Calix[4]arenes with 1,2- and 1,3-upper rim tetrathiafulvalene bridges

Article abstract of DOI:10.1080/10610278.2013.872245

Herein we report the synthesis of several calix[4]arene derivatives with tetrathiafulvalene bridges at the upper rim. Calix[4]arene-tetrathiafulvalene (TTF) conjugates 4a-d, fixed in cone conformation and comprising two smaller 1,2-bridges, were prepared

Full text of DOI:10.1080/10610278.2013.872245

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Calix[4]arenes with 1,2- and 1,3-upper rim
tetrathiafulvalene bridges
Matthias H. Dükera, Felix Kuttera, Thomas Dülcksa & Vladimir A. Azova
a Department of Chemistry, University of Bremen, Leobener Str. NW 2C, D-28359 Bremen,
Germany
Published online: 20 Jan 2014.
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To cite this article: Matthias H. Düker, Felix Kutter, Thomas Dülcks & Vladimir A. Azov (2014) Calix[4]arenes with 1,2- and
1,3-upper rim tetrathiafulvalene bridges, Supramolecular Chemistry, 26:7-8, 552-560, DOI: 10.1080/10610278.2013.872245
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Supramolecular Chemistry, 2014
Vol. 26, Nos. 7–8, 552–560, http://dx.doi.org/10.1080/10610278.2013.872245
Calix[4]arenes with 1,2- and 1,3-upper rim tetrathiafulvalene bridges
Matthias H. Du¨ker, Felix Kutter, Thomas Du¨lcks and Vladimir A. Azov*
Department of Chemistry, University of Bremen, Leobener Str. NW 2C, D-28359 Bremen, Germany
(Received 13 September 2013; accepted 21 November 2013)
Herein we report the synthesis of several calix[4]arene derivatives with tetrathiafulvalene bridges at the upper rim. Calix[4]
arene-tetrathiafulvalene (TTF) conjugates 4a–d, fixed in cone conformation and comprising two smaller 1,2-bridges, were
prepared by cyclisation of tetrakis-chloromethylated calix[4]arene 1 with 2,3-dithiolates of TTFs. Larger calix[4]arene-TTF
macrocycles 14 and 15, also in cone conformation, contain 1,3-bridges and were synthesised by cyclisation of 2,6- and 2,7-
dithiolates of TTFs with bis-bromomethylated calix[4]arene 7. Redox properties of new calix[4]arene-TTF conjugates were
characterised using cyclic voltammetry.
Keywords: macrocycles; calixarenes; tetrathiafulvalenes; cyclic voltammetry
1. Introduction
two recent works report the preparation of upper rim-
modified calix[4]arenes with multiple TTF substitution
(16). These derivatives were used for anion recognition via
hydrogen bonding with amido groups, linking the TTF
units to the upper rim of calixarene backbones. In both of
these upper rim conjugates, TTF and calix[4]arene
moieties were connected using single TTF linkers.
Calixarenes, a family of macrocylic compounds assembled
from aromatic building blocks, are widely used in different
areas of supramolecular chemistry (1). Selective synthetic
methods (1, 2) allow the targeted preparation of
calixarenes with different ring size, which can be further
substituted at the lower (phenolic hydroxyl groups) or at
the upper (positions para to the HO-groups) rims. In this
way, calixarene scaffolds can be used for the construction
of receptors for neutral or charged guests (3), assembly of
molecular capsules (4) or for the formation of tailored
molecular networks in the solid state (5). The smallest
member of the calix[n]arene family, calix[4]arene, can be
locked in four principal conformations, each of which
exhibits different orientations of substituents on the lower
and upper rims, allowing to control the spatial arrangement
of the attached functional groups. This opportunity can be
employed, for example, to arrange the mutual orientation
of multiple dye labels in calix[4]arene-derived fluorescent
probes (6).
2. Results and discussion
Our goal was to study the possibility to prepare calix[4]
arene derivatives with 1,2- (between p-position of the two
neighbouring phenyl rings) and 1,3- (between p-position
of the two opposite phenyl rings) TTF bridges at the upper
rim in cone and 1,3-alternate conformations of the
calixarene backbone.
Two calixarene scaffolds, 5,11,17,23-tetrakis(chloro-
methyl)-25,26,27,28-tetrapropoxycalix[4]arenes fixed in
cone 1 (17) and 1,3-alternate 2 (18) conformations, were
prepared as described before from commercially available
p-tert-butylcalix[4]arene (Scheme 1).
Our group has been long interested in design and
construction of redox-active molecular architectures
comprising tetrathiafulvalene (TTF) building blocks (7).
TTFs (8) have played the role of switching units (9) in
various molecular (10) and supramolecular architectures
(11), as well as in materials chemistry (12). Nevertheless,
only a relatively small number of TTF-calixarene
derivatives has been prepared and tested so far (13–16).
The majority of those derivatives were lower rim calix[4]
arene (14) or thiacalix[4]arene (15) conjugates, which
were aimed for binding of ions via polar interactions
centred on the TTF-calixarene linkers (14b–g), or for the
study of metal-promoted electron-transfer (14h,i). Only
Then, cyclisation experiments employing 2,3-disub-
stituted TTFs were carried out (Scheme 2). Calix[4]arene-
TTF derivatives 4a–d, fixed in cone conformation and
comprising two 1,2-bridges, were prepared by reaction of
2,3-dithiolates of TTFs (19), generated in situ from 2,3-bis
(2-cyanoethylthio)TTFs 5a–d, with the calixarene deriva-
tive 1. The products precipitated from the reaction
mixtures upon methanol addition and could be further
purified using flash chromatography (FC) (20).
Quite surprisingly for us, the same reaction with
calixarene 2, fixed in 1,3-alternate conformation, com-
pletely failed to work. Only polar and poorly soluble
*Corresponding author. Email: vazov@unibremen.de
q 2014 Taylor & Francis

Supramolecular Chemistry
553
Scheme 1. Synthesis of calix[4]arene backbones 1 and 2.
decomposition products and no traces of the target
compound 6 could be detected in the reaction mixture.
Taking into account the possibility of cation complexation
by the calixarene backbone in 1,3-alternate conformation
due to p–cation interactions, which can be especially
favourable in the case of the ‘soft’ Csþ(21), we have tested
several other bases, containing Kþ, Naþ and [NMe4]þ as
counterions, but none of these reactions proved to be
successful. ESI-MS spectra showed trace amounts of the
[6·Cs]þ ion along with a large number of different side-
products when CsOH was used as a base, confirming the
formation of the target compound, but also implying its
very low yield or high instability.
commercially available 1 in four steps as described earlier
(22). Then it was formylated in a one pot reaction, which
included bromine-lithium exchange followed by quenching
of the bis-metallated intermediatewith dimethylformamide
(DMF) affording compound 9 (23). After reduction of the
two formyl groups with NaBH4 and bromination of the
formed hydroxyls using PBr3, the target calixarene 7 with
two opposite bromomethyl groups could be isolated.
Still, even using calix[4]arene 7, the attempted 1,3-
cyclisation with 2,3-TTF bridges did not work as expected
(Scheme 4). Although trace amounts of the target product
11 could be detected upon analysis of the crude reaction
mixture using ESI-MS, its instability on SiO2 during
chromatography precluded its separation and characteris-
ation in pure form.
Being intrigued by the negative outcome of the
attempted 1,3-bridging of the calix[4]arene backbone
fixed in 1,3-alternate conformation, we decided to check
the possibility of 1,3-cyclisation of the calix[4]arene in
the cone conformation. For that reason, 5,17-dibromo-
methyl-25,26,27,28-tetra-(1-propoxy)calix[4]arene 7 was
prepared (Scheme 3). Compound 8 was synthesised from
In order to explore the possibility to introduce another
type of upper rim TTF bridges, 2,6- and 2,7-bis-
cyanoethylthio-protected TTFs 12 were prepared from
2,3,6,7-tetrakis(2-cyanoethylthio)TTF 13 by its two-fold
alkylation with hexylbromide (Scheme 5). Although Z- und
Scheme 2. Attempted syntheses of calix[4]arene-TTF conjugates 4a–d and 6.

¨
M.H. Duker et al.
554
Scheme 3. Synthesis of calix[4]arene backbone 7.
E-isomers of 12 display almost identical 1H NMR spectra,
separation of multiplets of S-CH2 groups can be seen in the
600 MHz spectra (Figure 1). Due to significant difference in
Rf values, separation of both isomers was possible using FC,
which was followed by their detailed characterisation (24).
Compounds (Z)-12 and (E)-12 display noticeable differ-
ences in their melting points as well as in the chemical shifts
of the carbon atoms of the TTF backbone,1 otherwise all
other spectroscopic properties of the two isomers are almost
similar.2 Although fast chromatographic separation of the
two isomers was possible, unexpectedly fast Z–E
interconversion was observed between (Z)-12 and (E)-12.
Identity of the 2 þ 2 cyclisation products (Z/E)-15 after
chromatographic separation was determined using ESI-
MS. Due to the presence of two TTF moieties, each of
which slowly interconverts between Z or E configurations
upon standing in a solution, products of the 2 þ 2
cyclisation exist as a mixture of four possible isomers
(Z/E)-15, where ‘Z/E’ denotes the isomer mixture (26).
The large ring size precludes sterical strain in the
macrocylces, leading to the condition when none of the
isomers has significant thermodynamic advantage over the
others. Therefore, upon standing, isomer mixtures with
nearly equivalent isomer distribution can be expected,
3
1
In CH2Cl2 or CHCl3 solution in the dark, isomerisation
leading to observation of broadened signal patterns in H
NMR, as well as in 13C NMR spectra.
proceeded to a significant amount within several days and
was complete in 1–2 weeks, affording mixtures with a
slight surplus of the (E)-isomer. Isomerisation of 12 takes
place even in the solid state and isomerisation products
could be detected in samples which were kept at room
temperature for 1–2 months.
In ESI-MS, all macrocycles show formation of adducts
with alkali metal cations (Naþ, Kþ), whereas the bis-TTF
macrocycles (Z/E)-also exhibit simultaneous binding of two
metal cations forming doubly charged complexes. Addition-
ally, radical cations were always observed in ESI-MS,
indicating low oxidation potentials of the TTF-containing
macrocycles. The UV–vis spectra of derivatives 14 and 15
(CH2Cl2, 293 K) showed the typical absorption pattern for
tetrathio-substituted TTFs with absorption bands at lmax ca.
310and330 nm, aswell asa shoulder from ca.390to450nm.1
The cyclic voltammograms (CVs) of the mono-TTF
derivative (Z)-14 show the classical redox behaviour of TTF
(8), displaying two quasi-reversible electrochemical pro-
cesses on the cathodic scan (Figure 2 and Table 1), the first
one giving the TTF radical cation and the second one leading
to the dication. On the other hand, the CVs of bis-TTF
derivatives (Z/E)-15 display a splitting of the first oxidation
Cyclisation attempts using 2,6- or 2,7-TTF bridges
proved to be successful. Using chromatography, it was
possible to separate 1 þ 1 cyclisation products (Z)-14 or
(E)-14 from a reaction with (Z)-12 or (E)-12, respectively,
as well as the mixtures of 2 þ 2 cyclisation products (Z/E)-
15. Of the two smaller macrocycles 14, only the Z-isomer
(Z)-14 was found to be a stable compound. The E-isomer
(E)-14 isomerises rather fast upon standing in a solution,
affording predominantly the thermodynamically more
stable (Z)-14, as well as minor amounts of unknown
decomposition products, which makes its characterisation
(13C NMR, cyclic voltammetry) almost impossible (25).
Scheme 4. Attempted 1,3-bridging of calix[4]arene 7.

Supramolecular Chemistry
555
Scheme 5. Synthesis of 2,6- and 2,7-bis-cyanoethylthio-protected TTFs 12 and 1,3-upper rim-bridged calix[4]arene-TTF macrocycles
14 and 15. Note the numbering of the TTF backbone.
wave with DE11=2 < 0:13 V, indicating the sequential
formation of the mono-(radical cation) and the bis-(radical
cation). This observation suggests the formation of mixed
valence ½TTFꢀþ2 z dimers, in which the first-formed radical
cation is stabilised by the p electrons of the neighbouring
splitting, indicating that both TTF moieties are oxidised at the
same potential and do not form mixed valence ½TTFꢀ2þz
dimers. This observation can be explained by the relative
rigidity of macrotricylce 4, which prohibits the quasi-parallel
˚
stacking of two TTF moieties at a distance of ca. 3.5–4A,
required for formation of the dimers.4
TTF moiety, leading to an increase of the second
2ðþzÞ
monoelectronic oxidation step to ½TTFꢀ2
due to the
We can only speculate about the factors prohibiting the
synthesis of macrocycles 6 and 11, whereas the formation of
the macrocyclic derivatives 4, as well as of 14 and 15, proceeds
with reasonable yields under exactly the same reaction
conditions. Molecular modelling performed using PM3 did not
give evidence of any steric hindrance in 6 and 11. We believe
that one of the plausible factors leading to cyclisation failure
may be the spatial proximity of the opposite CH2S groups in 6,
as well as in 11, which are locked in pinched cone (flattened
cone) conformation. It has been noticed before that the cone
calix[4]arene derivatives with two hydroxymethyl substituents
in the 1,3-positions of the upper rim (analogous to 10, but with
different substituents on the lower rim) are prone to form a
cyclic ether product with a ZCH2OCH2Z bridge between the
two opposite phenyl rings under basic conditions (28). Another
report describes the formation of the same cyclic ether upon
reaction of the upper rim calix[4]arene macrocycle with a
flexible 1,3-bridge under acidic conditions (29). Moreover,
a highly efficient intramolecular Cannizzaro reaction readily
occurs only between 1,3-distal formyl groups at the upper rim
of a calix[4]arene in cone conformation, but not between 1,2-
proximal groups (30). All this evidence implies a special
relationship between the 1,3-distal upper rim substituents in
proximity of the first-formed radical cation, as it is known
from the literature (27). Opposite to the CVs of 15 (20), the
first oxidation wave of bis-TTFs 4a–d did not display
Figure 1. 1H NMR spectrum (600 MHz, CDCl3) of the (Z)-12/
(E)-12 mixture with an excess of (E)-12.

¨
M.H. Duker et al.
556
TTFs. On the other hand, 1,3-bridging employing 2,3-
disubstituted TTFs did not proceed, neither with cone nor with
1,3-alternate conformations of the calix[4]arene scaffold.
Unfortunately, due to poor electron-donating properties of
tetrakis-thioalkyl-substituted TTFs, such macrocycles did not
prove to be good binders of electron-deficient guests (20), and
now we focus our research on the development of calix[4]
arene-TTF receptors employing more efficient monopyrrolo-
TTF as electron-donating moieties (31).
4. Experimental part
4.1 General
Compounds 1 (17), 2 (18), 5 (19), 9 (23) and 13 (19) were
prepared as described before. Compounds 10 and 11 have
beenreportedpreviously(32), but nosynthetic proceduresand
characterisation were given. Synthesis and characterisation of
compounds 4a–d have been reported by our group before
(20). Reagent grade chemicals and solvents were used without
further purification unless otherwise stated. All reactions were
carried out under atmosphere of dry N2. NMR spectra were
recorded using Bruker Avance DPX-200, Bruker Avance
WB-360, or Bruker Avance DRX600 spectrometers (Bruker
BioSpin GmbH, Rheinstetten, Germany). Chemical shifts (d)
are reported in parts per million (ppm) downfield from
tetramethylsilane using the residual CHCl3 (7.26 ppm for 1H,
Figure 2. CVs of calix[4]arene-TTF macrocycles in
CH2Cl2/0.1 M Bu4NClO4, scan rate 100 mV s21, potentials are
plotted versus SCE.
Table 1. Electrochemical data of calixarene-TTF derivatives.a
ox10
1=2
ox2
Compound
Eo1x=12=E
(V)
E
(V)
1=2
(Z)-14
(Z/E)-15
4ab
0.43
0.90
0.82
0.83
0.78
0.78
0.88
0.45/0.58
0.47
0.50
0.48
0.50
4bb
1
77.0 ppm for 13C), CH2Cl2 (5.32 ppm for H) or acetone
4cb
(2.05 ppm for 1H) signals as a reference. Low resolution mass
spectra were measured on Finnigan MAT 8200 or Finnigan
MAT 95 spectrometers (Thermo Finnigan Mat GmbH,
Bremen, Germany) for electron ionisation (EI, 70 eV), and on
a Bruker Esquire-LC spectrometer (Bruker Daltonik GmbH,
Bremen, Germany) for electrospray ionisation (ESI). High-
resolution MS-spectra (HRMS) were measured on a Finnigan
MAT 95 spectrometer (Thermo Finnigan Mat GmbH,
Bremen, Germany) (EI, 70 eV) and on a Thermo Fisher
Scientific LTQ Orbitrap spectrometer (Thermo Fisher
Scientific Inc., Waltham, MA, USA) (ESI). Measured isotopic
patterns of the Mþ ions of all reported compounds were fully
consistent with the calculated ones. UV/vis measurements
were performed on a Varian Cary 50 Conc spectrophotometer
(Varian, Inc., Palo Alto, CA, USA) in a 1 cm path length
quartz optical cell. Melting points were determined using
capillary melting point apparatus and are uncorrected. Rf
values were determined using 0.2 mm silica gel F-254 thin
layer chromatography cards. Flash chromatography (FC) was
carried out using 230–440 mesh (particle size 36–70 mm)
silica gel.
4db
a Values given at room temperature versus SCE; the Fc/Fcþ couple
(0.480 V vs. SCE in CH2Cl2) was used as an internal reference.
b Redox potentials of compounds 4a–d are taken from our previous report
(20) and recalibrated versus SCE.
the cone conformation of calix[4]arene, leading to enhance-
ment of the reactivity of one group by the assistance of the
second one. Such assistance is possible after a calix[4]arene
molecule adopts the pinched cone conformation, bringing 1,3-
distal groups into the close mutual proximity. The same
assumption can be extended to calix[4]arenes in 1,3-alternate
conformation, in which 1,3-distal substituents are also forced
to stay proximal to each other. Among the calix[4]arene-TTF
macrocycles discussed earlier, both macrocycles 6 and 11
comply with this assumption, whereas 14 is fixed in the
pinched cone conformation with a large separation between
the two substituted phenyl rings.
3. Conclusions
To conclude, we have tested the possibility of preparation of
calix[4]arenes with 1,2- and 1,3-TTF bridges on the upper
rim. We could isolate and characterise the calix[4]arene-TTF
macrocyles 4a–d with two 1,2-bridges comprising 2,3-
disubstituted TTFs, as well as the larger macrocycles 14 and
15 with 1,3-bridges comprising 2,6 and 2,7-disubstituted
4.2 Cyclic voltammetry
Samples for cyclic voltammetry were dissolved to a
concentration of 1 £ 1023 M in dry degassed CH2Cl2
containing 0.1 M Bu4NClO4 (tetrabutylammonium per-

Supramolecular Chemistry
557
chlorate, TBAP) as a supporting electrolyte. Measure-
ments were carried out with a computer-controlled HEKA
PG390 potentiostat (HEKA Elektronik GmbH, Lam-
brecht, Germany) in a three-electrode single-compartment
cell (2.5 ml) with a platinum disk working electrode
(diameter of 1.5 mm) and a platinum wire used as a
counter electrode. A non-aqueous Ag/Agþ secondary
electrode (0.1 M TBAP þ 0.01 M AgNO3 in MeCN) was
used as the reference electrode. Ferrocene was used as a
(CDCl3, 50 MHz):d ¼ 156.9, 156.5, 135.4, 134.9, 130.7,
128.8, 128.3, 122.2, 76.8, 76.7, 34.7, 30.9, 23.3, 23.1, 10.3,
10.2. MS (EI, 70eV) m/z (%) 776 (20) [M]þz, 697 (100)
[M–Br]þ. HRMS (EI): m/z 776.20653 (calcd for
C42H50Br2O4: 776.20758, D ¼ –1.35ppm).
4.5 2,6-Bis(20-cyanoethylthio)-3,7-bis(hexylthio)-TTF
(Z)-12 and 2,7-bis(20-cyanoethylthio)-3,6-bis(hexylthio)-
TTF (E)-12
ox
reference with the potential E ¼ 0:48 V versus satu-
1=2
rated calomel electrode (SCE) for Fc/Fcþ pair in CH2Cl2
(33). The oxidation potential of the Fc/Fcþ pair was
recorded before and after each CV measurement and used
for calibration purposes. The values of oxidation potentials
of TTF derivatives are reported versus SCE.
2,3,6,7-Tetrakis(2-cyanoethylthio)TTF
13
(1 g,
1.84 mmol) was dissolved in dry DMF (60 ml) and
degassed using the freeze-pump-thaw method, and then
CsOH (3.68 mmol, 3.35 ml) was added as a 1.1 M solution
in MeOH at 0 8C. The mixture was allowed to warm to r.t.
and stirred for 30 min, changing its colour from orange to
dark brown-red. Afterwards, n-bromohexane (0.77 ml,
5.5 mmol) was added to the solution and the mixture
stirred overnight at r.t. The crude product was purified by
FC (CH2Cl2/PE, 1:1) to afford the cis- and trans-isomers
as an orange powder.
4.3 5,17-Dihydroxymethyl-25,26,27,28-tetra-(1-
propoxy)calix[4]arene 10
5,17-Diformyl-25,26,27,28-tetra-(1-propoxy)calix[4]arene
9 (4.28 g, 6.6 mmol) was dissolved in absolute ethanol
(150ml), NaBH4 (204mg, 5.4 mmol) was added and the
solution stirred for 1.5 h. When the reaction was complete,
ethanol was removed under reduced pressure and the residue
dissolved in CH2Cl2 (100ml). The solution was washed
twice with water (200ml), dried and evaporated to dryness.
The crude product was purified by FC (CH2Cl2/EtOAc/Hex)
to afford a white amorphous foam. Yield 3.94g (6.03 mmol,
92%). Rf: 0.14 (SiO2, CH2Cl2/EtOAc/Hex, 2:2:3). 1H NMR
(CDCl3, 200 MHz): d ¼ 6.90–6.93 (m, 4H), 6.75–6.82 (m,
2H), 6.37 (s, 4H), 4.45 (d, 2J ¼ 13.3Hz, 4H), 4.16 (s, 4H),
(Z)-12:yield370 mg(0.61 mmol, 33%). M.p.:77–788C.
Rf: 0.35 (SiO2, CH2Cl2/PE, 4:1). 1H NMR (360MHz,
CDCl3): d ¼ 3.03 (t, 3J ¼ 7.4 Hz, 4 H), 2.87 (t, 3J ¼ 7.4 Hz,
4 H), 2.70 (t, 3J ¼ 7.4 Hz, 4H), 1.60–1.68 (m, 4 H), 1.37–
1.45 (m, 4 H), 1.25–1.35 (m, 8 H), 0.91 (t, 3J ¼ 6.8 Hz, 6 H).
13C NMR (90 MHz, CDCl3):d ¼ 133.8, 121.9, 117.5, 110.6,
36.4, 31.2, 31.2, 29.7, 28.1, 22.5, 18.7, 14.0. MS (EI, 70eV):
m/z (%) 606 (100) [M]þz, 552 (5) [M–CH2CH2CN]þ.
HRMS (EI): m/z 606.04922 (calcd for C24H34N2S8
606.04877, D ¼ 0.74 ppm). CV (vs. SCE, CH2Cl2):
3
3
ox1
1=2
ox2
1=2
3.97 (t, J ¼ 7.9 Hz, 4H), 3.73 (t, J ¼ 7.1 Hz, 4H), 3.15
E
¼ 0:60 V, E ¼ 0:86 V.
2
(d, J ¼ 13.3Hz, 4H), 1.82–2.01 (m, 8H), 1.66 (bs, 2H),
(E)-12: Yield 430 mg (0.71 mmol, 38%). M.p.: 111–
0.89–1.09 (m, 12H). 13C NMR (CDCl3, 50 MHz):
d ¼ 157.1, 155.6, 135.9, 134.3, 134.2, 128.7, 126.4, 122.1,
76.6, 64.9, 31.0, 23.4, 23.0, 10.6, 10.0. IR (KBr): 3350, 2961,
2930, 2874, 1456, 1383, 1216, 1036, 1007cm21. MS (EI,
70eV) m/z (%) 652 (20) [M]þz, 634 (100) [M–H2O]þz.
112 8C. Rf: 0.56 (SiO2, CHCl2/PE, 4:1). 1H NMR
(360 MHz, CDCl3): d ¼ 3.03 (t, 3J ¼ 7.4 Hz, 4H), 2.87 (t,
3J ¼ 7.4 Hz, 4 H), 2.70 (t, 3J ¼ 7.4 Hz, 4H), 1.60–1.68 (m,
4 H), 1.37–1.45 (m, 4 H), 1.25–1.35 (m, 8 H), 0.91
(t, 3J ¼ 6.8 Hz, 6 H). 13C NMR (90 MHz, CDCl3):
d ¼ 134.0, 121.5, 117.5, 110.6, 36.4, 31.3, 31.2, 29.7,
28.1, 22.5, 18.7, 14.0. MS (EI, 70 eV): m/z (%) ¼ 606
(100) [M]þz, 552 (4) [M–CH2CH2CN]þ. HRMS (EI): m/z
606.04838 (calcd for C24H34N2S8 606.04877, D ¼ –
4.4 5,17-Dibromomethyl-25,26,27,28-tetra-(1-
propoxy)–calix[4]arene 7
0.64 ppm). CV (vs. SCE, CH2Cl2): Eo1x=12 ¼ 0:60 V,
To a solution of 5,17-dihydroxymethyl-25,26,27,28-tetra-
(1-propoxy)calix[4]arene 10 (200 mg, 0.306 mmol) in
CH2Cl2 (30 ml), PBr3 (86 mg, 30ml, 0.32mmol) was
added dropwise, and the reaction mixture was stirred for
further 10min. Then the mixture was washed with saturated
NaHCO3 solution (2 £ 30ml), dried and evaporated to
dryness to afford the pure product in form of a white
powder. Yield 226 mg (0.290mmol, 95%). M.p.: 110 8C. Rf:
ox2
1=2
E
¼ 0:86 V.
4.6 TTF-calixarene coupling, general procedure
TTF derivative 12 was dissolved in absolute DMF and
degassed by a freeze-pump-thaw cycle, and then CsOH
was added as a solution in MeOH at 0 8C. The mixture was
allowed to warm to r.t. and stirred for 30 min, changing its
colour from orange to dark brown-red. Calixarene 7 was
dissolved in dry tetrahydrofuran (THF), and the solution
was degassed by a freeze-pump-thaw cycle. Afterwards,
1
0.2 (SiO2, CH2Cl2/PE, 6:2). H NMR (CDCl3, 200 MHz):
d ¼ 6.63–6.67 (m, 6H), 6.59 (s, 4H), 4.42 (d, 2J ¼ 13.3Hz,
4H), 4.17 (s, 4H), 3.78–3.89 (m, 8H), 3.13 (d, 2J ¼ 13.3Hz,
4H), 1.84–1.97 (m, 8H), 0.93–1.03 (m, 12H). 13C NMR

¨
M.H. Duker et al.
558
the calixarene solution was added to one portion of the
previously prepared thiolate solution at 20 8C, and then the
mixture was allowed to warm to r.t. gradually and stirred
for an additional 3 h.
(200 mg, 0.26 mmol) in 4 ml THF. After the reaction, the
solvent was removed under reduced pressure and the crude
product purified by FC on silica gel to afford (E)-14 and
(Z/E)-15 as orange–yellow amorphous powders. High-
quality 13C NMR of (E)-14 could not be recorded due to its
fast decomposition/isomerisation to (Z)-14.
4.7 Macrocycles (Z)-14 and (Z/E)-15
(E)-14: Yield 45 mg (0.04 mmol, 15%). M.p.: 110–
115 8C. Rf: 0.50 (SiO2, CH2Cl2/cyclohexane, 1:2). 1H
NMR (200 MHz, acetone-d6): d ¼ 6.73–6.79 (m, 4H),
6.37–6.42 (m, 6H), 4.41 (d, 2J ¼ 13.3 Hz, 4H), 3.65–4.03
(m, 12H), 3.12 (d, 2J ¼ 13.3 Hz, 4H), 2.75–2.88 (m, 4H),
1.90 (bs, 8H), 1.60 (bs, 4H), 1.20–1.51 (m, 12H), 0.83–
0.12 (m, 18H). UV–vis (CH2Cl2): lmax (1) ¼ 309 nm sh
(16,000 l mol21 cm21), 333 (14,000), 392 sh (3800). MS
(ESI): m/z 1155.4 [M þ K]þ, 1139.4 [M þ Na]þ, 1116.4
[M]þz. HRMS (ESI): m/z 1116.35134 (calcd for
C60H76O4S16 1116.35038, D ¼ 0.86 ppm).
Prepared from (Z)-12 (86 mg, 0.14 mmol) in 25 ml DMF,
CsOH (250 ml, 0.28 mmol, 1.1 M in MeOH) and 7
(100 mg, 0.13 mmol) in 4 ml THF. After the reaction, the
solvent was removed under reduced pressure and the crude
product purified by FC on silica gel to afford (Z)-14 and
(Z/E)-15 as orange–yellow amorphous powders.
(Z)-14: Yield 32 mg (0.029 mmol, 22%). M.p.: 142–
144 8C. Rf: 0.34 (SiO2, CH2Cl2/cyclohexane, 1:2). 1H
NMR (360 MHz, CDCl3): d ¼ 7.08 (s, 4H), 6.77 (d,
3J ¼ 7.6 Hz, 4H), 6.49 (t, 3J ¼ 7.6 Hz, 2H), 4.44 (d,
2J ¼ 13.3 Hz, 4H), 3.98 (t, 3J ¼ 7.6 Hz, 4H), 3.76 (s, 4H),
3.67 (t, 3J ¼ 7.6 Hz, 4H), 3.18 (d, 2J ¼ 13.3 Hz, 4H), 2.86
(Z/E)-15: Yield 136 mg (0.061 mmol, 46%).
3
(t, J ¼ 7.3 Hz, 4H), 2.18–2.29 (m, 4H), 1.85–1.95 (m,
4H), 1.63–1.72 (m, 4H), 1.38–1.50 (m, 4H), 1.24–1.37
Acknowledgements
3
3
(m, 8H), 1.03 (t, J ¼ 7.6 Hz, 6H), 1.01 (t, J ¼ 7.6 Hz,
6H), 0.90 (t, 3J ¼ 6.9 Hz, 6H). 13C NMR (90 MHz,
CDCl3): d ¼ 156.2, 154.3, 136.4, 134.0, 132.4, 131.9,
129.3, 128.3, 124.4, 124.1, 108.2, 78.0, 77.2, 41.4, 36.0,
31.3, 30.2, 29.7, 28.2, 23.3, 23.2, 22.5, 14.0, 10.5, 10.0.
UV–vis (CH2Cl2): lmax (1) ¼ 275 nm (16,000 l mol21
cm21), 311 sh (12,000), 333 (11,200), 420 (2300). MS
(ESI): m/z 1155.4 [M þ K]þ, 1139.5 [M þ Na]þ, 1134.5
[M þ NH4]þ, 1116.5 [M]þz. HRMS (ESI): m/z
1116.35167 (calcd for C60H76O4S8 1116.35038,
We are indebted to Ms D. Kemken (MS), Mr J. Stelten (NMR)
and Dr Uli Papke (HR-MS, TU Braunschweig) for their help with
the characterisation of the new compounds.
Funding
M. H. D. is grateful to BFK NaWi, University of Bremen, for
financial support.
D ¼ 1.16 ppm). CV (vs. SCE, CH2Cl2): Eo1=x21 ¼ 0:43 V,
Supplementary information
1H/13C NMR spectra and signal assignment of two isomers of 12,
UV–vis spectra of macrocycles 14 and 15.
ox2
1=2
E
¼ 0:90 V.
(Z/E)-15: Yield 62 mg (0.028 mmol, 43%). M.p.: 115–
120 8C. Rf: 0.55–0.61 (SiO2, CH2Cl2/cyclohexane, 1:2).
1H NMR (360 MHz, CDCl3): d ¼ 6.28–6.83 (m, 20H),
2
Notes
4.38 (d, J ¼ 13.3 Hz, 8H), 3.61–3.98 (m, 24H), 3.10 (d,
3
2J ¼ 13.3 Hz, 8H), 2.75 (t, J ¼ 7.2 Hz, 8H), 1.78–2.02
1. See Supplementary Information for details.
2. Assignment of (Z) or (E) configuration of 12 was carried out
(m, 16H), 1.52–1.68 (m, 8H), 1.19–1.48 (m, 24H), 0.79–
1.09 (m, 36H). 13C NMR (90 MHz, CDCl3): d ¼ 156.5,
156.1, 136.0, 135.5, 135.2, 134.9, 134.5, 134.3, 134.0,
129.2, 129.0, 128.9, 128.8, 128.5, 128.2, 128.0, 122.6,
122.4, 110.5, 77.0, 40.5, 36.3, 31.3, 30.9, 29.6, 28.1, 23.2,
23.1, 22.5, 14.1, 10.4, 10.2. UV–vis (CH2Cl2): lmax
(1) ¼ 311 nm sh (29,000 l mol21 cm21), 333 (27,000), 395
sh (7200). MS (ESI): m/z 2255.4 [M þ Na]þ, 2232.4
on the basis of the available literature by comparison of 13
C
NMR spectra and polarities of the products with the reported
TTF derivatives possessing longer alkyl chains, see Ref.
(24).
3. Deactivated using aluminum oxide.
4. Molecular modelling using PM3 gave evidence for the
impossibility of close stacking of the two TTF moieties in 4.
On the other hand, such contacts are energetically favourable
in 15, in case both calixarene moieties adopt pinched cone
conformations with two upper rim-substituted benzene rings
aligning parallel to each other.
[M]þz, 1138.3 [M þ 2Na]2þ
. HRMS (ESI): m/z
2232.70359 (calcd for C120H152O8S16 2232.70130,
D ¼ 1.03 ppm). CV (vs. SCE, CH2Cl2): Eo1=x21:1 ¼ 0:45 V,
ox1:2
1=2
ox2
1=2
E
¼ 0:58 V, E ¼ 0:82 V.
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