Synthesis and characterisation of C60 derivatives containing functionalised anthraquinone groups and an unusual fullerene-stabilised cation

Article abstract of DOI:10.1016/S0022-328X(98)00436-7

The ortho-anthraquinonedimethane dienophiles prepared in situ from 1,4-dihydroxy-2,3-bis(bromomethyl)-anthraquinone and 1,4-dimethoxy-2,3-bis(bromomethyl)anthraquinone respectively react with the fullerene C₆₀ to give the anthraquinone derivatives: dihydroxy-anthraquinone-C₆₀ and dimethoxy-anthraquinone-C₆₀. The former compound with sodium butoxide and 15-crown-5 gives the bis(sodium-15-crown-5)dioxo-anthraquinone-C₆₀. The dimethoxy-anthraquinone-C₆₀ reacts with [Ru(PPh₃)₂(NO)Cl] to form the bis-adduct {[η²-(dimethoxy-anthraquinone-C₆₀)][Ru(PPh₃ )₂(NO)Cl]}. The electrochemistry of the dihydroxy- and dimethoxy-anthraquinone-C₆₀ derivatives has been studied by cyclic voltammetry and, in contrast to 1,4-dihydroxy-2,3-dimethylanthraquinone, the compound dihydroxy-anthraquinone-C₆₀ shows two separate one electron oxidations at lower potentials strongly suggesting a relatively rare example of a fullerene stablised cation.

Full text of DOI:10.1016/S0022-328X(98)00436-7

Journal of Organometallic Chemistry 562 (1998) 115–122
Synthesis and characterisation of C60 derivatives containing
functionalised anthraquinone groups and an unusual
fullerene-stabilised cation1
Wolfgang Bidell a, Richard G. Compton b, John C. Eklund b, Malcolm L.H. Green a,*,
Thomas O. Rebbitt b, Adam H.H. Stephens a
a Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR, UK
b Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, UK
Received 9 January 1998; received in revised form 27 January 1998
Abstract
The ortho-anthraquinonedimethane dienophiles prepared in situ from 1,4-dihydroxy-2,3-bis(bromomethyl)-anthraquinone and
1,4-dimethoxy-2,3-bis(bromomethyl)anthraquinone respectively react with the fullerene C60 to give the anthraquinone derivatives:
dihydroxy-anthraquinone-C60 and dimethoxy-anthraquinone-C60. The former compound with sodium butoxide and 15-crown-5
gives the bis(sodium-15-crown-5)dioxo-anthraquinone-C60. The dimethoxy-anthraquinone-C60 reacts with [Ru(PPh3)2(NO)Cl] to
form the bis-adduct {[p2-(dimethoxy-anthraquinone-C60)][Ru(PPh3)2(NO)Cl]}. The electrochemistry of the dihydroxy- and
dimethoxy-anthraquinone-C60 derivatives has been studied by cyclic voltammetry and, in contrast to 1,4-dihydroxy-2,3-dimethy-
lanthraquinone, the compound dihydroxy-anthraquinone-C60 shows two separate one electron oxidations at lower potentials
strongly suggesting a relatively rare example of a fullerene stablised cation. © 1998 Elsevier Science S.A. All rights reserved.
Keywords: Fullerenes; Anthraquinone derivatives; Ruthenium complexes; Electrochemistry
1. Introduction
low solubility, are very difficult to separate and purify
[11–13].
Early studies of the reactions of the fullerene C60
showed the molecule behaved as an electron-poor ’su-
peralkene’ as indicated by its reactivity towards nucle-
ophilic addition, radical addition, addition across the
double bond, formation of exohedral transition metal
complexes and cycloadditions [1–7]. The C60 molecule
is very reactive but its derivatives are normally of low
solubility [8–10] in common organic solvents and they
often reversibly decompose to the very stable C60 [1–7].
Further, the C60 molecule has multiple reactive sites
and mixtures of regio isomers and polyfunctional com-
pounds are formed which, due to their instability and
The electron withdrawing nature of the closed cage
alkene C60 makes it an excellent dienophile for Diels–
Alder [4+2] cycloaddition [1–7]. The [4+2] cycloaddi-
tion involves exclusive addition to the 6–6 bond
[14–21]. However, many Diels–Alder C60-adducts are
often unstable and undergo retro-Diels–Alder reactions
and hence are unsuitable for further reactions [14–21].
However, more stable, non-labile Diels–Alder C60-ad-
ducts are formed when the adduct formation is accom-
panied by stabilisation energy gained by aromatisation.
For example, stable C60 adducts are formed by iso-ben-
zofurans [19] and ortho-quinodimethanes [20,21].
The objective of the work described below was to
prepare relatively stable C60-monoadducts, which could
be used for further chemical reactions, for example to
link C60 in a simple way through bridging groups with
* Corresponding author. Fax: +44 865 272690.
1 Dedicated to Professor Bruce King on the occasion of his 65th
birthday.
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00436-7

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W. Bidell et al. / Journal of Organometallic Chemistry 562 (1998) 115–122
Scheme 1. (i) Br2 in C2Cl4, PhCO3H, then irradiated with an IR lamp, 77%. (ii) K2CO3 in DMF and 2-butanone, add methyltosylate, 75%. (iii)
1,3-Dibromo-5,5-dimethylhydantoine and PhCO3H in CCl4, 91%. (iv) C60, 18-crown-6, and potassium iodide in toluene, reflux. R=H, 83%;
R=Me, 89%. (v) 3 in toluene, add NaOBut in THF with 15-crown-5 at r.t., 97%. (vi) 4 in benzene, add [Ru(PPh3)2(NO)Cl] at r.t., 75%.
chromophoric, electrophoric, or ionophoric fragments.
We identified the two functionalised anthraquinone di-
bromides 1,4-dihydroxy-2,3-bis(bromomethyl)-anthra-
quinone (1) and 1,4-dimethoxy-2,3-bis(bromome-
thyl)anthraquinone (2) as the precursors to unstable
ortho-anthraquinonedimethanes dieneophiles which
were likely to give stable functionalised C60 compounds.
The synthesis and properties of new anthaquinone-C60
derivatives are described below. A communication of
part of this work has appeared [22].
all the other new compounds described below, are given
in the Table 1.
The new functionalised C60-adducts, namely, dihy-
droxy-anthraquinone-C60 (3) and dimethoxy-an-
thraquinone-C60 (4) were prepared by adding a toluene
solution of red 1,4-dihydroxy-2,3-bis(bromomethyl)
anthraquinone 1 and yellow 1,4-dimethoxy-2,3-bis(bro-
momethyl)anthraquinone 2, respectively, to a refluxing
purple solution of C60, 18-crown-6 and potassium io-
dide. After a period of heating, addition of acetone/wa-
ter gave brown precipitates of 3 and 4 in excellent
yields. Analytical and spectroscopic data showed no
evidence for the formation of di-adducts. The solubility
of dihydroxy-anthraquinone-C60 3 is comparable to
that of C60 and dimethoxy-anthraquinone-C60 4 is sig-
nificantly more soluble (ca. 17 mg in 5 ml benzene as
compared with ca. 6 mg in 5 ml benzene).
2. Results and discussion
The compounds 1 and 2 were prepared using sub-
stantially modified literature procedures [23,24] which
are described in the Section 3 and Scheme 1. The
published method to generate ortho-quinodimethanes is
the iodide-induced 1,4-elimination at 1,2-bis(bro-
momethyl)-arene derivatives, which is usually per-
formed in dimethylformamide (DMF) [25,26].
However, since C60 is almost insoluble in DMF, the
synthesis was made in toluene using a suitable crown
ether as phase transfer catalyst for the iodide salt. The
analytical and spectroscopic data characterising 2, and
The 13C{1H}-NMR spectrum of 3 (Fig. 1) and 4 (Fig.
2) both showed the expected 17 fullerene signals consis-
tent with the molecule having C2v symmetry, as well as
additional resonances for the sidechains. At 25°C the
1H-NMR spectrum of 3 showed a broad singlet at 4.68
ppm due to the methylene protons (Ha, He), multiplets
at 8.16 and 7.46 ppm due to the aromatic protons and
a singlet at 13.42 ppm due to the two hydroxyl protons.

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W. Bidell et al. / Journal of Organometallic Chemistry 562 (1998) 115–122
119
Table 1
Analytical and spectroscopic dataa
Compound
Spectroscopic data
3
C 92.2 (92.5), H: 1.0 (1.0). MS (FAB, NOBA
1Hb 4.68 (s, br, CH2); 7.46, 8.16 (m, arom. H, AA%BB%); 13.42 (s, OH).
matrix, toluene): expected [M+ ion not found,
(CS2+C6D5CD3, −38°C): 4.02 (d, 2J=14.5, CH2); 4.98 (d, 2J=14.5, CH2); 7.43, 8.11
(m, arom. H, AA%BB%); 13.48 (s, OH). 13Cc: 37 (s, CH2); 65 (s, sp3 carbons C60);
110–155 (s, 16 C60 and 6 arene side chain signals); 186 (s, CO). IRa: 3450 (vw, w(OH)),
1622 (m, w(CꢀO)), 1585 (m), 1417 (s), 1339 (s), 1266 (s), 1183 (w), 810 (w), 775 (m), 732
(m), 723 (m), 578 (vw), 528 (s). UV–vis (CH2Cl2, nm): 229, 257, 328, 407, 437 (sh),
473, 489, 523 (sh).
only [C60]
+. m.p.:\310°C (dec.)
4
C 91.8 (92.3), H 1.6 (1.4), m.p.:\300°C (dec.). MS 1Hb: 4.33 (s, OCH3); 4.61, 5.43 (s, br, CH2); 8.08–8.10, 8.48–8.52 (m, arom. H,
(FAB, NOBA matrix, toluene): 1014 (4.5%,
AA%BB%). (C6D5CD3, −15°C): 4.00 (s, OCH3); 3.91 (d, 2J=14.2, CH2); 4.93 (d,
2J=14.2, CH2); 7.09–7.11, 8.16–8.19 (m, arom. H, AA%BB%). (C6D5CD3, 92°C): 3.99
(s, OCH3); 4.52 (s, br, CH2); 7.21–7.24, 8.12–8.15 (m, arom. H, AA%BB%). 13Cd: 39 (s,
CH2); 63 (s, OCH3); 66 (s, sp3 carbons C60); 110–160 (s, 20 peaks for C60 and arene
side chain signals); 183 (s, CO). IRa: 1672 (vs, w(CꢀO)), 1594 (m), 1567 (m),1317 (s),
1313 (s), 1255 (vs), 1083 (m), 1115 (w), 1061 (w), 1040 (m), 988 (m), 970 (vw), 952
(w), 800 (vw), 768 (w), 744 (m), 724 (m), 578 (m), 528 (vs). UV–vis (CH2Cl2, nm):
232, 255, 328, 431.
[M]+); 720 (58%, [C60
[M-C60H2]+).
]
+); 292 (100%,
7
C 80.6 (78.4), H 2.6 (3.3), Na 2.3 (3.1) MS (FAB, 1He: 3.64 (s, OCH2); 4.88, 5.20 (s, br, CH2); 7.62, 8.39 (m, arom. H, AA%BB%). IRa:
NOBA matrix, THF): expected [M]+ ion not
found, only 986 [M-2(Na-15C5)]+ and 721
1628 (vw), 1602 (w), 1580 (s), 1351 (s), 1299 (s), 1247 (m), 1119 (s), 950 (m), 860 (vw),
769 (w), 738 (m), 676 (vw), 578 (vw), 528 (s). UV–vis (THF, nm): 257, 288 (sh), 327,
404, 435, 489, 525, 573, 616.
[C60H]+
.
8
C 80.6 (80.3), H 2.6 (2.6), Cl 2.0 (2.1), N 0.7 (0.8) 1Hf: 3.98 (s, OCH3); 3.54, 4.92 (s, br, CH2); 7.12 (m, P(C6H5)3); 7.63–7.82, 8.11–8.18
(m, arom. H, AA%BB%). 31P-NMR (81 MHz, toluene-D8, 25°C): 25.0 (s, br) IRa: 1785
(m, w(NO)), 1756 (w, sh), 1672 (s, w(CꢀO)), 1593 (w), 1568 (w), 1316 (s), 1255 (s), 1186
(vw), 1159 (vw), 1093 (w) 1040 (w), 988 (w), 970 (vw), 952 (vw), 768 (vw), 7.42 (s),
723 (s), 693 (m), 579 (vw), 527 (s), 521 (s).
a Analytical data given as found (calc.)%. NMR data given as: chemical shift (ppm) [multiplicity (J in Hz), assignment]. Infrared data, in Nujol
mull, cm−1
.
b 300 MHz, CS2+C6D5CD3, 25°C.
c 75.4 MHz, CS2 (D2O, external), 25°C.
d 125 MHz, CS2+CD2Cl2, 25°C.
e In THF-d8, 50°C.
f 250 MHz, toluene-D8, 25°C.
The broad singlet for the methylene protons Ha, He
suggested a low conformational inversion barrier on the
1H-NMR time scale (Fig. 3). Indeed, variable tempera-
ture experiments showed the two signals for Ha and He
coalesced at ca. 6°C and on cooling to −40°C resolved
into two doublets at 4.98 and 4.02 ppm with a geminal
coupling constant of 14.5 Hz (Fig. 3). At r.t., the
different fine structure for the adducts.
Cyclic voltammetry investigations were undertaken
on 3 and 4 as well as the related analogues 5 and 6
shown in Scheme 2. The experiments were conducted in
dichloromethane solvent containing 0.1 M tetrabuty-
lammonium perchlorate as the supporting electrolyte
using platinum electrodes in the form of either mi-
crodisc electrodes (of radius ca. 30 mm) or flag elec-
trodes of traditional dimensions (3 mm).
Dihydroxy-anthraquinone-C60 3 was found to show
two separate one electron oxidations at potentials of
+0.49 and +0.82 V (vs SCE), respectively. However,
the related analogue 5 showed a single two electron
oxidation wave with a halfwave potential of +1.51 V
(vs SCE). This may be attributed to the reaction shown
in Scheme 2. The cyclic voltammetry studies confirmed
the production of H+. Tafel analysis showed the oxida-
tion to be electrochemically irreversible (Tafel slope 120
mV per decade). The contrast in the oxidation be-
haviour with 3 is intriguing. The significant decrease in
1H-NMR spectrum of dimethoxy-anthraquinone-C60
4
showed two separate peaks for the methylene protons
(Ha, He) at 4.93 and 3.91 ppm which resolved on
cooling to −15°C into two doublets with a geminal
coupling constant of 14.2 Hz. On heating the NMR
sample, the coalesce temperature occurred at ca. 50°C
and on heating to 90°C, the methylene protons showed
a broad singlet at 4.52 ppm.
The UV–vis spectra (CH2Cl2) of dihydroxy-an-
thraquinone-C60 3 and dimethoxy-anthraquinone-C60
4
all exhibit typical peaks assignable to the fullerene
moiety at ca. 220, 255 and 330 nm. In addition, there is
a broad absorption at 450–600 nm which exhibits

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W. Bidell et al. / Journal of Organometallic Chemistry 562 (1998) 115–122
groups cause a greater distance between the 9, 10
positions in the anthraquinone unit and the C60 frag-
ment. In consequence, there would be a reduced
through-space electronic interactions. Neither com-
pounds 4 nor 6 display any oxidative voltammetry.
The compounds 3 and 4 could not be chro-
matographed on silica gel or silylated silica gel and
chromatography on alumina led to an irreversible for-
mation of a bright red material. However, dimethoxy-
anthraquinone-C60 4 could be converted quantitatively
into dihydroxy-anthraquinone-C60 3 by ether cleavage
using BBr3 in o-dichlorobenzene.
Treatment of dihydroxy-anthraquinone-C60 5 with
two equivalents of sodium tert-butoxide in toluene gave
a insoluble dark blue precipitate presumed to be bis(-
sodium)dioxo-anthraquinone-C60,which is sparingly sol-
uble in THF. Addition of 15-crown-5 increased the
solubility and the dark blue compound bis(sodium-15-
crown-5)dioxo-anthraquinone-C60 7 could be precipi-
1
tated by addition of pentane. The H-NMR spectrum
of 7 at 50°C showed bands assignable to the methylene
protons at 5.20 and 4.88 ppm which indicated that the
conformational inversion does not occur below this
temperature. No reaction was observed between 3 and
an excess of 1,8-bis(dimethylamino)naphthalene (’pro-
ton sponge’).
Fig. 3. The two possible boat conformers of the anthraquinone-C60
derivatives with their coalescence temperature (Tc). (i) R=H. Tc=
6°C; R=Me. Tc=50°C.
the potentials suggests there is an appreciable stabilisa-
tion of the intermediate radical cation and the product
quinonoid forms, presumably due to a through-space
overlap of molecular orbitals of the C60 unit with those
on the aromatic ligand. Under cathodic conditions two
reversible one-electron waves were seen at potentials of
−0.72 and −1.22 V (vs SCE), respectively.
It has been previously shown that C60 reacts with
[Ru(PPh3)2(NO)Cl] to give the crystalline adduct {(p2-
C60)[Ru(PPh3)2(NO)Cl]} [27] and attempts were made
to prepare analogues with 4. [Ru(PPh3)2(NO)Cl] was
found to react with 4 in benzene to give olive green
{[p2 - (dimethoxy - anthraquinone - C60)][Ru(PPh3)2(NO)
Cl]}8 which was moderately soluble in aromatic sol-
vents. The spectroscopic properties of 8 were very
similar to those of 4 and {(p2-C60)[Ru(PPh3)2(NO)Cl]}.
The dimethoxy analogues were also investigated.
Compound 4 displayed reduction peaks which are a
superposition
of
1,4-dimethoxy-2,3-dimethylan-
thraquinone (6) and pure C60. These show a one elec-
tron reduction with a halfwave potential at −1.05 V
(vs SCE) and at −0.49, −0.88 and −1.33 V (vs
SCE), respectively. That the reduction potential of the
anthraquinone unit is essentially unchanged between
the ligand and the C60 adduct may arise if the methyl
1
Thus the H-NMR spectrum of 8 showed broad sing-
lets for the methylene protons (Ha, He) at 3.54 and
4.92 ppm, a singlet at 3.98 ppm due to the met-
hoxy protons, a multiplet at 7.12 ppm due to the
PPh3 protons and multiplets between 7.63–7.83 and
Scheme 2. Electrochemical processes for 3 and 5.

W. Bidell et al. / Journal of Organometallic Chemistry 562 (1998) 115–122
121
8.11–8.18 ppm. The 31P{1H}-NMR spectrum showed a
broad band at 25.0 ppm due to the PPh3 groups in the
mixed substituted C60 compound. The IR spectrum of 6
showed a broad peak at 1785 cm−1 assignable to w(NO)
which is at exactly the same frequency as that for for
{(p2-C60)[Ru(PPh3)2(NO)Cl]}. The relative positions of
attachment of the anthraquinone and ruthenium moi-
eties on the fullerene cage could not be ascertained as
low solubility prevented successful acquisition of 13C-
NMR data or crystal growth.
The compounds [Ru(PPh3)2(NO)Cl] [28–31] 1,4-di-
hydroxy-2,3-dimethylanthraquinone [23,24] and 1,4-
dimethoxy-2,3-dimethylanthraquinone [23,24] were
prepared as described. The published procedures [23,24]
for 1 and 2 have been modified.
3.2. Synthesis of 1,4-dihydroxy-2,3-bis(bromomethyl)
anthraquinone 1
A solution of bromine (2.00 ml, 38.82 mmol) in
tetrachloroethylene (15 ml) was added dropwise to a
hot solution (110°C) of 1,4-dihydroxy-2,3-dimethylan-
thraquinone (2.50 g, 9.32 mmol) in tetrachloroethylene
(120 ml) containing benzoyl peroxide (100 mg) under
irradiation with an IR lamp. Irradiation and heating
were continued for 36 h, at the end of which, upon
cooling, the dibromide was separated as dark red crys-
tals. These were extracted with cold chloroform (in
total 1.5 l). The volume of the extract was reduced and
cooled to −80°C to give 1,4-dihydroxy-2,3-bis(bro-
momethyl)anthraquinone as dark red crystals. Yield,
3.06 g (77%).
3. Experimental
3.1. General
All operations were carried out under an atmosphere
of dinitrogen using standard Schlenk-line techniques or
in a dinitrogen glove box. Solvents were dried and
freshly distilled before use. All solvents were thoroughly
degassed by repeated evacuation and re-admission of
the inert gas on the Schlenk-line.
NMR spectra were recorded either on a Bruker AM
300, Bruker AC 250 or a Bruker AMX 500 spectrome-
ter. Spectra were referenced internally using the residual
protio solvent relative to tetramethylsilane (l=0 ppm).
All chemical shifts are quoted in ppm and coupling
constants are in Hz. Infrared spectra were recorded on
a Perkin-Elmer 1510 F.T. Interferometer in the range
4000–400 cm−1. All samples were prepared as Nujol
mulls between KBr plates. FAB-Mass spectra were
recorded in the EPSRC Mass Spectrometry Service
Centre, University of Wales, Swansea. UV–vis spectra
were recorded on a Lambda 6 Perkin Elmer spectrome-
ter in 1 cm quartz cells. Melting points were recorded
on a Gallenkamp melting point apparatus and are
uncorrected. Elemental analyses were performed by the
Microanalytical Department of Inorganic Chemistry
Laboratory, University Oxford. The fullerene C60 was
synthesised using the arc evaporation of graphite in a
dynamic atmosphere of helium ca. 150 mmHg using
3.3. Synthesis of 1,4-dimethoxy-2,3-bis(bromomethyl)
anthraquinone 2
A
suspension of 1,4-dimethoxy-2,3-dimethylan-
thraquinone (2.00 g, 6.75 mmol), 1,3-dibromo-5,5-
dimethylhydantoine (2.00 g, 7.00 mmol) and benzoyl
peroxide (100 mg) in carbontetrachloride (100 ml) was
refluxed under irradiation, using an IR lamp, for 12 h.
After the mixture cooled, the succinimide was filtered
off, and the solvent was removed from the yellow
solution under reduced pressure. The yellow residue
was extracted with carbontetrachloride (10×10 ml) to
separate the succinimide. Evaporation of solvent from
the extract and crystallisation of the resulting yellow
residue from CH2Cl2 (50 ml) and pentane (150 ml) at
−80°C gave bright yellow needles. Yield, 2.79 g (91%).
3.4. Synthesis of dihydroxy-anthraquinone-C60
3
variable power supply at ca. 40 V/200
A
DC).Separation of the C60 and the higher fullerenes
from the amorphous carbon matrix (soot) generated
during evaporation (ca. 15 g) was achieved by column
chromatography of the soot with hexane using an
adapted Soxhlet method. After evaporation of the sol-
vent of the hexane-C60, was extracted with CS2, filtered
and evaporated to dryness. The black C60 was sonicated
five times in ca. 25 ml pentane, filtered and dried in
high vacuo (10−4–10−5 Torr) at 200°C for 48 h. The
yield of C60 was typically 2–4% and a typical experi-
ment gave ca. 100–150 mg. For all reactions the iso-
lated C60 or its derivatives were dissolved overnight in
the chosen solvent and the solution was filtered (typi-
cally there was ca. 5% insoluble material).
A purple toluene solution of C60 (500 mg, 0.695
mmol), 18-crown-6 (1.84 g, 6.95 mmol) and potassium
iodide (254 mg, 1.53 mmol) under reflux was treated
very slowly with a red toluene solution of 1,4-dihy-
droxy-2,3-bis(bromomethyl)-anthraquinone (326 mg,
0.765 mmol). The resulting brown reaction mixture was
refluxed for 8 h, the volume of the solution reduced in
vacuo (to ca. 150 ml) and the product was precipitated
by addition of 500 ml of an acetone-water mixture
(20:1). The resulting brown precipitate was washed with
acetone (3×500 ml), then pentane (2×100 ml) and
dried in vacuo. Yield, 569 mg (83%). The compound is
soluble in CS2, toluene and benzene, sparingly soluble
in CH2Cl2 and insoluble in polar solvents.

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W. Bidell et al. / Journal of Organometallic Chemistry 562 (1998) 115–122
Acknowledgements
3.5. Synthesis of dimethoxy-anthraquinone-C60
4
We thank the Swiss Nationalfonds and the Royal Soci-
ety for supporting W. Bidell and we also wish to thank
the St. John’s College for a scholarship to T.O. Rebbitt.
A purple solution of C60 (235 mg, 0.326 mmol),
anhydrous potassium iodide (117 mg, 0.705 mmol) and
18-crown-6 (860 mg, 3.26 mmol) in toluene (200 ml)
under reflux was treated in a dropwise manner with a
yellow toluene solution (50 ml) of 1,4-dimethoxy-2,3-
bis(bromomethyl)anthraquinone (160 mg). The result-
ing dark brown reaction mixture was refluxed for 12 h.
The solvent was concentrated to 50 ml giving a colour-
less precipitate. This was filtered off and addition of
acetone (250 ml) to the filtrate gave a brown precipi-
tate. This was washed with acetone (5×250 ml), then
with pentane (3×100 ml) and dried in vacuo. Yield,
295 mg (89%). The compound is soluble in CS2, o-
dichlorobenzene, toluene and benzene, and moderately
soluble in CH2Cl2 and insoluble in THF, ether, acetone
and water. Compared with dihydroxy-anthraquinone-
C60 the solubility is much greater, in aromatic solvents,
CS2 and CH2Cl2.
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anthraquinone-C60
7
A
reddish brown solution of dihydroxy-an-
8
[12] T. Suzuki, Q. Li, K. Khemani, F. Wudl, O. Almarson, Science 254
thraquinone-C60 (100 mg, 0.101 mmol) in toluene (250
ml) was treated with a THF solution (50 ml) of sodium
tert-butoxide (20 mg, 0.208 mmol) and 0.1 ml (0.5
mmol) of 15-crown-5 at r.t. and the mixture was stirred
overnight. During the addition, the colour of the reac-
tion mixture changed from reddish brown over deep
red to dark blue. The solvent was evaporated in vacuo,
the dark blue residue was extracted with ca. 300 ml
THF. The extract was filtered and the filtrate was
concentrated under reduced pressure. Addition of pen-
tane (200 ml) precipitated the dark blue product. This
was washed with pentane (3×100ml) and dried in
vacuo. Yield, 144 mg (97%). The compound is slightly
soluble in THF, very sparingly soluble in acetonitrile
and insoluble in aromatic solvents, CS2, CH2Cl2 and
pentane.
(1991) 1186.
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Chem. Soc. 115 (1993) 4919.
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3.7. Reaction of dimethoxy-anthraquinone-C60 with
bis(triphenylphosphine)nitrosylchlororuthenium 8
To a dark brown benzene solution (75 ml) of
dimethoxy-anthraquinone-C60 (85 mg, 0.084 mmol) was
added dropwise at r.t. a green benzene solution (20 ml)
of bis(triphenylphosphine) ruthenium nitrosyl chloride
(58 mg, 0.084 mmol). The resulting black olive green
solution was stirred for 48 h at r.t. The reaction mixture
was then reduced in volume and pentane was added
giving an olive green precipitate. This was washed with
pentane and dried in vacuo. Yield, 108 mg (75%). The
compound is fairly soluble in aromatic solvents.
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1.