Page 3 of 3
ChemComm
DOI: 10.1039/C3CC44861D
These results account for the extraordinary stability of the aggreꢀ
gates in the solvent mixture.
Investigations on the aggregates in the solid state were perforꢀ 55 symmetric oligothiopheneꢀproline hybrids were synthesized. The
ture.
In conclusion, on the basis of our rational structural design, aꢀ
med by using TEM. In the TEM micrographs, the presence of cirꢀ
cularly shaped aggregates was detected (Fig. 3). Two borderline
dimensions have been analyzed: the large aggregates evidence a
wellꢀdefined perimeter with a reflecting halo and strong contrast
hybrids revealed strong selfꢀorganizing behaviour in solution and
in the solid state. It is demonstrated that a single amino acid with
two stereocenters can induce a defined helical organization of the
conjugated backbones, which is preserved in the nanoꢀ and micꢀ
5
inside, which is indicative of a vesicle structure (Fig. 3, left). The 60 rometerꢀsized aggregates. The redox activity of the oligothiopheꢀ
size of the vesicles ranges from 0.5 to 1.7 ꢁm diameter. The small
ne unit in the enantiomeric hybrids is fully preserved which alꢀ
lows for further application in electronic devices. In addition, Lꢀ
proline and its derivatives are widely used as highly effective and
selective molecular catalysts; therefore, nanometer sized selfꢀasꢀ
10 structures (diameters between 25 to 75 nm) were randomly distriꢀ
buted in the micrographs and showed as well a brighter contrast
inside (Fig. 3, middle). No evidence of intermediate aggregates
was found. We attribute the inner contrast in the big vesicles to 65 semblies of prolineꢀfunctionalized oligothiophene hybrids in soꢀ
the enclosure of the solvent water in the structures.
lution or on surfaces offer versatile possibilities for the generation
of tailored catalytic microenvironments.
15
We acknowledge financial support of the Volkswagen foundation
70 (Project AZ. 85101ꢀ85103)
Notes and references
1 D. Fichou, Ed. Handbook of Oligo- and Polythiophenes; WileyꢀVCH:
75
Weinheim, Germany, 1999; P. Bäuerle, In K. Müllen, G. Wegner, Eds.;
Electronic Materials: The Oligomeric Approach; Wiley VCH:
Weinheim, Germany, 1998; pp 105ꢀ197.
2 A. Mishra, C.ꢀQ. Ma and P. Bäuerle, Chem. Rev. 2009, 109, 1141ꢀ
1278.
80 3 A. F. M. Kilbinger, A. P. H. J. Schenning, F. Goldoni, W. J. Feast and
E. W. Meijer, J. Am. Chem. Soc., 2000, 122, 1820ꢀ1821; O. Henze, W.
J. Feast, F. Gardebien, P. Jonkheijm, R. Lazzaroni, P. Leclere, E. W.
Meijer and A. P. H. J. Schenning, J. Am. Chem. Soc., 2006, 128, 5923ꢀ
5929.
85 4 K. P. R. Nilsson, A. Herland, P. Hammarstrom and O. Inganäs,
Biochemistry, 2005, 44, 3718ꢀ3724.
5 M. Melucci, G. Barbarella, M. Gazzano, M. Cavallini, F. Biscarini, A.
Bongini, F. Piccinelli, M. Monari, M. Bandini, A. UmaniꢀRonchi and P.
Biscarini, Chem. Eur. J., 2006, 12, 7304ꢀ7312.
90 6 H. A. Klok, A. Rösler, G. Götz, E. MenaꢀOsteritz and P. Bäuerle, Org.
Biomol. Chem., 2004, 2, 3541ꢀ3544.
7 S. R. Diegelmann, J. M. Gorham and J. D. Tovar, J. Am. Chem. Soc.,
2008, 130, 13840ꢀ13841.
8 D. A. Stone, L. Hsu and S. I. Stupp, Soft Matter, 2009, 5, 1990ꢀ1993.
95 9 R. J. Kumar, J. M. MacDonald, Th. B. Singh, L. J. Waddington and A.
B. Holmes, J. Am. Chem. Soc., 2011, 133, 22, 8564ꢀ8573.
10 J. A. Lehrman, H. Cui, W.ꢀW. Tsai, T. J. Moyer and S. I. Stupp, Chem.
Commun., 2012, 48, 9711–9713.
Figure 3 TEM micrographs left (9 x 9 ꢁm2, top and 2 x 2 ꢁm2, bottom)
obtained from dropꢀcasting of a 1:9 THF/H2O solution of hybrid 10S.
Proposed model for the aggregates of 10S, right: (a) π−π interacting enꢀ
20 semble formation, (b) vesicles and (c) unimolecular vesicles formation.
In addition, DLS measurements were taken from hybrid 10S in
THF/water 1:9 showing two different values for the averaged hyꢀ
drodynamic diameter of the aggregates (Fig. S6). Particles of 21
25 nm and 70 nm in diameter were detected which is in good agreeꢀ
ment with the size of the small features observed in the TEM
micrographs. Scarcely bigger aggregates (175 nm and ~ 0.4 ꢁm)
were also determined.
The vesicle formation can be rationalized by taking the amphiꢀ
30 philic character of the oligothiopheneꢀproline hybrids 10R and
10S into account. In the THF/H2O solution, the molecules tend to
aggregate leaving the hydrophilic proline part facing towards the
water. In accordance with the results of the blueꢀshifted absorpꢀ
tion band (Hꢀaggregates) a slightly tilted faceꢀtoꢀface arrangeꢀ
35 ment of the oligothiophene backbones is suggested (Fig. 3, right,
(a)). As the CD results showed, the chirality of the proline moiety
is transferred to the stacks of π−π interacting oligothiophene
backbones leading to the formation of large chiral ensembles
(Fig. 3, right, (a)). Thus, in the THF/H2O solution, the molecules
40 will preferentially form a stable bilayer structure with an all hydꢀ
rophilic surface (Fig. 3, right, (b)). The molecular wedge shape,
which is essential to form vesicles, most probably originates from
the bulky dimension of the proline part compared to the flat rodꢀ
like structure of the alkylated oligothiophene backbone. The bilaꢀ
45 yer of the vesicles expresses as well the leftꢀhanded chirality of
the molecular ensemble. The small structures could be interpreted
as small vesicles formed by unimolecular walls (Fig. 3, right, (c)),
which are as well chiral. In the solvent mixture, the THF might
act as surfactant to stabilize the small vesicles and to overcome
50 the entropic factor. The strong intermolecular interaction and the
stabilization of the vesicles in the two borderline dimensions exꢀ
plain the observed high stability of the aggregates with temperaꢀ
11 A. M. Sanders, T. J. Dawidcyzk, H. E. Katz and J. D. Tovar, ACS
100
Macro Letters, 2012, 1, 1326ꢀ1329.
12 L. Tian, R. Szilluweit, R. Marty, L. Bertschi, M. Zerson, E.ꢀC.
Spitzner, R. Magerle and H. Frauenrath, Chem. Sci., 2012, 3, 1512ꢀ
1521.
13 E.ꢀK. Schillinger, E. MenaꢀOsteritz, J. Hentschel, H. G. Börner and P.
Bäuerle, Adv. Mater., 2009, 21, 1562ꢀ1567; A. K. Shaytan, E.ꢀK.
Schillinger, P. G. Khalatur, E. MenaꢀOsteritz, J. Hentschel, H. G.
Börner, P. Bäuerle and A. R. Khokhlov, ACS Nano, 2011, 5, 6894ꢀ
6909.
14 I.ꢀB. Kim, J. N. Wilson and U. H. F. Bunz, Chem. Commun., 2005,
1273–1275.
15 S. Schmid, A. Mishra and P. Bäuerle, Chem. Commun. 2011, 47,
1324ꢀ1326.
105
110
115
16 A. J. Dirks, J. J. L. M. Cornelissen, F. L. van Delft, J. C. M. van Hest,
R. J. M. Nolte, A. E. Rowan and F. P. J. T. Rutjes, QSAR Comb. Sci.
26, 2007, 11ꢀ12, 1200–1210.
17 M. Kümin, L. S. Sonntag, H. Wennemers, J. Am. Chem. Soc., 2007,
129, 466ꢀ467.
18 R.S. Erdmann, H. Wennemers, Org. Biomol. Chem. 2012, 10, 1982ꢀ
1986
120 19 S. A. Tucker, H. C. Bates, V. L. Amszi, W. E. Acree, Jr., H. Lee, P.
Di Raddo, R. G. J. C. Fetzer and G. Dyker, Anal. Chim. Acta, 1993,
278, 269ꢀ274.
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 3