For the dark conductivity measurements, a Keithly 4200
source measuring unit was used for taking the I/V character-
istics.
The morphologies of the obtained structures were then
characterized by field emission scanning electron microscopy.
Conclusions
The synthesis of a new [2.2]paracyclophane 2 has been de-
scribed. These studies show how linearly-functionalized
[2.2]paracyclophanes 1 and 2, interacting with poly(3-bu-
tylthiophene), are largely responsible for the generation of
charge carriers in this semiconducting conjugated polymer
under illumination. We have also found the possibility of
modifying the morphology and conductivity of the blends by
applying an electric bias during the evaporation of the solvent.
Such a simple deposition method provides the means for an
evident trend towards the facile preparation of photoactive
materials of high current interest. This result may suggest that
this methodology provides an orientation of the molecules
along the direction of intermolecular p–p stacking. Verifying
this evidence will remain a challenging task in our future work.
Scheme 2 Schematic illustration of the voltage-assisted dewetting
procedure used for depositing thin films of compounds 1, 2 and
P3BT/PCP blends: (a) A drop of a dilute solution was placed onto
biased Pt electrodes set on a Si N /Si substrate. (b) After solvent
3 4
evaporation, the photoconductivity of the films was measured between
the electrodes.
mmol), PdCl (PPh ) (0.028 g, 0.04 mmol), triethylamine (2.5
3 2
2
ml) and compound 5 (0.2 g, 0.6 mmol) were placed in a flask
and de-gassed with Ar. The mixture was kept at 75 1C for 15 h.
The solvent was then removed under reduced pressure and the
residue chromatographed on silica gel (petroleum ether :
chloroform = 2 : 1) to give compound 2 (62%) as yellow
1
Acknowledgements
crystals. mp 213–214 1C (MeOH). H NMR (CDCl
3
) d 2.91
(
ddd, 1 H, J ¼ 13.1, 10.3, 5.3 Hz, H-2), 2.97–3.16 (m, 5 H, H-1,
A. T., A. M., S. L. and L. M. gratefully acknowledge financial
support from the M. I. U. R., Rome, Italy. The authors also
thank Dr Eszter Gacs-Baitz (Central Research Institute for
Chemistry, Hungarian Academy of Sciences, Budapest, Hun-
gary) for NMR spectra analyses.
Hs-9, Hs-10), 3.26 (m, 1 H, H-1), 3.66 (ddd, 1 H, J ¼ 13.1,
1
0.4, 2.7 Hz, H-2), 6.48–6.56 (m, 5 H, H-7, H-8, H-12, H-13,
0
H-16), 6.59 (d, 1 H, J ¼ 8.1 Hz, H-5), 6.64 (m, 1 H, H-20 or
0
H-24 ), 7.0 (dd, 1 H, J ¼ 7.8, 1.8 Hz, H-15), 7.34 (m, 1 H, H-
0
0
0
0
0
2
1
0 or H-24 ) and 7.46–7.52 (m, 4 H, H-12 , H-13 , H-15 , H-
0
13
6 ). C NMR (CDCl
3
) d 34.6, 34.8, 35.4, 35.7 (C-1, C-2, C-9,
0
0
0
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30.4 (C-15), 131.5, 131.8 (C-12 , C-13 , C-15 , C-16 ), 131.6,
0
0
0
0
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0
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9
1.50; H, 5.59; N, 2.69%.
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ꢁ1
dimethylformamide (DMF) solution (10 mg ml ), which was
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3
then allowed to dry in vacuo (10 Torr). For the preparation
of the blends, P3BT (1 mg) was dissolved in 1 ml of CHCl
3
.
Compound 1 or 2 was then added to the P3BT solution (10 : 1
w/w). The PCP/P3BT blends were then sonicated for 2 h.
Samples for the photoelectrical study were prepared by
depositing a drop (0.4 ml) of the solutions of compounds 1, 2
and the PCP/P3BT blends, and leaving the solutions to
evaporate in a nitrogen stream while applying a fixed bias
voltage (0 V and þ20 V) (Scheme 2) to platinum patterned
5
6
3 4
electrodes (electrode distance 3 mm), set on a Si N /Si sub-
strate. Photoelectrical measurements were obtained for the
films over several on/off light illumination cycles. The con-
ductivity of the films was monitored as a function of exposure
time through a solar simulator under air mass (AM) 0 condi-
ꢁ2
tions (Xenon lamp) with an input power of 300 mW cm
.
9
42 | New J. Chem., 2006, 30, 939–943 This journal is ꢀc the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2006