Fullerene Ylidene Malonate Supramolecular Triads
FULL PAPER
H, ϪN(CH3)2] ppm. 13C NMR (CDCl3): δ ϭ 167.4, 166.2, 164.5, lows. To a stock solution of crown ether (solution A) in MeCN
151.1, 143.1, 131.8, 121.0, 119.6, 112.1, 70.4, 68.8, 68.6, 64.5, 41.2, were added several aliquots of a solution (solution B) made up of
40.3 ppm. UV/Vis (CHCl3/MeCN, 1:1): λmax (ε) ϭ380 nm (20100). the metal salt (at higher concentration) dissolved in solution A, in
MS (EI): m/z (%) ϭ694.5 (41) [M ϩ K]ϩ, 678.6 (100) [M ϩ Na]ϩ.
C31H45NO14 (655.3): calcd. C 56.78, H 6.92, N 2.14; found C 57.05,
H 6.72, N 2.25.
order to maintain the crown ether at the same, constant concentra-
tion. Stock solutions A were in the range 5 ϫ 10Ϫ5 to 8 ϫ 10Ϫ5
,
whereas stock solutions B were in the range 6 ϫ 10Ϫ5 to 2 ϫ 10Ϫ2
for Eu(OTf)3. After each addition, the UV/Vis spectrum in the
250Ϫ700-nm region was recorded, and absorbances at selected
wavelengths were measured. By use of a nonlinear fitting curve
program, the plot of A against the metal concentration x was fitted
by Equation (1), thus affording the value of the association con-
stant ka, where A is the measured absorbance, x is the total concen-
tration of titrant (usually metal salt) added, εc is the molar ab-
sorptivity of the complex, εs is the molar absorptivity of the sub-
strate at the desired wavelength, which could be directly deter-
mined, C is the total concentration of the titrate (which is a
constant quantity, usually the crown ether), and ka is the associ-
ation constant for the 1:1 complex.
General Procedure for the Preparation of Methanofullerenes: A solu-
tion of DBU (0.5 mmol) in toluene (5 mL) was added dropwise to
a solution of the crown ether (0.2 mmol), C60 (0.2 mmol) and I2
(0.2 mmol) in toluene (130 mL). Stirring under nitrogen was con-
tinued for 12 h. The product was purified by column chromato-
graphy (SiO2; toluene, then toluene/iPrOH, 98:2), and then dis-
solved in a minimum amount of CH2Cl2, precipitated with MeOH
and centrifuged. The solvent was then removed and the solid was
dried under high vacuum.
Compound 7a: This compound was produced from crown ether 6a
(77 mg, 0.16 mmol), C60 (115 mg, 0.16 mmol), I2 (41 mg,
0.16 mmol) and DBU (61 mg, 0.4 mmol) and was obtained as a
dark red solid (50 mg, 26%). M.p. Ͼ 250 °C. 1H NMR (CDCl3):
δ ϭ 7.72 (s, 1 H, ϪCHϭCϪ), 7.4 (m, 2 H, ArϪH), 6.65 (m, 2 H,
ArϪH), 4.63 (m, 4 H, ϪCOOCH2CH2OϪ), 4.56Ϫ4.43 (m, 4 H,
ϪCOOCH2CH2OϪ), 4Ϫ3.88 (m, 8 H, ϪCOOCH2CH2OϪ), 3.05
[s, 6 H, ϪN(CH3)2] ppm. 13C NMR (CDCl3): δ ϭ 164.8, 163.4,
152.0, 145.1, 144.6, 144.0, 143.8, 142.9, 142.1, 141.8, 140.8, 139.0,
137.5, 132.1, 119.8, 118.6, 111.5, 69.6, 69.1, 69.0, 68.8, 66.8, 66.4,
65.0, 64.8, 39.9 ppm. UV/Vis (CHCl3/MeCN, 1:1): λmax (ε) ϭ 375
nm (17100).
(1)
Acknowledgments
We thank the University of Pavia for funding (FAR 2000Ϫ2002),
and Prof. M. Maggini (University of Padova, Italy) for useful dis-
cussions regarding this manuscript.
Compound 7b: This compound was produced from crown ether 6b
(90 mg, 0.16 mmol), C60 (150 mg, 0.21 mmol), I2 (43 mg,
0.17 mmol) and DBU (64 mg, 0.42 mmol), and was obtained as a
1
dark red solid (70 mg, 35%). M.p. Ͼ 250 °C. H NMR (CDCl3):
[1] [1a]
[1b]
H. Imahori, Y. Sakata, Adv. Mater. 1997, 9, 537Ϫ546.
δ ϭ 7.72 (s, 1 H, ϪCHϭCϪ), 7.4 (m, 2 H, ArϪH), 6.65 (m, 2 H,
ArϪH), 4.66 (m, 4 H, ϪCOOCH2CH2OϪ), 4.54Ϫ4.39 (m, 4 H,
ϪCOOCH2CH2OϪ), 3.96Ϫ3.73 (m, 16 H, ϪCOOCH2CH2OϪ
and ϪOCH2CH2OϪ), 3.05 [s, 6 H, ϪN(CH3)2] ppm. 13C NMR
(CDCl3): δ ϭ 167.8, 164.8, 163.4, 151.6, 145.3, 145.2, 145.1, 144.9,
144.7 ϫ 3, 144.6, 143.9, 143.6, 143.1, 143.0 ϫ 2, 142.2, 141.9 ϫ 2,
141.0, 139.3, 132.1, 112.1, 71.4, 72.0, 70.8, 70.6, 70.1, 70.0, 69.9,
66.4, 65.7, 64.5, 40.3 ppm. UV/Vis (CHCl3/MeCN, 1:1): λmax (ε) ϭ
375 nm (46100). MS (EI): m/z (%)ϭ 1309.4 (47) [M ϩ Na]ϩ.
´
´
´
N. Martın, L. Sanchez, B. Illescas, I. Perez, Chem. Rev. 1998,
98, 2527Ϫ2547. For recent examples, see:
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Compound 7c: This compound was produced from crown ether 6c
(120 mg, 0.18 mmol), C60 (144 mg, 0.2 mmol), I2 (51 mg, 0.2 mmol)
and DBU (61 mg, 0.4 mmol), and was obtained as a dark red solid
[2b]
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D. M. Guldi, C. Luo, A. Swartz, M. Scheloske, A. Hirsch,
1
(67 mg, 27%). M.p. Ͼ250 °C. H NMR (CDCl3): δ ϭ 7.72 (s, 1 H,
Chem. Commun. 2001, 1066Ϫ1067. [2d] J. L. Segura, N. Martin,
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ϪCHϭCϪ), 7.4 (m, 2 H, ArϪH), 6.65 (m, 2 H, ArϪH), 4.64 (m, 4
H, ϪCOOCH2CH2OϪ), 4.52Ϫ4.38 (m, 4 H, ϪCOOCH2CH2OϪ),
3.93Ϫ3.65 (m, 16 H, ϪCOOCH2CH2OϪ and ϪOCH2CH2OϪ),
3.05 [s, 6 H, ϪN(CH3)2] ppm. 13C NMR (CDCl3): δ ϭ 167.7, 164.8,
163.5, 145.3, 145.3, 145.2, 145.0, 144.8, 144.7, 144.0, 143.1, 143.1,
143.0, 142.3, 141.9, 141.0, 139.2, 139.1, 132.1, 71.5, 70.9, 70.8, 70.8,
70.8, 69.2, 68.9, 68.9, 66.4, 65.0, 65.0, 64.8, 64.7, 64.7, 52.0,
43.3.43.3 ppm. UV/Vis (CHCl3/MeCN, 1:1): λmax (ε) ϭ 375 nm
(39500). MS (EI: m/z (%)ϭ 1397.5 (100) [M ϩ Na]ϩ.
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F. Diederich, C. Thilgen, Science 1996, 271, 317Ϫ323.
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L. Smilowitz, A. J. Heeger, F. Wudl, Science 1992, 258,
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General Procedure for the Determination of the Association Con-
stants: MeCN (Carlo Erba UV/Vis spectroscopic grade) was used
for the determination of the stability constants by UV/Vis spectro-
photometry. A Mettler H31 analytical balance (with a precision of
10Ϫ4 g) was used to weigh the samples for the stock solutions. Ali-
quots of these stock solutions were then taken by high-precision
Hamilton syringes to prepare the cuvette samples for spectrophoto-
metric analyses. The titration experiments were conducted as fol-
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T. Da Ros, M. Prato, D. Guldi, E. Alessio, M. Ruzzi, L.
Pasimeni, Chem. Commun. 1999, 635Ϫ636. For a recent review
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Diederich, Chem. Soc. Rev. 1999, 28, 263Ϫ277.
E. Sartori,
L. Garlaschelli, A. Toffoletti, C. Corvaja, M. Maggini, G. Scor-
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rano, Chem. Commun. 2001, 311Ϫ312.
E. Sartori, A. Tof-
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105, 10776Ϫ10780.
Eur. J. Org. Chem. 2002, 3385Ϫ3392
3391