ARTICLE pubs.acs.org/JPCC
Structural, Electronic, and Magnetic Properties of Neutral and Charged Transition MetalBis(dicarbollide) Sandwich Clusters Tingting Zhang, Liyan Zhu, Zhi Tian, and Jinlan Wang* Department of Physics, Southeast University, Nanjing, 211189, People's Republic of China
bS Supporting Information ABSTRACT: Structural, electronic, and magnetic properties of transition metal (TM)bis(dicarbollide) (TM(Dcb)2; TM = ScMn, Dcb = dicarbollide) sandwich clusters and their charged counterparts (TM(Dcb)2+, TM(Dcb)2) are systematically investigated by using all electron density functional theory approach. All TM(Dcb)2 sandwich clusters are highly stable because of the formation of ioniccovalent bonding. The Ti(Dcb)2 is the most stable, the Sc- and V(Dcb)2 are intermediate, and the Cr- and Mn(Dcb)2 are the least stable. The magnetic moment of TM(Dcb)2 exhibits a clear element-dependent variation with 1 μB for Sc(Dcb)2 and 0 μB for Ti(Dcb)2 and with a linear increased trend by 1 μB from Ti(Dcb)2 to Mn(Dcb)2. This element-dependent magnetic behavior can be well understood by electron transfer as well as spin density distribution. We further reveal that charging can induce the rotation of the ligands in the Sc-, V-, Cr-, and Mn(Dcb)2 clusters, which makes them promising candidates for molecular motors.
I. INTRODUCTION Organometallic sandwich clusters comprised of transition metals (TMs) and organic molecules have attracted great attention in the past five decades since ferrocene, FeCp2 (Cp = C5H5), was first discovered.1,2 Afterward, quite a few sandwich clusters were experimentally synthesized including transition metal benzene,3 cationic alkali metalbenzene4 and lanthanide cyclooctatetraene5,6 sandwich clusters, on which many experimental511 and theoretical1224 studies have been performed. Besides, some all-metal clusters analogous to the structure of organometallic sandwich cluster have been computationally predicted to be stable aromatic complexes.25 Vanadium benzene sandwich compound is the most extensively studied one, whose magnetic moment linearly increases with increases of cluster size9,14,22 and its infinite wire is a (quasi) half-metallic ferromagnet.15,26 Furthermore, bimetallic organic sandwich clusters TMn(FeCp2)n+1 (TM = Ti, V, n = 13) were synthesized experimentally27 and were computationally predicted to be ferromagnetic with linearly increased magnetic moment; their infinite wires also showed interesting electronic and magnetic properties and followed an empirical electron filling rule.18,2832 Besides the extensively studied metalflat homocyclic ligand sandwich clusters, efforts have also been made on cage ligand-like sandwich clusters, such as metalfullerene sandwich clusters.21,3335 Dicarbollide (1,2-C2B9H11, abbreviated as Dcb hereafter), one of the most widely studied carboranes,36 might be another prominent cage ligand and could form sandwich clusters such as iron bis(dicarbollide),37 an analogue of ferrocene, because Dcb shows similar or even greater electron acceptor property than the Cp ligand.38,39 In fact, the ferrocene-like TM-Dcb (TM(Dcb)2, TM = Fe,40 Co,37,4143 Ni,37,44,45 Cu4648) sandwich clusters r 2011 American Chemical Society
have been successfully synthesized and characterized experimentally. Theoretically, B€uhl et al.4951 studied the structures and 11B NMR chemical shifts of TM(Dcb)2 (TM = Fe, Co, Ni, Ru, Rh, Pd). They found that transoid configurations were energetically preferred for TM = Fe, Co, Ru, and Rh, while cisoid conformations were slightly more stable for TM = Ni and Pd. More interestingly, the ligands of Ni(Dcb)2 can be easily rotated by a simple electron transfer, making it a potential candidate for a molecular motor.45 Structural transition from a transoid configuration [3-Fe-(1,2-C2B9H11)2]2- to a protonated cisoid configuration [3-Fe-(1,2-C2B9H11)2H] was also observed computationally.51 Moreover, Singh et al.52 found that metallacarboranes, especially the Sc and Ti compounds, showed high hydrogen storage capacity. By virtue of the high stability, inorganic nature, good solubility properties, and tailorability,53 metallacarborane sandwich clusters have showed broad applications in catalysis,5456 nuclear waste recuperation,57 boron neutron capture therapy,5860 human immunodeficiency virus protease inhibition,61 dyesensitized solar cell shuttle material,62 nanodevices,45 and so on. The aforementioned studies, however, were largely focused on the late 3d TM(Dcb)2 (TM = Fe, Co, Ni, and Cu) sandwich clusters. So far, there is little exploration on early 3d TM sandwich clusters.52 In this study, we systematically investigated the structure, stability, electronic, and magnetic properties of TM(Dcb)2 (TM = ScMn) sandwich clusters and their charged counterparts (TM(Dcb)2+, TM(Dcb)2). Our calculations showed that these clusters have higher or similar stability Received: March 17, 2011 Revised: June 26, 2011 Published: June 28, 2011 14542
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compared to the synthesized Co(Dcb)2 cluster. Besides, the magnetic moments of TM(Dcb)2 sandwich clusters exhibit an interesting element-dependent behavior. Charging on the Sc-, V-, Cr-, and Mn(Dcb)2 clusters can induce rotating of the ligands, which indicates these clusters might serve as molecular motors like the Ni(Dcb)2 cluster.45
II. COMPUTATIONAL METHOD All calculations were carried out within the framework of density functional theory (DFT) as implemented in the DMol3 package.63,64 We employed the general gradient approximation parametrized by PerdewBurkeErnzerhof (PBE)65 and all electron double numerical basis sets with polarization functions (DNP). Geometries were fully relaxed through the Broyden FletcherGoldfarbShanno algorithm without any symmetry constraint. The convergence criterions are 105, 103, 103 au for the total energy, gradient, and displacement, respectively. Different spin multiplicities were considered for each configuration. Besides, vibrational frequency calculations were carried out
Figure 1. Schematics of transoid (a) and cisoid (b) configurations of TM(Dcb)2 (TM = ScMn) sandwich clusters. Green, gray, pink, and white balls represent TM, carbon, boron, and hydrogen atoms, respectively.
to verify the obtained lowest-energy geometries to be true local minima. To evaluate the reliability of the method described above, we compared the optimized geometrical parameters of Co(Dcb)2 with other theoretical49,50 and experimental66,43 results. With the same definitions of dihedral angle θ and bond lengths for the ground state of Co(Dcb)2 in ref 50, the dihedral angle θ is 179.4° and the bond lengths of MC1, MC2, MB4, MB7, MB8, C1C2, C1B4, C2B7, B4B8, and B7B8 are 2.08, 2.08, 2.14, 2.13, 2.16, 1.61, 1.71, 1.72, 1.80, and 1.80 Å in our calculation, respectively. These results are in very good agreement with the previous theoretical values of 180.0°, 2.03, 2.03, 2.11, 2.11, 2.16, 1.64, 1.72, 1.72, 1.79, and 1.79 Å, respectively,49,50 and the experimental values of 180.0°, 2.02, 2.02, 2.11, 2.08, 2.14, 1.63, 1.71, 1.72, 1.79, and 1.78 Å, respectively,66 and 180.0°, 2.14, 2.10, 2.13, 2.12, 2.18, 1.57, 1.71, 1.71, 1.77, and 1.77 Å, respectively.43 Therefore, the method chosen in this work is workable for the TM(Dcb)2 sandwich clusters.
III. RESULTS AND DISCUSSION We considered two kinds of geometries for each cluster considering the relative positions of two Dcb ligands, namely, transoid and cisoid configurations, as shown in Figure 1. The optimized lowest energy structures of both configurations of TM(Dcb)2 are presented in Figure S1 in the Supporting Information. The structural, energetic, and magnetic properties of the lowest energy transoid and cisoid configurations for each sandwich cluster are summarized in Table 1, and their corresponding different spin states (low-lying states) are presented in Table S1 in the Supporting Information. The distances between two C atoms in Dcb are elongated by ∼9% when Dcb interacts with TM to form TM(Dcb)2 clusters but other bond lengths in Dcb ligands are nearly unchanged (see Table S2 in the Supporting Information, numbering of each atom is shown in Figure 1). The Sc- and Mn(Dcb)2 clusters energetically favor transoid configurations while the ground states of Ti-, V-, and Cr(Dcb)2 clusters adopt cisoid ones. With the decrease of the atomic diameter from Sc to Mn, the distances between metal and the centrals of ligands also decrease from Sc(Dcb)2 to Mn(Dcb)2. The different ground state structures of TM(Dcb)2 can be well understood from the characteristics of their occupied frontier
Table 1. Structural, Energetic, and Magnetic Properties of TM(Dcb)2 Sandwich Clustersa system
configuration
ΔE
M
μTM
μLigand
BE
Δ
RTMCen
q
Sc(Dcb)2
T
0.00
2
0.05
0.48/0.47
7.67
0.37
1.96/1.96
1.50
C
0.11
2
0.09
0.45/0.46
7.56
0.35
1.98/1.98
C
0.00
1
0.00
0.00/0.00
8.32
1.96
1.81/1.81
T
0.14
1
0.00
0.00/0.00
8.18
1.83
1.81/1.81
C
0.00
2
0.97
0.04/-0.002
7.50
1.40
1.76/1.74
T
0.13
2
0.96
0.05/-0.005
7.37
1.35
1.76/1.74
Cr(Dcb)2
C T
0.00 0.51
3 3
1.99 1.91
0.06/-0.04 0.05/0.04
5.30 4.79
1.46 0.29
1.68/1.72 1.66/1.66
1.00
Mn(Dcb)2
T
0.00
4
2.77
0.11/0.11
5.54
1.42
1.64/1.64
1.27
C
0.04
4
2.76
0.12/0.12
5.50
1.63
1.65/1.65
Ti(Dcb)2 V(Dcb)2
1.29 1.12
a Configurations (T and C stand for transoid and cisoid configurations, respectively), relative energy between two different configurations ΔE (eV), spin multiplicity M, magnetic moment on metal μTM (μB), magnetic moment on two ligands μLigand (μB), binding energy BE (eV), HOMOLUMO gap Δ (eV), distances between transition metal and two centrals of ligands RTM-Cen (Å), and charges on TM in the lowest-energy structures from natural population analysis (NPA) q (e) of the TM(Dcb)2 (TM = ScMn) sandwich clusters.
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Figure 3. Total magnetic moments of the ground states of TM(Dcb)2 (TM = ScMn) clusters. The corresponding spin density of each cluster is also present by the side of the magnetic moment.
Figure 2. Occupied frontier orbitals for lowest energy cisoid (a) and transoid (b) configurations of Cr(Dcb)2 cluster and occupied frontier orbitals for the ground states of Ti(Dcb)2 (c), V(Dcb)2 (d), and Mn(Dcb)2 (e) clusters, The R or β in parentheses represents the major and minor spin orbitals, respectively.
orbitals. As a representative example, the occupied frontier orbitals of the cisoid and transoid configurations of Cr(Dcb)2 are plotted in panels a and b of Figure 2. Obviously, the cisoid configuration has more bonding orbitals than the transoid one, which stabilizes the structure. To assess the stability of TM(Dcb)2 sandwich clusters, we calculated the binding energies (BEs) using the following definition BEðTMðDcbÞ2 Þ ¼ E½TM þ 2E½Dcb E½TMðDcbÞ2
ð1Þ
where E[ 3 ] represents the total energy of an isolated TM atom in ground state, a relaxed Dcb ligand, and a relaxed TM(Dcb)2 cluster, respectively. As listed in Table 1, all the BEs of the ground states are greater than 5.0 eV. For comparison, we also calculated the BE of Co(Dcb)2, an already synthesized cluster.37,41 The ground state of Co(Dcb)2 has a BE of around
5.69 eV using the same definition above. Hence, the Sc-, Ti-, and V(Dcb)2 are more stable than Co(Dcb)2 from the point view of BE; whereas the Cr- and Mn(Dcb)2 have the comparable stability to Co(Dcb)2. So it indicates that TM(Dcb)2 clusters are of high stability against decomposing into constituent fragments. Natural population analysis (NPA) shown in Table 1 (the detailed analysis of NPA is shown in Table S3 in the Supporting Information) reveals significant electron transfer from TM atoms to Dcb ligands, suggesting remarkably ionic interaction between TM atoms and Dcb ligands. On the other hand, frontier orbital analysis (see Figure 2) demonstrates that clear covalent bonding forms between TM and Dcb ligands. According to the Wade rule,67 each Dcb ligand tends to gain two extra electrons from metal atom to form a stable six electron structure, forming Dcb2 and TM4+. Meanwhile, when Dcb2 ligands interact with TM4+ cation, about two electrons backdonate from ligands to the TM4+ forming bonding orbitals. Taking Ti(Dcb)2 as an example, four valence electrons first transfer from Ti to two Dcb ligands, leading to the totally empty 3d orbitals of Ti4+. Then about two electrons back-donate from Dcb2 to the empty 3d orbitals of Ti4+ leading to the formation of four bonding orbitals (see HOMO, HOMO-1, HOMO-2, and HOMO-3 of Ti(Dcb)2 in Figure 2c and Figure S2 in the Supporting Information). Therefore, the coexistence of the ionic and covalent bonding between TMs and Dcb ligands is responsible for the high stability of TM(Dcb)2 (TM = ScMn) clusters. Moreover, a clear trend for the BEs of TM(Dcb)2 clusters is observed: the Ti(Dcb)2 cluster has the largest stability with BE larger than 8.0 eV, while the stabilities of Sc- and V(Dcb)2 clusters are intermediate; and the Cr- and Mn(Dcb)2 are the least ones, whose BEs are smaller than 6.0 eV. To deeply understand the interesting element-dependent stability, we examined the frontier orbitals of TM(Dcb)2 sandwich clusters and presented those of Ti(Dcb)2, V(Dcb)2, and Mn(Dcb)2 in panels c, d, and e of Figure 2, respectively. Apparently, the orbitals of Ti(Dcb)2 from the highest occupied molecular orbital (HOMO) to HOMO-3 are all bonding orbitals between TM and Dcb ligands, which accounts for the highest stability of Ti(Dcb)2. As for Mn(Dcb)2, the orbitals from HOMO to HOMO-3 are all nonbonding orbitals and the HOMO-4 antibonding orbital weakens the stability of the cluster remarkably. For V(Dcb)2 in Figure 2d, the number of bonding orbitals is between those of Ti(Dcb)2 and 14544
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Figure 4. (a) Charging induced rotation of the ligands in TM(Dcb)2 (TM = Sc, V, Cr, Mn) sandwich clusters. (b) Potential energy surfaces of Mn(Dcb)2 and Mn(Dcb)2+ with respect to the rotational angle. (c) Occupied frontier energy levels in the T and C configurations for TM(Dcb)2 (TM = Sc, V, Cr, Mn) sandwich clusters. The upward and downward arrows represent spin up and spin down electrons, respectively.
Mn(Dcb)2 clusters; hence, the BE of V(Dcb)2 is intermediate. While the intermediate stability of Sc(Dcb)2 roots in insufficient electrons transferring from Sc to ligands, the valence electronic configuration of Sc atom is 3d14s2 which could not supply enough electrons to the two Dcb ligands. The total magnetic moments of the TM(Dcb)2 clusters in the ground states are presented in Figure 3. The magnetic moments decrease from 1 μB of Sc(Dcb)2 to zero spin of Ti(Dcb)2 and then linearly increase from Ti(Dcb)2 to Mn(Dcb)2 with the increment of 1 μB. Such an interesting element-dependent magnetic variation can be thoroughly understood from electron donation and back-donation as well as spin density distribution. As mentioned above, four valence electrons transfer from TM to Dcb ligands and about two electrons back-donate from two Dcb2- ligands to TM4+ when Dcb2- ligands interact with TM4+ cation. Further analysis reveals that these two back-donation electrons equally occupy the R and β orbitals of TM atoms and have no contribution to the magnetic moment of TM(Dcb)2 clusters (see Table S3 in the Supporting Information). Therefore, the magnetism is actually determined by the donation process, that is, the charge transfer from TM to Dcb. For Ti-, V-, Cr-, Mn(Dcb)2, the electronic configurations of Ti, V, Cr, and Mn atoms are 3d24s2, 3d34s2, 3d54s1, and 3d54s2, respectively, the net valence electrons are 0, 1, 2, and 3 after four electrons transfer to two Dcb ligands; thus, their magnetic moments 0, 1, 2, and 3 μB, respectively. Spin densities of V-, Cr-, and Mn(Dcb)2 clusters are highly localized around TM atoms as shown in Figure 3, consistent with the above analysis. As for Sc(Dcb)2, the Sc atom could only supply three electrons to two Dcb ligands, leading to one unpaired electron in the Dcb ligands. Therefore, the magnetism of Sc(Dcb)2 is largely contributed by the Dcb ligands, which is perfectly reflected from the spin density of Sc(Dcb)2 distributed only on the two Dcb ligands as shown in the inset of Figure 3.
Bearing in mind that previous study revealed that cisoid and transoid structures of Ni(Dcb)2 could be switched through a simple electron transfer,45 which might be a good candidate for a molecular motor, both the positive and negative charged sandwich clusters, TM(Dcb)2+ and TM(Dcb)2, were also investigated here to address whether charging will induce the structure transition in these TM(Dcb)2. The optimized lowest energy cisoid and transoid configurations of the charged TM(Dcb)2+ and TM(Dcb)2 clusters are displayed in Figure 4a and Figure S3 in the Supporting Information. The total magnetic moment, HOMOLUMO gap and relative energy between transoid (T) and cisoid (C) configuration of lowest-energy structures for cationic and anionic clusters as well as their neutral ones are also listed in Table S4 in the Supporting Information. As clearly seen from Table S4 and Figure S3 in the Supporting Information, the ground states of V- and Cr(Dcb)2 clusters adopt T configuration, while their cationic clusters energetically favor the same configuration as the neutral cluster, namely, C configuration. C and T configurations are favorable for the anionic and cationic Sc(Dcb)2 clusters, respectively. For the case of Ti(Dcb)2, both its anion and cation prefer C configurations, which is exactly the same as the neutral cluster. Nevertheless, the anionic Mn(Dcb)2 cluster favors a T configuration, while the Mn(Dcb)2+ cation forms C configuration. These results indicate that addition of one electron on the neutral TM(Dcb)2 (TM = Sc, V, and Cr) clusters induces the rotation of the Dcb ligands and turns the structural transition from the T (or C) to C (or T) configuration, while the removal of an electron in Mn(Dcb)2 leads to the structure transition from the T to the C configuration. So these early TM(Dcb)2 sandwich clusters might also be good candidates for molecular motor, which enriches us more flexibility in designing TM(Dcb)2 based molecular motors. Nevertheless, to be an ideal molecular motor, the rotational barrier between the two configurations is another critical factor.45,68 Therefore, the 14545
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The Journal of Physical Chemistry C potential energy surfaces (PES) of TM(Dcb)2 with respect to the rotational angle are explored. Taking Mn(Dcb)2 and Mn(Dcb)2+ as an example, whose PES are shown in Figure 4b, the ground state of Mn(Dcb)2 (T configuration) is defined as 0°. One Dcb ligand in C configuration is rotated by ∼140° compared to the one in T configuration. The rotational barriers from T to C and from C to T are both about 0.2 eV for Mn(Dcb)2+ and Mn(Dcb)2, respectively. Hence, the small rotational barrier makes the TM(Dcb)2 clusters promising molecular motors. Besides, because the Dcb is a good electron acceptor and the metal atom has a low ionization energy (normally, the IEs of these metal atoms are about 1.5 eV lower than that of Dcb), the ionized electron should be removed from TM atoms instead of the Dcb ligand, while the addition of an extra electron is prone to go into the Dcb ligand. The rotation of ligands induced by the electron transfer can be well understood from the eigen energies of the HOMO and LUMO in the neutral TM(Dcb)2 clusters. Figure 4c gives the energy levels of T and C configurations for TM(Dcb)2 (TM = Sc, V, Cr, Mn). Taking Sc(Dcb)2 as an example, the eigen energy of LUMO in C configuration is lower than that in the T configuration. Hence, when an electron is added to the Sc(Dcb)2 cluster, it would prefer to occupy the LUMO of C configuration, so the anionic Sc(Dcb)2 cluster energetically adopts a C configuration rather than a T configuration. Moreover, because the eigen energy of HOMO in T configuration is higher than that in the C configuration, the electron of the T configuration is easier to remove, so the cationic cluster retains same geometry as the neutral cluster. Similar analysis can be done for Cr(Dcb)2, whose eigen energy of LUMO in the T configuration is lower than that in the C configuration and adding an electron in Cr(Dcb)2 can thus rotate the ligands and so the T configuration is more favorable for Cr(Dcb)2. For V(Dcb)2, the LUMO has a lower eigen energy in the T configuration than that in the C configuration; thus the anion tends to form a T configuration. In contrast, in the neutral V(Dcb)2 cluster, the eigen energies of HOMOs in C and T configuration are close, while the orbital distribution in the cationic C configuration is more delocalized implying its relatively higher stability (see Figure S4 in the Supporting Information); hence, V(Dcb)2+ energetically favors the C configuration. As for Mn(Dcb)2, the T configuration gives lower eigen energy of LUMO than the C one, so an extra electron coming to Mn(Dcb)2 will prefer to occupy the LUMO of the T configuration; thus, the anionic Mn(Dcb)2 has the same configuration with the neutral one. Interestingly, although the eigen energies of HOMOs in C and T configurations are close in the Mn(Dcb)2 cluster (about 0.01 eV), the ligand rotation is still observed upon removal of an electron. This is because more frontier occupied bonding orbitals are formed in the C configuration than those in the T configuration in the cationic Mn(Dcb)2+ clusters (see Figure S5 in the Supporting Information), which enhances the stability of the C configuration.
IV. CONCLUSION In summary, the structural, electronic, and magnetic properties of TM(Dcb)2 (TM = ScMn) sandwich clusters were systematically studied by using a spin-polarized all electron density functional theory approach. All the ground states of TM(Dcb)2 clusters are of high stability with BEs all larger than 5.0 eV, which is due to the ioniccovalent bonding between TM and Dcb ligands. The Ti(Dcb)2 cluster is the most stable with the largest HOMOLUMO gap and binding energy, the Sc- and
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V(Dcb)2 are intermediate, while the Cr- and Mn(Dcb)2 are the least stable. The large BE ensures the cluster will not decompose into small fragments under finite temperature. Compared to the synthesized species Co(Dcb)2, the TM(Dcb)2 clusters have higher or at least similar stability; hence, these clusters might be accessible in experiment. More interestingly, these TM(Dcb)2 clusters show rich magnetic properties with 1, 1, 2, and 3 μB magnetic moments for Sc-, V-, Cr-, and Mn(Dcb)2, respectively, while Ti(Dcb)2 has zero spin. Different from those of V-, Cr-, and Mn(Dcb)2 clusters, the magnetism origin of Sc(Dcb)2 is from an unpaired orbital of its two ligands. The element-dependent magnetic moments are well understood from electron transfer and spin density distribution. Due to their tunable magnetic moments, the TM(Dcb)2 clusters might be utilized as molecular magnets in a variety of important applications such as quantum computing and magnetic information storage. Moreover, we found that adding or removing an electron can lead to the rotation of the ligands in the Sc-, V-, Cr-, and Mn(Dcb)2 clusters, while the rotational barrier is relatively small. Therefore, these clusters will be good alternatives for the design of molecular motors, which might provide us with more flexibility in fabricating the nanoengine of the nanomachine in the future.
’ ASSOCIATED CONTENT
bS
Supporting Information. Structural, energetic, and magnetic properties of the lowest-energy and low-lying states of TM(Dcb)2 sandwich clusters (Table S1), optimized geometrical parameters for ground state of isolated Dcb and neutral and charged TM(Dcb)2 (TM = ScMn) complexes (Table S2), natural population analysis (NPA) of TM in the sandwich complexes (Table S3), structural, electronic, and magnetic properties of neutral and charged TM(Dcb)2 clusters (Table S4), optimized lowest energy transoid (T) and cisoid (C) configurations of TM(Dcb)2 (TM = ScMn) sandwich clusters (Figure S1), schematic of obrbital interaction for Ti(Dcb)2 with Ti4+ and Dcb2- as fragments (Figure S2), optimized lowest energy structures of neutral and charged TM(Dcb)2 (TM = ScMn) sandwich clusters (Figure S3), occupied frontier orbitals for lowest energy cisoid (C) configuration and transoid (T) configuration of V(Dcb)2+ (Figure S4) and Mn(Dcb)2+ (Figure S5) clusters. This material is available free of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION Corresponding Author
*E-mail:
[email protected].
’ ACKNOWLEDGMENT This work is supported by the NSF (Grant Nos. 11074035, 20873019), NBRP (Contract Nos. 2011CB302004, 2010CB923401, 2009CB623200), SRFDP (Contract No. 20090092110025), the Outstanding Yong Faculty Grant, and Peiyu Foundations of SEU in China. The authors thank the computational resource center at the Department of Physics, SEU. ’ REFERENCES (1) Coulson, C. A.; Higgs, P. W.; March, N. H. Nature 1951, 168, 1039. (2) Wilkinson, G.; Rosenblum, M.; Whiting, M. C.; Woodward, R. B. J. Am. Chem. Soc. 1952, 74, 2125. 14546
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The Journal of Physical Chemistry C (3) Kurikawa, T.; Takeda, H.; Hirano, M.; Judai, K.; Arita, T.; Nagao, S.; Nakajima, A.; Kaya, K. Organometallics 1999, 18, 1430. (4) Ma, J. C.; Dougherty, D. A. Chem. Rev. 1997, 97, 1303. (5) Kurikawa, T.; Negishi, Y.; Hayakawa, F.; Nagao, S.; Miyajima, K.; Nakajima, A.; Kaya, K. J. Am. Chem. Soc. 1998, 120, 11766. (6) Hosoya, N.; Takegami, R.; Suzumura, J.-i.; Yada, K.; Koyasu, K.; Miyajima, K.; Mitsui, M.; Knickelbein, M. B.; Yabushita, S.; Nakajima, A. J. Phys. Chem. A 2004, 109, 9. (7) Hoshino, K.; Kurikawa, T.; Takeda, H.; Nakajima, A.; Kaya, K. J. Phys. Chem. 1995, 99, 3053. (8) Miyajima, K.; Knickelbein, M. B.; Nakajima, A. J. Phys. Chem. A 2008, 112, 366. (9) Miyajima, K.; Nakajima, A.; Yabushita, S.; Knickelbein, M. B.; Kaya, K. J. Am. Chem. Soc. 2004, 126, 13202. (10) Miyajima, K.; Yabushita, S.; Knickelbein, M. B.; Nakajima, A. J. Am. Chem. Soc. 2007, 129, 8473. (11) von Fisher, E. O. J., G.; Meer, W. Z. Naturforshung 1958, 13b, 456. (12) Zhu, L.; Wang, J.; Yang, M. J. Mol. Struct.: THEOCHEM 2008, 869, 37. (13) Pandey, R.; Rao, B. K.; Jena, P.; Blanco, M. A. J. Am. Chem. Soc. 2001, 123, 3799. (14) Wang, J.; Acioli, P. H.; Jellinek, J. J. Am. Chem. Soc. 2005, 127, 2812. (15) Xiang, H.; Yang, J.; Hou, J. G.; Zhu, Q. J. Am. Chem. Soc. 2006, 128, 2310. (16) Zhang, X.; Ng, M.-F.; Wang, Y.; Wang, J.; Yang, S.-W. ACS Nano 2009, 3, 2515. (17) Zhang, X.; Wang, J. J. Phys. Chem. A 2010, 114, 2319. (18) Zhang, X.; Wang, J.; Gao, Y.; Zeng, X. C. ACS Nano 2009, 3, 537. (19) Zhou, L.; Yang, S.-W.; Ng, M.-F.; Sullivan, M. B.; Tan; Shen, L. J. Am. Chem. Soc. 2008, 130, 4023. (20) Zhu, L.; Wang, J. J. Phys. Chem. C 2009, 113, 8767. (21) Zhu, L.; Zhang, T.; Yi, M.; Wang, J. J. Phys. Chem. A 2010, 114, 9398. (22) Kandalam, A. K.; Rao, B. K.; Jena, P.; Pandey, R. J. Chem. Phys. 2004, 120, 10414. (23) Dutta, S.; Mandal, T. K.; Datta, A.; Pati, S. K. Chem. Phys. Lett. 2009, 479, 133. (24) Valencia, I.; Castro, M. J. Phys. Chem. A 2010, 114, 13303. (25) Datta, A.; Mallajosyula, S. S.; Pati, S. K. Acc. Chem. Res. 2007, 40, 213. (26) Shen, L.; Yang, S.-W.; Ng, M.-F.; Ligatchev, V.; Zhou, L.; Feng, Y. J. Am. Chem. Soc. 2008, 130, 13956. (27) Nagao, S.; Kato, A.; Nakajima, A.; Kaya, K. J. Am. Chem. Soc. 2000, 122, 4221. (28) Wang, L.; Cai, Z.; Wang, J.; Lu, J.; Luo, G.; Lai, L.; Zhou, J.; Qin, R.; Gao, Z.; Yu, D.; Li, G.; Mei, W. N.; Sanvito, S. Nano Lett. 2008, 8, 3640. (29) Shen, L.; Jin, H.; Ligatchev, V.; Yang, S.-W.; Sullivan, M. B.; Feng, Y. Phys. Chem. Chem. Phys. 2010, 12, 4555. (30) Da, H.; Jin, H. M.; Yang, S.-W.; Lim, K. H. J. Phys. Chem. C 2009, 113, 21422. (31) Da, H.; Jin, H. M.; Lim, K. H.; Yang, S.-W. J. Phys. Chem. C 2010, 114, 21705. (32) Zhang, X.; Tian, Z.; Yang, S.-W.; Wang, J. J. Phys. Chem. C 2011, 115, 2948. (33) Zhang, X.; Wang, J.; Zeng, X. C. J. Phys. Chem. A 2009, 113, 5406. (34) Nakajima, A.; Kaya, K. J. Phys. Chem. A 2000, 104, 176. (35) Nakajima, A.; Nagao, S.; Takeda, H.; Kurikawa, T.; Kaya, K. J. Chem. Phys. 1997, 107, 6491. (36) Lipscomb, W. N. Science 1966, 153, 373. (37) Hawthorne, M. F.; Young, D. C.; Andrews, T. D.; Howe, D. V.; Pilling, R. L.; Pitts, A. D.; Reintjes, M.; Warren, L. F.; Wegner, P. A. J. Am. Chem. Soc. 1968, 90, 879. (38) Hanusa, T. P. Polyhedron 1982, 1, 663.
ARTICLE
(39) de Rege, F. M.; Smith, W. H.; Scott, B. L.; Nielsen, J. B.; Abney, K. D. Inorg. Chem. 1998, 37, 3664. (40) Hawthorne, M. F.; Young, D. C.; Wegner, P. A. J. Am. Chem. Soc. 1965, 87, 1818. (41) Zalkin, A.; Hopkins, T. E.; Templeton, D. H. Inorg. Chem. 1967, 6, 1911. (42) Borodinsky, L.; Sinn, E.; Grimes, R. N. Inorg. Chem. 1982, 21, 1686. (43) Chamberlin, R. M.; Scott, B. L.; Melo, M. M.; Abney, K. D. Inorg. Chem. 1997, 36, 809. (44) St. Clair, D.; Zalkin, A.; Templeton, D. H. J. Am. Chem. Soc. 1970, 92, 1173. (45) Hawthorne, M. F.; Zink, J. I.; Skelton, J. M.; Bayer, M. J.; Liu, C.; Livshits, E.; Baer, R.; Neuhauser, D. Science 2004, 303, 1849. (46) Warren, L. F.; Hawthorne, M. F. J. Am. Chem. Soc. 1968, 90, 4823. (47) Wing, R. M. J. Am. Chem. Soc. 1967, 89, 5599. (48) Wing, R. M. J. Am. Chem. Soc. 1968, 90, 4828. (49) B€uhl, M.; Hnyk, D.; Machacek, J. Chem.—Eur. J. 2005, 11, 4109. (50) B€uhl, M.; Holub, J.; Hnyk, D.; Machacek, J. Organometallics 2006, 25, 2173. (51) B€uhl, M.; Hnyk, D.; Machacek, J. Inorg. Chem. 2007, 46, 1771. (52) Singh, A. K.; Sadrzadeh, A.; Yakobson, B. I. J. Am. Chem. Soc. 2010, 132, 14126. (53) Grimes, R. N. Coord. Chem. Rev. 2000, 200202, 773. (54) Hart, F. A.; Owen, D. W. Inorg. Chim. Acta 1985, 103, L1. (55) Long, J. A.; Marder, T. B.; Behnken, P. E.; Hawthorne, M. F. J. Am. Chem. Soc. 1984, 106, 2979. (56) King, R. E.; Busby, D. C.; Hawthorne, M. F. J. Organomet. Chem. 1985, 279, 103. (57) Plesek, J. Chem. Rev. 1992, 92, 269and references cited therein. (58) Soloway, A. H.; Tjarks, W.; Barnum, B. A.; Rong, F.-G.; Barth, R. F.; Codogni, I. M.; Wilson, J. G. Chem. Rev. 1998, 98, 1515. (59) Sivaev, I. B.; Bregadze, V. V. Eur. J. Inorg. Chem. 2009, 11, 1433. (60) Sivaev, I. B.; Semioshkin, A. A.; Bregadze, V. I. Appl. Radiat. Isot. 2009, 67, S91. (61) Cigler, P.; Kozisek, M.; Rezacova, P.; Brynda, J.; Otwinowski, Z.; Pokorna, J.; Plesek, J.; Gruner, B.; Doleckova-Maresova, L.; Masa, M.; Sedlacek, J.; Bodem, J.; Krausslich, H. G.; Kral, V.; Konvalinka, J. Proc. Natl. Acad. Sci. U.S.A. 2005, 102, 15394. (62) Li, T. C.; Spokoyny, A. M.; She, C.; Farha, O. K.; Mirkin, C. A.; Marks, T. J.; Hupp, J. T. J. Am. Chem. Soc. 2010, 132, 4580. (63) Delley, B. J. Chem. Phys. 1990, 92, 508. (64) Delley, B. J. Chem. Phys. 2000, 113, 7756. (65) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. Rev. Lett. 1996, 77, 3865. (66) Hardie, M. J.; Raston, C. L. Angew. Chem. 2000, 112, 3993. (67) Wade, K. Adv. Inorg. Chem. 1976, 18, 1. (68) Jose, D.; Datta, A. J. Phys. Chem. Lett. 2010, 1, 1363.
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dx.doi.org/10.1021/jp202531c |J. Phys. Chem. C 2011, 115, 14542–14547
