ARTICLE pubs.acs.org/JPCC
Synthesis, Isolation, Characterization, and Theoretical Studies of Sc3NC@C78-C2 Jingyi Wu,†,‡ Taishan Wang,*,† Yihan Ma,†,‡ Li Jiang,† Chunying Shu,† and Chunru Wang*,† †
Key Laboratory of Molecular Nanostructure and Nanotechnology, Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences (CAS), Beijing 100190, China ‡ Graduate School of CAS, Beijing 100049, China
bS Supporting Information ABSTRACT: Following the first isolation of Sc3NC@C80, a second member of this family of endohedral metallofullerenes, Sc3NC@C78, was prepared by an arc-discharging method. Experimental and theoretical studies demonstrated that the Sc3NC@C78 has a C78-C2 cage with two pairs of adjacent pentagons, which is different from the IPR-satisfying Sc3N@C78-D3h. It was revealed that the size of C78-D3h is appropriate for the Sc3N cluster, but not large enough for encaging the large planar species Sc3NC. Theoretical calculations were preformed on Sc3NC@C78-C2 and Sc3NC@C78-D3h. The results show that Sc3NC would bear a strong depression inside the C78-D3h fullerene cage due to the limited internal space of C78-D3h; on the contrary, C78-C2 has two pairs of adjacent pentagons that induce a large curvature in these sites to form an oblate ellipsoid structure. Thus, it is more favorable to encapsulate the planar species Sc3NC. Ab initio calculations were also performed to further disclose the electronic and electrochemical properties of Sc3NC@C78-C2. It was revealed that the molecule has an electronic structure of (Sc3+)3(NC)3@C786, in which the inner species NC has an unprecedented (NC)3 trianion charging status similar to that in the recently reported Sc3NC@C80-Ih.
’ INTRODUCTION In the past decade, the family of endohedral fullerenes has largely expanded from encaging metal ions to encapsulating various clusters, such as metal carbide,1a,b metal nitride,1c,d metal oxide,1e,f metal sulfide,1g etc., and these cluster endohedral fullerenes have attracted extensive attention due to their novel structures and unique electronic properties.2 In fact, the most recent studies on endohedral fullerenes were focused on cluster endohedral fullerenes, and among them, nearly 80% of the newly isolated molecules were either based on the C80-Ih fullerene cage or with two types of encaged species, that is, metal carbide and metal nitride. Therefore, endohedral fullerenes with both new endohedral species and parent fullerenes other than C80-Ih are highly interesting. C78 is a little smaller than C80, but most of the known C78based endohedral fullerenes are metal nitride endohedral fullerenes with the inner species, including Sc3N, Tm3N, Dy3N, Y3N, Gd3N, etc.3,4 Fascinatingly, even though these metal nitride clusters own very similar structures, they have different C78 parent fullerene cages, in which Sc3N@C78 adopts the IPRsatisfying C78 (D3h: 24 109) isomer, and all others adopt the nonIPR isomer (C2: 22 010, with two pairs of adjacent pentagons (APPs)). Theoretical analyses revealed that, in this case, the size of the endohedral species plays a key role in determining the parent fullerene cages; for example, the round-shaped C78 (D3h: 24 109) isomer is suitable for the small cluster Sc3N but is not large enough to encapsulate the large clusters Tm3N, Dy3N, Y3N, Gd3N, etc. Therefore, the larger clusters would be favored to r 2011 American Chemical Society
select the oblate ellipsoid C78 (C2: 22 010) to fit the planar metal nitride clusters Tm3N, Dy3N, Y3N, and Gd3N. In fact, the appearance of inner clusters templating the parent fullerene cage was also observed for other endohedral fullerenes, for example, Sc3N@C681d,5 and Sc2C2@C68,1b in which the triangular Sc3N cluster and rhombic Sc2C2 cluster template the C68-D3 and C68C2v cages, respectively. On the other hand, a new endohedral fullerene Sc3NC@C80-Ih, which has a planar Sc3NC endohedral cluster, was recently prepared and characterized. This finding inspires us to explore the possibility whether such a Sc3NC quinary cluster can also construct other endohedral fullerenes to form a new endohedral fullerene family, too. Recently, Jin et al.6 predicted the possible structure of Sc3NC@C2n (2n = 68, 78), which provides a valuable clue for us to search for these new metallofullerenes experimentally. Herein, we report the successful preparation and isolation one of the predicted endohedral fullerene Sc3NC@C78-C2, which is well characterized by various spectroscopic techniques, such as MS, UVvis absorption, and Raman spectrometry. Theoretical calculations were also preformed to disclose the electronic structures, ionization energies, electron affinities, and the frontier molecular orbitals of this molecule.
Received: August 25, 2011 Revised: October 21, 2011 Published: October 26, 2011 23755
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Figure 2. UVvis absorption spectra of the purified Sc3NC@78-C2 (red) and Sc3N@C78-D3h (black). The inset shows the enlarged UVvis absorption spectrum of Sc3NC@78-C2. Figure 1. (a) The first stage HPLC profile for the isolation of Sc3NC@C78 in the Buckyprep column (flow rate = 12 mL/min; toluene as eluent). (b) The HPLC profile of purified Sc3NC@C78 (Buckyprep column; flow rate = 6 mL/min; toluene as eluent). The inset shows the positive-ion MALDI-TOF mass spectrum as well as the experimental and calculated isotope distributions of Sc3NC@C78.
’ EXPERIMENTAL SECTION The target molecule was prepared by the Kr€atschmer Huffman arc-discharging method and isolated by high-performance liquid chromatography (HPLC), as we previously reported.1b,7 Graphite rods were core-drilled and subsequently packed with a mixture of Sc/Ni2 alloy and graphite powder in a weight ratio of 2:1. These rods were then vaporized in a Kr€atschmerHuffman generator under a mixed atmosphere of 6 Torr N2 and 194 Torr He. The resulting soot was Soxhlet-extracted with toluene for 12 h to obtain various fullerenes and endofullerenes. The target molecule was isolated by HPLC with two complementary columns, that is, Buckyprep (the first and the third steps) and Buckyprep-M (the second step) columns (see the Supporting Information). ’ THEORETICAL CALCULATION Density functional theory (DFT) calculations were preformed to study the geometric structures, electronic properties, and electrochemical redox potentials of Sc3NC@C78-C2 at the GGA-PBE/ DNP8 level by using the Dmol3 code9 The geometry optimizations were carried out with no symmetry and spin constraints in Cartesian coordinates and with an analytically constructed energy gradient. The Raman spectrum was simulated at the B3LYP10 level with the Gaussian 03 program.11 The standard 6-31G(d) basis set12 for C and the small-core RECP (relativistic effective core potential) plus valence double-ζ basis set (LanL2DZ)13 for Sc were employed, and such a combination of basis sets is denoted as DZP. The geometry of Sc3NC@C78-C2 used in the Raman simulation was reoptimized at the B3LYP/DZP level. ’ RESULTS AND DISCUSSION Sc3NC@C78-containing soot was extracted, and HPLC was performed to isolate this molecule with two complementary columns, that is, Buckyprep and Buckyprep-M columns. In the first step, the Buckyprep column was adopted and the retention time of Sc3NC@C78 was observed between that of Sc3N@ C78-D3h and Sc3N@C80-Ih (Figure 1a). After this fraction was enriched with multiple injections in the same column, in the second step, it was injected to HPLC with a Buckyprep-M column. For the third step, recycling HPLC processes were alternately performed on Buckyprep and Buckyprep-M columns until single peaks on
Figure 3. Experimental Raman spectra of (a) Sc3N@C80-Ih, (b) Sc3NC@ C78-D3h, and (c) Sc3NC@C78-C2, and the simulated Raman spectrum of (d) Sc3NC@C78-C2 at the B3LYP/DZP level.
both columns were reached, as shown in Figure 1b. Moreover, a MALDI-TOF mass spectrum was performed to confirm the high purity of the sample, and the peak at m/z 1097 in the spectrum is accounted for by the composition of Sc3NC79. The Sc3NC79 was further characterized by UVvis spectroscopy. It is well known that metallofullerenes with similar structures and electronic structures would show similar spectral features in their UVvis absorption spectra.1a,14 Figure 2 presents the comparison of UVvis absorption spectra of Sc3NC79 and Sc3N@C78-D3h, which are distinctly different, so the Sc3NC79 would have no similar electronic structure with the known Sc3N@C78-D3h. Alternatively, the feature-less absorption of Sc3NC79 resembles highly that of previously reported Dy3N@C78(II)3 with a C2-symmetric C78 cage; therefore, the Sc3NC79 can be preliminarily assigned as Sc3NC@C78-C2. To further experimentally characterize the geometric structure of this molecule, the Raman spectrometry of Sc3NC@C78-C2 was measured and compared with that of Sc3N@C78-D3h and Sc3NC@C80-Ih, as shown in Figure 3, as well as that of previously reported
[email protected] According to previous studies of endohedral fullerenes with similar structures, the Raman spectrum can be roughly classified to three bands, in which the band ranging from 1200 to 1600 cm1 is mainly attributed to the stretching vibrations of the tangential C78 cage vibrational mode, the weaker band around 700 cm1 is attributed to the flexural vibrations of the fullerene cage, and the low-energy band ranging from 100 to 600 cm1 is mainly attributed to the inner clusters. Obviously, the Raman spectral features of Sc3NC@C78-C2 in the low-energy range are similar to those of Sc3NC@C80-Ih, suggesting the internal cluster Sc3NC, and the high-energy bands are essentially similar to those of previously reported Dy3N@C78,3 indicating 23756
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Table 1. Selected AtomAtom Distances (Å), Angles, and Dihedral Angles for the Sc3NC and Sc3N Moieties in C78-C2 and C78-D3ha parameters
Figure 4. GGA-PBE/DNP-optimized structures of Sc3NC@C78-C2, Sc3NC@C78-D3h, Sc3N@C78-D3h, and Sc3N@C78-C2. Relative energies (RE, kcal/mol), HOMOLUMO gaps (Eg, eV), and their two-dimensional lengths (Å) of outer cages.
the fullerene cage C78-C2. Therefore, the Raman study strongly supports the structure of the above-proposed Sc3NC@C78-C2. With the experimental structure of Sc3NC@C78-C2, we now may make a detailed study on the geometric and electronic structural properties of this molecule via ab initio calculations. Because, until now, the parent fullerene cages for C78-based endohedral fullerenes are either C78(D3h: 24 109) or C78(C2: 22 010), we chose the two C78 isomers as parent cages to make a comparative study. The structure of the encaged species Sc3NC was assumed to take the planar structure as characterized in Sc3NC@C80-Ih,15 where the N atom is located at the center of the cluster. As shown in Figure 4, the geometries of Sc3NC@C78-C2 and Sc3NC@C78-D3h were optimized and compared with that of the reported Sc3N@C78-D3h. For comparison, the Sc3N@C78-C2 was also taken into account. Some key geometric parameters are listed in Table 1. In Sc3N@C78-D3h, it was shown that the C78 cage was slightly deformed, and the Sc3N cluster nearly maintains its original structure (see Figure S2, Supporting Information). The three scandium atoms show an equilateral triangle structure with a ScSc distance at 3.48 Å, and the nearest Sccage distance, 2.25 Å, is close to the ScC bond length in solid scandium carbides.16,17 Therefore, all the geometric parameters are in a reasonable range. Besides, the Sc3N@C78-D3h is 18.41 kcal/mol more stable than Sc3N@C78-C2 in calculated relative energy. On the basis of the optimized geometries and energies of them, it was revealed that the inner space of C78-D3h is appropriate for encapsulating the Sc3N cluster. However, the optimized structure of Sc3NC@C78-D3h shows that the C78-D3h in this case bears a serious deformation where the size of the fullerene cage along the Sc2Sc3 direction changes from 7.76 to 8.05 Å (see Figure S2, Supporting Information), and the nearest Sccage distance was depressed to only 2.17 Å, which is even smaller than the covalence bond of ScC, 2.21 Å. Therefore, the structure of Sc3NC@C78-D3h is obviously unfavorable. Finally, the C78-C2 isomer has two APP sites in the fullerene cage, which induces a large curvature on these sites and forms an oblate ellipsoid structure of this fullerene, which makes it more appropriate to encapsulate the rigid planar Sc3NC. It was shown that, for the optimized structure of Sc3NC@C78-C2, the Sccage distance becomes 2.25 Å, suggesting that no serious depression was put on the Sc3NC cluster. It was further revealed that the big inner space of C78-C2 is apt to encapsulate the large inner cluster Sc3NC. The rationality of a molecular structure can also be judged from its relative energies. For Sc3NC@C78-D3h, due to the large deformation of the fullerene cage and the strong depression of Sc3NC, the calculated total energy of this structure is 4.44 kcal/mol higher than that of Sc3NC@C78-C2, indicating the less stability of this structure comparing with the non-IPR Sc3NC@C78-C2. Besides,
Sc3NC@
Sc3NC@
Sc3N@
Sc3N@
C78-C2
C78-D3h
C78-D3h
C78-C2 2.35
Sc1cage
2.28
2.18
2.25
Sc2cage
2.24
2.17
2.25
2.34
Sc1Sc2
3.89
3.46
3.48
3.58
Sc2Sc3 Sc1N
4.26 2.01
4.01 2.04
3.48 2.01
3.57 2.02
Sc2N
2.47
2.15
2.01
2.10
Sc2C
2.13
2.07
CN
1.25
1.29
Sc1NSc2
120.4
111.4
Sc2CSc3
180.0
151.8
Sc2NCSc3
180.0
180.0
120.0
120.7
180.0b
178.3b
a
In all the four endohedral fullerenes, the atom Sc3 and atom Sc2 are equivalent due to molecule symmetry. b Dihedral angles Sc2N Sc1Sc3 for Sc3N@C78-D3h and Sc3N@C78-C2.
the HOMOLUMO gaps of Sc3NC@C78-D3h and Sc3NC@ C78-C2 are 0.84 and 1.00 eV, respectively, reflecting also the less stability of Sc3NC@C78-D3h to Sc3NC@C78-C2. On the basis of the optimized structure of Sc3NC@C78-C2, the Raman spectrometry was simulated, as shown in Figure 3d, which agrees well with the experimental result in Figure 3c. With the theoretical simulation combining a comparative study between Sc3NC@C80-Ih and Sc3NC@C78-C2, it is very helpful to assign vibration modes in the spectrum of this molecule. For example, in the Raman spectrum of Sc3NC@C78-C2, there are a group of lines at around 470 cm1 that would be assigned as the N-dominated δ (ScNCSc) bending modes and vs (ScNC) stretching mode; similar features can be found at 468 cm1 in
[email protected] Moreover, the intense signals at ca. 232 cm1 were assigned to the CNC-dominated δ (ScNCSc) bending modes and in-plane Sc3NC deformation, corresponding to that of Sc3NC@C80-Ih at 223 cm1. However, obvious differences were also observed in the Raman spectra of Sc3NC@C80-Ih and Sc3NC@C78-C2 due to their different parent fullerene cages. For example, Sc3NC was bonded to the APP sites of C78-C2 but it rotates freely inside the C80-Ih. Therefore, in their Raman spectra, the vs (ScNC) stretching mode in Sc3NC@C80-Ih shows a strong and sharp signal at 410 cm1, but correspondingly, the relevant 404 cm1 peaks in Sc3NC@C78-C2 are somewhat weak and diffused due to the interaction from the C78 fullerene cage. Especially, a strong signal at 168 cm1 in the spectrum of Sc3NC@C78-C2 was ascribed to the A-symmetric frustrated translation (Tx) along the C2 axis of the molecule, which is absent for Sc3NC@C80-Ih and Sc3N@C78-D3h. In fact, this signal was also observed in Dy3N@C78-C2 as Tx at 166 cm1,3 so the signal around this position can be appointed to the fingerprint vibration for the metallofullerenes with the C78-C2 cage. The electronic properties of endohedral fullerenes are also highly interesting. Detailed analyses of its KohnSham molecular orbitals revealed that this molecule has a formal electronic structure of (Sc 3+ )3 (NC)3@C 78 6 (see the Supporting Information). As shown in Figure 5, its HOMO-1 is mainly attributed to the C78 cage and the HOMO is mainly attributed to the Sc3NC cluster, whereas the two lowest unoccupied 23757
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Table 2. Spin Multiplicities (S) and Redox Potentials (E0, V) for [Sc3NC@78-C2]q (q = 0, (1, 2) in o-DCB Solvent as Well as the Optimal NC Bond Length (RNC, Å) and Derived Formal Charge (QNC) for the Encapsulated NC Moiety Figure 5. Isodensity surfaces for the frontier molecular orbitals (isodensity value of 0.02) of Sc3NC@C78-C2 (eigenvalue of orbital, eV).
Figure 6. GGA-PBE/DNP-optimized structures of (a) Sc3NC@C78-C2 and (b) the inner Sc3NC cluster. The numbers represent the calculated shortest distances between Sc and the carbon cage, some key bond lengths (Å), and key bond angles and dihedral angles (°) in neutral, cationic (in parentheses), and anionic (in square brackets) of Sc3NC@C78-C2, respectively. The carbon atoms in two pairs of adjacent pentagons are denoted by the yellow color. Green balls represent the Sc atoms, pink balls and blue balls represent the carbon and nitride atoms in Sc3NC, and gray balls represent the normal carbon atoms in the C78-C2 cage.
molecular orbitals (LUMO and LUMO+1) can be attributed to the carbon cage orbitals with a minor contribution from the 3d orbitals of the top Sc3+ ions. To have a better understanding of the electronic property of Sc3NC@C78-C2, we made a detailed study on the monocation and monoanion. Structural optimizations were performed on the monocation and monoanion of Sc3NC@C78-C2 and compared with the neutral molecule. Accordingly, the ionization potential and electron affinity predicted for Sc3NC@C78-C2 at the GGAPBE/DNP level are 6.70 and 3.00 eV, respectively, suggesting that this endofullerene has good electron-accepting capacity and is rather stable against oxidation. As shown in Figure 6, Sc3NC@C78-C2 almost maintains its neutral structure after capturing an electron, but when it loses an electron, the structure of the Sc3NC cluster is seriously changed, in which the CN bond length is even shorten from 1.25 to 1.22 Å, suggesting that its first reduction state is predominantly related to the carbon cage, and its first oxidation state occurs on the inner Sc3NC cluster. To derive theoretically the electrochemical redox potentials, we computed the geometries and total energies of [Sc3NC@ C78-C2]q (q = 0, ( 1, 2) in 1,2-dichlorobenzene (o-DCB) solvent at the GGA-PBE/DNP theoretical level by using the conductorlike screening model (COSMO).18,19 For a given electrochemical reaction in the solvent, for example, aq f a(q+1) + e, the computed redox potential E0 is defined by the equation E0 ¼ ΔG 4:98
ð1Þ
in which ΔG (the free energy change of the reaction) is approximated by the total electronic energy change ΔEq ¼ Eðaq þ 1 Þ Eðaq Þ
ð2Þ
of the reaction, and 4.98 (unit = eV) is the free energy change associated with the reference ferrocene/ferrocenium (Fc/Fc+) redox couple.20
Q
+1
0
1
S
2
1
2
2 1
RNC
1.22
1.25
1.25
1.24
QNC
2
3
3
3
E0
0.57
1.05
1.81
Figure 7. Isodensity surfaces for the [Sc3NC@C78-C2]q (q = 0, ( 1, 2) in o-DCB solvent. For an open-shell isomer, SOMO refers to the highest occupied α-spinorbital; SUMO refers to the lowest unoccupied β-spinorbital.
As shown in Table 2, the COSMO-PBE/DNP calculations predicted one oxidation potential at +0.57 V as well as two reduction potentials at 1.05 and 1.81 V in o-DCB. To further calibrate the electronic properties of Sc3NC@C78-C2, isodensity surfaces for the frontier molecular orbitals of them at various valence states (q = 0, ( 1, 2) were investigated at the same level of calculations (see Figure 7). As a result, the two reduction states are predominantly related to adding electrons to the carbon cage, and the oxidation corresponds to deriving an electron from the encapsulated Sc3NC, or more precisely, from the CN group.
’ CONCLUSIONS The finding of Sc3NC@C80-Ih represents a new type of cluster endohedral fullerene, which may lead to a new family of such fullerenes with the novel encapsulated species Sc3NC, so, since our first report of this molecule in last year, it has attracted extensive attention to explore the possibility of other Sc3NC@C2n members. In this paper, we report the isolation, characterizations, and detailed theoretical studies of the second example of Sc3NC encapsulated fullerenes, that is, Sc3NC@C78-C2, which was predicted as a stable structure by Jin et al. recently. Various spectroscopic characterizations unambiguously revealed the non-IPR structure of Sc3NC@C78-C2, and detailed theoretical calculations indicated that the internal space of C78-D3h is not big enough for the Sc3NC, so, alternatively, the endohedral fullerene adopts the C78-C2 cage. On the basis of the optimized Sc3NC@ C78-C2 structure, the electronic and redox electrochemical properties of this molecule were also calculated. ’ ASSOCIATED CONTENT
bS
Supporting Information. Detailed data for HPLC, optimized structures of C786 cages, and coordinates of the optimized endohedral complexes. This material is available free of charge via the Internet at http://pubs.acs.org.
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’ AUTHOR INFORMATION Corresponding Author
*E-mail:
[email protected] (T.W.),
[email protected] (C.W.).
’ ACKNOWLEDGMENT We thank the National Nature Science Foundation of China (20821003, 20702053, and 20903107), the Ministry of Science and Technology (2008ZX05013-004), and the China Postdoctoral Science Foundation (20100480027). T.W. also gratefully acknowledges the support of the K. C.Wong Education Foundation, Hong Kong. ’ REFERENCES (1) (a) Dunsch, L.; Yang, S. F. Phys. Chem. Chem. Phys. 2007, 9, 3067. (b) Shi, Z. Q.; Wu, X.; Wang, C. R.; Lu, X.; Shinohara, H. Angew. Chem., Int. Ed. 2006, 45, 2107. (c) Shinohara, H. Rep. Prog. Phys. 2000, 63, 843. (d) Chaur, M. N.; Melin, F.; Ortiz, A. L.; Echegoyen, L. Angew. Chem., Int. Ed. 2009, 48, 7514. (e) Stevenson, S.; Fowler, P. W.; Heine, T.; Duchamp, J. C.; Rice, G.; Glass, T.; Harich, K.; Hajdu, E.; Bible, R.; Dorn, H. C. Nature 2000, 408, 427. (f) Yamada, M.; Akasaka, T.; Nagase, S. Acc. Chem. Res. 2010, 43, 92. (g) Dunsch, L.; Yang, S. F.; Zhang, L.; Svitova, A.; Oswald, S.; Popov, A. A. J. Am. Chem. Soc. 2010, 132, 5413. (2) (a) Stevenson, S.; Rice, G.; Glass, T.; Harich, K.; Cromer, F.; Jordan, M. R.; Craft, J.; Hadju, E.; Bible, R.; Olmstead, M. M.; Maitra, K.; Fisher, A. J.; Balch, A. L.; Dorn, H. C. Nature 1999, 401, 55. (b) Wang, C. R.; Kai, T.; Tomiyama, T.; Yoshida, T.; Kobayashi, Y.; Nishibori, E.; Takata, M.; Sakata, M.; Shinohara, H. Angew. Chem., Int. Ed. 2001, 40, 397. (c) Stevenson, S.; Mackey, M. A.; Stuart, M. A.; Phillips, J. P.; Easterling, M. L.; Chancellor, C. J.; Olmstead, M. M.; Balch, A. L. J. Am. Chem. Soc. 2008, 130, 11844. (d) Mercado, B. Q.; Olmstead, M. M.; Beavers, C. M.; Easterling, M. L.; Stevenson, S.; Mackey, M. A.; Coumbe, C. E.; Phillips, J. D.; Phillips, J. P.; Poblet, J. M.; Balch, A. L. Chem. Commun. 2010, 46, 279. (3) Popov, A. A.; Krause, M.; Yang, S. F.; Wong, J.; Dunsch, L. J. Phys. Chem. B 2007, 111, 3363. (4) Beavers, C. M.; Chaur, M. N.; Olmstead, M. M.; Echegoyen, L.; Balch, A. L. J. Am. Chem. Soc. 2009, 131, 11519. (5) Olmstead, M. M.; Lee, H. M.; Duchamp, J. C.; Stevenson, S.; Marciu, D.; Dorn, H. C.; Balch, A. L. Angew. Chem., Int. Ed. 2003, 42, 900. (6) Jin, P.; Zhou, Z.; Hao, C.; Gao, Z. X.; Tan, K.; Lu, X.; Chen, Z. F. Phys. Chem. Chem. Phys. 2010, 12, 12442. (7) Wang, T. S.; Wu, J. Y.; Xu, W.; Xiang, J. F.; Lu, X.; Li, B.; Jiang, L.; Shu, C. Y.; Wang, C. R. Angew. Chem., Int. Ed. 2010, 49, 1786. (8) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. Rev. Lett. 1996, 77, 3865. (9) (a) Delley, B. J. Chem. Phys. 1990, 92, 508. (b) Delley, B. J. Chem. Phys. 2000, 113, 7756 DMol3 is available as part of Material Studio and Cerius2 by Accelrys Inc. (10) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (b) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785. (11) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A.; Vreven, J. T.; Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J.; Ortiz, B. J. V.; Cui, Q.; Baboul, A. G.;
ARTICLE
Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian03, revision E01; Gaussian, Inc.: Wallingford, CT, 2004. (12) Hehre, W. J.; Ditchfield, R.; Pople, J. A. J. Chem. Phys. 1972, 56, 2257. (13) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 299. (14) Dunsch, L.; Yang, S. Small 2007, 3, 1298. (15) Wang, T. S.; Feng, L.; Wu, J. Y.; Xu, W.; Xiang, J. F.; Tan, K.; Ma, Y. H.; Zheng, J. P.; Jiang, L.; Lu, X.; Shu, C. Y.; Wang, C. R. J. Am. Chem. Soc. 2010, 132, 16362. (16) Cotton, F. A.; Wilkinson, G. C.; Murillo, A.; Bochmann, M. Advanced Inorganic Chemistry, 6th ed.; Wiley-Interscience: New York, 1999; p 221. (17) Dean, J. A. Lange’s Handbook of Chemistry; McGraw-Hill Inc.: New York, 1999; p 15. (18) Klamt, A.; Schuurmann, G. J. Chem. Soc., Perkin Trans. 2 1993, 799. (19) Klamt, A.; Jonas, V.; Burger, T.; Lohrenz, J. J. Phys. Chem. 1998, 102, 5074. (20) Ryan, M. F.; Eyler, J. R.; Richardson, D. E. J. Am. Chem. Soc. 1992, 114, 8611.
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