Communication pubs.acs.org/IC
New Giant Fullerenes Identified as Chloro Derivatives: IsolatedPentagon-Rule C108(1771)Cl12 and C106(1155)Cl24 as well as Nonclassical C104Cl24 Song Wang,† Shangfeng Yang,*,† Erhard Kemnitz,‡ and Sergey I. Troyanov*,§ †
Hefei National Laboratory for Physical Sciences at Microscale, CAS Key Laboratory of Materials for Energy Conversion & Department of Materials Science and Engineering, University of Science and Technology of China (USTC), Hefei 230026, China ‡ Institute of Chemistry, Humboldt University of Berlin, Brook-Taylor.-Str.2, 12489 Berlin, Germany § Chemistry Department, Moscow State University, Leninskie Gory, 119991 Moscow, Russia S Supporting Information *
also contain a chloride with a nonclassical (NC) carbon cage, C104(NC)Cl24, in the same crystallographic site. The fractions of higher fullerenes have been obtained by multistep HPLC of the extracts from arc-discharge fullerene synthesis performed in toluene including the recycling mode in the last steps (see the Supporting Information for details). According to mass-spectrometric measurements, the HPLC fraction I contained mainly C104 with small admixtures of C102 and C106, whereas fraction II was C106 admixed with C104 and C108. Fraction I was chlorinated with VCl4 and a drop of SbCl5 in a glass ampule at 350 °C for 4 weeks, whereas fraction II reacted with pure VCl4 in a glass ampule at 350 °C for 8 weeks. The chlorination products of fraction I gave, after washing with concentrated HCL and water, two types of crystals. An X-ray diffraction study using synchrotron radiation revealed the larger needle-like crystals to be C104(234)Cl22, which was already reported in ref 4b. The smaller, cornel-like orange crystals of the second type showed the presence of C106Cl24 and C104Cl24 in the same crystallographic site.9 The very small, plate-like crystals from chlorination products of fraction II gave (in spite of the larger content of C106) the crystal structure of C108Cl12.9 The crystal structure of C106/C104Cl24 is remarkable because it contains two molecules of fullerene chlorides with similar shape but different carbon cages. The most probable interpretation supposes the presence of C2-C106(1155)Cl24 (23%) and C1C104(NC)Cl24 (77%, in two orientations rotated by 180°) in the same crystallographic site (Figure 1). The overlap of three components is favored because both molecules possess the same chlorination pattern with exact or approximate 2-fold symmetry, which defines their similar shape. Therefore, their inclusion into the common crystal packing is not hampered by minor differences of the carbon cages such as a position of one C−C bond or even the absence of a C2 unit. Similar phenomena of cocrystallization of fullerene chlorides with similar chlorination patterns but slightly different cages were reported previously for C78(2,3)Cl18,10a C90(34,46)Cl32,10b and, as an example of different carbon cages, C100(417)Cl28 and C98(NC)Cl26.3b The C2-C106(1155)Cl24 has a remarkable chlorination pattern which is characterized by the presence of four isolated CC
ABSTRACT: High temperature chlorination of HPLC fractions of higher fullerenes followed by single crystal Xray diffraction with the use of synchrotron radiation resulted in the structure determination of IPR C106(1155)Cl24 and IPR C108(1771)Cl12. C106(1155)Cl24 is cocrystallized with C104Cl24, a chloride of the nonclassical isomer of C104. The moderately stable isomer C106(1155) and the most stable C108(1771) represent so far the largest pristine fullerenes with known cages.
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ass-spectrometric studies of the extracts from the fullerene soot revealed that they contain, besides C60 and C70, many higher fullerenes with sizes up to C418.1 However, the investigation of higher fullerenes is hampered by their low abundances which decrease drastically with increasing sizes of the carbon cages. In addition, higher fullerenes can exist as numerous isomers which further complicate their identification.2 These difficulties become more severe for so-called giant fullerenes consisting of 100 or more carbon atoms. Pristine giant fullerenes with experimentally determined cage structures are so far known for C100 (five isomers),3 C102 (two isomers),4 and C104 (four isomers),4b,5 all of which have been isolated as chloro derivatives and investigated by single crystal X-ray diffraction. The largest structurally characterized endohedral fullerene, Sm2@C104(822) (isomer numbering according to the spiral algorithm2), was studied in cocrystals with NiIIOEP (OEP = octaethylporphyrin).6 In the absence or the scarcity of the experimental structural data, computational studies of the formation energy of different isomers provide an estimate for most probable isomers which can be found experimentally. Generally, the experimental data confirm the existence of the energetically most stable pristine isomers, as has been established for C90(45),7a C94(133),7b C96(183),7c C98(248),7d C102(603),4b and C104(234).4b However, some less stable and even highly unstable isomers such as C96(3)8 or C100(1)3a have been found in the fullerene soot. Herein, we report the isolation and structural identification of chloro derivatives of the first isomers of giant isolatedpentagon-rule fullerenes C106 and C108, C106(1155)Cl24, and C108(1771)Cl12, respectively. The crystals with C106(1155)Cl24 © 2016 American Chemical Society
Received: March 31, 2016 Published: June 8, 2016 5741
DOI: 10.1021/acs.inorgchem.6b00809 Inorg. Chem. 2016, 55, 5741−5743
Communication
Inorganic Chemistry
9676 possible C104 cages containing one heptagon and 13 pentagons (but no fused pentagons). When compared with classical IPR isomers of C104, C104(NC) is only 40 kJ mol−1 higher than the most stable isomer C104(234). It is worth noting that IPR isomers of C104 confirmed experimentally include C104(811) and C104(258) with relative formation energies of 44 and 57 kJ mol−1, respectively.5 In fact, the starting fullerene mixture used for the chlorination experiment contained much less C106 than C104 according to the MS analysis (with isomer C104(234) definitely present as confirmed previously4b). The situation with C104(NC) as a possible component of fullerene soot is very similar to that reported recently for C100(NC), the presence of which was postulated based on its low calculated formation energy (21 kJ mol−1) relative to the most stable classical IPR isomer C100(449).3b Notably, both C104(NC) and C100(NC) have the same environment of a heptagon by three edge-sharing pentagons and one more distant pentagon as shown for C104(NC) in Figure 1. The molecular structure of C2-C108(1771)Cl12 is shown in three projections in Figure 2. The carbon cage is a little
Figure 1. Perspective views and Schlegel diagrams of C1-C104(NC)Cl24 and C2-C106(1155)Cl24. In the side projection and Schlegel diagram of C104(NC)Cl24, the cage heptagon is blue, whereas the surrounding pentagons are shown in red. Both the projection and Schlegel diagram of C106(1155)Cl24 are given along the molecular C2 axis. In the Schlegel diagrams, black circles denote the positions of attached Cl atoms. Isolated CC bonds and benzenoid rings are indicated.
bonds and seven benzenoid rings entirely or nearly isolated by sp3 carbons on the carbon cage. The carbon cage of C2C106(1155)Cl24 is somewhat flattened due to the presence of coronene and pyrene substructures on the poles of the molecule. Another unusual feature of the chlorination pattern is the attachment of four Cl atoms to the positions of triple hexagon junctions (THJs) which are generally less suitable for additions in fullerenes.11 In the case of C2-C106(1155)Cl24, each addition in the position of THJ results in the formation of two or even three benzenoid rings, thus contributing to the stabilization of the whole chlorination pattern. According to our calculations on the DFT level of theory using the PRIRODA package,12 C106(1155) possesses a moderate stability among 1233 topologically possible IPR isomers of C106 with its formation energy being 34 kJ mol−1 above that of the most stable isomer C106(534).13 It is known that some experimentally isolated higher fullerene isomers have relative formation energies of 50 kJ mol−1 or even higher.3a,8 The nonclassical carbon cage of the C1-C104(NC)Cl24 molecule differs from that of C2-C106(1155)Cl24 by a rotated CC bond in one cage region and the presence of a heptagon in another cage region. Therefore, there are only six benzenoid rings on the carbon cage and only two Cl attachments in THJs. At the same time, the addition positions of 24 Cl atoms in both molecules are very similar. The origin of the C104(NC) cage can be thought of as a result of C2 loss from C106(1158) (the relative formation energy is 38 kJ mol−1) upon chlorination. This assumption is not supported by the fact that there are no fused pentagons around the heptagon as typically observed for most known examples of C2 unit abstractions from fullerene cages.14 Alternatively, it can be assumed that isomer C104(NC) was initially present in the fullerene fraction used for chlorination. The calculation of the formation energy revealed that isomer C104(NC) belongs to the set of the most stable isomers of all
Figure 2. Perspective views and Schlegel diagram of C 2 C108(1771)Cl12. Both projections in the upper row are given orthogonal to the 2-fold axis, whereas the projection below is along the C2 axis. On the Schlegel diagram, cage pentagons are shown gray; black circles denote the positions of attached Cl atoms. The crosses mark the position of a 2-fold axis.
flattened due to the presence of several coronene substructures near the poles of the molecule. The isolation of a chloro derivative of just isomer D2-C108(1771) was rather expected because, according to theoretical calculations,12,15 this isomer is one of the most stable (with a significant HOMO−LUMO gap) among 1799 IPR isomers; it was thus predicted to be easier isolated than other isomers of C108.15 With respect to the chlorination pattern of C 2 C108(1771)Cl12, 12 chlorine attachments are distributed unequally on the C108 cage so that four pentagons bear no Cl atoms whereas four of the remaining eight pentagons are occupied with two Cl atoms each. Usually, the most stable addition patterns of the derivatives with 12 attached atoms or groups is characterized by their uniform distribution on the fullerene cages as in the known molecular structures of chloro (C70,16a C80,16b and C1003a) or trifluoromethyl derivatives 5742
DOI: 10.1021/acs.inorgchem.6b00809 Inorg. Chem. 2016, 55, 5741−5743
Communication
Inorganic Chemistry (C60,17a C70,17b C80,17c and C84,17d). A few exceptions from this rule were reported for derivatives with 12 or even more attached atoms or groups containing empty cage pentagons as in the structures of C88Cl12/16/24,7d,18a C78(2)(CF3)12,18b and some others. These deviations from the general rule are accounted for by the formation of stabilizing substructures on the carbon cages such as benzenoid rings or isolated CC bonds. A special feature of the chlorination pattern of C2C108(1771)Cl12 is that two separate regions on the carbon cage include both para and ortho additions of Cl atoms, but no stabilizing substructures are present. Elongated C−C bonds radiating from carbon atoms bearing Cl atoms of the sp2−sp3 type are, on average, 1.518 Å long, whereas four bonds of the sp3−sp3 type are significantly longer, av. 1.619 Å. C−Cl bonds have an average bond length of 1.823 Å, which is typical for chloro derivatives of fullerenes.16a In fact, two cage regions, each with six pentagons, are separated by the extended region of coronene substructures so that the single addition chain cannot be formed. Within the model of C2 symmetry with two separate chains, we carried out the calculations of formation energy of several possible isomers of C108(1771)Cl12 containing more (or exclusively) para additions of 12 Cl atoms. However, the formation energies of all these hypothetical isomers were a little (or significantly) higher than that of the experimental C2-C108(1771)Cl12. It can be suggested that the next steps of chlorination, if they occurred, would involve the positions on the second hemisphere of the D2-C108(1771) cage. In summary, two IPR isomers of pristine giant fullerenes C108 and C106 have been isolated and structurally characterized as chloro derivatives, C108(1771)Cl12 and C106(1155)Cl24, for the first time. The latter was found to cocrystallize with nonclassical C104(NC)Cl24, the formation of which is, most probably, due to the presence of nonclassical C104(NC) in the fullerene soot. Therefore, the chlorination of separated fullerene fractions followed by X-ray diffraction study is proven to be very effective in discovery and investigation of giant fullerenes in spite of their extremely low abundance in the fullerene soot.
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489/39-2), and the Russian Foundation for Basic Research (grants 15-03-004464 and 16-53-53012).
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(1) Beer, F.; Gügel, A.; Martin, K.; Räder, J.; Müllen, K. J. Mater. Chem. 1997, 7, 1327. (2) Fowler, P. W.; Manolopoulos, D. E. An Atlas of Fullerenes; Clarendon Press: Oxford, UK, 1995. (3) (a) Fritz, M. A.; Kemnitz, E.; Troyanov, S. I. Chem. Commun. 2014, 50, 14577. (b) Wang, S.; Yang, S.; Kemnitz, E.; Troyanov, S. I. Angew. Chem., Int. Ed. 2016, 55, 3451. (4) (a) Yang, S.; Wei, T.; Wang, S.; Ignat’eva, D. V.; Kemnitz, E.; Troyanov, S. I. Chem. Commun. 2013, 49, 7944. (b) Yang, S.; Wang, S.; Troyanov, S. I. Chem. - Eur. J. 2014, 20, 6875. (5) Yang, S.; Wei, T.; Kemnitz, E.; Troyanov, S. I. Chem. - Asian J. 2014, 9, 79. (6) Mercado, B. Q.; Jiang, A.; Yang, H.; Wang, Z.; Jin, H.; Liu, Z.; Olmstead, M. M.; Balch, A. L. Angew. Chem., Int. Ed. 2009, 48, 9114. (7) (a) Tamm, N. B.; Troyanov, S. I. Chem. - Asian J. 2015, 10, 1622. (b) Tamm, N. B.; Yang, S.; Wei, T.; Troyanov, S. I. Inorg. Chem. 2015, 54, 2494. (c) Yang, S.; Wei, T.; Kemnitz, E.; Troyanov, S. I. Angew. Chem., Int. Ed. 2012, 51, 8239. (d) Wang, S.; Yang, S.; Kemnitz, E.; Troyanov, S. I. Chem. - Asian J. 2016, 11, 77. (8) Yang, H.; Jin, H.; Che, Y.; Hong, B.; Liu, Z.; Gharamaleki, J. A.; Olmstead, M. M.; Balch, A. L. Chem. - Eur. J. 2012, 18, 2792. (9) Synchrotron X-ray data were collected at 100 K at the BESSY storage ring (BL14.2, PFS, Berlin, Germany) using a MAR225 CCD detector, λ = 0.88561 Å. C106(1155)Cl24/C104(NC)Cl24 (occupancy ratio 0.23/0.77): monoclinic, C2/c, a = 23.306(2) Å, b = 12.322(1) Å, c = 27.987(3) Å, β = 113.423(12)°, V = 7374.9(13) Å3, Z = 4, R1(F)/ wR2(F2) = 0.074/0.181 for 4808/8171 reflections and 650 parameters. C108(1771)Cl12: triclinic, P1̅, a = 11.381(1) Å, b = 14.734(1) Å, c = 20.500(1) Å, α = 71.256(7)°, β = 74.043(10°, γ = 70.057(10)°, V = 3006.8(4) Å3, Z = 2, R1(F)/wR2(F2) = 0.102/0.224 for 4569/11 342 reflections and 1081 parameters. (10) (a) Simeonov, K. S.; Amsharov, K. Yu.; Jansen, M. Chem. - Eur. J. 2008, 14, 9585. (b) Kemnitz, E.; Troyanov, S. I. Angew. Chem., Int. Ed. 2009, 48, 2584. (11) Amsharov, K. Yu.; Simeonov, K. S.; Jansen, M. Fullerenes, Nanotubes, Carbon Nanostruct. 2010, 18, 427. (12) (a) Laikov, D. N. Chem. Phys. Lett. 1997, 281, 151. (b) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. Rev. Lett. 1996, 77, 3865. (13) Wang, M. Q.; Liu, J. C.; Li, W. Q.; Zhou, X.; Tian, W. Q. J. Phys. Chem. C 2015, 119, 7408. (14) (a) Yang, S.; Wei, T.; Wang, S.; Ioffe, I. N.; Kemnitz, E.; Troyanov, S. I. Chem. - Asian J. 2014, 9, 3102. (b) Yang, S.; Wei, T.; Scheurell, K.; Kemnitz, E.; Troyanov, S. I. Chem. - Eur. J. 2015, 21, 15138. (c) Ioffe, I. N.; Yang, S.; Wang, S.; Kemnitz, E.; Sidorov, L. N.; Troyanov, S. I.; Sidorov, L. N. Chem. - Eur. J. 2015, 21, 4904. (15) Shao, N.; Gao, Y.; An, W.; Zeng, X. C.; Yoo, S. J. Phys. Chem. A 2006, 110, 7672. (16) (a) Troyanov, S. I.; Kemnitz, E. Curr. Org. Chem. 2012, 16, 1060. (b) Simeonov, K. S.; Amsharov, K. Yu.; Jansen, M. Chem. - Eur. J. 2009, 15, 1812. (17) (a) Troyanov, S. I.; Dimitrov, A.; Kemnitz, E. Angew. Chem., Int. Ed. 2006, 45, 1971. (b) Ignat’eva, D. V.; Goryunkov, A. A.; Tamm, N. B.; Ioffe, I. N.; Avdoshenko, S. M.; Sidorov, L. N.; Dimitrov, A.; Kemnitz, E.; Troyanov, S. I. Chem. Commun. 2006, 1778. (c) Yang, S.; Wei, T.; Tamm, N. B.; Kemnitz, E.; Troyanov, S. I. Inorg. Chem. 2013, 52, 4768. (d) Romanova, N. A.; Fritz, M. A.; Chang, K.; Tamm, N. B.; Goryunkov, A. A.; Sidorov, L. N.; Chen, C.; Yang, S.; Kemnitz, E.; Troyanov, S. I. Chem. - Eur. J. 2013, 19, 11707. (18) (a) Yang, S.; Wei, T.; Kemnitz, E.; Troyanov, S. I. Chem. - Asian J. 2012, 7, 290. (b) Tamm, N. B.; Kosaya, M. P.; Fritz, M. A.; Troyanov, S. I. Nanosyst.: Phys. Chem. Math. 2016, 7, 111.
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b00809. Data on isolation of HPLC fractions with C106 and C108 (PDF) Crytsallographic data (CIF) Crystallographic data (CIF)
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REFERENCES
AUTHOR INFORMATION
Corresponding Authors
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[email protected]. *Fax: +007 495 9391240. Tel.: +007 495 9395396. E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (nos. 21132007, 21371164, and 2151101074), the Deutsche Forschungsgemeinschaft (Ke5743
DOI: 10.1021/acs.inorgchem.6b00809 Inorg. Chem. 2016, 55, 5741−5743
