Hierarchical self-assembly of supramolecular helical fibres from amphiphilic C3-symmetrical functional tris(tetrathiafulvalenes)

Article abstract of DOI:10.1002/chem.201404753

The preparation and self-assembly of the enantio-mers of a series of C₃-symmetric compounds incorporating three tetrathiafulvalene (TTF) residues is reported. The chiral citronellyl and dihydrocitronellyl alkyl chains lead to helical one dimens

Full text of DOI:10.1002/chem.201404753

DOI: 10.1002/chem.201404753
Full Paper
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Supramolecular Chirality
Hierarchical Self-Assembly of Supramolecular Helical Fibres from
Amphiphilic C3-Symmetrical Functional Tris(tetrathiafulvalenes)
Flavia Pop,[a] Caroline Melan,[a] Ion Danila,[a] Mathieu Linares,[b] David Beljonne,[c]
David B. Amabilino,*[d] and Narcis Avarvari*[a]
Abstract: The preparation and self-assembly of the enantio-
mers of a series of C3-symmetric compounds incorporating
three tetrathiafulvalene (TTF) residues is reported. The chiral
citronellyl and dihydrocitronellyl alkyl chains lead to helical
one dimensional stacks in solution. Molecular mechanics and
dynamics simulations combined with experimental and the-
oretical circular dichroism support the observed helicity in
solution. These stacks self-assemble to give fibres that have
morphologies that depend on the nature of the chiral alkyl
group and the medium in which the compounds aggregate.
An inversion of macroscopic helical morphology of the citro-
nellyl compound is observed when compared to analogous
2-methylbutyl chains, which is presumably a result of the
stereogenic centre being further away from the core of the
molecule. This composition still allows both morphologies to
be observed, whereas an achiral compound shows no helici-
ty. The morphology of the fibres also depends on the flexi-
bility at the chain ends of the amphiphilic components, as
there is not such an apparently persistent helical morpholo-
gy for the dihydrocitronellyl derivative as for that prepared
from citronellyl chains.
Introduction
is the case when the molecular unit contains a functional
group with a specific property which can be then amplified in
the resulting chiral supramolecular assemblies.[5–8] Furthermore,
collective properties such as electrical conductivity may be ob-
served in the helical aggregates built up from p-conjugated
building blocks.[9] These latter include oligothiophenes,[10,11]
phenylene–vinylenes,[12–14] hexabenzocoronenes,[15,16] and also
tetrathiafulvalene (TTF) units.[17] One of the main objectives of
our research is to use such supramolecular electroactive fibres
in molecular electronics.[18,19]
The interest in chiral conductors[20–22] has been recently high-
lighted through the first experimental observation of the inter-
play between chirality and electrical conductivity in a bulk
crystalline molecular conductor prepared from a chiral TTF de-
rivative.[23] This phenomenon, referred to as electrical magneto-
chiral anisotropy (eMChA) effect,[24] expresses the difference in
the electrical resistance between the two enantiomers of
a chiral conductor, measured in a magnetic field parallel to the
direction of the current.
The formation of chiral supramolecular aggregates is the result
of a self-assembly process during which the molecular building
blocks engage in stereospecific non-covalent intermolecular in-
teractions, such as p–p stacking and hydrogen bonding, the
molecular chirality being transposed at the supramolecular
level.[1–4] Whether this chirality is expressed or not also de-
pends on weaker and less specific van der Waals interactions.[2]
Accordingly, various structural shapes, such as helical fibres,
twisted wires or ribbons, helical tubes, or coiled ribbons, can
be observed in the solid state as expression of the supramolec-
ular chirality at the nano- and mesoscale. Of particular interest
[a] Dr. F. Pop, C. Melan, Dr. I. Danila, Dr. N. Avarvari
Universitꢀ d’Angers, CNRS
Laboratoire MOLTECH-Anjou, UMR 6200
UFR Sciences, Bꢁt. K, 2 Bd. Lavoisier, 49045 Angers (France)
Fax: (+33)02-41-73-54-05
E-mail: narcis.avarvari@univ-angers.fr
C3-symmetric discotic platforms such as benzene-1,3,5-tricar-
boxamides (BTA) substituted with different chiral units proved
to be particularly efficient as triggers of the self-assembly of
molecular units into helical aggregates; they have been thor-
oughly investigated in solution by circular dichroism (CD) and
in solid state by microscopy techniques.[25] Furthermore, even
symmetry breaking can occur in BTA derivatives with rigid
achiral arms.[26] Meijer and co-workers have shown that the
functionalisation of BTA by 3,3’-diamino-2,2’-bipyridine
wedges,[27] which can be then appropriately substituted by
chiral units, induces a propeller conformation to the molecular
building blocks, which is further transmitted to the supra-
[b] Dr. M. Linares
Department of Computational Physics
IFM—Linkçpings Universitet, 581 83 Linkçping (Sweden)
[c] Dr. D. Beljonne
Laboratory for Chemistry of Novel Materials
Universitꢀ de Mons, Place du Parc 20, 7000 Mons (Belgium)
[d] Prof. D. B. Amabilino
Insitut de Ciencia de Materials de Barcelona (ICMAB-CSIC), 08193 Bellaterra
(Spain)
Present Address: School of Chemistry, The University of Nottingham,
NG72RD (UK)
E-mail: David.Amabilino@nottingham.ac.uk
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201404753.
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molecular aggregates built up upon p–p stacking.[28,29] The
chirality of the peripheral groups controls the helicity, M or P,
of the primary fibres, and, moreover, non-linear effects, that is,
“sergeants-and-soldiers”[30] and “majority rules”,[31] have been
evidenced by CD studies. Desymmetrisation of the C3 platform
allowed the modulation of the number of chiral units, the
effect.[37–41] Moreover, the dihydrocitronellyl unit has
demonstrated its usefulness in the control of supramolecular
organisation of BTA derivatives[29–31,42,43] or other related C3-
symmetric platforms.[44]
nature of the appended groups, and, ultimately, the self-as- Results and Discussion
sembly properties.[32,33] To prepare electroactive supramolecular
Synthesis and characterisation
aggregates, we have recently attached thioalkyl containing TTF
units to the 3,3’-bis(acylamino)-2,2’-bipyridine-substituted ben-
zene-1,3,5-tricarboxamide (BiPy-BTA) moieties. Accordingly,
organogels and conducting xerogel upon doping have been
obtained with three achiral bis(thioethyl)TTF fragments (com-
pound A in Figure 1),[34] while by the use of non-amphiphilic
The synthesis of the tris(TTF-citronellyl) derivatives follows the
strategy previously described for the ethyl and 2-methylbutyl
compounds (A and B in Figure 1).[34,35] First, the enantiopure
(S,S) and (R,R) monoacylated derivatives 10a,b have been
selectively obtained by reacting the acid chloride precursors
8a,b with the 3,3’-diamino-2,2’-bipyridine 9 at low tempera-
ture to avoid the bis-acylation reaction. 8a,b were classically
prepared by a sequence involving first the reaction of the
zinc(II) complex 2 with enantiopure citronellyl and dihydroci-
tronellyl bromides affording the dithiole–thiones 3a,b,[45]
which were then coupled with the diester dithiolone 4 to
obtain the diester-TTFs 5a,b. The latter were further mono-
decarboxylated to the monoester-TTFs 6a,b, hydrolysed to the
corresponding acids 7a,b, and finally reacted with oxalyl
chloride to obtain 8a,b (Scheme 1).
The amide protons of 10a,b resonate at d=14.85–
1
14.87 ppm in H NMR, as a consequence of the withdrawing
effect of carbonyl and the intramolecular NꢀH···NPy hydrogen
bond.[34] Further reaction of three equivalents of 10a,b with
one equivalent of trimesic acid chloride affords the tris(TTF) de-
rivatives 1a,b (Scheme 2) as red–brown powders that are very
soluble in chlorinated solvents and in toluene, insoluble in ace-
tone and alcohols at room temperature, while in solvents like
methyethylketone or 1,4-dioxane they are partially soluble at
room temperature and become soluble upon heating. Interest-
ingly, the dihydrocitronellyl derivative (1b) is much more
soluble than the citronellyl species (1a) in alkanes such as
undecane or dodecane, which is probably because of the
more rigid chains in the latter.
Figure 1. C3-symmetrical tris(TTF) compounds.
chiral 2-methyl-butyl groups (compound B in Figure 1), helical
fibres[35] or microscopic croissants[36] formed in the solid state
depending on the preparation conditions. Experimental CD
studies combined with theoretical CD calculations and molecu-
lar mechanics and dynamics modelling clearly demonstrated
that for the (S) configuration of the alkyl chains the primary
fibres in solution were of left-handed (M) helicity, while inver-
sion of the helical sense occurred from the solution to the
solid state.[35] Indeed, optical and electronic microscopy images
have shown the presence of only right-handed (P) solid fibres
or croissants for the configuration (S) of the alkyl substituent.
Thus, inversion of helicity took place during the hierarchical
organisation at the supramolecular level.
Molecular modelling of helical stacks
It is well-established that these chiral C3-symmetric precursors
self-assemble in solution to provide helical stacks. In the previ-
ous study we have shown that when substituted with a (S)-2-
methylbutyl group (compound B in Figure 1), the molecules
prefer to form a counterclockwise (CCW or M) helix,[35] which is
more stable by 2 kcalmolꢀ1 per molecule than the clockwise
(CW or P) helix. For the (S)-dihydrocitronellyl substituent ((S)-
1b), we have built two periodic stacks (CW and CCW) of 15
molecules, which was sufficient to simulate an infinite stack, as
the twist from one unit to the next one is about 8.08 and the
molecule is C3-symmetric. After a periodic optimisation of the
structure and the size of the box, we obtain intermolecular
distances of 3.67 ꢁ and 3.79 ꢁ for the CW and CCW helices,
respectively (Figure 2).
To illustrate the role of the chiral fragment on the self-
assembly properties of the system, herein we investigate the
replacement of the short 2-methylbutyl groups (compound B)
by the citronellyl and dihydrocitronellyl chains (compounds 1a
and 1b, respectively, in Figure 1) that give a more classical
amphiphilic nature to the materials. When compared to com-
pound B, in 1a and 1b the stereogenic centre has been shifted
by one carbon atom, which is expected to have some influ-
ence on the helicity of the aggregates through the “odd–even”
We performed molecular dynamics (MD) simulations on
those two systems in the NVT ensemble, at a temperature of
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Scheme 1. Synthesis of enantiopure tetrathiafulvalene(TTF)–amide–bipyridine precursors.
Scheme 2. Synthesis of enantiopure amphiphilic tris(TTFs).
300 K for 2 ns. When looking at the potential energy along the
trajectories, it does not allow us to determine which system is
the most stable because the fluctuations of energies are more
important than the difference of energy between the two sys-
tems. To be able to differentiate them, we need to optimise
several points along the trajectories. Doing so on two hundred
geometries for each helix, the stabilisation energy per mole-
cule converged to 131.3ꢁ0.7 kcalmolꢀ1 for the CW helix and
130.6ꢁ1.0 kcalmolꢀ1 for the CCW helix, suggesting that the
right-handed primary twist (P) is slightly more stable than the
left-handed twist. Thus, when changing the substituent from
(S)-methylbutyl (compound B) to (S)-dihydrocitronellyl ((S)-1b),
we invert the chirality of the stack from CCW to CW, an inver-
sion that is most likely related to the odd–even effect, as the
stereogenic centre is shifted one carbon away from the TTF
unit.[39] However, more importantly, the stability of one helical
sense over the opposite one (less than one kcalmolꢀ1) is less
pronounced than for analogue B. For (S)-1b, the CD spectrum
has been calculated based on one hundred structures extract-
ed from the MD trajectory (see computational details). As
expected, we obtain a CD signal image of the one obtained
for the precursor B (for a description of the main electronic
transitions that involve contributions from both the TTF and
bipyridine units, see Ref. [32]).
Electronic circular dichroism study
Circular dichroism (CD) spectroscopy has proved its efficiency
in the investigation of chiral supramolecular aggregates in so-
lution,[46] and in particular in the case of precursor B (Figure 1),
which shows strong CD signals in dioxane solutions at concen-
trations of 2–5ꢂ10ꢀ5 m.[35] Accordingly, two intense negative
bands centred at l=387 and 368 nm, assigned to bipyridine-
based transitions, and a shoulder at l=319 nm, corresponding
to a TTF transition, were observed for the (S) enantiomer of B,
and the mirror image signals for the (R) enantiomer. These ex-
perimental CD data combined with molecular mechanics/dy-
namics simulation and theoretical CD calculations allowed to
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Figure 3. CD spectra of the enantiomers (S)-1a (c=5ꢂ10ꢀ5 m) and (R)-1a
(c=4ꢂ10ꢀ5 m) in dodecane in a rectangular cell with 2 mm path length.
Figure 2. Models of CW stack (top left) and CCW stack (top right) for (S)-1b.
Calculated CD spectrum for (S)-1b (bottom).
Figure 4. CD spectra of the enantiomers (S)-1b and (R)-1b (c=10ꢀ4 m in
dioxane, 2 mm path length cell). Inset: temperature dependence of the CD
spectra for the same solution of the (S) enantiomer.
conclude on the preferential occurrence of (M) helical aggre-
gates in solution for the (S)-B precursor. The citronellyl com-
pound 1a gives accurate and reproducible CD signals in do-
decane with the mirror image feature for the two enantiomers
(Figure 3). The most striking difference when compared for ex-
ample (S)-1a to (S)-B is the overall sign inversion of the bands,
as a consequence of the odd–even effect, as the former shows
two positive bands at l=349 and 293 nm, corresponding to
p–p* transitions in bipy and TTF, respectively. However, the
band centred at l=397 nm, assigned to a bipy excitation, still
remains negative for (S)-1a but its intensity is weaker when
compared to the two others. As a general feature, the relative
intensities and maxima of the bands differ between 1a
measured in dodecane and B measured in dioxane, while the
same transitions are involved, underlying the critical role of the
solvent in the self-assembly process.
a more reliable comparison with B, and also in MEK, as in this
solvent solid fibres were obtained (see below). The spectra in
dioxane (Figure 4) are very similar to those of the compound B
except the inversion of sign. Indeed, now the enantiomer (S)
shows intense positive Cotton effects at l=388 and 368 nm
(387 and 368 nm for B) for the bipyridine p–p* transitions,
with chiral anisotropy factors g of around 4ꢂ10ꢀ3 and 3ꢂ10ꢀ3,
respectively, to compare with the anisotropy factors of ꢀ3.1ꢂ
10ꢀ2 and ꢀ1.3ꢂ10ꢀ2 for B. Moreover, the shoulder at l=
326 nm (319 nm for B), and also the broad band centred at
l=465-470 nm, both assigned to the TTF–amide system,[47] are
also observed. In fact, the CD spectra of (S)-1b and (S)-B in di-
oxane show an object mirror-image relationship, and thus the
odd–even effect is now fully expressed. The difference in aniso-
tropy factors might be attributed to the fact that in case of (S)-
B the preference for the (M) over (P) helicity is higher, accord-
ing to the theoretical calculations, than that of (S)-1b for the
(P) over (M) helicity.
Note that the CD spectrum of 1a in methylethylketone
(MEK) is very similar to the one of 1b in the same solvent (Sup-
porting Information, Figure S1). The dihydrocitronellyl com-
pound 1b was investigated in dioxane solutions to have
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Upon heating a dioxane solution of (S)-1b or (R)-1b at 608C
for a couple of minutes, the CD signal completely disappears
(inset in Figure 4). Nevertheless, the cooled solution shows
much more intense bands, suggesting that the final aggre-
gates are better organised than in the initial solution, a similar
behaviour to that of compound B.[35] For example, the band at
l=388 nm has now an anisotropy factor of 1.4ꢂ10ꢀ2, which
represents a circa 3.5-fold increase with respect to the initial
solution, and approaches the value shown by (S)-B. Very likely,
the helical aggregates disassemble upon heating, and at 608C
only short optically inactive aggregates remain. When cooling
back the solution, these aggregates serve as nucleation seeds
for the self-assembly process of the helical fibres, which grow
in a more ordered fashion and in which the chiral preference
for the (P) helicity is more clearly expressed. Moreover, when
a solution of (S)-1b (2ꢂ10ꢀ5 m) is heated at 508C for 30–
40 min, the CD signal disappears and it is not then recovered
by cooling (Supporting Information, Figure S2), showing that
a critical concentration in nucleation seeds is needed to ob-
serve the self-assembly process. However, the addition of
a small volume (10 mL) of fresh solution of (S)-1b in the initial
solution (0.2 mL), showing no more signal after heating, trig-
gers the aggregation processes of the dispersed molecules, as
demonstrated by the CD signals of the new solution, which
are eventually more intense than those of the initial solution
before heating (Supporting Information, Figure S1).
ered upon cooling back to 208C, reaching practically the same
intensity as before heating. The difference with the dioxane
solution probably comes from the fact that, as the molecules
do not self-assemble in CHCl3, in the MEK/CHCl3 9:1 mixture
part of the molecules 1b still remain dispersed in solution. This
particular mixture of solvents was chosen because solid helical
aggregates formed out of it upon re-precipitation (see below).
No evidence for the “majority rules” effect could be observed
for either 1a or 1b, thus emphasising the role of kinetic effects
such as nucleation and growth in the self-assembly process.
Microscopic investigation of macroscopic aggregates
The derivative 1a with the six citronellyl chains forms long
fibres from methylethylketone (MEK) upon cooling a hot solu-
tion of the compound at a concentration of 1 mg per millilitre
on the bench. For the (S) enantiomer these fibres have a clearly
left-handed (M helical) morphology. In accord with the odd–
even effect for chiral compounds, this is the opposite handed-
ness for the fibres formed by same enantiomer of the
compound B with a 2-methylbutyl chain, in that case formed
from dioxane.[35] In the present citronellyl-substituted case, no
fibrous material was obtained from dioxane, presumably
because of the very different solubility of the compound. The
fibres from MEK are very long (several tens of micrometres)
and are between 600 nm and 1 mm wide. Scanning electron
microscope (SEM) images (Figure 6) show that the fibres are
left-handed, although the texture is quite smooth. The ends of
the fibres are tapered, and the fibres occasionally turn at right
angles. The fibres also show helical morphology in the optical
microscope using reflected light (Figure 6) where long regions
of helical order can be discerned. In transmission, no helicity is
seen, but crossing polarisers shows that the fibres are
birefringent and as such they have a relatively high degree of
supramolecular order within them.
The CD spectra of 1b in MEK show basically the same char-
acteristics as those in dioxane, with positive Cotton effects for
the (S) enantiomer and negative for the (R) enantiomer
(Figure 5). The maximum of the two p–p* bipyridine transi-
tions slightly change to l=383 and 364 nm. As the difference
in aggregation between the room temperature and 508C is
very weak in MEK only, a solution of MEK/CHCl3 9:1 was used
for the temperature dependence studies (inset in Figure 5).
As observed, the CD signal disappears upon heating the
sample at 508C for a couple of minutes, and then it is recov-
When the same hot solution in MEK at the same concentra-
tion is cooled slowly to room temperature in a bath over
a period of one hour, very short “chiral croissants” are formed
(Figure 7). The particles are between one and two micrometres
in width and between four and seven micrometres in length,
the aspect ratio being similar in all cases. Often, the objects
appear to be homochiral (see the optical microscope image in
Figure 7), as they are clearly in the case of the chiral croissant-
shaped objects formed under similar conditions in dioxane for
the compound B with the 2-methyl-butyl chain.[36] However,
the SEM images show that there is a non-infrequent inversion
of helicity. The main left-handed spiral is usually seen for the
(S) enantiomer of the citronellyl-substituted species, but the in-
version at the midpoint to give a right-handed helix is also ob-
served (one can be seen right of centre in the SEM image in
Figure 7) or simply a poorly defined structure. The material is
also birefringent, as witnessed by their brightness between
crossed polarising filters in the optical microscope.
The citronellyl derivative 1a is soluble in a wide range of sol-
vents, and also shows aggregate formation in them, unlike the
compound B with 2-methylbutyl chains.[35,36] When MEK is
mixed with THF in a 9:1 ratio and the compound was dis-
Figure 5. CD spectra of the enantiomers (S)-1b and (R)-1b (c=10ꢀ5 m in
methylethylketone (MEK), 2 mm path length cell). Inset: temperature de-
pendence of the CD spectra for the (S) enantiomer in MEK/CHCl3 9:1 solu-
tion (c=2ꢂ10ꢀ5 m).
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Figure 8. Scanning electron microscope image of the fibres of the (S) enan-
tiomer of the citronellyl-substituted compound formed by cooling of a hot
solution in MEK/THF 9:1 on the bench. The morphological helicity of the
fibres is indicated next to them, and a clear inversion point is indicated.
Scale bar: 10 mm.
proximately one-and-a-half micrometres wide and are of the
order of hundreds of micrometres long. Shorter fibres are also
observed with lengths in the region of 50 mm. Interestingly, in
these fibres both M and P morphologies are observed clearly
in all the material. The M morphology is still the dominant
one, but the P morphology is present in many fibres. Helical in-
version points of these macroscopic objects can be seen clear-
ly in the SEM images. The inversion points are also present in
the shorter fibres that are also formed in this precipitation pro-
cess (Figure 9). They can also be inferred in the optical micro-
scope images of these shorter fibres (Figure 9) that are in size
between the chiral croissant-like objects and the longer fibres.
In all of the samples, very short (1–2 mm long) and narrow
fibres (hundreds of nanometres) are also observed, similar to
those seen in the emergent chiral structures in the 2-methyl-
butyl derivative B.[36]
Figure 6. Scanning electron microscope image (top) of the fibres of the (S)
enantiomer of 1a formed by cooling of a hot solution in MEK on the bench,
and (below) a reflection optical microscope image (left) of fibres in the same
sample and a transmission optical image with crossed polarisers (bottom).
Scale bars: 10 mm.
The careful inspection of more than 150 aggregates present
on 21 SEM images allows for a more quantitative estimation of
the helical preference of the fibres formed out of (S)-1a in
MEK/THF. Accordingly, 66% of the fibres show M morphology,
8% P, 18% show both M and P with a centre of inversion,
while about 8% of the fibres do not show any clear helicity.
The observation of an inversion of fibre chirality indicates the
delicate balance in the twisting of the aggregates one way or
the other. It is only in the micrometre-sized aggregates of
these molecules that the helical morphology can be observed;
the smaller structures show a smooth surface. Despite this fact,
chirality is clearly present in the assemblies because they pres-
ent very significant circular dichroic signals. The inversion of
fibre morphology was seen by us in micrometre-sized fibres
formed by a racemic mixture of self-assembling C3 compounds
B,[35] but the observation of the phenomenon here in an enan-
tiopure sample is unprecedented insofar as we are aware.
Moreover, in the enantiopure B inversion of helicity in the solid
fibres has not been observed, which is in agreement with the
higher degree of helical twist discrimination, suggested by the
theoretical calculations, in B than in 1a,b. As in the latter the
Figure 7. Scanning electron microscope image (top) of the “chiral croissants”
of (S)-1a formed by slow cooling of a hot solution in MEK in a bath, and
(below) a reflection optical microscope image of the objects. Scale bars:
5 mm.
solved in the hot mixture at a concentration of 2.45 mgmLꢀ1
cooling on the bench resulted in fibres that show a much
clearer helical morphology than those formed in MEK alone
(Figure 8). The fibres, that have clearly tapered ends, are ap-
,
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Figure 9. Scanning electron microscope image (left) and reflection optical
microscope image (right) of the fibres of the (S) enantiomer of the citronell-
yl-substituted compound formed by cooling of a hot solution in MEK/THF
9:1 on the bench. The inversion of the morphological helicity of the fibres
can be seen at their thickest part and also in the SEM image in the lower
section. Scale bars: 10 mm.
difference in energy between the M and P primary twists for
the same enantiomer is much weaker (see above), helical
inversion might occur with higher probability than in the case
of B.
The dihydrocitronellyl compounds 1b form fibres from MEK,
and mixtures of this solvent with 10% of either chloroform or
THF. In all cases the morphologies are similar. The fibres are rel-
atively short, from several tens to a few hundreds of microme-
tres long (Supporting Information, Figure S3). The helicity is
not always evident in their morphology, but when it is the
fibres show
a clearly P helical morphology for the (R)
enantiomer (Figure 10), in the same way as the citronellyl
derivative does. The width of the fibres is quite uniform, and is
approximately 700 nm.
Therefore in the assembly of dihydrocitronellyl compounds
1b the expression of the chirality from the stereogenic centres
to the morphology of the macroscopic fibres is not as clear as
in the case of the citronellyl compounds, in that smooth mor-
phology is observed frequently. On the other hand, no oppo-
site handedness are seen in the fibres. This subtle situation,
that in a way is a contradiction in that the compound with
enantiomorphic fibres shows greater tendency for helical mor-
phology, is probably a result of the different conformations
and relative rigidity of the chain ends where alkyl or alkene
groups are present.
Figure 10. Optical micrographs of the fibres formed by the (R) enantiomer
of 1b upon precipitation from MEK. Transmission (top), transmission with
crossed polarisers (middle), and reflection (bottom). Scale bars: 5 mm.
On the other hand, slower cooling of the dihydrocitronellyl
compounds also leads to fibres that show helical morphology
on occasion (Figure 11). The length of the individual objects is
between ten and twenty micrometres, somewhat shorter than
those formed under faster cooling conditions. The width of the
fibres is similar in both cases (approximately half a micrometre).
The SEM images shown in Figure 11 show areas of particularly
well-resolved fibres, where it can be observed that the helical
fibres are formed by intertwining smaller ones that sometimes
separate at the ends of the larger objects. In any case, the
morphology is completely different to the helical objects with
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One the other hand, a degree of structural rigidity apparent-
ly favours the emergence of helical morphology in certain
types of aggregate. In the samples that precipitate on relative-
ly slow cooling, chirality is very evident for citronellyl and 2-
methylbutyl substituted compounds in the croissant-like short
fibres that they form. On the other hand, the dihydrocitronellyl
compound forms somewhat longer fibres in which the helical
morphology is not so evident and where the component
smaller fibres tend in some instances to unwind near the fibre
ends, perhaps pointing to a weaker interaction as a result of
the greater flexibility at the chain end compared with the
other compounds. These new series of electroactive C3 com-
pounds demonstrate the flexibility of our approach towards
a control of the helical sense, morphologies, and dimensions
of the supramolecular aggregates. Although so far only hydro-
phobic chains have been attached at the periphery of the disk-
shaped platform, the possibility of using hydrophilic polyether
chains is also envisaged. Moreover, desymmetrisation of the C3
core through the well-established strategy[32,33] would possibly
allow for the modulation of the helical pitch of the mesoscopic
size fibres.
Experimental Section
General
Reactions were carried out under argon and using toluene HPLC.
Nuclear magnetic resonance spectra were recorded on a Bruker
Avance DRX 500 spectrometer (operating at 500.04 MHz for 1H
and 125 MHz for 13C) and a Bruker Avance DRX 300 automatic
spectrometer (operating at 300 MHz for 1H, and 75 MHz for 13C).
Chemical shifts are expressed in parts per million (ppm) downfield
from external TMS. The following abbreviations are used: s singlet,
d doublet, m multiplet, br broad. MALDI-TOF MS spectra were re-
corded on Bruker Biflex-IIITM apparatus, equipped with a 337 nm
N2 laser. Elemental analyses were recorded using Flash 2000 Fisher
Scientific Thermo Electron analyser. The compound 3,3’-diamino-
2,2’-bipyridine 9 has been synthesised according to a previously
reported procedure.[48]
Figure 11. SEM micrographs of the fibres formed by the (S) enantiomer of
1b upon precipitation from a mixture of MEK and chloroform (9:1 v/v). Scale
bars: 10 mm.
a smaller aspect ratio formed by either 1a or the analogous
compounds bearing the 2-methylbutyl group.[36] Fibres are also
formed by the enantiomers of 1b in cyclohexanol, although in
this case a totally smooth morphology is observed (Supporting
Information, Figures S4,S5), and no hint of helicity was
observed in either optical or electronic microscopes.
Synthesis
Conclusion
General method for 6a or 6b: 5a or 5b (see the Supporting
Information; 1 equiv) and LiBr (18 equiv) were mixed in dimethyl-
formamide. The solution was stirred at 858C for 5 h, the formation
of the product being monitored by TLC. Brine was added to the re-
action mixture, the product was extracted with ethyl acetate and
the organic phase was washed with brine and water and then
dried over MgSO4. The solvent was removed under vacuum and
the product was purified by chromatography on a silica column
using petroleum spirit with 5–10% of ethyl acetate.
The use of chiral citronellyl derivatives in C3-symmetric com-
pounds incorporating three TTF units gives the molecules
a preference for one handedness in their self-assembly into
one-dimensional stacks. The odd–even effect in the assembly
(compared with a previous 2-methylbutyl substituted com-
pound) is followed. Great differences are observed in the
higher-order fibres that assemble upon precipitation of the
compounds. A fast cooling of the saturated solutions leads to
the formation of fibres. For the citronellyl substituted com-
pound, the transmission of chirality from the single stacks to
the macroscopic fibres is not as selective as in the case of 2-
methylbutyl chains. Thus, despite the fact that a clear prefer-
ence for single handedness is seen in one dimensional stacks
in solution, the macroscopic objects have morphologies that
display both helical senses despite the presence of a single
enantiomer.
Bis(citronellylthio)methoxycarbonyltetrathiafulvalene (S,S)-6a:
General procedure, starting from (S,S)-5a (2.42 g, 3.66 mmol) and
LiBr (5.72 g, 65.9 mmol). The product was obtained as an orange
oil. Yield 1.70 g (2.82 mmol, 77%).
Bis(citronellylthio)methoxycarbonyltetrathiafulvalene (R,R)-6a:
General procedure, starting from (R,R)-5a (1.85 g, 2.80 mmol) and
LiBr (4.37 g, 50.4 mmol). The product was obtained as an orange
oil. Yield 1.60 g (2.60 mmol, 95%). 1H NMR (300 MHz, CDCl3): d
3
(ppm) 7.35 (s, 1H, HTTF), 5.09 (t, 2H, J=6.9 Hz, C=CH), 3.82 (s, 3H,
CO2CH3), 2.83 (m, 4H, SCH2), 1.98 (m, 4H), 1.69 (s, 6H, C(CH3)2
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trans), 1.61 (s, 6H, C(CH3)2 cis), 1.43–1.70 (m, 6H), 1.15–1.38 (m, 4H,
added dropwise. After 3 h at 458C the colour of the solution
turned to dark violet. The solvent and the excess oxalyl chloride
were removed under vacuum. The resulting dark violet oil,
obtained in quantitative yield, was used in the next step
without further purification.
3
SCH2CH2), 0.91 (d, 6H, J=6.2 Hz, CHCH3). 13C NMR (75 MHz, CDCl3):
d 159.7 (CO2CH3), 131.9 (CCO2CH3), 131.4 (HC=C(CH3)2), 128.3, 128.0,
127.3, 124.5 (HC=C(CH3)2), 52.7 (CO2CH3), 36.8 (CH2), 36.6 (CH2), 34.2
(SCH2), 31.7 (CHCH3), 25.7 (C=CHCH2), 25.4 (CH3 trans), 19.2
(CHCH3), 17.7 (CH3 cis). MS (MALDI-TOF) m/z: 601.6 [M+]; theor.
602.15.
Bis((citronellylthio)chloroformyltetrathiafulvalene (S,S)-8a: Gen-
eral procedure, starting from (S,S)-7a (1.44 g, 2.37 mmol) and
oxalyl chloride (0.88 g, 7.11 mmol). The product was obtained as
a dark violet oil.
Bis((3,7-methyloct-6-octyl)thio)methoxycarbonyltetrathiafulva-
lene (S,S)-6b: General procedure, starting from (S,S)-5b (4.25 g,
6.4 mmol) and LiBr (10 g, 115.2 mmol). The product was obtained
as an orange–red oil. Yield 3.84 g (6.3 mmol, 99%).
Bis((citronellylthio)chloroformyltetrathiafulvalene (R,R)-8a: Gen-
eral procedure, starting from (R,R)-7a (1.5 g, 2.54 mmol) and oxalyl
chloride (0.94 g, 7.62 mmol). The product was obtained as a dark
violet oil.
Bis((3,7-methyloct-6-octyl)thio)methoxycarbonyltetrathiafulva-
lene (R,R)-6b: General procedure, starting from (R,R)-5b (3 g,
4.5 mmol) and LiBr (7 g, 81 mmol). The product was obtained as an
orange-red oil. Yield 2.6 g (4.3 mmol, 95%). 1H NMR (300 MHz,
CDCl3): d 7.34 (s, 1H, HTTF), 3.84 (s, 3H, CO2CH3), 2.78–2.96 (m, 4H,
SCH2), 1.40–1.69 (m, 8H), 1.10–1.33 (m, 12H), 0.87 (d, 6H, 3J=
6.9 Hz, *CHCH3), 0.86 (d, 12H, 3J=6.6 Hz, CH(CH3)2). 13C NMR
(75 MHz, CDCl3): d 159.8 (CO2CH3), 132.0 (CCO2CH3), 128.3, 128.1,
127.3 (CH2SC), 111.9, 109.9, 52.7 (CO2CH3), 39.2, 36.8, 36.7, 34.2,
32.0, 27.9, 24.6, 22.7, 22.6, 19.2. MS (MALDI-TOF) m/z: 605.9 [M+];
theor. 606.18.
Bis((3,7-methyloct-6-octyl)thio)chloroformyltetrathiafulvalene
(S,S)-8b: General procedure, starting from (S,S)-7b (2 g, 3.37 mmol)
and oxalyl chloride (1.28 g, 10.11 mmol). The product was obtained
as a dark violet oil.
Bis((3,7-methyloct-6-octyl)thio)chloroformyltetrathiafulvalene
(R,R)-8b: General procedure, starting from (R,R)-7b (1.5 g,
2.5 mmol) and oxalyl chloride (1 g, 7.5 mmol). The product was ob-
tained as a dark violet oil.
General method for 7a and 7b: A mixture of LiOH·H2O (5 equiv)
was degassed for 15 min and was added under argon to a solution
of 6a or 6b (1 equiv) in dioxane. After a night at room tempera-
ture, the mixture was neutralised with 5m HCl (2 mL) and the
colour turned to red. After 15 min. at room temperature diethyl
ether and several mL of water were added in order to form two
phases. 5m HCl was added until the pH of the mixture became 1;
the two phases were separated and the aqueous phase was ex-
tracted with diethyl ether. The combined organic phases were
dried over MgSO4 and the solvent was removed by evaporation.
General method for 10a and 10b: A solution of 3,3’-diamino-2,2’-
bipyridine 9 (1 equiv) and triethylamine (1 equiv) in dry CH2Cl2 was
cooled at 08C, and then a solution of the acid chloride 8a or 8b
(1 equiv) in dry CH2Cl2 was added dropwise. The mixture was
stirred at 08C for 2 h and overnight at room temperature, affording
a brown solution. The entire mixture was washed several times
with water and once with brine. The organic phase was then sepa-
rated and then dried over magnesium sulfate to afford a red–
brown solid, which was further purified as follows for each type of
compound.
Bis((citronellylthio)tetrathiafulvalenylcarboxylic acid (S,S)-7a:
General procedure, starting from (S,S)-6a (1.61 g, 2.67 mmol) and
LiOH·H2O (0.56 g, 13.35 mmol). The product was obtained as an
orange–red oily solid. Yield 1.44 g (2.37 mmol, 89%).
3’-{[Bis(citronellylthio)tetrathiafulvalenyl]formylamino}2,2’-bipyr-
idine-3-amine (S,S)-10a: General procedure, starting from 3,3’-dia-
mino-2,2’-bipyridine
9 (0.44 g, 2.4 mmol) and (S,S)-8a (1.5 g,
2.4 mmol). The obtained red–brown crude was purified by chroma-
tography on a silica column with dichloromethane. The product
was obtained as an orange–red solid. Yield 1.39 g (1.8 mmol, 76%).
Bis((citronellylthio)tetrathiafulvalenylcarboxylic acid (R,R)-7a:
General procedure, starting from (R,R)-6a (1.60 g, 2.65 mmol) and
LiOH·H2O (0.55 g, 13.25 mmol). The product was obtained as an
orange–red oily solid. Yield 1.53 g (2.6 mmol, 99%). 1H NMR
(300 MHz, CDCl3, selected signals): d (ppm) 6.93 (s, 1H, HTTF), 5.09
(t, 2H, 3J=7.1 Hz, C=CH), 2.74–2.91 (m, 4H, SCH2), 1.98 (m, 4H),
1.69 (s, 6H, C(CH3)2 trans), 1.60 (s, 6H, C(CH3)2 cis), 1.20–1.60 (m,
3’-{[Bis[((R)-citronellyl)thio)]tetrathiafulvalenyl]formylamino}-2,2’-
bipyridine-3-amine (R,R)-10a: General procedure, starting from
3,3’-diamino-2,2’-bipyridine
9 (0.47 g, 2.54 mmol) and (R,R)-8a
(1.54 g, 2.54 mmol). The obtained red–brown crude was purified
by chromatography on a silica column with dichloromethane. The
product was obtained as an orange–red solid. Yield 1.85 g
3
10H), 0.90 (d, 6H, J=6.0 Hz, CHCH3). 13C NMR (75 MHz, CDCl3): d
(ppm) 131.4–131.4 (HC=C(CH3)2), 124.6–124.5 (HC=C(CH3)2), 36.7
(CH2), 31.7 (CHCH3), 25.7 (C=CHCH2), 25.4 (CH3 trans), 19.2 (CHCH3),
17.7 (CH3 cis). MS (MALDI-TOF) m/z: 587.4 [M+]; theor. 588.14.
1
(2.4 mmol, 96%). H NMR (300 MHz, CDCl3) d (ppm): 14.87 (s, 1H,
NH), 9.07 (dd, 1H, 3J=8.5 Hz, 4J=1.5 Hz, Hpy), 8.34 (dd, 1H, 3J=
4.6 Hz, 4J=1.6 Hz, Hpy), 8.11 (dd, 1H, 3J=4.0 Hz, 4J=1.9 Hz, Hpy),
7.29 (m, 1H, HTTF), 7.27 (m, 1H, Hpy), 7.13–7.20 (m, 2H, Hpy), 6.69 (br,
2H, NH2), 5.09 (m, 2H, C=CH), 2.86 (m, 4H), 1.99 (m, 4H, C=CHCH2),
1.67 (d, 6H, CH3 trans), 1.59 (d, 6H, CH3 cis), 1.30–1.70 (m, 6H),
1.10–1.26 (m, 4H), 0.94 (t, 6H, 3J=7.2 Hz, *CHCH3). 13C NMR
(75 MHz, CDCl3) d (ppm): 157.8 (C=O), 145.3, 143.2, 141.2, 138.0,
135.7, 134.8, 133.8, 128.4, 128.0, 126.5, 125.4, 124.3, 122.6, 112.2,
109.9, 36.1, 31.8, 21.7, 13.6. MS (MALDI-TOF) m/z=756.2 [M+];
theor. 756.22.
Bis((3,7-methyloct-6-octyl)thio)tetrathiafulvalenylcarboxylic acid
(S,S)-7b: General procedure, starting from (S,S)-6b (3.8 g,
6.26 mmol) and LiOH·H2O (1.31 g, 31.3 mmol). The product was ob-
tained as an orange–red oily solid. Yield 3.71 g (6.25 mmol, 99%).
Bis((3,7-methyloct-6-octyl)thio)tetrathiafulvalenylcarboxylic acid
(R,R)-7b: General procedure, starting from (R,R)-6b (2.5 g,
4.11 mmol) and LiOH·H2O (0.86 g, 20.6 mmol). The product was ob-
tained as an orange–red oily solid. Yield 2.45 g (4.11 mmol, 100%).
1H NMR (300 MHz, CDCl3): d (ppm) 6.91 (s, 1H, HTTF), 2.79–3.15 (m,
4H, SCH2), 1.42–1.69 (m, 8H, CH2), 1.25–1.31 (m, 12H, CH,CH2), 0.85
3’-{[Bis[(S)-((3,7-methyloct-6-octyl)thio)]tetrathiafulvalenyl]for-
mylamino}-2,2’-bipyridine-3-amine (S,S)-10b: General procedure,
starting from 3,3’-diamino-2,2’-bipyridine 9 (0.62 g, 3.3 mmol) and
(S,S)-8b (2 g, 3.3 mmol). The obtained red–brown crude was puri-
fied by chromatography on a silica column with dichloromethane/
petroleum spirits 2:1. The product was obtained as a red–brown
pasty solid. Yield 1.56 g (2.04 mmol, 62%).
3
3
(d, 6H, J=6.0 Hz, *CHCH3), 0.86 (d, 12H, J=6.6 Hz, CH(CH3)2). MS
(MALDI-TOF) m/z: 592.2 [M+]; theor. 592.17.
General method for 8a and 8b: 7a or 7b (1 equiv) was dissolved
in THF under argon and the solution was heated at 458C. Oxalyl
chloride (3 equiv) and pyridine 10% v/v in THF were immediately
Chem. Eur. J. 2014, 20, 1 – 12
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3’-{[Bis[(R)-((3,7-methyloct-6-octyl)thio)]tetrathiafulvalenyl]for-
mylamino}-2,2’-bipyridine-3-amine (R,R)-10b: General procedure,
starting from 3,3’-diamino-2,2’-bipyridine 9 (0.47 g, 2.54 mmol) and
(R,R)-8b (1.54 g, 2.54 mmol). The obtained red–brown crude was
purified by chromatography on a silica column with dichlorome-
thane/petroleum spirits 2:1. The product was obtained as a red–
(0.47 mmol, 98%). MS (MALDI-TOF) m/z: 2437.6; theor. 2436.72. El-
emental analysis calcd (%) for C120H156N12O6S18: C 59.07, H 6.44,
N 6.89, O 3.93, S 23.66); found: C 58.67, H 6.29, N 6.87, S 22.83.
Microscopy
1
brown pasty solid. Yield 1.15 g (2.4 mmol, 61%). H NMR (300 MHz,
Optical images were collected with a polarising optical microscope
Olympus BX51TRF. SEM images were acquired by scanning electron
microscope (SEM) QUANTA FEI 200 FEG-ESEM system on samples
deposited on gold on mica from the suspension. Contacts were
made between the gold surface and the sample holder with
graphite paste to avoid charging.
3
4
CDCl3): d (ppm) 14.85 (br, 1H, CONH), 9.06 (dd, 1H, J=8.4 Hz, J=
3
4
1.8 Hz, Hpy), 8.32 (dd, 1H, J=4.5 Hz, J=1.5 Hz, Hpy), 8.09 (dd, 1H,
4
3J=4.3 Hz, J=1.8 Hz, Hpy), 7.27 (m, 1H, Hpy), 7.27 (1H, HTTF), 7.13–
7.16 (m, 2H, Hpy), 6.67 (br, 2H, NH2), 2.74–2.94 (m, 4H, SCH2), 1.42–
3
1.70 (m, 8H), 1.21–1.31 (m, 6H), 1.00–1.17 (m, 6H), 0.89 (d, 6H, J=
6.3 Hz, *CHCH3), 1.02 (d, 12H, 3J=6.3 Hz, CH(CH3)2. 13C NMR
(75 MHz, CDCl3): d (ppm) 157.7 (C=O), 145.2, 143.1, 141.1, 137.9,
135.7, 134.7, 133.8, 128.3, 127.9, 127.8, 126.4, 125.4, 124.3, 122.6,
112.2, 109.7, 39.2, 36.8, 3.3, 34.2, 32.1, 27.9, 24.6, 22.7, 22.6, 19.3.
MS (MALDI-TOF) m/z: 759.9 [M+]; theor. 760.25.
Computational details of molecular mechanics and molecu-
lar dynamics
All calculations were performed using the Tinker package[49] and
the MM3 force-field.[50] MD simulations were carried out in the can-
onical ensemble with an integration step of 1 fs at a temperature
of 300 K maintained using a Berendsen thermostat.[51] Simulations
of the single helices were performed using periodic boundary con-
dition in order to simulate infinite stacks during 1 ns for equilibra-
tion followed by 2 ns to collect data. Stabilisation energies were
calculated by optimising snapshots along the MD trajectories every
10 ps, as follows:
General method for 1a and 1b: A solution of 10a or 10b
(1 equiv) and triethylamine (1 equiv) in dry CH2Cl2 was cooled at
08C, and then a solution of trimesic chloride 11 (0.33 equiv) in dry
CH2Cl2 was added dropwise. After 2 h stirring at 08C and one night
at room temperature water was added and the product was ex-
tracted with dichloromethane. The organic phase was further
washed several times with water and the solvent was evaporated.
The resulting solid was further purified as follows for each com-
pound.
N,N’,N’’-Tris{3[3’-{[Bis(((S)-citronellyl)thio)]tetrathiafulvalenyl]for-
mylamino]-2,2’-bipyridyl}benzene-1,3,5-tricarboxamide (S,S)-1a:
General procedure, starting from (S,S)-10a (1.29 g, 1.70 mmol) and
trimesic chloride 11 (0.15 g, 0.56 mmol). The obtained solid was
washed several times with methanol, ethyl acetate, and acetone,
and dried under vacuum. The product was obtained as an analyti-
cally pure red–brown powder. Yield 1.02 g (0.42 mmol, 74%). MS
(MALDI-TOF) m/z: 2426.2; theor. 2424.73. Elemental analysis
calcd (%) for C120H144N12O6S18: C 59.37, H 5.98, N 6.92, O 3.93,
S 23.77; found: C 59.22, H 6.02, N 6.73, S 23.09.
Estab ¼ ðn EisolꢀEstackÞ=n
Where n is the number of molecule in the stack, Eisol is the energy
of an isolated molecule, and Estack is the energy of the stack.
Computational details of CD calculations
The calculation of the excitonic CD spectra proceeds in two steps.
First, the lowest 50 excited states of the 15 molecules involved in
a full turn of the helical structures are computed at the INDO/SCI
level (using an active space of 60 occupied and 60 empty molecu-
lar orbitals). Then, an excitonic Hamiltonian encompassing a total
of 15ꢂ60 basis functions (60 localised excitations per molecule) is
built on the basis of INDO/SCI[52] excitation energies and exciton
couplings. The latter are calculated as Coulomb interactions be-
tween transition densities, thus going beyond the usual point
dipole model.[53] Diagonalisation of this Hamiltonian yields a set of
900 exciton states a with energies hꢀwa and wavefunctions jya >,
for which the rotational strength Ra is computed as:[54]
N,N’,N’’-Tris{3[3’-{[Bis(((R)-citronellyl)thio)]tetrathiafulvalenyl]for-
mylamino]-2,2’-bipyridyl}benzene-1,3,5-tricarboxamide (R,R)-1a:
General procedure, starting from (R,R)-10a (1.85 g, 2.44 mmol) and
trimesic chloride 11 (0.21 g, 0.81 mmol). The obtained solid was
washed several times with methanol, ethyl acetate, and acetone,
and dried under vacuum. The product was obtained as an analyti-
cally pure red–brown powder. Yield 1.6 g (0.37 mmol, 81%). MS
(MALDI-TOF) m/z: 2426.2; theor. 2424.73. Elemental analysis
calcd (%) for C120H144N12O6S18: C 59.37, H 5.98, N 6.92, O 3.93,
S 23.77; found: C 58.08, H 5.83, N 6.18, S 23.37.
N,N’,N’’-Tris{3[3’-{[Bis(S)-((3,7-methyloct-6-octyl)thio)]tetrathiaful-
valenyl]formylamino]-2,2’-bipyridyl}benzene-1,3,5-tricarboxa-
mide (S,S)-1b: General procedure, starting from (S,S)-10b (1.3 g,
1.70 mmol) and trimesic chloride 11 (0.15 g, 0.56 mmol). The ob-
tained solid was washed several times with methanol, pentane,
and acetone, and dried under vacuum. The product was obtained
as an analytically pure red–brown powder. Yield 1.29 g (0.53 mmol,
95%). MS (MALDI-TOF) m/z: 2437.6; theor. 2436.72. Elemental anal-
ysis: calcd for C120H156N12O6S18: C 59.07, H 6.44, N 6.89, O 3.93,
S 23.66; found: C 57.48, H 6.30, N 6.51, S 22.63.
X X
hyaj
m^ jGi ꢂ hGjm^ jyai ꢃ ðrn ꢀ rn0
Þ
;
ꢀhwa
c
i;n
j;n0
ꢀ
ꢀ
ꢀ
ꢀ ꢀ
ꢀ
ꢀ
ꢀ
Ra ¼
ꢀ ꢀ
ꢀ ꢀ
i;n j;n0
m
m
j;n0
i;n
where c is the speed of light, mi,n the transition dipole moment
from the ground state jg> to the excited state ji> of molecule n
along the stack, m^i;n ¼ mi;nðji; nihgj þ hcÞ the corresponding dipole
operator, jG> the ground state of the helical stack (product state
P
of all jg>), and jyai ¼ cai;nji; ni the exciton state wavefunctions
a
i;n
expanded in terms of the ci;n eigenvectors. The CD response at
input frequency w is calculated on the basis of the rotational
strengths as:
N,N’,N’’-Tris{3[3’-{[Bis(R)-((3,7-methyloct-6-octyl)thio)]tetrathiaful-
valenyl]formylamino]-2,2’-bipyridyl}benzene-1,3,5-tricarboxa-
mide (R,R)-1b: General procedure, starting from (R,R)-10b (1.1 g,
1.45 mmol) and trimesic chloride 11 (0.13 g, 0.48 mmol). The ob-
tained solid was washed several times with methanol, ethyl ace-
tate, and acetone, and dried under vacuum. The product was ob-
tained as an analytically pure red–brown powder. Yield 1.15 g
X
CDðwÞ ¼<
Ra Gðw ꢀ waÞ > ;
a
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[23] F. Pop, P. Auban-Senzier, E. Canadell, G. L. J. A. Rikken, N. Avarvari, Nat.
Commun. 2014, 5, 3757.
[24] G. L. J. A. Rikken, J. Fçlling, P. Wyder, Phys. Rev. Lett. 2001, 87, 236602–
1–4.
[25] S. Cantekin, T. F. A. de Greef, A. R. A. Palmans, Chem. Soc. Rev. 2012, 41,
6125–6137.
[26] D. Wang, Y. Huang, J. Li, L. Xu, M. Chen, J. Tao, L. Li, Chem. Eur. J. 2013,
19, 685–690.
where G(wꢀwa) is a Gaussian function centred around wa with var-
iance s=0.1 eV. The brackets denote a configurational average
over the positional and energetic disorder as explored during the
MD simulations. Here, a total of 100 supramolecular helical struc-
tures, each consisting of 15 molecules, were used; this approach
was found to yield CD spectra that are stable with respect to
configurational averaging.
[27] A. R. A. Palmans, J. A. J. M. Vekemans, H. Fischer, R. A. Hikmet, E. W.
Meijer, Chem. Eur. J. 1997, 3, 300–307.
[28] L. Brunsveld, H. Zhang, M. Glasbeek, J. A. J. M. Vekemans, E. W. Meijer, J.
Am. Chem. Soc. 2000, 122, 6175–6182.
Acknowledgements
[29] J. J. van Gorp, J. A. J. M. Vekemans, E. W. Meijer, J. Am. Chem. Soc. 2002,
124, 14759–14769.
[30] A. R. A. Palmans, J. A. J. M. Vekemans, E. E. Havinga, E. W. Meijer, Angew.
Chem. Int. Ed. Engl. 1997, 36, 2648–2651; Angew. Chem. 1997, 109,
2763–2765.
[31] J. van Gestel, A. R. A. Palmans, B. Titulaer, J. A. J. M. Vekemans, E. W.
Meijer, J. Am. Chem. Soc. 2005, 127, 5490–5494.
[32] M. H. C. J. van Houtem, R. Martꢅn-Rapffln, J. A. J. M. Vekemans, E. W.
Meijer, Chem. Eur. J. 2010, 16, 2258–2271.
This work was supported in France by the Ministry of Educa-
tion and Research (grants to I.D. and C.M.), the National
Agency for Research (ANR, Project 09-BLAN-0045–01), the
CNRS and the University of Angers (Ariane mobility program).
I. Freuze and C. Mꢃziꢄre are thanked for performing the MS
analysis, while V. Bonnin is thanked for the elemental analyses.
M.L. thanks SERC (Swedish e-Science Research Center) for fund-
ing and SNIC for providing computer resources. D.B. is a FNRS
Research Director.
[33] M. A. J. Gillissen, M. M. E. Koenigs, J. J. H. Spiering, J. A. J. M. Vekemans,
A. R. A. Palmans, I. K. Voets, E. W. Meijer, J. Am. Chem. Soc. 2014, 136,
336–343.
[34] I. Danila, F. Riobꢃ, J. Puigmarti-Luis, . Pꢃrez del Pino, J. D. Wallis, D. B.
Amabilino, N. Avarvari, J. Mater. Chem. 2009, 19, 4495–4504.
[35] I. Danila, F. Riobꢃ, F. Piron, J. Puigmartꢅ-Luis, J. D. Wallis, M. Linares, H.
ꢁgren, D. Beljonne, D. B. Amabilino, N. Avarvari, J. Am. Chem. Soc. 2011,
133, 8344–8353.
[36] I. Danila, F. Pop, C. Escudero, L. N. Feldborg, J. Puigmartꢅ-Luis, F. Riobꢃ,
N. Avarvari, D. B. Amabilino, Chem. Commun. 2012, 48, 4552–4554.
[37] J. Tabei, R. Nomura, F. Sanda, T. Masuda, Macromolecules 2004, 37,
1175–1179.
[38] P. J. M. Stals, M. M. J. Smulders, R. Martꢅn-Rapffln, A. R. A. Palmans, E. W.
Meijer, Chem. Eur. J. 2009, 15, 2071–2080.
[39] M. M. J. Smulders, P. J. M. Stals, T. Mes, T. F. E. Paffen, A. P. H. J. Schen-
ning, A. R. A. Palmans, E. W. Meijer, J. Am. Chem. Soc. 2010, 132, 620–
626.
Keywords: C3 symmetry
microscopy · supramolecular chirality · tetrathiafulvalene
· circular dichroism · electronic
[1] T. Aida, E. W. Meijer, S. I. Stupp, Science 2012, 335, 813–817.
[2] A. Brizard, R. Oda, I. Huc, Top. Curr. Chem. 2005, 256, 167–218.
[3] M. Crego-Calama, D. N. Reinhoudt, Supramolecular Chirality. Topics in
Current Chemistry, Springer: Berlin, Heidelberg, New York, 2006.
[4] D. B. Amabilino (Ed.), Chirality at the Nanoscale, Wiley-VCH, Weinheim,
2009.
[5] C. C. Lee, C. Grenier, E. W. Meijer, A. P. H. J. Schenning, Chem. Soc. Rev.
2009, 38, 671–683.
[6] V. K. Praveen, S. S. Babu, C. Vijayakumar, R. Varghese, A. Ajayaghosh,
Bull. Soc. Chem. Jpn. 2008, 81, 1196–1211.
[40] J. Zhi, Z. Zhu, A. Liu, J. Cui, X. Wan, Q. Zhou, Macromolecules 2008, 41,
1594–1597.
[41] D. B. Amabilino, J.-L. Serrano, T. Sierra, J. Veciana, J. Polym. Sci. Part A
2006, 44, 3161–3174.
[7] D. Pijper, B. L. Feringa, Soft Matter 2008, 4, 1349–1372.
[8] A. R. A. Palmans, E. W. Meijer, Angew. Chem. Int. Ed. 2007, 46, 8948–
8968; Angew. Chem. 2007, 119, 9106–9126.
[9] M. Hasegawa, M. Iyoda, Chem. Soc. Rev. 2010, 39, 2420–2427.
[10] F. S. Schoonbeek, J. H. van Esch, B. Wegewijs, D. B. A. Rep, M. P. de Haas,
T. M. Klapwijk, R. M. Kellogg, B. L. Feringa, Angew. Chem. Int. Ed. 1999,
38, 1393–1397; Angew. Chem. 1999, 111, 1486–1490.
[42] P. J. M. Stals, J. F. Haveman, R. Martꢅn-Rapffln, C. F. C. Fitiꢃ, A. R. A. Pal-
mans, E. W. Meijer, J. Mater. Chem. 2009, 19, 124–130.
[43] B. Narayan, C. Kulkarni, S. J. George, J. Mater. Chem. C 2013, 1, 626–
629.
[11] D. B. A. Rep, R. Roelfsema, J. H. van Esch, F. S. Schoonbeek, R. M. Kellogg,
B. L. Feringa, T. T. M. Palstra, T. M. Klapwijk, Adv. Mater. 2000, 12, 563–
566.
[12] P. Jonkheijm, P. van der Schoot, A. P. H. J. Schenning, E. W. Meijer, Sci-
ence 2006, 313, 80–83.
[13] A. P. H. J. Schenning, P. Jonkheijm, E. Peeters, E. W. Meijer, J. Am. Chem.
Soc. 2001, 123, 409–416.
[14] R. P. Sijbesma, E. W. Meijer, Chem. Commun. 2003, 5–16.
[15] W. Jin, Y. Yamamoto, T. Fukushima, N. Ishii, J. Kim, K. Kato, M. Takata, T.
Aida, J. Am. Chem. Soc. 2008, 130, 9434–9440.
[16] T. Yamamoto, T. Fukushima, A. Kosaka, W. Jin, Y. Yamamoto, N. Ishii, T.
Aida, Angew. Chem. Int. Ed. 2008, 47, 1672–1675; Angew. Chem. 2008,
120, 1696–1699.
[17] Y. Tatewaki, T. Hatanaka, R. Tsunashima, t. Nakamura, M. Kimura, H.
Shirai, Chem. Asian J. 2009, 4, 1474–1479.
[18] A. P. H. J. Schenning, E. W. Meijer, Chem. Commun. 2005, 3245–3258.
[19] F. J. M. Hoeben, P. Jonkheijm, E. W. Meijer, A. P. H. J. Schenning, Chem.
Rev. 2005, 105, 1491–1546.
[20] N. Avarvari, J. D. Wallis, J. Mater. Chem. 2009, 19, 4061–4076.
[21] A. M. Madalan, C. Rꢃthorꢃ, M. Fourmiguꢃ, E. Canadell, E. B. Lopes, M. Al-
meida, P. Auban-Senzier, N. Avarvari, Chem. Eur. J. 2010, 16, 528–537.
[44] F. Garcꢅa, L. Sµnchez, J. Am. Chem. Soc. 2012, 134, 734–742.
[45] E. Gomar-Nadal, C. Rovira, D. B. Amabilino, Tetrahedron 2006, 62, 3370–
3379.
[46] G. Gottarelli, S. Lena, S. Masiero, S. Pieraccini, G. P. Spada, Chirality 2008,
20, 471–485.
[47] S. A. Baudron, N. Avarvari, E. Canadell, P. Auban-Senzier, P. Batail, Chem.
Eur. J. 2004, 10, 4498–4511.
[48] C. R. Rice, S. Onions, N. Vidal, J. D. Wallis, M.-C. Senna, M. Pilkington, H.
Stoeckli-Evans, Eur. J. Inorg. Chem. 2002, 1985–1997.
[49] J. W. Ponder, TINKER, Ver. 4.2; 2004; http://dasher.wustl.edu/tinker.
[50] a) L. N. Allinger, Y. H. Yuh, J. H. Lii, J. Am. Chem. Soc. 1989, 111, 8551–
8566; b) B. Ma, J. H. Lii, L. N. Allinger, J. Comput. Chem. 2000, 21, 813–
825.
[51] H. J. C. Berendsen, J. P. M. Postma, W. F. van Gunsteren, A. DiNola, J. R.
Haak, Chem. Phys. 1984, 81, 3684–3690.
[52] J. Ridley, M. Zerner, Theor. Chim. Acta 1973, 32, 111–134.
[53] D. Beljonne, J. Cornil, R. Silbey, P. Millie, J. L. Bredas, J. Chem. Phys. 2000,
112, 4749–4758.
[54] F. C. Spano, S. C. J. Meskers, E. Hennebicq, D. Beljonne, J. Am. Chem.
Soc. 2007, 129, 7044–7054.
´
[22] F. Pop, P. Auban-Senzier, A. Fra˛ckowiak, K. Ptaszynski, I. Olejniczak, J. D.
Wallis, E. Canadell, N. Avarvari, J. Am. Chem. Soc. 2013, 135, 17176–
Received: August 6, 2014
17186.
Published online on && &&, 0000
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
11
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
FULL PAPER
Chiral croissants: Amphiphilic citron-
ellyl- and dihydrocitronellyl-based C3-
symmetric tris(tetrathiafulvalene) disk-
shaped derivatives have been synthes-
ised. Their self-assembly properties were
investigated by circular dichroism in
solution and electronic and optical
microscopy in the solid state.
&
Supramolecular Chirality
F. Pop, C. Melan, I. Danila, M. Linares,
D. Beljonne, D. B. Amabilino,*
N. Avarvari*
&& – &&
Hierarchical Self-Assembly of
Supramolecular Helical Fibres from
Amphiphilic C3-Symmetrical
Functional Tris(tetrathiafulvalenes)
&
&
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
12
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!