Molecular and ionic complexes of pyrrolidinofullerene bearing chelating 3-pyridyl units

Article abstract of DOI:10.1039/c1dt11040c

Molecular and ionic complexes of cis-2′,5′-di(pyridin-3-yl) pyrrolidino[3′,4′:1,9](C₆₀-I_h)[5,6]fullerene DP3FP with chlorobenzene (C₆H₅Cl), manganese(ii) tetraphenylporphyrin (Mn^IITPP) and tetrakis(dimethylamino)ethylene (TDAE) have been obtained for the first time. X-ray single crystal structure determination for the crystalline DP3FP·C₆H₅Cl (1) solvate proved unambiguously its molecular structure with the cis-arrangement of chelating 3-pyridyl groups. It has been demonstrated that DP3FP easily forms self-assembled photoactive complexes with metallated porphyrins. For example, the formation of a 1:1 complex between DP3FP and zinc (ii) tetraphenylporphyrin (Zn^IITPP) in cyclohexane solution (2) was evidenced using absorption spectroscopy. A successful X-ray single crystal structure determination was performed for a self-assembled triad composed of a DP3FP molecule linked with two Mn^IITPP molecules in {DP3FP·(Mn^IITPP) ₂}·(C₆H₄Cl₂)₃ (3). A strong organic donor TDAE reduces DP3FP to the radical anion state thus forming an ionic complex (TDAE⁺)·(DP3FP^-) ·(C₆H₄Cl₂)_1.6 (4). Optical, electronic and magnetic properties of 4 were investigated in detail. The performed studies strongly suggest that pyrrolidinofullerene DP3FP can be used as a building block in the design of various organic materials with advanced optoelectronic and/or magnetic properties.

Full text of DOI:10.1039/c1dt11040c

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PAPER
Molecular and ionic complexes of pyrrolidinofullerene bearing chelating
3
-pyridyl units†
a
b
a
a
a
Dmitri V. Konarev,* Salavat S. Khasanov, Alexey B. Kornev, Maxim A. Faraonov, Pavel A. Troshin* and
a
Rimma N. Lyubovskaya
Received 14th September 2011, Accepted 23rd September 2011
DOI: 10.1039/c1dt11040c
Molecular and ionic complexes of cis-2¢,5¢-di(pyridin-3-yl)pyrrolidino[3¢,4¢:1,9](C60-I
h
)[5,6]fullerene
II
DP3FP with chlorobenzene (C
6
H
5
Cl), manganese(II) tetraphenylporphyrin (Mn TPP) and
tetrakis(dimethylamino)ethylene (TDAE) have been obtained for the first time. X-ray single crystal
Cl (1) solvate proved unambiguously its
structure determination for the crystalline DP3FP·C
6
H
5
molecular structure with the cis-arrangement of chelating 3-pyridyl groups. It has been demonstrated
that DP3FP easily forms self-assembled photoactive complexes with metallated porphyrins. For
example, the formation of a 1 : 1 complex between DP3FP and zinc (II) tetraphenylporphyrin (Zn TPP)
II
in cyclohexane solution (2) was evidenced using absorption spectroscopy. A successful X-ray single
crystal structure determination was performed for a self-assembled triad composed of a DP3FP
II
II
molecule linked with two Mn TPP molecules in {DP3FP·(Mn TPP)
2
}·(C
6
H
4
Cl
2
3
) (3). A strong organic
donor TDAE reduces DP3FP to the radical anion state thus forming an ionic complex
∑
+
∑-
(
TDAE )·(DP3FP )·(C
6
H
4
Cl )1.6 (4). Optical, electronic and magnetic properties of 4 were investigated
2
in detail. The performed studies strongly suggest that pyrrolidinofullerene DP3FP can be used as a
building block in the design of various organic materials with advanced optoelectronic and/or
magnetic properties.
Introduction
cells based on metal oxide or gold electrodes covered with mono-
layers of fullerene/porphyrin dyads or triads. High light–power
5
Fullerenes and their derivatives are three-dimensional electron ac-
ceptor materials widely used in research and technology. Fullerene
derivatives are promising building blocks in the design of donor–
acceptor dyads where fullerenes perform as electron acceptor units,
while metalloporphyrins, phthalocyanines and other molecules
perform as donor components. The strongest advantage of
fullerene-based acceptors is their small reorganization energy
which provides the formation of long-lived charge separated
states.
conversion efficiency was achieved using fullerene/porphyrin
nanoclusters. Particularly exciting are self-assembled nanotubes
and nanorodes composed of fullerene derivatives and porphyrins.
These systems produce solar cells with promising efficiency of
6
0
.63% that might be significantly increased after subsequent
1–4
7
optimization. Planar p–n heterojunction devices were dramat-
ically improved when pyrrolidinofullerenes bearing chelating
pyridyl groups (PyFs) were used as electron acceptor materials
8
in combination with zinc phthalocyanine as electron donor.
Self-assembled fullerene/porphyrin and fullerene/phthalo-
cyanine systems are of particular interest since they mimic natural
The observed increase in device efficiency was attributed to
complex formation at the interface between the p- and n-type
2,3
photosynthetic antenna. Fullerene/porphyrin architectures are
widely applied for construction of different types of photovoltaic
devices. The most intensely studied are photoelectrochemical solar
9
materials. Photoactive fullerene–phthalocyanine systems were
also successfully applied in the design of bulk heterojunction and
10,11
mixed heterojunction solar cells.
The above examples illustrate the importance of pyridyl-
appended fullerene derivatives for design of photoactive systems
for solar energy conversion. Many self-assembled dyads composed
of pyrrolidinofullerenes and metallated porphyrins (phthalo-
cyanines) were investigated in solution. They were based on
a
Institute of Problems of Chemical Physics of RAS, Chernogolovka, Moscow
region, 142432, Russia. E-mail: konarev@icp.ac.ru, troshin2003@inbox.ru
b
Institute of Solid State Physics RAS, Chernogolovka, Moscow region,
1
42432, Russia. E-mail: khasanov@issp.ac.ru
Electronic supplementary information (ESI) available: Electronic sup-
†
plementary information (ESI) available: IR spectra of starting compounds
pyrrolidinofullerenes bearing one chelating pyridyl or imidazolyl
and complexes 1, 2 and 4. Crystallographic data in CIF format for complex
1
12–14
group,
or two chelating substituents at 2¢ and 5¢ positions of
at 100 and 295R and complex 3 at 120 K. CCDC reference numbers
22362, 822364 and 822366. For ESI and crystallographic data in CIF or
15–17
the pyrrolidine ring,
positions 1¢,2¢,5¢.
or even three chelating pyridyl units at
8
18,19
On the contrary, there are just few examples
other electronic format see DOI: 10.1039/c1dt11040c
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of porphyrine–fullerene dyads characterized in solid state by X-
ray single crystal diffraction. All such systems are non-covalently
linked dyads composed of one pyrrolidinofullerene molecule and
one Zn TPP molecule.
In this work we report the preparation and X-ray single crystal
bases or acids) and continuous heating of the reagents at reflux in
1,2-dichlorobenzene (10–12 h).
Here we proposed the conduction of such reactions under
microwave heating conditions. Indeed, irradiating a mixture of
the [60]fullerene, 3-pyridinecarboxaldehyde, 3-picolylamine and
butyric acid dissolved in 1,2-dichlorobenzene in a conventional
microwave oven (600 W) produced the title product 1 in 15 min
with 70% yield (Scheme 1). Similar results were achieved under
conventional heating conditions only after 6–10 h. Therefore, there
is an obvious accelerating effect of microwave irradiation on the
formation of the title pyrrolidinofullerene. Thus, compound 1
II
20–22
structures of parent pyrrolidinofullerene DP3FP (1) and the
II
first triad composed of DP3FP and two Mn TPP molecules (3)
(
Fig. 1). In addition, synthesis and spectroscopic characterization
II
of 1 : 1 complexes of DP3FP with Zn TPP (2) and TDAE (4) are
discussed.
(DP3FP) can easily and quickly be prepared under microwave
conditions to be available on a multigram scale for various
applications.
Scheme 1
1.2 Molecular structure of DP3FP
The crystals of starting DP3FP were obtained as 1 : 1 solvate
with chlorobenzene DP3FP·C
6
H Cl (1) by slow concentration
5
of the chlorobenzene solution of pyrrolidinofullerene in argon
atmosphere. The crystal structure of 1 was studied at room
temperature and 100 K. At both temperatures DP3FP is ordered,
whereas solvent C
6
5
H Cl molecules are disordered between three
orientations. The top and side views of the DP3FP molecule
are shown in Fig. 2. It is clearly seen that two 3-pyridyl groups
are arranged in cis-configuration with respect to the pyrrolidine
ring. This result unambiguously justifies indirect assignment of
stereochemistry of pyrrolidinofullerene DP3FP made previously
23,24
from the analysis of the NMR data.
Pyridine nitrogens in
DP3FP are arranged in the opposite directions.
Fig. 1 Molecular structures of the investigated compounds.
Results and discussion
Fig. 2 Top (a) and side (b) views of the DP3FP molecule in solvate 1.
Carbon atoms of the pyrrolidine addend are marked with orange color for
clarity.
1
.1 Microwave-assisted synthesis of DP3FP
Efficient methods for the preparation of pyrrolidinofullerenes with
23,24
the appended chelating pyridyl groups were reported.
The
The pyrrolidine ring is attached to the 6–6 bond of the
˚
synthesis of fullerene derivatives bearing 2-pyridyl or 4-pyridyl
groups was straightforward and produced desired products in
high yields within short reaction times (2–5 min to 1–2 h). On
the contrary, the preparation of fullerene derivatives bearing 3-
pyridyl groups required the application of some catalysts (organic
fullerene cage which elongates from 1.380(4) A in C60 to 1.585(4)
˚
A in DP3FP. The attachment of the pyrrolidine ring distorts
significantly the fullerene cage. Thus, the length of the cage along
the axis passing through the functionalized 6–6 bond is 0.3 A
greater than the dimensions of the carbon cage in the two other
˚
7
92 | Dalton Trans., 2012, 41, 791–798
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Table 1 Association constants for complexes of different pyrrolidinofullerenes with metallated porphyrins
1
2
3
3
-1
Compound
R
R
R
Porphyrin
Solvent
K
a
¥ 10 L mol
Ref.
P2FP
P3FP
P4FP
ImPhFP
2-Py
3-Py
4-Py
ImPh
H
4-Py
4-Py
2-Py
3-Py
4-Py
H
H
H
H
4-Py
Me
Me
H
H
H
H
H
H
H
H
H
H
2-Py
3-Py
4-Py
ZnTPP
ZnTPP
ZnTPP
ZnTPP
ZnTPP
InClTPP
ZnTPP
ZnTPP
ZnTPP
ZnTPP
1,2-dichlorobenzene
1,2-dichlorobenzene
1,2-dichlorobenzene
1,2-dichlorobenzene
1,2-dichlorobenzene
chloroform
1,2-dichlorobenzene
cyclohexane
cyclohexane
no binding
7.74
7.66
11.6
74
69
7.2
12.0
84
14.5
14
14
14
14
21
13
14
18
2
P4FP
MP4FP
MP4FP
DP2FP
DP3FP
DP4FP
This work
15
1,2-dichlorobenzene
1
2
3
Definitions: R , R and R are substituents in the pyrrolidine ring according to Fig. 3; K
a
, association constant; ImPh, 4-(1H-imidazol-1-yl)phenyl.
orthogonal directions. This is a reasonable consequence of the
3
appearance of two sp -hybridized carbon atoms in the fullerene
cage.
II
1
.3 Complex formation between DP3FP and Zn TPP in solution
Pyridyl substituted pyrrolidinofullerenes (Fig. 3) are strong
enough ligands. They readily form self-assembled complexes with
ZnTPP via axial coordination of pyridyl nitrogen to the metal
atom in the macrocyclic ring. Binding constants published for
various pyrrolidinofullerens bearing chelating groups and ZnTPP
are listed in Table 1. It is seen that the complexes of 2P4FP
with ZnTPP and MP3FP with indium(III) tetraphenylporphyrin
13,21
chloride are characterized by the highest association constants.
-6
Fig. 4 Evolution of the absorption spectrum of ZnTPP (3.2 ¥ 10 mol
-1
L ) in cyclohexane upon the addition of 1–5 equivalents of DP3FP. The
upper inset shows the Scatchard graph where the changes in absorbance
(
DA) at 416 nm are plotted against DA/[1], where [1] is concentration of
DP3FP. The bottom inset illustrates the shift of the Q-bands of ZnTPP
upon the addition of 0, 2, 3 and 5 equivalents of DP3FP.
DP3FP ligand. The Q-bands of ZnTPP are shifted to 563, 604
and 624 nm, which is also a consequence of complex formation
(
Fig. 4, bottom inset). The isobestic point located at 423 nm
25
suggests the formation of a 1 : 1 complex. The 1 : 1 stoichiom-
etry of the complex was also determined from the Job’s plot
(ESI†).
Fig. 3 General formula of pyrrolidinofullerenes bearing pyridyl units
1
2
3
at different positions. The definitions of R , R and R for different
compounds are shown in Table 1.
The association constant K
a
was determined from the slope
of the Scatchard plot (Fig. 4, the upper inset). The obtained
4
-1
The association constant of the DP3FP–ZnTPP couple was de-
termined using absorption spectroscopy. The absorption spectrum
of ZnTPP in cyclohexane shows the intense Soret band at 416 nm
and weaker Q-bands with the maxima at 547, 585 and 622 nm
K
a
value of 8.4 ± 0.5 ¥ 10 L mol indicates that DP3FP is a
stronger ligand in cyclohexane than pyrrolidinofullerene DP2FP
(K = 1.2 ¥ 10 L mol ). This difference can be due to different
4
-1 18
a
modes of coordination of DP2FP and DP3FP ligands with
ZnTPP. In the case of pyrrolidinofullerene DP2FP, two 2-pyridyl
groups are sterically hindered and cannot be involved in complex
formation with ZnTPP. Therefore, a coordination bond is formed
between the pyrrolidine nitrogen and zinc atom of ZnTPP. X-ray
diffraction studies revealed that in this case the N ◊ ◊ ◊ Zn bond is
(
Fig. 4, curve 0). In a typical spectroscopic titration experiment
increasing amounts of DP3FP were added to the aliquot of ZnTPP
dissolved in cyclohexane. Concentration of DP3FP in solution was
-
6
-5
-1
varied from 4 ¥ 10 to 2 ¥ 10 mol L . This corresponds to the
changes in a DP3FP : ZnTPP ratio from 1 : 1 to 5 : 1. Evolution of
the absorption spectrum of ZnTPP upon the addition of DP3FP
is shown in Fig. 4
˚
considerably longer (2.29 A) than that in the dyads composed
of MP4FP or 2P4FP ligands (the N ◊ ◊ ◊ Zn bond length is 2.13–
˚
2.16 A), which provides chelating 4-pyridyl groups coordination
The longer N ◊ ◊ ◊ Zn coordination bond suggests
weaker association of DP2FP with ZnTPP. In the case of DP3FP
3-pyridyl units are not sterically hindered and can participate in
The increase in concentration of DP3FP results in the decrease
in intensity of the Soret band of starting ZnTPP (416 nm) and
the appearance of a new band at 430 nm which can be attributed
to the Soret band of ZnTPP linked with the axially coordinated
20–22
with ZnTPP.
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complex formation with metallated porphyrins. This might be a
II
reason why the association constant for DP3FP–Zn TPP system
II
is larger than for the previously studied DP2FP–Zn TPP dyad.
The direct comparison of DP3FP with other ligands is prob-
lematic because the association constants are known to be
strongly solvent dependent. For example, for a simple pyridine
II
molecule used as a ligand for coordination with Zn TPP, the
-
1
association constants of 610, 6900, 7750 and 25 100 L mol
were obtained in CHCl
3
, CH
2
Cl
2
, C
6
H
4
Cl
2
and cyclohexane
value obtained in
14,26
solvents, respectively.
Nevertheless, the K
a
our experiments for DP3FP suggests that it is quite a strong
ligand able to form complexes with a variety of metallated
macrocycles.
1
.4 Preparation and X-ray single crystal structure
characterization of the self-assembled triad composed of DP3FP
II
and two Mn TPP units
We prepared complexes of DP3FP with tetraphenylporphyrinates
of different metals such as cobalt(II), zinc(II) and manganese(II). In
II
II
the case of Co TPP and Zn TPP, dark polycrystalline precipitates
were formed in quantitative yields within several days. The
obtained crystals were found to be very small and not suitable
for the X-ray diffraction analysis. On the contrary, in the case of
II
Mn TPP, the product does not precipitate so readily. Diffusion of
II
hexane into the solution containing both DP3FP and Mn TPP
in 1,2-dichlorobenzene during one month produced large black
prisms with characteristic blue luster. These crystals rapidly
degraded after isolation from mother solution. Therefore, a crystal
taken from the solution was immediately cooled down to 100 K
in nitrogen flow at the diffractometer and then successful mea-
surements and the structure determination were preformed.
Structure of complex 3 was solved with relatively high R-
Fig. 5 Top (a) and side (b) views of the molecular structure of
coordination triad 3. The carbon atoms of the pyrrolidine ring are shown
with orange color for clarity.
◦
coordinated to the DP3FP unit form an angle of 61.4 (Fig. 5).
factor (12.14%). The reason for this is the presence of large
This angle is defined by geometry of two 3-pyridyl substituents in
the DP3FP molecule.
The projection of the crystal packing of 3 along the lattice c axis
is shown in Fig. 6. The molecular arrangement is characterized
by a zigzag of pyrrolidinofullerene chains and large continuous
channels filled with disordered solvent molecules both parallel to
3
˚
voids in this complex (calc. volume of 958 A ) which are
occupied by strongly disordered solvent molecules (those are
C
6
H
4
2
Cl molecules). Moreover solvent molecules can partially
leave these cavities during transportation of a crystal from solution
to diffractometer. That makes impossible qualitative analysis
of disordered components in these voids. Thus the presented
II
composition {DP3FP·(Mn TPP)
2
}·(C
6
H
4
Cl
2
) takes in account
3
only solvent molecules whose position was resolved correctly
from X-ray diffraction data. In spite of a relatively high R-factor
II
the geometry of DP3FP·(Mn TPP)
2
triads was solved with good
precision since they are well ordered in the complex.
II
Geometry of DP3FP·(Mn TPP)
2
triad is shown in Fig. 5. It
is notable that pyridine nitrogens in DP3FP are arranged in the
same direction in contrast to parent pyrrolidinofullerene whose
molecular structure is shown in Fig. 2. The lengths of axial
II
coordination Mn–N(DP3FP) bonds in triad for both Mn TPP
˚
is equal to 2.199(5) A. These bonds are slightly longer than the
Zn–N bonds in the dyads comprising chelating 4-pyridyl groups
II
coordinated to Zn TPP. The average lengths of the equatorial Mn–
Fig. 6 The projection of the crystal packing of triad 3 along the lattice
c axis which shows cross-sections of the zigzag fullerene chains and large
channels occupied by solvent molecules (a); the projection of the chain
of triad molecules along the lattice a axis (b). Green ellipses define the
channels occupied by disordered solvent molecules. Green dashed lines
show short VdW C ◊ ◊ ◊ C contacts between fullerenes. Solvent molecules
are not shown for clarity.
II
˚
N(TPP) bonds in Mn TPP is 2.110(5) A. Relatively large lengths
II
of these bonds strongly suggest the high spin state of Mn TPP in
. The porphyrin rings are distorted and have an umbrella shape
27
3
˚
with manganese atoms displaced by 0.415 A out of the porphyrin
plane (defined by four porphyrin ring nitrogen atoms) towards
pyridine nitrogens. The planes of the two porphyrin molecules
7
94 | Dalton Trans., 2012, 41, 791–798
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∑
+
-
)
0.5 and to 1667–1672 cm-1 in
36
the lattice c axis. The pyrrolidinofullerene molecules are separated
by porphyrin layers lying in the ac plane. Most probably, solvent
molecules are weakly bonded in the channels and can easily leave
the crystal. This results in rapid crystal degradation which was
observed when the crystals were stored without solvent. The
distances between the fullerene cages in the zigzag chains are not
(TDAE )·(C70 )·(C
6
H
4
Cl
2
)·(C
6
H
14
35
the dication state. The TDAE characteristic band was observed
at 1521 cm in the spectrum of 4 thus indicating the formation of
the TDAE cation.
The optical absorption spectrum of 4 in KBr pellet in the
visible and NIR ranges is shown in Fig. 7. New absorption
bands appear in the spectrum of 4 at 792 and 998 nm. These
bands can be attributed to the D3PFP radical anion. Similar
bands appear in the NIR spectrum of C60 at 930–950 and
-
1
∑
+
˚
equal. One centre-to-centre distance is shorter (10.098 A) than
∑
-
˚
another (10.132 A). There is a short Van der Waals (VdW) C ◊ ◊ ◊ C
∑
-
˚
contact with the length of 3.085 A formed between two fullerene
37–39
cages that are arranged in the close proximity to each other
1070–1090 nm.
Thus, the obtained spectroscopic data prove
(
Fig. 6b).
unambiguously that complex 4 has ionic ground state and can be
∑
+
∑-
Optical IR (see ESI†) and NIR spectra of 3 in KBr pellet
presented as (TDAE )·(DP3FP )·(C
6
H
4
Cl
2
1.6
) .
provided some information on the nature of electronic interactions
between the pyrolidinofullerene and the Mn TPP units in the
II
triad. First of all, very small shift of the characteristic IR
-
1
-1
band of starting DP3FP at 1427 cm to 1432 cm in triad
suggests that there is no noticeable charge transfer from
3
28
porphyrin to pyrrolidinofullerene. A solid state absorption
spectrum of triad 3 in the NIR range shows no bands that can
∑
-
be attributed to the DP3FP radical anion, which is further
evidence of the absence of charge transfer in this system.
II
The Soret and Q-bands of the Mn TPP units in triad 3 were
observed at 444, 571 and 616 nm, respectively. These positions
are almost equal to those in the spectrum of uncomplexed
II
Mn TPP in which the Soret band appears at 443 nm, while
Q-bands are manifested at 572 and 611 nm. A small shift
II
of these bands upon complex formation of Mn TPP with
DP3FP suggests weak electronic interactions between these
components. Much stronger shifts of the Mn TPP absorption
Fig. 7 The absorption spectrum of 4 in KBr pellet in the visible–NIR
range.
II
bands (up to 10 nm) were observed in the ionic fullerene
+
II
∑-
II
complexes {(Cation )
2
·Mn TPP}·(C60
)
2
when Mn TPP
The ESR spectrum of polycrystalline 4 manifested an intense
asymmetric signal at room temperature which can be well fitted by
coordinates nitrogen containing N-methyldiazabicyclooctane
MDABCO ) or N,N¢N¢-trimethylpiperazinium (TMP )
+
+
(
two narrow lines (g
1
= 2.0030, DH = 0.7 G and g
2
= 2.0035, DH = 0.5
29–31
∑+
cations.
G, Fig. 8). It is known that TDAE shows a narrow signal with g =
36
Thus, triad 3 is a molecular architecture which shows no notice-
able charge transfer from the porphyrin to the pyrrolidinofullerene
unit. Similarly, no charge transfer was observed previously for
2.0035 whereas anion radicals of pyrrolidinofullerenes manifest
40
narrow ESR signals with g = 2.0001–2.0002. Narrow ESR signals
with g-factors larger than 2.0000 are also characteristic of radical
anions of other fullerene derivatives.
II
41,42
supramolecular complexes of Mn TPP with fullerenes C60 and
32,33
70
C .
1
.5 The formation of ionic complex of D3PFP with
tetrakis(dimethylamino)ethylene TDAE·D3P-FP·(C
6
H
4
2
Cl )1.6 (4)
Tetrakis(dimethylamino)ethylene is stronger donor than
a
II
+/0
Mn TPP with the first oxidation potential E of -0.75 V vs.
34
SCE. To prepare the complex, parent DP3FP (30 mg) was
dissolved together with an excess of TDAE (0.5 mL) in 1,2-
dichlorobenzene. Slow diffusion of hexane into the prepared
solution results in the formation of dark crystals of complex
4
, which has the TDAE·DP3FP·(C
6
H
4
Cl )1.6 formula according
2
to the chemical analysis data. The FTIR spectrum of 4 showed
strongly shifted absorption bands of the DP3FP unit (ESI†). The
-
1
characteristic band of parent DP3FP at 1427 cm was shifted to
-
1
1
386 cm in the spectrum of 4. Moreover, this band becomes much
more intense in the spectrum of 4 as compared to the spectrum of
parent DP3FP.
Fig. 8 The experimental ESR spectrum of polycrystalline 4 at 260 K
(top). The fitting of the signal by two Lorentzian curves (bottom).
The TDAE molecule also has one characteristic band which
-
1
35
changes its position from 1340 cm in the neutral state to
Exact attribution of these signals is not possible. Spectrum can
518 cm- in the radical cation state in (TDAE )·(C60
1
∑+
∑- 35
)
or
belong to one common spin having axial symmetry with the g
1
^
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Fig. 9 Temperature dependence of g-factor (a) and linewidth (b) for the two components of the ESR spectrum of polycrystalline 4 in the 4–295 K range.
and gII components or to different spins (g
2
= 2.0035 is close to
broadening of the EPR signal and increasing g-factor were also
∑
+
∑+
∑-
the g-factor of EPR signal from TDAE whereas g
1
= 2.0030
observed for ferromagnetic (TDAE )·(C60 ) complex below 20 K.
∑
-
∑+
43
is shifted closer to DP3FP and can belong to both TDAE
These changes were associated with a ferromagnetic transition.
∑
-
and DP3FP species having exchange interaction. The remarkable
∑
+
∑-
ferromagnetic phase of (TDAE )·(C60 ) is also characterized only
Conclusions
42
by one broad EPR signal with g = 2.0003. This value lies between
∑
+
∑-
the characteristic positions of the TDAE and C60 ESR signals.
The appearance of only one broad signal can be a consequence of
We have presented for the first time the improved microwave-
assisted synthesis of pyrrolidinofullerene DP3FP (1) bearing two
chelating 3-pyridyl groups at 2¢ and 5¢ positions of the pyrrolidine
ring. The molecular structure of DP3FP was determined by the
X-ray single crystal structure analysis for its 1 : 1 solvate with
chlorobenzene. It was proved unambiguously that two 3-pyridyl
groups in the DP3FP molecule are arranged in cis-configuration
with respect to the pyrrolidine ring.
∑
+
strong exchange interactions between the paramagnetic TDAE
∑
-
and C60 units.
The temperature dependences of g-factors and linewidths of
the components of the ESR spectrum of 4 are shown in Fig. 9.
Both components can be observed in the spectrum down to 80 K
with nearly temperature independent parameters. Broadening of
these signals and their shifting towards larger g-factors is observed
below 60 K. We also analyzed the temperature dependence of
total integral intensity of the ESR signal in the the spectrum of 4
It was shown that DP3FP is a strong ligand capable of complex
formation with a variety of metallated macrocycles. In particular,
the formation of a 1 : 1 complex between DP3FP and ZnTPP was
evidenced in solution. The association constant of 8.4 ± 0.5 ¥
(
Fig. 10). It can be well fitted by the Curie–Weiss law with the
4
-1
negative Weiss temperature of -10 K in the whole temperature
range (4–295 K). SQUID measurments for the sample of 4 support
ESR data. Reciprocal magnetic susceptibility can be fitted well by
the Curie–Weiss expression with negative Weiss temperature of
10 L mol determined for this complex in cyclohexane exceeds
the binding constants reported previously for other complexes of
pyrrolidinofullerenes with porphyrins in cyclohexane, chloroform
and 1,2-dichlorobenzene.
-
9 K in the 10–300 K range. Therefore, the observed broadening
Self-assembled triad 3 composed of one DP3FP unit and two
II
of the ESR signals and increasing g-factors below 60 K might
be attributed to antiferromagnertic interactions of TDAE and
DP3FP spins in 4. It should be noted for comparison that
Mn TPP molecules was prepared and characterized by X-ray
∑
+
II
single crystal diffraction. It was revealed that both Mn TPP
∑
-
molecules form coordination bonds with the nitrogen atoms of
two 3-pyridyl groups of the DP3FP molecule. Optical spectra
showed weak electronic interactions between the porphyrin and
pyrrolidinofullerene units in triad 3 and the absence of charge
transfer in the ground state.
On the contrary, complex 4 formed by DP3FP with the strong
organic donor TDAE has ionic ground state and its composition
∑
+
∑-
can be represented by the formula (TDAE )·(DP3FP )·
(
C
6
H
4
Cl 1.6. The formation of the radical anion and cation was
2
)
proved by the optical absorption spectra in the visible, NIR
and IR ranges. The EPR spectrum of 4 was considered as a
superposition of two narrow signals (g
= 2.0035, DH = 0.5 G). Noticeable broadening of the signals and
their shift towards higher g-factors observed below 60 K strongly
1
= 2.0030, DH = 0.7 G and
g
2
∑
+
suggests antiferromagnertic interactions between the TDAE and
∑
-
DP3FP units. This conclusion is supported by the temperature
dependence of integral intensity of the EPR signal in the 4–295 K
range and by the temperature dependence of reciprocal magnetic
susceptibility in the 10–300 K range which were fitted by the
Fig. 10 Temperature dependence of integral intensity of both compo-
nents of the ESR spectrum of 4 fitted by the Curie–Weiss law with the
Weiss temperature of -10 K.
7
96 | Dalton Trans., 2012, 41, 791–798
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Curie–Weiss law with negative Weiss temperatures of -10 and
9 K, respectively.
of the fresh crystal of 3 was additionally tested by the Energy
Dispersive X-ray analysis (EDX) using a SUPRA-50UP electron
microscope to show a Cl to Mn ratio in a crystal to be close
-
to 6 : 1. Therefore the real composition of complex 3 should be
Experimental
II
close to {DP3FP·(Mn TPP)
2
}·(C
6
H
4
Cl ) . The difference between
2
6
the compositions determined from EDX and X-ray diffraction
analyses is three solvent C Cl molecules. Most probably these
Materials
6
H
4
2
III
II
II
Mn TPPCl, Co TPP, Zn TPP and tetrakis(dimethylamino)-
molecules occupy large voids in the structure of 3 where they are
strongly disordered. The crystals were decanted from the solution,
washed with hexane to yield black prisms with characteristic blue
luster (25% yield). The IR and visible–NIR spectra were measured
on fresh crystals. Testing the crystals by X-ray diffraction one day
later showed that they completely lost crystallinity (most probably
II
ethylene (TDAE) were purchased from Aldrich. Mn TPP was
synthesized by the reduction of Mn TPPCl with an excess
III
44
of NaBH
mosphere. Chlorobenzene (Aldrich) was used as received. 1,2-
Dichlorobenzene (Aldrich) was distilled over CaH under reduced
4
in ethanol. Solvents were purified in argon at-
2
II
pressure and hexane was distilled over Na/benzophenone under
argon. Solvents for preparation of 3 and 4 were degassed and
stored in a glove box. All manipulations for the synthesis of 3 and
due to the loss of solvent). Similarly, Co TPP and ZnTPP were
II
used in the synthesis instead of Mn TPP. However, in this case a
nearly quantitatively polycrystalline precipitate was formed after
several days.
4
were carried out in a MBraun 150B-G glove box with controlled
atmosphere. The crystals were stored in a glove box and put in
anaerobic conditions in 5 mm quartz tubes for EPR measurements
under argon. KBr pellets for IR and visible–NIR measurements
were prepared in a glovebox.
The TDAE·DP3FP·(C
6
H
4
Cl )1.6 (4) was prepared by dissolving
2
DP3FP (30 mg, 0.033 mmol) in 14 mL of 1,2-dichlorobenzene with
◦
an excess of TDAE (0.5 mL) upon stirring at 60 C for a night.
Brown solution was formed. The solution was cooled down to
room temperature, filtered in a 50 mL glass tube of 1.8 cm diameter
with a ground glass plug, and 30 mL of hexane was layered over
the solution. Diffusion was carried out during 1 month to yield the
crystals of 4 on the wall of the tube. The solvent was decanted from
the crystals, which were washed with hexane to give black plates up
Synthesis
Pyrrolidinofullerene DP3FP was synthesized as follows. Fullerene
C
60 (230 mg) was dissolved in 12 mL of 1,2-dichlorobenzene
together with 80 mg of 3-pyridinecarboxaldehyde and 80 mg of
-picolylamine. The reaction mixture was closed in a 100 mL
3
to 0.3 ¥ 0.3 ¥ 0.5 mm in size with 40% yield. The composition of 4
3
was determined by elemental analysis: TDAE·DP3FP·(C
6
H
4
Cl
2
)
1.6
teflon reactor and heated inside a conventional microwave oven
at 600 W for 15 min. (Caution: the conditions should be carefully
adjusted to prevent overheating of dichlorobenzene up to and
above the boiling temperature and explosive opening of the
reactor). After heating, the teflon container was cooled down
to room temperature. The reaction mixture was diluted by 3–4
volumes of toluene and separated by column chromatography on
silica using toluene/methanol mixtures as eluent. The product
yield was 70%. Column chromatography isolation of DP3FP and
spectroscopic characteristics of this compound were previously
(C91.6
H
39.4
N
7
Cl3.2, 1350.8); found, %: C = 80.85, H = 2.93, N = 7.48;
Cl = 8.33; calc., %: C = 81.43, H = 2.92, N = 7.25; Cl = 8.40.
General
FT-IR spectra were measured in KBr pellets with a Perkin-
-
1
Elmer Spectrum BX spectrometer (400–4000 cm ). The UV-
visible spectrum was measured in KBr pellet on a Shimadzu-3100
spectrometer in the 400–1600 nm range. Solution spectra in visible
range were measured on Specord M40. ESR spectra were recorded
with a Radiopan SE/X-2547 spectrometer at room temperature
and with a JEOL JES-TE 200 X-band ESR spectrometer equipped
with a JEOL ES-CT470 cryostat in the 295–4 K range. Magnetic
susceptibility measurements were carried out with a Quantum
Design MPMS-XL SQUID magnetometer at a magnetic field of
23
reported in detail.
For the preparation of the crystals of DP3FP·C
6
H Cl (1),
5
starting fulleropyrrolidine (30 mg, 0.033 mmol) was dissolved
in chlorobenzene (15 mL). Slow evaporation of the solution
under argon produces the crystals of 1 whose composition was
determined from X-ray analysis on single crystal. Unit cell
parameters for several crystals tested from one synthesis are the
same showing that crystals belong to one crystal phase. The prisms
1
000 G between 2 and 300 K.
X-ray crystal structure determination
of 1 were of brown–black color and were obtained with 60% yield.
Crystal data for 1 at 100(2) K.
mol , dark brown prism, monoclinic, P 2
C
78
H
16ClN
3
, M
r
= 1030.39 g
II
The crystals of {DP3FP·(Mn TPP)
2
}·(C
6
II
H
4
Cl
2
)
3
(3) were ob-
-1
1
/c, a = 10.0579(10), b =
tained in anaerobic conditions since Mn TPP is sensitive to
oxygen. DP3FP (30 mg, 0.033 mmol) and a slight excess of
◦
3
˚
˚
4
d
1.578(5), c = 9.9818(9) A, b = 102.202(9) , V = 4079.9(7) A , Z = 4,
-3
-1
◦
calc = 1.677 g cm , m = 0.161 mm , F(000) = 2088, 2qmax = 52.80 ,
II
Mn TPP (24 mg, 0.036 mmol) were dissolved in 14 mL of 1,2-
reflections measured 30736, unique reflections 8353, reflections
with I > 2s(I) = 5371, parameters refined 838, restraints 391,
◦
dichlorobenzene at 60 C for 6 h. The resulting dark green solution
was filtered into a 50 mL tube for diffusion and hexane was
layered over the obtained solution. After one month well-shaped
crystals were formed on the walls of the tube in the hexane part of
the solution. The crystal for X-ray diffraction measurements was
taken directly from the solution and immediately cooled down
to 100 K in the nitrogen flow. Therefore, the composition of 3
was determined from the X-ray diffraction data. The composition
R
1
= 0.0768, wR
2
= 0.1550, G.O.F. = 1.064, CCDC reference
number is 822365.
Crystal data for 1 at 293(2) K.
C
78
H
16ClN
3
, M = 1030.39 g
r
-
1
mol , dark brown prism, monoclinic, P 2
1
/c, a = 10.1250(12),
◦
˚
b = 42.021(5), c = 10.0152(10) A, b = 101.937(11) , V = 4169.0(8)
3
-3
-1
˚
A , Z = 4, dcalc = 1.642 g cm , m = 0.158 mm , F(000) = 2088,
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 791–798 | 797

View Article Online
◦
2
8
q
max = 52.74 , reflections measured 31698, unique reflections
13 T. N. Lomova, M. E. Malov, M. V. Klyuev and P. A. Troshin,
Macroheterocycles, 2009, 2, 164.
495, reflections with I > 2s(I) = 4550, parameters refined 838,
= 0.0711, wR = 0.2225, G.O.F. = 1.018, CCDC
reference number is 822362.
1
4 F. D’Souza, G. R. Deviprasad, M. E. Zandler, V. T. Hoang, A. Klykov,
M. Van Stipdonk, A. Perera, M. E. El-Khouly, M. Fujitsuka and O.
Ito, J. Phys. Chem. A, 2002, 106, 3243.
restraints 385, R
1
2
1
1
5 G. Yin, D. Xu and Z. Xu, Chem. Phys. Lett., 2002, 365, 232.
6 M. E. El-Khouly, S. Gadde, G. R. Deviprasad, M. Fujitsuka, O. Ito
and F. D’Souza, J. Porph. Phth., 2003, 7, 1.
Crystal data for 3 at 120(2) K.
694.10 g mol , black prism, monoclinic, C 2/m, a = 28.6483(15),
C
178
H
79Cl
6
Mn
2
N
11, M
r
=
-
1
2
◦
˚
17 I. A. Mochalov, A. N. Lapshin, V. A. Nadtochenko, V. A. Smirnov and
b = 26.2811(16), c = 19.8784(12) A, b = 101.854(5) , V =
3
-3
-1
N. F. Goldshleger, Russ. Chem. Bull., 2006, 55, 1598.
8 A. N. Lapshin, V. A. Smirnov, R. N. Lyubovskaya and N. F.
Gol’dshleger, Russ. Chem. Bull., 2005, 54, 2338.
˚
1
4647.4(15) A , Z = 4, dcalc = 1.222 g cm , m = 0.339 mm ,
1
◦
F(000) = 5504, 2qmax = 52.74 , reflections measured 52022, unique
reflections 15269, reflections with I > 2s(I) = 6503, parameters
19 R. Koeppe, P. A. Troshin, A. Fuchsbauer, R. N. Lyubovskaya and N.
S. Sariciftci, Fuller. Nanotub. Carb. Nanostruct., 2006, 14, 441.
refined 1104, restraints 1212, R
.081, CCDC reference number is 822366.
X-ray diffraction data for 1 and 3 were collected on an
Oxford diffraction “Gemini-R” CCD diffractometer with graphite
monochromated MoK radiation using an Oxford Instrument
1
= 0.1214, wR
2
= 0.3658, G.O.F. =
2
0 P. A. Troshin, S. I. Troyanov, G. N. Boiko, R. N. Lyubovskaya, A. L.
Lapshin and N. F. Goldshleger, Full. Nanotub. Carb. Nanostr., 2004,
12, 435.
1
2
2
1 F. T. Tat, Z. Zhou, S. MacMahon, F. Song, A. Rheingold, L. Echegoyen,
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a
2
Cryojet system. Raw data reduction to F was carried out using
CrysAlisPro, Oxford Diffraction Ltd. The structures were solved
by direct method and refined by the full-matrix least-squares
23 P. A. Troshin, A. S. Peregudov, D. Muhlbacher and R. N. Lyubovskaya,
Eur. J. Org. Chem., 2005, 3064.
4 P. A. Troshin, A. S. Peregudov, S. M. Peregudova and R. N.
Lyubovskaya, Eur. J. Org. Chem., 2007, 5861.
2
2
45
method against F using SHELX-97. Non-hydrogen atoms were
refined in the anisotropic approximation. Positions of hydrogen
atoms were calculated geometrically. Subsequently, the positions
of H atoms were refined by the “riding” model with Uiso = 1.2Ueq
of the connected non-hydrogen atom.
25 D. M. Guldi, C. Luo, T. DaRos, M. Prato, E. Dietel and A. Hirsch,
Chem. Commun., 2000, 375.
2
2
6 G. Ercolani, M. Ioele and D. Monti, New J. Chem., 2001, 25, 783.
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1
Acknowledgements
9 D. V. Konarev, S. S. Khasanov, A. Otsuka, G. Saito and R. N.
Lyubovskaya, Inorg. Chem., 2007, 46, 2261.
0 D. V. Konarev, S. S. Khasanov, G. Saito and R. N. Lyubovskaya, J.
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The work was supported by the RFBR (grants nos. 09-02-
1514 and 10-03-00443) and the Federal Agency for Science
and Innovations within the Program “Research and scientific-
pedagogic personnel of innovative Russia” (State contract no.
2.740.11.0749) and Russian President Science Foundation (MK-
916.2011.3).
0
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98 | Dalton Trans., 2012, 41, 791–798
This journal is © The Royal Society of Chemistry 2012