Theoretical Study of Small Scandium-Doped Silver Clusters ScAgn

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Theoretical Study of Small Scandium-Doped Silver Clusters ScAgn with n = 1-7: #-Aromatic Feature Hung Tan Pham, Loc Quang Ngo, My Phuong Pham-Ho, and Minh Tho Nguyen J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.6b08080 • Publication Date (Web): 20 Sep 2016 Downloaded from http://pubs.acs.org on September 22, 2016

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The Journal of Physical Chemistry

Theoretical Study of Small Scandium-doped Silver Clusters ScAgn with n = 1-7: σ-Aromatic Feature Hung Tan Pham,a Loc Quang Ngo,a My Phuong Pham-Ho,a,* Minh Tho Nguyenb,* a

Institute for Computational Science and Technology (ICST), Ho Chi Minh City, Viet Nam

b

Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium.

Abstract: Geometry, chemical bonding and aromatic feature of a series of small silver clusters doped by an Sc atom (ScAgn with n = 1-7) were investigated by mean of DFT calculations. A planar shape is found for ScAgn including n from 4 to 7. The growth mechanism is established for the formation of the hexagonal and heptagonal metallic cycles following increase of the number of Ag atoms. Particularly, both clusters ScAg6- and ScAg7 present a planar cyclic form in which the Sc atom is situated at the central position of the Ag6 and Ag7 cycles. The σ-aromaticity is unambiguously demonstrated by the existence of strongly diatropic current flows within the ring in both ScAg6and ScAg7. The isovalent ScCu7 cluster has a similar ring current characteristic. In the Sc doped ScAgn clusters, a delocalized bonding pattern is found as a connector between the dopant Sc and the Agn host, as indicated by an ELI_D analysis.

*

Emails: [email protected]; [email protected] 1 ACS Paragon Plus Environment


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1. Introduction The concept of aromaticity was introduced by Kekule in 1865 in an attempt to rationalize the particular thermodynamic stability and chemical reactivity of benzene and its derivatives.1,2,3 With the aim of theoretically predicting the aromaticity of monocyclic hydrocarbons, Hückel established in 1931 the milestone formula of (4N + 2) to count their π electrons.4,5 This simple rule points out that if an unsaturated cyclic hydrocarbon molecule has a number of π electrons satisfying the (4N+2) count, this species is aromatic and has thereby a high stability and low reactivity. Subsequently, Breslow defined in 1970 the associated concept of anti-aromaticity in which a molecule containing 4N π electrons is thermodynamically unstable and highly reactive.6 Since then, the 4N/4N + 2 electron count rules emerged as the simplest and most popular indicator for the aromatic character of not only hydrocarbons but also of different classes of organic and inorganic compounds. The emergence of elemental clusters has given an unexpected expansion of the aromatic character. As for a prototype of aromatic cycle containing metal atoms, the dianion Al42- has been the subject of several experimental and theoretical studies.7,8,9,10,11,12,13,14,15,16,17 Based on an MO analysis and NICS calculations, the tetra-atomic cluster Al42- has been considered as having a triple aromaticity involving σ-radial, σ-tangential and π-planar aromaticity.9 However, subsequent ring current calculations that evaluated the orbital contributions to the magnetic responses of the electron density clearly demonstrated that Al42- is an σ-aromatic species rather than a triple aromatic compound.15,16,17 Planar metallic cycles not only contain a high coordination but also involve often a double σ and π aromaticity. For instance, let us consider the species B@B72- and B@B8-, both sets of σ and π delocalized MOs are considered to be aromatic as indicated by ring current calculations.18 Additionally, by exploring the ring current maps of both delocalized σ and 2 ACS Paragon Plus Environment

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π orbitals, the M@B6H6q and M@B7H7q planar cycles with M = Cr, Mn and Fe and q (charge) = 1, 0 and +1 provide us with another kind of double aromaticity.19 As indicated by CMO analyses and mostly by negative NICS values, the dianions Zn 32-, Cd32- and Hg32- were classified as π aromatic with 2 π electrons. 20 The planar transition metal centered five-membered ring [Fe(Sb)5]+ and [Fe(Bi)5]+ clusters were characterized to be πaromatic in agreement with the existence of 10 delocalized π electrons.21 While the main group elements can lead to either a single π or a double π and σ aromaticity, the δ-aromaticity which is formed by d-d interactions, has been observed for planar cycles containing transition metals. The Hf3 (1A1’ D3h) cluster was shown to exhibit a triple σ, π and δ aromaticity.22 The δ aromatic character was identified by canonical MO analysis and negative NICS value for the W32- and W3O92- clusters.23,24 In the latter, a combination of 5d-AOs of W atoms produces delocalized MOs that turn out to be responsible for a δ aromaticity with two delocalized electrons. The 5d-AOs generate delocalized δ MOs occupied by two electrons in the anion Ta3- and its oxides including Ta3O- and Ta3O3-. As a result, they are considered as δ aromatic species.25,26 Although d-d interactions tend to induce a δ aromaticity, both σ and π aromatic characters are mainly found in metallic cycles. There is a debate on the aromatic character of hydrometallic and transition metal cycles. On the basis of a NICS and CMO analysis, the CunHn hydrometallic cycles, which is in perfect planar shape with high Dnh symmetry, are classified as the triple σ, π and δ aromatic feature.27 Similar phenomena were also observed for the isovalent clusters AunHn and AgnHn again with n = 3-6.28 In particular, the mixed coinage metal clusters CunAg3-nH3, CunAg4-nH4 and CunAg5-nH5 were found to be stable in planar geometry, and their triple aromaticity is contributed by σ, π and

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δ components.29 However, these hydrometallic cycles are considered as non-aromatic species according to the GIMIC30, MCI31 and CMO-NICS calculations.32,33,34 Transition metal clusters containing only σ aromaticity are rather scarce.35,36 The trimeric cationic trimers of coinage metals Cu3+, Ag3+ and Au3+ were characterized as σ aromatic cycles.37 However, the ring current analysis clearly showed that these species present strong local paramagnetic currents around the atomic nuclei rather than moving through the whole cluster. As a consequence, they should be classified as non-aromatic clusters.38 The aromatic feature of planar Cu42-, Ag42- and Au42- clusters were rationalized by using magnetic responses that pointed out that six delocalized σ electrons are the main contributors to the ring current flows. Accordingly, these planar coinage metal clusters are classified as σ aromatic. Structural identifications demonstrated that the scandium-doped copper cluster ScCu7 is a beautiful heptagonal cycle in which the Sc atom is located at the center of the ring, whereas the smaller analogues ScCu6 and ScCu5 were found to be in a 3D form. Perhaps more interestingly is the fact that the seven-membered ScCu7 cycle is an σ aromatic species containing 10 delocalized σ electrons as supported by NICS calculations and ELI_D analysis.36 The yttrium doped gold cluster YAu6- cluster, characterized as a D6h planar structure with Y occupying the central position of a six-membered ring, is also σ aromatic with 10 delocalized σ electrons.39 In this context, a legitimate question emerges as to whether an σ aromaticity can be recovered in isovalent species of YAu6- and ScCu7 containing silver atoms such as ScAg6- and ScAg7, respectively. For silver clusters, the sizes of 6 and 7 Ag atoms have been identified as structures in which a transition from 2D to 3D form of small sizes occurs.40,41,42,43,44 A systematic investigation of the neutral and charged Agn-/0/+ clusters with n = 1-15 showed that these clusters undergo a transition from spherical to prolate to oblate form.45 The pure and mixed silver clusters have been the subject 4 ACS Paragon Plus Environment

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of several experimental and theoretical studies.46,47,48 However, study of silver cluster doped by 3d transition metals is quite limited. An extensive search on Ag5M0/- with M being a 3d transition metal using both experiment and DFT calculations showed that both 2D and 3D structures coexist.49 Particularly, of the 3d transition metal doped MAgn+ clusters, the size CoAg10+ presents an endoheral structure with singlet spin state.50 The quenching and high stability of CoAg10+ was rationalized in term of the 18 electron rule. More recently, the V-doped clusters VAg14+ and VAg15 are identified to have high stability with 18 and 20 electrons shells, respectively.51 In this context, we set out to search for Ag clusters featuring only an σ aromatic character. For this aim, we perform a systematic investigation on the geometric and electronic structure of small scandium-doped silver clusters ScAgn using quantum chemical calculations. The Sc atom is selected in view of its behavior in the ScCun clusters. Concerning the rationalization of aromaticity, it has recently been shown that the one-point NICS values often draw incorrect predictions for cyclic metallic systems, whereas the ring current maps appear to behave as consistent magnetic indicators.16,17,19,52 2. Computational Methods All geometry optimizations and energy calculations are performed using the Gaussian 09 suite of program.53 A stochastic genetic algorithm is used to generate the initial geometries for the ScAgn clusters.54 They are firstly optimized using density functional theory (DFT) with the hybrid functional B3LYP and the small LAN2DZ basis set.55,56 The lower-energy isomers identified at this level, within a range of 50 kcal/mol on relative energies with respect to the lowest-lying isomer, are subsequently reoptimized using the same functional but in conjunction with the larger cc-pVTZ basis set for the Sc atom and the cc-pVTZ-PP for Ag atom.57 In the latter, PP stands for an effective core potential which also includes the relativistic effects. The electronic structure and 5 ACS Paragon Plus Environment


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chemical bonding features of the ScAgn global energy minimum structures are then explored carrying out a partition of the electron density. This is achieved by using the electron localizability indicator (ELI_D) 58 and the magnetic responses expressed in terms of ring currents. Calculations on the ring current maps are carried out using the SYSMO program,59,60 which is connected to the GAMESS-UK package.61 As for a convention, a diatropic current density corresponds to an aromatic character, whereas a paratropic current indicates an anti-aromatic character. For the sake of comparison, the σ aromatic character of the ScCu7 cluster, which was pointed out in previous studies, is also revisited by ring current calculations. 3. Results and Discussion We first briefly describe the geometries of a series of the smallest scandium-doped silver clusters considered and establish their growth pattern. In the following sections, the electron distribution and chemical bonding phenomena in these clusters will be examined, with a particular focus on their aromatic character. 3.1 Geometrical Aspects The shape, electronic state and relative energies of the lower-lying isomers of the clusters ScAgn considered are displayed in Figure 1 for n = 1-4 and Figure 2 for n = 5-7. ScAg and ScAg2. The diatomic Sc-Ag is identified to have a triplet ground state with an equilibrium distance of 2.7 Å. The closed-shell singlet state is ~8 kcal/mol above. For the triatomic ScAg2 and its anion, the linear structure in which the Sc atom is located in the middle turns out to be the lowest-energy isomer. ScAg3. The global minimum structure 3.A is planar, in which the Sc dopant occupies the central position of the equilateral Ag3 cycle. The tetraatomic 3.A can thus be formed upon adding the Sc 6 ACS Paragon Plus Environment

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atom to the Ag3 cluster. The next isomer 3.B has also a planar shape and is located at ~5 kcal/mol and ~9 kcal/mol above the ground state for the triplet and singlet states, respectively. The 3.B form was previously predicted as the global minimum structure of the PdAg3 cluster.62 However, the Sc dopant does not favor this shape. ScAg4. Extensive search on the isomers of the penta-atomic ScAg4 cluster results in the planar 4.A (C2v 2B2) as the most stable structure. Basically 4.A could be generated by substitution of an Ag atom of the Ag5 structure which has the highest coordination state.45 The same shape is also found for the penta-atomic PdAg4 and VAg4 clusters in which either the Pd62 or the V63 dopant is surrounded by four Ag atoms. The 4.B shown in Figure 1 results from attachment of a Sc atom into the Ag4 square, and is at ~10 kcal/mol above 4.A. The isomers including 4.C and 4.D seen in Figure 1 have 3D shape and are much less stable. ScAg5. As shown in Figure 2, the incomplete planar hexagon 5.A (C2v 1A1), as the lowest-lying energy isomer, is consistent with previous results on the geometry of the ScAg50/- clusters.49 ScAg6-. DFT calculations indicate that the singlet and high symmetry 6.A (D6h 1A1g) is the lowest energy isomer. This structure presents a particular shape in which the Sc dopant is situated at the central position of the hexagonal Ag6 ring. Let us mention that the pure neutral Ag7 cluster was identified as a pentagonal bipyramid.45 Accordingly, the Sc atom strongly affects the geometry of when replacing an Ag atom. The next isomers including 6.B, 6.C and 6.D that are formed by adding an Ag atom to the ScAg5 cluster at various sites are highly unstable. This behavior of ScAg6differs thus from the isovalent ScCu6- which has a 3D shape64, but similar to the isovalent YAu6which has high symmetry planar form (D6h).39 It is apparent that the larger size of the Ag6 and Au6 rings allows the metal dopant to be endohedrally incorporated.



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ScAg7. There is a competition for the ground state in case of ScAg7 cluster. The planar 7.B (D7h 1

A1g) in which the Sc atom is located at the center of a planar heptagonal Ag7 ring, is only ~2

kcal/mol higher than 7.A. In a view, 7.A actually arises from a strong distortion of 7.B. With the expected accuracy of DFT calculations (~ 3-4 kcal/mol), both of them can be regarded as competitive for the ground state of ScAg7. Because the Ag7 ring is large, it tends to undergo distortion upon doping. 3.2 Growth Pattern: Formation of Hexagonal and Heptagonal Cycles From geometrical characteristics described above, the growth pattern of the ScAgn clusters can thus be revealed, and illustrated in Figure 3. The ScAg2 structure is generated following addition of an Ag atom to the diatomic Sc-Ag. Then the ScAg3 cyclic structure results from an attachment of one more Ag to the trimer ScAg2. The ScAg4 cluster arises from both addition and substitution pathways. Replacement of an Ag site on Ag5 by Sc, or addition of one Ag atom to ScAg3 equally ends up in the ScAg4 global minimum. More interestingly, this structure is actually a fragment of hexagonal and heptagonal cycles. As a matter of fact, addition of two and three Ag atoms to the ScAg4 unit result in the hexagonal and heptagonal cycles of ScAg6 and ScAg7, respectively. It is obvious that the incomplete hexagonal ScAg5 cluster is formed by a combination of an Ag atom with the most stable ScAg4 structure. Finally, the planar hexagonal cycle ScAg6 is produced upon addition of one Ag atom to the ScAg5. Attachment of Ag to the hexagonal ScAg6 cycle gives subsequently rise to the heptagonal cycle. Overall, upon doping of a Sc atom, the resulting ScAgn clusters up to the sizes of n = 6 and 7 follow a rather simple route leading to formation of hexagonal and heptagonal cycles. 3.3 The Electronic Shell Model


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The high thermodynamic stability of the planar form of singly doped MAgn clusters whose dopant is a transition metal atom, was previously rationalized as a results of a strong stabilizing orbital interaction of the metal atom with the Agn hosts.50,51 Such an interaction gives rise to a MO pattern of MAgn satisfying the eigenstates inherently produced by the electron shell model. We thus use this simple approach to probe the stability of the planar ScAg6 and ScAg7 cycles. In the shell model, nuclei are ignored and replaced by a mean field, while electrons are considered to move freely within this mean field. The S, P, D, F,… orbitals according to the angular momentum numbers L = 0,1,2,3... are generated and successively filled by the valence electrons. With a given quantum number L, the lowest-lying level has a principle number N = 1. In the framework of the shell model, a successive occupation of a level, giving rise to a magic number, leads to a stabilized cluster. In order to determine the electron shells, partial densities of state (pDOS) are calculated for Sc atom and Agn cycle with n = 6 and 7 and displayed in Figures 4 and 5. Total densities of state (DOS) involving all contributions from both the dopant Sc and the Ag6 and Ag7 hosts are displayed in the same Figures 4 and 5. Combining with the MO shape, the electron shell configurations of these clusters can unambiguously be established. The orbital overlap between Ag and Sc (Figures 4 and 5) yields the shell configuration as [1S2 1P4 1D4…] occupied by 10 electrons for both the anion ScAg6- and the neutral ScAg7. The same shell configuration was found in the case of the planar isovalent YAu6- and ScCu7 clusters. The valence electrons of both Sc or Y dopants and the Cu7, Ag6,7 or Au6 hosts can then fully occupy the electron shell of [1S2 1P4 1D4...] and consequently stabilize the resulting planar clusters. 3.4 Chemical Bonding Analysis Using Orbital Interaction



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To obtain a deeper understanding on chemical bonding of Sc@Ag7 and Sc@Ag6- planar cycles, the orbital interactions of the Sc atom with the Ag7 and Ag6- cycles are constructed. As shown in Figure 6, the 1S level of Ag7 and Ag6- combines with the 4s orbital of Sc, and thereby establish the 1S subshell for Sc@Ag7 and Sc@Ag6- clusters. Clearly, the 1P subshells of Sc@Ag7 and Sc@Ag6- clusters are mainly contributed by the 1P levels Ag7 and Ag6- cycles. The 3d orbitals of Sc dopant enjoy a stabilizing interaction with the 1D levels of Ag7 and Ag6- strings, and subsequently give rise to the 1D subshells, each of which is occupied by 4 electrons of either Sc@Ag7 or Sc@Ag6- planar structure. As a result, orbital interactions between Sc and Ag7 and Ag6- cycles induce a thermodynamic stability for the resulting clusters. 3.5 Electron Partition Using the Electron Localizability Indicator (ELI_D) and WBI In order to obtain a deeper understanding of the bonding pattern of the ScAgn clusters, we now use the electron localizability indicator (ELI_D) to probe the electron distribution. This method includes a partition of the total electron density into basins where electrons are populated. As given in Figure 7, the ELI_D maps that are plotted at the bifurcation of 1.15 of the ScAg, ScAg2 and ScAg3 clusters, clearly indicate the localization domains between Sc and Ag. In these systems the Sc dopant connects to the Ag hosts through localized bonds. At the bifurcation value of 0.98, the ELI_D map of ScAg4 illustrates a localization domain which is distributed over the region between Ag atoms and the Sc center. In other words, in the ScAg4 cluster, the Sc dopant induces delocalized bond with the Ag4 host. A similar result is recovered for the hexa-atomic ScAg5 cluster in which a localization domain populated in the space between Sc and Ag5 host is present. This indicates the existence of a delocalized bond.


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At the bifurcation value of ELI_D = 0.925, the localization domain which is distributed over the region covering the Sc dopant and the Agn host, is again found for both ScAg6- and ScAg7. The connection between the Sc atom to each of the Ag6 and Ag7 cycles is thus made by delocalized electrons. The fact that the Sc dopant tends to connect with the Agn hosts, from the size of ScAg4, through delocalized bonding pattern is consistent with the results derived from the DOS analysis described in the previous section. To obtain a deeper insight into the bonding features of Sc@Ag6- and Sc@Ag7 planar clusters, the Wiberg bond indices (WBI) are calculated for the relevant Ag-Ag and Sc-Ag connections. As a result, all Sc-Ag connection of Sc@Ag7 have a WBI value of 1.0 whereas in Sc@Ag6- the six Sc-Ag bonds have the same WBI value of 0.8. Additionally, WBI values of ~0.8 are calculated for all Ag-Ag connections in both Sc@Ag6- and Sc@Ag7. These results clearly point out the existence of electron sharing between Ag atoms in Sc@Ag6- and Sc@Ag7 cycles. 3.6 The σAromaticity of Planar ScAg6- and ScAg7. A Comparison with ScCu7 Let us now probe the aromatic feature of the planar ScAg6- and ScAg7 metallic cycles using the magnetic responses of the electron density as expressed by ring current flows. As for a comparison with the behavior of the isovalent ScCu7, the ring current maps of the latter are also generated. The total ring current flow which is contributed by all valence electrons of both ScAg7 and ScCu7 are displayed in Figure 8. Both species generate strongly diatropic current maps in terms of magnetic responses. Therefore, they can be classified as aromatic species. The most remarkable feature is that total ring current of ScAg7 and ScCu7 are entirely contributed by σ valence electrons, due to the fact that these clusters do not contain π electrons. It is obvious that both clusters bear an σ aromatic character. As indicated by both DOS and ELI_D analysis, the valence electrons of 11 ACS Paragon Plus Environment


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either ScAg7 or ScCu7 are not only delocalized over whole cluster but also satisfy the (4N+2) electron count. In the present case, the classical (4N + 2) rule draws a consistent conclusion with the ring current criteria. In order to further probe their aromatic feature, the orbital contributions to the ring currents are performed and displayed in Figure 8. It thus appears that the doubly degenerate HOMO and HOMO’ constitute the main contributors to the ring current maps whereas the HOMO-1,1’ and HOMO-2 are not active in magnetic response. For a comparison of the electron circulation within the ring, the ring current maps of the planar Ag73- and Cu73- heptagonal trianions, that are isovalent to both ScCu7 and ScAg7 clusters, are also performed (Figure 9). As expected, strongly diatropic current density are also identified for both Ag73- and Cu73- cycles indicating also their σ aromatic feature. This result confirms that the Sc dopant supplies all of its three valence electrons to the whole molecular σ system. In order to quantify the aromaticity level of both Sc@Cu7 and Sc@Ag7, the jmax values are calculated and compared to Al42- which is considered as a typical all-metal aromaticity. This quantity can be regarded as a measure of the maximum strength of the current per unit inducing field. It should be noted that the current maps mainly convey qualitative information about aromaticity, whereas the jmax values are a more quantitative criterion. In other words, the jmax value could also be used to quantitatively evaluate the degree of aromaticity. Both Sc@Ag7 and ScCu7 have jmax value of 0.06, whereas the jmax of Al42- is found to be 0.05. As a consequence, both Sc@Ag7 and ScCu7 cycles have a comparable level of aromatocoty as Al42-. 4. Conclusions


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In the present theoretical study, we have investigated the geometry, chemical bonding and aromatic feature of the smallest Sc doped silver clusters ScAgn with n = 2-7. Geometric identifications show that all of ScAgn clusters have a planar shape in which the Sc dopant prefers a high coordination position. In particular, the ScAg6- and ScAg7 present a planar metallic cyclic form in which the Sc atom is located at the central position of the Ag6 and Ag7 cycles. The growth mechanism can be established in which formation of the hexagonal and heptagonal metallic cycles can be achieved following increase of the number of Ag atoms. The partition of the total electron density using the ELI_D approach demonstrates that the Sc dopant connects to the Agn hosts through a delocalized orbital pattern. Magnetic ring current calculations show that both the ScAg6and ScAg7 clusters exhibit a σ aromatic character, similar to the isovalent species YAu6- and ScCu7. Acknowledgments: The authors thank the Department of Science and Technology of Ho Chi Minh City, Vietnam, for supporting our work at ICST. MTN is indebted to the KU Leuven Research Council (GOA program) and FWO-Vlaanderen.



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Figure Captions: Figure1: Shape of lower-lying isomers of Ag2Sc- and AgnSc clusters with n = 1, 3 and 4. Geometry optimizations were performed using B3LYP/cc-pVTZ:Sc and cc-pVTZ-PP:Ag computations. Figure 2: Shape of lower-lying isomers of Ag6Sc- and AgnSc clusters with n = 5 and 7. Geometry optimizations were performed using B3LYP/cc-pVTZ:Sc and cc-pVTZ-PP:Ag computations. Figure 3: The growth mechanism of the series of small Sc doped silver clusters. Figure 4: The DOS and pDOS plots of ScAg6- planar cluster. Figure 5: The DOS and pDOS plots of ScAg7 planar cluster. Figure 6: The orbital interactions of the Sc atom with Ag6- and Ag7 strings giving the Sc@Ag6and Sc@Ag7 cycles. Figure 7: ELI_D surfaces: ScAg5, ScAg6 and ScAg7 are plotted at bifurcation value ELI_D = 0.925, and ScAg, ScAg2 and ScAg3 performed at ELI_D = 1.15, and ScAg4 at ELI_D = 0.98. Figure 8: Total ring currents of b) ScCu7 and Cu73- and b) ScAg7 and Ag73- cycles. Figure 9: Orbital contributions to the ring currents of a) ScAg7 and b) ScCu7.


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1.A

2.A.a

2.B.a

C∞v 3Σg 0

D∞h 1Σg 0

C∞v 1Σg 11

C∞v 1Σg 7.5

D∞h 3Σg 4

C∞v 3Σg 18

3.A.

3.B.

D3h 1A1 0

C2v 1A1 9.3

C2v 3B2 5.5

C2v 3A2 4.4

4.A.

4.B.

4.C.

4.D.

C2v 2B2 0.0

C4v 2A 9.8

C2v 2B1 10

Cs 2A’ 11.0

C2v 4B2 20.0

C2v 4B1 19.0

S4 4A 23.0

Cs 4A” 20.0

Figure 1.



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5.A C2v 1A 0

5.B C4s 1A1 5

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5.C Cs 1A 6

5.D Cs 1A 11

6.C.a C1 1A 12 Cs 3A 20

6.D.a Cs 1A 14 Cs 3A 21

7.C Cs 1A 5.1 Cs 3A 15

7.D Cs 1A 6.0 Cs 3A 10

ScAg5

6.A.a D6h 1A1g 0 D2h 3Ag 17

6.B.a Cs 1A 11 Cs 3A 15

ScAg6-

7.A

7.B

1

1

C2 A1 0.0 Cs 3A 12

D7h A1g 2.4 D7h 3A1g 19

ScAg7 Figure 2.


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+Ag C∞v ScAg

D∞h ScAg2

+2Ag

+Ag

+2Ag

+Ag D3h ScAg3 +Ag

C2v ScAg5

C2v ScAg4

+2Ag +2Ag

+Ag

+Ag D7h ScAg7 D6h ScAg6 Figure 3.



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3

1D4

1P4

2,5 2

1S2

sd-Aos(Sc)

1,5

sd-Aos(Ag) total

1 0,5

0 -4

-3,5

-3

-2,5

-2

-1,5

-1

-0,5

0

Figure 4.


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1S4

3

1P4

2,5

1D4

2 1,5

sd-AO-( Sc)

1

sd-AO-(Ag) Total

0,5 0 -8

-7,5

-7

-6,5

-6

-5,5

-5

-4,5

-4

Figure 5.



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Sc@Ag7

Ag7

Page 20 of 32

Ag6-

Sc

Sc@Ag6-

Sc

3d

3d

1D

1D

1D

1D 4s

4s

1P

1P

1S

1P

1P

1S

1S

1S b)

a)

Figure 6.


Page 21 of 32

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ScAg

ScAg2

ScAg4

ScAg5

ScAg6

ScAg7

ScAg3

ScAg7

Figure 7. 21 ACS Paragon Plus Environment


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D7h Cu73-

D7h ScCu7 a)

D7h Ag73-

D7h ScAg7 b) Figure 8.


Page 23 of 32

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HOMO-HOMO’

HOMO-1,1’

HOMO-2

a)

HOMO-HOMO’

HOMO-1,1’

HOMO-2

b) Figure 9.



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Page 24 of 32

References

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(64) Höltzl,T.; Veldeman, N.; Veszprémi, T.; Lievens, P.; Nguyen, M. T.; Cu6Sc+ and Cu5Sc: Stable, High Symmetry and Aromatic Scandium-doped Coinage Metal Clusters, Chem. Phys. Letts., 2009, 469, 304-307.



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TOC Graphic

D7h Sc@Ag7

Diatropic ring current

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Theoretical Study of Small Scandium-Doped Silver Clusters ScAgn

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