Formation, Structures, and Reactivities of Niobium Oxide Cluster Ions

Deng, Haiteng; Kerns, K. P.; Castleman, A. W.

doi:10.1021/jp953100d

Cited by 77 publications

(100 citation statements)

References 32 publications

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“…26,30 With regard to reactivity, Castleman and co-workers found that the cluster size and the degree of coordinative saturation affect the reactivity of the cationic clusters with n-butane and that cationic clusters with a somewhat metal-rich character can abstract an oxygen atom from acetone. 25,31,32 As for anionic clusters, Jackson and co-workers have reported that Nb x O y − compounds undergo different reactions with methanol and ethanol depending on the oxidation state of Nb and the number of Nb−O double bonds. 29 In our previous study, we showed that the combination of coverage-dependent 2PPE measurements and DFT calculations is a highly effective tool for understanding electron transfer at the cluster−support interface for a series of metal oxide nanoclusters on Cu(111).…”

Section: O 10mentioning

confidence: 99%

Influence of Cluster–Support Interactions on Reactivity of Size-Selected Nb_xO_y Clusters

Nakayama

Xue

et al. 2015

J. Phys. Chem. C

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Size-selected niobium oxide nanoclusters (Nb 3 O 5 , Nb 3 O 7 , Nb 4 O 7 , and Nb 4 O 10 ) were deposited at room temperature onto a Cu(111) surface and a thin film of Cu 2 O on Cu(111), and their interfacial electronic interactions and reactivity toward water dissociation were examined. These clusters were specifically chosen to elucidate the effects of the oxidation state of the metal centers; Nb 3 O 5 and Nb 4 O 7 are the reduced counterparts of Nb 3 O 7 and Nb 4 O 10 , respectively. From twophoton photoemission spectroscopy (2PPE) measurements, we found that the work function increases upon cluster adsorption in all cases, indicating a negative interfacial dipole moment with the positive end pointing into the surface. The amount of increase was greater for the clusters with more metal centers and higher oxidation state. Further analysis with DFT calculations of the clusters on Cu (111) indicated that the reduced clusters donate electrons to the substrate, indicating that the intrinsic cluster dipole moment makes a larger contribution to the overall interfacial dipole moment than charge transfer. X-ray photoelectron spectroscopy (XPS) measurements showed that the Nb atoms of Nb 3 O 7 and Nb 4 O 10 are primarily Nb 5+ on Cu(111), while for the reduced Nb 3 O 5 and Nb 4 O 7 clusters, a mixture of oxidation states was observed on Cu(111). Temperature-programmed desorption (TPD) experiments with D 2 O showed that water dissociation occurred on all systems except for the oxidized Nb 3 O 7 and Nb 4 O 10 clusters on the Cu 2 O film. A comparison of our XPS and TPD results suggests that Nb 5+ cations associated with NbO terminal groups act as Lewis acid sites which are key for water binding and subsequent dissociation. TPD measurements of 2-propanol dehydration also show that the clusters active toward water dissociation are indeed acidic. DFT calculations of water dissociation on Nb 3 O 7 support our TPD results, but the use of bulk Cu 2 O(111) as a model for the Cu 2 O film merits future scrutiny in terms of interfacial charge transfer. The combination of our experimental and theoretical results suggests that both Lewis acidity and metal reducibility are important for water dissociation.

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Section: O 10mentioning

confidence: 99%

Influence of Cluster–Support Interactions on Reactivity of Size-Selected Nb_xO_y Clusters

Nakayama

Xue

et al. 2015

J. Phys. Chem. C

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“…[24][25][26] We investigated the structure and bonding of early transition metal oxide clusters using a combined photoelectron spectroscopy (PES) and theoretical approach with the aim of discovering specific structures or clusters that may mimic a catalytic site. [27,28] Our experiment was carried out with a magnetic-bottle PES apparatus with a laser vaporization cluster source.…”

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confidence: 99%

Observation of d‐Orbital Aromaticity

et al. 2005

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Aromaticity is one of the most important concepts in chemistry and refers to planar cyclic hydrocarbon molecules that exhibit delocalized p-bonds and unusual stability, such as benzene. This concept has been extended to metal-substituted organic molecules, [1,2] as well as main group organometallic complexes. [3][4][5][6] The recent discovery of aromaticity in allmetal clusters, for instance [Al 4 ] 2À in [MAl 4 ] À (M = Cu, Li, Na), [7] has led to a flurry of research activities [8][9][10][11][12][13][14][15][16] and predictions of new aromatic metal clusters, [17][18][19][20][21][22][23] among which is a class of interesting cyclic species containing Cu. [20,23] While main group clusters can give rise to s-and paromaticity, transition-metal-containing clusters can exhibit d-orbital aromaticity or, more interestingly, d-aromaticity due to d bonding interactions. However, d-orbital aromaticity requires significant d-d bonding interactions. Unlike valent s or p orbitals, d orbitals are spatially more contracted, and their tendency to participate in chemical bonding depends strongly on the position of the transition metals in the periodic table and their coordination environments. The predicted aromaticity in the cyclic Cu-containing species, [20,23] for example, has not been verified experimentally. More promisingly, d-orbital aromaticity is expected to be found in early or 4d/5d transition metal systems, where strong d-d interactions are known. Here, we report experimental and theoretical evidence of d-orbital aromaticity in two early 4d and 5d transition metal oxide clusters, namely [M 3 O 9 ] À and [M 3 O 9 ] 2À (M = W, Mo).

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“…Numerous groups have applied CID to investigate a wide variety of cluster systems (e.g. metal [10], metal oxide [11], carbon [12] and silicon [13] clusters). Particularly, for Ti x O + y clusters, Yu and Freas [1] have investigated the CID of mass selected Ti x O + y complexes produced by fast-atom-bombardment on Ti-foils and TiO 2 -powders.…”

Section: Introductionmentioning

confidence: 99%

Collision-induced dissociation studies on gas-phase titanium oxide cluster cations

2012

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Titanium oxide cluster cations Ti x O + y are produced in a molecular beam by combining laser ablation of titanium with the supersonic expansion of oxygen into vacuum. The size distribution of the clusters produced is analyzed by time-of-flight reflectron mass spectrometry. The stable clusters appearing in the mass spectrum can be described by the general formula (TiO) m (TiO 2 ) n (O 2 ) + k (with m, n = 0, 1, 2, . . . and k = 0, 1). Additionally, collisioninduced dissociation studies of mass selected clusters colliding with Kr atoms in a gas cell have been performed. The results show that the clusters lose neutral O 2 , TiO and/or (TiO 2 ) n units, and the remaining charged fragments are those with the lowest ionization potentials. From these results the fragmentation cross section of the selected clusters is obtained.

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Formation, Structures, and Reactivities of Niobium Oxide Cluster Ions

Cited by 77 publications

References 32 publications

Influence of Cluster–Support Interactions on Reactivity of Size-Selected Nb_xO_y Clusters

Influence of Cluster–Support Interactions on Reactivity of Size-Selected Nb_xO_y Clusters

Observation of d‐Orbital Aromaticity

Collision-induced dissociation studies on gas-phase titanium oxide cluster cations

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Formation, Structures, and Reactivities of Niobium Oxide Cluster Ions

Cited by 77 publications

References 32 publications

Influence of Cluster–Support Interactions on Reactivity of Size-Selected NbxOy Clusters

Influence of Cluster–Support Interactions on Reactivity of Size-Selected NbxOy Clusters

Observation of d‐Orbital Aromaticity

Collision-induced dissociation studies on gas-phase titanium oxide cluster cations

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Influence of Cluster–Support Interactions on Reactivity of Size-Selected Nb_xO_y Clusters

Influence of Cluster–Support Interactions on Reactivity of Size-Selected Nb_xO_y Clusters