Synthesis and properties of novel heterocycle-fused TTF-type electron donors: Bis(propylenethio)tetrathiafulvalene (BPT-TTF), bis(propyleneseleno)tetrathiafulvalene (BPS-TTF), and their tetraselenafulvalene analogues (BPT-TSF and BPS-TSF)

Article abstract of DOI:10.1039/b009700o

A series of novel heterocycle-fused TTF-type electron donors, bis(propylenethio)tetrathiafulvalene (BPT-TTF, 5), bis(propyleneseleno)tetrathiafulvalene (BPS-TTF, 6), and their tetraselenafulvalene analogues (BPT-TSF, 7 and BPS-TSF, 8) have been effectivel

Full text of DOI:10.1039/b009700o

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Synthesis and properties of novel heterocycle-fused TTF-type
electron donors: bis(propylenethio)tetrathiafulvalene (BPT-TTF),
bis(propyleneseleno)tetrathiafulvalene (BPS-TTF), and their
tetraselenafulvalene analogues (BPT-TSF and BPS-TSF){
Tetsuya Jigami, Mie Kodani, Satoshi Murakami, Kazuo Takimiya,* Yoshio Aso and
Tetsuo Otsubo*
Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Higashi-
Hiroshima 739-8527, Japan. Tel: z81-824-24-7734; Fax: z81-824-22-7191;
E-mail: ktakimi@hiroshima-u.ac.jp
Received 4th December 2000, Accepted 8th February 2001
First published as an Advance Article on the web 5th March 2001
A series of novel heterocycle-fused TTF-type electron donors, bis(propylenethio)tetrathiafulvalene (BPT-TTF,
5), bis(propyleneseleno)tetrathiafulvalene (BPS-TTF, 6), and their tetraselenafulvalene analogues (BPT-TSF, 7
and BPS-TSF, 8) have been effectively synthesized from a common starting compound, THP-protected pent-4-
yn-1-ol. The solution electrochemistry reveals that all the new donors have good electron donating properties.
Formation of their radical cation salts by electrocrystallization technique has been successfully achieved. All the
radical salts derived from the TTF derivatives (5 and 6) are insulating owing to the complete charge transfer.
On the other hand, the TSF derivatives (7 and 8) afford different types of highly conductive radical cation
salts. Of these, 7?PF6, 7?AsF6 and 7?FeCl4 remain metallic down to liquid helium temperature.
designated as a-, b-, h-, k-types, and so on. The planar
Introduction
molecular structures of 3 and 4 unlike non-planar BEDT-TTF
are considered to favor simple p-stacking suitable for a
columnar structure. With these results in mind, we have
designed a new family of six-membered heterocycle fused-TTF
type donors, namely bis(propylenethio)tetrathiafulvalene
(BPT-TTF, 5), bis(propyleneseleno)tetrathiafulvalene (BPS-
TTF, 6), and their tetraselenafulvalene analogues (BPT-TSF, 7
and BPS-TSF, 8). These donors might have flexible outer six-
membered rings like BEDT-TTF, and accordingly form radical
cation salts with versatile crystal structures. In addition, it
should be noted that intermolecular interactions among the
donors can be more or less tuned, i.e., decreased by installing
only one chalcogen atom in the six-membered ring, but
increased by introducing selenium in place of sulfur. In this
paper the synthesis and properties of these new TTF-type
donors (5–8) as well as the conductive properties and solid state
structures of their radical cation salts are described.
Most of the organic superconductors so far reported are radical
cation salts of bis(ethylenedithio)tetrathiafulvalene (BEDT-
TTF, 1) and related heterocycle-fused TTF type electron
donors.1 The fused outer heterocycles in these donors play a
very important role in intermolecular interactions through
heteroatomic contacts and accordingly in the solid state
properties of the derived radical cation salts. In the search
for new electron donors to produce highly conducting and
superconducting radical cation salts, potential approaches are
to modify the BEDT-TTF framework by (i) changing the
number of heteroatoms or ring size of the outer heterocycles
and (ii) replacing the sulfur atoms of the inner and outer
heterocycles with more polarizable selenium atoms.2 By a
combination of these two guidelines, one may design a wide
variety of heterocycle-fused TTF and tetraselenafulvalene
(TSF) derivatives, some of which have already been investi-
gated and found to behave as superior electron donors.1,3,4
Bis(ethylenethio)tetrathiafulvalene (BET-TTF, 2)5 possessing
five-membered sulfur heterocycles, is such a heterocycle-fused
TTF derivative developed early on, and recently Rovira and
coworkers reported that it can produce a wide variety of
metallic radical cation salts.5 Our group also synthesized the
selenium analogues of 2, bis(ethyleneseleno)tetrathiafulvalene
(BES-TTF, 3) and bis(ethyleneseleno)tetraselenafulvalene
(BES-TSF, 4) and found that they can form similar conducting
radical cation salts but with increasing metallic stability at low
temperature due to the introduction of the selenium atoms.6
The X-ray structural analyses revealed that the radical cation
salts of 3 and 4 possess a columnar structure of donor stacks
similar to the quasi one-dimensional Bechgaard salts.1 This
feature is in sharp contrast to the quasi two-dimensional salts
of BEDT-TTF, which appear in various crystal phases
Results and discussion
Syntheses of novel electron donors
For the synthesis of the title compounds, we examined a
synthetic route similar to that used for BES-TTF 3 and BES-
TSF 4, as shown in Scheme 1.6 This synthetic route involves
two important steps: (1) one-pot formation of the 1,3-
dichalcogenole ring7 from tetrahydropyranyl (THP)-protected
pent-4-yn-1-ol8 and (2) intramolecular transalkylation on a
sulfur or selenium atom toward the construction of the outer
six-membered heterocycle. The advantage of this method is
that an appropriate combination of the sulfur and selenium
reagents in the initial formation of 1,3-dichalcogenole ring
permits a common access to all the target donors from the same
starting material. Thus, BPT-TTF 5 and BPS-TTF 6 were
obtained as follows; the acetylene 9 was treated successively
with nBuLi, sulfur and carbon disulfide to generate the vinyl
anion intermediate 10, which was then quenched by methyl
{Electronic supplementary information (ESI) available: further
experimental
b009700o/
details.
See
http://www.rsc.org/suppdata/jm/b0/
1026
J. Mater. Chem., 2001, 11, 1026–1033
This journal is # The Royal Society of Chemistry 2001
DOI: 10.1039/b009700o

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thiocyanate or by a combined reagent of selenium and methyl
iodide to afford THP-protected 4-(hydroxypropyl)-5-methyl-
chalcogeno-1,3-dithiole-2-thiones 11 (X~S, 69% yield; X~Se,
83% yield). After deprotection of the THP group (79–90%
yield) followed by tosylation under general conditions (77–80%
yield), the resulting tosylates 13 were treated with sodium
iodide in DMF to afford 14 (X~S, 92% yield; X~Se, 98%
yield). It is reasonable to consider that this heterocyclization
reaction proceeds via intramolecular transalkylation on the
chalcogen atom. The transalkylation on sulfur required a
higher reaction temperature (120 ‡C, 3 h), whereas that on the
selenium proceeded under somewhat milder conditions (80 ‡C,
2 h). The conventional transformation of 14 into the ketones 15
with mercury acetate and subsequent trimethyl phosphite-
promoted coupling reaction gave BPT-TTF (5) and BPS-TTF
(6) in 52% and 30% yields (two steps), respectively.
For the syntheses of TSF derivatives, BPT-TSF (7) and BPS-
TSF (8), we noticed that it is inexpedient to pursue similar
chemical conversions forming the outer six-membered hetero-
cycle on the relatively unstable 1,3-diselenole-2-selone stage,6
and accordingly a slightly modified route was taken as shown
in Scheme 2. Thus the 1,3-diselenole-2-selones 16 were similarly
prepared from 9 using a combination of selenium and carbon
diselenide instead of sulfur and carbon disulfide, and directly
converted into the TSF derivatives 17, which were then
subjected to conversion reactions to give 7 and 8 in moderate
yields.
Scheme 1 Synthesis of BPT-TTF 5 and BPS-TTF 6. Reagents: i, nBuLi,
TMEDA, THF; ii, S, CS2; iii, MeSCN (for 11 (X~S)) or Se then MeI
(for 11 (X~Se)); iv, HCl aq. MeOH–acetone; v, TsCl, pyridine; vi, NaI,
DMF; vii, Hg(OAc)2, CHCl3; viii, P(OMe)3.
between the first and second oxidation potentials, DE values, of
5–8 are almost same as those of TTF and TSF.
The present donors are expected to exist as a mixture of cis-
and trans-isomers concerning the central double bond as
observed for 2–4.5,6 Unlike the cases of BES-TTF (3) and BES-
TSF (4), 1H NMR spectra of 5–8 did not give any helpful
information on the existence of the isomers owing to multiplet
signals for the outer heterocyclic protons. Alternatively, 13C
NMR of readily soluble 5 and 6 showed the three pairs of peaks
assignable to the quaternary carbons of the TTF core
supporting the existence of cis- and trans-isomers as expected
(see Experimental section). The approximately similar height of
each peak in the pairs indicates that the ratio of the cis- and
trans-isomers is roughly 1 : 1.
Electrochemistry
Table 1 summarizes the oxidation potentials of 5–8 determined
by cyclic voltammetry, together with those of the parent
donors, TTF and TSF. All these new donors show two
reversible one-electron redox waves, indicating the sequential
formation of radical cation and dication species. The first
oxidation potentials of 5–8 are positively shifted by 10–40 mV
with respect to their parent compounds, regardless of the
chalcogen type in the outer ring. In addition, the differences
Scheme 2 Synthesis of BPT-TSF 7 and BPS-TSF 8. Reagents: i, nBuLi,
TMEDA, THF; ii, Se, CSe2; iii, MeSCN (for 16 X~S) or Se then MeI
(for 16 X~Se); iv, P(OMe)3, benzene; v, HCl aq. MeOH–THF; vi,
TsCl, NEt3, CH2Cl2; vii, NaI, DMF.
J. Mater. Chem., 2001, 11, 1026–1033
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Table 1 Half-wave oxidation potentialsa of 5–8 and related donors
Donor
E11/2/V
E21/2/V
DE/V
5
6
7
8
TTF
TSF
0.38
0.37
0.53
0.50
0.34
0.49
0.76
0.75
0.83
0.80
0.71
0.78
0.38
0.38
0.30
0.30
0.37
0.29
avs. Ag/AgCl electrode, in PhCN containing 0.1 M nBu4NClO4 as
supporting electrolyte. Pt working and counter electrodes, scan rate
100 mV s21, 23 ‡C.
Radical cation salts
A standard procedure for electrocrystallization was applied to
the present new donors, and the obtained radical cation salts
are very versatile in composition ratio and conductive
behavior, as shown in Table 2. All the salts produced from
TTF derivatives 5 and 6 have conductivities lower than
1025 S cm21 at room temperature. This is rationalized in terms
of their 1 : 1 composition ratios of donor to anion: since each
donor species is in a monocationic state, they are Mott-type
insulators.
In contrast, the TSF derivatives 7 and 8 afforded conductive
radical cation salts; those of 7 took either 2 : 1 or 3 : 2
Table 2 Radical cation salts of BPT-TTF (5), BPS-TTF (6), BPT-TSF
(7) and BPS-TSF (8)
Salt
Appearance
D : Aa srt/S cm21c Remarks
5?PF6
5?AsF6 Black prisms
6?PF6
Dark blue needles 1 : 1b
v1025 d
v1025 d
v1025 d
v1025 d
v1025 d
50
38
150
2.0
98
—
—
—
—
1 : 1b
Dark blue needles 1 : 1b
6?AsF6 Dark blue needles 1 : 1b
6?SbF6 Dark blue needles 1 : 1b
—
7?BF4
7?PF6
Black plates
Black prisms
3 : 2b
2 : 1
2 : 1
3 : 2
2 : 1
3 : 2
3 : 2
3 : 2
3 : 2
M down to 200 K
M down to 4.2 K
M down to 4.2 K
M down to 200 K
M down to 4.2 K
7?AsF6 Black prisms
7?SbF6 Black prisms
7?FeCl4 Black plates
8?BF4
8?ClO4 Black prisms
8?PF6 Black prisms
8?AsF6 Black prisms
Black prisms
0.5
1.0
3.0
5.0
E
E
E
E
act~0.027 eV
act~0.027 eV
act~0.030 eV
act~0.017 eV
aDetermined by X-ray crystallographic analysis unless otherwise
c
stated. bDetermined on the basis of elemental analysis. Measured on
a single crystal with a four-probe method unless otherwise stated.
dMeasured on a single crystal with a two-probe method.
Fig. 2 Crystal structure of 7?AsF6: (a) a-axis projection, (b) stacking
arrangement viewed from the molecular long axis.
stoichiometry, while those of 8 only 3 : 2 stoichiometry. The
room temperature conductivities of three 2 : 1 salts of 7, 7?PF6,
7?AsF6 and 7?FeCl4 are very high (38–150 S cm21), and they
are metallic down to liquid helium temperature. The con-
ductivities of 7?PF6 and 7?AsF6 monotonously increase with
lowering temperature, and the maximum values at liquid
helium temperature are about twenty times higher than those at
room temperature. Fig. 1 demonstrates the temperature-
dependent resistivity of 7?PF6 as a representative.
The crystal structure of 7?AsF6, elucidated by X-ray
crystallographic analysis, is shown in Fig. 2.9 The donor
molecules form dimeric pairs, which stack in a columnar
manner, resembling b-type BEDT-TTF (1) salts.1 The inter-
˚
planar distance within the pair is 3.71 A, and that between the
Fig. 1 Temperature dependence of resistivity of radical cation salts
derived from 7 and 8.
˚
pairs is 4.03 A. There are many side-by-side interactions
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Fig. 3 Crystal structure of 7?FeCl4: viewed along the a-axis (left) and the b-axis without anions (right).
between the adjacent stacks through short Se–Se and S–Se
contacts, which can enhance the conductivity and stabilize the
metallic state down to low temperature.
also Fig. 1 for 7?BF4). The X-ray crystallographic analysis of
7?BF4 with a high room temperature conductivity of 50 S cm21
indicated that it belongs to a monoclinic system, but failed in
the final refinement of the structure solution because of
insufficient data due to serious decay of the crystal during data
collection.10 On the other hand, it turned out that the crystal
structure of less conductive 7?SbF6 belongs to a triclinic system,
which was completely analyzed to be isostructural with 3 : 2
salts of 8 as described below.
All the radical cation salts of 8 have 3 : 2 stoichiometry and
are moderately conductive (0.5–5.0 S cm21) at room tempera-
ture with semiconductive behavior as represented by 8?PF6
shown in Fig. 1. The crystal structures of 8?PF6 and 8?AsF6 are
isostructural with the above 7?SbF6.11 As a representative of
this type, the structure of 8?AsF6 is shown in Fig. 4. It contains
two crystallographically independent donor molecules, one of
which takes the cis form and the other the trans form. The cis
isomers make face-to-face stacked dimers, which are piled up to
construct a columnar structure. In the dimer unit, there are
The temperature dependence of the conductivity of 7?FeCl4
is not so large as that of 7?PF6 and 7?AsF6, and its maximum
conductivity around 20 K is about double that at room
temperature (see also Fig. 1). This different behavior is ascribed
to the different crystal structure of 7?FeCl4, which comprises a
so-called k-type arrangement of the donor, as shown in Fig. 3.
The two 3 : 2 salts of 7 are metallic with a broad maximum of
conductivity at a relatively high temperature around 200 K (see
˚
short Se–Se contacts (3.60–3.64 A), but the shortest Se–Se
˚
distance between the neighboring dimers is 4.12 A, thus
indicating alternate interplanar interactions along the
column. The trans isomer, in contrast, orthogonally exists
between the stacking columns of the cis isomer. The
neighboring trans donors interact with each other in an edge-
˚
to-edge manner through short Se–Se contacts (3.80–3.89 A),
consequently forming a ribbon-like array. In addition there are
˚
many face-to-edge Se–Se interactions (3.70–3.90 A) between
the cis isomer and the trans isomer, forming a two-dimensional
Se–Se contact network.12 On comparison of the molecular
˚
structures, the central double bond of the cis isomer (1.38 A) is
˚
longer than that of the trans isomer (1.31 A), suggesting a
higher oxidation state of the cis isomer than of the trans isomer.
Taking account of this, the 3 : 2 stoichiometry is elucidated by
possibly assigning a monocationic state for the cis isomer and a
neutral state for the trans isomer. This means that the main
conduction path occurs through a two-dimensional Se–Se
contact network interaction between the cis isomer and the
trans isomer. Such electric conduction over donors with
different valence states must suffer a high barrier, being
responsible for the semiconductive or weakly metallic behavior
of this type of salts.13
Conclusion
Bis(propylenethio)- and bis(propyleneseleno)-substituted TTF
and TSF (5–8) have been effectively synthesized from readily
available common THP-protected pent-4-yn-1-ol. Electroche-
mical study showed that they all have moderate electron
donating abilities. However, contrary to our initial expectation,
no conductive radical cation salts were obtained from the TTF
derivatives 5 and 6. In contrast, the TSF derivatives 7 and 8
gave conductive radical cation salts that were versatile in
Fig. 4 Crystal structure of 8?AsF6: (a) projected along the cis-8 stacks,
(b) packing diagram of donor arrays viewed from the molecular long
axis of cis-8.
J. Mater. Chem., 2001, 11, 1026–1033
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composition ratio and conductive behavior. In particular, all
the salts of 7 were metallic at room temperature but
demonstrate different temperature dependence of the con-
ductivities depending on their crystal structures and stoichio-
metry.
4-(3-Hydroxypropyl)-5-methylthio-1,3-dithiole-2-thione (12
(X~S))
A mixture of 11 (X~S) (1.61 g, 5.0 mmol), hydrochloric acid
(1 M, 3 mL), methanol (50 mL), and acetone (50 mL) was
stirred at rt for 12 h. The mixture was diluted with water
(100 mL) and then extracted with dichloromethane (30 mL).
The extract was washed with brine, dried (MgSO4), and then
concentrated. The residue was purified by column chromato-
graphy (silica gel, eluent: dichloromethane–AcOEt, 9 : 1 v/v) to
give 4 as a yellow oil (1.07 g, 90%). Further purification with
preparative GPC gave an analytical sample.
Experimental
General
Melting points are uncorrected. Nuclear magnetic resonance
spectra were obtained in the indicated deuterated solvent with a
JEOL Lambda 400 spectrometer operating at 400 MHz for 1H
and 100 MHz for 13C with TMS as internal reference; chemical
shifts (d) are reported in parts per million. Mass spectral data
were obtained on a Shimadzu QP-2000 spectrometer using an
electron impact ionization procedure (70 eV). The molecular
ion peaks of the selenium-containing compounds showed a
typical selenium isotopic pattern, and all the selenium-
containing mass peaks are reported for 80Se. Infrared spectra
were obtained on a Shimadzu FTIR-8100A spectrometer.
Cyclic voltammetry was carried out on a Hokuto Denko HA-
301 potentiostat equipped with a Hokuto Denko HB-104
function generator. 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. All
reactions were carried out under a nitrogen atmosphere with
dry solvents. Column chromatography was carried out with
Daisogel IR-60 (63–210 mm). Preparative gel permeation
chromatography (GPC) was performed on Japan Analytical
Industry Co., Ltd. LC-908 equipped with a JAI-GEL 1H, 2H
column assembly. Selenium powder (red)14 and carbon
diselenide15 were synthesized according to the literature
procedures. All the new compounds were fully characterized
by the spectroscopic and elemental analyses, and most of the
characterization data are available as Electronic Supplemen-
tary Information.{
4-(3-Hydroxypropyl)-5-methylseleno-1,3-dithiole-2-thione (12
(X~Se))
12 (X~Se) was synthesized from 11 (X~Se) in the same
manner as 12 (X~S). Yellow oil (79% yield).
4-Methylthio-5-(3-tosyloxypropyl)-1,3-dithiole-2-thione (13
(X~S))
To a solution of 12 (X~S) (1.99 g, 7.0 mmol) in pyridine
(17.5 mL) was added tosyl chloride (26.7 g, 14.0 mmol) at
0 ‡C. After being stirred for 6 h, the mixture was poured into
ice-containing 1 M hydrochloric acid (50 mL). The mixture was
extracted with dichloromethane (50 mL63), and the extract
was washed successively with 1 M hydrochloric acid
(100 mL62) and brine (100 mL) and dried (MgSO4). The
concentrated extract was purified by column chromatography
on silica gel eluting with dichloromethane followed by
recrystallization from hexane–chloroform and gave 13
(X~S) as yellow fine needles (2.53 g, 77%).
4-Methylseleno-5-(3-tosyloxypropyl)-1,3-dithiole-2-thione (13
(X~Se))
13 (X~Se) was synthesized from 12 (X~Se) in the same
manner as 13 (X~S). Yellow oil (80% yield).
6,7-Dihydro-5H-thiino[2,3-d]-1,3-dithiole-2-thione (14 (X~S))
A mixture of 13 (X~S) (1.46 g, 3.72 mmol) and sodium iodide
(1.12 g, 7.44 mmol) in DMF (16 mL) was heated at 120 ‡C for
3 h. The mixture was then diluted with water (16 mL) and
extracted with carbon disulfide (50 mL63), and the extract was
successively washed with water (50 mL) and brine (50 mL) and
finally dried (MgSO4). Column chromatography of the
concentrated extract on silica gel eluted with carbon disulfide
gave 14 (X~S) as yellow micro crystals (710 mg, 92%). An
analytical sample was obtained by recrystallization from
hexane–carbon disulfide as yellow needles.
4-Methylthio-5-[3-(tetrahydropyran-2-yloxy)propyl]-1,3-
dithiole-2-thione (11 (X~S))
To a solution of 2-(pent-4-yn-1-yloxy)tetrahydro-2H-pyran 9
(2.52 g, 15 mmol) and TMEDA (4.5 mL, 30 mmol) in THF
(120 mL) was added a solution of nBuLi in hexane (1.60 M,
10.5 mL) at 270 ‡C, and the solution was stirred at the same
temperature for 30 min. After addition of sulfur (480 mg,
15 mmol), the mixture was warmed to 0 ‡C over a period of 1 h
and stirred for 2 h at that temperature. The solution was again
cooled to 290 ‡C, and then carbon disulfide (1.8 mL, 30 mmol)
and methyl thiocyanate (3.1 mL, 37.5 mmol) were added. The
resulting mixture was allowed to warm to 0 ‡C over a period of
1 h, then diluted with water (50 mL), and extracted with
dichloromethane (30 mL63). The extract was washed with
water and saturated NaCl aqueous solution, dried (MgSO4),
and concentrated. The residue was purified with column
chromatography on silica gel eluted with dichloromethane to
afford practically pure 11 (X~S) as a yellow oil (Rf 0.5, 3.32 g,
69%). An analytical sample was obtained by further purifica-
tion by preparative GPC.
6,7-Dihydro-5H-selenino[2,3-d]-1,3-dithiole-2-thione (14
(X~Se))
14 (X~Se) was synthesized from 13 (X~Se) in the same
manner as 14 (X~S). Yellow needles from chloroform–hexane
(98% yield).
6,7-Dihydro-5H-thiino[2,3-d]-1,3-dithiol-2-one (15 (X~S))
A mixture of 14 (X~S) (160 mg, 0.79 mmol) and mercury
acetate (630 mg, 1.98 mmol) in chloroform (8 mL) was stirred
for 8 h at room temperature. The resulting white solid was
filtered off and washed with chloroform (10 mL63), and the
combined filtrate was washed with saturated sodium bicarbo-
nate solution (10 mL63) and dried (MgSO4). The concen-
trated organic layer was subjected to column chromatography
on silica gel eluted with dichloromethane to give practically
pure 15 (X~S) (150 mg, 99%). Recrystallization from carbon
disulfide–hexane gave analytically pure 15 (X~S) as colorless
needles.
4-Methylseleno-5-[3-(tetrahydropyran-2-yloxy)propyl]-1,3-
dithiole-2-thione (11 (X~Se))
11 (X~Se) was synthesized in the same manner as 11 (X~S)
using a combined reagent of selenium powder and methyl
iodide instead of methyl thiocyanate as the final quenching
reagent. Yellow oil (83% yield).
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6,7-Dihydro-5H-selenino[2,3-d]-1,3-dithiol-2-one (15 (X~Se))
4,4’(5’)-Bis(methylseleno)-5,5’(4’)-bis[3-(tetrahydropyran-2-
yloxy)propyl]tetraselenafulvalene (17 (X~Se))
Colorless needles from carbon disulfide–hexane (87% yield).
17 (X~Se) was synthesized from 16 (X~Se) in the same
manner as 17 (X~S). Red oil (98% yield).
Bis(propylenethio)tetrathiafulvalene (BPT-TTF, 6,6’,7,7’-
tetrahydro-5H,5’H-D2,2’-bi(thiino[2,3-d]-1,3-dithiole), 5)
4,4’(5’)-Bis(3-hydroxypropyl)-5,5’(4’)-
bis(methylthio)tetraselenafulvalene (18 (X~S))
A solution of 15 (X~S) (700 mg, 3.69 mmol) in trimethyl
phosphite (15 mL) was heated under reflux for 20 h. After
concentration, the residue was purified by column chromato-
graphy on silica gel eluted with carbon disulfide followed by
recrystallization from benzene–hexane to give 5 as red needles
(340 mg, 53%): mp 204–206 ‡C; 1H NMR (CDCl3) d 2.13–2.19
(m, 4H, CH2), 2.37 (t, J~6.3 Hz, 4H, CH2), 2.97–3.00 (m, 2H,
CH2); 13C NMR (CDCl3) d 23.38, 24.96, 28.36, 108.65 and
108.73, 116.36 and 116.44, 118.04 and 118.12; MS m/z 348
(Mz). Anal. Calcd for C12H12S6: C, 41.35; H, 3.47%. Found:
C, 41.36; H, 3.43%.
A mixture of 17 (X~S) (2.14 g, 2.78 mmol), hydrochloric acid
(1.0 M, 1.4 mL), methanol (42 mL), THF (35 mL) and water
(50 mL) was stirred at rt for 12 h. The mixture was extracted
with dichloromethane (20 mL63), and the extract was washed
with brine and dried (MgSO4). Evaporation of the solvent gave
practically pure 18 (X~S) as a red oil (1.44 g, 86%), which was
used for the next reaction without further purification. The
analytically pure sample was obtained by further purification
with preparative GPC.
4,4’(5’)-Bis(3-hydroxypropyl)-5,5’(4’)-
bis(methylseleno)tetraselenafulvalene (18 (X~Se))
Bis(propyleneseleno)tetrathiafulvalene (BPS-TTF, 6,6’,7,7’-
tetrahydro-5H,5’H-D2,2’-bi(selenino[2,3-d]-1,3-dithiole), 6)
18 (X~Se) was synthesized from 17 (X~Se) in the same
manner as 18 (X~S). Red powder (95% yield).
Red needles from benzene–hexane (34% yield): mp 190–191 ‡C;
1H NMR (CDCl3) d 2.22–2.28 (m, 2H, CH2), 2.37–2.40 (m, 2H,
CH2), 3.07–3.10 (m, 2H, CH2); 13C NMR d 21.42, 24.12, 26.26,
105.49 and 105.56, 109.65 and 109.69, 119.84 and 119.91; MS
m/z 444 (Mz). Anal. Calcd for C12H12S4Se2: C, 32.58; H,
2.73%. Found: C, 32.45; H, 2.69%.
4,4’(5’)-Bis(methylthio)-5,5’(4’)-bis[3-
(tosyloxy)propyl]tetraselenafulvalene (19 (X~S))
To a solution of 18 (X~S) (360 mg, 0.6 mmol) and triethyl-
amine (0.24 mL, 1.8 mmol) in dichloromethane (6 mL) was
added tosyl chloride (336 mg, 1.8 mmol) at 0 ‡C. The mixture
was stirred for 12 h, then quenched by addition of water
(3.0 mL) and extracted with dichloromethane (10 mL63). The
extract was washed with saturated NaCl aqueous solution and
dried (MgSO4). Evaporation of the solvent gave 19 (X~S) as a
red solid (323 mg, 59%). An analytically pure sample was
obtained by the reprecipitation technique: the crude 19 (X~S)
was dissolved in dichloromethane (5 mL), and the solution was
filtered through filter paper, whereupon hexane (15 mL) was
added to the solution to precipitate a microcrystalline solid of
pure 19 (X~S).
4-Methylthio-5-[3-(tetrahydropyran-2-yloxy)propyl]-1,3-
diselenole-2-selone (16 (X~S))
To a mixture of 9 (2.52 g, 15 mmol) and TMEDA (4.5 mL,
30 mmol) in THF (120 mL) cooled to 270 ‡C was added a
hexane solution of nBuLi (1.61 M, 10.2 mL, 16.4 mmol), and
the solution was stirred for 30 min to form the lithium acetylide
species. Red selenium powder (987 mg, 12.5 mmol) was added
in one portion, and the reaction mixture was warmed to 0 ‡C
over a period of 1 h and stirred for an additional 1 h. The
mixture was cooled again to 290 ‡C, and then carbon
diselenide (0.8 mL, 12.5 mmol) and methyl thiocyanate
(3.09 mL, 37.5 mmol) were added. The resulting mixture was
allowed to warm to 0 ‡C over a period of 1 h and then diluted
with water (50 mL), extracted with dichloromethane
(30 mL63). The extract was washed with water (50 mL) and
saturated NaCl aqueous solution (50 mL), dried (MgSO4), and
concentrated. The residue was purified with column chroma-
tography on silica gel with dichloromethane to afford 16
(X~S) as a red oil (Rf 0.5, 4.89 g, 70%).
4,4’(5’)-Bis(methylseleno)-5,5’(4’)-bis[3-
(tosyloxy)propyl]tetraselenafulvalene (19 (X~Se))
19 (X~Se) was synthesized from 18 (X~Se) in the same
manner as 19 (X~S). Red microcrystalline solid (64% yield).
Bis(propylenethio)tetraselenafulvalene (BPT-TSF, 6,6’,7,7’-
tetrahydro-5H,5’H-D2,2’-bi(thiino[2,3-d]-1,3-selenole), 7)
A mixture of 19 (X~S) (1.23 g, 1.35 mmol) and sodium iodide
(605 mg, 4.05 mmol) in DMF (13 mL) was stirred at 80 ‡C for
12 h. The reaction mixture was poured into water (50 mL), and
the resulting precipitate was collected by filtration and dried in
vacuo. Column chromatography on silica gel eluting with
carbon disulfide gave 7 as a green powder. Recrystallization
from hexane–carbon disulfide afforded analytically pure 7 as
red plates (430 mg, 60%). mp 181–182 ‡C (melt with decom-
position); 1H NMR (CDCl3) d 2.14–2.20 (m, 4H, CH2) 2.46 (t,
J~ 6.0 Hz, 4H, CH2) 3.02–3.05 (m, 4H, CH2); MS m/z 540
(Mz). Anal. Calcd for C12H12S2Se4: C, 26.88; H, 2.26%.
Found: C, 26.82; H, 2.26%.
4-Methylseleno-5-[3-(tetrahydropyran-2-yloxy)propyl]-1,3-
diselenole-2-selone (16 (X~Se))
16 (X~Se) was synthesized in the same manner as 16 (X~S)
using a combined reagent of selenium powder and methyl
iodide instead of methyl thiocyanate as the final quenching
reagent. Red oil (76% yield).
4,4’(5’)-Bis(methylthio)-5,5’(4’)-bis[3-(tetrahydropyran-2-
yloxy)propyl]tetraselenafulvalene (17 (X~S))
Bis(propyleneseleno)tetraselenafulvalene (BPS-TSF, 6,6’,7,7’-
tetrahydro-5H,5’H-D2,2’-bi(selenino[2,3-d]-1,3-selenole), 8)
Trimethyl phosphite (2.6 mL, 16.6 mmol) was added to a
solution of 16 (X~S) (2.57 g, 5.5 mmol) in benzene (30 mL),
and the mixture was refluxed for 2 h. Evaporation of the
solvent and the excess phosphite gave an oily residue, which
was purified by column chromatography on silica gel with
dichloromethane as an eluent to give 17 (X~S) as a red oil (Rf
0.4, 1.92 g, 90%).
8 was synthesized from 19 (X~Se) in a similar manner as 7: the
reaction was complete within 1 h at 80 ‡C. Red plates from
hexane–carbon disulfide (30% yield): mp 191–192 ‡C (melt with
1
decomposition); H NMR (CDCl3) d 2.22–2.28 (m, 4H, CH2)
2.43–2.46 (m, 4H, CH2) 3.09–3.12 (m, 4H, CH2); MS m/z 636
J. Mater. Chem., 2001, 11, 1026–1033
1031

View Article Online
Table 4 Refined probability for atoms in outer six-membered rings
Atom
72?AsF6
72?FeCl4
83?(AsF6)2
S(Se)6/C9
S(Se)15/C18
S(Se)24/C24
0.82
0.63
—
0.63
0.81
—
0.89
0.87
0.94
Fig. 5 Numbering scheme of 5–8 for structure analyses.
(Mz); Anal. Calcd for C12H12Se6: C, 22.88; H, 1.92%. Found:
C, 22.87; H, 1.94%.
analysis followed by additional cycles of least-squares calcula-
tion under the constraints of eqn. (1):
.
Oc(C)~3:667{2:667 Oc(S)
Typical electrocrystallization procedure
.
Oc(C)~6:667{5:667 Oc(Se)
Into a 20 mL H-shaped glass cell with a fine frit dividing the
anolyte and catholyte compartments equipped with platinum
wire electrodes were placed 15 mL of chlorobenzene or THF
and 3 mL of ethanol containing the appropriate tetrabutyl-
where Oc(X)~occupancy of the given atom in parenthesis.
Then the probability of atoms are calculated according to
eqn. (2):
ammonium salt (nBu4NzX2, X2~BF4
, ClO4 , PF6 ,
2
2
2
AsF62and SbF62) or tetraethylammonium salt (Et4NzX2,
X2~FeCl42) (50–150 mg). The donor (ca. 5 mg) was added
into the anode compartment. The solution was degassed by
passing a dry nitrogen stream and electrolyzed under a
constant current of 1–4 mA at 23 ‡C. Black crystals of radical
cation salts gradually grew on the anode electrode within
several days. The crystals were collected by filtration, washed
with cold dichloromethane, and dried in vacuo. The obtained
crystals were utilized for the conductivity measurements and X-
ray crystallographic analyses. The ratios of donor to anion
were determined by the results of crystallographic analyses,
except for the following radical cation salts, of which ratios
were determined on the basis of combustion microanalysis.
.
(C)~(16{6 Oc(C))=10
P
P
P
.
(S)~(16 Oc(S){6)=10
.
(Se)~(34 Oc(Se){6)=10
where P(X)~probability of the given atom in parenthesis.
The results for each structural analysis are summarized in
Tables 3 and 4.
CCDC 154224–154226. See http://www.rsc.org/suppdata/jm/
b0/b009700o/ for crystallographic files in .cif format.
Acknowledgement
This work was partially supported by Grants-in-Aid for
Scientific Research from the Ministry of Education, Science,
Sports and Culture of Japan. We thank the Cryogenic Center,
Hiroshima University for supplying cryogen (liquid helium).
X-Ray crystallographic analyses
X-ray diffraction experiments were performed at room
temperature on a Rigaku AFC6S diffractometer with gra-
˚
phite-monochromated Cu Ka radiation (l ~1.5418 A) or a
Rigaku AFC7R diffractometer with Mo Ka radiation
˚
(l~0.7107 A). The intensity data were measured using the
References
1
For comprehensive reviews on organic superconductors, see:
J. M. Williams, J. R. Ferraro, R. J. Thorn, K. D. Carlson,
U. Geiser, H. H. Wang, A. M. Kini and M.-H. Whangbo, Organic
Superconductors (Including Fullerenes): Synthesis, Structure,
Properties, and Theory, Prentice Hall, Englewood Cliffs, New
Jersey, 1992; T. Ishiguro, K. Yamaji and G. Saito, Organic
Superconductors, 2nd edn., Springer–Verlag, Berlin, 1998.
For reviews on the synthesis of TTF derivatives, see: G. Schukat,
A. M. Richter and E. Fangha¨nel, Sulfur Rep., 1987, 7, 155;
G. Schukat and E. Fangha¨nel, Sulfur Rep., 1993, 14, 245;
G. Schukat and E. Fangha¨nel, Sulfur Rep., 1996, 18, 1.
D. J. Lagouvardos and G. C. Papavassiliou, Z. Naturforsch., 1992,
47b, 898; T. Naito, H. Kobayashi and A. Kobayashi, Bull. Chem.
Soc. Jpn., 1997, 70, 107; S. Golhen, L. Ouahab, A. Lebeuze,
M. Bouayed, P. Delhaes, Y. Kashimura, R. Kato, L. Binet and J.-
M. Fabre, J. Mater. Chem., 1999, 9, 387; J. Yamada, H. Nishikawa
and K. Kikuchi, J. Mater. Chem., 1999, 9, 617.
v–2h scan technique. The structures were solved by direct
methods or Patterson methods. Hydrogen atoms were located
by calculation and not refined. All non-hydrogen atoms were
refined by full-matrix least-squares techniques with anisotropic
temperature factors. All the radical cation salt crystals
potentially contain the cis and trans isomers of donors or
disordering at S(Se)6–C9, S(Se)15–C18 and S(Se)24–C27 in the
outer six-membered rings (see numbering scheme, Fig. 5). The
initial positions of the carbon and sulfur (selenium) atoms were
determined as usual, and the occupancy of each atom was
refined by full-matrix least-squares techniques with population
2
3
Table 3 Crystal data for radical cation salts of 7 and 8
72?AsF6
72?FeCl4
83?(AsF6)2
4
A. Kobayashi, T. Udagawa, H. Tomita, T. Naito and
H. Kobayashi, Chem. Lett., 1993, 2179; H. Kobayashi,
H. Tomita, T. Naito, A. Kobayashi, F. Sakai, T. Watanabe and
P. Cassoux, J. Am. Chem. Soc., 1996, 118, 368; H. Kobayashi,
T. Naito, A. Sato, K. Kawano, A. Kobayashi, H. Tanaka, T. Saito,
M. Tokumoto and P. Cassoux, Mol. Cryst. Liq. Cryst., 1996, 284,
61; H. Tanaka, A. Kobayashi, A. Sato, H. Akutsu and
H. Kobayashi, J. Am. Chem. Soc., 1999, 121, 760; E. Ojima,
H. Fujiwara, K. Kato and H. Kobayashi, J. Am. Chem. Soc., 1999,
121, 5581; H. Kobayashi, A. Kobayashi and P. Cassoux, Chem.
Soc. Rev., 2000, 29, 325.
Chemical formula
C24H24S4- C24H24
-
C36H36Se18
As2F12
2267.79
-
Se8AsF6
1261.29
Triclinic
7.891(6)
16.406(5)
6.629(3)
96.09(3)
100.43(5)
87.10(5)
838.8(8)
296(1)
S4Se8FeCl4
1270.03
Orthorhombic Triclinic
11.733(5)
35.43(1)
8.606(5)
—
—
—
Formula weight
Crystal system
˚
a/A
10.793(4)
15.769(5)
8.312(3)
93.85(3)
109.43(2)
88.04(3)
1331.0(8)
296(1)
˚
b/A
˚
c/A
a/‡
b/‡
c/‡
3
˚
V/A
3577(2)
296(1)
5
E. M. Engler, V. V. Patel, J. R. Andersen, R. R. Schumaker and
A. A. Fukushima, J. Am. Chem. Soc., 1978, 100, 3769; C. Rovira,
J. Veciana, N. Santalo´, J. Tarre´s, J. Cirujeda, E. Molins, J. Llorca
and E. Espinosa, J. Org. Chem., 1994, 59, 3307; J. Tarre´s,
N. Santalo´, M. Mas, E. Molins, J. Veciana, C. Rovira, S. Yang,
H. Lee and D. O. Cowan, Chem. Mater., 1995, 7, 1558;
M. C. Rovira, J. J. Novoa, J. Tarre´s, C. Rovira, J. Veciana,
S. Yang, D. O. Cowan and E. Canadell, Adv. Mater., 1995, 7,
1023; C. Rovira, J. Veciana, J. Tarre´s, E. Molins, M. Mas,
D. O. Cowan and S. Yang, Synth. Met., 1995, 70, 883;
T/K
Space group
Z
¯
¯
P1 (no. 2) Pnma (no. 62) P1 (no. 2)
1
4
1
m/cm21
99.95
(Mo Ka)
91.17
(Mo Ka)
2463
136.38
(Mo Ka)
3928
Number of data (I¢3.0s(I)) 2892
Ra, Rw
0.028, 0.024 0.064, 0.050 0.040, 0.041
2
b
aR~S(|Fo|2|Fc|)/S|Fo|. Rw~{Sw(|Fo|2|Fc|) /Sw|Fo| }2.
b
2
1
1032
J. Mater. Chem., 2001, 11, 1026–1033

View Article Online
E. Coronado, L. R. Falvello, J. R. Gala´n-Mascaro´s, C. Gime´nez-
Saiz, C. J. Go´mez-Garc´ıa, V. N. Lauhkin, A. Pe´rez-Ben´ıtez,
C. Rovira and J. Veciana, Adv. Mater., 1997, 9, 984; E. Ribera,
C. Rovira, J. Veciana, V. N. Laukhin, E. Canadell, J. Vidal–
Gancedo and E. Molins, Synth. Met., 1997, 86, 1993; C. Rovira,
J. Tarre´s, E. Ribera, J. Veciana, E. Canadell, E. Molins, M. Mas,
V. Laukhin, M.-L. Doublet, D. O. Cowan and S. Yang, Synth.
Met., 1997, 86, 2145; A. Pe´rez-Ben´ıtez, C. Rovira, J. Veciana,
J. Vidal-Gancedo, V. N. Laukhin, L. V. Zorina, S. S. Khasanov,
B. Z. Narymbetov and R. P. Shibaeva, Synth. Met., 1999, 102,
1707; E. Laukhina, E. Ribera, J. Vidal-Gancedo, S. Khasanov,
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S. Nam, J. Singleton, J. Veciana and C. Rovira, Adv. Mater., 2000,
12, 54.
with 73?(SbF6)2, 83?(PF6)2and 83?(AsF6)2. Crystal data for
M~2080.04,
73?(SbF6)2:
a~10.730(6),
C36H36S6Se12Sb2F12,
c~8.162(4) A,
triclinic,
a~92.69(5),
˚
b~16.150(9),
3
˚
¯
b~109.82(4), c~88.65(6)‡, V~1329(1) A , space group P1
(no. 2), Z~1, R~0.078, Rw~0.054. 83?(PF6)2: C36H36Se18P2F12,
M~2179.89, triclinic, a~10.80(2), b~15.63(3), c~8.33(1) A,
˚
3
˚
a~94.0(1), b~109.4(1), c~88.2(2)‡, V~1322(4) A , space
¯
group P1 (no. 2), Z~1. 83?(BF4)2: C36H36Se18B2F8,
˚
M~2063.58, triclinic, a~10.72(1), b~15.24(7), c~8.27(1) A,
3
˚
a~94.6(2), b~108.88(9), c~87.4(2)‡, V~1274(7) A , space
¯
group P1 (no. 2), Z~1. 83?(ClO4)2: C36H36Se18Cl2O8,
M~2088.87, triclinic, a~10.686 (6), b~15.274 (7), c~8.262
˚
3
˚
(3) A, a~94.29 (3), b~108.95 (3), c~87.60 (4)‡, V~1271 (1) A ,
¯
T~296(1) K, space group P1 (no. 2), Z~1.
6
T. Jigami, K. Takimiya, Y. Aso and T. Otsubo, Chem. Lett., 1997,
1091; T. Jigami, K. Takimiya, T. Otsubo and Y. Aso, J. Org.
Chem., 1998, 63, 8865; T. Jigami, K. Takimiya, Y. Aso and
T. Otsubo, Synth. Met., 1999, 102, 1714.
K. Takimiya, A. Morikami and T. Otsubo, Synlett, 1997, 319.
L. Crombie and A. G. Jacklin, J. Chem. Soc., 1957, 1622.
In 7?AsF6, the main isomer is trans, but orientational disordering
of the outer six-membered rings was observed; the probability of
sulfur atoms for the trans form are approximately 80% for one ring
and 60% for the other. For the details, see Experimental section.
The crystal data of 7?PF6 indicate that the salt is isostructural with
7?AsF6. Crystal data for 72?PF6: C24H24S4Se8PF6, M~1217.34,
12 Similar packing arrangements have been reported: R. Kato,
A. Kobayashi, Y. Sakaki and H. Kobayashi, Chem. Lett., 1984,
993; M. A. Beno, U. Geiser, A. M. Kini, H. H. Wang,
K. D. Caarlson, M. M. Miller, T. J. Allen, J. A. Schlueter,
R. B. Proksch and J. M. Williams, Synth. Met., 1988, 27, A209.
13 Generally the bond lengths on the TTF core in TTF-based radical
cation salts can be a good probe to evaluate the oxidation stage of
the given TTF derivatives. In the present cases, unfortunately the
standard deviation of the carbon–carbon bond lengths are
relatively large due to the existence of many heavy selenium
atoms, and it is very difficult to estimate the exact valences of 8
based on the bond lengths from the structural analysis..
14 J. P. Cornelissen, J. G. Haasnoot, J. Reedijk, C. Faulmann, J.-
P. Legros, P. Cassoux and P. J. Nigrey, Inorg. Chim. Acta, 1992,
202, 131.
7
8
9
˚
triclinic, a~7.9230(8), b~16.264(3), c~6.6524(8) A, a~96.03(1),
˚
3
¯
b~100.489(9), c~87.51(1)‡, V~838.0(2) A , space group P1 (no.
2), Z~1, R~0.043, Rw~0.043.
10 Crystal data for 73?(BF4)2: C36H36S12Se6B2F8, M~2063.58,
15 W.-H. Pan and J. P. Fackler Jr., in Inorganic Syntheses, Vol. 21,
ed. J. P. Fackler Jr., John Wiley & Sons, New York, 1982, pp. 6–
11; F. Ogura and K. Takimiya, in Organoselenium Chemistry; A
Practical Approach, ed. T. G. Back, Oxford University Press, New
York, 1999, pp. 258–260.
˚
monoclinic, a~31.628(2), b~10.358(2), c~15.369(2) A,
˚
b
3
~92.549 (9)‡, V~5030(1) A , space group C2/c (no. 15), Z~4.
11 The final refinements of 83 (BF4)2 and 83?(ClO4)2 were not carried
out since their cell parameters indicated that they are isostructural
J. Mater. Chem., 2001, 11, 1026–1033
1033