Theoretical Study of Tetrahydrofuran-Stabilized Al₁₃ Superatom Cluster

We present here an in-depth study upon the interaction between a neutral cluster Al13 and a typical ligand tetrahydrofuran (THF) via density functional theory (DFT) calculation. It is found that electron delocalization over the framework of Al13 and THF facilitates ligand-to-Al13 charge transfer leading to enhanced stability for the superhalogen cluster Al13. Further study on the stabilization of Al13(THF)n cluster complexes with n = 1–8 reveals that the adsorption of more THF ligands gradually enhances the total binding energy and the total electronic charge transfer from the ligand to Al13. The bonding nature and stabilization of Al13(THF)n cluster are then demonstrated by rationalizing the interactions between superatomic and molecular orbitals of Al13 and THF, respectively

What Determines If a Ligand Undergoes Coordination or Catalytic Activation on a Metal Cluster?

We report a joint experimental and theoretical study on the reactivity of Agn+ clusters with H2S, D2O, and NH3. Complete dehydrogenation products are observed for Agn+ reacting with H2S, but no dehydrogenation products are found for D2O or NH3 under the same reaction condition. Theoretical calculations elucidate why Agn+ clusters show different reactivities with these inorganic hydrides. NH3 shows strong coordination with Agn+, but the dehydrogenation reactions are unfavorable; in contrast, the fragile H–S bonds and stable AgnS+ products facilitate the hydrogen evolution of H2S on Agn+. We fully analyzed the metal–ligand interactions of Agn+ clusters with three molecules and illustrated the reaction dynamics and charge-transfer interactions and altered the superatomic states during the formation of cluster sulfides. We expect this study to benefit the design of stable environmentally friendly desulfurization catalysts and also the understanding of the mechanism on ligand-protected metal clusters in wet chemistry

Acetone Dimer Hydrogenation under Vacuum Ultraviolet: An Intracluster Trimolecular Dissociation Mechanism

Hydrogenation of organic chemicals is one of the most frequent things that people take for granted in mass spectroscopy; however, it could provide important information on spontaneous or stimulated hydrogen transfer in initiating chemical reactions and in determining the product selectivity and conversion efficiency. Here, we present a study of hydrogenation of acetone via vacuum ultraviolet laser ionization mass spectrometry (VUV-LIMS) and density functional theory (DFT) calculations. It is interestingly found that acetone dimer readily captures a hydrogen to form (C3H6O)2H+ in the presence of alcohols, shedding light on the intracluster hydrogen atom transfer via a trimolecular mechanism. This is well consistent with the DFT calculation results of energetics and reaction kinetics. It is worth noting that, although the hydrogen bond interaction of O–H···O is stronger than that of C–H···O, the hydrogen atom transfer (HAT) tends to proceed from the methyl group of the alcohols to acetone. We fully demonstrate the intracluster HAT reactivity of such a simple system and provide new insights into hydrogen bond interactions and molecular cluster chemistry

Quantum Tunneling Tautomer of <i>N</i>,<i>N</i>‑Dimethyl‑<i>p</i>‑toluidine Dehydrogenates Identified by Deep-UV Laser Ionization Mass Spectroscopy

Utilizing customized deep-ultraviolet laser ionization mass spectroscopy, here we report a finding of remarkable dehydrogenation product of N,N-dimethyl-p-toluidine (DMT). The DMT dehydrogenates find comparable mass abundance with the DMT molecule ions showing decent stability at the loss of one electron and one H atom from the DMT molecule. First-principles calculation reveals that the dehydrogenation most readily occurs at the N-connected methyl group. Furthermore, at the removal of a hydrogen atom, a neighboring hydrogen atom on the other methyl come close and interact with the dehydrogenated methylene group, pertaining to C–H···C weak interactions which give rises to a resonant structure (C···H–C) on a basis of hydrogen atom quantum tunneling effect. The quantum tunneling tautomer of DMT dehydrogenates displays reversible donor–acceptor charge-transfer interactions as demonstrated by natural bonding orbital analysis and vibrational spectroscopy. It is worth noting that the novel dehydrogenation product was also observed for another small organic molecule o-phenylenediamine, which bears two neighboring amino groups and the subsequent dehydrogenation product pertains to resonant structures of N–H···N and N···H–N. The deep ultraviolet laser not only produces fragmentation-free mass spectra for such small organic molecules but also tailors the interesting quantum tunneling tautomer from such specific molecules

An Open-Shell Superatom Cluster Ta₁₀^– with Enhanced Stability by United d–d π Bonds and d‑Orbital Superatomic States

We carried out a comprehensive study on the gas-phase reactions of Tan– (n = 5–27) with nitrogen using a customized reflection time-of-flight mass spectrometer coupled with a velocity map imaging apparatus (Re-TOFMS-VMI). Among the studied tantalum clusters, Ta10– exhibits prominent mass abundance indicative of its unique inertness. DFT calculation results revealed a D4d bipyramidal prolate structure of the most stable Ta10–, which was verified by photoelectron spectroscopy experiments. The calculations also unveiled that Ta10– has the largest HOMO–LUMO gap and second-order difference of binding energy among the studied clusters. This is associated with its well-organized superatomic orbitals, which consist of both 6s and 5d orbitals of tantalum atoms, allowing for splitting of superatomic 1D and 2P orbitals and an enlarged gap between the singly occupied molecular orbital (SOMO) and unoccupied β counterpart, which brings forth stabilization energy pertaining to Jahn–Teller distortion. Also, the SOMO exhibits a united d–d π orbital pattern that embraces the central Ta8– moiety

An Open-Shell Superatom Cluster Ta₁₀^– with Enhanced Stability by United d–d π Bonds and d‑Orbital Superatomic States

We carried out a comprehensive study on the gas-phase reactions of Tan– (n = 5–27) with nitrogen using a customized reflection time-of-flight mass spectrometer coupled with a velocity map imaging apparatus (Re-TOFMS-VMI). Among the studied tantalum clusters, Ta10– exhibits prominent mass abundance indicative of its unique inertness. DFT calculation results revealed a D4d bipyramidal prolate structure of the most stable Ta10–, which was verified by photoelectron spectroscopy experiments. The calculations also unveiled that Ta10– has the largest HOMO–LUMO gap and second-order difference of binding energy among the studied clusters. This is associated with its well-organized superatomic orbitals, which consist of both 6s and 5d orbitals of tantalum atoms, allowing for splitting of superatomic 1D and 2P orbitals and an enlarged gap between the singly occupied molecular orbital (SOMO) and unoccupied β counterpart, which brings forth stabilization energy pertaining to Jahn–Teller distortion. Also, the SOMO exhibits a united d–d π orbital pattern that embraces the central Ta8– moiety

On the Nature of Three-Atom Metal Cluster Catalysis for N₂ Reduction to Ammonia

Catalytic N2 activation and reduction for ammonia synthesis has been subject of intense research interest. Cluster-modified catalysts have been proposed as promising candidates for nitrogen activation due to the featured active sites and maximized synergistic effect. However, the nature of metal clusters itself has not been fully unveiled. Herein, we report a systematic investigation of N2 activation and reduction on three-atom metal clusters (M3) of all the 20 transition metals in the third and fourth periods of elements. We evaluate the catalysis of these M3 clusters by taking into consideration three critical processes, namely, N2 dissociation, hydrogenation, and NH3 desorption. The TMI series of the M3 clusters (Group 3B–5B metals) are found to support N2 dissociation spontaneously, in contrast to the TMII and TMIII clusters (i.e., Groups 6B–8B and 1B–2B). Based on the three criteria, Y3, Sc3, Zr3, and Nb3 are identified as eligible candidates for ammonia synthesis. These clusters show preferable hollow-site N2 adsorption and strong orbital hybridization, with electronic backdonation from the metal d orbitals to both π* and π/σ orbitals of N2. Further studies on ammonia synthesis have been conducted by applying Y3 and Nb3 clusters supported on graphene (Y3/G and Nb3/G), illustrating superior activity and potential application of such M3 clusters. This work validates the three-atom cluster catalysis and guides the design of efficient catalysts for N2 fixation