Exo-Methylene-BEDT-TTF and alkene-functionalised BEDT-TTF derivatives: Synthesis and radical cation salts

Article abstract of DOI:10.1039/c5ra03921e

Hydroxymethyl-BEDT-TTF is converted by tosylation and elimination into exo-methylene-BEDT-TTF whose exocyclic double bond leads to a small increase in the oxidation potential, and from which radical cation salts with perchlorate and triiodide have been pr

Full text of DOI:10.1039/c5ra03921e

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1
Exo-Methylene-BEDT-TTF
and
Alkene-
Derivatives:
functionalised
BEDT-TTF
Synthesis and Radical Cation Salts.
Matteo Zecchini,a Jordan R. Lopez,a Scott Allen,a Simon J. Coles,b Claire
Wilson,c Hiroki Akutsu,d Lee Martin,* John D. Wallis*
aSchool of Science and Technology, Nottingham Trent University, Clifton Lane,
Nottingham NG11 8NS, UK, eꢀmail: john.wallis@ntu.ac.uk
bUK National Crystallography Service, University of Southampton, Highfield Campus,
Southampton, SO17 1BJ, UK, eꢀmail: S.J.Coles@soton.ac.uk
cDiamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot,
Oxfordshire, OX1 0DE, UK, eꢀmail: claire.wilson@diamond.ac.uk
dDepartment of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan,
email: akutsu@chem.sci.osakaꢀu.ac.jp
Abstract. HydroxymethylꢀBEDTꢀTTF is converted by tosylation and elimination into exoꢀ
methyleneꢀBEDTꢀTTF whose exocyclic double bond leads to a small increase in the
oxidation potential, and from which radical cation salts with perchlorate and triiodide have
been prepared, the latter showing semiconductor properties. Allyloxymethylꢀ and
allylthiomethylꢀBEDTꢀTTF, the first BEDTꢀTTF derivatives with an alkene in the side chain,
have been prepared, along with a 1:2 radical cation perchlorate salt of the former, an
insulator which contains a donor dication.

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Introduction.
Organosulfur donors such as TTF 1 and BEDTꢀTTF 2 have been used as substrates for
preparation of conducting materials by oxidation either by electrocrystallisation or treatment
with electronꢀdeficient acceptor substances, leading to conducting, semiꢀconducting and in
some cases, superconducting materials.1 A wide range of substituted derivatives of these
donors has been prepared and applications explored.2 There has been less interest in donor 3,
known as VT, the fully unsaturated derivative of BEDTꢀTTF containing endocyclic double
bonds at both ends of the molecule, though several salts have been prepared.3,4 Substituted
derivatives of VT have been prepared including the tetraꢀmethyl, ꢀphenyl and ꢀpyridꢀ4ꢀyl
substituted derivatives, for example 4,5 as well as the dimethyl derivative 5 which has been
prepared as a mixture of cis and trans isomers.4 There are a few reports of the BEDTꢀTTF
derivative 6 where just one dithiin ring contains an extra double bond,6,7 and some of its
monosubstituted derivatives such as the methyl derivative 7.6,8 The inclusion of one or two
extra double bonds raises the oxidation potential from that of BEDTꢀTTF by 0.06 and 0.14 V
respectively.6 We have been interested in preparing donors with alkene functionality, partly
because of the potential for polymerising such systems, as well as for the donors themselves
as substrates for salt formation. Here we report the preparation of three new donors 8ꢀ10, one

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with an exocyclic double bond attached to the BEDTꢀTTF framework and thus a tautomer of
7, and two with an alkene group at the end of a side chain.
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
X
8
9
X = O
10 X = S
Discussion.
Synthesis and properties of exo-methylene-BEDT-TTF.
Scheme 1.
HydroxymethylꢀBEDTꢀTTF 12 is readily prepared in four steps from allyl acetate and
trithione 11,9 but has not been significantly exploited synthetically. We now report that
conversion to its Oꢀtosylate 139 and subsequent treatment with tꢀbutoxide eliminates tosic
acid to give exoꢀmethyleneꢀBEDTꢀTTF 8 which has an exocyclic double bond connected to
the BEDTꢀTTF system. We were unable to isomerise 8 to the donor 7 with an exocyclic
1
methyl group and endocyclic double bond. The H NMR spectrum of donor exoꢀmethylene
BEDTꢀTTF shows signals for the alkene hydrogens at δ: 5.13 and 5.22 ppm and for the
adjacent methylene group at δ: 3.52 ppm. In contrast donor 7 clearly shows the methyl and
vinyl hydrogen signals (δ: 2.11 and 6.53 ppm) from the unsaturated ring and quite a different
1
melting point.6,8 Furthermore, the H NMR of the dimethylꢀVT donor 5 also clearly shows
the presence of the methyl and vinyl hydrogens.4

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For the new donor 8 the consequence of conjugation of the organosulfur system with
the exocyclic bond is a small increase in the first two oxidation potentials from 0.52 and 0.94
V (relative to Ag/AgCl) for BEDTꢀTTF to 0.56 and 0.97 V for exoꢀmethyleneꢀBEDTꢀTTF.
Table 1. Cyclic voltammetry of donors 8, 9 and 10.
Compound
E1
E2
BEDTꢀTTF, 2
0.52
0.56
0.54
0.54
0.94
0.97
0.94
0.94
exoꢀmethyleneꢀBEDTꢀTTF, 8
allyloxymethylꢀBEDTꢀTTF, 9
allylthiomethylꢀBEDTꢀTTF, 10
Electrocrystallisation experiments on exoꢀ(methylene)BEDTꢀTTF 8 in the presence of
various anions were carried out, and the most successful was that with perchlorate which
gave thin black crystals of a 1:1 radical cation salt. Furthermore, diffusion of a
dichloromethane solution of iodine into a benzonitrile solution of 8 led to a 2:2:1 salt of the
donor monocation with triiodide and iodine which has been shown to be a semiconductor.
The crystal structure of the 1:1 salt with perchlorate was measured at 100 K. The
crystal system is monoclinic, in space group P21/c, with one donor cation and one perchlorate
anion in the asymmetric unit (Figure 1). The crystals are twinned and there is some
orientational disorder of the perchlorate ion, as well as some of the commonly observed
conformational disorder in the unsubstituted dithiin ring. The donor cations are organised in
centrosymmetric pairs, and these are packed in the bc plane along with the anions (Figure 2)
which isolate pairs from one another. However, there are short contacts between pairs which
lie side by side in the a direction (Figure 3). In the donor cation the effect of the exocyclic

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alkene is a shortening of the endocyclic bonds connecting it to its sulfur and carbon atom
neighbours to 1.758(13) and 1.457(18) Å. The alkene bond length is 1.32(2) Å but the
apparent shortness may be due to some slight positional disorder of the terminal methylene
group. The conformation of the substituted dithiin ring is an envelope with the sp3 carbon
atom at the envelope’s flap. The exocyclic sp2 methylene group lies to the opposite side.
Within a donor cation dimer there are four short S···S contacts
between the
centrosymmetrically related TTF moieties (3.375(4) and 3.504(5) Å), and there are four short
S···S contacts in the range 3.460(5)ꢀ3.535(5) Å between dimers (Figure 3), thus providing a
possible route for conduction of electrons through the structure. Unfortunately, the crystals
were too brittle for attachment of electrodes for conductivity measurements.
Figure 1. Molecular structure of the salt 8.ClO4 with anisotropic displacement parameters
drawn at the 50% level.

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Figure 2. Crystal packing of the salt 8.ClO4 viewed down the a axis.
Figure 3. Interꢀdimer S··· S contacts (Å) in the a direction in the salt 8.ClO4.

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The Xꢀray crystal structure of the salt formed from donor 8 and iodine showed that it
had a composition 2:2:1 donor:I3:I2. Two probe conductivity measurements showed that it
was a semiconductor with room temperature conductivity of 1.89 x 10ꢀ4 S cmꢀ1 and an
energy of activation of 0.373 eV. The crystal system is triclinic and the space group is P1¯ .
The asymmetric unit is composed of one donor cation, one triiodide and half of an iodine
molecule, since the iodine molecule lies on a centre of symmetry. The donor cations are
organised in face to face pairs, which are almost surrounded by iodine molecules and
triiodide anions (Figures 4 and 5). However, there are side to side contacts between adjacent
pairs of donor cations in the a direction (Figure 6). The IꢀI bonds length are 2.8054(13) Å in
the iodine molecule and 2.8730(10) and 2.9535(10) Å in the triiodide anion, and the two
species approach each other at 85o with a I···I contact of 3.3789(13) Å between them. Lines
of triiodide anions run through the structure between the donor cation pairs, with successive
short and long head to tail I···I contacts between triodides of 3.4274(11) and 3.8388(12) Å.
Within the radical cation pairs there are four short S···S contacts between the S atoms of the
TTF core, all of length 3.396(4) Å. In addition there are two sets of two short S···S contacts
between adjacent cation pairs of length 3.462(4) and 3.543(4) Å (Figure 6).
Figure 4. A face to face radical cation pair surrounded by triiodide anions and iodine
molecules in the crystal structure of 8.I3.0.5I2.

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Figure 5. Triodide/iodine network in the bc plane in the crystal structure of 8.I3.0.5I2.
Intermolecular contacts < 3.5 Å shown.
Figure 6. S···S contacts (Å) between adjacent dimers of donor cations in 8.I3.0.5I2.

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Synthesis of donors with a side chain alkene group.
Scheme 2.
Scheme 3.
Reaction of diallyl ether with an excess of the trithione 11 in hot toluene gave thione 14, the
product of one cycloaddition, as the main product in 68% yield. A small amount of the
bis(thione) 15, formed by both alkene groups reacting with a trithione molecule was also
isolated in 6% yield. Increasing the amount of the trithione in the reaction did not alter the
product distribution. Conversion of the thione 14 to oxo compound 16 with mercuric acetate

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proceeded in 83% yield, and the oxo compound was coupled with the unsubstituted thione 18
to yield the BEDTꢀTTF derivative with an allyloxymethyl side chain 9 in 53% yield after
separation from homoꢀcoupled products. The bis(thione) 15 decomposed slowly. Although it
can be converted to the corresponding bis(oxo compound) 17, attempts to couple this product
with 18 did not lead to any bis(BEDTꢀTTF) derivatives. The corresponding chemistry
starting with diallyl sulphide proceeded in a similar way though with lower yields. Thus,
reaction with trithione 11 gave the thione 19 resulting from just one cycloaddition in 31%
yield. This was converted in 53% yield to the oxo compound 20, which was then coupled to
the unsubstituted thione 18 to give the BEDTꢀTTF derivative with an allylthiomethyl side
chain 10 in 31% yield. Zhu et al. have reported the closely related alkyne analogue 21.10
The oxidation potentials of donors 9 and 10 were similar to those of BEDTꢀTTF.
Electrocrystallisation experiments with 9 have yielded a 1:2 perchlorate salt whose crystal
structure has been determined. Diffusion experiments with iodine only gave very small
crystals of low quality. The crystal structure of 9.2ClO4, measured at 100 K, is monoclinic,
in space group P21 and there are two donors each bearing a charge of 2+ and four perchlorate
anions in the unit cell. The crystal structure is shown in Figure 7. The donor dication shows
the typically very long bond between dithiole units of 1.44(2) Å, and the four central CꢀS
bonds, shortened by the 2+ charge, lie in the range 1.676(18)ꢀ1.717(18) Å similar to those
reported for the dication of BEDTꢀTTF.11 The monosubstituted donor is disordered between
two positions, which are roughly related by a 2 fold rotation about the long axis of the
molecule. The positions differ in the point of attachment of the side chain to the dithiin ring,
however the side chain lies so that the two structures have a common position for the terminal
allyloxy group. This is achieved by the dithiin ring in the two structures adopting an
approximate envelope conformation with the side chain attached to the “flap” methine carbon
and oriented in a pseudoꢀaxial manner (Figure 8). There is no stacking of donor dications,
but there are lines of dications along the a axis organised so that the molecules have edge to
edge S···S contacts in the range 3.630(7)ꢀ4.198(8) Å. Adjacent donors in the b direction are
strongly slipped relative to each other so that there are only three S···S contacts (3.728(7) ꢀ
3.785(6) Å) between sulfurs from the unsubstituted end of one donor with sulfurs from the

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substituted end of the next donor (Figure 9). The perchlorate anions are distributed among the
donor dications, and each donor has S···O contacts to four anions (Figure 10). Although
donor stacking and segregated anions are common in BEDTꢀTTF radical cation salts, the
larger donor charge in this case leads to anion contacts with the organosulfur residue.
Conductivity measurements showed that the material was an insulator as might be expected.
Figure 7. Crystal structure of 9.2ClO4 viewed down the a axis, showing the integration of
dicationic donors with anions.

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Figure 8. View of the donor dication of 9 showing the two disordered orientations of the side
chain and how they overlap.
Figure 9. Partial crystal packing diagram of 9.2ClO4 showing the relation between donor
dications in the a and b directions. Only one conformation of the disordered donor
is shown and anions are omitted for clarity.

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Figure 10. Contacts (Å) between the donor dication 92+ and perchlorate anions.
Conclusion.
The small size of the substituent on exoꢀmethyleneꢀBEDTꢀTTF 8 provides minimal steric
hindrance to crystal packing and may offer access to a wide range of new radical cation salts,
as observed for BEDTꢀTTF. The ready preparation of donors 9 and 10 with a terminal alkene
substituent provide donors with the potential for incorporation into polymers. Both of these
aspects are now under investigation in our laboratory.

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Experimental.
General. Solution NMR spectra were measured on a JEOL Eclipse 400 spectrometer at 400
1
MHz for H and at 100.6 MHz for 13C using CDCl3 as solvent and tetramethylsilane (TMS)
as standard unless otherwise stated, and measured in p.p.m. downfield from TMS with
coupling constants reported in Hz. IR spectra were recorded on a Perkin Elmer Spectrum 100
FTꢀIR Spectrometer using Attenuated Total Reflection sampling unless otherwise stated, and
are reported in cm−1. Mass spectra were recorded at the EPSRC UK National Mass
Spectrometry Facility at the University of Swansea. Chemical analysis data were obtained
from Mr Stephen Boyer, London Metropolitan University. Flash chromatography was
performed on 40–63 silica gel. Cyclic voltammetry was conducted on a Metrohm ꢁꢀAutolab
Type III.
exo-Methylene-BEDT-TTF, 8.
To a solution of tosyloxymethylꢀBEDTꢀTTF 139 (0.103 g, 0.18 mmol) in dry THF (5 ml)
under nitrogen was added sodium tertꢀbutoxide (27 mg, 0.28 mmol). The solution was stirred
at room temperature for 3 h. The solvent was evaporated, DCM added and the mixture
washed with water. The organic phase was collected and dried over Na2SO4. The product was
purified by flash chromatography (3:1 hexane : ethyl acetate) to yield donor 8 as an orange
solid (0.099 g, 97%), m.p. 165 oC (dec.). δH (400 MHz, CDCl3): 5.22 (1H, s, ꢀC=CHH), 5.13
(1H, s, ꢀC=CHH), 3.52 (2H, s, 6ꢀH2), 3.23 (4H, s, 5’ꢀ,6’ꢀH2); δC (100 MHz, CDCl3): 137.4
(CH=CH2), 117.1, 114.6, 113.8, 113.7, 113.5, 112.0 (2ꢀ,2’ꢀ,3aꢀ,3a’ꢀ,7aꢀ,7a’ꢀC) 111.0 (ꢀ
C=CH2), 36.5 (6ꢀC), 30.1 (5’,6’ꢀC); νmax: 2958, 2921, 2847, 1598, 1407, 1386, 1282, 1259,
1223, 1211, 1124, 1093, 1020, 899, 875, 799, 769, 729, 622, 530 496; found C, 33.45, H,
2.09%, C11H8S8 requires C, 33.33; H, 2.08%.
Radical cation salts of exo-methylene-BEDT-TTF, 8.
Perchlorate salt: To the anodic side of a Hꢀshaped electrochemical cell fitted with a glass frit
was placed donor 8 (5 mg, 0.0126 mmol), and to the cathodic side of the cell was added a
0.0089 M solution of tetrabutylammonium perchlorate in chlorobenzene (40 mL). The level
of solution in each compartment was allowed to equilibrate, and into each side was inserted a
platinumꢀtipped electrode. A constant current of 2.0 ꢁA was applied across the cell for 3 days
to give black needleꢀshaped crystals of 8.ClO4.

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Triiodide salt: A solution of donor 8 (10 mg) in dichloromethane (10 ml) was slowly diffused
into a solution of iodine (10 mg) in benzonitrile (10 ml) over two weeks to give black crystals
of 8.I3.0.5I2.
Syntheses of alkenyl-substituted donors 9 and 10.
5-(Allyloxymethyl)-5,6-dihydro-1,3-dithiolo[4,5-b]1,4-dithiin-2-thione, 14.
A suspension of trithione 11 (2.94 g, 15.0 mmol) and diallyl ether (0.49 g, 5.0 mmol) in
toluene (50 ml) was heated to reflux overnight, cooled to RT and filtered. The solid residue
was washed with toluene and the combined filtrates collected. The solvent was evaporated
and the residue purified by flash chromatography on silica (6:1 = cyclohexane:ethyl acetate)
(Rf 0.75) to yield compound 14 (0.99 g, 68%) as a red oil. δH (400 MHz, CDCl3): 5.81ꢀ5.91
(1H, m, ꢀCH=CH2), 5.27 (1H, dq, J = 17.3, 1.6 Hz, ꢀCH=CHHꢀtrans), 5.20 (1H, dq, J = 10.1,
1.6 Hz, ꢀCH=CHHꢀcis), 4.01 (2H dt, J = 5.7, 1.2 Hz, ꢀOꢀCH2ꢀCH=CH2), 3.83ꢀ3.89 (1H, m, 5ꢀ
H), 3.77 (1H, dd, J = 9.5, 8.5 Hz, 5ꢀCHα), 3.60 (1H, dd, J = 9.5, 5.5 Hz, 5ꢀCHβ), 3.27ꢀ3.36
(2H, m, 6ꢀH2); δC (100MHz, CDCl3): 207.7 (C=S), 133.7 (ꢀCH=CH2), 123.5, 122.1 (3aꢀ,7aꢀ
C), 117.8 (ꢀCH=CH2), 72.3 (ꢀOꢀCH2ꢀCH=CH2), 70.6 (5ꢀCH2ꢀOꢀ), 42.6 (5ꢀC), 31.3 (6ꢀC);
ν
max: 2928, 2852, 1644, 1469, 1448, 1408, 1346, 1283, 1262, 1093, 1061, 989, 909, 770,
679; HRMS: (ASAP) found: 294.9403 (100%), C9H10O1S5 +H requires: 294.9408; found C,
36.86; H, 3.46%, C9H10O1S5 requires C, 36.73; H, 3.40%.
Further elution of the column gave bis(2ꢀthioxoꢀ1,3ꢀdithiolo[4,5ꢀb]1,4ꢀdithiinꢀ5ꢀmethyl)ether
15 (Rf 0.35) (0.15 g, 6%) as a brown solid, m.p. 117 oC (dec). δH (400 MHz, CDCl3): 3.84ꢀ
3.93 (4H, m, ꢀCH2ꢀOꢀCH2), 3.69ꢀ3.77 (2H, m, 5ꢀ,5’ꢀH), 3.29ꢀ3.34 (4H, m, 6ꢀ,6’ꢀH2); δC
(100MHz, CDCl3): 207.5 (2 x C=S), 122.8, 121.9 (3aꢀ,3a’ꢀ,7aꢀ,7a’ꢀC), 76.7 ( ꢀCH2ꢀOꢀCH2ꢀ).
42.1 (5ꢀ,5’ꢀC), 31.2 (6ꢀ,6’ꢀC); νmax: 2847, 1478, 1404, 1261, 1112, 1054, 868, 517; HRMS:
(ASAP) found: 490.8003, C12H10O1S10 + H requires 490.8011; found C, 29.48; H, 2.15%,
C12H10OS10 requires C, 29.38; H, 2.04%. Over a period of time this compound decomposed.
5-(Allyloxymethyl)-5,6-dihydro-1,3-dithiolo[4,5-b]1,4-dithiin-2-one, 16.
To a solution of thione 14 (2.13 g, 7.3 mmol) in CHCl3 (100 ml) was added mercury (II)
acetate (5.70 g, 17.9 mmol) and the suspension left stirring for 4 h. under nitrogen at RT. The
solid obtained during the reaction was filtered and washed with CHCl3. The combined

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filtrates were neutralised with solid NaHCO3. The organic layer was collected and washed
with water, dried over MgSO4 and the solvent evaporated to give the desired compound 16
(2.70 g, 83%) as a yellowꢀbrown oil; δH (400 MHz, CDCl3): 5.77ꢀ5.87 (1H, m, ꢀCH=CH2),
5.23 (1H, dq, J = 17.2, 1.4 Hz, ꢀCH=CHHꢀtrans), 5.16 (1H, dq, J = 10.4, 1.4 Hz, ꢀCH=CHHꢀ
cis), 3.97 (2H, dt, J = 5.7, 1.3 Hz, ꢀOꢀCH2ꢀCH=CH2), 3.82ꢀ3.88 (1H, m, 5ꢀH), 3.75 (1H, t, J
= 9.6 Hz, 5ꢀCHα), 3.28 (1H, dd, J = 9.6, 5.6 Hz, 5ꢀCHβ), 3.23ꢀ3.32 (2H, m, 6ꢀH2); δC
(100MHz, CDCl3): 188.7 (C=O), 133.8 (ꢀCH=CH2), 113.9, 112.5 (3aꢀ,7aꢀC), 117.7
(CH=CH2), 72.3 (OꢀCH2ꢀCH=CH2), 70.7 (5ꢀCH2ꢀOꢀ), 44.3 (6ꢀC), 32.4 (5ꢀC); νmax: 2918,
2853, 1673, 1621, 1509, 1241, 1093, 825, 763, 542; HRMS: (ASAP) found: 278.9632,
C9H10O2S4 + H requires: 278.9636; found C, 38.69; H, 3.48%, C9H10O2S4 requires C, 38.85;
H, 3.60%.
(Allyloxymethyl)-BEDT-TTF, 9.
To a solution of oxo compound 16 (1.08 g, 3.90 mmol) in freshly distilled triethyl phosphite
(30 ml) was added unsubstituted thione 18 (1.74 g, 7.80 mmol) and the solution was left
stirring for 5 h. under nitrogen at 90oC. The BEDTꢀTTF formed was filtered off and the
triethyl phosphite was distilled off from the filtrate using a Kugelrohr apparatus. The residue
was purified using flash chromatography (3:1=cyclohexane:ethyl acetate) affording the
desired product 9 as an orange solid (0.94 g, 53%), which was recrystallized from
acetonitrile, m.p. 82ꢀ84oC. δH (400 MHz, CDCl3): 5.83ꢀ5.94 (1H, m, ꢀCH=CH2), 5.29 (1H,
dq, J = 16.9, 1.8 Hz, ꢀCH=CHHtrans), 5.22 (1H, dd, J = 10.5, 1.8 Hz, ꢀCH=CHHcis), 4.02 (2H,
dt, J = 5.5, 1.2 Hz, ꢀOꢀCH2ꢀCH=CH2), 3.78ꢀ3.84 (1H, m, 5ꢀH), 3.74 (1H, t, J = 9.2 Hz, 5ꢀ
CHα), 3.57 (1H, dd, J = 9.2, 5.0 Hz, 5ꢀCHβ ), 3.29 (4H, s, 5’ꢀ,6’ꢀH2), 3.19ꢀ3.28 (2H, m, 6ꢀH2);
δC (100 MHz, CDCl3): 134.0 (ꢀCH=CH2), 117.7 (CH=CH2), 114.2, 113.7, 113.3, 111.8,
111.6 (sp2ꢀC), 72.3 (OꢀCH2ꢀCH=CH2), 71.0 (5ꢀCH2), 43.0 (5ꢀC), 32.1 (6ꢀC), 30.1 (5’ꢀ, 6’ꢀC);
νmax: 3075, 2977, 2929, 2847, 1644, 1472, 1448, 1408, 1347, 1283, 1260, 1094, 986, 907,
770, 680, 652, 555, 500, 449; HRMS: (ASAP) found: 454.8881, C14H14OS8 + H requires:
454.8883; found C, 36.91; H, 3.15%, C14H14OS8 requires C, 37.00; H, 3.08%.
Bis(2-oxo-1,3-dithiolo[4,5-b]1,4-dithiin-5-methyl)ether, 17.
To a solution of 15 (0.75 g, 1.53 mmol) in CHCl3 (60 ml) was added mercury (II) acetate
(1.71 g, 5.36 mmol) and the suspension was left stirring at RT for 5 h. The solid was filtered

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off and the solution neutralised with saturated aqueous NaHCO3 (5 x 50 ml). The organic
phase was collected, washed sequentially with water (50 ml) and brine (50 ml) and dried over
MgSO4. Evaporation of the solvent gave the desired product 17 as a brown solid (0.64 g,
91%), m.p. 122ꢀ124oC. δH (400 MHz, DMSOꢀd6): 4.14ꢀ4.21 (2H, m, 5ꢀ, 5’ꢀH), 3.83ꢀ3.91
(2H, m) and 3.67ꢀ3.73 (2H, m) (ꢀCH2ꢀOꢀCH2ꢀ), 3.48 (2H, dd, J=13.6, 3.4 Hz) and 3.39 (2H,
dd, J=13.6, 6.3 Hz) (6ꢀ,6’ꢀH2); δc (100 MHz, DMSOꢀd6): 187.9 (2 x C=O), 114.2, 112.7 (3aꢀ
,3a’ꢀ,7aꢀ,7a’ꢀC), 71.4 (CH2ꢀOꢀCH2ꢀ), 44.4 (5ꢀ, 5’ꢀC), 32.0 (6ꢀ, 6’ꢀC); νmax: 2850, 1614, 1498,
1408, 1100, 768, 463; HRMS: (ASAP) found 458.8489, C12H10O3S8 + H requires 458.8468;
found C, 31.54; H, 2.29%, C12H10O3S8 requires C, 31.44; H, 2.18%. Attempted cross
coupling of 17 with thione 18 in triethyl phosphite was unsuccessful.
5-(Allylthiomethyl)-5,6-dihydro-1,3-dithiolo[4,5-b]1,4-dithiin-2-thione, 19.
A suspension of trithione 11 (5.82 g, 29.7 mmol) and diallyl sulphide (1.42 g, 11.9 mmol) in
toluene (160 ml) was heated to reflux overnight, cooled to RT and filtered. The solid residue
was washed with CHCl3 and the combined filtrates collected. The solvent was evaporated and
the residue purified by flash chromatography on silica (3:1 = cyclohexane:ethyl acetate) to
yield compound 19 (1.14 g, 31%) as a red oil. δH (400 MHz, CDCl3): 5.68ꢀ5.78 (1H, m, ꢀ
CH=CH2), 5.10 (1H, br d, J = 9.6 Hz, ꢀCH=CHHcis), 5.09 (1H, dd, J = 17.1, 1.4 Hz, ꢀ
CH=CHHtrans), 3.66ꢀ3.72 (1H, m, 5ꢀH), 3.30ꢀ3.41 (2H, m, 6ꢀH2), 3.14 (2H, d, J = 7.2 Hz,
CH2ꢀCH=CH2), 2.87 (1H, dd, J = 14.0, 8.8 Hz, 5ꢀCHα), 2.80 (1H, dd, J = 14.0, 5.9 Hz, 5ꢀ
CHβ); δC (100 MHz, CDCl3): 207.8 (C=S), 133.7 (ꢀCH=CH2), 123.1, 121.7 (3aꢀ,7aꢀC), 118.2
(ꢀCH=CH2), 42.5 (5ꢀC), 35.3 (5ꢀCH2ꢀS), 34.8 (ꢀSꢀCH2ꢀCH=CH2), 32.9 (6ꢀC); νmax: 2905,
1631, 1484, 1403, 1054, 917, 574; HRMS: (ASAP) found: 310.9179, C9H11S6 + H requires:
310.9180.
5-(Allylthiomethyl)-5,6-dihydro-1,3-dithiolo[4,5-b]1,4-dithiin-2-one, 20.
To a solution of thione 19 (1.10 g, 3.5 mmol) in CHCl3 (25 ml) under nitrogen was added
mercury (II) acetate (3.00 g, 9.4 mmol) and the suspension was left stirring for 2 h. at RT.
The solid obtained during the reaction was filtered and washed with CHCl3. The combined
filtrates were washed with a saturated solution of NaHCO3 (5 x 20 ml). The organic layer was
collected and washed sequentially with water and brine and dried over MgSO4 to give the

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desired compound 20 (0.60 g, 53%) as a pinkꢀred oil. δH (400 MHz, CDCl3): 5.67ꢀ5.78 (1H,
m, ꢀCH=CH2), 5.10 (1H, br d, J = 10.0 Hz, ꢀCH=CHHcis), 5.09 (1H, dd, J = 17.5, 1.3 Hz, ꢀ
CH=CHHtrans), 3.69ꢀ3.75 (1H, m, 5ꢀH), 3.39 (1H, dd, J = 13.4, 3.1 Hz, 6ꢀHα), 3.33 (1H,
dd, J = 13.4, 6.0 Hz, 6ꢀHβ), 3.14 (2H, d, J = 7.3 Hz, CH2ꢀCH=CH2), 2.89 (1H, dd, J =
13.9, 9.0 Hz, 5ꢀCHα), 2.81 (1H, dd, J = 13.9, 5.8 Hz, 5ꢀCHβ); δC (100 MHz, CDCl3): 188.9
(C=O), 133.8 (ꢀCH=CH2), 118.2 (CH=CH2), 113.5, 112.3 (3aꢀ,7aꢀC), 44.4 (5ꢀC), 35.4 (5ꢀ
CH2ꢀS), 34.9 (ꢀSꢀCH2ꢀCH=CH2), 34.2 (6ꢀC); νmax: 2910, 1670, 1628, 1503, 1405, 1226, 988,
916, 888, 754; found C, 36.60; H, 3.51%, C9H10OS5 requires C, 36.73; H, 3.40%.
(Allylthiomethyl)-BEDT-TTF, 10.
To a solution of oxo compound 20 (0.60 g, 2.05 mmol) in freshly distilled triethyl phosphite
(30 ml) was added unsubstituted thione 18 (0.92 g, 4.1 mmol) and the solution was left
o
stirring for 5 h. under nitrogen at 90 C. The BEDTꢀTTF formed during the reaction was
filtered off and the triethyl phosphite was distilled off from the filtrate using a Kugelrohr
apparatus. The crude red oil was purified by flash chromatography (6:1=cyclohexane: ethyl
o
acetate) affording the donor 10 as an orangeꢀred solid (0.30 g, 31%), m.p. 107ꢀ109 C. δH
(400 MHz, CDCl3): 5.67ꢀ5.77 (1H, m, ꢀCH=CH2), 5.08 (1H, br d, J = 10.8 Hz, ꢀCH=CHHcis),
5.07 (1H, dq, J = 16.4, 1.2 Hz, ꢀCH=CHHtrans), 3.58ꢀ3.63 (1H, m, 5ꢀH), 3.21ꢀ3.27 (2H, m, 6ꢀ
H2), 3.22 (4H, s, 5’ꢀ,6’ꢀH2), 3.12 (2H, d, J = 7.2 Hz, ꢀSꢀCH2CH=CH2), 2.82 (1H, dd, J = 14.0,
9.2 Hz, 5ꢀCHα) 2.75 (1H, dd, J = 14.0, 5.8 Hz, 5ꢀCHβ); δC (100 MHz, CDCl3): 133.7 (ꢀ
CH=CH2), 118.0 (CH=CH2), 113.8, 113.7, 112.8, 111.9, 111.6 (2ꢀ,2’ꢀ,3aꢀ,3a’ꢀ,7aꢀ,7a’ꢀC),
42.9 (5ꢀC), 35.3 (ꢀSꢀCH2ꢀCH=CH2), 34.9 (5ꢀCH2Sꢀ), 33.6 (6ꢀC), 30.1 (5’ꢀ, 6’ꢀC); νmax: 2915,
1633, 1517, 1399, 1287, 1203, 913, 882, 772; found C, 35.81; H, 2.93%, C14H14S9 requires
C, 35.74; H, 2.98%.
Radical cation salts of allyloxymethyl-BEDT-TTF, 9.
Perchlorate salt. To the anodic side of a Hꢀshaped electrochemical cell fitted with a glass frit
was placed donor 9 (10 mg, 0.022 mmol), and to the cathodic side of the cell was added a
0.0089 M solution of tetrabutylammonium perchlorate in chlorobenzene (40 mL). The level
of solution in each compartment was allowed to equilibrate, and into each side was inserted a
platinumꢀtipped electrode. A constant current of 0.5 ꢁA was applied across the cell for 4
weeks to give black needle shaped crystals of 9.(ClO4)2.

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X-ray crystallography.
Crystal data for 8.ClO4: C11H8S8.ClO4, Mr =496.10, monoclinic, a = 6.401(2), b = 16.234(5),
c = 16.417(5) Å, β = 95.579(9)°, V = 1697.9(9) Å3, Z = 4, P21/c, Dc = 1.941 g cmꢀ3, MoKα
( λ = 0.71073 Å), ꢁ = 1.224 mmꢀ1, T = 100(2) K, 12665 unique reflections (Rint = 0.16),
8291 with F2 > 2σ, R(F, F2 > 2σ) = 0.11, Rw (F2, all data) = 0.16. The data were measured at
the National Crystallography Centre,12 Southampton University on a Rigaku AFC12
diffractometer equipped with enhanced sensitivity (HG) Saturn724+ CCD detector mounted
at the window of an FRꢀE+ SuperBright molybdenum rotating anode generator (Mo Kα, λ =
0.71075 Å) with VHF Varimax optics (70 ꢀ
m focus) using Crystal Clear software13 for data
collection and reduction. The structure was solved with SHELXS97,14 and refined with
SHELX201315 within OLEX2.16 Data were collected from a twinned crystal. ROTAX17 was
used to identify the twin law, corresponding to a 2ꢀfold rotation about the 1 0 0 direction:
twin law [ 1.000 0.000 0.000] [ 0.000 ꢀ1.000 0.000][ ꢀ0.498 0.000 ꢀ1.000] and
the twin component fraction refined to 0.71. Disorder in the ClO4 anion was modelled with
two of the oxygen sites split over two sites with the occupancy refined competitively,
0.63/0.37(3), and isotropic atomic displacement parameters for partially occupied atoms.
Distance restraints were applied to the ClꢀO distances.
Crystal data for 8.I3.(I2)0.5: C11H8S8.I3.0.5I2, Mr = 904.28 , triclinic, a = 8.2014(15), b =
9.1986(16), c = 15.637(3) Å, α = 86.967(10), β = 86.049(10), γ = 72.972(7)°, V = 1124.6(4)
Å3, Z = 2, P1¯ , Dc = 2.670 g cmꢀ3, MoKα ( λ = 0.71073 Å), ꢁ = 6.281 mmꢀ1, T = 296(2) K,
4911 unique reflections (Rint = 0.026), 3208 with F2 > 2σ, R(F, F2 > 2σ) = 0.049, Rw (F2, all
data) = 0.15. Data were collected at room temperature using a Rigaku Mercury II CCD
configured with the Rigaku MicroMaxꢀ007HF generator and VariMax confocal mirror using
Crystal Clear software13 for data collection and reduction. The structure was solved by
SIR9218 and refined with SHELX201315 using the Rigaku CrystalStructure ® software
package.
Crystal data for 9.(ClO4)2: C14H14OS8.2ClO4, Mr = 653.63, monoclinic, a = 5.9156(4), b =
9.5177(7), c = 21.3112(16) Å, β = 97.871(4) °, V = 1188.58(13) Å3, Z = 2, P21, Dc =

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1.826 g cmꢀ3, MoKα (λ = 0.6889 Å), ꢁ = 0.942 mmꢀ1, T = 100(2) K, 9058 unique
reflections (Rint=0.08), 8296 with F2 > 2σ, R(F, F2 > 2σ) = 0.079, Rw (F2, all data) = 0.22.
The data were collected using synchrotron Xꢀray radiation (λ = 0.6889 Å) at the Diamond
Light Source, UK using Beamline I19 situated on an undulator insertion device with a
combination of double crystal monochromator, vertical and horizontal focussing mirrors and
a series of beam slits (primary white beam and either side of the focussing mirrors). The
experimental hutch (EH1) is equipped with a Crystal Logic 4ꢀcircle kappa geometry
goniometer with a Rigaku Saturn 724 CCD detector and an Oxford Cryosystems Cryostream
plus cryostat (80ꢀ500K). Data reduction, cell refinement and absorption correction were
performed using CrystalClearꢀSM Expert 2.0 r5.13 The structure was solved with
SUPERFLIP19 and refined with SHELXL201315 within OLEX2 Graphics in OLEX2.16 The
structure was refined as a 2ꢀcomponent twin; twin law (1 0 0 / 0 ꢀ1 0 / ꢀ1 0 ꢀ1) corresponding
to 2ꢀfold rotation about the 1 0 0 direction. Twin law identified using ROTAX and hklf5 file
generated through WINGX.20 Twin scale factor refined to 0.394(4). Disorder was present in
the sp3 carbon atoms of the substituted dithiin ring and the first methylene carbon of the side
chain, and these were modelled over two half occupied sites. Distance restraints were applied
and atoms were refined with isotropic displacement parameters. All geometric analyses were
performed using PLATON21 and all illustrations were made with MERCURY.22 Data is
deposited at the Cambridge Crystallographic Data Centre with code numbers CCDC
1051494ꢀ1051496.
Conductivity Measurements.
Twoꢀprobe DC transport measurements were made on several crystals of 8.I3.0.5I2 using a
HUSO HECS 994C multiꢀchannel conductometer, and on crystals of 9.(ClO4)2 using an
Oxford Instruments Optistat and temperature controller. Gold wires were attached to the
crystal, and the attached wires were connected to an fourꢀpin integrated circuit plug with
conductive cement.
Acknowledgements.
We thank Nottingham Trent University for PhD grants (MZ, JRL) and the EPSRC UK
National Mass Spectrometry Facility at Swansea University for data. We thank EPSRC for
funding the National Crystallography Service including access to Synchrotron facilities at the
Diamond Light Source, LM thanks the Royal Society for Research Grants (RG100853 and

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RG081209), an International Exchange Scheme (IE130367) and an International Joint Project
(JP0869972). LM thanks the Royal Society of Chemistry for a Journals Grant for
International Authors.
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