Infrared Spectroscopic Characterization of Early 4d Transition Metal Carbene Cations, ZrCH and NbCH.

IR multiple-photon dissociation (IRMPD) action spectroscopy is combined with quantum chemical calculations to examine the [M,C,2H] species for the early 4d metals, M = Zr and Nb. These ions were formed by reacting laser ablated M ions with cyclopropane (-CH) in a molecular beam apparatus. Both IRMPD spectra exhibit one major band near 700 cm and a second weaker band at about twice that wavenumber, more evident when irradiated in focus.

Mixed Cluster Ions of Magnesium and C.

Magnesium clusters exhibit a pronounced nonmetal-to-metal transition, and the neutral dimer is exceptionally weakly bound. In the present study, we formed pristine Mg ( = 1-100, = 1-3) clusters and mixed (C)Mg clusters ( = 1-7, = 1, 2) upon electron irradiation of neutral helium nanodroplets doped with magnesium or a combination of C and magnesium. The mass spectra obtained for pristine magnesium cluster ions exhibit anomalies, consistent with previous reports in the literature.

Pentagon, Hexagon, or Bridge? Identifying the Location of a Single Vanadium Cation on Buckminsterfullerene Surface.

Buckminsterfullerene C has received extensive research interest since its discovery. In addition to its interesting intrinsic properties of exceptional stability and electron-accepting ability, the broad chemical tunability by decoration or substitution on the C-fullerene surface makes it a fascinating molecule. However, to date, there is uncertainty about the binding location of such decorations on the C surface, even for a single adsorbed metal atom.

Tuning the degree of CO activation by carbon doping Cu ( = 3-10) clusters: an IR spectroscopic study.

Copper clusters on carbide surfaces have shown a high catalytic activity towards methanol formation. To understand the interaction between CO and the catalytically active sites during this process and the role that carbon atoms could play in this, they are modeled by copper clusters, with carbon atoms incorporated. The formed clusters CuC ( = 3-10, = 1-2) are reacted with CO and investigated by IR multiple-photon dissociation (IR-MPD) spectroscopy to probe the degree of CO activation.

Water quality monitoring based on chemometric analysis of high-resolution phytoplankton data measured with flow cytometry.

River water is an important source of Dutch drinking water. For this reason, continuous monitoring of river water quality is needed. However, comprehensive chemical analyses with high-resolution gas chromatography [GC]-mass spectrometry [MS]/liquid chromatography [LC]-MS are quite tedious and time consuming; this makes them poorly fit for routine water quality monitoring and, therefore, many pollution events are missed.

NO Bond Cleavage on Gas-Phase Ir Clusters Investigated by Infrared Multiple Photon Dissociation Spectroscopy.

The adsorption forms of NO on Ir ( = 3-6) clusters were investigated using infrared multiple photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) calculations. Spectral features indicative both for molecular NO adsorption (the NO stretching vibration in the 1800-1900 cm range) and for dissociative NO adsorption (the terminal Ir-O vibration around 940 cm) were observed, elucidating the co-existence of molecular and dissociative adsorption of NO. In all calculated structures for molecular adsorption, NO is adsorbed via the N atom on on-top sites.

Bonding Nature between Noble Gases and Small Gold Clusters.

Noble gases are usually seen as utterly inert, likewise gold, which is typically conceived as the noblest of all metals. While one may expect that noble gases bind to gold via dispersion interactions only, strong bonds can be formed between noble gas atoms and small gold clusters. We combine mass spectrometry, infrared spectroscopy, and density functional theory calculations to address the bonding nature between Au ( ≤ 4) clusters and Ar, Kr, and Xe.

IR Spectroscopic Characterization of Methane Adsorption on Copper Clusters Cu ( = 2-4).

The interaction of CH with cationic copper clusters has been studied with infrared-multiple photon dissociation (IRMPD) spectroscopy. Cu ( = 2-4) formed by laser ablation were reacted with CH. The formed complexes were irradiated with the IR light of the free-electron laser for intracavity experiments (FELICE), and the fragments were mass-analyzed with a reflectron time-of-flight mass spectrometer.

Efficient Formation of Size-Selected Clusters upon Pickup of Dopants into Multiply Charged Helium Droplets.

Properties of clusters often depend critically on the exact number of atomic or molecular building blocks, however, most methods of cluster formation lead to a broad, size distribution and cluster intensity anomalies that are often designated as magic numbers. Here we present a novel approach of breeding size-selected clusters via pickup of dopants into multiply charged helium nanodroplets. The size and charge state of the initially undoped droplets and the vapor pressure of the dopant in the pickup region, determines the size of the dopant cluster ions that are extracted from the host droplets, via evaporation of the helium matrix in a collision cell filled with room temperature helium or via surface collisions.

Adsorption Forms of NO on Iridium-Doped Rhodium Clusters in the Gas Phase Revealed by Infrared Multiple Photon Dissociation Spectroscopy.

The adsorption of an NO molecule on a cationic iridium-doped rhodium cluster, RhIr, was investigated by infrared multiple photon dissociation spectroscopy (IRMPD) of RhIrNO·Ar complexes in the 300-2000 cm spectral range, where the Ar atoms acted as a messenger signaling IR absorption. Complementary density functional theory (DFT) calculations predicted two near-isoenergetic structures as the putative global minimum: one with NO adsorbed in molecular form in the on-top configuration on the Ir atom in RhIr, and one where NO is dissociated with the O atom bound to the Ir atom in the on-top configuration and the N atom on a hollow site formed by three Rh atoms. A comparison between the experimental IRMPD spectrum of RhIrNO and calculated spectra indicated that NO mainly adsorbs molecularly on RhIr, but evidence was also found for structures with dissociatively adsorbed NO.

The size-dependent influence of palladium doping on the structures of cationic gold clusters.

The physicochemical properties of small metal clusters strongly depend on their precise geometry. Determining such geometries, however, is challenging, particularly for clusters formed by multiple elements. In this work, we combine infrared multiple photon dissociation spectroscopy and density functional theory calculations to investigate the lowest-energy structures of Pd doped gold clusters, PdAu ( ≤ 10).

IR spectroscopic characterization of the co-adsorption of CO and H onto cationic Cu clusters.

To understand elementary reaction steps in the hydrogenation of CO over copper-based catalysts, we experimentally study the adsorption of CO and H onto cationic Cu clusters. For this, we react Cu clusters formed by laser ablation with a mixture of H and CO in a flow tube-type reaction channel and characterize the products formed by IR multiple-photon dissociation spectroscopy employing the IR free-electron laser FELICE. We analyze the spectra by comparing them to literature spectra of Cu clusters reacted with H and with new spectra of Cu clusters reacted with CO.

Structures of Nitrogen Oxides Attached to Anionic Gold Clusters Au Revealed by Infrared Multiple Photon Dissociation Spectroscopy.

The adsorption forms of NO and NO on anionic Au clusters were investigated by a combination of IR multiple photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) calculations. For all three species investigated (AuNO, AuNO, and AuNO), the spectra were found to be consistent with a Y-shaped Au cluster with triangular Au and one Au atom sticking out, on which NO and NO molecules adsorb molecularly. These species are considered as intermediates of the Au-mediated disproportionation reaction of NO, Au(NO) → Au(NO)(NO).

Water Splitting by C -Supported Vanadium Single Atoms.

Water splitting is an important source of hydrogen, a promising future carrier for clean and renewable energy. A detailed understanding of the mechanisms of water splitting, catalyzed by supported metal atoms or nanoparticles, is essential to improve the design of efficient catalysts. Here, we report an infrared spectroscopic study of such a water splitting process, assisted by a C supported vanadium atom, C V +H O→C VO +H .

IR Spectroscopic Characterization of H Adsorption on Cationic Cu ( = 4-7) Clusters.

IR spectra of cationic copper clusters Cu ( = 4-7) complexed with hydrogen molecules are recorded via IR multiple-photon dissociation (IRMPD) spectroscopy. To this end, the copper clusters are generated via laser ablation and reacted with H and D in a flow-tube-type reaction channel. The complexes formed are irradiated using IR light provided by the free-electron laser for intracavity experiments (FELICE).

Not Completely Innocent: How Argon Binding Perturbs Cationic Copper Clusters.

Argon is often considered as an innocent probe that can be attached and detached to study the structure of a particular species without perturbing the species too much. We have investigated whether this assumption also holds for small copper cationic clusters and demonstrated that small but significant charge transfer from argon to metal changes the remaining binding positions, leading in general, to weaker binding of other argon atoms. The exception is binding to just one copper ion, where the binding of the first argon facilitates the binding of the second.

Carbide Dihydrides: Carbonaceous Species Identified in Ta -Mediated Methane Dehydrogenation.

The products of methane dehydrogenation by gas-phase Ta clusters are structurally characterized using infrared multiple photon dissociation (IRMPD) spectroscopy in conjunction with quantum chemical calculations. The obtained spectra of [4Ta,C,2H] reveal a dominance of vibrational bands of a H Ta C carbide dihydride structure over those indicative for a HTa CH carbyne hydride one, as is unambiguously verified by studies employing various methane isotopologues. Because methane dehydrogenation by metal cations M typically leads to the formation of either MCH carbene or HMCH carbyne hydride structures, the observation of a H MC carbide dihydride structure implies that it is imperative to consider this often-neglected class of carbonaceous intermediates in the reaction of metals with hydrocarbons.

The structures of cationic gold clusters probed by far-infrared spectroscopy.

Determining the precise structures of small gold clusters is an essential step towards understanding their chemical and physical properties. Due to the relativistic nature of gold, its clusters remain planar (2D) up to appreciable sizes. Ion mobility experiments have suggested that positively charged gold clusters adopt three-dimensional (3D) structures from n = 8 onward.

Oxophilicity as a Descriptor for NO Cleavage Efficiency over Group IX Metal Clusters.

Iridium and rhodium are group IX elements that can both catalytically reduce NO. To understand the difference in their reactivity toward NO, the adsorption forms of NO onto clusters of Ir and Rh are compared using vibrational spectra, recorded via infrared multiple-photon dissociation spectroscopy. The spectra give evidence for the existence of at least two specific adsorption forms.

Infrared Spectroscopy of Gold Carbene Cation (AuCH): Covalent or Dative Bonding?

The present work explores the structure of the gold carbene cation, AuCH, using infrared multiple photon dissociation action spectroscopy and density functional theory (DFT). Unlike several other 5d transition-metal cations (M = Ta, W, Os, Ir, and Pt) that react with methane by dehydrogenation to form MCH species, gold cations are unreactive with methane at thermal energies. Instead, the metal carbene is formed by reacting atomic gold cations formed in a laser ablation source with ethylene oxide (cCHO) pulsed into a reaction channel downstream.

Structures of Cu ( n = 3-10) Clusters Obtained by Infrared Action Spectroscopy.

Coinage metal clusters are of great importance for a wide range of scientific fields, ranging from microscopy to catalysis. Despite their clear fundamental and technological importance, the experimental structural determination of copper clusters has attracted little attention. We fill this gap by elucidating the structure of cationic copper clusters through infrared (IR) photodissociation spectroscopy of Cu -Ar complexes.

Spectroscopic Identification of the Carbyne Hydride Structure of the Dehydrogenation Product of Methane Activation by Osmium Cations.

The present work explores the structures of species formed by dehydrogenation of methane (CH) and perdeuterated methane (CD) by the 5d transition metal cation osmium (Os). Using infrared multiple photon dissociation (IRMPD) action spectroscopy and density functional theory (DFT), the structures of the [Os,C,2H] and [Os,C,2D] products are explored. This study complements previous work on the related species formed by dehydrogenation of methane by four other 5d transition metal cations (M = Ta, W, Ir, and Pt).