Geometrically constrained tetrathiafulvalenophanes: Synthesis and characterization

Article abstract of DOI:10.1021/jo970326z

The synthesis of tetrathiafulvalenophanes 4b, 4c, 5, 9, and 10 employing two fundamentally different strategies is reported. Macrocycle 9 was obtained as a mixture of cis and trans isomers and was crystallized to afford two distinct crystals types: a red type consisting of the cis isomer and a yellow type consisting of the trans isomer. The crystal structures of cis-9 and trans-9, determined by X-ray diffraction, revealed that the cis-form possesses a planar TTF moiety while the trans-form has a distorted TTF unit. The electrochemical properties of the new tetrathiafulvalenophanes are reported.

Full text of DOI:10.1021/jo970326z

4936
J . Org. Chem. 1997, 62, 4936-4942
Geom etr ica lly Con str a in ed Tetr a th ia fu lva len op h a n es: Syn th esis
a n d Ch a r a cter iza tion
J esper Lau,†,§ Philippe Blanchard,†,‡ Ame´de´e Riou,‡ Michel J ubault,‡ Michael P. Cava,§ and
J an Becher*,†
Department of Chemistry, Odense University, Campusvej 55, DK-5230, Odense M, Denmark,
IMMO, CNRS, EP 66, Universite´ d'Angers, 49045 Angers, France, and Department of Chemistry,
The University of Alabama, P.O. Box 870336, Tuscaloosa, Alabama 35487-0336
Received February 19, 1997
The synthesis of tetrathiafulvalenophanes 4b, 4c, 5, 9, and 10 employing two fundamentally
different strategies is reported. Macrocycle 9 was obtained as a mixture of cis and trans isomers
and was crystallized to afford two distinct crystals types: a red type consisting of the cis isomer
and a yellow type consisting of the trans isomer. The crystal structures of cis-9 and trans-9,
determined by X-ray diffraction, revealed that the cis-form possesses a planar TTF moiety while
the trans-form has a distorted TTF unit. The electrochemical properties of the new tetrathiaful-
valenophanes are reported.
Cyclophanes are fundamentally important compounds
i.e. two,5b three,5b four,5i or five5d,h atoms gives intermo-
lecular coupling whereas longer spacers5a,d,f,g,l tends to
give intramolecular reaction. An interesting class of
redox active macrocycles are the sandwich type bis-TTF
macrocycles. However the easily obtainable bis-TTF
derivatives of this type are those with short linkers (two
to five atoms). The resulting short distance between the
two TTF moieties makes it a poor candidate for donor-
acceptor based host-quest chemistry. We have revisited
the triethyl phosphite coupling of some bis-trithiocar-
bonates in the hope of gaining more information of the
linkers influence on the course of the reaction.
We have previously described a versatile new meth-
odology6 using preformed TTF derivatives as building
blocks for the modular syntheses of macrocyclic com-
pounds.7 In the present work we extend this approach
to complement the original strategy where the TTF
moiety is formed in the cyclization step. We report the
syntheses of TTF building block 8a as well as full
experimental details for 8b. Various new tetrathiaful-
valenophanes were prepared employing the two different
strategies. The synthesis and electrochemical properties
of these new electroactive cyclophanes, as well as an
X-ray crystallographic study of the two isomers of 9 will
be discussed. The isolation and characterization of the
pure cis and trans isomers of 9 represents a particularly
novel result of this study.
in many aspects of macrocyclic and supramolecular
chemistry, and research in this field has expanded
rapidly in recent years.1,2 Several interesting systems,
like catenanes and rotaxanes, have been prepared based
on self assembling of complementary electroactive units.3
Tetrathiafulvalene (TTF) is a stable and reversible elec-
tron donor;4 hence, the incorporation of TTF units into
cyclophanes may be expected to give interesting electro-
active macrocycles. Indeed a number of such tetrathia-
fulvalenophanes are known,5a-l all of which were pre-
pared by coupling reactions in which a TTF moiety is
formed in the final cyclization step. The course of these
reactions, giving either inter- or intramolecular cycliza-
tion, seems to be controlled solely by the length of the
linker between the two dithiole units. Very short linkers
† Odense University.
‡ Universite´ d’Angers.
§ The University of Alabama.
X Abstract published in Advance ACS Abstracts, J une 15, 1997.
(1) (a) Vo¨gtle, F., Ed. Cyclophanes I. Topics in Current Chemistry;
Springer: Berlin, 1983; Vol. 113. (b) Vo¨gtle, F., Ed. Cyclophanes II.
Topics in Current Chemistry; Springer: Berlin, 1983; Vol. 115. (c)
Vo¨gtle, F. Cyclophane Chemistry; Wiley: Chichester, 1993.
(2) Diederich, F. Cyclophanes. Monographs in Supramolecular
Chemistry; Fraser Stoddart, J ., Ed.; The Royal Society of Chemistry:
London, 1991.
(3) Amabilino, D. B.; Stoddart, J . F. Chem. Rev. 1995, 95, 2725-
2828.
(4) Reviews on TTF chemistry: (a) Narita, M.; Pittman, C. U.
Synthesis 1976, 489. (b) Schukat, G.; Richter, A. M.; Fangha¨nel, E.
Sulphur Rep. 1987, 7, 155. (c) Schukat, G.; Fangha¨nel, E. Sulphur
Rep. 1993, 14, 245. (d) J ørgensen, T.; Hansen, T. K.; Becher. J . J . Chem.
Soc. Rev. 1994, 41. (e) Adam, M.; Mu¨llen, K. Adv. Mater. 1994, 6, 439.
(5) (a) Staab, H. A.; Ippen, J .; Tao-pen, C.; Krieger, C.; Starker, B.
Angew. Chem., Int. Ed. Engl. 1980, 19, 66. (b) Ippen, J .; Tao-Pen, C.;
Schweitzer, D.; Staab, H. A. Angew. Chem., Int. Ed. Engl. 1980, 19,
67. (c) Ro¨hrich, J .; Wolf, P.; Enkelmann, V.; Mu¨llen, K. Angew. Chem.
1988, 100, 1429. (d) Bertho-Thoraval, A.; Robert, A.; Souizi, A.;
Boubekeur, K.; Batail, P. J . Chem. Soc., Chem. Commun. 1991, 843.
(e) Hascoat, P.; Lorcy, D.; Robert, A.; Boubekeur, K.; Batail, P.; Carlier,
R.; Tallec, A. J . Chem. Soc., Chem. Commun. 1995, 1229. (f) Hansen,
T. K.; J ørgensen, T.; J ensen, F.; Thygesen, P. H.; Christiansen, K.;
Hursthouse, M. B.; Harman, M. E.; Malik, M. A.; Girmay, B.;
Underhill, A. E.; Begtrup, M.; Kilburn, J . D.; Belmore, K.; Roepstorff,
P.; Becher, J . J . Org. Chem. 1993, 58, 1359. (g) Girmay, B.; Kilburn,
J . D.; Underhill, A. E.; Varma, K. S.; Hursthouse, M. B.; Harman, M.
E.; Becher, J .; Bojesen, G. J . Chem. Soc., Chem. Commun. 1989, 1406.
(h) Matsuo, K.; Takimiya, K.; Aso, Y.; Otsubo, T.; Ogura, F. Chem.
Lett. 1995, 523. (i) Takimiya, K.; Aso, Y.; Ogura, F.; Otsubo, T. Chem.
Lett. 1995, 735. (j) Tanabe, J .; Kudo T.; Okamoto, M.; Kawada, Y.; Ono,
G.; Izuoka, A.; Sugawara, T. Chem. Lett. 1995, 579. (k) Takimiya, K.;
Shibata, Y.; Imamura, K.; Kashihara, A.; Aso, Y. Otsubo, T.; Ogura,
F. Tetrahedron. Lett. 1995, 36, 5045. (l) Boubekeur, K.; Lenoir, C.;
Batail, P.; Carlier, R.; Tallec, A.; LePaillard, M.-P.; Lorcy, D.; Robert,
A. Angew. Chem., Int. Ed. Engl. 1994, 33, 1379.
Resu lts a n d Discu ssion
The necessary cesium 1,3-dithiole-2-thione-5-thiolate
1 was obtained by the recently reported procedure.6c,8
Alkylation of 1 proceeds cleanly and in excellent yield,
and alkylation with either R,R′-dibromo-, o-, m- or p-
xylene afforded the bis-1,3-dithiole-2-thiones 2a -c in
(6) (a) Svenstrup, N.; Rasmussen, K. M.; Hansen, T. K.; Becher, J .
Synthesis 1994, 809. (b) Becher, J .; Lau, J .; Leriche, P.; Mørk, P.;
Svenstrup, N. J . Chem. Soc., Chem. Commun. 1994, 2715. (c) Lau, J .;
Simonsen, O.; Becher, J . Synthesis 1995, 521. (d) Simonsen, K. B.;
Svenstrup, N.; Lau, J .; Simonsen, O.; Mørk, P.; Kristensen, G. J .;
Becher, J . Synthesis 1996, 407.
(7) (a) Li, Z.-T.; Stein, P. C.; Svenstrup, N.; Lund K. H.; Becher, J .
Angew. Chem., Int. Ed. Engl. 1995, 34, 2524. (b) Blanchard, P.;
Svenstrup, N.; Becher, J . J . Chem. Soc., Chem. Commun. 1996, 615.
(c) Li, Z.-T.; Becher, J . J . Chem. Soc., Chem. Commun. 1996, 639.
(8) (a) Sudmale, I. V.; Tormos, G. V.; Khodorkovsky, V. Y.; Edzina,
A. S.; Neilands, O. J .; Cava, M. P. J . Org. Chem. 1993, 58, 1355. (b)
Augustin, M.; Do¨lling, W.; Vogt, A. Z. Chem. 1983, 23, 333.
S0022-3263(97)00326-5 CCC: $14.00 © 1997 American Chemical Society

Geometrically Constrained Tetrathiafulvalenophanes
J . Org. Chem., Vol. 62, No. 15, 1997 4937
Ta ble 1. UV-vis Da ta (CH2Cl2)
Sch em e 1
compd
δmax/nm (log ꢀ)
4b
327(4.08), 414(3.53)
4c
321(4.01), 424(3.32)
5
324(3.81)
cis-9
trans-9
10
236(4.29), 316(4.03), 404(3.28)
232(4.37), 264(4.17), 336(4.26), 370(3.49)
228(4.80), 332(4.44), 379(3.79)
Sch em e 3
Sch em e 2
o-xylylene analog, the linker gets shorter. In this ap-
proach, shortening of the linker to disfavor intramolecu-
lar reaction and hence favor intermolecular reaction does
not afford the bis-TTF product.
1
Due to hindered rotation of the phenylene group, H-
NMR of the p-cyclophane 4c shows two different aromatic
protons Ha and Hb, indicating that the macrocycle in
solution has a conformation in which part of the phenyl
ring is situated over the TTF moiety.5d Ha appears as a
mutiplet consisting of three signals between 7.480 and
7.485 ppm each separated by approximately 1 Hz. Hb
likewise consists of three signals between 6.753 and 6.760
ppm each separated by 1 Hz. The multiplets are prob-
ably two unresolved doublet of doublets. Since the two
Ha protons would be nonequivalent in a trans-isomer an
ortho-coupling of typically 6-10 Hz would be expected
for this isomer. The absence of such an ortho-coupling
therefore indicates that the stereoisomer present is the
cis-structure. Analogous results were obtained with the
parent compound 5. In the case of the corresponding
m-cyclophane 4b no upfield shift of the aromatic protons
is observed. In all cases an AB-spin system was observed
for the CH2 protons with a geminal coupling J ) 12.0
Hz.
almost quantitative yields. Subsequent transchalcoge-
nation yielded the corresponding bis-1,3-dithiole-2-ones
3a -c (Scheme 1).
Triethyl phosphite treatment of 3a gave an intractable
solid. Plasma desorption mass spectrometry (PDMS)
investigation of the crude material revealed a complex
mixture of products. The same result was obtained in
the cases of 3b and 3c using neat triethyl phosphite.
However, an excess of triethyl phosphite in refluxing
toluene resulted in fair yields of the m- and p- cyclo-
tetrathiafulvalenophanes 4b and 4c (43% and 48%,
Scheme 2). In order to obtain the unsubstituted TTF
compound, diester 4c was hydrolyzed to the dicarboxylic
acid. Decarboxylation was achieved by heating the
intermediate diacid in diglyme to give 5. Hydrolysis and
decarboxylation proceeded in an overall yield of 58%.
Attempts to decarboxylate the meta-analog failed. It
must be noted that the phosphite coupling of the present
1,3-dithiole-2-ones 3b and 3c yields exclusively the
intramolecular coupled tetrathiafulvalenophanes. PDMS
revealed that no intermolecular coupling of 3a -c leading
to bis-TTF macrocycles is taking place. CPK-models
indicate that the new TTF-phanes 4b, 4c, and 5 are very
compact molecules. In fact a CPK-model of neither
metacyclophane 4b nor of the corresponding orthocyclo-
phane can be constructed due to the tremendous strain
in the structure. On going from the p- to the m- to the
The m-cyclophane 4b is less colored than the p-
cyclophane 4c; indeed, λmax for 4b is 414 nm whereas λmax
for 4c is 424 nm (Table 1). This indicates that the
m-cyclophane has a more distorted TTF group that allows
for less π-delocalization.
The building blocks 8a and 8b were prepared according
to Scheme 3. The 1,3-dithiole-2-thiones 6a and 6b were
treated with mercuric acetate to give the corresponding
oxo compounds 7a and 7b. Triethyl phosphite treatment
of these afforded the key TTF derivatives 8a and 8b in
72% and 70% yields, respectively. 8b was treated with
2.2 equiv of cesium hydroxide in methanol to generate
the TTF bis-thiolate (Scheme 4). This was reacted with
bis[4-(bromomethyl)phenyl]methane under high dilution
conditions, using a medical perfusor pump. Chromatog-
raphy afforded 9 as an orange powder in 71% yield. No
trace of the dimeric product 10 was detected in PDMS.
The high yield and selectivity in this reaction is probably
due to the almost perfect geometrical complementarity
of the TTF bis-thiolate and the bis-bromo reagent and it
nicely demonstrates the efficiency of the overall strategy.

4938 J . Org. Chem., Vol. 62, No. 15, 1997
Lau et al.
Sch em e 4
1H-NMR (CDCl3 stored over K2CO3)9 of 9 revealed the
presence of two configurational isomers, as evidenced by
two well resolved singlets for the methylthio groups at
2.26 and 2.44 ppm, with the ratio of integration of 3:2,
respectively. Separation of the different isomers by
column chromatography was not possible. However,
crystallization from a mixture of CH2Cl2-hexane afforded
a mixture of two different crystal types: red shiny
needles and yellow plates. The crystals were easily
separated from each other simply by mechanical sorting.
The two different types of colored crystals thus obtained
exhibited identical mass and IR spectra. The red crystals
melted at 192-194 °C whereas the yellow crystals melted
at 210-212 °C. 1H-NMR (CDCl3 over K2CO3) of the red
crystals showed a singlet at δ ) 2.44 ppm due to the
methylthio groups, one singlet at δ ) 3.86 ppm from the
two different methylene protons (ArCH2Ar and ArCH2S),
and two doublets from the para-substituted aromatic
system.
On cooling below -30 °C, the methylene signal splits
into two signals. In the case of the yellow compound the
1H-NMR spectrum clearly corresponds to a more rigid
system, since an AB spin system arises from the geminal
methylenethio protons (δ ) 3.84 and 4.09 ppm, J ) 13.3
Hz), equivalent to the case of 4b, 4c, and 5. No cis-
trans isomerization was observed in the CDCl3 (previ-
ously stored over K2CO3) solutions of compounds cis-9
and trans-9; however, addition of an excess of CF3COOD
to solutions of each isomer leads to a darkening of the
from different configurational isomers. In contrast to
mono-TTF 9, the isomers of bis-TTF 10 could not be
separated by neither chromatography nor crystallization.
All the new tetrathiafulvalenophanes were investi-
gated by PDMS to confirm their purity.
1
X-r a y An a lysis.13 X-ray diffraction analysis (Figure
1) revealed that the trans-9 isomer (yellow) is more
strained than the corresponding cis-9 isomer (red) since
the cis isomer has a planar TTF framework, whereas the
dithiole moieties are distorted out of planarity in the
trans isomer. The central tetrathioethylene medium
plane of trans-9 and the two external dithioethylene
medium planes of the TTF moiety formed two different
angles of 28° and 16°, indicating that the TTF core is
much less distorted compared to the recently described
[8]tetrathiafulvalenophane5d,11 in which the correspond-
ing angles of 47° and 34° were observed. Furthermore,
the central fulvalenic bond is significantly shorter in the
trans isomer (1.309(5) Å) than in the cis isomer (1.332-
(8) Å). Thus, the better conjugation of the planar TTF
in cis-9 nicely explained the color difference between the
two configurational isomers. The UV-visible spectrum
(Table 1) in dichloromethane of the cis isomer exhibited
a lower energy absorption band (λmax ) 404 nm) than did
solutions showing identical H NMR spectra with broad-
ening of signals characteristic of the presence of cation
1
radicals in solution.10 The H NMR spectrum of a crude
reaction product of compound 9 revealed an initial 40/
60 mixture of cis/ trans isomers.
The corresponding macrocycle bis-TTF 10 could be
prepared via a stepwise reaction sequence: (i) a thiolate
monodeprotection of 8b using 1.1 equiv of cesium hy-
droxide, followed by alkylation with bis[4-(bromometh-
yl)phenyl]methane (0.48 equiv) gave 11 in 54% yield; (ii)
subsequent deprotection of the two remaining thiolate
functions, followed by ring closure reaction under high
dilution conditions in the presence of bis[4-(bromometh-
yl)phenyl]methane (1 equiv), afforded bis-TTF 10 as an
orange-brown powder 55% yield (Scheme 4). 10 shows
three different methylthio protons in the 1H-NMR arising
(9) To avoid the slow cis/trans isomerization observed in commercial
CDCl3, due to the presence of traces of acid, see Souizi, A.; Robert, A.;
Batail, P.; Ouahab, L. J . Org. Chem. 1987, 52, 1610.
(10) Giffard, M.; Alonso, P.; Garin, A.; Gorgoues, A.; Nguyen, T. P.;
Richomme, P.; Robert, A.; Roncali, J .; Uriel, S. Adv. Mater. 1994, 6,
298.
(11) Boubekeur, K.; Batail, P.; Bertho-Thoraval, F.; Robert, A. Acta
Crystallogr. Sect. C 1991, 47, 1109.

Geometrically Constrained Tetrathiafulvalenophanes
J . Org. Chem., Vol. 62, No. 15, 1997 4939
F igu r e 2. Cyclic voltammograms of cis-9 (a) and trans-9 (b).
Sch em e 5
F igu r e 1. Crystal structures of cis-9 (top) and trans-9
(bottom).
scan, cis-9 revealed two reversible one-electron oxidation
peaks at 0.44 and 0.88 V accompanied with a small
shoulder A at 0.53 V.
Ta ble 2. Cyclic Volta m m etr y Da ta a
compd (solvent)
Eox or E1/2 (V)
1
2
TTF (MeCN)
4b (MeCN)
4c (MeCN)
5 (CH2Cl2)
8a (MeCN)
8b (CH2Cl2)
cis-9 (CH2Cl2)
trans-9 (CH2Cl2)
10 (CH2Cl2)
11 (CH2Cl2)
E1/2 ) 0.32, E1/2 ) 0.73
Eox ) 1.05 (irr)
The corresponding trans-9 isomer showed two one-
electron redox processes at 0.53 and 0.88 V during the
first scan, the first one being quasireversible (Epa-Epc
) 0.185 V) and the second being truly reversible at
potentials identical to those of cis-9. These results
indicated that after the electrochemical oxidation of cis-9
(Scheme 5, eq 1), the resulting cis-9+‚ cation radical was
subject to rapid chemical isomerization to the trans-9+‚
species (eq 2) which was reduced to the neutral trans-9
by diffusing of the cis-9 isomer, according to the ther-
+‚
Eox ) 1.00 (irr)
Eox ) 0.81 (irr)
1
2
E1/2 ) 0.71, E1/2 ) 1.05
1 2
E1/2 ) 0.65, E1/2 ) 1.01
1 2
E1/2 ) 0.39, E1/2 ) 0.83
1
2
E1/2 ) 0.44, E1/2 ) 0.83
1
2
E1/2 ) 0.49, E1/2 ) 0.87
1
2
E1/2 ) 0.54, E1/2 ) 0.89
a
NBu4PF6, Ag/AgCl, platinum electrode, scan speed: 100 mV
s-1
.
+‚/trans
modynamically allowed (E°trans
> Ecis /cis) redox
reaction (eq 3). Then the small amount of the resulting
trans isomer was oxidized at 0.53 V (eq 4), giving rise to
the small shoulder A observed in the first scan in the
voltammogram of cis-9. This ECE mechanism (ECE )
electron transfer with subsequent chemical reaction and
further electron transfer) was seen to be independent of
the scan rates since the shoulder A was always present
between 200 and 10 mV s-1 (Figure 3a).
In the case of compound trans-9, a rapid chemical
isomerization of trans-9+‚ to cis-9+‚ was also observed
after the first electron transfer since a new well-resolved
oxidation wave B appeared at 0.44 V during the second
scan (Figure 2b). Therefore, the electrochemical behavior
can be explained as followed: at the first scan, trans-9
was oxidized to trans-9+‚ , which then isomerized to cis-
9+‚, these two species being in rapid chemical equilibrium
(Scheme 5, eq 2). In the reverse scan, trans-9+‚ and cis-
9+‚ were reduced to trans-9 and cis-9, the presence of the
latter being proved by its oxidation peak (0.44 V) at the
second scan. The additional wave B can be suppressed
by lowering the scan rate to 20 mV s-1 due to the
diffusion of the electrochemically formed cis isomer from
the trans isomer (λmax ) 370 nm). Note that in the solid
state, the benzene rings of each isomer adapt two
different conformations which were not observed in a
CDCl3 solution on the NMR timescale at room temper-
ature.
Cyclic Volta m m etr y. Cyclic voltammetry of the new
cyclophanes shows that 4b, 4c, and 5 are irreversibly
oxidized. Table 2 shows that the m-cyclophane 4b has a
slightly higher oxidation potential (1.05 V) than the
p-cyclophane 4c (1.00 V). According to previous results,5f
the higher potential indicates that the the m-cyclophane
has a more bent TTF unit. The oxidation potential of 5
(0.81 V) is lowered about 200 mV compared to that of
4c, which is consistent with the disappearance of the
electron withdrawing effect of the ester groups.
The cyclophanes 9 and 10 with the larger spacer
groups are reversible donors, as well as all the noncyclic
TTF derivatives 8a , 8b, 11 (Table 2). The electrochemical
properties of cis-9 and trans-9 are somewhat different.
The cyclic voltammograms of cis-9 and trans-9 showed
two different behaviors (Figure 2, parts a and b, respec-
tively). At a scan rate of 100 mV s-1, during the first

4940 J . Org. Chem., Vol. 62, No. 15, 1997
Lau et al.
possible interaction between the radical cation and the
π-system in the diphenylmethane moiety resulting in a
stabilization of the radical cation.
Con clu sion
It can be concluded that the synthetic method, using
triethyl phosphite as a coupling agent for the xylylene-
dithio-bis-1,3-dithiol-2-ones described here, gives rise
exclusively to intramolecular coupled cyclophanes in good
yields. Decreasing the length of the spacer on going from
the para to the ortho analog does not favor intermolecular
cyclization as reported from other systems. Apparently
the length of the linker as well as its geometry have a
profound influence on the course of this type of coupling
reaction. Therefore, a general method for preparing
tetrathiafulvalenophanes with more than one TTF moiety
requires a strategy involving a preformed TTF building
block. In this work, we have demonstrated that the use
of cyanoethyl-protected TTF-thiolate is efficient for the
preparation of cyclophanes containing either one or two
TTF units. An electrochemical cis/ trans isomerization
of 9 was observed starting either from the cis or from
the trans isomer. A cyclic voltammetry study of 9 at
different scan rates allowed a better understanding of
chemical reactions coupled with redox processes.
Exp er im en ta l Section
Gen er a l.12 X-ray structures were determined with an
Enraf-Nonius MACH3 four circles diffractometer. Crystal data
for cis-9: C23H20S8, M ) 552.89, red needles, monoclinic P21/
c, a ) 5.923(6), b ) 17.559(11), c ) 23.972(12) Å, â ) 94.59-
(5)°, V ) 2485(2) Å3, Z ) 4, Fcalc ) 1.478 g cm-3, λ(Mo KR) )
0.71073 Å, 7744 reflections (2 < θ < 30°) were collected at 298
K, 2280 reflections with I > 3σ(I) were used in the refinements,
280 refined parameters, R ) 0.056, Rw ) 0.063.
Crystal data for trans-9: C23H20S8, M ) 552.89, yellow
plates, triclinic P1h, a ) 8.308(12), b ) 10.121(7), c ) 16.138-
(10) Å, R ) 76.90(5), â ) 84.39(8), γ ) 73.71(7)°, V ) 1268(1)
Å3, Z ) 2, Fcalc ) 1.448 g cm-3, λ(Mo KR) ) 0.71073 Å, 7354
reflections (2 < θ < 30°) were collected at 298 K, 4452
reflections with I > 3σ(I) were used in the refinements, 280
refined parameters, R ) 0.079, Rw ) 0.096.
Cyclic voltammetry was carried out at room temperature
with platinum working (0.785 mm2 surface) and counter
electrodes and a standard calomel electrode (SCE) or a Ag/
AgCl as reference: 10-3 mol L-1 of TTF derivatives in a
solution of Bu4NPF6 (10-1 mol L-1) in CH2Cl2 or MeCN
(purified through basic alumina), scan rate 100 m V s-1 unless
otherwise stated.
4,4′-(Xylylen ed ith io)bis(5-ca r bom eth oxy-1,3-d ith iole-
2-t h ion es) (2a -c). Gen er a l P r oced u r e. To a stirred
suspension of 1 (1.96 g, 5.50 mmol) in degassed acetone (25
mL) was added dibromoxylene (0.66 g, 2.50 mmol) in one lot.
The reaction mixture was stirred at room temperature under
N2 for 45 min. The precipitate was filtered off, washed with
2 × 50 mL water, and dried in air. The products were all pure
for practical use (NMR and TLC).
F igu r e 3. (a) Successive cyclic voltammograms of cis-9 (5 ×
10-4 mol L-1) between 0 and 0.72 V vs scan rates: 10, 50, 100,
200 mV s-1. (b) Cyclic voltammograms of trans-9 (10-3 mol
L-1) between 0 and 0.70 V: first and second scan at different
scan rates.
2a : 1.30 g, 95%. Yellow crystals, mp 203-204 °C (toluene).
IR (KBr) (cm-1) 1703, 1482, 1257, 1072. MS: m/ z 550 (M+,
31), 327 (16), 238 (23), 191 (100). 1H-NMR (CDCl3) δ 7.36 (m,
4 H), 4.37 (s, 4 H), 3.84 (s, 6 H). Anal. Calcd for C18H14O4S8:
C, 39.25; H, 2.56. Found: C, 39.57; H, 2.68.
2b: 1.29 g, 94%. Yellow crystals, mp 168-169 °C (toluene).
IR (KBr) (cm-1) 1703, 1481, 1259, 1070. MS: m/ z 550 (M+,
53), 486 (23), 360 (7), 327 (100). 1H-NMR (CDCl3) δ 7.41 (s, 1
the electrode to the solution (Figure 3b). These results
are in accordance with the results obtained by Robert
and co-workers.5l
In the nonstrained macrocycle 10, two well-resolved
reversible two-electron redox systems were observed at
E1/2 ) 0.49 and 0.87 V. The bis-(TTF) 11 showed two
well-resolved reversible peaks at E1/2 ) 0.54 and 0.89 V.
The cyclic TTF derivatives cis-9 (E11/2 ) 0.39 V), trans-9
(E1 ) 0.44 V) and 10 (E1 ) 0.49 V) have a consider-
(12) See the general experimental section in ref 6d.
1/2
1/2
(13) The author has deposited atomic coordinates for this structure
with the Cambridge Crystallographic Data Centre. The coordinates
can be obtained, on request, from the Director, Cambridge Crystal-
lographic Data Centre, 12 Union Road, Cambridge, CB2 1EZ, UK.
ably lower first halfwave potential than the TTF synthon
8b (E1 ) 0.65 V) or the noncyclic bis-TTF 11 (E1
)
1/2
1/2
0.54 V). This phenomenon is probably explained by a

Geometrically Constrained Tetrathiafulvalenophanes
J . Org. Chem., Vol. 62, No. 15, 1997 4941
H), 7.35 (s, 3 H), 4.21 (s, 4H), 3.85 (s, 6 H). Anal. Calcd for
C18H14O4S8: C, 39.25; H, 2.56. Found: C, 39.61; H, 2.60.
2c: 1.32 g, 96%. Yellow crystals, mp 210-211 °C (toluene).
IR (KBr) (cm-1): 1703, 1477, 1259, 1070. MS: m/ z 550 (M+,
33), 486 (7), 360 (7), 327 (100). 1H-NMR (CDCl3) δ 7.38 (s, 4
H), 4.21 (s, 4 H), 3.85 (s, 6H). Calcd for C18H14O4S8: C, 39.25;
H, 2.56. Found: C, 39.57; H, 2.62.
4,4′-(Xylylen ed ith io)bis(5-ca r bom eth oxy-1,3-d ith iol-2-
on es) (3a -c). Gen er a l P r oced u r e. A solution of Hg(OAc)2
(0.96 g, 3.0 mmol) in AcOH (100 mL) was added to a stirred
solution of the thiones (2a -c) (0.55 g, 1.0 mmol) in CHCl3 (100
mL). The mixture was stirred at room temperature for 30 min,
and the white precipitate was filtered off using Celite. The
filtrate was washed with aqueous bicarbonate (3 × 150 mL)
and water (2 × 100 mL). After drying with Na2SO4, the
solvent was removed in vacuo to give off-white crystalline
products. The products were all pure for practical use (NMR
and TLC).
3a : yield 0.45 g, 87%, off-white crystals, mp 188-189 °C
(toluene). IR (KBr) (cm-1) 1701, 1658, 1489, 1261, 1092. MS:
m/ z 518 (M+, 14), 311 (36), 191 (43), 135 (100). 1H-NMR
(CDCl3) δ 7.35 (m, 4 H), 4.35 (s, 4 H), 3.83 (s, 6 H). Calcd for
C18H14O6S6: C, 41.68; H, 2.72. Found: C, 41.82; H, 2.75.
3b: yield 0.47 g, 91%, off-white crystals, mp 168-169 °C
(toluene). IR (KBr) (cm-1) 1702, 1658, 1489, 1262, 1092.
MS: m/ z 518 (M+, 38), 311 (100), 281 (43), 251 (67), 219 (95).
1H-NMR (CDCl3) δ 7.40 (s, 1 H), 7.33 (s, 3H), 4.20 (s, 4H), 3.84
(6H, s). Calcd for C18H14O6S6: C, 41.68; H, 2.72. Found: C,
41.81; H, 2.82.
3c: yield 0.48 g, 93%, off-white crystals, mp 185-186 °C
(toluene). IR (KBr) (cm-1) 1700, 1659, 1490, 1264, 1092.
MS: m/ z 518 (M+, 10), 311 (100), 283 (52), 281 (48), 251 (48),
207 (43). 1H-NMR (CDCl3) δ 7.36 (s, 4 H), 4.19 (s, 4 H), 3.84
(s, 6 H). Calcd for C18H14O6S6: C, 41.68; H, 2.72. Found: C,
41.66; H, 2.72.
point over a 15 min period. After the boiling point was reached
the heating was continued for an additional 5 min. The light
brown solution was cooled down to room temperature and
poured into water (100 mL) to give a yellow suspension. In
order to be able to filter off the product, a small amount of
KCl was added, and the suspension was gently heated. By
this treatment a pale yellow product precipitated and could
be filtered off. The product was washed with water (50 mL)
and dried in vacuo before it was taken up in CH2Cl2 and
filtered through a short layer of silica. The solvent was
removed in vacuo to give pale yellow needles. Yield: 0.12 g,
58%, mp >184 °C dec. IR (KBr) (cm-1) 1630, 1506, 1425.
MS: m/ z 370 (M+, 87), 306 (30), 266 (100), 177 (53). λmax(log
ꢀ): CH2Cl2, 324 nm (3.81). 1H-NMR (CDCl3) δ 7.470-7.475
(m, 2H), 6.668-6.673 (t, 2H, J ) 1.0), 3.91 (d, 2H, J ) 12.0),
3.83 (d, 2H, J ) 12.0). 13C-NMR (CDCl3) δ 135.24, 130.58,
129.28, 127.81, 127.21, 124.63, 41.32. Anal. Calcd for
C14H10S6: C, 45.37; H, 2.72; S, 51.92. Found: C, 45.52; H,
2.90; S, 51.50.
4-[(2-Cyan oeth yl)th io]-5-(m eth oxycar bon yl)-1,3-dith iol-
2-on e (7a ). To a solution of 4-[(2-cyanoethyl)thio]-5-(meth-
oxycarbonyl)-1,3-dithiole-2-thione (6a ) (5.21 g, 18.8 mmol) in
a mixture of chloroform (200 mL) and glacial acetic acid (100
mL) was added Hg(OAc)2 (11.97 g, 37.6 mmol). The reaction
mixture was stirred for 2 h whereupon the white precipitate
was filtered off using a pad of Celite. The filtrate was washed
with a saturated bicarbonate solution (3 × 100 mL) and with
water (2 × 100 mL). After drying (MgSO4) the solvent was
removed in vacuo. Recrystallization from ethanol afforded 7a
as colorless needles. Yield: 4.24 g (86%), mp 152 °C. IR (KBr)
(cm-1): 2249, 1785, 1708, 1658, 1478. MS: m/ z 261 (M+, 100),
130 (60), 88 (80), 59 (50). 1H-NMR (CDCl3) δ (t, 2H, J ) 7.1),
3.25 (t, 2H, J ) 7.1), 3.87 (s, 3H). Anal. Calcd for C8H7-
NO3S3: C, 36.77; H, 2.70; S, 36.80. Found: C, 36.74; H, 2.69;
S, 36.60.
4-[(2-Cya n oe t h yl)t h io]-5-(m e t h ylt h io)-1,3-d it h iol-2-
on e (7b). To a solution of 4-[(2-(cyanoethyl)thio]-5-(meth-
ylthio)-1,3-dithiole-2-thione (6b) (3.87 g, 14.6 mmol) in a
mixture of chloroform (150 mL) and glacial acetic acid (75 mL)
was added Hg(OAc)2 (9.30 g, 29.2 mmol). The reaction mixture
was stirred for 2 h whereupon the white precipitate was
filtered off using a pad of Celite. The filtrate was washed with
a saturated bicarbonate solution (3 × 100 mL) and with water
(2 × 100 mL). After drying (MgSO4), the solvent was removed
in vacuo. Recrystallization from toluene-cyclohexane afforded
colorless nedles of 7b. Yield 3.00 g (82%), mp 61-62 °C. IR
(KBr) (cm-1): 2247, 1662, 1657, 1621, 1481, 1415. MS: m/ z
249 (M+, 43), 91 (100), 88 (29). 1H-NMR (CDCl3) δ 2.52 (s,
3H), 2.74 (t, 2H, J ) 7.0), 3.07 (t, 2H, J ) 7.0). Anal. Calcd
for C7H7ONS4: C, 33.71; H, 2.83; N, 5.62. Found: C, 33.71;
H, 2.86; N, 5.66.
2,6(7)-Bis[(2-cya n oet h yl)t h io]-3,7(6)-b is(m et h oxyca r -
b on yl)t et r a t h ia fu lva len e (8a ). 4-[(2-Cyanoethyl)thio]-5-
(methoxycarbonyl)-1,3-dithiol-2-one (7a ) (9.72 g, 37.2 mmol)
was refluxed in a mixture of benzene (150 mL) and trieth-
ylphosphite (20 mL) for 20 h. After cooling to room temper-
ature the precipitate was filtered off, washed with methanol
(3 × 100 mL), and dried in vacuo. Yield 6.6 g (72%), orange
powder, mp >250 °C dec. IR (KBr) (cm-1): 2250, 1698, 1495,
1434, 1259. MS: m/ z 490 (M+, 84), 451 (36), 289 (100), 88
(58). 1H-NMR (CDCl3) δ 2.80 (t, 2H, J ) 7.3), 3.27 (m, 2H),
3.82 (s, 3H). Anal. Calcd for: C16H14N2O4S6: C, 39.17; H,
2.88; N, 5.71. Found: C, 39.42; H, 2.87; N, 5.65.
2,6(7)-Bis[(2-cya n oet h yl)t h io]-3,7(6)-b is(m et h ylt h io)-
tetr ath iafu lvalen e (8b). 4-[(2-cyanoethyl)thio]-5-(methylthio)-
1,3-dithiol-2-one (7b) (5.76 g, 23.1 mmol) was heated to 110
°C in triethyl phosphite (25 mL) for 45 min. During heating,
an orange product started to precipitate. After cooling to room
temperature, methanol (50 mL) was added and the orange
precipitate was filtered off. The product was washed with
methanol (3 × 100 mL) and dried. Yield 3.75 g (70%), mp
181-183 °C (MeCN). IR (KBr) (cm-1): 2922, 2250, 1727, 1631,
1495, 1424, 1321. MS: m/ z 466 (M+, 100), 412 (39), 277 (29),
223 (32), 91 (50). 1H-NMR (CDCl3) δ 2.45 (s, 3H), 2.71 (t, 2H,
J ) 7.1), 3.03 (t, 2H, J ) 7.1). Anal. Calcd for C14H14N2S8:
C, 36.03; H, 3.02; N, 6.00. Found: C, 36.17; H, 3.09; N, 5.98.
[2]Meta cyclo-1,10-d ith ia [2]((3,6)-d ica r bom eth oxy(2,7)-
tetr a th ia fu lva len o)p h a n e (4b). To a stirred solution of the
dione 3b (1.96 g, 3.66 mmol) in toluene (200 mL) under N2
was introduced freshly distilled P(OEt)3 (20.0 mL, 0.12 mol).
After refluxing for 10 h, the solvent was removed in vacuo .
The red precipitate was subjected to column chromatography
(silica, CH2Cl2-hexane 3:1). The pale yellow band was col-
lected, and a crystalline product was obtained. Yield: 0.76 g,
43%. Recrystallized from glacial acetic acid for microanalysis.
Yellow-orange crystals, mp 233 °C. IR (KBr) (cm-1) 1698,
1495, 1433, 1251, 1075. MS: m/ z 486 (M+, 100), 410 (10),
382 (7), 267 (45), 105 (34). 1H-NMR (CDCl3) δ 7.57 (broad s,
1 H), 7.30-7.20 (m, 3 H), 4.29 (d, 2 H, J ) 14.7), 4.02 (d, 2 H,
J ) 14.7), 3.78 (s, 6 H). 13C-NMR (CDCl3) δ 160.15, 142.23,
137.53, 135.17, 129.29, 128.00, 126.93, 121.62, 52.38, 40.77.
Anal. Calcd for C18H14O4S6: C, 44.42; H, 3.00; S, 39.54.
Found: C, 44.51; H, 2.87; S, 39.62.
[2]P a r a cyclo-1,10-d ith ia [2]((3,6)-d ica r bom eth oxy(2,7)-
tetr a th ia fu lva len o)p h a n e (4c). To a stirred solution of the
dione 3c (2.22 g, 4.28 mmol) in toluene (200 mL) under N2
was introduced freshly destilled P(OEt)3 (20.0 mL, 0.12 mol).
After refluxing for 10 h, the solvent was removed in vacuo.
The red precipitate was subjected to column chromatography
(silica, CH2Cl2-hexane 3:1). The yellow band was collected,
and a crystalline product was obtained. Yield: 1.00 g, 48%.
Recrystallized once from glacial acetic acid for microanalysis.
Yellow-orange crystals, mp 224 °C. IR (KBr) (cm-1) 1725,
1697, 1511, 1490, 1432, 1241. MS: m/ z 486 (M+, 100), 382
(90), 235 (98), 218 (32). 1H-NMR (CDCl3) δ 7.480-7.485 (m,
2H), 6.755-6.760 (m, 2H), 4.19 (d, 2H, J ) 13.2), 4.07 (d, 2H,
J ) 13.2), 3.87 (s, 6H). 13C-NMR (CDCl3) δ 160.15, 139.49,
135.82, 128.36, 128.15, 125.14, 52.62, 40.79. Anal. Calcd for
C18H14O4S6: C, 44.42; H, 3.00; S, 39.54. Found: C, 44.46; H,
2.87; S, 39.45.
[2]P a r a cyclo-1,10-d it h ia [2](2,7)t e t r a t h ia fu lva le n o-
p h a n e (5). A solution of 4c (0.27 g, 0.56 mmol) and CsOH‚
H2O (0.19 g, 1.13 mmol) in dioxane (10 mL) and water (5 mL)
was stirred for 1 h. The solution was then poured into aqueous
HCl to give an orange precipitate. The precipitate was filtered
off, washed with water, and dried in vacuo. The intermediate
acid was then heated in diglyme from 140 °C to the boiling

4942 J . Org. Chem., Vol. 62, No. 15, 1997
Lau et al.
cis/tr a n s-1,7-Dith io[2.1]p a r a cyclo[2](3,6(7))bis(m eth yl-
th io)(2,7(6))tetr a th ia fu lva len op h a n e (9). To a solution of
a mixture of TTF 8b (0.466 g, 1.0 mmol) in anhydrous degassed
DMF (40 mL) was added a solution of CsOH‚H2O (0.376 g,
2.2 mmol) in anhydrous degassed MeOH (10 mL) over a period
of 10 min. After an additional stirring of 15 min, this solution
and a solution of bis[4-(bromomethyl)phenyl]methane (0.354
g, 1.0 mmol) in anhydrous degassed DMF (50 mL) were added
simultaneously, during 10 h at room temperature to 50 mL of
anhydrous degassed DMF, under high dilution conditions
using a perfusor pump. Stirring was continued for additional
5 h, and the reaction mixture was concentrated in vacuo. The
residue was dissolved in CH2Cl2 (150 mL) and washed with
water (3 × 50 mL). After drying (MgSO4), the solution was
concentrated in vacuo affording a residue which was purified
by column chromatography on silica gel (CH2Cl2/petroleum
ether 60-80 °C 1:1, Rf ) 0.62). Yield 0.39 g (71%), an orange
powder (mixture of the cis and trans isomers of paracy-
clotetrathiafulvalenophane 9). Recrystallization from CH2Cl2/
hexane gave, after one night at 4 °C, 0.27 g of a mixture of
red and yellow needles. Concentration of the mother liquor
followed by recrystallization from CH2Cl2/hexane, after one
night at room temperature, afforded an additional crop of 40
mg of a mixture of red needles and yellow plates.
dropwise during 1 h. This reaction mixture was stirred at
room temperature overnight. The solvent was removed in
vacuo, and the resulting residue was dissolved in CH2Cl2 (200
mL), washed with water (3 × 50 mL), dried (MgSO4), and
concentrated in vacuo to afford a brown oil which was
subjected to column chromatography (silica gel, CH2Cl2),
affording 0.55 g (54%) of an orange foam of bis-TTF 11: Rf )
0.68. Mp 52-54 °C. Compound 11: IR (KBr) (cm-1): 2920,
2251 (CN), 1510, 1419, 908. PDMS: m/ z ) 1019.8 (M+‚); calcd
for C37H34N2S16, 1019.65. 1H-NMR (CDCl3) δ 2.20 (s, 6H), 2.47
(s, 6H), 2.69 (t, 4H, J ) 7.2), 3.01 (t, 4H, J ) 7.2), 3.93 (s, 2H),
3.97 (s, 4H), 7.11 (d, 4H, J ) 8.1), 7.22 (d, 4H, J ) 8.1). Anal.
Calcd for C37H34N2S16
: C, 43.62; H, 3.37; N, 2.75; S, 50.26.
Found: C, 43.72; H, 3.38; N, 2.69; S, 50.50.
cis/tr a n s-1,17,28,44-Tetr a th io[2.1]p a r a cyclo[2](3,6)bis-
(m eth ylth io)(2,7)tetr ath iafu lvalen o[2.1]par acyclo-[2](3,6)-
bis(m eth ylth io)(2,7)tetr a th ia fu lva len op h a n e (10). To a
solution of TTF (cis/ trans) 11 (0.52 g, 0.51 mmol) in anhydrous
degassed DMF (25 mL) was added a solution of CsOH‚H2O
(0.205 g, 1.22 mmol) in anhydrous degassed MeOH (5 mL) over
a period of 15 min. This solution and a solution of bis[4-
(bromomethyl)phenyl]methane (0.181 g, 0.51 mmol) in anhy-
drous degassed DMF (30 mL) were added simultaneously,
during 10 h at room temperature with stirring, to 50 mL of
anhydrous degassed DMF, using a perfusor pump. Stirring
was continued for additional 5 h and the reaction mixture
concentrated in vacuo. The residue was then dissolved in CH2-
Cl2 (150 mL) and washed with water (3 × 50 mL). The organic
phase was dried (MgSO4) and concentrated in vacuo to afford
a residue which was purified by column chromatography (silica
gel, CH2Cl2/petroleum ether 60-80 °C, 1:1), affording an
orange-brown powder, 0.31 g (55%) of a mixture isomers of
TTF macrocycle 10. Decomposition without melting between
163-166 °C. IR (KBr) (cm-1): 2918, 1615, 1510, 1420, 889,
772. PDMS: m/ z ) 1105.5 (M+‚); calcd for C46H40S16, 1105.78.
1H-NMR (CDCl3) δ 2.04, 2.12, 2.14 (3s, 12H), 3.91, 3.92, 3.93
(3s, 12H), 7.07 (d, 8H, J ) 8), 7.20 (d, 8H, J ) 8). 13C-NMR
(CDCl3) δ 19.11, 19.14, 40.29, 41.26, 110.63, 124.36, 129.07,
129.10, 129.12, 129.19, 129.25, 134.81, 135.07, 140.30, 140.35.
Anal. Calcd for C46H40S16: C, 49.97; H, 3.65; S, 46.39. Found:
C, 50.25 H, 3.84; S, 43.45.
cis-9 (red): mp 192-194 °C. IR (KBr) (cm-1): 2918, 1616,
1508, 1422, 1110, 894, 820, 771. PDMS: m/ z ) 552.9 (M+‚);
calcd for C23H20S8, 552.89. 1H-NMR (CDCl3) δ 2.44 (s, 6H),
3.86 (s, 4H + 2H), 7.18 (d, 4H, J ) 8.1), 7.28 (d, 4H, J ) 8.1).
trans-9 (yellow): mp 210-212 °C. IR (KBr) (cm-1): 2917,
1611, 1510, 1427, 1199, 1108, 968, 891, 876, 818, 774.
PDMS: m/ z ) 552.9 (M+‚); calcd for C23H20S8, 552.89. 1H-NMR
(CDCl3) δ 2.26 (s, 6H), 3.78 (s, 2H), 3.84 (d, 2H, J ) 13.3),
4.09 (d, 2H, J ) 13.3), 6.84 (d, 4H, J ) 8.1), 7.27 (d, 4H, J )
8.1). Anal. Calcd for C23H20S8H: C, 49.97; H, 3.65; S, 46.39.
Found (mixture of cis/ trans): C, 50.10; H, 3.63; S, 46.15.
Bis[4-[[[3′(4′)-[(2-cya n oet h yl)t h io]-4,4′(3′)-b is(m et h yl-
t h io)t et r a t h ia fu lva len -3-yl]t h io]m et h yl]p h en yl]m et h -
a n e (11). To a solution of TTF 8b (cis/ trans) (0.979 g, 2.1
mmol) in anhydrous degassed DMF (100 mL) was added
dropwise a solution of CsOH‚H2O (0.390 g, 2.3 mmol) in
anhydrous degassed MeOH (25 mL) over a period of 3 h. Then
a solution of bis[4-(bromomethyl)phenyl]methane (0.354 g, 1.0
mmol) in anhydrous degassed DMF (20 mL) was added
J O970326Z