Scheme 2. Synthesis of Angled Nanocar 1
Figure 2. (A-C) Three models of possible conformations of 1
represented by material studios (MS) modeling. (D) STM10 image
of 1 shown in A (bias voltage ) -0.71 V, tunneling current ) 7
pA). (E) Higher resolution view of 1, same tunneling parameters.
Our next step was to image the angled nanocar (Figure
2). STM imaging of the molecule revealed that a large variety
With the addition of the axles and the N-alkylated
carbazole, the tetrafullerene (1) proved to be sufficiently
soluble for definitive characterization by 1H NMR, 13C NMR,
and mass spectrometric analysis.8
Hz), 3.97 (t, 2H, J ) 6.53 Hz), 3.86 (t, 2H, J ) 6.33 Hz), 3.74 (t, 2H, J )
6.24 Hz) (the six -OCH2- groups), 2.0-1.1 (m, 196H) (other decyl and
carbazole CH2 groups), 0.99 (t, 3H, J ) 7.35 Hz) (the carbazole CH3),
0.87-0.81 (m, 36H) (six different decyl CH3 groups); 13C NMR (126 MHz
CDCl3) δ 154.6, 154.3, 153.84, 153.76, 153.6, 153.4 (six different signals
from aryloxy C), 151.7, 151.5, 147.7, 147.5, 146.8, 146.52, 146.50, 146.34,
146.33, 145.9, 145.8, 145.7, 145.56, 145.55, 145.5, 144.8, 144.6, 143.3,
142.71, 142.68, 142.24, 142.16, 142.1, 142.0, 141.8, 141.7, 140.5, 140.4,
136.2, 135.3 (30 different fullerene sp2 signals; the two slightly different
fullerene environments cannot be differentiated), 134.4, 131.6, 130.8, 130.0,
124.0, 108.9 (six different C-H groups on the 3,6-disubstituted carbazole
and 1,2,4-trisubstituted phenyl rings, the last signal is C-1 of carbazole),
143.1, 126.5, 125.9, 123.2, 122.6, one signal in the cluster of seven signals
from 115.14 to 113.27 (six different substituted C on the 3,6-disubstituted
carbazole and the 1,2,4-trisubstituted phenyl rings, the first signal is C-8a/
C-9a of carbazole), 117.6, 117.4, 117.2, 117.09, 117.08, 116.8 (six different
C-H groups on three types of tetrasubstituted phenyl rings), 115.1, 114.4,
114.3, 114.2, 114.0, 113.5, 113.3 (six of these seven signals are from six
different alkyne-substituted C on three types of tetrasubstituted phenyl rings),
101.2, 100.2, 97.8, 96.5, 94.4, 93.7, 92.7, 92.3, 91.1, 88.2, 84.5, 80.2 (the
12 different alkyne C; lack of symmetry in the trisubstituted phenyl ring
results in the three groups with two alkynes giving 3 × 4 ) 12 well-resolved
alkynyl signals), 70.1, 69.9, 69.8, 69.6, 69.5, 69.3 (the six different -OCH2-
C), 62.0 (fullerene C-H signal), 55.6 (fullerene sp3 quaternary C), 43.2
(N-CH2- broad signal detected only in the DEPT-135 13C experiment
because of its increased sensitivity), 31.97, 31.96 (×2), 31.9, (four signals
for six C-8 decyl C), 31.1 (N-CH2-CH2-) 30.0, 29.85, 29.83, 29.76, 29.74,
29.714, 29.708, 29.70, 29.65, 29.643, 29.64, 29.636, 29.49, 29.47, 29.44,
29.43, 29.42, 29.41, 29.39, 29.35, 29.3 (numerous signals for six sets of
C-3 through C-7 decyl C), 26.6, 26.23, 26.19, 26.16, 26.1, 26.0 (the six
different -OCH2-CH2- C), 22.8, 22.74, 22.71, 22.69 (four signals for
the six C-9 decyl C), 20.6 (N-CH2-CH2-CH2-), 14.20, 14.18, 14.1 (three
signals for the six C-10 decyl C), 13.9 (N-CH2-CH2-CH2-CH3);
MALDI-TOF MS m/z (silver nitrate as the matrix) calcd for C448H289NO12
5873, found 5873.
(8) Angled Nanocar 1. To an oven-dried 500 mL round-bottom flask
equipped with a magnetic stir bar were added 11 (0.075 g, 0.0250 mmol)
and C60 (0.200 g, 0.278 mmol). After adding THF (250 mL), the mixture
was sonicated for 3 h (general purpose sonicator). To the greenish-brown
suspension formed after sonication was added LHMDS (1.00 mL, 1.00
mmol) dropwise at room temperature over 1 h. As the reaction progressed,
the mixture turned into a deep greenish-black solution. During the addition
of LHMDS, small aliquots from the reaction were extracted and quenched
with trifluoroacetic acid (TFA), dried, and redissolved in CS2 for TLC
analysis (developed in a mixture of CS2, CH2Cl2, and hexanes 2:1:1).
Completion of the reaction was confirmed by the disappearance of the
starting materials. Upon completion, the reaction was quenched with TFA
to give a brownish slurry. Excess TFA and solvent were then removed in
vacuo to afford a crude product that was dissolved in CS2 and directly loaded
onto a column. The column was eluted with CS2/CH2Cl2 (100:1) to remove
unreacted C60, followed by CS2/CH2Cl2 (1:1) for complete removal of trace
C60 and elution of product. The product was further purified using another
flash column with graduated elution of CS2/CH2Cl2/hexanes (4:1:3 then
2:1:1). A third column with elution (2:1:1) was used to complete the
purification to afford 1 (0.015 g, 10%): FTIR 2950, 2922, 2851, 2207,
2151, 1591, 1501, 1461, 1410, 1382, 1277, 1215, 1015, 843, 732, 662 cm-1
;
1H NMR (500 MHz, CDCl3, ppm) δ 8.27 (dd, 2H, J ) 1.51 Hz, J ) 0.5
Hz), 7.67 (dd, 2H, J ) 8.46 Hz, J ) 1.57 Hz), 7.38 (d, 2H, J ) 8.58 Hz)
(aromatic H on 3,6-disubstituted carbazole ring), 7.76 (dd, 2H, J ) 1.66
Hz, J ) 0.59 Hz), 7.54 (dd, 2H, J ) 8.01 Hz, J ) 0.5 Hz), 7.48 (dd, 2H,
J ) 8.03 Hz, J ) 1.66 Hz) (aromatic H on 1,2,4-trisubstituted phenyl ring),
7.29 (s, 2H), 7.13 (s, 2H), 7.07 (s, 2H), 7.04 (s, 2H), 6.96 (s, 2H), 6.94 (s,
2H) (six aromatic H on the three types of tetrasubstituted phenyl rings),
7.18 (s, 4H) (the fullerene C-H), 4.32 (t, 2H) (the carbazole N-CH2-),
4.17 (t, 2H, J ) 6.05 Hz), 4.15 (t, 2H, J ) 6.63 Hz), 4.03 (t, 2H, J ) 6.55
Org. Lett., Vol. 10, No. 2, 2008
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