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

Buckminsterfullerene C60 has received extensive research interest ever 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 C60-fullerene surface makes it a fascinating molecule. However, to date there is uncertainty about the binding location of such decorations on the C60 surface, even for a single adsorbed metal atom. In this work, we report the gas-phase synthesis of the C60V+ complex and its in-situ characterization by mass spectrometry and in-frared spectroscopy with the help of quantum chemical calculations and molecular dynamics simulations. We identify the most probable binding position of a vanadium cation on C60 above a pentagon center in eta5-fashion, demonstrate a high thermal stability for this complex, and explore the bonding nature between C60 and the vanadium cation, reveal-ing that large orbital and electrostatic interactions lie at the origin of the stability of the eta5-C60V+ complex.Comment: 29 pages (11 pages for main text and 17 pages for the supporting information

Not Completely Innocent:How Argon Binding Perturbs Cationic Copper Clusters

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Tuning the degree of CO2 activation by carbon doping Cun- (n = 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 CO2 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 CunCm- (n=3–10, m = 1–2) are reacted with CO2 and investigated by IR multiple-photon dissociation (IR-MPD) spectroscopy to probe the degree of CO2 activation. IR spectra for the reaction products [CunCCO2]-, (n = 6–10), and [CunC2.CO2]-, (n = 3–8) are compared to reference spectra recorded for products formed when reacting the same cluster sizes with CO, and with density functional theory (DFT) calculated spectra. The results reveal a size- and carbon load-dependent activation and dissociation of CO2. The complexes [CunC.CO2]- with n = 6 and 10 show predominantly molecular activation of CO2, while those with n = 7–9 show only dissociative adsorption. The addition of the second carbon to the cluster leads to the exclusive molecular activation of the CO2 on all measured cluster sizes, except for Cu5C2- where CO2 dissociates. Combining these findings with DFT calculations leads us to speculate that at lower carbon-to-metal ratios (CMRs), the C can act as an oxygen anchor facilitating the OC=O bond rupture, whereas at higher CMRs the carbon atoms increasingly attract negative charge, reducing the Cu cluster’s ability to donate electron density to CO2, and consequently its ability to activate CO2

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. Size distributions of the selected dopant cluster ions are determined utilizing a high-resolution time of flight mass spectrometer. The comparison of the experimental data, with simulations taking into consideration the pickup probability into a shrinking He droplet due to evaporation during the pickup process, provides a simple explanation for the emergence of size distributions that are narrower than Poisson

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. Size distributions of the selected dopant cluster ions are determined utilizing a high-resolution time of flight mass spectrometer. The comparison of the experimental data, with simulations taking into consideration the pickup probability into a shrinking He droplet due to evaporation during the pickup process, provides a simple explanation for the emergence of size distributions that are narrower than Poisson

Tuning the Dissociative Action of Cationic Rh Clusters Toward NO by Substituting a Single Ta Atom

Modification of Rh chemical activity for decomposition of NO by alloying with Ta was studied by vibrational spectroscopy of gas-phase clusters, where one single Rh atom was substituted by Ta, with NO adsorbed. While NO adsorbs molecularly on pure Rh clusters, it was found to adsorb dissociatively on Rh_<i>n</i>Ta⁺ (<i>n</i> = 2–8) with the O bound to the Ta on-top site. A reaction path for NO decomposition obtained by density functional theory calculations for octahedral Rh₅Ta⁺ and Rh₆⁺ suggests that the Ta oxygen affinity strongly reduces the energy barrier right before bond cleavage, facilitating NO dissociation. The trend is consistent with the Bell–Evans–Polanyi principle. The addition of other less oxophilic dopant atoms could plausibly enhance catalytic reactivity of Rh

Structural characterization of [M,C,2H](+) products formed by reaction of 5d metal cations Pt+ and Ir+ with ethylene oxide and Ta+ with methane using messenger spectroscopy

Structural characterization of gas-phase [M,C,2H]+(M = Ta, Ir, Pt), formed by reacting laser ablationformed M+with ethylene oxide (c-C2H4O) or methane under multiple collision conditions, is achievedusing infrared multiple-photon dissociation (IR-MPD) spectroscopy with the intracavity free-electronlaser FELICE. After product formation, part of the product distribution is complexed with Ar, allowingfor simultaneous recording of IR-MPD spectra of both bare [M,C,2H]+, which dissociates viadehydrogenation, and [M,C,2H]+∙Ar, which loses Ar. Comparison of the spectra with density functionaltheory (DFT) calculations allows for an internally consistent assignment of the spectra to the Ta+CH2(3A00) distorted carbene, Pt+CH2(2A1) carbene, and to the HIr+CH (1A0) carbyne-hydride. Evidence for asymmetric Ta+CH2∙Ar (3B2) complex is also obtained. For Pt and Ir, these structures match those foundin previous work when these species were formed by reaction of M+with methane, CH4and CD4.Under the current conditions, no clear signs of the previously observed Ir+CH2(3A2) carbene product werefound, consistent with its higher energy, especially after Ar complexation. Potential energy surfaces forthe reactions of Pt+and Ir+with c-C2H4O are also computed

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

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Mixed Cluster Ions of Magnesium and C₆₀

Magnesium clusters exhibit a pronounced nonmetal-to-metal transition, and the neutral dimer is exceptionally weakly bound. In the present study, we formed pristine Mgnz+ (n = 1–100, z = 1–3) clusters and mixed (C60)mMgnz+ clusters (m = 1–7, z = 1, 2) upon electron irradiation of neutral helium nanodroplets doped with magnesium or a combination of C60 and magnesium. The mass spectra obtained for pristine magnesium cluster ions exhibit anomalies, consistent with previous reports in the literature. The anomalies observed for C60Mgn+ strongly suggest that Mg atoms tend to wet the surface of the single fullerene positioning itself above the center of a pentagonal or hexagonal face, while, for (C60)mMgnz+, the preference for Mg to position itself within the dimples formed by fullerene cages becomes apparent. Besides doubly charged cluster ions, with the smallest member Mg22+, we also observed the formation of triply charged ions Mgn3+ with n > 24. The ion efficiency curves of singly and multiply charged ions exhibit pronounced differences compared to singly charged ions at higher electron energies. These findings indicate that sequential Penning ionization is essential in the formation of doubly and triply charged ions inside doped helium nanodroplets