C O M M U N I C A T I O N S
molecular arrangement. Thus, a small tape (0.24 × 0.10 × 0.005
-
mm) prepared from wires of 1•+‚ClO4 showed a conductivity of
σrt ) 1.1 × 10-3 S cm-1, suggesting more effective conduction
due to a hexagonally ordered columnar structure, whereas the film
-
of 1•+‚ClO4 showed a conductivity of σrt ) 3.1 × 10-5 S cm-1
.
In summary, we have synthesized a novel TTF hexamer 1 with
a flexible disk-like structure, weak amphiphilic nature, and strong
self-aggregation properties. Nanowires fabricated from 1 in a
CHCl3/hexane solution have a hexagonal columnar structure,
reflecting the lateral and π-π stacking interactions of its disk-like
frame. Furthermore, we have also succeeded in formation of fibrous
material with a hexagonal columnar structure from 1•+‚ClO4-. We
believe this is a quite rare example of nanowires prepared from
organic ion radical salts. The electric conductivity of the wire of
1•+ is 2 orders of magnitude higher than that of the film of 1•+,
reflecting their nanostructured, one-dimensional morphologies.
Figure 1. (A) SEM image of entangled fibrous material of neutral 1 with
5000× magnification. (B) XRD pattern of hexagonal nanowires of 1 on an
aluminum plate.
Acknowledgment. This work was supported in part by a Grant-
in-Aid for scientific research from JSPS. We would like to thank
Prof. Y. Tobe (Osaka University) for his assistance with VPO
measurements.
Supporting Information Available: Details of the synthesis,
aggregation behavior, and characterization of nanostructures of 1,
1•+‚ClO4-, and 13+‚(ClO4-)3. This material is available free of charge
Figure 2. (A) SEM image of a fibrous material of 1•+‚ClO4- with 5000×
magnification. (B) Powder XRD patterns of a hexagonal columnar structure
of 1•+‚ClO4-; the inset shows the region of 17.5 < 2θ < 30°.
References
•+
-
(TTF)2 unit, and the association constants of 1•+‚ClO4 and
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structure of the stacked 1•+ and 13+ can be expected in solution,13
ESR spectra of 1•+‚ClO4- and 13+‚ClO4- in CHCl3 (23 °C) exhibit
the existence of 100% spin for 1•+ (g ) 2.0068) and 33% spin for
13+ (g ) 2.0073), respectively, suggesting weak intermolecular
spin-spin interaction in 1•+ and strong intramolecular spin-spin
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the cationic charges, whereas nanowires of 1 (Figure 1A) prefer to
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-
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reflections based on a hexagonally ordered lamellar structure (a0
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couple of reflections (d ) 25.5 and 13 Å) corresponding to laterally
stacking arrangement. The longer distance (d ) 25.5 Å) of the film
of 1•+‚ClO4- compared to that of 1 (d ) 21.4 Å) may reflect more
overlapping structure of 1•+‚ClO4- which rises perpendicularly from
the surface of the aluminum plate. Another point which should be
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(12) The film of 1 exhibits weak FET properties, reflecting a lamellar structure
vertical to the substrate (Figure S16, Supporting Information).
(13) Small-angle X-ray scattering (SAXS) analysis of 1•+ and 13+ in THF
reveals cylinder structures with 11 Å radius and 14-16 Å high, and hence
three to five disk-like 1•+ and 13+ stacks on average, although 1 shows
no self-aggregation in THF (Figure S24, Supporting Information).
-
noted is that the lattice constants (a0) of nanowires of 1•+‚ClO4
are smaller than that of 1 despite the presence of a ClO4
-
counteranion.
The electric conductivities of the wires and film of 1•+‚ClO4
-
exhibit a considerable difference according to their different
JA069025+
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