Aryl ester dendrimers incorporating tetrathiafulvalene units: Convergent synthesis, electrochemistry and charge-transfer properties

Article abstract of DOI:10.1039/a800225h

The convergent synthesis of a range of aryl ester dendrimers with peripheral tetrathiafulvalene (TTF) units is reported. 4-(Hydroxymethyl)-TTF and 4,5-(2-hydroxymethylpropane-1,3-diyldithio)-TTF have been used as the starting TTF reagents. The core reagen

Full text of DOI:10.1039/a800225h

J O U R N A L O F
Aryl ester dendrimers incorporating tetrathiafulvalene units:
convergent synthesis, electrochemistry and charge-transfer properties
Wayne Devonport, Martin R. Bryce,*† Gary J. Marshallsay, Adrian J. Moore and
Leonid M. Goldenberg
C H E M I S T R Y
Department of Chemistry, University of Durham, Durham, UK DH1 3L E
The convergent synthesis of a range of aryl ester dendrimers with peripheral tetrathiafulvalene (TTF) units is reported.
4-(Hydroxymethyl)-TTF and 4,5-(2-hydroxymethylpropane-1,3-diyldithio)-TTF have been used as the starting TTF reagents.
The core reagents are benzene-1,3,5-tricarbonyl trichloride, terephthaloyl chloride, biphenyl-4-4∞-dicarbonyl chloride and 4,4∞-
oxybis(benzenecarbonyl chloride). Dendrimers comprising up to 12 TTF units have been characterised by elemental analysis,
plasma desorption mass spectrometry, 1H NMR spectroscopy and solution electrochemistry. Cyclic voltammetry (CV) and ultra
microelectrode CV studies show that the TTF dendrimers display nearly ideal redox behaviour for the TTF system with no
significant interaction between the TTF units. Thin layer cyclic voltammetric studies show that all the TTF units of these systems
undergo two, single-electron oxidations. The dendrimers form charge-transfer complexes upon reaction with iodine in solution.
Intermolecular interactions of the TTF radical cations are observed in the UV–VIS spectra of some of the oxidised derivatives.
The synthesis and characterisation of dendrimers, cascade
molecules and related hyper-branched systems is a rapidly-
expanding topic in polymer science.1 These materials comprise
a multifunctionalised core, from which radiate repeating layers
of monomers with a branch occurring at each monomer unit.
They possess well-defined, three-dimensional structural order,
and their size and architecture can be precisely controlled in
their synthesis, providing unique molecular frameworks for the
disposition of functional groups in predetermined spatial
arrangements. Initial research into dendrimers focused on the
synthesis of higher generation systems with large molecular
weights and dense surface packing.2 As synthetic methodology
has developed, the emphasis has clearly changed towards
systems which incorporate more elaborate functional groups3
at the exterior surface of, or embedded within, the dendrimer
framework, e.g. crown ethers,4 chiral units,5 polynuclear metal
complexes,6 liquid crystal groups7 and saccharide units,8 which
impart special properties to these macromolecules. In the
context of functional dendrimers, a variety of redox-active
organic and organometallic groups9 have been incorporated
into the structures with several long-term aims in mind. These
include: (i) new electron-transfer catalysts; (ii) studies on the
dynamics of electron transport at surfaces and within restricted
reaction spaces; (iii) new materials for energy conversion; (iv)
organic semiconductors; (v) organic magnets; and (vi) mimics
of biological redox processes.
Some dendrimers contain a single redox-active unit (e.g. a
metalloporphyrin) at the core, and the solution redox behav-
iour of this central ‘encapsulated’ group is modulated by the
shielding effect of the outer spheres of the dendrimer struc-
ture.10 More commonly, however, organometallic redox units,
e.g. ferrocene and related metal sandwiches11 or metal(bipyri-
dyl),6 are emplaced at peripheral sites and/or within the
branches. The redox groups may behave independently in
multi-electron processes (n identical electroactive centres giving
rise to a single n-electron wave) or they may interact intra- or
inter-molecularly, in which case overlapping or closely-spaced
redox waves are observed at different potentials.
The incorporation of TTF into dendrimers presents a fascinat-
ing prospect for the following reasons: (i) oxidation of TTF to
the cation radical and dication species occurs sequentially and
reversibly at low potentials in a range of organic solvents (see
Table 1); (ii) the oxidation potentials can be finely tuned by
substituents on the TTF ring system; (iii) TTF cation radicals
are thermodynamically very stable; (iv) oxidised TTF units
have a high propensity to form dimers or ordered stacks, along
which there can be high electron mobility, and (v) TTF is
stable to many synthetic transformations, although it is import-
ant to avoid strongly acidic conditions and strong oxidising
agents. Most multi-TTF derivatives13 are dimers,14 although
some trimers,15 pentamers,16 higher oligomers,17 and main-
chain and side-chain polymeric TTFs18 are known. A feature
of these multi-TTF systems is that in general they readily yield
multiply-charged species upon electrochemical oxidation in
solution. Our aim was to synthesise structurally well-defined
multi-electron redox systems, exploiting the known solubility
enhancement in highly-branched macromolecules, compared
to their linear counterparts.
Results and Discussion
Synthesis
We now describe in detail the synthesis of aryl ester dendri-
mers19 functionalised with peripheral TTF groups.20 4-
(Hydroxymethyl)-TTF 112 has served as a convenient starting
material. A convergent strategy, based on a repetitive coupling/
deprotection sequence, has furnished dendrimer 12 comprising
a 1,3,5-benzene triester core, surface-functionalised with 12
TTF units (Scheme 1). In a convergent synthesis,21 dendrimer
construction begins at what will become the surface of the
molecule, and progresses inwards via a series of dendron
wedges of increasing size, several of which are attached to the
core unit in the final step. The functionalised reagent which
we used for the esterification reactions that built up successive
generations is 5-(tert-butyldimethylsilyloxy)isophthaloyl chlor-
ide 4.19 A conceptually similar synthesis, using a new TTF
derivative 20, is shown in Scheme 2. A series of bifunctional
cores have also been used, as shown in Schemes 3–5.
We recognised that advances in the synthesis of mono-
functionalised tetrathiafulvalene (TTF) derivatives12 offered
the possibility of constructing dendrimers bearing TTF units.
At the outset of this work, we established that 4-(hydroxy-
methyl)-TTF 1 readily formed esters under mild conditions,
and that the products were stable to silica gel chromatography,
†E-mail: m.r.bryce@durham.ac.uk
J. Mater. Chem., 1998, 8(6), 1361–1372
1361

Table 1 Solution electrochemical data obtained by CV and UV–VIS spectroscopya
compound
E 1/2/V
E 1/2/V
l
/nm
l
/nm after addition of I
1
2
max
max
2
TTF
3
6
7
9
12
20
21
23
24
25a
26a
27a
25b
26b
27b
25c
26c
27c
28
0.34
0.42
0.42
0.45
0.42
0.43
0.50
0.52
0.50
0.52
0.41
0.42
0.44
0.40
0.43
0.41
0.40
0.40
0.41
0.41
0.71
0.84
0.81
0.86
0.81
0.86
0.82
0.83
0.82
0.83
0.84
0.83
0.86
0.81
0.85
0.82
0.83
0.84
0.82
0.83
228, 312, 320, 365, 450
220, 307, 365
222, 306
220, 263, 305, 360
223, 299, 364, 433
220, 295, 363
232, 295, 366, 442, 590
225, 363, 439, 590
222, 306, 591
222, 294, 363, 590
222, 299, 364, 433, 590
223, 262, 291, 363, 590
293, 335, 367, 800
233, 290, 359, 815
233, 290, 338, 812
230, 296, 335, 827
222, 295, 362, 516
221, 294, 365, 433, 516
221, 294, 365, 433, 516
221, 291, 365, 516
262, 318, 363, 438, 528, 831
233, 296, 368, 545, 836
222, 280, 363, 437, 578, 820
233, 281, 314, 530, 830
233, 281, 362, 525, 830
230, 295, 363, 444, 590
265, 334
227, 263, 332, 443
233, 263, 335, 395
233, 263, 311, 335, 440
222, 242, 302, 370
222, 250, 300, 362
222, 250, 300, 362
223, 291, 363
293, 365, 398
229, 306, 370
222, 270, 308, 363
223, 307, 364
233, 281, 362
232, 312, 320, 364, 444
aCV data were obtained at 20 °C vs. Ag/AgCl, under argon using a platinum working electrode (1.6 mm diameter)
and a platinum wire counter electrode, ca. 5×10−4  compound, electrolyte 0.1  Bu N+PF −, scan rate
except for compounds 25a, 26a, 27a, 25b, 26b and 27b, for which all data (CV and UV–VIS) were obtained in DMSO.
4
6
100 mV s−1. CV data were obtained in MeCN–CH Cl (151 v/v); UV–VIS data obtained in CH Cl at 20 °C,
2
2
2 2
but not to acidic media.12 In an initial model experiment for
dendrimer synthesis, compound 1 reacted with benzene-1,3,5-
tricarbonyl trichloride 2, using triethylamine as base in
dichloromethane at room temperature, to afford the tris(TTF)
derivative 3 in 85% yield. The analogous reaction of 1 with
the silyl-protected diacid chloride 4 gave compound 5 (83%
yield), deprotection of which [tetra-n-butylammonium fluoride
(TBAF) in tetrahydrofuran (THF) at room temperature]
afforded the bis(TTF) derivative 6 (85% yield) as a first
generation dendron wedge containing the phenolic group as a
reactive handle for further functionalisation. The hexakis(TTF)
dendrimer 7 was obtained in 75% yield from reaction of 6
with triacid chloride 2, in the presence of 4-dimethylaminopyri-
dine (DMAP) as base (dichloromethane, room temperature).
This reaction required DMAP as base: no reaction occured
when triethylamine (the base used in the synthesis of 3) was
used instead. Following the same procedures that gave com-
pounds 5 and 6, reaction of two equivalents of alcohol 6 with
reagent 4 yielded the silyl protected derivative 8 (76% yield)
and hence dendron wedge 9 in 95% yield. By iterative pro-
cedures, compounds 9 and 4 reacted in the presence of a
mixture of N,N-dimethylaniline and 4-dimethylaminopyridine
(optimum ratio ca. 151 v/v) to yield octakis(TTF) derivative
10 in 76% yield. It was notable that no product was obtained
using either triethylamine, N,N-dimethylaniline, or DMAP as
the sole base: there is precedent for this in the work of Miller
et al., who noted that careful selection of the correct base was
necessary for the synthesis of each generation of aryl ester
dendrimers.19 Compound 10 was desilylated, as before, to yield
phenol derivative 11 (50% yield). Compound 9 reacted with
benzene-1,3,5-tricarbonyl trichloride 2 to give the dodeca(TTF)
dendrimer 12 in 48% yield.
desorption mass spectra (PDMS) were consistent with the
proposed structures. Solids were pure by combustion analysis.
We next sought to vary the structure of the TTF unit in
these macromolecules, and to this end we chose the new
derivative 4,5-(2-hydroxymethylpropane-1,3-diyldithio)TTF
20. The methylthio substituents were attached as they are
known to enhance the solubility of TTF derivatives, without
significantly affecting the redox properties.22 We envisaged that
the hydroxymethyl substituent in compound 20 would function
as a reactive alcohol (similar to compound 1) in esterification
reactions, and be less sterically hindered than the hydroxy
analogue, 4,5-(2-hydroxypropane-1,3-diyldithio)TTF, which
we had synthesised previously.22
The synthesis of compound 20 and its esterification reactions
are shown in Scheme 2. Thione 15 was prepared by reaction
of alcohol 1323 with zincate salt 1424 in refluxing acetonitrile
in 85% yield. The hydroxymethyl functionality was protected
as its tert-butyldiphenylsilyl ether derivative 16, in 84% yield,
by reaction with tert-butyldiphenylsilyl chloride in the presence
of imidazole in DMF.25 The thione group was then oxidised
to the corresponding ketone 17 under standard conditions
(mercuric acetate in chloroform–acetic acid)24b,26 in 88% yield.
Ketones 17 and 1827 were then cross-coupled in the presence
of triethyl phosphite at 130 °C,28 to yield TTF derivative 19,
which was not separated from self-coupled products. After
treatment of the mixture of TTF derivatives with TBAF in
THF, alcohol 20 was isolated in 31% overall yield for the two
steps. 1H NMR spectroscopy revealed that alcohol 20 exists
as a mixture of two conformational isomers, where the
hydroxymethyl group at C-2 can be axial or equatorial with
respect to the locked conformation of the seven-membered
ring.22 As a model reaction, three-fold esterification of 20 was
achieved by reaction with reagent 2, using DMAP as base, to
afford compound 21 as an orange solid in 57% yield.
Dendrimer 24 was then synthesised as shown in Scheme 2 via
compounds 22 and 23. In contrast to the silyl deprotection
reactions in Scheme 1, the reaction of 22 with TBAF in THF
was not straightforward and unless very dilute reaction con-
ditions were used, the formation of 23 was accompanied by
decomposition to form brown, oily products. Nonetheless,
alcohol 23 could be isolated as an orange solid in an optimised
yield of 66%. Esterification of 23 required far harsher con-
ditions than the comparable reactions of alcohols 6 or 20.
Deprotonation of alcohol 23 was achieved using sodium
Molecule 3 was stable for several months at room tempera-
ture, whereas 7 and 12 were stable only when stored at <0 °C;
when stored at room temperature, even in the dark and under
an argon atmosphere, they decomposed after a few days.
Stability of the dendrimers and the dendron wedges decreased
with increasing generation, so no attempts were made to
assemble molecules of higher generation by reactions of 11.
These TTF macromolecules were purified by chromatography
on silica gel and they were isolated as yellow–orange solids
(compounds 3 and 5–8) or as oils (compounds 9–12), all of
which were soluble in polar organic solvents. They were >98%
pure as judged by 1H NMR spectroscopy, and their plasma
1362
J. Mater. Chem., 1998, 8(6), 1361–1372

S
S
S
S
R
O
O
S
S
S
S
S
S
S
S
i
OH
Cl
O
O
O
O
Cl
2 R = C(O)Cl
4 R = OSiMe2But
O
O
1
S
S
S
3
S
S
S
ii
S
S
S
S
S
S
O
O
O
O
R
S
S
S
O
O
O
O
S
iv
O
O
O
5 R = OSiMe2But
O
O
S
S
S
S
O
O
iii
S
6 R = OH
O
O
S
S
S
S
O
S
S
O
O
S
O
O
S
S
v
S
S
S
S
S
7
S
R
O
O
O
S
S
O
O
O
O
S
S
S
S
S
S
O
O
O
O
O
S
S
S
S
S
S
S
S
8 R = OSiMe2But
9 R = OH
vi
Scheme 1 Reagents and conditions: i, Et N, compound 2, CH Cl , 20 °C; ii, Et N, compound 4, CH Cl , 20 °C; iii, TBAF, THF, 20 °C; iv, DMAP,
3
2
2
3
2 2
compound 2, CH Cl , 20 °C; v, DMAP, compound 4, CH Cl , 20 °C; vi, TBAF, THF, 20 °C; vii, DMAP–N,N-dimethylaniline, compound 4,
2
2
2 2
CH Cl , 35 °C; viii, TBAF, THF, 20 °C; ix, DMAP–N,N-dimethylaniline, compound 2, CH Cl , 35 °C.
2
2
2 2
hydride in refluxing THF (no reaction was observed using
DMAP in refluxing dichloromethane) and the resulting alkox-
ide reacted with reagent 2 to afford dendrimer 24 as an orange
oil in 58% yield. Compounds 23 and 24 were harder to purify
and were less stable than their analogues 6 and 7, so we did
not develop further the chemistry of TTF derivative 20 in this
context.29
Instead, in attempts to improve dendrimer stability, we
opted to change from trifunctional to bifunctional core units,
with a view to obtaining more open structures. Thus, using
J. Mater. Chem., 1998, 8(6), 1361–1372
1363

Scheme 1 (continued)
reagent 1 as the TTF derivative, terephthaloyl chloride, biphe-
nyl-4,4∞-dicarbonyl dichloride and 4,4∞-oxybis(benzenecarbonyl
chloride) gave the oligoester systems 25–27, respectively
(Schemes 3–5).30 As in Scheme 1, it was necessary to choose
carefully the base for the esterification reactions of alcohols 1,
6 and 9. The compounds containing the benzene and biphenyl
cores, viz. 25a,31 25b, 26a, 26b, 27a and 27b, were only sparingly
soluble in organic solvents, whereas analogues 25c, 26c and
27c, with the more flexible diphenyl ether core unit, showed
good solubility in polar organic solvents (e.g. acetone and
dichloromethane). The three series of compounds 25a–c, 26a–c
and 27a–c were all stable upon storage at room temperature
in air and daylight for at least one year, which is in marked
contrast to the analogues in Schemes 1 and 2, which are built
around the benzene triester core, where the high density of
ester groups in the interior of the molecule appear to be
responsible for the instability.
Electrochemical redox properties
An important aspect of this work was to evaluate the solution
redox properties of the materials synthesised. A variety of
1364
J. Mater. Chem., 1998, 8(6), 1361–1372

Scheme 2 Reagents and conditions: i, MeCN, reflux; ii, tert-butyldiphenylsilyl chloride, imidazole, DMF, 20 °C; iii, mercuric acetate, CHCl –glacial
3
AcOH, 20 °C; iv, triethyl phosphite, 130 °C; v, TBAF, THF, 20 °C; vi, DMAP, compound 2, CH Cl , 20 °C; vii, DMAP, compound 4, CH Cl ,
2
2
2 2
20 °C; viii, TBAF, THF, 20 °C; ix, NaH, compound 2, THF, reflux
electrochemical techniques were used, viz. cyclic voltammetry
(CV) using platinum electrodes, and CV using platinum ultra-
microelectrodes (UME CV), chronoamperometry (CA) and
thin layer cyclic voltammetry (TLCV). An initial study was
made using CV. Data are collated in Table 1 for a selection of
the new compounds, together with TTF and the model TTF
phenyl ester derivative 28 (prepared by reaction of compound
112 with benzoyl chloride, 92% yield) for comparison.
Experiments were performed in a mixture of acetonitrile and
dichloromethane (151 v/v) except for derivatives 25a, 25b, 26a,
J. Mater. Chem., 1998, 8(6), 1361–1372
1365

The study revealed that accurate data could be obtained only
for TTF itself, for which calculations34a gave values of 1 0.07
electrons (e) for each wave. For dimeric TTF system 6, calcu-
lations suggested that the first and second waves corresponded
to 2.1 0.1 and 1.8 0.1 e, respectively, which was in reasonable
agreement with the expected value of 2.0 e for each wave. For
the higher TTF oligomers, calculations of the number of
electrons transferred at each redox wave, using the combined
data of CV and CA to eliminate unknown diffusion
coefficients,35 or UME CV and CV/CA34a gave irreproducible
results between different experiments. Possible reasons for this
are: (i) adsorption and electrode passification, and/or (ii) errors
in determining the concentration of the dendrimers due to
their low solubility and the very small amounts of material
used. [The concentration of our dendrimers was ca. two orders
of magnitude lower than in ref. 34(a).] For other dendrimers
and branched systems containing multiples of structurally very
similar (or identical) redox groups (e.g. ferrocene11c and related
iron sandwiches11a) the extent of oxidation of the system has
been calculated using formulae which take into account the
different diffusion coefficients of a reference compound and the
dendrimer. However, applying these methods34a to our TTF
derivatives gave inconclusive results.36 Assuming full oxidation,
from the limiting currents at the ultra-microelectrode, diffusion
coefficients of the TTF oligomers were, as expected, lower than
those of TTF itself,37 but the values did not correlate with the
molecular weights of the oligomers, so this method could not
be used reliably with this series of compounds. A general trend,
for all the series of compounds in Schemes 1–5, was that with
increasing molecular size (i.e. increased numbers of TTF units),
the first redox wave broadened, whereas the second wave
sharpened. Similar behaviour has been reported previously for
O
S
S
S
S
O
Ph
28
26b, 27a and 27b, where insolubility forced us to use dimethyl
sulfoxide as the solvent. These experiments established that all
the compounds exhibited two redox couples typical of the
TTF system (i.e. the sequential formation of the TTF cation
radical and the TTF dication).32 It was noted that the silyl
ether derivatives tended to adsorb onto the electrode, resulting
in narrower waves: data for these compounds, are, therefore,
not included in Table 1. The attachment of alkylthio substitu-
ents to TTF is known to raise the oxidation potential32,33 (an
additive effect has been noted for one, two and four alkylthio
substituents)33 and this effect is manifested in a small anodic
shift in the values of E (but not E ) for compounds 19, 21, 23
and 24, which contain four alkylthio groups, relative to the
other compounds in Table 1. For compound 28 and the bis-
TTF systems 6, 23 and 25a–c, the redox waves were reversible,
at least up to scan rates of 500 mV s−1: the criterion applied
for reversibility was a ratio of 1.0 0.1 for the intensities of
the cathodic and anodic currents I /I , and no shift of the half
1
2
c
a
wave potentials with varying scan rates. For oligomers contain-
ing more than two TTF groups, slightly increased peak separa-
tions at higher scan rates were observed, consistent with quasi-
reversible behaviour.
We performed extensive CV and UME CV studies34 in
attempts to determine the number of electrons involved in the
two redox waves of the TTF dimers, wedges and dendrimers.
TTF amides immobilised on RuO or PtO electrode surfaces,38
and the data can be explained by adsorption or precipitation
2
S
on the UME. The CV and UME CV of dendrimer 12 are
shown in Figs. 1(a) and (b), respectively.
O
Cl
O
S
S
CORE
i
The electrochemistry of the stable bis-, tetra- and octa-TTF
derivatives 25c, 26c and 27c was studied using TLCV tech-
niques.39 Integrating the voltammetric waves against the one-
electron reduction peak of the internal standard 2,3-dichloro-
naphthoquinone (DCNQ) provided clear evidence that com-
plete oxidation occurs for all the TTF units in these
compounds, and we suggest that this is likely to be the case
for all the compounds in Schemes 1–5. We note that for
compound 27c the second TTF oxidation wave was slightly
narrower than the first wave, which was probably due to
adsorption phenomena. Fig. 1(c) shows the TLCV of com-
pound 27c in the presence of DCNQ. These TLCV data are
qualitatively similar to those we have reported recently for a
structurally very different family of TTF dendrimers, where
complete oxidation of all the TTF groups was also observed.40
We suggest, therefore, that TLCV is the most reliable method
for assessing the extent of oxidation of multi-TTF derivatives
in solution.
Cl
S
1
O
O
O
O
CORE
S
S
S
25a–c
S
a
b
c
=
CORE
CORE
=
=
CORE
O
Scheme 3 Reagents and conditions: i, NEt (for 25a), DMAP (for 25b
and 25c) CH Cl , 20 °C
3
2
2
S
S
S
S
O
S
O
S
S
O
O
S
S
O
Cl
O
O
O
O
O
O
O
CORE
i
CORE
Cl
O
S
6
O
S
S
S
S
S
S
26a–c
Scheme 4 Reagents and conditions: i, DMAP, CH Cl , 20 °C (a–c as Scheme 3)
2
2
1366
J. Mater. Chem., 1998, 8(6), 1361–1372

S
S
S
S
S
S
S
S
S
S
S
S
O
S
S
S
O
O
S
O
O
O
O
O
O
O
O
O
O
Cl
O
O
O
O
O
O
CORE
i
Cl
CORE
9
O
O
O
O
O
O
O
O
S
O
O
S
S
S
O
S
S
S
S
S
S
S
S
S
S
S
S
27a–c
Scheme 5 Reagents and conditions: i, DMAP–N,N-dimethylaniline, CH Cl , 35 °C (a–c as Scheme 3)
2
2
Charge-transfer complexes
TTF is famous for its ability to form charge-transfer com-
plexes41 with electron acceptors, e.g. halogens.42 UV–VIS
Spectroscopy is a convenient method for monitoring the
formation of TTF cation radicals, which have a characteristic
absorption band at l =580 nm for unsubstituted TTF.43 As
mentioned earlier, oxidised TTF units can form dimers or
max
stacks, and they display lower energy absorptions, e.g. 830 nm
for (TTF+·) dimers.43b,44 To assess the ability of our TTF
2
dendrimers to undergo chemical oxidation, UV–VIS spectra
were obtained in dichloromethane or DMSO solution before
and after the addition of iodine (Table 1). There were significant
changes in the spectra upon addition of iodine. All the com-
pounds derived from 4-(hydroxymethyl)TTF 1 showed a new
band with a l value between 516 and 590 nm. Additionally
max
for compounds 21, 23, 24, 25c, 26b, 26c, 27b and 27c a low
intensity, broad absorption band was present with a l value
max
between 810 and 836 nm. The higher energy band is consistent
with the formation of isolated (non-interacting) TTF cation
radicals, while the lower energy band suggests the existence of
interacting cation radical dimers. Addition of iodine to solu-
tions of compounds 21, 23 and 24, i.e. those derived from 4,5-
(2-hydroxymethylpropane-1,3-diyldithio)TTF 20, resulted in
no absorption in the 500–600 nm region; the lower energy
band with a l
value between 812–827 nm was, however,
max
clearly observed, suggesting that dimerisation is especially
favoured with these derivatives. Dilution studies for the stable
dendrimers 26b, 26c, 27b and 27c established that the absorp-
tion coefficient of this band decreased with increasing dilution,
which is, therefore, assigned to an intermolecular dimer band.
These data provide evidence that the oxidised dendrimers self-
associate in solution, by virtue of intermolecular interactions
of their peripheral TTF cation radicals. It is not clear why the
low energy dimer absorption is not seen for some of the
compounds in Table 1 (indeed, we did not observe it for TTF
itself under these conditions); subtle conformational factors at
the periphery of the macromolecules appear to be important
in determining whether or not dimer formation is energetically
Fig. 1 Solution electrochemistry: (a) CV of dendrimer 12 (solvent
MeCN, electrolyte Bu N+PF −, Pt electrode, vs. Ag/AgCl, scan rate
4
6
100 mV s−1); (b) UME CV of dendrimer 12 [solvent MeCN–CH Cl
2
2
(151 v/v), electrolyte Bu N+PF −, Pt electrode, vs. Ag/AgCl, scan rate
4
6
50 mV s−1]; (c) TLCV of compound 27c (0.5×10−4 ) and 2,3-
dichloronaphthoquinone (4.0×10−4 ) as internal reference (which
gives rise to the wave at negative potential) in 1  Bu N+PF −CH Cl
4
6
2 2
solution, vs. Ag/Ag+, scan rate 10 mV s−1
J. Mater. Chem., 1998, 8(6), 1361–1372
1367

favourable. The relatively rigid and short aryl ester units in
our systems presumably disfavour intramolecular dimerisation.
These observations are timely in the light of studies of intra-
molecular interactions of naphthalene diimide anion radicals
at the periphery of flexible poly(amidoamine) dendrimers.45
Intermolecular self-association of dendrimers by hydrogen-
bonding46 or coordinative bonds47 has also been reported
recently.
rather, intermolecular interactions (as seen in the UV–VIS
spectra) should be preferable.
Conclusions
This investigation has combined two different topics in contem-
porary materials chemistry, namely the study of functionalised
TTF systems and dendritic macromolecules. Convergent meth-
odology has provided aryl ester dendrimers with peripheral
TTF groups, and established that these compounds possess
well-defined redox activity, affording highly-charged cationic
species. The higher generation TTF dendrimers containing the
benzene triester core were stable only when stored at <0 °C,
whereas the analogues with a diphenyl ether core enjoy good
shelf stability and are soluble in organic solvents. Several new
functionalised TTF and multi-TTF derivatives have been
synthesised during the course of this work, and those possessing
reactive alcohol substituents, e.g. compounds 6, 9, 20 and 23,
are available in synthetically useful quantities and should be
suitable for other synthetic transformations for the incorpor-
ation of TTF units into new materials.
Molecular modelling studies
Molecular modelling studies were performed on selected com-
pounds. We first found the energetically most favourable
conformer of subunit 28 to provide an appropriate confor-
mation for use in the minimisation of the dendrimer structures.
The energy-minimised conformations of compounds 12 and
27b are shown in Fig. 2(a) and (b), respectively. The electro-
chemical and UV–VIS spectrophotometric data discussed
above are consistent with these conformations, with the import-
ant proviso that the preferred conformation may be very
solvent dependent.48 There are two points to note: (i) all the
TTF groups of 12 and 27b are exposed and, therefore, are
available to participate in redox processes: there are no TTF
groups buried within the macromolecular structure; (ii) the
juxtaposition of the TTF groups, enforced by the aryl ester
branch units, does not favour intramolecular interactions;
Experimental
General
Column chromatography was carried out using Merck silica
gel (70–230 mesh) and solvents were distilled prior to use in
column chromatography. All reactions were performed in dry,
distilled solvents under an atmosphere of nitrogen which was
dried by passage through a column of phosphorus pentoxide.
Melting points were recorded on a Reichert-Kofler hot-stage
microscope apparatus and are uncorrected. Solution state
electronic spectra were obtained on a Unicam UV2 instrument.
1H NMR spectra were recorded on Varian Gemini-200, XL-
200, Varian VXR-200 and Varian 400 instruments; chemical
shifts (d) are quoted in ppm, relative to tetramethylsilane as
an internal reference (0 ppm), and coupling constants (J) are
quoted in Hz. Mass spectra were obtained on a VG 7070E
instrument, with ionisation modes as indicated; ammonia was
used as the impingent gas for chemical ionisation mode.
Plasma desorption mass spectrometry was carried out on a
BioIon 10 K time of flight instrument (Biosystems, Uppsala,
Sweden) over 5×105 fissions (252Cf ) at the Department of
Molecular Biology, University of Odense, Denmark. Elemental
analyses were obtained on a Carlo-Erba Strumentazione
instrument. Cyclic voltammetry (CV) and UME CV experi-
ments were performed in a one-compartment cell with platinum
working and counter electrodes: the microelectrodes were
10 mm diameter (from BAS). The reference electrode was
Ag/AgCl. Electrochemical measurements were carried out with
a BAS 100 electrochemical analyser or an EG & G Princeton
Applied Research potentiostat/galvanometer, model no. 273
using iR compensation. The TLCV cell used in this work was
constructed as described previously.39b All solutions were
purged with argon and retained under the inert atmosphere
whilst measurements were carried out.
A Silicon Graphics Indigo workstation, running Biosym
Technologies Insight II (version 2.3.5) molecular modelling
package was used to determine the minimum energy confor-
mation of the compounds. Molecules were built using the
‘Builder’ program, then studied using the ‘Discover’ program.
Initially the molecules were contorted for 10 000 iterations at
a temperature of 750 K. The structure was minimised using
the VA09A minimisation algorithm for 10 000 iterations.
Tris(tetrathiafulvalen-4-ylmethyl) benzene-1,3,5-
tricarboxylate 3
Fig. 2 Energy minimised conformations of (a) compound 12 and (b)
compound 27b. Green=carbon; white=hydrogen; red=oxygen;
yellow=sulfur.
To a solution of alcohol 112,49 (100 mg, 0.43 mmol) in dichloro-
methane (100 cm3) was added compound 2 (34 mg, 0.13 mmol)
1368
J. Mater. Chem., 1998, 8(6), 1361–1372

and triethylamine (0.14 cm3, 1 mmol) and the solution stirred
at 20 °C for 18 h. The solvent was removed in vacuo and
column chromatography of the residue, eluent dichloro-
methane, afforded compound 3 (94 mg, 85%) as an orange
solid, mp 53–54 °C (Analysis found: C, 40.7; H, 2.3;
Bis{3,5-bis[3,5-bis(tetrathiafulvalen-4-ylmethoxycarbonyl)-
phenoxycarbonyl]phenyl} 5-tert-butyldimethylsilyloxy-
benzene-1,3-dicarboxylate 10
To a solution of alcohol 9 (110 mg, 0.08 mmol) in dichloro-
methane (60 cm3) was added compound 4 (13 mg, 0.039 mmol),
DMAP (40 mg, 0.33 mmol) and N,N-dimethylaniline
(0.05 cm3, 0.39 mmol) and the resultant mixture stirred at
35 °C for 54 h. Workup as for compound 3 afforded compound
10 (90 mg, 76%) as an orange oil; m/z (PDMS) 1505.0 (M2+
/2); d [(CD ) CO] 8.62 (1 H, t, J 1.5), 8.56 (2 H, t, J 1.5),
C H O S requires: C, 41.9; H, 2.1%); m/z (PDMS) 859.3
30 18 6 12
(M+); d (CDCl ) 8.85 (3 H, s), 6.45 (3 H, s), 6.29 (6 H, s),
H
3
5.10 (6 H, s).
Bis(tetrathiafulvalen-4-ylmethyl) 5-tert-
butyldimethylsiloxybenzene-1,3-dicarboxylate 5
H
3 2
8.25 (12 H, d, J 1.5), 7.94 (6 H, d, J 1.5), 6.81 (8 H, s), 6.58
(16 H, s), 5.18 (16 H, s), 1.03 (9 H, s), 0.30 (6 H, s).
To a solution of alcohol 1 (100 mg, 0.43 mmol) in dichloro-
methane (50 cm3) was added compound 419 (64 mg, 0.19 mmol)
and triethylamine (0.2 cm3, 1.43 mmol) and the solution stirred
at 20 °C for 18 h. Workup as described for compound 3,
afforded compound 5 (116 mg, 83%) as a yellow solid, mp
Bis{3,5-bis[3,5-bis(tetrathiafulvalen-4-ylmethoxycarbonyl)-
phenoxycarbonyl]phenyl} 5-hydroxybenzene-
1,3-dicarboxylate 11
45–46 °C (Analysis found: C, 45.9; H, 3.9; C H O S Si
To a solution of compound 10 (90 mg, 0.029 mmol) in THF
(60 cm3) was added TBAF (0.2 cm3, 1.1 , 0.22 mmol) and the
solution stirred at 20 °C for 18 h. Workup as described for
28 28 5 8
requires: C, 46.1; H, 3.9%); m/z (PDMS) 729.1 (M+); d
H
[(CD ) CO] 8.26 (1 H, t, J 1.5), 7.74 (2 H, d, J 1.5), 6.84 (2
3 2
compound
3 [eluent dichloromethane–acetone (551 v/v)]
H, s), 6.62 (4 H, s), 5.21 (4 H, s), 1.03, (9 H, s), 0.30 (6 H, s).
afforded compound 11 (42 mg, 50%) as an orange oil; m/z
(PDMS) 2897.6 (M+); d [(CD ) CO] 9.30 (1 H, br s, exch.),
H, s), 5.15 (16 H, s).
Bis(tetrathiafulvalen-4-ylmethyl) 5-hydroxybenzene-1,3-
dicarboxylate 6
H
3 2
8.14 (7 H, t, J 1.5), 7.78 (14 H, d, J 1.5), 6.83 (8 H, s), 6.58 (16
To a solution of compound 5 (5.67 g, 7.78 mmol) in THF
(75 cm3) was added tetrabutylammonium fluoride (TBAF)
(7.5 cm3, 1.1  in THF, 8.25 mmol) and the solution stirred at
20 °C for 18 h. Workup as described for compound 3 afforded
compound 6 (4.1 g, 85%) as a yellow solid, mp 76–77 °C
Tris{3,5-bis[3,5-bis(tetrathiafulvalen-4-ylmethoxycarbonyl)-
phenoxycarbonyl]phenyl} benzene-1,3,5-tricarboxylate 12
To a solution of alcohol 9 (50 mg, 0.036 mmol) in dichloro-
(2.0 mg,
methane (60 cm3) was added compound
2
(Analysis found: C, 43.4; H, 2.7; C H O S requires: C, 43.0;
22 14 5 8
0.0075 mmol), DMAP (30 mg, 0.25 mmol) and N,N-dimethyl-
aniline (0.05 cm3, 0.39 mmol) and the solution stirred at 35 °C
for 54 h. Workup as described for compound 3 [eluent
dichloromethane–acetone (551 v/v)] afforded compound 12
(15 mg, 48%) as an orange oil; m/z (PDMS) 2141.7 (M2+ /2);
H, 2.3%); m/z (PDMS) 614.7 (M+); d [(CD ) CO] 9.24 (1
s), 6.62 (4 H, s), 5.19 (4 H, s).
H
3 2
H, s, exch.), 8.16 (1 H, t, J 1.5), 7.73 (2 H, d, J 1.5), 6.85 (2 H,
Tris[3,5-bis(tetrathiafulvalen-4-ylmethoxycarbonyl)phenyl]
benzene-1,3,5-tricarboxylate 7
d
[(CD ) CO] 8.54 (3 H, s), 8.17 (9 H, t, J 1.5), 7.73 (18 H,
H
3 2
d, J 1.5), 6.84 (12 H, s), 6.61 (24 H, s), 5.19 (24 H, s).
To a solution of alcohol 6 (155 mg, 0.25 mmol) in dichloro-
methane (60 cm3) was added compound 2 (20 mg, 0.075 mmol)
and DMAP (75 mg, 0.61 mmol) and the solution stirred at
20 °C for 18 h. Workup as descibed for compound 3 [eluent
dichloromethane–acetone (551 v/v)] afforded compound 7
(113 mg, 75%) as a yellow solid, mp 80–81 °C; m/z (PDMS)
2000.6 (M+); d [(CD ) SO] 9.10 (3 H, s), 8.44 (3 H, t, J 1.5),
4,5-[2-(Hydroxymethyl)propane-1,3-diyldithio]-1,3-dithiole-2-
thione 15
To a stirred solution of alcohol 1323 (4.51 g, 19.44 mmol) in
acetonitrile (100 cm3) was added zincate salt 1424 (6.97 g,
9.73 mmol) and the mixture was refluxed for 4.5 h to afford
an orange-coloured solution. Workup as described for com-
pound 3 [eluent dichloromethane–acetone (551 v/v)] afforded
compound 15 (4.41 g, 85%) as an orange solid, mp 128–130 °C
(Analysis found: C, 31.6; H, 3.0; C H OS requires: C, 31.3; H,
H
3 2
8.32 (6 H, d, J 1.5), 7.00 (6 H, s), 6.70 (12 H, s), 5.20 (12 H, s).
Bis[3,5-bis(tetrathiafulvalen-4-ylmethoxycarbonyl)phenyl 5-
tert-butyldimethylsilyloxybenzene-1,3-dicarboxylate 8
7
8
5
3.0%); m/z (CI) 269 (M+ +1); d [(CD ) CO] 4.07 (1 H, t, J
H
3 2
5.2, exch.), 3.71 (2 H, m), 3.16 (2 H, m), 2.81 (2 H, m), 2.47 (1
H, m).
To a solution of alcohol 6 (100 mg, 0.16 mmol) in dichloro-
methane (50 cm3) was added compound 4 (24 mg, 0.072 mmol)
and DMAP (70 mg, 0.58 mmol) and the solution stirred at
20 °C for 18 h. Workup as described for compound 3 afforded
compound 8 (91 mg, 76%) as a yellow solid, mp 85–86 °C
4,5-[2-(tert-Butyldiphenylsilyloxymethyl)propane-1,3-
diyldithio]-1,3-dithiole-2-thione 16
To a solution of thione 15 (400 mg, 1.5 mmol) in DMF (80 cm3)
was added tert-butyldiphenylsilyl chloride (830 mg, 3.0 mmol)
and imidazole (1.1 g, 16 mmol) and the mixture stirred at 20 °C
for 18 h. After evaporation in vacuo, the residue was dissolved
in dichloromethane (50 cm3), washed with water (2×50 cm3),
(Analysis found: C, 46.5; H, 2.9; C H O S Si requires: C,
58 44 13 16
46.7; H, 3.2%); m/z (PDMS) 1490.0 (M+); d [(CD ) CO]
H
3 2
8.61 (1 H, t, J 1.5), 8.55 (2 H, t, J 1.5), 8.25 (4 H, d, J 1.5),
7.95 (2 H, d, J 1.5), 6.84 (4 H, s), 6.58 (8 H, s), 5.22 (8 H, s),
1.04 (9 H, s), 0.32 (6 H, s).
dried (MgSO ), filtered and the solvent removed in vacuo.
4
Column chromatography of the residue, eluent dichloro-
methane–hexane (151 v/v) afforded compound 16 (630 mg,
Bis[3,5-bis(tetrathiafulvalen-4-ylmethoxycarbonyl)phenyl 5-
hydroxybenzene-1,3-dicarboxylate 9
84%) as a viscous orange oil; m/z (CI) 507 (M+ +1); d
H
(CDCl ) 7.63 (4 H, m), 7.38 (6 H, m), 3.73 (2 H, d, J 6.1), 2.96
3
To a solution of compound 8 (5.76 g, 3.9 mmol) in THF
(60 cm3) was added TBAF (7 cm3, 1.1  in THF, 7.7 mmol)
and the solution stirred at 20 °C for 18 h. Workup as described
for compound 3 afforded compound 9 as a yellow oil (5.1 g,
95%); m/z (PDMS) 1375.8 (M+); d [(CD ) CO] 9.30 (1 H,
(2 H, m), 2.66 (2 H, m), 2.52 (1 H, m), 1.06 (9 H, s).
4,5-[2-(tert-Butyldiphenylsiloxymethyl )propane-1,3-diyldithio]-
1,3-dithole-2-one 17
H
3 2
br s, exch.), 8.15 (3 H, t, J 1.5), 7.73 (6 H, d, J 1.5), 6.68 (4 H,
To a solution of thione 16 (1.43 g, 2.8 mmol) in chloroform–
glacial acetic acid (100 cm3, 351 v/v) was added mercuric
s), 6.63 (8 H, s), 5.20 (8 H, s).
J. Mater. Chem., 1998, 8(6), 1361–1372
1369

acetate (1.0 g, 3.1 mmol) and the reaction stirred at 20 °C for
18 h. Water (100 cm3) was added and the reaction mixture was
stirred for a further 1 h, after which time the resulting white
precipitate was removed by filtration through a Celite bed.
The organic phase was separated and washed with saturated
aqueous sodium hydrogen carbonate (100 cm3), dried
and the reaction mixture stirred at 20 °C for 18 h. Workup as
described for compound 3 [eluent dichloromethane–acetone
(151 v/v)] afforded compound 23 as an orange solid (59 mg,
66%), mp 238–239 °C (Analysis found: C, 38.8; H, 3.3;
C H O S requires: C, 38.1; H, 3.0%); m/z (PDMS) 1007.6
32 30 5 16
(M+); d [(CD ) SO] 10.18 (1 H, s, exch.), 7.90 (1 H, t, J 1.5),
m), 2.42 (12 H, s).
H
3 2
(MgSO ), filtered and the solvent removed in vacuo to afford
7.61 (2 H, d, J 1.5), 4.45 (4 H, m), 3.11 (2 H, m), 2.72 (8 H,
4
compound 17 (1.22 g, 88%) as a viscous colourless oil; m/z
(CI) 508 (M+NH +); d (CDCl ) 7.64 (4 H, m), 7.39 (6 H,
H, m), 1.06 (9 H, s).
3
H
3
m), 3.73 (2 H, d, J 5.9), 2.93 (2 H, m), 2.62 (2 H, m), 2.46 (1
Tris(3,5-bis{1,3-[4,5-di(methylthio)tetrathiafulvalene-4∞,5∞-
diyldithio]propan-2-ylmethoxycarbonyl}phenyl) benzene-1,3,5-
tricarboxylate 24
4,5-Di(methylthio)-4∞,5∞-[2-(tert-butyldiphenylsiloxymethyl)-
propane-1,3-diyldithio]tetrathiafulvalene 19 and 4,5-di(methyl-
thio)-4∞,5∞-[2-(hydroxymethyl)propane-1,3-diyldithio]tetrathia-
fulvalene 20
To a solution of alcohol 23 (50 mg, 0.05 mmol) in THF
(50 cm3) was added compound 2 (4 mg, 0.015 mmol) and
sodium hydride (30 mg, 1.25 mmol) and the reaction mixture
was then stirred at reflux for 18 h. Workup as described
for compound 3 [eluent dichloromethane–hexane (551 v/v)]
afforded compound 24 (28 mg, 58%) as an orange oil; m/z
(PDMS) 1579.0 (M2+/2); d (CDCl ) 8.73 (3 H, s), 8.25 (3 H,
A stirred suspension of ketone 17 (430 mg, 2.0 mmol) and
ketone 1826 (1.0 g, 2.0 mmol) in triethyl phosphite (5 cm3) was
heated to 130 °C, and the reaction maintained at that tempera-
ture for 2 h, after which time the solution had turned dark red.
Column chromatography of the crude reaction mixture (eluent
hexane) removed triethyl phosphite, then continued elution
with a mixture of dichloromethane–hexane (351 v/v) afforded
an orange oil consisting of an inseparable mixture of the cross-
coupled product 19 and self-coupled products. This mixture
was dissolved in THF (100 cm3), TBAF (2.0 cm3, 1·1  in
THF, 2.2 mmol) was added and the mixture was stirred at
20 °C for 18 h. The solvent was removed in vacuo and column
chromatography of the residue, eluent dichloromethane–ace-
tone (151 v/v) afforded an orange oil which crystallised from
dichlomethane–hexane to yield compound 20 (300 mg, overall
yield 31% from ketone 17) as a yellow solid, mp 128–130 °C
(Analysis found: C, 33.0; H, 3.2; C H OS requires: C, 33.5;
H
3
t, J 1.5), 7.95 (6 H, d, J 1.5), 4.57 (12 H, br s), 2.96 (6 H, m),
2.78–2.66 (24 H, m), 2.40 (36 H, s).
Bis(tetrathiafulvalen-4-ylmethyl) benzene-1,4-dicarboxylate
25a
To a solution of compound 1 (156 mg, 0.67 mmol) in dichloro-
methane (60 cm3) was added terephthaloyl chloride (67 mg,
0.33 mmol) and triethylamine (0.3 cm3, 2.2 mmol) and the
solution stirred at 20 °C for 18 h. Workup as described for
compound
3 [eluent dichloromethane–acetone (551 v/v)]
afforded compound 25a (117 mg, 59%) as a salmon coloured
solid, mp 188–189 °C (Analysis found: C, 44.0; H, 2.2;
C H O S requires: C, 44.1; H, 2.4%); m/z (EI) 599 (M+);
(4 H, s).
12 14
8
22 14 4 8
H, 3.3%); m/z (CI) 431 (M+ +1); d (CDCl ) 3.78 (2 H, d, J
d
[(CD ) SO] 8.14 (4 H, s), 7.01 (2 H, s), 6.75 (4 H, s), 5.19
H
3
H
3 2
6.0), 2.89 (2 H, m), 2.58 (2 H, m), 2.45 (1 H, m), 2.41 (6 H, s),
OH not observed.
Bis(tetrathiafulvalen-4-ylmethyl) biphenyl-4,4∞-dicarboxylate
25b
Tris{1,3-[4-5-di(methylthio)tetrathiafulvalene-4∞,5∞-
diyldithio]propan-2-ylmethyl} benezene-1,3,5-tricarboxylate 21
To a solution of compound 1 (105 mg, 0.45 mmol) in dichloro-
methane (60 cm3) was added biphenyl-4,4∞-dicarbonyl dichlor-
ide (61 mg, 0.22 mmol) and DMAP (220 mg, 1.80 mmol) and
the solution stirred at 20 °C for 48 h. Workup as described for
compound 3 afforded compound 25b (81 mg, 55%) as an
orange solid, mp 219–222 °C (Analysis found: C, 48.1; H, 2.7;
To a solution of alcohol 20 (100 mg, 0.23 mmol) in dichloro-
methane (50 cm3) was added compound 2 (18.5 mg, 0.07 mmol)
and DMAP (59 mg, 0.48 mmol) and the reaction mixture
stirred at 20 °C for 18 h. The solvent was removed in vacuo
and column chromatography of the residue, eluent dichloro-
methane–hexane (551 v/v), afforded compound 21 (66 mg,
57%) as an orange solid, mp 133–135 °C (Analysis found: C,
C H O S requires: C, 47.8; H, 2.7%); m/z (CI) 675 (M+);
28 18 4 8
d [(CD ) SO] 8.06 (4 H, d, J 8.0), 7.91 (4 H, d, J 8.0), 6.97
(2 H, s), 6.71 (4 H, s), 5.16 (4 H, s).
H
3 2
37.3; H, 3.0; C H O S requires: C, 37.3; H, 2.9%); m/z
45 42 6 24
(PDMS) 1448.4 (M+); d (CDCl ) 8.78 (3 H, s), 4.57 (6 H, br
H
3
s), 2.96 (6 H, m), 2.78–2.66 (9 H, m), 2.40 (18 H, s).
Bis(tetrathiafulvalen-4-ylmethyl) 4,4∞-oxybis(benzene-
carboxylate) 25c
Bis{1,3-[4-5-di(methylthio)tetrathiafulvalene-4∞,5∞-
diyldithio]propan-2-ylmethyl} 5-tert-butyldimethylsilyloxy-
benzene-1,3-dicarboxylate 22
To a solution of alcohol 1 (105 mg, 0.45 mmol) in dichloro-
methane (60 cm3) was added 4,4∞-oxybis(benzenecarbonyl
chloride) (66 mg, 0.22 mmol) and DMAP (110 mg, 0.9 mmol)
and the solution stirred at 20 °C for 18 h. Workup as described
for compound 3 [eluent dichloromethane–acetone (551 v/v)]
afforded compound 25c (130 mg, 84%) as a yellow solid, mp
To a solution of alcohol 20 (110 mg, 0.26 mmol) in dichloro-
methane (50 cm3) was added compound 4 (39 mg, 0.12 mmol)
and DMAP (59 mg, 0.48 mmol) and the reaction mixture
stirred at 20 °C for 18 h. Workup as described for compound
3 afforded compound 22 (126 mg, 96%) as an orange solid,
154–156 °C (Analysis found: C 48.9; H, 2.6; C H O S
28 18 5 8
requires: C, 48.7; H, 2.6%); m/z (DCI) 691 (M+);
H, s), 6.59 (4 H, s), 5.13 (4 H, s).
d
[(CD ) CO] 8.04 (4 H, d, J 9.0), 7.17 (4 H, d, J 9.0), 6.80 (2
mp 66–67 °C (Analysis found: C, 41.3; H, 4.2; C H O S Si
H
38 44 5 16
requires: C, 40.7; H, 4.0%); m/z (PDMS) 1120.9 (M+); d
3 2
H
(CDCl ) 8.15 (1 H, t, J 1.5), 7.65 (2 H, d, J 1.5), 4.50 (4 H, br
3
s), 2.90 (2 H, m), 2.75 (8 H, m), 2.40 (12 H, s), 1.03 (9 H, s),
Bis[3,5-bis(tetrathiafulvalen-4-ylmethoxycarbonyl)phenyl]
benzene-1,4-dicarboxylate 26a
0.25 (6 H, s).
Bis{1,3-[4-5-di(methylthio)tetrathiafulvalene-4∞,5∞-
diyldithio]propan-2-ylmethyl} 5-hydroxybenzene-1,3-
dicarboxylate 23
To a solution of compound 4 (100 mg, 0.16 mmol) in dichloro-
methane (60 cm3) was added terephthaloyl choride (16 mg,
0.08 mmol) and DMAP (40 mg, 0.32 mmol) and the solution
stirred at 20 °C for 18 h. Workup as described for compound
3 [eluent dichloromethane–acetone (551 v/v)] afforded com-
To a solution of compound 22 (100 mg, 0.09 mmol) in THF
(50 cm3) was added TBAF (0.2 cm3, 1.1  in THF, 0.22 mmol)
1370
J. Mater. Chem., 1998, 8(6), 1361–1372

pound 26a (117 mg, 59%) as a salmon coloured solid, mp
113–114 °C (Analysis found: C, 46.1; H, 2.3; C H O S
Bis{3,5-bis[3,5-bis(tetrathiafulvalen-4-ylmethoxycarbonyl)-
phenoxycarbonyl]phenyl} 4,4∞-oxydibenzoate 27c
52 30 12 16
requires: C, 45.9; H, 2.2%); m/z (PDMS) 1359.7 (M+); d
H
[(CD ) SO] 8.59 (2 H, t, J 1.5), 8.28 (4 H, d, J 1.5), 8.12 (4
3 2
To a solution of compound 9 (108 mg, 0.078 mmol) in dichloro-
methane (60 cm3) was added 4,4∞-oxybis(benzenecarbonyl
chloride) (10.9 mg, 0.037 mmol), DMAP (190 mg, 1.56 mmol)
and N,N-dimethylaniline (0.2 cm3, 1.56 mmol) and the solution
stirred at 35 °C for 72 h. Workup as described for compound
27b [eluent dichloromethane–acetone (551 v/v)] afforded com-
pound 27c (18 mg, 16%) as an orange oil; m/z (PDMS) 2971.1
(M+); d [(CD ) CO] 8.57 (4 H, t, J 1.5), 8.29 (4 H, d, J 9.0),
H, s), 6.89 (4 H, s), 6.65 (8 H, s), 5.24 (8 H, s).
Bis[3,5-bis(tetrathiafulvalen-4-ylmethoxycarbonyl)phenyl]
biphenyl-4,4∞-dicarboxylate 26b
To a solution of compound 4 (100 mg, 0.16 mmol) in dichloro-
methane (60 cm3) was added biphenyl-4-4∞-dicarbonyl dichlor-
ide (22 mg, 0.08 mmol) and DMAP (156 mg, 1.28 mmol) and
the solution stirred at 20 °C for 18 h. The solution was filtered
and the residue washed sequentially with water (25 cm3),
dichloromethane (50 cm3), isopropyl alcohol (25 cm3) and
diethyl ether (50 cm3) to afford compound 26b (94 mg, 83%)
as an orange solid, mp >250 °C (Analysis found: C, 48.7; H,
H
3 2
8.24 (8 H, d, J 1.5), 8.14 (2 H, t, J 1.5), 7.72 (4 H, d, J 1.5),
7.30 (4 H, d, J 9.0), 6.88 (8 H, s), 6.62 (16 H, s), 5.24 (16 H, s).
Tetrathiafulvalen-4-ylmethyl benzoate 28
To a solution of compound 112 (500 mg, 2.14 mmol) in
dichloromethane (50 cm3) was added benzoyl chloride
(0.25 cm3, 2.18 mmol) and triethylamine (1 cm3, excess) and
the solution stirred at 20 °C for 12 h. After evaporation of the
solvent, the residue was chromatographed, eluting with
hexane–dichloromethane (151 v/v) to afford compound 28
(665 mg, 92%) as a yellow solid, mp 68 °C (Analysis found: C,
2.5; C H O S requires: C, 48.5; H, 2.4%); m/z (PDMS)
58 34 12 16
1435.8 (M+); d [(CD ) SO] 8.57 (2 H, t, J 1.5), 8.29 (4 H, d,
6.72 (8 H, s), 5.21 (8 H, s).
H
3 2
J 8.8), 8.24 (4 H, d, J 1.5), 8.03 (4 H, d, J 8.8), 7.01 (4 H, s),
49.8; H, 3.1; C H O S requires: C, 49.7; H, 3.0%); m/z (DCI)
14 10 2 4
Bis[3,5-bis(tetrathiafulvalen-4-ylmethoxycarbonyl)phenyl]
4,4∞-oxydibenzoate 26c
339(M+ +1); d (CDCl ) 8.05 (2 H, d, J 7.8), 7.56 (1 H, t, J
H
3
7.0), 7.44 (2 H, m), 6.40 (1 H, s), 6.21 (2 H, s), 5.05 (2 H, s).
To a solution of compound 4 (75 mg, 0.12 mmol) in dichloro-
methane (60 cm3) was added 4,4’-oxybis(benzenecarbonyl
chloride) (17 mg, 0.06 mmol) and DMAP (117 mg, 0.96 mmol)
and the solution stirred under nitrogen at 20 °C for 18 h.
Workup as described for compound 3 afforded compound 26c
(43 mg, 52%) as an orange solid, mp 110–112 °C (Analysis
We thank the EPSRC for funding this work, and the British
Council for Alliance grant 94.028 which funded a visit by
W. D. to Universite´ d’Angers. We thank M. Salle´ and M.
Jubault for assistance with electrochemical experiments in
Angers.
found: C, 47.9; H, 2.4; C H O S requires C, 48.0; H, 2.4%);
58 34 13 16
References
m/z (PDMS) 1451.7 (M+); d [(CD ) CO] 8.57 (2 H, t, J 1.5),
6.88 (4 H, s), 6.62 (8 H, s), 5.25 (8 H, s).
H
3 2
8.30 (4 H, d, J 8.2), 8.24 (4 H, d, J 1.5), 7.32 (4 H, d, J 8.2),
1
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5
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(Analysis found: C, 46.1; H, 2.3; C H O S requires: C,
112 62 28 32
46.7; H, 2.2%; m/z (PDMS) 1440.8 (M2+/ 2); d [(CD ) CO]
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H
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8.59 (6 H, t, J 1.5), 8.27 (12 H, d, J 1.5), 8.23 (4 H, s), 6.88 (8
6
Bis{3,5-bis[3,5-bis(tetrathiafulvalen-4-ylmethoxycarbonyl)-
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7
8
(a) V. Percec, P. Chu and M. Kawasumi, Macromolecules, 1994, 27,
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¨
¨
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9
dried (MgSO ). The solvent was removed in vacuo and column
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H
3 2
H, t, J 1.5), 8.29 (4 H, d, J 1.5), 8.14 (4 H, t, J 1.5), 8.02 (8 H,
d, J 1.5), 7.80 (4 H, d, J 7.0), 7.77 (4 H, d, J 7.0), 6.85 (8 H,
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Paper 8/00225H; Received 7th January 1998
1372
J. Mater. Chem., 1998, 8(6), 1361–1372