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The thermal reaction of diatomic gold boride cation AuB+ with methane has been studied by using state-of-the-art mass spectrometry in conjunction with density functional theory calculations. The AuB+ ion can activate a methane molecule to produce exclusively the free hydrogen atom, an important intermediate in hydrocarbon transformation. This result is different from the reactivity of AuC+ and CuB+ counterparts with methane in previous studies. The AuC+ cation mainly transforms methane into ethylene. The CuB+ reaction system principally generates the free hydrogen atoms, but it also gives rise a portion of ethylene-like product H2B−CH2. The B atom of AuB+ is the active site to activate methane. The strong relativistic effect on gold plays an important role for the product selectivity. The mechanistic insights obtained from this study provide guidance for rational design of active sites with high product selectivity toward methane activation. [ABSTRACT FROM AUTHOR]

Abstract: The single copper atom doped clusters CuAl4O7–9− can catalyze CO oxidation by O2. The CuAl4O7–9− clusters are the first group of experimentally identified noble‐metal free single atom catalysts for such a prototypical reaction. The reactions were characterized by mass spectrometry and density functional theory calculations. The CuAl4O9CO− is much more reactive than CuAl4O9− in the reaction with CO to generate CO2. One adsorbed CO is crucial to stabilize Cu of CuAl4O9− around +I oxidation state and promote the oxidation of another CO. The widely emphasized correlation between the catalytic reactivity of CO oxidation and Cu oxidation state can be understood at the strictly molecular level. The remarkable difference between Cu catalysis and noble‐metal catalysis was discussed. [ABSTRACT FROM AUTHOR]

Abstract: The single copper atom doped clusters CuAl4O7–9− can catalyze CO oxidation by O2. The CuAl4O7–9− clusters are the first group of experimentally identified noble‐metal free single atom catalysts for such a prototypical reaction. The reactions were characterized by mass spectrometry and density functional theory calculations. The CuAl4O9CO− is much more reactive than CuAl4O9− in the reaction with CO to generate CO2. One adsorbed CO is crucial to stabilize Cu of CuAl4O9− around +I oxidation state and promote the oxidation of another CO. The widely emphasized correlation between the catalytic reactivity of CO oxidation and Cu oxidation state can be understood at the strictly molecular level. The remarkable difference between Cu catalysis and noble‐metal catalysis was discussed. [ABSTRACT FROM AUTHOR]

Investigations of the intrinsic properties of gas-phase transition metal nitride (TMN) ions represent one approach to gain a fundamental understanding of the active sites of TMN catalysts, the activities and electronic structures of which are known to be comparable to those of noble metal catalysts. Herein, we investigate the structures and reactivities of the triatomic anions HNbN− by means of mass spectrometry and photoelectron imaging spectroscopy, in conjunction with density functional theory calculations. The HNbN− anions are capable of activating CH4 and C2H6 through oxidative addition, exhibiting similar reactivities to free Pt atoms. The similar electronic structures of HNbN− and Pt, especially the active orbitals, are responsible for this resemblance. Compared to the inert NbN−, the coordination of the H atom in HNbN− is indispensable. New insights into how to replace noble metals with TMNs may be derived from this combined experimental/computational study. [ABSTRACT FROM AUTHOR]

The study of chemical reactions between gold-containing heteronuclear oxide clusters and small molecules can provide molecular level mechanisms to understand the excellent activity of gold supported by metal oxides. While the promotion role of gold in alkane transformation was identified in the clusters with atomic oxygen radicals (O−.), the role of gold in the systems without O−. is not clear. By employing mass spectrometry and quantum chemistry calculations, the reactivity of Au2VO3+ clusters with closed-shell electronic structures toward ethane was explored. Both the dehydrogenation and ethene elimination channels were identified. It is gold rather than oxygen species initiating the C−H activation. The Au−Au dimer formed during the reactions plays important roles in ethane transformation. The reactivity comparison between Au2VO3+ and bare Au2+ demonstrates that Au2VO3+ not only retains the property of bare Au2+ that transforming ethane to dihydrogen, but also exhibits new functions in converting ethane to ethene, which reveals the importance of the composite system. This study provides a further understanding of the reactivity of metal oxide supported gold in alkane activation and transformation. [ABSTRACT FROM AUTHOR]

Investigations on the reactivity of atomic clusters have led to the identification of the elementary steps involved in catalytic CO oxidation, a prototypical reaction in heterogeneous catalysis. The atomic oxygen species O.− and O2− bonded to early-transition-metal oxide clusters have been shown to oxidize CO. This study reports that when an Au2 dimer is incorporated within the cluster, the molecular oxygen species O22− bonded to vanadium can be activated to oxidize CO under thermal collision conditions. The gold dimer was doped into Au2VO4− cluster ions which then reacted with CO in an ion-trap reactor to produce Au2VO3− and then Au2VO2−. The dynamic nature of gold in terms of electron storage and release promotes CO oxidation and OO bond reduction. The oxidation of CO by atomic clusters in this study parallels similar behavior reported for the oxidation of CO by supported gold catalysts. [ABSTRACT FROM AUTHOR]

In addition to generation of a methyl radical, formation of a formaldehyde molecule was observed in the thermal reaction of methane with AuNbO3+ heteronuclear oxide cluster cations. The clusters were prepared by laser ablation and mass-selected to react with CH4 in an ion-trap reactor under thermal collision conditions. The reaction was studied by mass spectrometry and DFT calculations. The latter indicated that the gold atom promotes formaldehyde formation through transformation of an AuO bond into an AuNb bond during the reaction. [ABSTRACT FROM AUTHOR]

Identification and mechanistic study of thermal methane conversion mediated by gas-phase species is important for finding potentially useful routes for direct methane transformation under mild conditions. Negatively charged oxide species are usually inert with methane. This work reports an unexpected result that the bi-metallic oxide cluster anions PtAl2O4− can transform methane into a stable organic compound, formaldehyde, with high selectivity. The clusters are prepared by laser ablation and reacted with CH4 in an ion trap reactor. The reaction is characterized by mass spectrometry and density functional theory calculations. It is found that platinum rather than oxygen activates CH4 at the beginning of the reaction. The Al2O4− moiety serves as the support of Pt atom and plays important roles in the late stage of the reaction. A new mechanism for selective methane conversion is provided and new insights into the surface chemistry of single Pt atoms may be obtained from this study. [ABSTRACT FROM AUTHOR]

Graphical abstract Sulfur‒oxygen exchange channels were observed in the reactions of oxygen atoms with CH 3 COS−, C 6 H 5 COS− and C 6 H 5 S− anions. Sulfur‒containing anions will be depleted in astrochemical environments where oxygen atoms are abundant. Highlights • None of the studied anions react with nitrogen atoms. • A sulfur‒oxygen exchange channel was observed in the reactions of oxygen atoms with CH 3 COS−, C 6 H 5 COS− and C 6 H 5 S− anions. • A sulfur abstraction channel was observed in the reactions of oxygen atoms with SCN− and −SCH 2 COOH anions. • The rate constants for reactions between sulfur‒containing anions and oxygen atoms are found to be higher than for the related oxygen‒containing anions. Abstract Sulfur‒containing anions are expected to exist in molecular clouds and other astrochemical environments due to the relative abundance of sulfur and the predicted stability of the anions. Furthermore, nitrogen and oxygen atoms are of high abundance in the interstellar medium. Therefore, reactions of nitrogen and oxygen atoms with small sulfur‒containing anions, SCN−, CH 3 COS−, C 6 H 5 COS−, −SCH 2 COOH, C 6 H 5 S−, and related oxygen‒containing anions, OCN−, CH 3 COO−, C 6 H 5 COO−, HOCH 2 COO−, C 6 H 5 O−, have been studied both experimentally and computationally. The experimental results show that none of the studied anions react with nitrogen atoms. All of the studied anions with the exception of OCN− react with oxygen atoms, and the reaction channels are more diverse than those for the previously studied reactions with hydrogen atoms. In addition to the associative electron detachment (AED) channel, some ionic products such as CN−, CH 3 COO−, C 6 H 5 COO−, HO− and S− were observed. A sulfur‒oxygen exchange channel was observed in the reactions of oxygen atoms with CH 3 COS−, C 6 H 5 COS− and C 6 H 5 S− anions. A sulfur abstraction channel was observed in the reactions of oxygen atoms with SCN− and −SCH 2 COOH anions. The rate constants for reactions between sulfur‒containing anions and oxygen atoms are found to be generally higher than for the related oxygen‒containing anions. Density functional theory calculations were conducted to provide insight into the experimental results. [ABSTRACT FROM AUTHOR]

Abstract: The single copper atom doped clusters CuAl4O7–9− can catalyze CO oxidation by O2. The CuAl4O7–9− clusters are the first group of experimentally identified noble‐metal free single atom catalysts for such a prototypical reaction. The reactions were characterized by mass spectrometry and density functional theory calculations. The CuAl4O9CO− is much more reactive than CuAl4O9− in the reaction with CO to generate CO2. One adsorbed CO is crucial to stabilize Cu of CuAl4O9− around +I oxidation state and promote the oxidation of another CO. The widely emphasized correlation between the catalytic reactivity of CO oxidation and Cu oxidation state can be understood at the strictly molecular level. The remarkable difference between Cu catalysis and noble‐metal catalysis was discussed. [ABSTRACT FROM AUTHOR]

Dinitrogen (N2) activation by metal hydride species is of fundamental interest and practical importance while the role of hydrogen in N2 activation is not well studied. Herein, the structures of Co3Dn− (n = 0–4) clusters and their reactions with N2 have been studied by using a combined experimental and computational approach. The mass spectrometry experiments identified that the Co3Dn− (n = 2–4) clusters could adsorb N2 while the Co3Dn− (n = 0 and 1) clusters were inert. The photoelectron imaging spectroscopy indicated that the electron detachment energies of Co3D2–4− are smaller than those of Co3D0,1−, which characterized that it is easier to transfer electrons from Co3D2–4− than from Co3D0,1− to activate N2. The density functional theory calculations generally supported the experimental observations. Further analysis revealed that the H atoms in the Co3Hn− (n = 2–4) clusters generally result in higher energies of the Co 3d orbitals in comparison with the Co3Hn− (n = 0 and 1) systems. By forming chemical bonds with H atoms, the Co atoms of Co3H2–4− are less negatively charged with respect to the naked Co3− system, which leads to higher N2 binding energies of Co3H2–4N2− than that of Co3N2−. [ABSTRACT FROM AUTHOR]

Abstract: The single copper atom doped clusters CuAl4O7–9− can catalyze CO oxidation by O2. The CuAl4O7–9− clusters are the first group of experimentally identified noble‐metal free single atom catalysts for such a prototypical reaction. The reactions were characterized by mass spectrometry and density functional theory calculations. The CuAl4O9CO− is much more reactive than CuAl4O9− in the reaction with CO to generate CO2. One adsorbed CO is crucial to stabilize Cu of CuAl4O9− around +I oxidation state and promote the oxidation of another CO. The widely emphasized correlation between the catalytic reactivity of CO oxidation and Cu oxidation state can be understood at the strictly molecular level. The remarkable difference between Cu catalysis and noble‐metal catalysis was discussed. [ABSTRACT FROM AUTHOR]

To develop proper ionization methods for alkanes, the reactivity of bare or ligated transition metal ions toward alkanes has attracted increasing interests. In this study, the reactions of the gold cations with linear alkanes from ethane up to nonane (CnH2n+2, n = 2-9) under mild conditions have been characterized by mass spectrometry and density functional theory calculations. When reacting with Au+, small alkanes (n = 2-6) were confirmed to follow specific reaction channels of dehydrogenation for ethane and hydride transfer for others to generate product ions characteristic of the original alkanes, which indicates that Au+ can act as a reagent ion to ionize alkanes from ethane to n-hexane. Strong dependence of the chain length of alkanes was observed for the rate constants and reaction efficiencies. Extensive fragmentation took place for larger alkanes (n > 6). Theoretical results show that the fragmentation induced by the hydride transfer occurs after the release of AuH. Moreover, the fragmentation of n-heptane was successfully avoided when the reaction took place in a high-pressure reactor. This implies that Au+ is a potential reagent ion to ionize linear and even the branched alkanes. [ABSTRACT FROM AUTHOR]

Laser-ablation-generated cerium-vanadium oxide cluster cations CeVO 4 + were mass-selected by applying a quadrupole mass filter, and reacted with propylene in a linear ion trap reactor at ambient conditions. Time-of-flight mass spectrometry and density functional theory calculations were used to characterize the cluster reactions. The CeVO 4 + cluster has a closed-shell electronic structure, and is reactive toward propylene leading to the formation of CeVO 3 C 3 H 4 + /H 2 O and CeVO 4 C 3 H 6 + . The computed results indicate that this reaction involves the occurrence of spin conversions (singlet → triplet), and a new mechanism of dehydrogenation of alkenes, which is different from the reported ones, was proposed. Compared with another closed-shell cluster V 3 O 7 + , possessing the similar mass with CeVO 4 + , the heteronuclear oxide cluster cations show higher reactivity toward propylene. The computational results are in good agreement with the experimental observations. This work provides insights into nature of active sites and reaction mechanisms in related condensed-phase systems at a molecular level. [ABSTRACT FROM AUTHOR]

[Display omitted] • Known Ta 9−13 clusters isomers are confirmed. • New Ta 9−13 clusters isomers are found. • The deep neural network method better explores larger-sized clusters. Global optimization is performed on Ta n (n = 9–13) clusters by deep neural network (DNN) combined with density functional theory (DFT) method. All of the previously known cluster isomers within relative energy of 1.5 eV (except 2.0 eV for Ta 10 ) are confirmed by our calculations. Moreover, new cluster isomers within relative energy of 1.5 eV (except 2.0 eV for Ta 10 ) are reported. More complicated high-dimensional PESs that correspond to larger-sized clusters can be better explored by the DNN method because more new low-lying energy isomer configurations are found with increasing cluster size. [ABSTRACT FROM AUTHOR]

Abstract: A time of flight mass spectrometer coupled with a laser ablation/supersonic expansion cluster source is used to study the formation and distribution of cationic iron and cobalt oxide clusters. Although the distributions of iron oxide clusters (, q =0, ±1) have been extensively reported in literature, new and very interesting distribution of Fe m O n + clusters is observed in this study. Under saturated O2 growth conditions, the smallest (leading) cluster in m =2k +1 (k =2−14) cluster series is with stoichiometry of Fe2k O3k FeO+, which is perfect (iron atoms are perfectly oxidized) in terms of average oxidation states of iron (Fe3+) and oxygen (O2−) atoms. For m =2k (k =2–15) cluster series, the leading cluster is either Fe2k O3k + (the least over-oxidized) or Fe2k O3k−1 + (the least under-oxidized). Density functional theory (DFT) calculations indicate that these leading clusters are with unexpected structures although their appearance in the mass spectra is predictable. These clusters may serve as good models for predicting or interpreting novel properties of Fe2O3 nano-materials. The distribution of the cobalt oxide clusters (Co m O n +) under saturated O2 growth conditions is complex and very different from that of Fe m O n +. A very interesting result for cobalt species is that two clusters Co11O13 + and Co12O13 + are missing in the cluster distribution although their oxygen-neighbor clusters Co11O12,14 + and Co12O12,14 + are generated. This suggests relatively high stability for Co11O12 + and Co12O12 + clusters. The DFT calculations predict that Co12O12 cluster are with tower or cage structure rather than the compact NaCl-like arrangement that is found for bulk CoO. [Copyright &y& Elsevier]