Supporting Online Material
Encapsulation of Molecular Hydrogen in
Fullerene C60 by Organic Synthesis
Koichi Komatsu*, Michihisa Murata & Yasujiro Murata
Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
e-mail: komatsu@scl.kyoto-u.ac.jp
Contents
Page
Experimental Procedures
S2
Spectroscopic Data
S7
S1/S11
Experimental Procedures
General.
Nuclear magnetic resonance (NMR) spectra were recorded on a Varian Mercury-300
spectrometer (300 MHz for 1H and 75 MHz for 13C NMR) and a JEOL AL-400 spectrometer (100
MHz for
13
C NMR).
UV-3100PC
Ultraviolet-visible (UV-vis) spectra were recorded with a Shimadzu
spectrometer.
Matrix-assisted
laser
desorption/ionization
time-of-flight
(MALDI-TOF) mass spectra were measured with an Applied Biosystems Voyager-DE STR
spectrometer.
Fast atom bombardment (FAB) mass spectra were measured with a JEOL JMS-700
spectrometer. Infrared (IR) spectra were taken on a Shimadzu FTIR-8600 spectrometer.
Cyclic
voltammetry (CV) and differential pulse voltammetry (DPV) were conducted on a BAS
Electrochemical Analyzer CV-100W using a three-electrode cell with a glassy carbon working
electrode, a platinum wire counter electrode, and a Ag/0.01 M AgNO3 reference electrode.
The
potentials were corrected against ferrocene used as an internal standard added after each
meagurement.
The open-cage fullerene encapsulating hydrogen, H2@2, was prepared as reported previously1,2.
Oxidation of H2@2.
A mixture of H2@2 (107 mg, 0.0988 mmol) and m-chloroperbenzoic acid (34 mg, 0.20 mmol) in
200 ml of toluene was stirred at room temperature for 13 hours under nitrogen atmosphere.
The
solvent was evaporated under reduced pressure, and the residual brown solid was washed twice
with 50 ml of methanol and dried under vacuum to give H2@3 (106 mg, 0.0977 mmol, 99%) as a
brown solid.
H2@3: mp > 300 °C; IR (KBr) ν (cm–1) 1746 (C=O), 1073 (S=O); UV-vis (CHCl3) λmax (nm)
(log ε) 258 (5.14), 320 (4.70); 1H NMR (300 MHz, CS2-CD2Cl2 (5:1)) δ (ppm) 8.63 (m, 1H), 8.32
(m, 1H), 8.26-8.23 (m, 2H), 8.05 (m, 1H), 7.68 (m, 1H), 7.42-7.34 (m, 4H), 7.17-7.03 (m, 4H),
–6.18 (s, 2H); 13C NMR (75 MHz, o-dichlorobenzene-d4) δ (ppm) 193.61, 187.54, 167.08, 163.54,
155.72, 154.97, 150.41, 149.06, 148.94, 148.21, 148.00, 147.99, 147.96, 147.79, 147.71, 147.68,
147.40, 147.34, 147.32, 147.14, 147.03, 146.96, 146.89, 146.71, 146.44, 146.29, 146.14, 145.35,
144.27, 143.79, 142.89, 142.54, 142.06, 141.82, 141.79, 141.69, 140.86, 140.81, 140.80, 140.62,
S2/S11
140.46, 140.25, 139.94, 139.79, 139.41, 139.11, 139.05, 138.85, 138.59, 138.58, 138.46, 137.46,
136.01, 135.68, 133.56, 133.08, (132.15, 131.36, 131.29, 131.02, 130.80, 128.87, 128.76), 125.84,
125.09, 122.81, 122.75, 75.10, 52.60 (the signals at the range of δ 132.4–126.8 ppm were
overlapped with the signals of o-dichlorobenzene-d4); high-resolution mass spectrum (HRMS)
(FAB; positive ion mode) calcd for C80H16O3N2S (M+): 1084.0882, found: 1084.0929.
Photochemical desulfurization of H2@3.
A stirred solution of H2@3 (52 mg, 0.048 mmol) in 150 ml of toluene in a Pyrex-glass flask was
irradiated with a Xe-lamp (500 W) placed at the distance of 20 cm at room temperature for 17 hours
under argon atmosphere.
After removal of the solvent under reduced pressure, the residual brown
solid was subjected to flash column chromatography over silica gel.
Elution with CS2-ethyl
acetate (30:1 by volume) gave H2@4 (21 mg, 0.020 mmol, 42%) as a brown solid, and following
elution with CS2-ethyl acetate (10:1 by volume) gave unreacted H2@3 (20 mg, 0.018 mmol, 38%).
H2@4: mp > 300 °C; IR (KBr) ν (cm–1) 1747 (C=O); UV-vis (CHCl3) λmax (nm) (log ε) 257
(5.09), 324 (4.67); 1H NMR (300 MHz, CS2-CD2Cl2 (5:1)) δ (ppm) 8.57 (m, 1H), 8.40 (m, 1H),
8.10-7.99 (m, 3H), 7.82 (m, 1H), 7.40-7.35 (m, 4H), 7.27-7.07 (m, 4H), –5.69 (s, 2H);
13
C NMR
(75 MHz, o-dichlorobenzene-d4) δ (ppm) 196.45, 189.88, 168.35, 163.06, 149.82, 148.75, 148.62,
148.42, 147.66, 147.52, 147.17, 146.88, 146.51, 146.08, 145.92, 145.59, 145.56, 145.55, 145.50,
145.43, 145.38, 145.16, 145.08, 144.95, 144.92, 144.59, 144.47, 143.95, 143.89, 143.73, 142.98,
142.60, 142.41, 142.15, 141.82, 141.72, 141.33, 140.93, 140.64, 140.33, 140.11, 139.96, 139.94,
139.70, 139.66, 139.61, 139.15, 138.43, 137.55, 137.43, 137.25, 136.28, 136.14, 135.72, 133.56,
133.17, (131.46, 131.01, 130.77), 123.31, 122.79, 75.67, 53.01 (the signals at the range of δ
132.4–126.8 ppm were overlapped with the signals of o-dichlorobenzene-d4); HRMS (FAB;
positive ion mode) calcd for C80H17O2N2 (MH+): 1037.1290, found: 1037.1290.
Reductive coupling of the two carbonyl groups in H2@4.
To a stirred suspension of zinc powder (299 mg, 4.57 mmol) in 10 ml of dry tetrahydrofuran was
added titanium tetrachloride (250 µl, 2.28 mmol) drop by drop at 0 °C under argon atmosphere, and
the mixture was refluxed for 2 hours.
A 1-ml portion of the resulting black slurry was added to a
stirred solution of H2@4 (49 mg, 0.048 mmol) in 7 ml of o-dichlorobenzene at room temperature
S3/S11
under argon atmosphere.
After heating at 80 °C for 2 hours, the resulting brownish purple solution
was cooled to room temperature. Then the solution was diluted with 20 ml of o-dichlorobenzene,
and the solution was washed with 50 ml of saturated aqueous solution of NaHCO3.
The organic
layer was dried over MgSO4 and evaporated under reduced pressure to give a residual brown solid,
which was then subjected to flash column chromatography over silica gel. Elution with CS2-ethyl
acetate (20:1 by volume) gave H2@5 (42 mg, 0.042 mmol, 88%) as a brown solid.
H2@5: mp > 300 °C; IR (KBr) ν (cm–1) 1748 (C=N); UV-vis (CHCl3) λmax (nm) (log ε) 262
(5.08), 328 (4.66), 431 (3.33), 532 (3.11); 1H NMR (300 MHz, CS2-CD2Cl2 (5:1)) δ (ppm) 8.74 (m,
1H), 8.04-7.92 (m, 2H), 7.80 (m, 1H), 7.72 (m, 1H), 7.48-7.39 (m, 2H), 7.29-7.12 (m, 7H), –2.93 (s,
2H); 13C NMR (100 MHz, o-dichlorobenzene-d4) δ (ppm) 168.39, 165.87, 149.48, 148.76, 148.41,
145.57, 145.55, 145.48, 145.44, 145.26, 144.69, 144.64, 144.57, 144.53, 144.44, 144.30, 144.28,
144.13, 144.12, 144.10, 144.01, 143.97, 143.92, 143.86, 143.75, 143.69, 143.61, 143.55, 143.52,
143.49, 143.47, 143.45, 143.38, 141.63, 141.12, 141.09, 140.98, 140.84, 140.62, 140.49, 140.26,
139.84, 139.25, 138.95, 138.37, 138.31, 137.26, 137.01, 136.89, 136.78, 136.64, 136.63, 135.68,
135.65, 135.46, 135.23, 134.98, (131.46, 131.02, 128.76, 128.68, 128.66, 127.69, 127.64), 125.55,
125.51, 122.86, 73.70, 56.69 (the signals at the range of δ 132.4–126.8 ppm were overlapped with
the signals of o-dichlorobenzene-d4); HRMS (FAB; positive ion mode) calcd for C80H17N2 (MH+):
1005.1392, found: 1005.1381.
Thermal reaction of H2@5.
A powder of H2@5 (245 mg, 0.244 mmol) lightly wrapped with a piece of aluminum foil was
heated in a glass tube using an electric furnace at 340 °C for 2 hours under vacuum (1 mmHg).
The resulting black solid was dissolved in CS2, and the solution was passed through a glass tube
packed with silica gel (40 g) to afford H2@C60 contaminated with 9% of empty C60 (total weight
118 mg, 0.163 mmol (calculated as H2@C60), 67%) as a brown solid.
Analytically pure H2@C60
was obtained by separation of this product by the use of high-performance liquid chromatography
(HPLC) on a preparative Cosmosil Buckyprep column (25 cm × 10 mm inner diameter × 2, with
toluene as a mobile phase; flow rate, 4 ml min–1) after 20 times recycling.
H2@C60: mp > 300 °C; IR (KBr) ν (cm–1) 1429, 1182, 577, 527; UV-vis (cyclohexane) λmax (nm)
(log ε) 212 (5.14), 258 (5.17), 330 (4.67), 405 (3.42), 543 (2.84), 600 (2.80), 622 (2.52); 1H NMR
S4/S11
(300 MHz, o-dichlorobenzene-d4) δ (ppm) –1.44 (s); 13C NMR (75 MHz, o-dichlorobenzene-d4) δ
(ppm) 142.844; HRMS (FAB; positive ion mode) calcd for C60H2 (M+): 722.0157, found: 722.0163;
Anal. calcd for C60H2: C, 99.72; H, 0.28, found: C, 99.04; H, 0.24.
Solid-state mechanochemical [2+2] dimerization reaction of H2@C60.
H2@C60 (10 mg, 0.014 mmol) and 4-aminopyridine (1.5 mg, 0.016 mmol) were placed in a
stainless-steel capsule together with a stainless-steel milling ball.
The capsule was sealed under
nitrogen, and was vigorously shaken at the speed of 3500 r.p.m. for 30 min by the use of a
high-speed vibration mill at room temperature3,4.
The reaction mixture was dissolved in 4 ml of
o-dichlorobenzene, and the solution was subjected to HPLC on a preparative Cosmosil 5PBB
column (25 cm × 20 mm inner diameter × 2, with o-dichlorobenzene as a mobile phase; flow rate, 3
ml min–1) to give unreacted H2@C60 (6.9 mg, 0.0095 mmol, 69%) and [2+2] dimer (H2@C60)2 (3.0
mg, 0.0021 mmol, 30%) as a brown solid.
(H2@C60)2: mp > 300 °C; IR (KBr) ν (cm–1) 1463.9, 1425.3, 1187.1, 796.5, 770.5, 762.8, 746.4,
710.7, 706.9, 612.4, 574.7, 561.2, 550.6, 544.9, 526.5, 480.2, 450.3, 417.6 (Reported values for
(C60)2; 1463.9, 1425.3, 1188.1, 796.5, 769.5, 761.8, 746.4, 710.7, 705.9, 612.4, 573.8, 560.3, 550.6,
544.9, 526.5, 479.3, 449.4, 418.5)4; 1H NMR (300 MHz, o-dichlorobenzene-d4) δ (ppm) –4.04 (s).
HPLC analysis on a Cosmosil Buckyprep column (25 cm × 4.6 mm inner diameter, with toluene as
a mobile phase; flow rate, 1 ml min–1) exhibited a single peak at exactly the same retention time as
authentic [2+2] dimer (C60)2, 18.7 min4.
Thermal stability of H2@C60.
Powder of H2@C60 (1 mg) was lightly wrapped with a piece of aluminum foil and heated in a
glass tube under vacuum (1 mmHg) using an electric furnace at 500 °C for 10 minutes. The
recovered powder was examined by 1H and
observed. The
13
13
C NMR spectroscopy. No decomposition was
C NMR spectrum (75 MHz, o-dichlorobenzene-d4) exhibited a single signal at
142.844 ppm. corresponding to H2@C60 only.
The
1
H NMR spectrum (300 MHz,
o-dichlorobenzene-d4) exhibited only a single signal at –1.44 ppm.
Analysis by the use of HPLC
on a Cosmosil Buckyprep column (25 cm × 4.6 mm inner diameter, with toluene as a mobile phase;
flow rate, 1 ml min–1) exhibited only one peak at the same retention time as that of C60 (8.0
S5/S11
minutes).
References
1. Y. Murata, M. Murata, K. Komatsu, Chem. Eur. J. 9, 1600 (2003).
2. Y. Murata, M. Murata, K. Komatsu,. J. Am. Chem. Soc. 125, 7152 (2003).
3. G.-W. Wang, K. Komatsu, Y. Murata, M. Shiro, Nature 387, 583 (1997).
4. K. Komatsu. et al. J. Org. Chem. 63, 9358 (1998).
S6/S11
Spectroscopic Data
%T
100
1429.2
1182.3
576.7
90
80
4600
526.5
4000
3000
2000
1500
1000
400
−1
wavenumber / cm
Figure S1 Infrared spectrum (KBr) of H2@C60.
%T
100
80
1429.2
1182.3
575.7
60
40
526.5
20
4600
4000
3000
2000
1500
wavenumber / cm
1000
−1
Figure S2 Infrared spectrum (KBr) of C60.
S7/S11
400
0.5
λmax (log ε)
212 (5.14)
258 (5.17)
330 (4.67)
405 (3.42)
543 (2.84)
600 (2.80)
622 (2.52)
Absorbance
0.4
0.3
x 50
0.2
0.1
0
200
300
400
500
600
700
800
wavelength / nm
Figure S3 Ultraviolet-visible spectrum (cyclohexane) of H2@C60 (3.18 x 10−5 M).
1.0
λmax (log ε)
212 (5.16)
258 (5.18)
330 (4.67)
405 (3.41)
543 (2.86)
600 (2.84)
622 (2.58)
Absorbance
0.8
0.6
0.4
x 50
0.2
0
200
300
400
500
600
700
800
wavelength / nm
Figure S4 Ultraviolet-visible spectrum (cyclohexane) of C60 (5.99 x 10−5 M).
S8/S11
o-dichlorobenzene
H2O
hexane
−1.44 p.p.m.
*
10
8
6
4
*
2
−2
0
−4
−6
−8
−10
δ / p.p.m.
1
Figure S5 H NMR (300 MHz, o-dichlorobenzene-d4) spectrum of H2@C60.
o-dichlorobenzene-d4
* Impurities of the solvent.
142.844 p.p.m.
220
200
Figure S6
180
13
160
140
120
100
80
60
40
20
0
δ / p.p.m.
C NMR (75 MHz, o-dichlorobenzene-d4) spectrum of H2@C60.
S9/S11
a
−1.13
H2@C60
−1.54
−1.99
5 µA
(CV)
−1.16
−1.11
−1.57
−1.52
−2.02
−2.50
2 µA
(DPV)
−1.99
C60
b
−1.15
1
−1
0
−1.56
−2.02
−2
−2.49
V vs Fc/Fc
+
Figure S7 Cyclic voltammetry (CV) and differential pulse voltammetry (DPV).
a, H2@C60 and b, C60: 0.5 mM in o-dichlorobenzene, 0.05 M Bu4NBF4, scan
−1
rate 0.02 V s . Values of potential are read with reference to ferroceneferrocenium couple.
a
−1.07
−1.44
H2@C60
10 µA
+1.62
b
−1.07
−1.44
C60
+1.63
2
1
0
−1
V vs Fc/Fc
+
Figure S8 Cyclic voltammetry (CV). a, H2@C60 and b, C60: 0.5 mM in
1,1,2,2-tetrachloroethane, 0.1 M Bu4NPF6, scan rate 0.02 V s−1. Values
of potential are read with reference to ferrocene-ferrocenium couple.
S10/S11
H2@C60
m/z 722
Relative intensity
H2@C60
714
500
700
900
718
722
1100
726
1300
m/z
Figure S9 Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF)
mass spectrum (positive ionization mode, dithranol matrix) of H2@C60. Inset is
the expanded spectrum.
S11/S11