Syntheses of new electron donors with hydroxymethyl groups and studies on their cation-radical salts

Article abstract of DOI:10.1039/b003041o

New electron donors 4,5-ethylenedithio-4',5'-(1-hydroxypropane-2,3-diyldithio)tetrathiafulvalene (1a), 4,5-bis(methylthio)-4',5'-(1-hydroxypropane-2,3-diyldithio)tetrathiafulvalene (1b), 4,5-ethylenedithio-4',5'-(1,4-dihydroxybutane-2,3-diyldithio)tetrathiafulvale ne (1c) and 4,5-bis(methylthio)-4',5'-(1,4-dihydroxybutane-2,3-diyldithio)tetrathiafulval ene (1d) with hydroxymethyl groups were synthesized and characterized spectroscopically. Their redox potentials were determined using cyclic voltammetry. Crystals of cation-radical salts based on these new electron donors, (1a)₂·ClO₄, (1c)₂·Cl, (1c)₂·I, were obtained by standard electrochemical methods. The crystal structure of (1c)₂·Cl was determined and studied. Electrical measurements of the cation-radical salts indicated that they displayed semiconducting behaviors, however, with good conductivities at room temperature: 0.68 S cm^-1 for (1a)₂·ClO₄ and 0.10 S cm^-1 for (1c)₂·Cl.

Full text of DOI:10.1039/b003041o

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J O U R N A L O F
Syntheses of new electron donors with hydroxymethyl groups and
studies on their cation-radical salts
Hongxiang Li,a Deqing Zhang,*a Bin Zhang,a Youxin Yao,a Wei Xu,a Daoben Zhu*a and
Zhemin Wangb
C H E M I S T R Y
aOrganic Solids Laboratory, Center for Molecular Sciences, Institute of Chemistry, Chinese
Academy of Sciences, Beijing, 100080, China. E-mail: dqzhang@infoc3.icas.ac.cn
bDepartment of Chemistry, Peking University, Beijing 100875, China
Received 17th April 2000, Accepted 27th June 2000
Published on the Web 3rd August 2000
New electron donors 4,5-ethylenedithio-4',5'-(1-hydroxypropane-2,3-diyldithio)tetrathiafulvalene (1a), 4,5-
bis(methylthio)-4',5'-(1-hydroxypropane-2,3-diyldithio)tetrathiafulvalene (1b), 4,5-ethylenedithio-4',5'-(1,4-
dihydroxybutane-2,3-diyldithio)tetrathiafulvalene (1c) and 4,5-bis(methylthio)-4',5'-(1,4-dihydroxybutane-2,3-
diyldithio)tetrathiafulvalene (1d) with hydroxymethyl groups were synthesized and characterized
spectroscopically. Their redox potentials were determined using cyclic voltammetry. Crystals of cation-radical
salts based on these new electron donors, (1a)2?ClO4, (1c)2?Cl, (1c)2?I, were obtained by standard
electrochemical methods. The crystal structure of (1c)2?Cl was determined and studied. Electrical measurements
of the cation-radical salts indicated that they displayed semiconducting behaviors, however, with good
conductivities at room temperature: 0.68 S cm21 for (1a)2?ClO4 and 0.10 S cm21 for (1c)2?Cl.
4,5-ethylenedithio-1,3-dithiole-2-thione.9 Efforts were also
made to synthesize 3a and b by the nucleophilic substitution
reaction between 1,3-dithiole-2-thione-4,5-dithiolate (DMIT)
Introduction
Since the discovery of organic metals in 1973 and super-
conductors in 1980, great progress has been achieved1 in the
®eld of organic conductors and superconductors. To date,
more than one hundred organic conductors and forty organic
superconductors have been discovered.2 As far as the super-
conducting transition temperature is concerned, apart from the
superconductors derived from C60, the organic superconductor
based on the cation-radical salt of BEDT-TTF [bis(ethylene-
dithio)tetrathiafulvalene] still holds the record.2c Various
chemical modi®cations of BEDT-TTF have been made.
These include the substitution of peripheral sulfur atoms
with selenium (BETS)3 [bis(ethylenediseleno)tetrathiafulva-
lene] and with oxygen (BEDO)4 [bis(ethylenedioxy)tetrathia-
fulvalene] atoms as well as extra-substitution with hydroxy,
amide, or pyridine groups.5 In fact, several organic super-
conductors based on modi®ed BEDT-TTF have been dis-
covered.6 Recently, we have paid great attention to new
electron donors with hydroxy groups since the intermolecular
interactions between electron donor and acceptor molecules or
counter anions may be enhanced by the formation of
intermolecular hydrogen-bonds. We have reported the synth-
esis of an electron donor with four hydroxy groups and related
investigations previously.7 In this paper, we will describe the
synthesis and physical studies on four new electron donors with
hydroxy groups and their cation-radical salts.
Results and discussion
Synthesis
The synthesis of new electron donors 1a±d started from
trithione oligomer (C3S5)x 2 (see Scheme 1) which was prepared
by the oxidation of bis(tetrabutylammonium) bis[2-thioxo-1,3-
dithiole-4,5-bis(thiolato)]zincate with iodine.8 Compounds 3a
and b were synthesized by [4z2] cycloaddition between allyl
alcohol and but-2-ene-1,4-diol, respectively, with trithione
oligomer, which decomposed to give the unstable 4,5-dihydro-
1,3-dithiole-2,4,5-trithione monomer on heating. A similar
strategy was employed for the preparation of alkyl substituted
Scheme 1
DOI: 10.1039/b003041o
J. Mater. Chem., 2000, 10, 2063±2067
This journal is # The Royal Society of Chemistry 2000
2063

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anion and the corresponding dibromoalkyl alcohols, but there
were no target compounds in the reaction mixture as indicated
by analysis of thin layer chromatography and the mass
spectrum.
The trialkyl phosphite mediated coupling of 1,3-dithiole-2-
thiones is standard chemistry in the construction of TTF
derivatives. However, direct coupling of compounds 3a±d
failed probably because of the side-reaction between the
hydroxy groups and trialkyl phosphite, although triisopropyl
phosphite instead of triethyl phosphite was used to hinder such
a side-reaction. Thus, 3a and b were converted to 4a and b to
protect the hydroxy groups with tert-butyldiphenylchlorosi-
lane. Oxidation of 4a and b with Hg(OAc)2 gave 5a and b in
high yield. The cross coupling reaction between 5a and b and
the corresponding 1,3-dithiole-2-thiones afforded compounds
6a±d in moderate yield. Deprotection of 6a±d, using tetra-
butylammonium ¯uoride in CH2Cl2, afforded target molecules
1a±d in analytically pure form after isolation by column
chromatography on silica gel. Since the target molecules 1a±d
were easily and quickly oxidized in the crude reaction mixture
under air, the deprotection step should be performed under a
nitrogen atmosphere and tetrabutylammonium ¯uoride should
not be used in large excess. The chemical structures of 1a±d
were con®rmed by spectroscopic data (1H-NMR, MS) and
elemental analysis.
Fig. 2 The energy-minimized conformation of 1c obtained with semi-
empirical quantum calculations: the two hydroxymethyl groups are in a
cis-con®guration.
The crystals of the cation-radical salts based on these new
electron donors 1a±d were grown using standard electroche-
mical techniques. Crystals of good quality from 1a with
Bun4N?ClO4, and from 1c with Bun4N?I3 and Bun4N?GaCl4
were obtained. Their chemical compositions were established
with elemental analysis and electron probe microscopy (EPM).
The cation-radical salt (1c)2?Cl, in which the counter anion was
Cl2, not GaCl42, was formed by oxidising 1c under constant
current with Me4N?GaCl4 as supporting electrolyte in CH2Cl2.
Similar phenomena with BEDT-TTF as electron donor were
described previously.10 Among them, the crystal structure of
(1c)2?Cl was determined.
Fig. 3 Asymmetric unit of (1c)2?Cl with atomic numbering scheme.
1c is shown in Fig. 2. The two hydroxymethyl groups are in a
cis-conformation, which is predicted by the Diels±Alder
reaction mechanism and corresponds well with the X-ray
diffraction analytical results for (1c)2?Cl (see below). Since
oxidation implies extraction of one electron from the HOMO,
the oxidation potentials of electron donors should be directly
related to their HOMO energies. The new donor molecules 1a±
d
and BEDT-TTF have similar HOMO energies (e.g.
28.092 eV for 1c; 28.032 eV for BEDT-TTF), so it can be
inferred that 1a±d should have similar electron-donating
abilities as BEDT-TTF, which is fully consistent with the
results of cyclic voltammetric measurements as discussed
above.
Electrochemistry and theoretical calculation
The redox behaviors of compounds 1a±d were investigated by
cyclic voltammetry. They all exhibited two quasi-reversible
redox waves. As an example, the cyclic voltammograms of 1c
with E11=2~0.48 V, E21=2~0.88 V was shown in Fig. 1. For
comparison, the corresponding redox potentials of BEDT-TTF
were also measured under the same conditions (E11=2~0.48 V,
E21=2~0.89 V). The experimental results indicated that com-
pounds 1a±d show similar electron-donating capabilities to
BEDT-TTF. It further indicated that the substituted hydroxy
groups of 1a±d have no signi®cant in¯uence on the electron-
donation properties and they all should be good precursors for
organic conductors.
Crystal structure of (1c)2?Cl{
The crystal of (1c)2?Cl (size: 0.33601460.02 mm3) for
structural analysis was obtained by electrochemical methods
(for details see Experimental section). The X-ray crystal-
lographic data are as follows. Formula: C24H24ClO4S16.
Formula weight: 924.84. Crystal system: triclinic. Space
Å
group: P1; a~8.9908(5) A, b~13.2399(5) A, c~15.0602(10)
Ê
Ê
Ê
A, a~81.003(4)³, b~85.747(3)³, c~70.911(3)³, V~
1672.79(16) A , Z~2, Dc~1.836 g cm23; F(000)~946. Re¯ec-
Ê 3
The molecular structures of these new electron donors were
also theoretically investigated with semi-empirical quantum
calculations (PM3 method implemented in MOPAC pro-
gram11). As an example, the energy-minimized conformation of
tions measured 23520; re¯ections unique 7929 (Rint~0.072);
re¯ections Iw2s(I) 6055; R~0.0825; Rw~0.2000.
The asymmetric unit contains two donor molecules A and B
as well as the chloride anion (see Fig. 3). Molecules A and B
show slight differences with regard to bond lengths and angles,
but all of them are still within the normal range as indicated in
Table 1 in which representative bond lengths and angles are
listed. The differences in bond lengths and angles between
molecule A and B indicate that these two molecules may carry
different charges. For these two molecules, the central TTF
plane plus the peripheral sulfur atoms: S5, S6, S7 and S8 for
molecule A; S13, S14, S15 and S16 for molecule B, are almost
coplanar. For molecule A, the molecule is folded along the
vector of S5±S6 and S7±S8 with angles of 13.03³ and 6.63³,
{CCDC reference number 1145/231. See http://www.rsc.org/suppdata/
jm/b0/b003041o for crystallographic ®les in .cif format.
Fig. 1 The cyclic voltammogram of compound 1c.
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Ê
Table 1 Selected bond lengths (A) and angles (³) of molecules A and B
in (1c)2?Cl
Table 2 The short atomic contacts for (1c)2?Cl in the crystal
S(1)±S(14)a
S(5)±S(14)a
S(6)±S(16)b
S(8)±S(15)
H(2)±Cl(1)
3.454(3)
3.578(3)
3.556(3)
3.544(3)
2.306(2)
S(4)±S(15)
S(1)±S(10)c
S(8)±S(10)b
S(8)±S(14)b
H(4)±Cl(1)
3.623(3)
3.571(3)
3.571(3)
3.571(3)
2.319(9)
A
B
S(1)±C(1)
S(1)±C(3)
S(3)±C(5)
S(3)±C(2)
S(5)±C(3)
S(5)±C(7)
S(7)±C(5)
S(7)±C(9)
C(1)±C(2)
C(3)±C(4)
C(5)±C(6)
C(7)±C(8)
C(9)±C(10)
C(1)±S(1)±C(3)
C(3)±S(5)±C(7)
S(1)±C(1)±S(2)
S(5)±C(3)±S(1)
1.745(8)
1.769(8)
1.751(8)
1.752(8)
1.761(8)
1.820(8)
1.745(8)
1.790(10)
1.333(11)
1.337(11)
1.359(11)
1.545(10)
1.479(12)
94.9(4)
S(9)±C(11)
S(9)±C(13)
S(11)±C(12)
S(11)±C(15)
S(13)±C(13)
S(13)±C(17)
S(15)±C(15)
S(15)±C(19)
C(11)±C(12)
C(13)±C(14)
C(15)±C(16)
C(17)±C(18)
C(19)±C(20)
C(11)±S(9)±C(13)
C(13)±S(13)±C(17)
S(9)±C(11)±S(10)
S(13)±C(13)±S(9)
1.723(8)
1.768(8)
1.723(8)
1.735(8)
1.738(8)
1.828(8)
1.742(8)
1.802(8)
1.374(10)
1.342(10)
1.384(11)
1.525(10)
1.501(12)
95.4(4)
Symmetry transformation used to generate equivalent atoms:
a21zx, 1zy, z. b22x, 12y, 2z. 12x, 12y, 2z.
c
also show semiconducting behaviors. The corresponding
conductivity at room temperature and activation energies
evaluated approximately by the plot of ln (R/Rrt) vs. 1/T (see
inset of Fig. 5) are summarized in Table 3.
By now, to the best of our knowledge, most of the cation-
radical salts based on electron donors containing hydroxy-
methyl groups exhibit semiconducting properties,5b,5e for
which there is still no clear interpretation. We will continue
our efforts to prepare CT salts of 1a±d with various
experimental conditions, hoping to ®nd new organic con-
ductors.
100.3(4)
114.3(4)
113.5(4)
100.2(4)
115.5(4)
114.2(4)
respectively. Similarly, for molecule B the central TTF plane
forms dihedral angles of 7.39³ and 8.48³ with the plane of S13,
C17, C18 and S14 and that of S15, C19, C20 and S16
respectively. The two hydroxymethyl groups of both molecules
A and B are in a cis-conformation.
In the crystal, molecules form columns along the a-axis (see
Fig. 4). Intermolecular interactions in the column are sig-
ni®cantly weak because of the larger intermolecular separation
Summary
Four new electron donors with hydroxy groups were
synthesized and characterized. They all show similar elec-
tron-donating capabilities as BEDT-TTF. Three cation-radical
salts: (1a)2?ClO4, (1c)2?Cl, (1a)2?I were obtained. The crystal
structure of (1c)2?Cl was determined by X-ray diffraction
analysis. Conductivity measurements indicated that they all
displayed semiconducting behavior. Preparation of other
cation-radical salts derived from these new electron donors
and corresponding structural and physical investigations are in
progress.
Ê
(y9 A). In the ab plane, molecules arrange in the sequence of
AA'BB'AA'¼ forming layers (see Fig. 4). Here, molecules A
and A' are related by an inversion center. This also holds true
for molecules B and B'. Such a molecular arrangement may
avoid the direct overlapping of hydroxymethyl groups, and
hence reduce the steric hindrance. Neighboring molecular
layers are separated by chloride anion columns. In each
molecular layer there are several short contacts between sulfur
atoms as listed in Table 2. Hydrogen-bonds are not found
between the hydroxy groups. Hydroxy groups, however, form
hydrogen-bonds with chloride anions as indicated also in
Table 2.
Experimental
General
Melting points were measured on an XT4-100X microscope
apparatus and are uncorrected. 1H-NMR: UNITY
200(Varian). Mass spectra: AEI-MS50 for EI-MS and
BEFLEX III for TOF-MS. Elemental analyses: Carlo-Erba-
1106 instrument. EPM: ETM810Q instrument. Cyclic voltam-
Electrical conductivity of cation-radical salts
The temperature dependence of electrical conductivity of the
cation-radical salts (1a)2?ClO4, (1c)2?Cl, (1c)2?I, was studied
with crystals by the conventional four-probe method.12 As an
example, the variation of resistance ratio (R/Rrt, where Rrt is
the resistance at 300 K) of (1c)2?Cl with temperature is
displayed in Fig. 5. With decreasing temperature, the resistance
increases gradually in the temperature range 290±180 K, and
below 180 K it increases signi®cantly, being characteristic of a
semiconductor. Similarly, the CT salts (1a)2?ClO4 and(1c)2?I
Fig. 5 Temperature dependence of electrical resistance for (1c)2?Cl.
Table 3 The room temperature conductivity and activation energies of
cation-radical salts (1a)2?ClO4, (1c)2?Cl and (1c)2?I
Conductivity (rt)/S cm21
Activating energy/eV
(1c)2?Cl
(1c)2?I
(1a)2?ClO4
0.10
0.0071
0.68
0.25
0.051
0.014
Fig. 4 Molecular packing pattern for (1c)2?Cl (ab plane).
J. Mater. Chem., 2000, 10, 2063±2067
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metric measurement: EGDG PAR 370 System, TBAPF6 as
electrolyte. Semi-empirical calculations were done with the
MOPAC program.
The X-ray diffraction data were collected on an Enraf-
Nonius Kappa CCD diffractometer using graphite-monochro-
freshly distilled triisopropyl phosphite (8 ml) and the mixture
was heated to 140 ³C under N2 and stirred at this temperature
for 5 h. After that, the reaction mixture was cooled down to
room temperature and distilled in vacuo to remove triisopropyl
phosphite. Column chromatography of the residue on silica gel
with petroleum ether (bp 60±90 ³C)±dichloromethane (5 : 1)
yielded compound 6a as a red oil (0.41 g, 30%). 1H-NMR
(CDCl3): d 7.63 (4H, m), 7.39 (6H, m), 3.85 (2H, m), 3.79 (1H,
m), 3.36 (2H, m), 3.20 (4H, t), 1.05 (9H, s); MS(TOF) 652
(Mz).
Ê
matized Mo-Ka radiation (l~0.71073 A) at 120 K. Absorption
correction was made for all re¯ections with 6.88³v2hv55.78³
via the Sortav procedure (Tmin~0.864, Tmax~0.990). Data
reduction was performed with the program HKLScale (Nonius
1995). Unit cell dimensions were re®ned with the program
Denzo (Nonius 1995). The crystal structure was solved by
direct methods (SHELXS-97), and re®ned by full-matrix-least
squares method on F2. Anisotropic thermal parameters were
employed for non-hydrogen atoms. The positions of hydrogen
atoms were calculated and re®ned with isotropic thermal
parameters at geometrically restrained positions.
Compounds 6b, 6c, 6d were prepared similarly
Compound 6b: red oil (yield: 32%). 1H-NMR (CDCl3): d
7.62 (4H, m), 7.38 (6H, m), 3.92 (2H, m), 3.78 (1H, m), 3.21
(2H, m), 2.40 (6H, s), 1.01 (9H, s); MS(TOF) 654 (Mz).
Compound 6c: red oil (yield: 40%). 1H-NMR (CDCl3): d
7.62 (8H, m), 7.38 (12H, m), 3.88 (4H, m), 3.80 (2H, m), 3.25
(4H, t), 0.99 (18H, s); MS(TOF) 920 (Mz). Anal.Calc. for
C44H48S8O2Si2: C, 57.39; H, 5.20; S, 27.62; Found C, 57.33; H,
5.01; S, 27.62%.
Compounds 3b, 4b, 5b were synthesized according to the
reported procedures.7
Compound 6d: red oil (yield: 30%). 1H-NMR (CDCl3): d
7.60 (8H, m), 7.32 (12H, m), 3.92 (4H, m), 3.79 (2H, m), 2.42
(6H, s), 1.00 (18H, s); MS(TOF) 922 (Mz).
4,5-(1-Hydroxypropane-2,3-diyldithio)-1,3-dithiole-2-thione (3a)
Compound 3a was prepared, according to the procedure
described by Neilands et al.13 by [4z2] cycloaddition of
oligo(1,3-dithiole-2,4,5-trithione) 2 (4.8 g) to allyl alcohol
(3.0 g, 51.7 mmol) in 1,4-dioxane and the mixture was stirred
at 80±85 ³C for 4 h. The reaction mixture was ®ltered and the
residue was washed twice with hot ethanol (50 ml). The
combined ®ltrate and washings were decolorized by use of
activated charcoal. After removing the solvent, column
chromatography of the crude reaction mixture on silica gel
with petroleum ether (bp 60±90 ³C)±ethyl acetate (4 : 1)
afforded compound 3a as a yellow powder (2.6 g, 42.0%),
mp 88±89 ³C; 1H-NMR (CDCl3): d 3.96 (2H, m), 3.89 (1H,
m), 3.40 (2H, m); MS(EI) 254 (Mz); Anal. Calc. for
C6H6OS5: C, 28.33; H, 2.38; S, 63.01; Found C, 28.59; H,
2.25; S, 63.25%.
4,5-Ethylenedithio-4',5'-(1-hydroxypropane-2,3-
diyldithio)tetrathiafulvalene (1a)
To a solution of 6a (1.0 g, 1.53 mmol) in THF (50 ml) was
added tetrabutylammonium ¯uoride trihydrate (0.72 g,
2.28 mmol) and the mixture was stirred at 25 ³C for 10 h
under N2. Then solvent was removed in vacuo to afford a
viscous oil. Column chromatography of the crude reaction
mixture on silica gel with CH2Cl2 yielded 1a as a dark red
1
powder (0.44 g, 70%), mp 160±161 ³C; H-NMR (CDCl3): d:
3.84 (2H, m), 3.78 (1H, m), 3.30 (2H, m), 3.28 (4H, t);
MS(TOF) 414 (Mz); Anal. Calc. for C11H10OS8: C, 31.88; H,
2.41; S, 61.84; Found C, 32.18; H, 2.53; S, 61.42%.
Compounds 1b, 1c and 1d were synthesized in a similar
manner.
4,5-(1-tert-Butyldiphenylsilyloxypropane-2,3-diyldithio)-1,3-
dithiole-2-thione (4a)
Compound 1b: red oil (yield: 65%). 1H-NMR (CDCl3): d
3.85 (2H, m), 3.80 (1H, m), 3.27 (2H, m), 2.43 (6H, s). High-
resolution MS(EI) for C11H12OS8, Found: 415.8643950; Calc:
415.8648254.
Compound 1c: red powder (yield: 60%), mp 196±197 ³C. 1H-
NMR (CDCl3): d 4.05 (4H, m), 3.93 (2H, m), 3.28 (4H, t);
MS(EI) 444 (Mz). Anal. Calc. for C12H12O2S8: C, 32.43; H,
2.70; S, 57.65; Found C, 32.33; H, 2.77; S, 57.44%.
Compound 1d: red powder (yield: 56%), mp 138±139 ³C. 1H-
NMR (CDCl3): d 3.95 (4H, m), 3.85 (2H, m), 2.42 (6H, s);
MS(TOF) 446(Mz). Anal. Calc. for C12H14O2S8: C, 32.29; H,
3.14; S. 57.40; Found C, 32.29; H, 3.20; S, 57.37%.
To a solution of compound 3a (0.25 g, 0.88 mmol) in dry DMF
(50 ml) was added sequentially tert-butyldiphenylchlorosilane
(0.6 g, 2.18 mmol) followed by imidazole (0.5 g, 7.35 mmol)
under N2, then the mixture was stirred at 20 ³C for 16 h. The
solvent was removed in vacuo and the residue was dissolved in
CH2Cl2. The organic phase was washed with water (3620 ml),
dried (MgSO4) and then the solvent was evaporated. Column
chromatography of the residue on silica gel with petroleum
ether (bp 60±90 ³C)±dichloromethane (3 : 1) afforded com-
pound 4a as a yellow powder (0.40 g, 93%), mp 112±114 ³C;
1H-NMR (CDCl3): d 7.65 (4H, m), 7.42 (6H, m), 3.88 (2H, m),
3.80 (1H, m), 3.39 (2H, m), 1.03 (9H, s); MS(TOF) 492 (Mz).
4,5-(1-tert-Butyldiphenylsilyloxypropane-2,3-diyldithio)-1,3-
dithiol-2-one (5a)
Preparation of cation-radical salts
Standard electrochemical techniques were employed for the
crystal growth of cation-radical salts. For example, (1c)2?Cl
was prepared as follows: 8.88 mg of compound 1c and
17.16 mg Me4N?GaCl4 were placed in an H-cell and dissolved
in 20 ml of dichloromethane. Constant current (1.0 mA) was
applied. Black needle single-crystals were obtained after two
weeks.
Salts (1a)2?ClO4 and (1c)2?I were obtained similarly.
The chemical compositions of (1a)2?ClO4 and (1c)2?I were
determined by elemental analysis and EPM respectively. EPS
data for (1c)2?I: element weight of S, 80.2; element number of S,
2.51; element weight of I, 18.5; element number of I, 0.15;
estimated composition, (1c)2?I; (1a)2?ClO4: Anal. Calc. for
C22H20S16O6Cl: C, 28.46; H, 2.16; S, 55.20; Cl, 3.83; Found C,
28.45; H, 2.07; S, 55.27; Cl, 4.18%.
To a solution of compound 4a (2.0 g, 4.06 mmol) in CH2Cl2±
HOAc (40 ml, 3 : 1 v/v), mercuric acetate (excess) was added
and the mixture was stirred at 20 ³C for 5 h. The white
precipitate was removed by ®ltration through Celite and the
®ltrate was washed with water and dried (MgSO4). The solvent
was removed to afford compound 5a as white powder (1.91 g,
99%), mp 61±63 ³C; H-NMR (CDCl3): d 7.59 (4H, m), 7.33
(6H, m), 3.80 (2H, m), 3.68 (1H, m), 3.21 (2H, m), 0.99 (9H, s);
MS(EI) 476 (Mz).
1
4,5-Ethylenedithio-4',5'-(1-tert-butyldiphenylsilyloxypropane-
2,3-diyldithio)tetrathiafulvalene (6a)
4,5-Ethylenedithio-1,3-dithiole-2-thione (0.8 g, 3.57 mmol) was
added to a solution of compound 5a (1.0 g, 2.10 mmol) in neat,
2066
J. Mater. Chem., 2000, 10, 2063±2067

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M. R. Bryce, J. N. Heaton, A. J. Moore, P. J. Skabara,
J. A. K. Howard, E. OrtÂõ, P. M. Viruela and R. Viruela,
J. Mater. Chem., 1995, 5, 1689; (e) J. M. Fabre, S. Chakroune,
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78, 89; (f) A. S. Batsanov, M. R. Bryce, G. Cooke, J. N. Heaton
and J. A. K. Howard, J. Chem. Soc. Chem. Commun., 1993, 1701;
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Acknowledgements
The present work was supported ®nancially by the Chinese
Academy of Sciences (KJ951-A1-501-03).
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