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Ferromagnets constructed from nanometals of atomic precision are important for innovative advances in information storage, energy conversion, and spintronic microdevices. Considerable success has been achieved in designing molecular magnets, which, however, are challenging in preparation and may suffer from drawbacks on the incompatibility of high stability and strong ferromagnetism. Utilizing a state-of-the-art self-developed mass spectrometer and a homemade laser vaporization source, we have achieved a highly efficient preparation of pure iron clusters, and here, we report the finding of a strongly ferromagnetic metal–carbon cluster, Fe12C12–, simply by reacting the Fen–clusters with acetylene in proper conditions. The unique stability of this ferromagnetic Fe12C12–cluster is rooted in a plumb-bob structure pertaining to Jahn–Teller distortion. We classify Fe12C12–as a new member of metallo-carbohedrenes and elucidate its structural stability mechanism as well as its soft-landing deposition and magnetization measurements, providing promise for the exploration of potential applications.

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 NH3under the same reaction condition. Theoretical calculations elucidate why Agn+clusters show different reactivities with these inorganic hydrides. NH3shows 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.

Well-resolved Nbn–clusters are produced and reacted with ethene and propene via a downstream flow tube reactor. Interestingly, the Nbn–clusters readily react with ethene and propene to form dehydrogenation products; however, Nb15–shows up in the mass spectra with prominent mass abundance indicating its inertness to react with olefins. For this cluster, we conduct photoelectron velocity map imaging (VMI) experiments and verify the stability of Nb15–within a highly symmetrical rhombic dodecahedron structure. Theoretical studies show that the stability of the Nb15–cluster is correlated with its superatomic nature pertaining to both geometric and electronic shell closures. Notably, the superatomic 1s orbital is dominated by the 5s electron of the central Nb atom, while the other superatomic orbitals are contributed by s–d hybridization, especially a remarkable contribution of s–dz2hybridization. Apart from the closed shells, the highly symmetric geometry of Nb15–is associated with a regular polyhedral structure directed by all rhombus facets, embodying a magic number for body-centered dodecahedra, indicative of enhanced stability as a double magic cluster free of olefin adsorption.

Exploring metal cluster reactivity with alkyl halides enables to understand the related chemical mechanism of metal surfaces in terms of active sites. Here we report a study of Agn+(n= 1–27) clusters reacting with iodomethane by a flow tube apparatus in tandem with a customized triple quadrupole mass spectrometer. Strong even/odd alternation of the Agn+is observed in their reactions with CH3I, where silver clusters with even-number, Ag2n+, find favorable products of Ag2nI1,3+series, while the Ag2n−1+clusters form Ag2n−1I2,4+products. Interestingly, Ag9+shows up with prominent mass abundance but allows for the formation of Ag9I2+, which finds an echo with the formation of Ag10I3+. We illustrate the enhanced stability of Ag9I2+and Ag10I3+by showing their significantly enlarged highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps and balanced charge distribution compared with the bare metal clusters, respectively. Also elucidated, is the superatomic nature of these bare and iodinated silver clusters, especially Ag9I2+which mimics the rare-gas compound XeF2. This study expands a vivid example of special and general superatoms, and enriches the general knowledge on how a ligand stabilizes a metal cluster.

We report an in-depth study of the adsorption and reaction of NO with cationic Nbn+(n= 1–20) clusters under thermalized conditions in a laminar flow tube reactor in tandem with a customized triple quadrupole mass spectrometer (FT-TQMS). It is found that the small-sized Nbn+clusters (2 ≤ n≤ 7) readily react with NO giving rise to dominant fragmentation products pertaining to the loss of a stable diatomic molecule NbO or NbN. In contrast, the reaction products of larger-sized clusters (n≥ 10) proceed through diverse channels, including NO adsorption, N2/N2O release, and even NO2formation. These experimental observations provided the incentive for us to dig deep into the reaction mechanism with the help of DFT calculations. In contrast to the NO-donation coordination in transition metal complexes, here the cationic Nbn+clusters exhibit dominant electronic donation in initiating the reactions with NO molecules. We fully demonstrated the reaction rate constants, compared the reaction energy diagram of typical Nbn+clusters, and unveiled the distinct interaction mechanism of niobium clusters available for NO activation and conversion.

Metal nanoclusters are promising nanomaterials with unique properties, but only a few ones with specific numbers of metal atoms can be obtained and studied up to now. In this study, we establish a new paradigm of in-situgeneration and global study of metal nanoclusters with different sizes, constitutions, and charge states, including both accurate constitution characterization and global activity profiling. The complex mixtures of metal nanoclusters are produced by employing single-pulsed 193-nm laser dissociation of monolayer-protected cluster (MPC) precursors within a high-resolution mass spectrometry (HRMS). More than 400 types of bare gold nanoclusters including novel multiply charged (2+ and 3+), S-/P-doped, and silver alloy ones can be efficiently generated and accurately characterized. A distinct size (1 to 142 atoms)- and charge (1+ to 3+)-hierarchy reactivity is clearly observed for the first time. This global cluster study might greatly promote the developments and applications of novel metal nanoclusters.

Methane dehydrogenation and C–C coupling under mild conditions are very important but challenging in chemistry. Utilizing a customized time of flight mass spectrometer combined with a magnetron sputtering (MagS) cluster source, here, we have conducted a study on the reactions of methane with small silver and copper clusters simply by introducing methane in argon as the working gas for sputtering. Interestingly, a series of [M(CnH2n)]+(M= Cu and Ag; n= 2–12) clusters were observed, indicating high-efficiency methane dehydrogenation in such a plasma-assisted chamber system. Density functional theory calculations find the lowest energy structures of the [M(CnH2n)]+series pertaining to olefins indicative of both C–H bond activation of methane and C–C bond coupling. We analyzed the interactions involved in the [Cu(CnH2n)]+and [Ag(CnH2n)]+(n= 1–6) clusters and demonstrated the reaction coordinates for the “Cu++ CH4” and “Ag++ CH4.” It is illustrated that the presence of a second methane molecule enables us to reduce the necessary energy of dehydrogenation, which concurs with the experimental observation of an absence of the metal carbine products Cu+CH2and Ag+CH2, which are short-lived. Also, it is elucidated that the higher-lying excitation states of Cu+and Ag+ions enable more favorable dehydrogenation process and C═C bond formation, shedding light on the plasma assistance of the essence.

We have prepared well-resolved Nbn+(n = 1–10) clusters and report here an in-depth study on the essentially different reactivity with N2and O2, by utilizing a multiple-ion laminar flow tube reactor in tandem with a customized triple quadrupole mass spectrometer (MIFT-TQMS). As results, the Nbn+clusters are found to readily react with N2and form adsorption products NbnN2m+; in contrast, the reactions with O2give rise to NbnO1−4+products, and the odd-oxygen products indicate O-O bond dissociation, as well as increased mass abundance of NbO+pertaining to oxygen-etching reactions. We illustrate how N2prefers a physical adsorption on Nbn+clusters with an end-on orientation for all the products, and allow for size-selective Nbn+clusters to act as electron donor or acceptor in forming NbnN2m+. In contrast to these nitrides, the dioxides NbnO2+display much larger binding energies, with O2always as an electron acceptor, corresponding to superoxide or peroxide states in the initial reactions. Density-of-states and orbital analyses show that the interactions between Nbn+and O2are dominated by strong π-backdonation indicative of incidental electron transfer; whereas weak π-backdonation and simultaneous σdonation interactions exist in NbnN2+. Further, reaction dynamics analysis illustrates the different interactions for N2and O2in approaching the Nbn+clusters, showing the energy diagrams for N2adsorption and O-O bond dissociation in producing odd-oxygen products. Fragment analyses with orbital correlation and donor-acceptor charge transfer are also performed, giving rise to full insights into the reactivities and interactions of such transition metal clusters with typical diatomic molecules.

Advances in cluster science have enabled the preparation of atomically precise metal clusters with one to a hundred atoms under controllable expansion conditions. After introducing typical gas-phase cluster preparation and reaction apparatuses, this work summarized recent progress in preparing pure metal clusters of single-atom resolution, including neutral and ionic ones, with typical examples of Al, V, Nb, Fe, Co, Ni, Rh, Pt, Ag, Cu, and Pb. With the development of soft-landing deposition technology, the size-selective pure metal clusters with strict atomic precision and predictive property will benefit nanomanufacturing down to atomic and near-atomic scales. This work serves as a modest motivation to stimulate the interest of scientists focusing on interdisciplinary subjects.

We report a joint experimental and theoretical study on the reactions of cobalt clusters (Con±/0) with nitrogen using the customized reflection time-of-flight mass spectrometer combined with a 177.3 nm deep-ultraviolet laser. Comparing to the behaviors of neutral Con(n= 2–30) and anionic Con–clusters (n= 7–53) which are relatively inert in reacting with nitrogen in the fast-flow tube, Con+clusters readily react with nitrogen resulting in adducts of one or multiple N2except Co6+which stands firm in the reaction with nitrogen. Detailed quantum chemistry calculations, including the energetics, electron occupancy, and orbital analysis, well-explained the reasonable reactivity of Con+clusters with nitrogen and unveiled the open-shell superatomic stability of Co6+within a highly symmetric (D3d) structure. The D3dCo6+bears an electron configuration of a half-filled superatomic 1P orbital (i.e., 1S21P3||1D0), a large α-highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap, symmetric multicenter bonds, and reasonable electron delocalization pertaining to metallic aromaticity. Topology analysis by atom-in-molecule illustrates the interactions between Con+and N2corresponding to covalent bonds, but the Co–N interactions in cationic Co2+N2and Co6+N2clusters are apparently weaker than those in the other systems. In addition, we identify a superatomic complex Co5N6+which exhibits similar frontier orbitals as the naked Co5+cluster, but the alpha HOMO–LUMO gap is nearly double-magnified, which is consistent with the high-abundance peak of Co5N6+in the experimental observation. The enhanced stability of such a ligand-coordinated superatomic complex Co5N6+, along with the superatom Co6+with aromaticity, sheds light on special and general superatoms.

A customized reflection time-of-flight (Re-TOF) mass spectrometer combined with a 177 nm deep-ultraviolet laser has enabled us to observe well-resolved cobalt clusters Con±/0and perform a comprehensive study of their reactivity with ammonia (NH3). The anions Con–are found to be inert, the neutrals allow the adsorption of multiple NH3molecules, while the cationic Con+clusters readily react with NH3giving rise to dehydrogenation. However, incidental dehydrogenation of NH3on Con+is only observed for n≥ 3. The dramatic charge- and size-dependent reactivities of Con±/0clusters with NH3are studied by the density functional theory (DFT)-calculation results of energetics, density of states, orbital interactions, and reaction dynamics. We illustrate the dehydrogenation from two NH3molecules, where a significantly reduced transition-state energy barrier is found pertaining to the dimolecular co-catalysis effect. The reactivity of Co3+with NH3is illustrated showing effective catalysis for N–H dissociation to produce hydrogen applicable for designing ammonia fuel cells.

Utilizing the homemade reflection time-of-flight mass spectrometer (Re-TOFMS), here we report a comprehensive study of the reactivity of aluminum clusters Aln±,0with molecular benzene in the gas-phase flow tube reactor. During the reactions with benzene, Aln+clusters were found to be relatively more reactive than Aln0/–, and interestingly, the Al13+cluster exhibited more reaction product than its neighboring Aln+clusters. With an emphasis on Al13±,0clusters, we have performed an in-depth study utilizing DFT calculations to unravel the diverse reactivity of aluminum clusters with benzene. It is revealed that the Al13+Bz cluster has a short Al–C distance and high binding energy, as well as an enlarged HOMO–LUMO gap in comparison with that of Al13+. This contrasts with Al130/–and Al15+, of which the HOMO–LUMO gaps are reduced when the cluster binds with a benzene molecule. Further, the cluster−π interactions between aluminum clusters and benzene are fully demonstrated via topological analysis, natural bonding orbital (NBO) analysis, and noncovalent interaction plots based on independent gradient model (IGM). The unique gyro-like structure of Al13+and cluster−π interaction induce uneven redistribution of charges on the 13- atoms of Al13+, enabling a tight Al–C bond with strong electrostatic attraction and orbital interactions, which largely differs from the weak orbital overlap and electrostatic repulsion between benzene molecule and Al130/–clusters.

Utilizing a magnetron-sputtering (MagS) source in tandem with a multiple-ion laminar flow tube (MIFT) reactor and a customized triple quadrupole mass spectrometer (TQMS), we have prepared clean Pbn+(n= 1–13) clusters and measured their reactivity with iodomethane under high carrier gas pressures. Strong size dependences are found for the reactivity of these cationic Pbn+clusters with CH3I. For the Pbn+with n≤ 4, iodinated clusters PbnI+were found to be the dominant products, in strong contrast to n> 4 where no such products were seen. Quantum chemical studies show that with an increasing number of Pb atoms, the Pb–Pb interatomic interactions become stronger compared with the Pb–I bonding in PbnI+clusters. Furthermore, the reactions of Pb1–4+with CH3I have fairly small transition state energy barriers, in contrast to those for Pbn>4+clusters which have magnitudes that will prevent reactions under the ambient conditions.

Synergistic interactions within metal clusters help to improve the catalytic activity of individual metal atoms and contribute to advance the understanding of mechanisms in multisite catalysis. Herein, the MoS2-supported Fe2cluster was chosen as the catalyst for nitrogen reduction reaction (NRR) to produce ammonia. First-principles calculations reveal that the Fe2/MoS2exhibits high catalytic activity for electrochemical NRR and sheds light on the enzymatic mechanism which bears a low overpotential of 0.21 V. Compared with a single Fe atom on MoS2, the presence of a vicinal Fe atom (i.e., Fe2/MoS2) enables side-on adsorption of N2, which is propitious to effective N–N bond activation. Whereas the Fe3/MoS2catalyst, simply with one more Fe atom involved, reduces electron depletion among Fe atoms and hence represses N2adsorption. The origin of reasonable NRR catalysis of Fe2/MoS2is further unveiled by natural charge population and projected crystal orbital Hamilton population (pCOHP) analyses. This investigation provides an effective strategy for designing active catalysts with low cost and multisite synergy catalysis.

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.

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 Al6clusters 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 Al6cluster, 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.

Tailoring materials with prescribed properties and regular structures is a critical and challenging research topic. Early transition metals were found to form supermagic M8C12metallocarbohedrenes (Met-Cars); however, stable metal carbides are not limited to this common stoichiometry. Utilizing self-developed deep-ultraviolet laser ionization mass spectrometry, here, we report a strategy to generate new titanium carbides by reacting pure Tinclusters with acetylene. Interestingly, two products corresponding to Ti17C2and Ti19C10exhibit superior abundances in addition to the Ti8C12Met-Cars. Using global-minimum search, the structures of Ti17C2and Ti19C10are determined to be an ellipsoidal D4dand a rod-shaped D5hgeometry, respectively, both with carbon-capped Ti4C moieties and superatomic features. We illustrate the electronic structures and bonding nature in these carbon-doped superatoms concerning their enhanced stability and local aromaticity, shedding light on a new class of metal-carbide nanomaterials with atomic precision.

Iodomethane and bromomethane (CH3I/CH3Br) are common chemicals, but their chemistry on nanometals is not fully understood. Here, we analyze the reactivity of Rhn+(n= 3–30) clusters with halomethanes and unveil the spin effect and concentration dependence in the C–H and C–X bond activation. It is found that the reactions under halomethane-rich conditions differ from those under metal-rich conditions. Both CH3I and CH3Br undergo similar dehydrogenation on the Rhn+clusters in the presence of small quantity reactants; however, different reactions are observed in the presence of sufficient CH3I/CH3Br, showing dominant Rh(CH3Br)x+(x= 1–4) products but a series of RhnCxHyIz+species (x= 1–4, y= 1–12, and z= 1–5) pertaining to H2, HI, or CH4removal. Density functional theory calculations reveal that the dehydrogenation and demethanation of CH3Br are relatively less exothermic and will be deactivated by sufficient gas collisions if helium cooling takes away energy immediately; instead, the successive adsorption of CH3Br gives rise to a series of Rh(CH3Br)x+species with accidental C–Br bond dissociation.

Metal clusters including those supported on graphene-based materials have attracted extensive research interest in the past decade allowing dissection of the interfaces, stability, electronic properties, and catalytic activities at an atomically precise scale. Here, we have synthesized glutathione-protected Ag6clusters via a facile green reaction route, transferred onto graphene oxide (GO) and exploit as catalyst for cyclohexane oxidation under ambient conditions. High selectivity and high yields to produce cyclohexanone are attained with tert-butyl hydroperoxide (TBHP) as the oxidant in the oxygen-flowing atmosphere. Based on density functional theory calculations, it is demonstrated that both TBHP and oxygen interact with the GO-supported Ag6clusters, giving rise to the peroxide structure and hence facilitating the catalytic oxidation of cyclohexane. It is interestingly found that the hydrogen-added hydroperoxyl (−OOH) brings forth largely decreased activation barrier for the O–O bond dissociation. The O–O dissociated intermediate then reacts with cyclohexane to form cyclohexanol, followed by successive oxidative dehydrogenation to produce cyclohexanone. This finding verifies the enhanced catalysis of TBHP and O2for the conversion of cyclohexane to cyclohexanone and helps to develop heterogeneous catalysts of metal clusters for efficient C–H activation.

The reactivity of cationic aluminum clusters with oxygen is studied via a customized time-of-flight mass spectrometer. Unlike the etching effect for anionic aluminum clusters exposed to oxygen, here, the cationic Aln+clusters react and produce a range of small AlnOm+clusters. Relatively large-mass abundances are found for Al3O4+, Al4O5+, and Al5O7+at lower O2reactivity, while at higher O2concentration, oxygen addition leads to Al2O7+, Al3O6,8–10+, and Al4O7,9+, showing relatively high abundance, and Al5O7+remains as a stable species dominating the Al5Om+distribution. To understand these results, we have investigated the structures and stabilities of the AlnOm+clusters. First-principles theoretical investigations reveal the structures, highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gaps, fragmentation energies, ionization energies, and Hirshfield charge of the AlnOm+clusters (2 ≤ n≤ 7; 0 ≤ m≤ 10). Energetically, Al3O4+, Al4O5+, and Al5O7+are calculated to be most stable with high fragmentation energies; however, they still allow for the chemisorption of additional O2with large binding energies leading to clusters with higher O/Al ratios. The stability of the species is consistent with Al possessing three valence electrons, while O typically accepts two, leading to the expectation that Al3O4+, Al5O7+, and Al7O10+are reasonably stable. In addition to this, Al3O+, Al5O3+, and Al7O5+are found to exhibit large HOMO–LUMO gaps associated with the different oxidation states of Al. The oxygen-rich species such as Al2O7+, Al3O10+, and Al4O9+all display superoxide structures providing further insights into the oxidation of aluminum clusters.

Utilizing a customized multiple-ion laminar flow tube reactor in tandem with a triple quadrupole mass spectrometer, we report a study of the gas-phase reactivity of Agn+clusters with acetylene. Well-resolved Agn+clusters (n= 1–20) are produced by a self-designed magnetron sputtering source (MagS); however, on their reactions with acetylene under sufficient collisional conditions, only Ag7+[C2H2] is produced with a reasonable intensity. DFT calculations reveal that Agn+clusters do not form strong Ag–C bonds with C2H2and Ag7+[C2H2] bears larger binding energy than the other Agn+[C2H2] although within similar cluster−π interactions. Besides gas-phase reaction rate estimation, the relatively large noncovalent cluster−π interaction in Ag7+[C2H2] is fully demonstrated via topological analysis and natural bonding orbital analysis. Also, we illustrate both thermodynamically and kinetically favored channels in producing the Ag7+[C2H2]. This study helps in understanding metal-involved noncovalent bonds and how such weak interactions are able to tune the material function and biological activity.

Understanding the interactions between water and Fe-based clusters is necessary to unravel the micromechanics of the surface hydrophilic property and the corrosion process of iron-related materials. Herein, a theoretical study is conducted of water adsorption and dissociation on icosahedral Fe13and Fe12X (X = Ti, V, Cr, Mn, Co, Ni) clusters. It is found that the doping atoms have significant influence on the geometric structures, magnetic moments, and electronic states of Fe12X clusters. The center-doped clusters X@Fe12show higher stability than the shell-doped X–Fe12; Ni@Fe12exhibits lower activation energy for the dissociation of H2O than all the others; Ti@Fe12strikes a weak bonding energy and high activation energy for water dissociation. Also, a water dimer finds a decreased energy barrier for O–H dissociation, and the electronic states and metal–water interactions can be altered by the support effect. This information is helpful to those working on water chemistry, anticorrosion wading devices, and high-standard potable water utilization.

We report a finding of feasible oxidant-free dehydrogenation of glycerol over small Au clusters, with a low-energy barrier of transition state initiated by hydrogen atom transfer from methene, which differs from the general reaction mechanism based on hydroxyl.

Utilizing a facile top-down synthetic procedure, here we report the finding of a chlorine-passivated Al37superatom cluster. It is demonstrated that the presence of electrophilic groups, severing as protecting ligands, alters the valence electron count of the metallic core and stabilize the as-prepared aluminum clusters especially when even-numbered chlorine atoms are located at equilibrium positions. Following the discussion regarding their reasonable stabilities, we illustrate the feasible reaction pathways in forming such chlorine-passivated Al37superatom clusters which bear delocalized superatomic orbitals with five valence 3P5electrons shifting to the chlorine ligands indicative of a closed electron shell 2F14of the metal core. The successful synthesis of such chlorine-protected aluminum clusters evidences the compatibility of general theory of cluster chemistry in both gas phase and wet chemistry. Such simple-ligand-protected aluminum clusters exhibit reverse-saturated-absorption (RSA) nonlinear optical property pertaining to electronic transitions within the discrete energy states of cluster materials.

The application of low-fragmentation mass spectrometry to identify chemicals has been recognized to be of particular importance in chemistry, biomedicine, and materials science. Utilizing a customized all-solid-state picosecond-pulsed deep-ultraviolet (DUV) laser, here we present new advances into photoionization mass spectrometry. The DUV laser ionization mass spectrometry (DUV-LIMS) results in very clean spectra pertaining to minimized structure relaxation and fragmentation under the ultrafast ionization process. Typical DUV-LIMS applications are illustrated not only for small organic molecules but also for long-chain unsaturated hydrocarbons and clusters of benzene. The unique advantages of DUV-LIMS enable us to detect and analyze confusing organic compound mixtures, indicating promising applications. DUV-LIMS is also found to be applicable in the identification of phenylenediamine isomers. An in-depth analysis of reaction dynamics is provided showing how hydrogen-atom-transfer (HAT) initiates the distinguishable photodissociation of phenylenediamines under near-resonant excitation. In particular, ortho-phenylenediamine (OPD) finds a remarkable dehydrogenation product with comparable intensity to the molecular ion peak, which is associated with the quantum tunnelling tautomers, providing new subjects for studying intramolecular noncovalent interactions.

We have synthesized two copper nanoclusters (NCs) with a protection of the same ligand diphenylphosphino-2-pyridine (C17H14NP, dppy for short), formulated as Cu4(dppy)4Cl2and Cu21(dppy)10, respectively. The former one bears a distorted tetrahedron Cu4core with its six edges fully protected by chlorine and dppy ligands, while the latter presents a symmetric Cu21core on which ten dppy molecules function as monolayer protection via well-organized monodentate or bidentate coordination. Interestingly, the Cu4(dppy)4Cl2cluster exhibits a strong yellow emission at ∼577 nm, while Cu21(dppy)10displays dual emissions in purple (∼368 nm) and green (∼516 nm) regions respectively. In combination with TD-DFT calculations, we demonstrate the origin of altered emissions and unique stability of the two copper nanoclusters pertaining to the ligand coordination and metallic superatomic states.

Weak intermolecular interactions in aniline-pyrrole dimer clusters have been studied by the dispersion-corrected density functional theory (DFT) calculations. Two distinct types of hydrogen bonds are demonstrated with optimized geometric structures and largest interaction energy moduli. Comprehensive spectroscopic analysis is also addressed revealing the orientation-dependent interactions by noting the altered red-shifts of the infrared and Raman activities. Then we employ natural bond orbital (NBO) analysis and atom in molecules (AIM) theory to have determined the origin and relative energetic contributions of the weak interactions in these systems. NBO and AIM calculations confirm the V-shaped dimer cluster is dominated by N−H···N and C−H···π hydrogen bonds, while the J-aggregated isomer is stabilized by N−H···π, n→π* and weak π···π* stacking interactions. The noncovalent interactions are also demonstrated via energy decomposition analysis associated with electrostatic and dispersion contributions.

Investigations on conformational transition of a small organic molecule are important to understand the conformation principles in chemistry and biology. We employed a low-temperature surface-enhanced Raman spectroscopy (LT-SERS) technique to probe the conformational changes of 2,2′-bipyridyl (22BPY) on Ag nanoparticles at the presence of external fields. An electrochemical system was used to provide an electrostatic field, and a special magnet was designed to supply a magneto-static field. High-quality and distinguishable SERS spectra of 22BPY were obtained at the different environments, which show fingerprint labels for correlative conformations of the 22BPY. The conformational transition of 22BPY is implemented via its adsorption on the Ag nanoparticles by triggers of the external electric field and magnetic field.

Small aluminum clusters (<30 atoms) have been the subject of extensive study, demonstrating markedly different properties as even a single atom is added or removed. Successfully depositing and characterizing mass-selected clusters are the next steps in producing precise surfaces or cluster-assembled materials that demonstrate properties that differ from those of bulk materials. This proves to be difficult due to the reactivity of these all-metal clusters and their susceptibility to agglomerate in bulk form. In the present study, we have successfully deposited Al17−onto self-assembled monolayers using reactivity previously characterized in the gas phase.

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The activation of molecular oxygen is an important step in metal-catalyzed oxidation reactions and a hot subject for the research of gas-phase metal clusters. It is known that the Ag and Au clusters readily react with O2when they have open shell electronic structures. Distinct from this, here we observed Cun−(n = 7−20) clusters of both open and closed shells possess high reactivity with O2with few exceptions. In a combination with ab initio calculations, we demonstrate that the activation of O2on the even- and odd-sized Cun−clusters follows the single and double electron transfer models, respectively. Such phenomenon of metal clusters with different basicity to activate oxygen is enabled by the leveling effect of spin accommodation. The activity of Cun−clusters is correlated to the HOMO level, and for the close-shell clusters is also governed by the vertical spin excitation energy (VSE). In encountering the attack of dioxygen, the activity of the copper cluster anions not only depends on their basicity to donate electrons, but also closely associated with the cluster sizes. Small copper clusters Cun−(n = 7−13) can dissociate O2spontaneously, while large clusters require extra energies and display close relationship between the reaction rates and electronic vertical detachment energies (VDE). Our work illuminates a novel reaction mechanism between Cun−clusters and O2, which sheds light in manipulating the activity and stability of coinage clusters by controlling the spin and charge states.

Exploring stable clusters to understand structural evolution from atoms to macroscopic matter and to construct new materials is interesting yet challenging in chemistry. Utilizing our newly developed deep-ultraviolet laser ionization mass spectrometry technique, here we observe the reactions of neutral cobalt clusters with oxygen and find a very stable cluster species of Co13O8that dominates the mass distribution in the presence of a large flow rate of oxygen gas. The results of global-minimum structural search reveal a unique cubic structure and distinctive stability of the neutral Co13O8cluster that forms a new class of metal oxides that we named as ‘metalloxocubes’. Thermodynamics and kinetics calculations illustrate the structural evolution from icosahedral Co13to the metalloxocube Co13O8with decreased energy, enhanced stability and aromaticity. This class of neutral oxygen-passivated metal clusters may be an ideal candidate for genetic materials because of the cubic nature of the building blocks and the stability due to cubic aromaticity.

Cyclotrimerization of acetylene to benzene has attracted significant interest, but the role of geometric and electronic effects on catalytic chemistry remains unclear. To fully elucidate the mechanism of catalytic acetylene-to-benzene conversion, we have performed a gas-phase reaction study of the Fen+, Con+, and Nin+(n= 1–16) clusters with acetylene utilizing a customized mass spectrometer. It is found that their reactions with acetylene are initiated by C2H2molecular adsorption and allow for dominant dehydrogenation with the relatively low partial pressure of the acetylene gas. However, at high acetylene concentrations, the cyclotrimerization in Mn++ 3C2H2(M = Fe, Co, Ni) becomes the dominant reaction channel. We demonstrate theoretically the favorable thermodynamics and reaction dynamics leading to the formation of the M+(C6H6) products. The results are discussed in terms of a cluster-catalyzed multimolecule synergistic effect and the cation−π interactions.