Interaction of curved and flat molecular surfaces. The structures of crystalline compounds composed of fullerene (C60, C60O, C70, and C120O) and metal octaethylporphyrin units

Article abstract of DOI:10.1021/ja990618c

Solutions of C₆₀, C⁶⁰O, or C⁷⁰ and metal complexes of octaethylporphyrin (OEPH₂) yield crystals that contain both the fullerene and the porphyrin. The structures of C₆₀'2Co(II)(OEP)·CHCl₃,

Full text of DOI:10.1021/ja990618c

7090
J. Am. Chem. Soc. 1999, 121, 7090-7097
Interaction of Curved and Flat Molecular Surfaces. The Structures of
Crystalline Compounds Composed of Fullerene (C60, C60O, C70, and
C120O) and Metal Octaethylporphyrin Units
Marilyn M. Olmstead,* David A. Costa, Kalyani Maitra, Bruce C. Noll,† Shane L. Phillips,
Pamela M. Van Calcar, and Alan L. Balch*
Contribution from the Department of Chemistry, UniVersity of California, DaVis, California 95616, and
Department of Chemistry, UniVersity of Colorado, Boulder, Colorado 80309
ReceiVed February 26, 1999
Abstract: Solutions of C60, C60O, or C70 and metal complexes of octaethylporphyrin (OEPH2) yield crystals
that contain both the fullerene and the porphyrin. The structures of C60‚2CoII(OEP)‚CHCl3, C60‚2ZnII(OEP)‚
CHCl3, and C60O‚2CoII(OEP)‚CHCl3 are isomorphous and contain an ordered C60 cage surrounded by two
MII(OEP) units. Although there is no covalent bond between the fullerene and porphyrin components, the
separation between these units is shorter than normal van der Waals contact. Crystals of C70‚CoII(OEP)‚C6H6‚
CHCl3, C70‚NiII(OEP)‚C6H6‚CHCl3, and C70‚CuII(OEP)‚C6H6‚CHCl3 are also isomorphous with an ordered
fullerene, but have only one porphyrin/fullerene contact. Crystalline C60‚ClFeIII(OEP)‚CHCl3 lacks the close
face-to-face porphyrin/porphyrin contact that is common to all of the other structures reported here but retains
the intimate contact between the porphyrin and the fullerene. In (C120O)‚CoII(OEP)‚0.6C6H6‚0.4CHCl3 the
fullerene dimer is enclosed by two CoII(OEP) moieties. Unfortunately disorder in the fullerene portion obscures
details of the geometry of the bridging region between the fullerenes.
Introduction
organometallic (e.g. ferrocene7), and inorganic species (e.g. Pd6-
Cl12,8 P4,9 S810).
The unique three-dimensional shapes of the fullerenes coupled
with their distinct physical properties make them attractive
candidates for the construction of larger, supramolecular ag-
gregates. While the synthetic chemist has had decades of
experience using the flat surfaces of aromatic hydrocarbons in
the construction of molecules and molecular arrays, the curved
external surfaces of the fullerenes are unusual and present
interesting challenges in the design of larger assemblies. There
have been several approaches to obtaining curved surfaces that
are able to encircle a fullerene by building complex structures
from planar aromatic hydrocarbon units and other flat moieties.
A number of bowl-shaped molecules including calixarenes,1
cyclodextrins,2 and cyclotriveratrylene3 have been found to form
weak complexes with C60 and other fullerenes. Several of these
assemblies have been structurally characterized. Metal binding
ligands have been designed with portions that can allow flat
benzene rings to encircle C60.4 Solutions of silver nitrate and
Here we report that metal complexes of octaethylporphyrin
cocrystallize with C60 and C70 to form solids in which the two
components make remarkably close contact despite the differ-
ences in external shapes, planar versus highly curved. There
have been a number of molecules created in which a fullerene
and a porphyrin are covalently attached to one another,11-13 but
(6) Balch, A. L.; Lee, J. W.; Noll, B. C.; Olmstead, M. M. J. Chem.
Soc., Chem. Commun. 1993, 56.
(7) Crane, J. D.; Hitchcock, P. B.; Kroto, H. W.; Taylor, R.; Walton, D.
M. R. J. Chem. Soc., Chem. Commun. 1992, 1764. Olmstead, M. M.; Hao,
L.; Balch, A. L. J. Organomet. Chem. 1999, 578, 85.
(8) Olmstead, M. M.; Ginwalla, A. S.; Noll, B. C.; Tinti, D. S.; Balch,
A. L. J. Am. Chem. Soc. 1996, 118, 7737. Balch, A. L.; Olmstead, M. M.
Chem. ReV. 1998, 98, 2123.
(9) Douthwaite, R. E.; Green, M. L. H.; Heyes, S. J.; Rosseinsky, M. J.;
Turner, J. F. C. J. Chem. Soc., Chem. Commun. 1994, 1367.
(10) Bu¨rgi, H. B.; Venugopalan, P.; Schwarzenbach, D.; Diederich, F.;
Thilgen, C. HelV. Chim. Acta, 1993, 76, 2155. Roth, G.; Adelmann, P. J.
Phys. I Fr. 1992, 2, 1541.
C60 yield a black crystalline solid, C60{Ag(NO3)}5, that contains
(11) Ikeda, A.; Fukuhara, C.; Shinkai, S. Chem. Lett. 1997, 407.
Drovetskaya, T.; Reed, C. A.; Boyd, P. D. W. Tetrahedron Lett. 1995, 36,
7971. Imahori, H.; Hagiwara, K.; Akiyama, T.; Taniguchi, S.; Okada, T.;
Sakata, Y. Chem. Lett. 1995, 265. Imahori, H.; Sakata, Y. Chem. Lett. 1996,
199. Akiyama, T.; Imahori, H.; Ajawakom, A.; Sakata, Y. Chem. Lett. 1996,
907. Liddell, P. A.; Kuciauskas, D.; Sumida, J. P.; Nash, B.; Nguyen, D.;
Moore, A. L.; Gust, D. J. Am. Chem. Soc. 1997, 119, 1400. Imahori, H.;
Yamada, K.; Hasegawa, M.; Taniguchi, S.; Okada, T.; Sakata, Y. Angew.
Chem., Int. Ed. Engl. 1997, 36, 2626. Imahori, H.; Sakata, Y. AdV. Mater.
1997, 9, 537. Kuciauskas, D.; Lin, S.; Seely, G. R.; Moore, A. L.; Gust,
D.; Drovetskaya, T.; Reed, C. A.; Boyd, P. D. W. J. Phys. Chem. 1996,
100, 0, 15926.
an infinite, curved silver nitrate network that encapsulates the
fullerene.5 Fullerenes are also well-known to cocrystallize with
a variety of molecules that include organic (e.g. benzene6),
† University of Colorado.
(1) Atwood, J. L.; Barbour, L. J.; Raston, C. L.; Sudria, I. B. N. Angew.
Chem., Int. Ed. 1998, 37, 981. Atwood, J. L.; Koutsantonis, G. A.; Raston,
C. L. Nature 1994, 368, 229.
(2) Yoshida, Z.; Takekuma, H.; Takekuma, S.; Matsubara, Y. Angew.
Chem., Int. Ed. Engl. 1994, 33, 1597.
(3) Steed, J. W.; Junk, P. C.; Atwood, J. L.; Barnes, M. J.; Raston, C.
L.; Burkhalter, R. S. J. Am. Chem. Soc. 1994, 116, 10346.
(4) Balch, A. L.; Catalano, V. J.; Lee, J. W.; Olmstead, M. M. J. Am.
Chem. Soc. 1992, 114, 5455. Catalano, V. J.; Parodi, N. Inorg. Chem. 1997,
36, 537.
(12) Sun, Y.; Drovetskaya, T.; Bolskar, R. D.; Bau, R.; Boyd, P. D. W.;
Reed, C. A. J. Org. Chem. 1997, 62, 3642.
(13) Dietel, E.; Hirsch, A.; Eichhorn, E.; Rieker, A.; Hackbarth, S.; Ro¨der,
B. Chem. Commun. 1998, 1981.
(5) Olmstead, M. M.; Maitra, K.; Balch, A. L. Angew. Chem., Int. Ed.
1999, 38, 231.
(14) Pauling, L. The Nature of the Chemical Bond; 3rd ed.; Cornell
University Press: Ithaca, NY, 1960; p 260.
10.1021/ja990618c CCC: $18.00 © 1999 American Chemical Society
Published on Web 07/20/1999

Interaction of CurVed and Flat Surfaces
J. Am. Chem. Soc., Vol. 121, No. 30, 1999 7091
Figure 1. A view of the C60‚2CoII(OEP) unit in C60‚2CoII(OEP)‚CHCl3
with 50% thermal ellipsoids showing how the two porphyrins surround
the fullerene.
in the work presented here, no covalent links occur between
the constituents.
Results
The compounds reported here were obtained in a form
suitable for single-crystal X-ray diffraction by allowing a
solution of the fullerene in benzene to diffuse into a solution of
the metalloporphyrin in chloroform.
Figure 2. A view emphasizing the ethyl groups that surround the
fullerene in C60‚2CoII(OEP)‚CHCl3.
The Isomorphous Series, C60‚2CoII(OEP)‚CHCl3, C60‚
2ZnII(OEP)‚CHCl3, and C60O‚2CoII(OEP)‚CHCl3. The asym-
metric unit in these three compounds consists of a C60 molecule,
two metalloporphyrins, and one molecule of chloroform. In each
compound the C60 cage is fully ordered. These compounds
crystallize so that two porphyrin molecules surround each
fullerene as shown in Figure 1 for the cobalt complex C60‚2CoII-
(OEP)‚CHCl3. Within this unit the fullerene is positioned
asymmetrically between the two CoII(OEP) units, but the
fullerene is too far from the cobalt atoms for any covalent
bonding between them. The fullerene is positioned so that the
closest approach to the cobalt atom involves 6:6 ring junctions.
The distances from the cobalt atoms to the midpoints of these
C-C bonds are 2.680 and 2.893 Å, respectively. The Co-C
distances are Co(1)‚‚‚C(1), 2.738; Co(1)‚‚‚C(2), 3.198; Co(2′)‚
‚‚C(45), 2.858; and Co(2′)‚‚‚C(46), 2.673 Å. While these
distances are too long to represent coordination, they are shorter
than normal van der Waals contact seen between graphite layers
(3.4 Å),14 between adjacent porphyrins (3.2 Å and larger),15 and
between neighboring fullerenes (greater than 3.2 Å).16
The ethyl groups of both CoII(OEP) portions lie on the same
side of the porphyrin as the fullerene and form an octapoid
embrace about the fullerene. The distances from the center of
the fullerene to the methyl carbons span the range 6.94-7.87
Å. The van der Waals radius of C60 is 5.0 Å, and that of a
methyl group is 2.0 Å.14,16 Thus, the eight methyl groups are
within van der Waals contact of the fullerene. Additionally, the
fullerene is surrounded by the ethyl groups from two other pairs
of CoII(OEP) molecules. Figure 2 shows a drawing of the
molecular packing that emphasizes how the fullerene is nestled
within the ethyl groups of these other cobalt porphyrin
molecules.
their way through the crystal. A portion of a ribbon is shown
in Figure 3. The contact between the two porphyrins places each
cobalt atom nearly directly over a nitrogen atom of the adjacent
porphyrin, but the Co‚‚‚N separation is too long to represent a
covalent interaction.
Selected interatomic distances within the porphyrin portion
of these cocrystals are given in Table 1. The core molecular
geometry of the cobalt porphyrin in C60‚2CoII(OEP)‚CHCl3 is
similar to that found in CoII(OEP) itself,17 as seen in Table 1
where parameters for some simple metalloporphyrins are also
shown. Notice from this table that the face-to-face porphyrin/
porphyrin contact is greater in the fullerene cocrystals than it is
in CoII(OEP) itself. Thus, the lateral shift (LS) and the Co‚‚‚
Co separation (M‚‚‚M) in the fullerene compound are shorter
than they are in CoII(OEP). Additionally the mean plane
separation (MPS) and the LS are shorter in C60‚2CoII(OEP)‚
CHCl3 than in CoII(OEP) itself. This close face-to-face arrange-
ment is facilitated by the positioning of all of the ethyl groups
on the opposite side of the porphyrin from the adjacent
porphyrin. In contrast CoII(OEP) has four ethyl groups on one
side of the porphyrin plane and four on the opposite side.
While C60‚2CoII(OEP)‚CHCl3 and C60‚2ZnII(OEP)‚CHCl3 are
isomorphous, there are some slight differences in the structures.
Again, there is no coordination of the fullerene to zinc, but the
fullerene is more symmetrically positioned between the two
porphyrins in the zinc cocrystal. The distances from the
midpoints of the closest 6:6 fullerene ring junctions to the zinc
ions are 2.971 and 3.082 Å, and the Zn‚‚‚C distances are 2.943,
3.147, 2.985, and 3.321 Å.
C60O,18 like C60, forms a cocrystalline compound with CoII-
(OEP). The fullerene is again asymmetrically positioned between
In addition to these fullerene/porphyrin interactions, there are
significant porphyrin/porphyrin contacts with pairwise, face-
to-face contact. The combination of fullerene/porphyrin and
porphyrin/porphyrin contacts produces helical ribbons that wind
(17) Scheidt, W. R.; Turowska-Tyrk, I. Inorg. Chem. 1994, 33, 1314.
(18) Creegan, K. M.; Robbins, J. L.; Robbins, W. K.; Millar, J. M.;
Sherwood, R. D.; Tindall, P. J.; Cox, D. M.; Smith, A. B., III; McCauley,
J. P., Jr.; Jones, D. R.; Gallagher, R. T. J. Am. Chem. Soc. 1992, 114, 1103.
Elemes, Y.; Silverman, S. K.; Sheu, C.; Kao, M.; Foote, C. S.; Alvarez, M.
M.; Whetten, R. L. Angew. Chem., Int. Ed. Engl. 1992, 31, 351. Balch, A.
L.; Costa, D. A.; Noll, B. C.; Olmstead, M. M. J. Am. Chem. Soc. 1995,
117, 8926.
(15) Scheidt, W. R.; Lee, Y. J. Struct. Bonding (Berlin) 1987, 64, 1.
(16) Bu¨rgi, H. B.; Restori, R.; Schwarzenbach, D.; Balch, A. L.; Lee, J.
W.; Noll, B. C.; Olmstead, M. M. Chem. Mater. 1994, 6, 1325.

7092 J. Am. Chem. Soc., Vol. 121, No. 30, 1999
Olmstead et al.
Figure 3. A view of the helical chains of C60‚2CoII(OEP) in C60‚2CoII(OEP)‚CHCl3.
Table 1. Selected Interatomic Distances
C60‚2CoII(OEP)‚ C60‚2ZnII(OEP)‚ C60O‚2CoII(OEP)‚ C70‚CoII(OEP)‚ C70‚NiII(OEP)‚ C70‚CuII(OEP)‚ C60‚ClFeIII- C120O‚CoII(OEP)‚
CHCl3 CHCl3 CHCl3 C6H6‚CHCl3 C6H6‚CHCl3 C6H6‚CHCl3 (OEP)‚CHCl3 0.4C6H6‚0.6CHCl3
M-N
1.971(5) 1.983(5) 2.089(4) 2.042(5) 1.980(7) 1.986(7)
1.983(6) 1.985(6) 2.054(5) 2.081(5) 1.978(8) 1.967(8)
1.979(6) 1.982(5) 2.030(4) 2.047(5) 1.978(8) 1.976(7)
1.967(6) 1.954(6) 2.036(5) 2.033(4) 1.957(8) 1.962(8)
1.964(5)
1.966(5)
1.964(5)
1.967(5)
1.950(6)
1.956(6)
1.956(6)
1.960(6)
1.961(9)
2.009(8)
1.964(9)
1.993(8)
2.073(8)
1.964(15)
1.966(11)
1.961(15)
M-Cl
M‚‚‚N
2.235(9)
2.980
2.970
3.438
3.63
3.21
1.69
2.592
2.674
3.166
3.68
3.21
1.80
2.955
2.981
3.425
3.61
3.21
1.65
2.965
3.152
2.962
2.936
M‚‚‚M
Ct‚‚‚Ct
MPS
3.392
3.60
3.19
3.485
3.65
3.28
3.407
3.66
3.26
8.079
8.45
2.98
7.91
3.448
3.68
3.21
1.80
LS
1.67
1.60
1.66
M-N4 plane 0.0219
0.1605
0.1402
0.0236
0.0134
0.0320
0.0276
0.0255
0.0114
CoII(OEP)a
NiII(OEP)b
CuII(OEP)d ClFeIII(OEP)c
M-N
1.967(3)
1.975(2)
1.946(4)
1.958(4)
1.996(3)
1.999(3)
2.074
2.076
2.064
2.067
M-Cl
M‚‚‚M
Ct‚‚‚Ct
MPS
2.231
4.742
4.74
3.33
3.38
4.802
4.802
3.44
4.805
4.805
3.43
7.877, 8.193
8.24, 7.69
3.41, 3.42
7.50, 6.89
LS
3.35
3.36
a Data from Scheidt, W. R.; Turowska-Tyrk, I. Inorg. Chem. 1994, 33, 1314. b Data from Brennan, T. D.; Scheidt, W. R.; Shelnutt, J. A. J. Am.
Chem. Soc. 1988, 110, 3919. c Data from Senge, M. Private communication, Cambridge Crystallographic Data Base, TOYRUU. d Data from Pak,
R.; Scheidt, W. R. Acta Crystallogr., Sect. C, 1991, C47, 431.
the two porphyrin molecules with Co-C distances of 2.728,
3.219, 2.670, and 2.840 Å and separations of 2.669 and 2.902
Å between the cobalt atoms and the centers of the adjacent 6:6
ring junctions of the fullerene oxide. Although the C60 cage is
fully ordered, the epoxide oxygen atoms are disordered over
five sites as seen in Figure 4. (In crystalline C60O itself, the
oxygen atoms are disordered over the entire surface of the
fullerene.19) The sum of the occupancies is only 0.71, whereas
the expected occupancy is 1. The reduction in oxygen atom
occupancy may result from additional disorder of the oxygen
atom over sites that are simply too sparsely occupied to be
detected in the available X-ray diffraction data or from the loss
of oxygen from C60O during the time required for crystal growth.
(It is well-known that C60O readily reverts to C60 under a variety
of conditions including chromatography on alumina.18) Never-
theless, the data indicate that the oxygen atoms are all situated
above 6:6 ring functions in epoxide functionalities as seen also
in the crystallographically determined structures of (η2-C60O)-
Ir(CO)Cl(PPh3)2 and (η2-C60O)Ir(CO)Cl(AsPh3)2.20,21
Figure 4. A drawing showing the locations of the five, partially
The Isomorphous Series, C70‚CoII(OEP)‚C6H6‚CHCl3, C70‚
occupied oxygen atom positions in C60O‚2CoII(OEP)‚CHCl3. The
NiII(OEP)‚C6H6‚CHCl3, and C70‚CuII(OEP)‚C6H6‚CHCl3.
occupancies are O1, 0.21(1); O2, 0.17(1); O3, 0.13(1); O4, 0.16(1);
and O5, 0.07(1).
(19) Vaughan, G. B. M.; Heiney, P. A.; Cox, D. E.; McGhie, A. R.;
Jones, D. R.; Strongin, R. M.; Cichy, M. A.; Smith, A. B., III. Chem. Phys.
1992, 168, 185.
The asymmetric unit in each consists of one fully ordered C70
molecule, one metalloporphyrin, and two solvent sites which
may be occupied by chloroform or benzene. The porphyrin/
fullerene interaction, which involves only a single MII(OEP)
(20) Balch, A. L.; Costa, D. A.; Lee, J. W.; Noll, B. C.; Olmstead, M.
M. Inorg. Chem. 1994, 33, 2071.
(21) Balch, A. L.; Costa, D. A.; Noll, B. C.; Olmstead, M. M. Inorg.
Chem. 1996, 35, 458.

Interaction of CurVed and Flat Surfaces
J. Am. Chem. Soc., Vol. 121, No. 30, 1999 7093
furan-like bridge,24-27 was obtained by the solid-state thermoly-
sis of a mixture C60O and C60 and purified by HPLC.23,24 Figure
9 shows a view of the packing of the fullerene and porphyrin
units within this solid. The CoII(OEP)/fullerene and CoII(OEP)/
CoII(OEP) interactions are similar to those seen in C60‚CoII-
(OEP)‚CHCl3 and C70‚CoII(OEP)‚C6H6‚CHCl3. The fullerene
dimer unfortunately suffers from a complex disorder as de-
scribed in the Experimental Section. The two C60 units are
clearly linked by a carbon-carbon single bond. However, the
connections to the oxygen atom of the dimer are poorly defined.
Discussion
Eight new compounds that involve cocrystallization of
fullerenes with porphyrins have been examined by single-crystal
X-ray diffraction. Although fullerenes have a remarkable
propensity for disorder,28 the fullerenes are ordered in C60‚2MII-
(OEP)‚CHCl3 (M ) Co, Zn) and in C70‚MII(OEP)‚C6H6‚CHCl3
(M ) Co, Ni, Cu). In C60O‚2CoII(OEP)‚CHCl3, there is disorder
in the location of the epoxide oxygen atom, but the carbon cage
is ordered. Because the fullerene carbon cages are ordered in
these structures, it is anticipated that cocrystallization with
metalloporphyrins may offer a method of obtaining suitable
crystals of related compounds, i.e. endohedral metallofullerenes,
higher fullerenes, and chemically modified fullerenes, for study
by single-crystal X-ray diffraction. However, in C60‚ClFeIII-
(OEP)‚CHCl3 the fullerene is disordered over four positions,
and in C120O‚CoII(OEP)‚0.6C6H6‚0.4CHCl3 the bridged fullerene
dimer is also disordered.
Figure 5. A view of the fullerene/porphyrin unit in C70‚NiII(OEP)‚
C6H6‚CHCl3 with 30% thermal ellipsoids. The arrows show the location
of the 5-fold axis in C70.
molecule, is shown in Figure 5. The fullerene is positioned so
that the C5 axis of the fullerene makes an angle of 16.4° with
the porphyrin plane in C70‚CoII(OEP)‚CHCl3‚C6H6, 16.2 ° in
C70‚NiII(OEP)‚CHCl3‚C6H6, and 16.6 ° in C70‚CuII(OEP)‚C6H6‚
CHCl3. Again, there is no covalent bonding between the metal
ions and the fullerene. The fullerene is positioned so that one
of the carbon atoms (an atom in layer c of the fullerene) is
positioned almost directly over the metal at the center of the
porphyrin. These short, but nonbonded Co‚‚‚C, Ni‚‚‚C, and
Cu...C distances are 2.800, 2.835, and 2.919 Å, respectively.
The ethyl groups on the porphyrin molecules are arranged
so that they again encircle the C70 molecule and also avoid
contact with the adjacent porphyrin molecules which make close
face-to-face contact. An overall view of the molecular packing
of these solids is shown in Figure 6.
Within these new compounds the fullerene/porphyrin contacts
are all unusually close (with M‚‚‚C distances as short as 2.68
Å), but there is no direct coordination of the fullerene to the
metalloporphyrin. This point is particularly clear in the structure
of C60‚ClFeIII(OEP)‚CHCl3, where the metal and the fullerene
reside on opposite sides of the porphyrin plane. The close
fullerene/porphyrin contacts seen here can be compared to
previously reported cases where arene molecules interact with
metalloporphyrins. For example, in MnII(TPP)‚(CH3C6H5) a
toluene molecule sits over the center of the porphyrin with
distances from the mean porphyrin plane to the carbon atoms
of the toluene that range from 3.12 to 3.4 Å.29 In (ClO4)FeIII-
(TPP)‚0.5(m-(CH3)2C6H4), a similar situation occurs with por-
phyrin mean plane to m-xylene carbon atom distances ranging
from 3.32 to 3.66 Å.30 Closer arene to metalloporphyrin contacts
are seen in [Fe(TTP)][Ag(Br6CB11H6)2]‚4(p-xylene) where two
p-xylene molecules make face-to-face contact with the center
of the porphyrin.31 The closest distance between a xylene carbon
atom and the porphyrin mean plane is 2.89 Å, where the [Fe-
(TPP)]+ unit is tightly solvated by its neighbors.
The internal dimensions of the porphyrins are similar to those
previously reported for CoII(OEP), for the triclinic B form of
NiII(OEP),22 and for CuII(OEP) as can be seen from the data in
Table 1. However, the face-to-face interactions between the
metalloporphyrin components are more extensive in the fullerene
cocrystals than in the simple porphyrin crystals.
C60‚ClFeIII(OEP)‚CHCl3. The asymmetric unit consists of
one-quarter of the iron porphyrin at a site of mm symmetry, a
fullerene (also at a site of mm symmetry), which is disordered
over four positions, and a chloroform molecule. A view of the
porphyrin/fullerene interaction in this solid is shown in Figure
7, while Figure 8 shows a view of the overall molecular packing.
As seen in Figure 7 there is one porphyrin/fullerene interaction.
Again, there is no coordination of the fullerene to the metal;
indeed the iron ion is on the opposite side of the porphyrin from
the fullerene. The distance from the closest fullerene carbon
atom to the N4 plane is 2.748 Å. The ethyl groups are arranged
to embrace the fullerene.
In all structures reported here, the eight ethyl groups of each
metalloporphyrin are arranged so that they form an octopus-
(24) Smith, III, A. B.; Tokuyama, H.; Strongin, R. M.; Furst, G. T.;
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(25) Lebedkin, S.; Ballenweg, S.; Gross, J.; Taylor, R.; Kratschmer, W.
Tetrahedron Lett. 1995, 36, 4971.
(26) Balch, A. L.; Costa, D. A.; Fawcett, W. R.; Winkler, K. J. Phys.
Chem. 1996, 100, 4823.
(27) Penn, S. G.; Costa, D. A.; Balch, A. L.; Lebrilla, C. B. Int. J. Mass
Spectrom. Ion Processes 1997, 169/170, 371.
(28) Bu¨rgi, H. B.; Blanc, E.; Schwarzenbach, D.; Liu, S.; Kappes, M.
M.; Ibers, J. A. Angew. Chem., Int. Ed. Engl. 1992, 31, 640.
(29) Kirner, J. F.; Reed, C. A.; Scheidt, W. R. J. Am. Chem. Soc. 1977,
99, 1093.
The geometry of the porphyrin core and the iron coordination
in C60‚ClFeIII(OEP)‚CHCl3 are similar to those in ClFeIII(OEP)23
itself, as seen from the data in Table 1. However, in ClFeIII-
(OEP) the molecular packing gives rise to a different distribution
of ethyl group orientations, with five lying on one side of the
porphyrin and three on the opposite side, the side that includes
the Fe-Cl portion.
C120O‚CoII(OEP)‚0.4C6H6‚0.6CHCl3. The fullerene oxide,
120O, which consists of two C60 cages joined by a tetrahydro-
C
(30) Reed, C. A.; Mashiko, T.; Bentley, S. P.; Kastner, M. E.; Scheidt,
W. R.; Spartalian, K.; Lang, G. J. Am. Chem. Soc. 1979, 101, 2948.
(31) Xie, Z.; Bau, R.; Reed, C. A. Angew. Chem., Int. Ed. Engl. 1994,
33, 2433.
(22) Brennan, T. D.; Scheidt, W. R.; Shelnutt, J. A. J. Am. Chem. Soc.
1988, 110, 3919.
(23) Senge, M. Personal communication. CSD file TOYRUU.

7094 J. Am. Chem. Soc., Vol. 121, No. 30, 1999
Olmstead et al.
Figure 6. A stereoview of the molecular packing in C70‚CoII(OEP)‚C6H6‚CHCl3.
Figure 7. A view of the fullerene/porphyrin units in C60‚ClFeIII(OEP)‚
CHCl3 with 50% thermal ellipsoids.
Figure 8. A drawing that shows the molecular packing in C60‚ClFeIII-
(OEP)‚CHCl3.
like embrace of the fullerene surface. This orientation of the
ethyl groups also facilitates the adjoining porphyrin/porphyrin
interactions.
entirely surrounded by C-H groups from the two MII(OEP)
units that encapsulate the fullerene as well as from two adjacent
pairs of MII(OEP) units that sit off to the other side of the
fullerene. Consequently the center to center distance between
the fullerenes in this family is quite large, ca. 13.09 Å. In the
series C70‚CoII(OEP)‚C6H6‚CHCl3, C70‚NiII(OEP)‚C6H6‚CHCl3,
and C70‚CuII(OEP)‚C6H6‚CHCl3, the closest contacts between
C70 molecules are 3.486, 3.438, and 3.395 Å, respectively. In
C60‚ClFeIII(OEP)‚CHCl3 the shortest separation between the
centers of the C60 molecules that lie in the plane shown in Figure
8 is 9.80 Å, which compares to the spacing of 9.94 Å (at 110
K) that is seen in C60 itself.
Examination of the planarity of the MN4 portion of the
metalloporphyrins in the new compounds reported here shows
that the metal protrudes only slightly from the plane of the four
nitrogen donors. Relevant data, the distances of the metal from
the N4 plane, are given in Table 1 as the M-N4 plane distances.
The deviations are small and range from 0.0114 to 0.1605 Å.
Those for the zinc compound are an order of magnitude larger
For the four-coordinate metalloporphyrins, the face-to-face
stacking of pairs of MII(OEP) units is also a prominent feature
of the structures with both C60 and with C70. Scheidt and Lee
have previously classified such interactions as weak when the
lateral shift is greater than 4.5 Å, intermediate when the lateral
shift is about 3.5 Å, and strong when this shift is about 1.5 Å.15
In this scheme, the face-to-face interactions of the four-
coordinate metalloporphyrins are all strong in the fullerene
cocrystals. In contrast, in the porphyrin-porphyrin arrangements
in CoII(OEP) itself and in the triclinic B form of NiII(OEP) they
correspond to intermediate face-to-face interactions. However,
in five-coordinate ClFeIII(OEP) the position of the Fe-Cl bond
prohibits such close contact, and consequently in C60‚ClFeIII-
(OEP)‚CHCl3 the face-to-face interaction is weak.
Cocrystallization of these fullerenes with the metalloporphy-
rins by necessity changes the nature of the fullerene/fullerene
contacts from those seen in pure crystalline fullerenes. As seen
in Figure 2, in the C60‚2CoII(OEP)‚CHCl3, C60‚2ZnII(OEP)‚
CHCl3, and C60O‚2CoII(OEP)‚CHCl3 family, the fullerenes are

Interaction of CurVed and Flat Surfaces
J. Am. Chem. Soc., Vol. 121, No. 30, 1999 7095
Figure 9. The molecular packing of fullerenes and porphyrins in C120O‚CoII(OEP)‚O.4C6H6‚0.6CHCl3. Only one set of four orientations of the C60
units is shown.
than those of the corresponding cobalt complexes. In all cases
the metal ions are displaced from the N4 plane in such a fashion
that they are closer to the immediately adjacent porphyrin and
further from the neighboring fullerene.
complete quenching of the expected porphyrin fluorescence at
500 nm. Another set of covalently linked dyads containing C60
and porphyrins have been reported.38 A variety of metal-free
tetra(substituted-aryl)porphyrins have also been found to form
cocrystals with C60.39
The cocrystallizations reported here may be facilitated by
charge-transfer interactions between the porphyrin and the
fullerene, with the fullerene acting as an acceptor and the
metalloporphyrin as a donor. A number of studies have been
made of the interaction of metalloporphyrins with strong organic
π-acceptors such as trinitrobenzene.32 The acceptor properties
of the fullerenes are a consequence of their ease of reduction.33
Chromatographic materials with appended porphyrins have
been developed for the separation of fullerenes.34 The porphyrin/
fullerene interactions seen in these cocrystallized materials
provide a model for the porphyrin/fullerene interactions that
occur during chromatography. Interactions of fullerenes with
one or two porphyrin units have been considered as part of the
chromatographic process.
Other cases are known where fullerenes and related large flat
molecules are found in close proximity. Crystalline C60‚2octakis-
(dimethylamino)porphyrazine‚C6H5CH3 has a structure similar
to that of C60‚2CoII(OEP)‚CHCl3 with two of the macrocycles
cupping the fullerene.35 However, in this structure the fullerene
portion is disordered over several orientations. The planar
porphyrazine molecules are arranged in a face-to-face fashion.
The pyrrolidine-linked tetraphenylporphyrin/C60 dyad, 1, crys-
tallizes in a fashion that places the fullerene of one molecule in
close proximity to the porphyrin plane of another.36 An unusual
donor/acceptor relationship, in which the fullerene acts as a
donor and the porphyrin acts as the acceptor, was proposed for
the intermolecular interactions in crystalline 1. The C60/
porphyrin dyad, 2, was synthesized with covalent links that
enforce proximity of the porphyrin and fullerene.37 Evidence
of π-π stacking of the two components comes from the
bathochromic shift of the Soret and Q-bands of the zinc
porphyrin in the dyad relative to the free porphyrin and the
C60 as well as the cage molecules, 1,2-dicarbadodecaborane
and P4S3, have also been found to cocrystallize with the nickel
complex, 3.40 In these crystals each side of the saddle-shaped
nickel complex interacts with a fullerene molecule. It remains
to be seen whether porphyrins that have saddle shapes due to
steric encumbrances on the periphery can cocrystallize with
fullerenes. However, in that context it is interesting to note that
NiII(OEP), which does crystallize in both planar and saddle-
shaped modifications, assumes a planar geometry when it
cocrystallizes with C70.
(32) Barry, C. D.; Hill, H. A. O.; Mann, B. E.; Sadler, R. J.; Williams,
R. P. J. J. Am. Chem. Soc. 1973, 95, 4545. Walker, F. A. J. Magn. Reson.
1974, 15, 201. Fulton, G. P.; LaMar, G. N. J. Am. Chem. Soc. 1976, 98,
2124.
(33) Echegoyen, L.; Echegoyen, L. E. Acc. Chem. Res. 1998, 31, 593.
(34) Kibbey, C. E.; Savina, M. R.; Parseghian, B. K.; Francis, A. H.;
Meyerhoff, M. E. Anal. Chem. 1993, 65, 3717. Martin, G. B.; Xiao, J.;
Savina, M. R.; Wilks, M.; Francis, A. H.; Meyerhoff, M. E. Recent AdVances
in the Chemistry and Physics of Fullerenes, Electrochemical Society
Proceedings 1994, 94-24, 178. Xiao, J.; Meyerhoff, M. E. J. Chromatogr.
A 1995, 715, 19. Xiao, J.; Savina, M. R.; Martin, G. B.; Francis, A. H.;
Meyerhoff, M. E. J. Am. Chem. Soc. 1994, 116, 9341.
Tetra(aryl)porphyrins and their metal complexes are known
to act as “porphyrin sponges” in which they cocrystallize with
hundreds of foreign guest molecules.41 That behavior is distinct
from what we report here. The porphyrin sponges generally
(38) Bourgeois, J. P.; Diederich, F.; Echegoyen, L.; Nierengarten, J. F.
HelV. Chim. Acta 1998, 81, 1835.
(39) Boyd, B. D. W.; Reed, C. A.; and co-workers. Reported at the
Electrochemical Society Meeting, San Diego, CA, May, 1998.
(40) Andrews, P. C.; Atwood, J. L.; Barbour, L. J.; Nichols, P. J.; Raston,
C. L. Chem. Eur. J. 1998, 4, 1384.
(35) Eichhorn, D. M.; Yang, S.; Jarrell, W.; Baumann, T. F.; Beall, L.
S.; White, A. J. P.; Williams, D. J.; Barrett, A. G. M.; Hoffman, B. M. J.
Chem. Soc., Chem. Commun. 1995, 1703.
(36) Sun, Y.; Drovetskaya, T.; Bolskar, R. D.; Bau, R.; Boyd, P. D. W.;
Reed, C. A. J. Org. Chem. 1997, 62, 3642.
(37) Dietel, E.; Hirsch, A.; Eichhorn, E.; Rieker, A.; Hackbarth, S.; Ro¨der,
B. Chem. Commun. 1998, 1981.
(41) Byrn, M. P.; Curtis, C. J.; Khan, S. I.; Sawin, P. A.; Tsurumi, R.;
Strouse, C. E. J. Am. Chem. Soc. 1990, 112, 1865. Byrn, M. P.; Strouse, C.
E. J. Am. Chem. Soc. 1991, 113, 2501. Byrn, M. P.; Curtis, C. J.; Goldberg,
I.; Hsiou, Y.; Khan, S. I.; Sawin, P. A.; Tendick, S. K.; Strouse, C. E. J.
Am. Chem. Soc. 1991, 113, 6549. Byrn, M. P.; Curtis, C. J.; Hsiou, Y.;
Khan, S. I.; Sawin, P. A.; Tendick, S. K.; Terzis, A.; Strouse, C. E. J. Am.
Chem. Soc. 1993, 115, 9480.

7096 J. Am. Chem. Soc., Vol. 121, No. 30, 1999
Olmstead et al.
involve intercalation of guests into channels that occur between
tightly packed porphyrin stacks. The close approach of the
fullerene to the porphyrin which characterizes the solids
described here is not a prominent feature in the structures of
the porphyrin sponges.
Experimental Section
Preparation of Crystals. C70‚NiII(OEP)‚C6H6‚CHCl3. A 0.0005 g
(0.0006 mmol) sample of C70 was dissolved in a minimum volume of
benzene, and the solution was filtered and then carefully layered over
a filtered solution of 0.006 g (0.001 mmol) of NiII(OEP) dissolved in
a minimum volume of chloroform in a 5 mm o.d. glass tube. The
resultant mixture was allowed to stand for 6-8 days during which dark
crystals of the product formed. These were collected by decantation of
the solvent to yield 0.0015 g (37%) of product. The other cocrystallized
samples were prepared by a similar procedure from their respective
components.
X-ray Data Collection. All crystals were coated with a light
hydrocarbon oil and mounted on a glass fiber in the cold dinitrogen
stream of the diffractometer. Data for C60O‚2CoII(OEP)‚CHCl3, C60‚
ClFeIII(OEP)‚CHCl3, C70‚NiII(OEP)‚C6H6‚CHCl3, and C120O‚CoII(OEP)‚
0.4C6H6‚0.6CHCl3 were collected on a Siemens P4 diffractometer with
nickel-filtered Cu KR (λ ) 1.541 78 Å) radiation from a rotating anode
source, while data for C60‚2CoII(OEP)‚CHCl3, C60‚2ZnII(OEP)‚CHCl3,
C70‚CoII(OEP)‚C6H6‚CHCl3, and C70‚CuII(OEP)‚C6H6‚CHCl3 were col-
lected on a Siemens SMART CCD with graphite-monochromated Mo
KR radiation. Lorentz and polarization corrections were applied. Check
reflections were stable throughout data collection. Crystal data are given
in Table 2.
Solution and Structure Refinement. Calculations for the structures
were performed using SHELXS-97 and SHELXL-97. Tables of neutral
atom scattering factors, f ′ and f′′, and absorption coefficients are from
a standard source.42 The structures were all solved by direct methods.
All atoms except disordered atoms and hydrogen atoms were refined
anisotropically. Hydrogen atoms were included through the use of a
riding model. For C60‚ClFeIII(OEP)‚CHCl3, an empirical absorption
correction was used,43 while for C60‚2CoII(OEP)‚CHCl3, C60‚2ZnII-
(OEP)‚CHCl3, and C70‚CoII(OEP)‚C6H6‚CHCl3 a semiempirical method
utilizing equivalents was employed.44 Absorption corrections were not
applied to the structures of C60O‚2CoII(OEP)‚CHCl3, C70‚NiII(OEP)‚
C6H6‚CHCl3, and C120O‚CoII(OEP)‚0.4C6H6‚0.6CHCl3.
The structures of C60‚2CoII(OEP)‚CHCl3, C60‚2ZnII(OEP)‚CHCl3, and
C60O‚2CoII(OEP)‚CHCl3 were refined as racemic twins with the twin
parameters refining to 0.48(2), 0.49(2), and 0.531(9), respectively. For
C70‚CoII(OEP)‚C6H6‚CHCl3, C70‚NiII(OEP)‚C6H6‚CHCl3, and C70‚CuII-
(OEP)‚C6H6‚CHCl3, the structure of the C70 molecule was constrained
to D5h symmetry by the application of same-distance restraints (SADI
0.01) to equivalent distances about the 5-fold axis. In addition, the nine
parallel layers of carbon atoms within the C70 molecules were restrained
to be flat (FLAT 0.001). For anisotropic refinement of the fullerene
molecule in C70‚CoII(OEP)‚C6H6‚CHCl3, a restraint (DELU 0.001) was
applied to the components of the tensor along the C-C bonds. There
is large thermal motion of the fullerene in this structure, but there is
no apparent disorder. Two different sites are disordered with respect
to occupation by both benzene and chloroform. Identification of the
individual components was possible, and they were modeled as follows.
Site 1 contained 0.50 benzene (C71-C76 as an idealized hexagon)
and 0.50 chloroform (C1S, H1S, Cl1, Cl2, Cl3). Site 2 contained 0.50
benzene (C77-C82 as an idealized hexagon), 0.30 chloroform (C2S,
H2S, Cl4A, Cl5A, Cl6A), and 0.20 chloroform (C2T, H2T, Cl4B, Cl5B,
Cl6B) with the chloroform molecules refined as rigid groups.
The structure of C60‚ClFeIII(OEP)‚CHCl3 was refined using a rigid
group for the C60 molecule with an occupancy of 0.25 to coincide with
the mm symmetry of the site. The C60 molecule itself does not reside
(42) International Tables for Crystallography; Wilson, A. J. C., Ed.;
Kluwer Academic Publishers: Dordrecht, 1992; Vol. C.
(43) Parkin, S.; Moezzi, B.; Hope, H. J. Appl. Crystallogr. 1995, 28,
53.
(44) Blessing, R. H. Acta Crystallogr., Sect. A 1995, A51, 33.

Interaction of CurVed and Flat Surfaces
J. Am. Chem. Soc., Vol. 121, No. 30, 1999 7097
exactly on the mm site but is slightly shifted and rotated away from it.
The refinement is more stable in the space group Cmcm than in Cmc21.
Although the porphyrin portion of the structure of C120O‚CoII(OEP)‚
0.4C6H6‚0.6CHCl3 refined normally, the fullerene portion is highly
disordered and required special treatment. The point symmetry of the
However, due to the complex disorder, the actual connectivity of the
oxygen atom to the fullerenes cannot be stated with certainty. The
structure also contains disorder in the solvent region, where a benzene
molecule and a chloroform molecule share a site with mirror symmetry.
Using restraints and the site symmetry, relative occupancies were
determined by refinement and subsequently fixed. The final refinement
placed the occupancy of benzene at 40% and of chloroform at 60%.
Hydrogen atoms on the porphyrin were refined using a riding model,
while hydrogen atoms on the disordered benzene and chloroform
molecules were placed at calculated positions and subsequently fixed.
Anisotropic thermal parameters were utilized only for the porphyrin.
C120O molecule is 2/m. Rigid body refinement of the C60 portion in
the asymmetric unit revealed a second molecule of C60 unit which was
rotated approximately by 30° with respect to a 3-fold axis of the first.
The two balls were refined with sufficient restraints to individually
describe the icosohedral symmetry but with looser restraints in the
region of bonding to the bridging oxygen atom. The occupancies of
each were allowed to refine as x and 0.5 - x, and converged to
approximately 0.333/0.167 for the two balls {C1-C60} and {C1B-
C60B}. Subsequent refinement was carried out with each ball treated
as a rigid group, their group thermal parameters refining. For {C1-
C60} the thermal parameter was 0.083(4), and for {C1B-C60B} it
was 0.091(2). Occupancies were fixed as previously determined. The
unique oxygen atom was refined at 0.25 occupancy, and its thermal
parameter converged at 0.071(10). A very weak restraint of 1.60(5) Å
for the O-C distances that are nearest to each other was also applied.
Acknowledgment. We thank the National Science Founda-
tion (Grant CHE 9610507) for support.
Supporting Information Available: Tables of crystal data
(PDF). X-ray crystallographic files (CIF). This material is
available free of charge via the Internet at http://pubs.acs.org.
JA990618C