Size-Specific, Dissociative Activation of Carbon Dioxide by Cobalt Cluster Anions

Abstract

The reaction of cobalt cluster anions Co_n^– (3 ≤ n ≤ 17) with CO₂ was studied experimentally and theoretically to explore the size-specific activation mode of CO₂ by Co_n^–. Mass spectrometric measurements revealed that the reactivity depends strongly on cluster size: the reactivity emerges abruptly at n = 7, peaks at n = 8–10, and then gradually decreases with increasing n. Infrared multiple photon dissociation spectra of Co_nCO₂^– exhibit a single peak at ∼1870 cm^–1, similarly to the previously reported spectra of Co_nCO^–. Density functional theory calculations for Co₇CO₂^– as an example revealed that the dissociative adsorption of CO₂ into CO and O is energetically more favorable than nondissociative adsorption. The infrared spectra calculated for dissociated isomers Co₇(CO)O^– reproduced the experimental results, whereas those for nondissociated isomers Co₇CO₂^– did not. The photoelectron spectra of Co_nCO₂^– were shifted dramatically toward higher energies relative to those of Co_n^–, suggesting electron transfer from Co_n^– to the CO and O ligands. These results indicate that the CO₂ molecule adsorbs dissociatively on Co_n^–, in sharp contrast to its nondissociative adsorption onto the Co monomer anion

Free electron laser infrared action spectroscopy of nitrous oxide binding to platinum clusters, Ptn(N2O)+

“…The infrared multiple-photon dissociation (IR-MPD) spectra presented in this report were recorded at the Fritz Haber Institute (FHI) in Berlin making use of the FHI free electron laser (FEL) 37 facility. The experimental setup has been described in detail previously 38,39 and only essential details are described here. Briefly, a rotating natural Pt target is ablated by a Nd:YAG laser (532 nm, 10 Hz).…”

IR Signature of Size‐Selective CO2 Activation on Small Platinum Cluster Anions, Ptn− (n=4–7)

“…[19] Relevant to the studies here, CO2 was found to adsorb only on cobalt cluster anions Conwith n > 7, and a strong C=O stretching band around 1900 cm -1 signified dissociative binding. [20] The instrument and IR source used in these studies have been described previously. [20][21] Briefly, platinum cluster anions were generated by pulsed laser ablation of a 194 Pt isotopicallyenriched target.…”

“…[20] The instrument and IR source used in these studies have been described previously. [20][21] Briefly, platinum cluster anions were generated by pulsed laser ablation of a 194 Pt isotopicallyenriched target. CO2 was introduced to a reaction channel downstream at ~30 °C and the resulting anionic cluster distribution was probed by reflectron time-of-flight mass spectrometry.…”

Reductive Activation of Small Molecules by Anionic Coinage Metal Atoms and Clusters in the Gas Phase

“…Photoelectron spectroscopice xperiments revealed that the electronic charge was partly transferred to the Oa tom during the reaction. [47]…”

“…It was demonstrated by means of IRMPD spectroscopy that CO 2 was dissociatively activated on Co n − ( n =3–17) to form Co n (CO)O − , where the CO and O units are bonded to different sites of the cluster. Photoelectron spectroscopic experiments revealed that the electronic charge was partly transferred to the O atom during the reaction …”