How Partial Atomic Charges and Bonding Orbitals Affect the Reactivity

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A: Kinetics and Dynamics

How Partial Atomic Charges and Bonding Orbitals Affect the Reactivity of Aluminum Clusters with Water? Anthony M.S Pembere, Xianhu Liu, Wei-Hua Ding, and Zhixun Luo J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.7b10635 • Publication Date (Web): 12 Mar 2018 Downloaded from http://pubs.acs.org on March 15, 2018

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The Journal of Physical Chemistry

How Partial Atomic Charges and Bonding Orbitals Affect the Reactivity of Aluminum Clusters with Water? † Anthony M.S Pembereξ, Xianhu Liuξ, Weihua Ding, Zhixun Luo*

State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences; and University of Chinese Academy of Sciences, Beijing 100090, China. *

ξ

†

Correspondence. Email: [email protected] These authors contributed equally to this paper and share the first authorship.

This paper is published to memorise A.W Castleman in the Pennsylvania State University.

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ABSTRACT We present here a further insight on the hydrogen evolution reactions (HER) of aluminum clusters with one and multiple water molecules. Along with natural bond orbital (NBO) and frontier molecular orbital (FMO) analysis, we compared the reactivities of both anionic and neutral Al13, Al12, Al7 and Al6 clusters with water in gas phase. It is found that electron flow interactions between these typical Al clusters and H2O initiate their reactions, allowing varied charge distribution on the cluster. With an emphasis on the typical Al6 cluster, we checked out the reactive intermediates, activated complexes, transition states, bond breaking and stereochemistry for it to react with two and four water molecules respectively. The kinetic- and thermodynamic- allowed reaction pathways are coincident with the experimental observation of Aln(OH)4− being dominant products for Aln− clusters reacting with water. It is illustrated how additional water molecules function as catalysts enabling strengthened HER activity.

1. Introduction Aluminum is known an energy storage material with pretty high gravimetric energy density (31.1 MJ/kg) and the stored chemical potential energy enables large energy-favorable hydrogen evolution reaction (HER) from water (2Al + 6H2O→2Al(OH)3 + 3H2, △H = -861.1KJ).1 For this aim, extensive investigations have been conducted via various means to crush Al into fine powers in order to circumvent the surface oxide (e.g., by doping metal additives like gallium).2-3 In recent years, the HER investigations of water on metal clusters has been an important subject of researchers working in a few interdisciplines.4-11 For example, Castleman, Khanna, and their colleagues12 reported an interesting study on the reactivity of aluminum cluster anions


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with water in a gas flow tube, and they found that Al16−, Al17−, and Al18− result in spontaneous production of H2 from water, while Al12− reacts to form Al12H2O− as Al12− binds water tightly and Al12H2O− bears a stable structure. In comparison, clusters (such as Al11− and Al13−) bearing insurmountable energy-transition states have low reactivity toward water;13 while those (like Al14− and Al16−) having open electronic shells do not support the product observation of water adsorption. Based on these findings, a complementary-active-sites (CAS) mechanism was proposed to rationalize the size-selective reactivity of Al clusters with water. In principle, the initial interaction between a molecule (like water) and metal clusters (like Aln−) is the nucleophilic attack of a H2O molecule on the aluminum surface; the donation of lone-pair electrons from H2O to the LUMO (or LUMO+1 for odd-electron systems) of the Al cluster is required.12 Since the LUMO profile of a metal cluster differs with dependence on its geometric structure, the CAS mechanism is established, not only to reveal that the closing of electron shells is insufficient to explain the observed selective reactivity of Aln− with water, but also to illustrate how adjacent locations on the cluster surface can function as Lewis acid and Lewis base sites enabling size-selective reactivity of metal clusters toward polar molecules.14 In addition to unique geometric and electronic structures, the distinct chemical reactivity of metal clusters could still vary with a few uncertain factors, due to their very high surface-to-volume ratio, likely long-range charge transfer and quantum confinement at reduced sizes, pressure-dependent reactive encounter ratio and sizedependent transition states.15-17 For example, a recent study showed that the reaction of Ag8− and Cu8− clusters with chlorine involves long-range valence electron transfer pertaining to a harpoon mechanism.12 It is also found that the presence of additional OH group molecules gives rise to catalysis for a HER process.18-20 Insights into these



factors in a well-defined manner are a prerequisite for the fundamental understanding of precise chemical reactivities,14 although the reactant interactions are prone to energy minimization which is generally attained when a cluster closes an incomplete electronic shell, either by ionization or forming a covalent/ionic bond.21-22 Comprehensive insights devoted to understand how specific sizes and/or shapes affect the affinities and interactions of metal clusters toward a specific reagent facilitate the efforts to design new materials for specific applications.20-21 More recently a theoretical investigation has been addressed toward the cationic aluminum clusters reacting with water molecules.23 Among several low-energy paths for the HER from water, a rate-determining step was addressed for the H2O dissociation on the cluster. We hereby further expand this study and compare the interaction of both anionic and neutral typical aluminum clusters (typically Al13−, Al13, Al12, Al12−, Al6−, Al6, Al7− and Al7) with one and multiple water molecules using complementary analysis, including electron flow, donor-acceptor natural bond orbital (NBO) overlaps, natural population analysis (NPA) and frontier molecular orbital (FMO) interactions. Along with an emphasis on how partial atomic charges and bonding orbitals affect the reactivity of aluminum clusters with water, we demonstrated a comprehensive insight including reactive intermediates, activated complexes, transition states, bond breaking and stereochemistry.

2.Theoretical and Experimental Methods The aluminum cluster structures were acquired via DFT global optimization referring to previous work.12, 24-25 All geometry optimizations and energy calculations were carried out using the Gaussian 09 software package.26 The CEP-31G*27 basis set (which includes a pseudopotential) is the one employed for the geometry optimization


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and vibrational frequencies with the M06 functional. Frequency calculations were performed at ground states to obtain thermodynamic parameters of zero-point-energy before classifying the stationary points as minima (zero imaginary frequency) or transition states (one imaginary frequency).28 Using the M06/CEP-31G* geometries, single-point energy computations are performed using aug-cc-pVTZ basis set and the B3LYP functional. 29-30 The difference of total electronic and zero point energies (∆E) is used to elucidate the reaction coordinates. For the following discussion, we report on the energies calculated at M06/CEP-31G* // B3LYP/ aug-cc-pVTZ level of theory while the energies calculated at M06/CEP-31G* are also listed in S1. NBO analysis was performed at M06/CEP-31G* level of theory using the related program implemented in the Gaussian 09,31 and the energetic importance was estimated by secondorder perturbation theory. On the other hand, we conducted the reaction of water with Al cluster anions in the gas phase carried by helium gas through a fast-flow tube apparatus, as reported previously.32 The clusters were produced by a customized magnetron-sputtering source which was based on a circular TORUS® magnetron sputter head (Kurt J. Lesker Company).33 Cooling water (~10oC) was used to prevent overheating inside the head and around the vacuum chamber. A magnetron axial mount was designed enabling the magnetron head to move back and forth in the chamber. Ar gas (~2 mTorr, 99.99%, Praxiar, Inc.) was introduced through a modified inner pipeline. Helium gas (~2 Torr, 99.99%, Praxiar, Inc.) was introduced from a small rear flange to carry the clusters through an adjustable iris then into the triple quadrupole mass spectrometer. Quantity of gas flow of water vapor was controlled (~5 sccm) using a medium-flow needle valve (SS-4MG-MH, Swagelok Co.). 20 The flow tube pressure was kept at 0.7 Torr pertaining to several hundred times of collisions.32



3. Results and Discussion Figure 1 shows the optimized structures, charge distribution and frontier orbital distribution of Al13−/Al13, Al12/Al12−, Al6/Al6− and Al7/Al7− clusters. The geometry of Al13/Al13− is icosahedral with one atom in the center and the other 12 atoms located at the icosahedron vertices. The clusters Al12 and Al12− have a similar structure as Al13/Al13− but one of the vertex atoms is missing; thus can be described as two stacked, staggered pentagonal rings with one atom on top and one central atom. This study (with a focus on Al13− versus Al13, Al12 and Al12−) is also motivated by our recent gas-phase reactivity of water and methanol/isopropanol with Al cluster anions in a fast-flow tube apparatus coupled to a quadrupole mass spectrometer,18 whereby methanol was found to exhibit an etching effect towards the Al cluster anions with an exception of Al13−; in comparison, isopropanol tended to bind to the Al clusters. As results, the HOMO-LUMO gaps of Al13−, Al13, Al12 and Al12− are calculated to be 2.59 eV, 2.40 eV, 1.26 eV, and 1.68 eV respectively, which are in good agreement with the previous studies.34-36 Herewith we also provide a comparison of the FMOs relative energies of Al13−, Al13, Al12 and Al12− with water (Figure S1, ESI). From the energy differences between the HOMOs of Al13−/Al13/Al12/Al12− and the LUMO of water, it is expected that, by providing a filled (Al13− and Al12) or a half-filled (Al12− and Al13) orbital, electron flow readily occurs rendering reactions with water. The optimized structures, charge distribution and frontier orbital distribution of Al7/ Al7− and Al6 /Al6− clusters have also been checked out as shown in Figure 1e-h. From the energy differences between the HOMOs of the typical Al clusters and the LUMO of water (Figure S2, ESI), it is expected that, by providing a filled or a half-filled orbital, electron flow occurs rendering uncomplicated reactions with water.


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Figure 1. The optimized structures, charge distribution and frontier orbital distribution of (a) Al13−, (b) Al13, (c) Al12−, (d) Al12, (e) Al6−, (f) Al6, (g) Al7−, and (h) Al7 clusters. Atoms in purple, red, white, color represent Al, O, and H respectively. Bond lengths are in angstroms.



Figure 2. (Left) The reaction coordinates of “Al13− + H2O” (a), “Al13 + H2O” (b), “Al12− + H2O” (c) and “Al12 + H2O” (d). (Right) Second order perturbation theory analysis of Fock matrix in NBO donor–acceptor interactions in Al13−H2O (a), Al13H2O (b), Al12−H2O” (c) and Al12H2O (d). The inserts indicate atom numbers, while BD (bonding orbital), BD* (antibonding orbital), LP (lone pair) and LP* (antibonding lone pair) are molecular orbitals. Bond lengths are in angstroms. Atoms in purple, red, white, color represent Al, O, and H respectively. Energies are in eV.

From the reaction pathway of Al13−, Al13, Al12 and Al12− with a single water molecule (Figure 2), it is revealed that the adsorptions of H2O on Al13−, Al13, Al12− and Al12 are exothermic, where Al12 gives relatively higher adsorption energy. Following the adsorption steps, the first transition states all display the transfer of a hydrogen atom onto the Lewis-base sites of Al13−, Al13, Al12− and Al12 clusters, whereby there are minor single-step energy barriers (0.58 eV, 0.19 eV, 0.10 eV, and 0.42 eV respectively). Also, we have checked the O-H bonds in the transition states, and found that the original O-H bond length (0.98 Å) extends to 1.35 Å for Al13−, 1.31 Å for Al13, 1.30 Å for


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Al12−, and 1.31 Å for Al12, respectively, indicating that H2O can be effectively dissociated with a hydrogen atom transferred to the metal cluster. However, considering the thermalized condition for the gas-phase reaction chamber on the time scale of flow tube, previous studies have found that clusters which have transition-state energies greater than 0.10 eV more than those of the separated reactants exhibit negligible reactivity.12,13,

37

Thus Al13, Al12− and Al12 may readily react with water but, the

reaction of Al13− anion with water could be slow considering the relatively large barrier of the transition state. The finding that Al12 displays particularly high reactivity but Al13− undergoes a high-energy transition state is consistent with the previously published investigations.13 We have attempted to provide further insights why the single atom/electron brings divisive reactivity of aluminum clusters with water. It is known that the reactivity of aluminum clusters with nucleophiles (such as water) varies with the Lewis acidity at different sites of the cluster and frequently depends on the electron flow tendencies on surfaces.12, 38-41 In view of this, we have examined the global electrophilicity indexes which measure the stabilization energy when the system acquires an additional electronic charge from a donor environment (Table S5).42-44 The global electrophilicity 2

index, ω, is generally given by “ω = µ /2η” in terms of the chemical hardness η (η=[IE−EA]/2) and the electronic chemical potential µ (µ ≈ [εH + εL]/2 in terms of the one-electron energies of the frontier molecular orbitals HOMO and LUMO, εH and εL).42-44 As results, the calculated electrophilicity of water (1.39 eV) is found to be higher than that of Al13− (0.17 eV) and Al12− (0.48 eV), but lower than that for Al13 (3.56 eV) and Al12 (3.48 eV). Therefore, within polar interactions, electron flow from water to anionic Al13− and Al12− clusters is favored; on the contrary, electron flow could occur from neutral Al13 and Al12 to water. However, when estimating the total



electron flow between the aluminum clusters and H2O by NPA charge distribution (S3, ESI), we noticed that H2O carries positive charges in the Al13H2O, Al12H2O and Al12−H2O complexes, respectively. Therefore, for Al13/Al12/Al12−, electron flow may still occur from H2O to the cluster. Further, Figure 2 (Right) also presents NBO analysis showing the dominant interactions in the four complexes (the other interactions between donor Lewis-type NBOs and acceptor non-Lewis NBOs are provided in S2, ESI). It is noted that there are very high stabilization energies in the orbital overlap interactions between the Al-Al bonds in Al13−H2O (e.g., LP*Al(7) →RY*Al(1) at 244.7 eV); in comparison, dominant donor-acceptor charge transfer interactions in Al13H2O is BDAl(7) → LP*Al(9) (33.14 eV), and for Al12−H2O and Al12H2O they belong to BD*Al(7) → BD*Al(10) (20.65 eV), and LP*Al(10) →LPAl(12) at 57.64 eV). On the other hand, there are relatively high stabilization energies of the orbital overlap interactions between the O-Al bonds in Al12H2O, e.g., LPO(13) → LPAl(6) (1.24 eV), which is higher than those of the other three complexes. The size- and charge- selective reactivity of aluminum clusters with water has also been studied for aluminum cluster anions (Al6− and Al7−) and neutral (Al6 and Al7). It is worth noting that the electrophilicity power, ω, of water (1.39 eV) is higher than that for the Al7− and Al6− (0.02 eV and 2.0x10-4 eV) but lower than that for Al6 and Al7 (9.72 eV and 4.13 eV). Therefore, the electron flow is expected to take place from water toward Al7− and Al6− clusters as opposed to Al6 and Al7. However, as seen from the NPA charge distribution (ESI), H2O carries positive charges in the Al6H2O and Al7H2O complexes but negative charges in Al7−H2O and Al6−H2O indicating that electron flow still occurs from H2O to Al7 and Al6 clusters, as opposed to Al7− and Al6− anions. Similar to the case of Al12−/Al13/Al12, the complementary Lewis acid and Lewis base sites initiate their interactions and reactivities. The adsorptions of H2O on


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Al7/Al7−/Al6−/Al6 clusters (Figure 3) are endothermic, with Al6 giving relatively higher adsorption energy (-0.75 eV and 0.42 eV at M06/CEP-31G* and B3LYP/aug-ccpVTZ levels of theory respectively). There are also relatively high stabilization energies in the orbital overlap interactions between the Al-Al and the O-Al bonds in Al6H2O, e.g., LP*Al(1) → LP*Al(4) (39.70 eV) and LPO(7) → LP*Al(2) (1.60 eV). In the first transition state (i.e. TS1), there are minor activation energy barriers (0.29 eV and 0.33 eV) for ‘Al6 + H2O’ and ‘Al7 + H2O’, making the reactions to be thermodynamically allowed; whereas, ‘Al7− + H2O’ and ‘Al6− + H2O’ bear larger energy-transition states.

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Figure 3. (Left) The reaction coordinates of (a) “Al6 + H2O”, (b) “Al6 +H2O”, (c) “Al7 + H2O”, (d) − “Al7 +H2O”. (Right) Second order perturbation theory analysis of Fock matrix in NBO donor– − − acceptor interactions in Al6H2O, Al6 H2O, Al7H2O”, and Al7 H2O respectively. BD* (antibonding orbital), LP (lone pair) and LP* (antibonding lone pair) are molecular orbitals. Bond lengths are in angstroms. Atoms in purple, red, white, color represent Al, O, and H respectively. Energies are in eV.



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We have further investigated the reaction pathways of Al6− cluster with two water molecules (Figure 4, upper) and made a comparison with the reaction toward a single water molecule. It is found that the second water molecule prefers co-adsorption on the first water molecule with a relatively large binding energy (-0.75 eV). As opposed to the reaction with a single water molecule, the NPA charge distribution indicates that H2O carries positive charge in the Al6−2H2O complex suggesting electron flow from 2H2O to the Al6− cluster. In the first step, the second water molecule transfers a hydrogen atom to the Al cluster with a barrierless activation energy of 0.03 eV, which contrasts with the insurmountable energy-transition state (0.48 eV) in “Al6− +H2O”. The second step involves the transfer of an OH group to the Al cluster with a singlestep energy barrier at 0.71 eV. In the third step, the hydrogen on the first water molecule is transferred to the cluster with a minor single step barrier of 0.11 eV. Note that, for the final step involving formation of H2, the single-step energy barrier is 0.44 eV, indicating both kinetic- and thermodynamic- favorable reaction pathway.

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Figure 4. The reaction coordinates of “Al6 + 2H2O” (Upper) and “Al6 + 4H2O” (Below). Atoms in purple, red, white, color represent Al, O, and H respectively. Energies are in electron volts


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While the reaction path for the release of the H2 molecule involves adsorption of a second water molecule with an exothermicity of 0.75 eV, the third and fourth water molecules are adsorbed with an exothermicity of 1.87 eV (Figure 4, below) and a barrierless activation of 0.06 eV. The NPA charge distribution also shows that H2O carries positive charge in the Al6−4H2O complex indicating that electron flow occurs from 4H2O to the Al6− cluster. The second step has a small single step energy barrier (0.18 eV) followed by a third step with a barrier of 0.35 eV, and the final step displays a barrier of 0.07 eV. It is important to note that, in our experimental study of Al cluster anions reacting with water in the gas phase carried by helium through a fast-flow tube apparatus (Figure 5), all the Al ion and small Al clusters (Al−, Al2−, Al5−, Al6− and Al7− ) prefer to attach four OH molecules to form Al(OH)4−, Al2(OH)4−, Al5(OH)4−, Al6(OH)4− and Al7(OH)4− species. Among them, Al(OH)4− is the dominant ion cluster based on a very stable molecule Al(OH)3 associated with an additional hydroxy radical. Al(OH)4− displays enhanced intensity likely due to dissociation of larger clusters during the reaction. These –OH group products also coincide well with the DFT calculation results (Figure 4) that demonstrate the catalytic effect of additional water molecules in the reactivity of Al clusters with –OH group chemicals, as revealed in previously reported investigations where water was found to help activate the O-H bond of methanol when reacting with Al cluster anions.20-21, 45 It is worth noting that, a few stable aluminum carbide clusters (e.g., Al3C, and Al4C etc.) also allow to adsorb water molecules and even O-H dissociation, such as Al3C(OH)2, but the Al3,4C clusters may hinder the formation of Al3,4(OH)4−. In addition, the observation of a few reaction products of AlnOx− oxides could be associated with further hydrogen evolution steps as proposed in previously published studies.23, 46



Figure 5. Reaction of water with aluminum clusters. The blue spectrum represents the original Aln− spectrum before the reaction. The red spectrum represents the products after introduction of water.

Conclusion In summary, we have further studied the hydrogen evolution reactions of aluminum clusters with water molecules. Using FMO and NBO analysis, the reactivity of both anionic and neutral Al13, Al12, Al7 and Al6 clusters with water in gas phase is fully addressed. It is revealed that electron flow interactions between these typical Al clusters and H2O initiate their reactions, allowing the varied charge distribution on the cluster to function as steric effect in determining a chemisorption step. Insights into the reactive intermediates, activated complexes, transition states, bond breaking and stereochemistry for the typical Al6 cluster to react with one, two and four water molecules illustrate how additional water molecules function as catalyst, coincident with the experimental observation. Supporting Information


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More details of data and analysis, including adsorption energies, FMO analysis, NPA analysis, NBO analysis, Cartesian coordinates for the optimized structures etc. This material is available free of charge via the Internet at http://pubs.acs.org.

Acknowledgement Z. Luo acknowledges the National Thousand Youth Talents Program (Y3297B1261). This work was also financially supported by Key Research Program of Frontier Sciences (CAS, Grant QYZDB-SSW-SLH024) and the National Natural Science Foundation of China (Grant No. 21722308). A. Pembere acknowledges the support from the CAS/TWAS PHD Presidential Fellowship Initiative for international students.

References 1. 2. 3. 4. 5. 6. 7. 8.

9. 10.

11. 12.

13.

Mench, M. M., Fuel Cell Engines; John Wiley & Sons, 2008. Kravchenko, O.; Semenenko, K. N.; Bulychev, B. M.; Kalmykov, K. B., Activation of Aluminum Metal and Its Reaction with Water, 2005; Vol. 397, p 58-62. Ziebarth, J. T.; Woodall, J. M.; Kramer, R. A.; Choi, G., Liquid Phase-Enabled Reaction of Al– Ga and Al–Ga–in–Sn Alloys with Water. Int. J. Hydrog. Energy. 2011, 36, 5271-5279. Oblath, S. B.; Gole, J. L., Aluminum Hydration in the Vapor Phase. J. Chem. Phys. 1979, 70, 581-582. Jones, M.; Brewster, M., Radiant Emission from the Aluminum-Water Reaction. J. Quant.Spectrosc. Radiat. Transf. 1991, 46, 109-118. McClean, R. E.; Nelson, H.; Campbell, M. L., Kinetics of the Reaction Aluminum (2P0) + Water over an Extended Temperature Range. J. Phys. Chem. 1993, 97, 9673-9676. Hauge, R.; Kauffman, J.; Margrave, J., Infrared Matrix-Isolation Studies of the Interactions and Reactions of Group 3a Metal Atoms with Water. J. Am. Chem. Soc. 1980, 102, 6005-6011. Joly, H.; Howard, J.; Tomietto, M.; Tse, J., Characterization of the Intermediates Formed in the Reaction of Al Atoms with H2O, H2S and H2Se by EPR Spectroscopy. J. Chem. Soc., Faraday Trans.1994, 90, 3145-3151. Brunet, F. o. D.; Joly, H. A., Electron Paramagnetic Resonance Spectroscopic Evidence for the Interaction of HAlOH with Water Molecules. J. Phys. Chem. A 2012, 116, 4267-4273. Álvarez-Barcia, S.; Flores, J., The Oxidation of Al Atoms Embedded in Water Clusters: A Dynamical Study of the Relay (Grotthuss-Like) Mechanism. J. Chem. Phys. 2011, 134, 244305. Álvarez-Barcia, S.; Flores, J. R., How Fast Do Microhydrated Al Clusters React: A Theoretical Study. J. Phys. Chem. C 2011, 115, 24849-24857. Roach, P. J.; Woodward, W. H.; Castleman, A.; Reber, A. C.; Khanna, S. N., Complementary Active Sites Cause Size-Selective Reactivity of Aluminum Cluster Anions with Water. Science 2009, 323, 492-495. Reber, A. C.; Khanna, S. N.; Roach, P. J.; Woodward, W. H.; Castleman Jr, A., Reactivity of Aluminum Cluster Anions with Water: Origins of Reactivity and Mechanisms for H2 Release. J. Phys. Chem. A 2010, 114, 6071-6081.



14. Luo, Z.; Castleman Jr, A.; Khanna, S. N., Reactivity of Metal Clusters. Chem. Rev. (Washington, DC, U. S.) 2016, 116, 14456-14492. 15. Schick, I.; Gehrig, D.; Montigny, M.; Balke, B.; Panthoefer, M.; Henkel, A.; Laquai, F.; Tremel, W., Effect of Charge Transfer in Magnetic-Plasmonic Au@MOx (M = Mn, Fe) Heterodimers on the Kinetics of Nanocrystal Formation. Chem. Mater. 2015, 27, 4877-4884. 16. Wang, J.; Xu, W.; Wu, J.; Yu, G.; Zhou, X.; Xu, S., Plasmon-Enhanced Catalysis of Photo-Induced Charge Transfer from TCNQF4- to TCNQF42-. J. Mater. Chem. C 2014, 2, 2010-2018. 17. Sung, Y.-H.; Frolov, V. D.; Pimenov, S. M.; Wu, J.-J., Investigation of Charge Transfer in Au Nanoparticle-Zno Nanosheet Composite Photocatalysts. Phys. Chem. Chem. Phys. 2012, 14, 14492-14494. 18. Álvarez-Barcia, S.; Flores, J. R., How H2 Can Be Formed by the Interaction of Al Atoms with a Few Water Molecules: A Theoretical Study. Chem. Phys. 2010, 374, 131-137. 19. Álvarez-Barcia, S.; Flores, J., The Interaction of Al Atoms with Water Molecules: A Theoretical Study. J. Chem. Phys. 2009, 131, 174307. 20. Luo, Z.; Smith, J. C.; Woodward, W. H.; Castleman Jr, A., Reactivity of Aluminum Clusters with Water and Alcohols: Competition and Catalysis? J. Phys. Chem. Lett. 2012, 3, 3818-3821. 21. Luo, Z.; Castleman, A. W., Special and General Superatoms. Acc. Chem. Res., 2014, 47, 29312940. 22. Bergeron, D. E.; Castleman, A. W.; Morisato, T.; Khanna, S. N., Formation of Al13I-: Evidence for the Superhalogen Character of Al13. Science 2004, 304, 84-87. 23. Moc, J., Theoretical Investigation of the Reaction Paths of the Aluminum Cluster Cation with Water Molecule in the Gas Phase: A Facile Route for Dihydrogen Release. J. Phys. Chem. A 2015, 119, 8683-91. 24. Ahlrichs, R.; Elliott, S. D., Clusters of Aluminium, a Density Functional Study. Phys. Chem. Chem. Phys. 1999, 1, 13-21. 25. Aguado, A.; López, J. M., Structures and Stabilities of AlN+, AlN, and AlN−(N= 13-34) Clusters. J. Chem. Phys. 2009, 130, 064704. 26. Gaussian 09, Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, Jr., J. A.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, N. J.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G.A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, Ö.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian, Inc., Wallingford CT, 2009. 27. Zhao, Y.; Truhlar, D. G., The M06 Suite of Density Functionals for Main Group Thermochemistry, Thermochemical Kinetics, Noncovalent Interactions, Excited States, and Transition Elements: Two New Functionals and Systematic Testing of Four M06-Class Functionals and 12 Other Functionals. Theor. Chem. Acc. 2008, 120, 215-241. 28. Hou, H.; Deng, L.; Li, J.; Wang, B., A Systematic Computational Study on the Reactions of HO2 with RO2: The HO2 + CH3O2(CD3O2) and HO2 + CH2FO2 Reactions. J. Phys. Chem. A 2005, 109, 9299-9309. 29. Perdew, J. P.; Burke, K.; Ernzerhof, M., Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865. 30. Dunning Jr, T. H., Gaussian Basis Sets for Use in Correlated Molecular Calculations. I. The Atoms Boron through Neon and Hydrogen. J. Chem. Phys. 1989, 90, 1007-1023. 31. Glendening, E.; Reed, A.; Carpenter, J.; Weinhold, F., Nbo Version 3.1, Tci. University of Wisconsin, Madison 1998, 65. 32. Luo, Z.; Grover, C. J.; Reber, A. C.; Khanna, S. N.; Castleman Jr, A., Probing the Magic Numbers of Aluminum–Magnesium Cluster Anions and Their Reactivity toward Oxygen. J. Am. Chem. Soc. 2013, 135, 4307-4313. 33. Luo, Z. X.; Woodward, W. H.; Smith, J. C.; Castleman, A. W., Jr., Growth Kinetics of Al Clusters in the Gas Phase Produced by a Magnetron-Sputtering Source. Int. J. Mass Spectrosc. 2012, 309, 176-181. 34. Leuchtner, R. E.; Harms, A. C.; Castleman, A. W., Thermal Metal Cluster Anion Reactions Behavior of Aluminum Clusters with Oxygen. J. Chem. Phys. 1989, 91, 2753-2754.


Page 16 of 18

Page 17 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


35. Reber, A. C.; Khanna, S. N.; Roach, P. J.; Woodward, W. H.; Castleman, A. W., Spin Accommodation and Reactivity of Aluminum Based Clusters with O2. J. Am. Chem. Soc. 2007, 129, 16098-16101. 36. Khanna, S. N.; Jena, P., Atomic Clusters - Building-Blocks for a Class of Solids. Phys. Rev. B 1995, 51, 13705-13716. 37. Abreu, M. B.; Powell, C.; Reber, A. C.; Khanna, S. N., Ligand-Induced Active Sites: Reactivity of Iodine-Protected Aluminum Superatoms with Methanol. J. Am. Chem. Soc. 2012, 134, 2050720512. 38. Cox, D.; Trevor, D.; Whetten, R.; Kaldor, A., Aluminum Clusters: Ionization Thresholds and Reactivity toward Deuterium, Water, Oxygen, Methanol, Methane, and Carbon Monoxide. J. Phys. Chem.1988, 92, 421-429. 39. Lippa, T.; Lyapustina, S.; Xu, S.-J.; Thomas, O.; Bowen, K., Magic Numbers in AlN+(H2O)1 Cluster Cations. Chem. Phys. Lett. 1999, 305, 75-78. 40. Sun, Q.; Wang, Q.; Yu, J.; Briere, T.; Kawazoe, Y., Structure and Interaction Mechanism in the Magic Al13+H2O Cluster. Phys. Rev. A 2001, 64, 053203. 41. Guevara-García, A.; Martínez, A.; Ortiz, J., Addition of Water, Methanol, and Ammonia to Al3O3− Clusters: Reaction Products, Transition States, and Electron Detachment Energies. J. Chem. Phys 2005, 122, 214309. 42. Domingo, L. R.; Pérez, P.; Sáez, J. A., Understanding the Local Reactivity in Polar Organic Reactions through Electrophilic and Nucleophilic Parr Functions. RSC Adv. 2013, 3, 1486-1494. 43. Domingo, L. R.; Pérez, P., A Quantum Chemical Topological Analysis of the C–C Bond Formation in Organic Reactions Involving Cationic Species. Phys. Chem. Chem. Phys., 2014, 16, 14108-14115. 44. Domingo, L. R.; Sáez, J. A., Understanding the Mechanism of Polar Diels–Alder Reactions. Org. & Biomol. Chem., 2009, 7, 3576-3583. 45. Álvarez-Barcia, S.; Rivero-González, U.; Flores, J. s. R., Reaction Mechanisms and Dynamics of H2 Generation in Microhydrated Al Clusters: The Role of Oxo–Hydroxyl and Dioxo Structures in the Al17–·(H2o)2 System. J. Phys. Chem. C 2015, 119, 21928-21942. 46. Arakawa, M.; Kohara, K.; Ito, T.; Terasaki, A., Size-Dependent Reactivity of Aluminum Cluster Cations toward Water Molecules. Eur. Phys. J. D, 2013, 67, 80.



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How Partial Atomic Charges and Bonding Orbitals Affect the Reactivity

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