containing about 5%
ethanol.
X-r a y Cr ysta llogr a p h ic An a lyses.19 X-ray diffraction
experiments were performed at rt on a Rigaku AFC6S diffrac-
Su p p or tin g In for m a tion Ava ila ble: X-ray data for trans
BES-TSF, (BES-TTF)2‚AsF6, DS-TTF‚TCNQ, and BES-TSF‚
TCNQ (9 pages). This material is contained in libraries on
microfiche, immediately follows this article in the microfilm
version of the journal, and can be ordered from the ACS; see
any current masthead page for ordering information.
(19) Fully refined data for these structures have been deposited at
the Cambridge Crystallographic Data Centre. The data can be
obtained, on request, from the Director, Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge, CB2 1EZ, U.K.
J O981024F