Wang et al.
Chart 1. Chemical Structures of the Gelators Studied Herein
Article
1
1a (0.36 g, 0.34 mmol, 68%): H NMR (400 MHz, Pyr) δ
9.33-9.28 (m, 2H), 8.26 (d, J=8.4 Hz, 2H), 7.78 (s, 2H), 7.61 (s,
1H), 7.16 (s, 1H), 6.63 (t, J=6.6 Hz, 2H), 4.32 (t, J=6.4 Hz, 2H),
4.03 (t, J=6.4 Hz, 4H), 3.80 (dd, J=11.0, 5.3 Hz, 4H), 2.07-1.94
(m, 4H), 1.85-1.78 (m, 4H), 1.73-1.66 (m, 2H), 1.50-1.41 (m,
4H), 1.30 (br, 48H), 0.90 (t, J=6.7 Hz, 9H). 13C NMR (101 MHz,
Pyr) δ 168.1, 167.4, 154.0, 141.7, 132.3, 131.0, 128.5, 128.1, 125.2,
120.5, 120.3, 115.8, 115.1, 107.8, 107.1, 93.7, 83.5, 74.0, 69.7, 37.8,
37.7, 32.6, 31.3, 30.8, 30.4, 30.2, 30.1, 27.0, 26.8, 23.4, 14.7.
MALDI-TOF-MS: m/z calcd for C61H92N2O5S4: 1061.6; found:
1060.4 [M]þ. Anal. calcd (%) for C61H92N2O5S4: C, 69.01; H,
8.73; N, 2.64; found: C, 69.07; H, 8.80; N, 2.82.
1b (0.23 g, 0.28 mmol, 56%): 1H NMR (400 MHz, Pyr) δ 9.18
(t, J=5.5 Hz, 1H), 8.22 (d, J=8.2 Hz, 2H), 7.88 (t, J=5.8 Hz,
1H), 7.17 (s, 1H), 6.63 (t, J=6.8 Hz, 2H), 5.41 (d, J=4.9 Hz, 1H),
4.97-4.84 (m, 1H), 3.80 (q, J=6.2 Hz, 2H), 3.56 (dd, J=12.1, 6.0
Hz, 2H), 2.64-2.44 (m, 2H), 2.05-0.91 (m, 40H, cholesterol and
NHCH2CH2CH2NH), 0.68 (s, 3H, cholesteryl CH3). 13C NMR
(101 MHz, Pyr) δ 167.3, 157.7, 140.7, 132.3, 128.5, 128.1, 125.1,
123.0, 120.5, 120.3, 115.8, 115.1, 107.8, 93.7, 83.4, 74.5, 57.2, 56.8,
50.7, 42.9, 40.3, 40.1, 39.6, 39.1, 38.1, 37.7, 37.2, 36.9, 36.4, 32.6,
32.5, 31.2, 30.4, 29.1, 28.9, 28.6, 24.9, 24.6, 23.3, 23.1, 21.7, 19.8,
19.4, 12.4. MALDI-TOF-MS: m/z calcd for C46H60N2O3S4:
817.2; found: 816.4 [M]þ, 839.4 [MþNa]þ. Anal. calcd (%) for
C46H60N2O3S4: C, 67.60; H, 7.40; N, 3.43; found: C, 67.62; H,
7.53; N, 3.49.
system composed of 1D highly aligned fibers via π-π and
hydrogen bonding interactions, and the mixed-valence state of
the TTF stack was obtained after doping with iodine. Kato et al.31
combined electroactive TTF-derived gelators with a liquid-crys-
tal approach to generate oriented-gel fibers with electrical con-
ductivity of 10-5 S cm-1. Amabilino et al.32,33 recently prepared
electroactive fibrillar nanowires from an amide-functionalized
TTF organogel with a bulk conductivity of 3-5ꢀ10-3 S cm-1 at
room temperature after doping with iodine and an irreversible
phase transition after heating. All of the results indicate that the
use of intermolecular noncovalent interactions via a gelation
process to construct TTF-based conducting fibers is very appeal-
ing, although most of the fibers exhibit moderate to poor
conductivities, presumably due to the poor ability to form a good
conduction path between the TTF cores.
Particular interest in building 1D conductive nanostructures
and understanding cooperative intermolecular interactions in-
volved in self-assembly process prompted us to prepare the set
of TTF derivatives 1-2 shown in Chart 1. Herein, 3,4,5-tris-
(n-dodecyloxy)benzoylamide substituents a and cholesteryl group
b as versatile gel-forming segments,6-9 the amide groups, and one
or two electroactive TTF residues were readily introduced to
2a (0.46 g, 0.36 mmol, 72%): 1H NMR (400 MHz, Pyr) δ 9.44
(t, J=5.8 Hz, 1H), 9.27 (t, J=5.8 Hz, 1H), 8.32 (d, J=1.3 Hz,
2H), 7.77 (s, 2H), 7.64 (t, J=1.4 Hz, 1H), 6.65 (d, J=1.2 Hz, 4H),
4.31 (t, J=6.4Hz, 2H), 4.03 (t, J=6.4Hz, 4H), 3.84 (d, J=4.9Hz,
4H), 2.16-2.09 (m, 2H), 2.01-1.94 (m, 2H), 1.86-1.80 (m, 4H),
1.73-1.65 (m, 2H), 1.52-1.49 (m, 4H), 1.30 (br, 48H), 0.90 (t, J=
6.8 Hz, 9H). 13C NMR (101 MHz, CDCl3) δ 167.9, 166.4, 154.0,
141.6, 136.9, 131.7, 131.1, 128.5, 120.5, 120.3, 115.5, 115.3, 107.7,
107.0, 92.5, 83.0, 74.0, 69.7, 38.2, 37.9, 32.6, 31.3, 30.7, 30.4, 30.2,
30.1, 30.1, 27.0, 26.9, 23.4, 14.7. MALDI-TOF-MS: m/z calcd for
C69H94N2O5S8: 1288.0; found: 1288.4 [M]þ. Anal. calcd (%) for
C69H94N2O5S8: C, 64.34; H, 7.36; N, 2.17; found: 64.72; H, 7.53;
N, 2.28.
2b (0.25 g, 0.24 mmol, 48%): 1H NMR (400 MHz, Pyr) δ 9.30
(t, J=5.3 Hz, 1H), 8.32 (d, J=1.3 Hz, 2H), 7.91 (t, J=5.3 Hz,
1H), 7.63 (s, 1H), 6.67-6.63 (m, 4H), 5.43-5.41 (m, 1H),
4.90-4.85 (m, 1H), 3.84 (dd, J = 12.3, 6.2 Hz, 2H), 3.61 (dd,
J=12.1, 6.0 Hz, 2H), 2.66-2.62 (m, 1H), 2.48 (t, J=11.7 Hz, 1H),
2.12-0.90 (m, 40H, cholesterol and NHCH2CH2CH2NH), 0.69
(s, 3H, cholesteryl CH3). 13C NMR (101MHz, Pyr) δ 166.1, 157.7,
140.7, 137.0, 136.8, 131.7, 128.5, 123.4, 123.0, 120.6, 120.3, 115.5,
115.2, 107.8, 92.6, 83.0, 74.5, 57.2, 56.8, 50.6, 42.9, 40.4, 40.1, 39.6,
39.3, 38.4, 37.7, 37.2, 36.9, 36.5, 32.6, 32.5, 31.0, 29.1, 28.9, 28.6,
24.9, 24.6, 23.4, 23.1, 21.7, 19.8, 19.4, 12.4. MALDI-TOF-MS: m/
z calcd for C54H62N2O3S8: 1043.6; found: 1042.5 [M]þ. Anal.
calcd (%) for C54H62N2O3S8: C, 62.15; H, 5.99; N, 2.68; found: C,
61.97; H, 6.08; N, 2.75.
examine the roles and extent of the π-π stacking and S
S
3 3 3
contacts among the TTF cores, the hydrogen-bonding, and the
van der Waals forces among the amide groups and long alkyl
chains or cholesteryl group as well (Chart 1). It is anticipated that
with the cooperative multiple intermolecular interactions, such
compounds can self-assemble into long fibers in organic solvents
and entangle further to form gels. In these fibers, the more TTF
residues may provide a more efficient conducting pathway.
Comparison of the electrical conductivities of xerogels upon
partial oxidization by iodine not only offers ideal TTF-based
conductive nanostructures, but also provides valuable informa-
tion as to what extent the TTF cores interact in these self-
assembling fibers. The detailed results are presented below.
Results and Discussion
Synthesis and Characterization. The synthesis of new gela-
tors based on TTFs 1-2 were accomplished in high yields by
using the Sonogashira reaction (Scheme 1). The starting com-
pounds 3 with different R groups and gel-forming segments a and
b, were directly coupled with iodo-substituted benzoic acid, with
the aid of the coupling reagent benzotriazol-1-yl-oxytripyrrolidi-
nophosphonium hexafluorophosphate (PyBOP) in a mixture of
dimethylformamide (DMF) and CH2Cl2, to give compounds
4 and 5. The Sonogashira reactions of 4 and 5 with excess
(trimethylsilyl)acetylene (TMSA) yielded 6 and 7, respectively,
which were then deprotected by excess K2CO3 in the mixture of
CH3OH and CH2Cl2 to afford the terminal alkyne compounds 8
and 9. Then, 8 and 9 were reacted with 2-iodotetrathiafulvalene in
Experimental Section
The synthesis of compounds 3-9 is described in the Supporting
Information.
General Synthetic Procedures for 1 and 2. Tothemixtureof
anhydrous tetrahydrofuran (THF; 30 mL) and triethylamine
(TEA; 30 mL) were added 8 (0.50 mmol) or 9 (0.50 mmol),
TTF-I (0.60 or 1.2 mmol), CuI (3.8 mg, 0.02 mmol), and Pd-
(PPh3)4 (12 mg, 0.01 mmol) under Ar. The reaction mixture was
refluxed over 12 h under Ar atmosphere and was monitored by
thin-layer chromatography (TLC). Upon completion, the solu-
tion was evaporated in vacuo to dryness. The crude product was
purified by silica gel flash column chromatography (CH2Cl2/
EtOAc, 30/1) to give compound 1 or 2 as a red solid.
Langmuir 2011, 27(2), 774–781
DOI: 10.1021/la103686n 775