Magnetic properties and stability of negatively charged doubly bonded C1202- dimers

Article abstract of DOI:10.1039/c1nj20074g

A new ionic complex {(MDABCO⁺)·Zn^IITMPP} ₂·(C₁₂₀^2-)·(C₆H ₄Cl₂)_2.15·(C₆H ₅CN)_1.85 (1) (Zn^IITMPP: zinc(ii) tetrakis(4-methoxyphenyl)porphyrin; MDABCO⁺: the cation of N-methyldiazabicyclooctane) has been obtained as single crystals. The complex contains negatively charged doubly bonded C₁₂₀^2- dimers whose magnetic properties have been studied. Magnetic moment of the complex is 2.69 μ_B at 290 K indicating presence of about two spins per dimer. The dimers show narrow doublet-like EPR signal with g_M = 2.0014 and the linewidth of 0.315 mT at 290 K. The data of SQUID measurements for 1 can be fitted according to the Heisenberg model for isolated antiferromagnetically interacting spin pairs with exchange interaction of J/k_B = -44.7 K. The EPR signal from the dimers and magnetic susceptibility of 1 decrease below 40 K resulting in diamagnetic dilution of the sample and the appearance of triplet features of the signal. Two pairs of lines show peak separation of 5.2 and 2.6 mT and are centered at g_T = 2.0008. Averaged separation of 10.2 A between two spins was estimated. Additional narrow doublet-like signal is manifested at 40 K and below. The signal was centered at g_I = 1.9984 (20 K) and was attributed to the impurity of non-dimerized C ₆₀^- since its intensity did not exceed 4% from that of the signal from the dimers. Heating of 1 above 380 K resulted in irreversible dissociation of the C₁₂₀^2- dimers to monomeric C ₆₀^- which was accompanied by transition from narrow to broad EPR signal. The degree of dimer-monomer conversion was 97.5% at 446 K.

Full text of DOI:10.1039/c1nj20074g

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PAPER
Magnetic properties and stability of negatively charged doubly bonded
C120 dimersw
2À
Dmitri V. Konarev,*a Salavat S. Khasanov,b Akihiro Otsuka,c Hideki Yamochi,c
Gunzi Saitod and Rimma N. Lyubovskayaa
Received (in Montpellier, France) 27th January 2011, Accepted 18th May 2011
DOI: 10.1039/c1nj20074g
A new ionic complex {(MDABCO+)ÁZnIITMPP}2Á(C1202À)Á(C6H4Cl2)2.15Á(C6H5CN)1.85 (1)
(ZnIITMPP: zinc(II) tetrakis(4-methoxyphenyl)porphyrin; MDABCO+: the cation of
N-methyldiazabicyclooctane) has been obtained as single crystals. The complex contains
2À
negatively charged doubly bonded C120 dimers whose magnetic properties have been studied.
Magnetic moment of the complex is 2.69 mB at 290 K indicating presence of about two spins per
dimer. The dimers show narrow doublet-like EPR signal with gM = 2.0014 and the linewidth of
0.315 mT at 290 K. The data of SQUID measurements for 1 can be fitted according to the
Heisenberg model for isolated antiferromagnetically interacting spin pairs with exchange
interaction of J/kB = À44.7 K. The EPR signal from the dimers and magnetic susceptibility of 1
decrease below 40 K resulting in diamagnetic dilution of the sample and the appearance of triplet
features of the signal. Two pairs of lines show peak separation of 5.2 and 2.6 mT and are
centered at gT = 2.0008. Averaged separation of 10.2 A between two spins was estimated.
Additional narrow doublet-like signal is manifested at 40 K and below. The signal was centered
À
ꢀ
at gI = 1.9984 (20 K) and was attributed to the impurity of non-dimerized C60 since its
intensity did not exceed 4% from that of the signal from the dimers. Heating of 1 above 380 K
2À
À
ꢀ
resulted in irreversible dissociation of the C120 dimers to monomeric C60 which was
accompanied by transition from narrow to broad EPR signal. The degree of dimer-monomer
conversion was 97.5% at 446 K.
two-dimensional polymers formed by C604À in Na4ÁC60.6 Two
Introduction
C–C bonds between fullerenes are fÀormed via the [2+2]
cycloaddition. For example, the C60 anions form linear
metallic polymers in MÁC60 phases (M = K, Rb and Cs) in
Interest to ionic fullerene compounds has been evoked by their
magnetic, conducting and optical properties.1–3 Among a wide
variety of dimeric and polymeric structures of negatively
charged fullerenes some show promising physical properties.4–7
Fullerenes in these structures are linked by one or two
intercage C–C bonds. Polymers bonded by single C–C bonds
are formed in the salts containing di-, tri- and tetraanions of
À
which each C60 forms four C–C bonds with neighbours.7
Formation of polymers through the [2+2] cycloaddition was
also observed when neutral fullerenes were treated at high
pressure and temperature.8
Fullerene dimerization is also accompanied by formation of
one or two intercage C–C bonds. Neutral fullerenes form only
doubly bonded C120 dimers.9 On the contrary, negatively
charged fullerenes generally form diamagnetic singly bonded
3À
fullerenes. Those are linear polymers formed by C60 in the
Na2RbÁC60 and Li3CsÁC60 phases,4 zig-zag polymers formed
by C702À in the MÁC70ÁnNH3 salts (M = Ca, Sr, and Ba)5 and
2À
C120 dimers (Fig. 1a) which dissociate even at 140–250 K
a Institute of Problems of Chemical Physics RAS, Chernogolovka,
Moscow region, 142432, Russia. E-mail: konarev@icp.ac.ru;
Fax: +7-49652-21852
and cannot be observed at room temperature.10 Recently ionic
{(MDABCO+)ÁCoIITMPP}2Á(C1202À)Á(C6H4Cl2)2.5Á(C6H5CN)1.5
complex (2) (CoIITMPP: cobalt(II) tetrakis(4-methoxyphenyl)-
porphyrin; MDABCO+: the cation of N-methyldiazabicyclo-
octane) has been synthesized.11 The complex contains a new
type of negatively charged dimers, in which fullerene anions
are bound by two intercage C–C bonds (Fig. 1b). Analysis of
magnetic properties of these dimers showed that in contrast
b Institute of Solid State Physics RAS, Chernogolovka, Moscow
region, 142432, Russia
c Research Center for Low Temperature and Materials Sciences,
Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
d Research Institute, Meijo University, 1-501 Shiogamaguchi,
Tempaku-ku, Nagoya, 468-8202, Japan
w Electronic supplementary information (ESI) available: Spectra of
the complex 1 in IR ranges. CCDC reference number 735312. For ESI
and crystallographic data in CIF or other electronic format see DOI:
10.1039/c1nj20074g
2À
to the diamagnetic single-bonded C120 dimers, they contain
unpaired spins. However, the presence of paramagnetic
c
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2. Crystal structure
Crystal structure of 1 was studied at 120(2) K. The monoclinic
unit cell of the structure contains two double C–C bonded
2À
C120 dimers lying on a inversion center (Fig. 1b and 2,
ellipsoids are shown with 20% probability) and four cations
coordinated to metalloporphyrin by free nitrogen atom:
(MDABCO+)ÁZnTMPP (Fig. 2). Solvent molecules occupy
two positions. One position is occupied by the C6H4Cl2
molecules, and the other position is shared by both C6H4Cl2
and C6H5CN molecules at 0.075(6)/0.925(6) ratio. Such
a composition assumes non-integer content of solvent in
1: 2.15(C6H4Cl2) : 1.85(C6H5CN). A 2 : 1 ratio between the
MDABCO+ cations and the C1202À dimers corresponds to À2
formal charge on the dimer. This conclusion is justified by
IR- and visible-NIR spectra. The dimer has approximate
(non-crystallographic) D2h symmetry, the length of the intercage
C–C bonds is 1.607(6) A and the center-to-center distance
between fullerenes in the dimer is 9.046 A. Similar length of
the intercage C–C bond and center-Àto-center distance were
)
dimer in 2.11 The
2
2À
Fig. 1 (a) Singly bonded C1202À dimer10b and (b) doubly bonded C120
dimer in 2.11
CoIITMPP in 2 does not allow investigating intrinsic magnetic
properties of these dimers because of strong exchange inter-
2À
action between C120 and CoIITMPP resulting in formation
found for the doubly bonded (C60
of a system of four strongly antiferromagnetically interacting
S = 1/2 spins.11
observed length of the intercage C–C bond is only slightly
longer than that in neutral doubly bonded C120 dimer and the
We have obtained a new {(MDABCO+)ÁZnIITMPP}2Á
(C1202À)Á(C6H4Cl2)2.15Á(C6H5CN)1.852À complex (1), which
also contains doubly bonded C120 dimers. The IR- and
UV-visible-NIR spectra of these dimers are discussed.
ZnIITMPP is diamagnetic and EPR silent allowing one to
study the intrinsic magnetic properties of the dimers by EPR
and SQUID techniques. The dissociation temperature for the
dimers is determined and compared with those of other fullerene
dimers.
2À
singly bonded C120
dimer (1.575(7)9 and 1.597(7) A,10b
respectively). The center-to-center distance is noticeably shorter
than that in the singly bonded C120 dimer (9.28 A).10b
2À
Each C120
dimer is surrounded by six (MDABCO+)Á
2À
ZnTMPP units (four such units are shown in Fig. 2). Two
units are facing the dimer by slightly concave porphyrin
surface and four units by the MDABCO+ cations. The shortest
ZnÁ Á ÁC(C1202À) distance of 3.02–3.17 A indicates absence of
coordination between metalloporphyrin and fullerene dimer.
However, multiple van der Waals N, CÁ Á ÁC(C1202À) contacts
2À
between the plane of the porphyrin macrocycle and C120
Results and discussion
provide p–p interaction between them. A relatively long
ZnÁ Á ÁC(C1202À) distance is a result of the coordination of
MDABCO+ to ZnTMPP. The N(MDABCO+)Á Á ÁZn distance
is rather short (2.280(4) A) and the displacement of the Zn atom
from the plane of four nitrogen atoms towards MDABCO+ is
1. Synthesis
The crystals of 1 were obtained by diffusion technique. In contrast
to previously described complex 2 which was prepared as a
single phase,11 complex 1 was obtained as a mixture of two
phases (total yield is about 70%). The first minor phase (from
5 to 40% of the total amount of crystals) was obtained as good
quality well-shaped elongated parallelepipeds. The second
major phase contained hexagonal prisms. The surface of the
prisms had low quality, even just prepared, and crystals
degraded quickly. The parallelepipeds were separated from
prisms under microscope in a glove box. The parallelepipeds
were tested by X-ray diffraction which showed them to be
isostructural to 2 and have the {(MDABCO+)ÁZnIITMPP}2Á
(C1202À)Á(C6H4Cl2)2.15(C6H5CN)1.85 composition (1). Prisms
did not reflect in the X-ray diffraction experiment. The
loss of crystallinity probably due to elimination of solvent
molecules. According to SQUID and EPR measurements they
are diamagnetic and EPR silent in the 2–300 KÀrange and
perhaps contain diamagnetic singly bonded (C60
) dimers.
2
In contrast to prisms parallelepipeds manifest intense
narrow EPR signal from room temperature (290 K) and down
to 4 K. Therefore, parallelepipeds and prisms can be
distinguished not only by shape, but by the difference in
X-ray diffraction and EPR as well.
Fig. 2 Fragment of crystal structure of 1 showing the cage from the
(MDABCO+)ÁZnTMPP units accommodating the doubly bonded
C120 dimer. Only major occupied orientation of MDABCO+ is
2À
shown.
c
1830 New J. Chem., 2011, 35, 1829–1835
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0.265 A, whereas such displacement from the 24-atom porphyrin
plane is 0.430 A.
3. IR- and UV-visible-NIR spectra of 1
Detailed IR-spectrum of 1 is listed in the ESI.w Neutral doubly
bonded C120 dimer has lower symmetry than pristine C60 and,
in addition to the regular C60 bands at 527, 575, 1186 and
1426 cmÀ1, shows new bands at 420, 479, 549, 612, 709, 726,
2À
769, 796, 1462 cmÀ1.9 Formation of negatively charged C120
dimers in 1 shifts the band of C120 at 1426 to 1387 cmÀ1. The
band of the neutral C120 dimer at 575 cmÀ1 is at the same
position in spectrum of 1 but is split into three components
and has significantly higher intensity than the band at
527 cmÀ1. Such changes are similar to those observed for the
À 12
ꢀ
formation of C60
indicating that fullerenes in the dimers
are negatively charged. Additional bands in the spectrum of
C1202À at 420, 482, 546, 714, 794, 1462 cmÀ1 can be attributed
to symmetry forbidden silent modes of C60 which appear due
to the breaking of C60 symmetry at dimerization. They have
close positions to those observed in the spectrum of the neutral
C120 dimer.9
Spectrum of 1 in the UV-visible-NIR range is shown in
Fig. 3. The doubly bonded C120 dimers manifest broad
absorption bands at 950 and 1070 nm, which are characteristic
À
of fullerene anions.13 Dimeric C120 species photogenerated
in solution from neutral C120 show absorption band at
1020 nm.14 The absorption bands in the visible range were
attributed to ZnIITMPP. Those are intense Soret band at
440 nm and Q-bands at 566 and 609 nm (Fig. 3).
ꢀ
4. Magnetic properties
EPR spectra of 1 were measured for one single crystal tested
by X-ray diffraction and for one polycrystalline sample. Both
spectra are similar and contain the same set of lines down to
4 K. Therefore the EPR responses of bulk sample and single
crystal are identical. The admixture of second phase (prisms) if
present in the polycrystalline sample will not contribute to the
EPR signal since this phase is diamagnetic and EPR silent.
Narrow intense doublet-like signal with gM = 2.0014 and line
width (DH) of 0.315 mT is observed for bothꢀsamples at room
temperature, RT = 290 K (Fig. 4a). The C60 À radical anions
exhibit at RT broad EPR signals (DH = 3–6 mT), which
Fig. 4 EPR signal from a polycrystalline sample of 1 at: (a) 290 K;
(b) 40 K (below the fitting of signal by two lines is shown, for their
attribution see text); (c) 20 K (the scheme for the determination of the
constant of dipole splitting D for triplet signal.
become narrower with decreasing temperature,3,13 whereas the
radical anions of fullerene derivatives exhibit narrow EPR
signals even at RT.15 The doubly bonded C1202À dimer previously
observed in 2 is also a fullerene derivative (the product of
addition of one fullerene to another). Nevertheless, it showed
a broad EPR signal in 2 at RT (DH = 3.46 mT).11 It is
possible that the broadness of this signal is a result of
strong antiferromagnetic exchange interaction realized between
Fig. 3 UV-visible-NIR spectrum of 1 in KBr pellet in the 275–1600 nm
range.
c
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C1202À and CoIITMPP. Absence of such interaction in 1 due to
diamagnetic ones. Diamagnetic dilution results in manifestation of
diamagnetism of ZnIITMPP allows narrow EPR signal from
triplet features of the signals both in the EPR spectra of
polycrystalline sample and single crystal. At 20 K when
intensity of the major signal from the dimers decreases by a
factor of 4, the triplet features are well resolved (they are even
more pronounced for the spectrum of arbitrary oriented single
2À
C120 to be observed.
Intense major line from the dimers is observed down to low
temperatures (this line is labeled as gM in the spectra of
polycrystalline 1 at 290, 40, 20 K (Fig. 4) and a single crystal
of 1 at 20 and 4 K (Fig. 5)). The g-factor and linewidth of
this line are nearly temperature independent down to 4 K.
However, its intensity reaches maximum at 40 K and rapidly
decreases below this temperature.
2À
crystal of 1, Fig. 5). Therefore, triplet features for the C120
dimers can be observed in solid state only for diamagnetically
diluted samples. The use of diamagnetically diluted samples to
minimize the effects of intermolecular contribution among the
paramagnetic centers is a common practice in the study of
biradicals. Concentrated samples (crystals) can frequently
show doublet-like lines, for example dianion of anthracene
with triplet state or exchange coupled copper(II) nitroxide
clusters.17 In the latter case diamagnetic dilution due to the
spin phase transition also provides the appearance of triplet
features of the EPR signal.17b Parameters of the triplet signal
were estimated from the spectrum of polycrystalline sample of
1 at 20 K. The signal consists of two pairs of lines with
approximate peak separation of 5.2 and 2.6 mT. Constant
D of the dipole interaction was estimated from the peak
separation to be D = 2.6 mT (Fig. 4c). Averaged separation
between two spins in the point-dipole approximation was
calculated to be 10.2 A which is a reasonable value for the
fullerene dimer. The g-factor of the signal is slightly shifted
relative to the high-temperature major signal with gM and is
equal to gT = 2.0008.
Magnetic susceptibility of polycrystalline 1 was measured in
the 300–1.9 K range. Magnetic moment of the complex is 2.69
mB at 290 K. This value is close to the magnetic moment
calculated for a system with a triplet S = 1 state (2.83 mB) or
two noninteracting S = 1/2 spins (2.45 mB). The maximum of
magnetic susceptibility is found near 55 K and magnetic
susceptibility drops below 40 K (Fig. 6a). Observed temperature
dependence of magnetic susceptibility can be fitted well by the
Heisenberg model for isolated pairs of antiferromagnetically
interacting spins16 with J/kB = À44.7 K (Fig. 6b).
Thus, dimer has about two spins at room temperature.
Dimers have diamagnetic singlet (S = 0) ground state and
antiferromagnetic ordering of spins is realized below 40 K as is
shown by both EPR and SQUID measurements. Small
amount of spins is still observed even at 4 K (Fig. 5b). It is
interesting that triplet features of the signal from the dimers
are not observed in undiluted sample from room temperature
down to 40 K. Below 40 K dimers transfer to diamagnetic
state and paramagnetic dimers become magnetically isolated by
The most actively studied negatively charged fullerene dimer
is C120O2À which has spin state S = 1.18 The spectrum of this
dimer was measured in dilute solution. It is very similar to that
2À
of the doubly bonded C120 dimer at 20 K. It manifests a
central doublet-like line with g = 2.0018 which is surrounded
by triplet features centered at g = 2.0007 and having the
dipole interaction constant D = 2.6 mT.18 Thus, the distances
2À
between the spins in the C120 are comparable to that in the
2À
C
O
dimers.
120
In addition to signals attributed to the dimers, a weak
doublet-like signal appears at T r 40 K. This minor signal
is labelled as gI in Fig. 4b and 5b. It is narrow (DH = 0.24 mT
at 40, 20 and 4 K) and has gI = 1.9984. The comparison
of integral intensities of the minor and major signals at
40 K (when the major signal from the dimers has maximum
intensity) showed that the intensity of the minor signal is only
about 4% of the major signal. However, at 20 K the minor
signal can be well resolved as it grows by a factor of 2
in intensity in accordance with paramagnetic temperature
dependence, whereas the major signal decreases in intensity
by a factor of 4 (Fig. 4c and 5a).
Contribution from the dimers strongly decreases at low
temperatures (T o 20 K) and the paramagnetic tail is well
pronounced in SQUID measurements (Fig. 6b, black circles).
It can be fitted well by the Curie–Weiss expression with the
Curie constant C = 0.039 emu K molÀ1 and the Weiss
temperature of À1.5 K. The amount of Curie impurities was
estimated to be about 4% of the total amount of fullerenes.
Small Weiss temperature indicates weak magnetic interaction
between these spins in contrast to strong antiferromagnetic
exchange interaction observed for the spins localized on the
Fig. 5 EPR spectrum of arbitrary oriented single crystal of 1 at (a) 20 K;
(b) 4 K. For attribution of the signals with gM, gI, gT see the text.
2À
C120 dimers. The paramagnetic tail can be associated with
c
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Fig. 6 (a) Temperature dependence of molar magnetic susceptibility of 1 in the 1.9–100 K range. Inset shows the temperature dependence of wMT
(b) Theoretical fitting of the experimental curve by two contributions: the major contribution from the dimers (crosses) fitted by the Heisenberg
model for the pairs of antiferromagnetically interacting spins with J/kB = À44.7 K (squares) and the paramagnetic tail (black circles) fitted by the
Curie–Weiss expression with C = 0.039 emu K molÀ1 and Y = À1.5 K.
minor EPR signal manifested at T r 40 K which also has
paramagnetic temperature dependence down to 4 K.
(determined from relative integral intensities of the signals).
Dissociation of the dimers is irreversible because the narrow
signal does not reappear when thÀe crystal is cooled down to
Spins contributed to the minor EPR signal and para-
magnetic tail most probably originated from low concentration
impurities. Due to specific g-factoÀr value, these impurities were
ꢀ
RT and only the signal from C60 can be seen. Probably the
dissociation temperature of the dimers in 1 is too high and the
solvent molecules are removed from the crystal resulting in
loss of crystallinity of the sample. Indeed, according to
X-ray diffraction measurements the single crystal slowly loses
crystallinity at 400 K.
ꢀ
attributed to non-dimerized C60 radical anions which show
EPR signaÀls with g-factors in the 2.000–1.996 range. Signals
from C60 can also be narrow below 20 K.3,13 Generally
ꢀ
anions of fullerene derivatives including dianions of fullerene
dimers show signals with g-factor higher than 2.000.15,18 It was
Thus, the doubly bonded C1202À dimers are essentially more
thermodynamically stable than the singly bonded ones which
start dissociating at 140–250 K.10 Stability of the doubly
shown10 that weak EPR signals from monomeric C60 À (from
ꢀ
0.5 to 5% of a total amount of fullerenes) remain after
À
2À
ꢀ
dimerization of C60 in ionic complexes.
bonded C120 dimers Àis close to those of the singly bonded
2À
Crystal of 1 indicates high thermal stability of the doubly
2À
C140
and (C60CN2
)
dimers which dissociate above
2
bonded C120 dimers upon heating. Intensity of the narrow
360 K19 and 380 K,20 respectively. Dissociation temperature
of the neutral doubly bonded C120 dimers is even higher
(423–448 K)9 indicating destabilization of the negatively
charged dimers relative to the neutral ones due to the repulsion
of electrons.
EPR signal decreases above 380 K and a new broad signal
appears (Fig. 7). According to g-factor and linewidth, new
signal can be attributed to monomeric C60 À (g = 2.0000 and
ꢀ
DH = 3.8 mT at 446 K, Fig. 7) which forms after dissociation
2À
2À
of the C120
dimers. The degree of conversion of the
In spite of lower stability mainly singly bonded C120
dimers to monomers was estimated to be 97.5% at 446 K
dimers are formed in ionic complexes,10 whereas the doubly
bonded C1202À dimers were found only in two ionic complexes
with porphyrins. In one case both single and doubly bonded
2À
C120
dimers were found in the ionic complex with
manganese(II) tetraphenylporphyrin.21 One possible reason
2À
for formation of the doubly bonded C120 dimers in these
complexes is formation of porphyrin cages which accommodate
fullerene dimers. These cages are held together by van der
Waals forces and can perform as a pressure cell for the dimers.
This assists in formation of more compact doubly bonded
dimers instead of singly bonded ones. Stability of the doubly
bonded dimers is associated not only with their intrinsic
stability but with presence of a porphyrin cage which can
prevent dissociation of the dimer. After the crystal loses
crystallinity and the porphyrin cage is decomposed when
sample is heated above 400 K, the dimers cannot form again
at cooling.
Fig. 7 (a) The EPR signal from a single crystal of 1 at 446 K. (b) The
fitting of the signal by two Lorentzian lines is shown below, the
attribution of the signals is in the text).
c
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solution changed from violet to violet-brown. The solution
Conclusion
was cooled down to RT, filtered off, and NIR spectrum of the
solution was measured to show reduction of fullerene to
À1 charged state. One molar equivalent of ZnTMPP was
dissolved in obtained solution, which was then filtered in a
50 mL glass tube having diameter of 1.8 cm with a ground
glass plug, and 30 mL of hexane was layered over the solution.
The crystals grew on the walls of the tube after 1 month of
diffusion. The solvent was decanted from the crystals, which
were washed with hexane (the 70% yield). Study of the crystals
under microscope in a glove box showed two different phases.
The first major phase contained hexagonal prisms. The second
minor phase (from 5 to 40% of the total amount of crystals)
was good quality well-shaped elongated parallelepipeds. The
parallelepiped-shaped crystals were separated from hexagonal
prisms under microscope. The crystals were tested in X-ray
diffraction experiment. The composition of the parallelepiped-
shaped crystals was determined from X-ray diffraction on a
single crystal to be {(MDABCO+)ÁZnIITMPP}2Á(C1202À)Á
(C6H4Cl2)2.15(C6H5CN)1.85 (1). Several single crystals of these
shape had similar unit cell parameters. The structure and
composition of the major phase containing hexagonal prisms
could not be determined correctly due to the loss of crystal-
linity immediately after isolation.
2À
New complex 1 containing doubly bonded C120 dimers was
obtained. The dimer has D2h symmetry, the intercage C–C
bond of 1.607(6) A length and center-to-center distance
between fullerenes of 9.046 A. The IR-spectrum of the dimers
shows additional absorption bands due to breaking of C60
symmetry at dimerization and some bands are shifted relative
to those of the neutral C120 dimer due to formation of fullerene
anions. The bands at 950 and 1070 nm in the visible-NIR
spectrum of 1 are also characteristic of fullerene monoanions.
Magnetic moment of 1 is 2.69 mB at 290 K indicating the
presence of about two spins per dimer. Magnetic behaviour of
the dimers is described well by the Heisenberg model for
isolated pairs of antiferromagnetically interacting spins with
J/kB = À44.7 K. The dimers show a narrow doublet-like
signal with gM = 2.0014 at 290 K. Intensity of this signal
decreases abruptly below 40 K resulting in diamagnetic dilution of
the sample and the appearance of triplet features. Dipole
interaction constant D was estimated to be 2.6 and the
averaged spin separation was 10.2 A. The new minor signal
with gI = 1.9984 that appearsꢀbelow 40 K was attributed to
impurity of non-dimerized C60 À. The doubly bonded dimers
have high thermal stability and begin to dissociate only above
2À
380 K, whereas the singly bonded C120 dimers begin to
dissociate at 140–250 K. Presence of unpaired spins in a dimer
in a wide range of temperature between 40 and 380 K can
provide superior magnetic and conductive properties of the
compounds containing such dimers.
General procedures
EPR spectra were recorded for X-ray tested single crystals
from 4 up to 446 K and for a polycrystalline sample from 4 up
to 300 K with a JEOL JES-TE 200 X-band ESR spectrometer
equipped with a JEOL ES-CT470 cryostat. A Quantum
Design MPMS-XL SQUID magnetometer was used to measure
static susceptibility of polycrystalline 1 between 300 and 1.9 K
at 100 mT static magnetic field. A sample holder contribution
and core temperature independent diamagnetic susceptibility
(w0) were subtracted from the experimental data.
Experimental
Materials
H2TMPP and sodium ethanethiolate (CH3CH2SNa) were
purchased from Aldrich. C60 of 99.98% purity was received
from MTR Ltd. Solvents were purified in argon atmosphere.
o-Dichlorobenzene (C6H4Cl2) was distilled over CaH2 under
reduced pressure, benzonitrile (C6H5CN) was distilled over
Na under reduced pressure, and hexane was distilled over
Na/benzophenone. The solvents were degassed and stored in a
glove box. All procedures for the synthesis of 1 were carried
out in a MBraun 150B-G glove box with controlled atmosphere
with H2O and O2 content less than 1 ppm.
Crystal structure determination
Crystal data for 1 at 120(2) K: C255.85H119.85Cl4.3N13.85O8Zn2,
M = 3798.82, black parallelepiped, F(000) = 3898 e,
monoclinic, P21/n,
24.2553(11), c = 25.6268(13) A, b = 100.963(6)1, V =
8453.3(9) A3, Dc = 1.492 g cmÀ3, mMo = 0.430 mmÀ1
2ymax = 58.281, N(unique) = 17 592 (merged from 63 243
reflections, Rint = 0.0550, Rsig = 0.0624), N0 (I > 2s(I)) =
12 132, parameters refined 1739, restrains 1667, R = 0.0906,
wR2 = 0.1956, GOF = 1.062, |rmax = 0.584 e AÀ3|. CCDC
reference number is 735312.
Z = 4, a = 13.8523(12), b =
,
Synthesis
Synthesis of MDABCOÁI was described previously.22
ZnTMPP was obtained in a standard procedure used for
preparation of metalloporphyrins.23 One gram of H2TMPP
was boiled with 5-fold molar excess of ZnCl2 in N,N-dimethyl-
formamide (40 ml) under argon for 30 min. The mixture
was cooled down, and 100 ml of cold water was added to
precipitate ZnTMPP. The precipitate was filtered off, dried in
vacuum for 8 h and then was used without further purification.
The crystals of 1 were obtained by diffusion technique. C60
(25 mg, 0.035 mmol), 10-fold molar excess of CH3CH2SNa
(30 mg, 0.36 mmol) and 5-fold molar excess of MDABCOÁI
(46 mg, 0.18 mmol) were stirred in 16 ml of C6H4Cl2 : C6H5CN =
14 : 2 mixture at 60 1C for 2 h. While stirring, the colour of the
The intensity data for 1 were collected on an Oxford
diffraction ‘‘Gemini-R’’ CCD diffractometer with graphite
monochromated Mo-Ka radiation at low temperatures using
an Oxford Instrument Cryojet system. Raw data reduction to
F2 was carried out using CrysAlisPro, Oxford Diffraction Ltd.
The structures were solved by direct method and refined by the
full-matrix least-squares method against F2 using SHELX-97.24
Non-hydrogen atoms were refined in the anisotropic
approximation. Positions of hydrogen atoms were calculated
geometrically. Subsequently, positions of H atoms were
refined by the ‘‘riding’’ model with Uiso = 1.2Ueq of the
c
1834 New J. Chem., 2011, 35, 1829–1835
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2011

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connected non-hydrogen atom or as ideal CH3 groups with
Uiso = 1.5Ueq.
10 (a) A. Honnerscheid, L. Wullen, M. Jansen, J. Rahmer and
¨
¨
M. Mehring, J. Chem. Phys., 2001, 115, 7161; (b) D. V. Konarev,
S. S. Khasanov, A. Otsuka and G. Saito, J. Am. Chem. Soc., 2002,
124, 8520; (c) D. V. Konarev, S. S. Khasanov, G. Saito, A. Otsuka,
Y. Yoshida and R. N. Lyubovskaya, J. Am. Chem. Soc., 2003,
125, 10074; (d) D. V. Konarev, S. S. Khasanov, A. Y. Kovalevsky,
G. Saito, A. Otsuka and R. N. Lyubovskaya, Dalton Trans., 2006,
3716; (e) D. V. Konarev, S. S. Khasanov, G. Saito, A. Otsuka and
R. N. Lyubovskaya, J. Mater. Chem., 2007, 17, 4171;
(f) D. V. Konarev, A. Yu. Kovalevsky, A. Otsuka, G. Saito and
R. N. Lyubovskaya, Inorg. Chem., 2005, 44, 9547–9553; (g) M. Schulz-
Dobrick and M. Jansen, Angew. Chem., Int. Ed., 2008, 47, 2256;
(h) D. V. Konarev, S. S. Khasanov, G. R. Mukhamadieva,
L. V. Zorina, A. Otsuka, H. Yamochi and R. N. Lyubovskaya, Inorg.
Chem., 2010, 49, 3881; (i) D. V. Konarev, S. S. Khasanov and
R. N. Lyubovskaya, Russ. Chem. Bull., 2007, 56, 371.
To keep fullerene geometry close to ideal the bond length
restrains were applied in the disordered groups along with the
next-neighbour distances, using the SADI SHELXL instruction.
To keep the anisotropic thermal parameters of the fullerene atoms
within reasonable limits the displacement components were
restrained using ISOR and DELU SHELXL instructions. That
results in a great number of restrains used for the refinement of the
crystal structures of 1.
Molecular disordering in 1
Porphyrin molecules and fullerene dimers are ordered. The
MDABCO+ cations are disordered between two orientations
with the 0.827(6)/0.173(6) occupancies related by cation
rotation about the axis passing through two nitrogen atoms
of MDABCO+ by 601. Solvent molecules occupy two positions.
One position is occupied by the disordered C6H4Cl2 molecules
and the other one is shared by both disordered C6H4Cl2 and
C6H5CN molecules.
11 D. V. Konarev, S. S. Khasanov, A. Otsuka, G. Saito and
R. N. Lyubovskaya, J. Am. Chem. Soc., 2006, 128, 9292.
12 T. Picher, R. Winkler and H. Kuzmany, Phys. Rev. B: Condens.
Matter, 1994, 49, 15879.
13 C. A. Reed and R. D. Bolskar, Chem. Rev., 2000, 100, 1075.
14 M. Fujitsuka, C. Luo, O. Ito, Y. Murata and K. Komatsu, J. Phys.
Chem., 1999, 103, 7155.
15 (a) P. Boulas, F. D’Souza, C. Henderson, P. A. Cahill, M. T. Jones
and K. M. Kadish, J. Phys. Chem., 1993, 97, 13435; (b) V. Brezova,
´
A. Staska, P. Rapta, D. M. Guldi, K. D. Asmus and K. P. Dinse,
Magn. Reson. Chem., 1997, 35, 795; (c) S. Fukuzumi, H. Mori,
T. Suenobu, H. Imahori, X. Gao and K. M. Kadish, J. Phys.
Chem. A, 2000, 104, 10688.
Acknowledgements
16 J. S. Smart, Magnetism III, ed. G. T. Rado and H. Suhl, Academic
Press, London, N.Y., 1963, p. 63.
The work was supported by RFBR grant 09-02-01514, MEXT
Japan (152005019, 21st Century COE, 15073215 and
20110006) and JSPS (18GS0208 and Japan-Russia Bilateral
Joint Research Program).
17 (a) H. Bock, K. Gharagozloo-Hubmann, M. Sievert, T. Prisner
and Z. Havlas, Nature, 2000, 404, 267; (b) S. L. Veber,
M. V. Fedin, K. Yu. Maryunina, G. V. Romanenko,
R. Z. Sagdeev, E. G. Bagryanskaya and V. I. Ovcharenko, Inorg.
Chim. Acta, 2008, 361, 4148.
References
18 (a) A. L. Balch, D. A. Costa, W. Fawcett and K. Winkler, J. Phys.
Chem., 1996, 100, 4823; (b) P. P. Paul, K.-C. Kim, D. Sun,
P. D. W. Boyd and C. A. Reed, J. Am. Chem. Soc., 2002, 124, 4394.
19 (a) D. V. Konarev, S. S. Khasanov, I. I. Vorontsov, G. Saito, Yu.
A. Antipin, A. Otsuka and R. N. Lyubovskaya, Chem. Commun.,
2002, 2548; (b) D. V. Konarev, S. S. Khasanov, S. V. Simonov,
E. I. Yudanova and R. N. Lyubovskaya, CrystEngComm, 2010,
12, 3542.
1 M. J. Rosseinsky, J. Mater. Chem., 1995, 5, 1497.
2 B. Gotschy, Fullerene Sci. Technol., 1996, 4, 677.
3 D. V. Konarev and R. N. Lyubovskaya, Russ. Chem. Rev., 1999,
68, 19.
4 G. Bendele, P. Stephens, K. Prassides, K. Vavekis, K. Kortados
and K. Tanigaki, Phys. Rev. Lett., 1998, 80, 736.
5 H. Brumm, E. Peters and M. Jansen, Angew. Chem., Int. Ed., 2001,
40, 2069–2071.
20 Y. Yoshida, A. Otsuka, O. O. Drozdova, K. Yakushi and G. Saito,
J. Mater. Chem., 2003, 13, 252.
6 G. Oszla
Lett., 1997, 78, 4438.
7 P. W. Stephens, G. Bortel, G. Faigel, M. Tegze, A. Ja
S. Pekker, G. Oszlanyi and L. Forro, Nature, 1994, 370, 636–639.
nyi, G. Baumgarther, G. Faigel and L. Forro, Phys. Rev.
´ ´
21 D. V. Konarev, S. S. Khasanov, G. Saito, A. Otsuka and
R. N. Lyubovskaya, Inorg. Chem., 2007, 46, 7601.
´
nossy,
22 D. V. Konarev, S. S. Khasanov, A. Otsuka, G. Saito and
R. N. Lyubovskaya, Chem.–Eur. J., 2006, 12, 5225.
23 D. F. Marsh and L. M. Mink, J. Chem. Educ., 1996, 73, 1188.
´
8 V. D. Blank, S. G. Buga, G. A. Dubitsky, N. S. Serebryanaya, M.
Yu. Popov and B. Sundqvist, Carbon, 1998, 36, 319.
9 G. W. Wang, K. Komatsu, Y. Murata and M. Shiro, Nature, 1997,
387, 583.
24 G. M. Sheldrick, SHELX97, University of Gottingen, Germany,
1997.
¨
c
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