Infrared action spectroscopy of nitrous oxide on cationic gold and cobalt clusters

Abstract

Infrared multiple-photon dissociation spectroscopy reveals the nature of nitrous oxide binding to metal clusters.

Atomic Cluster Au10+ Is a Strong Broadband Midinfrared Chromophore

“…In each system, the spectrum comprises a smooth continuous absorption from 700 cm -1 upwards and has not reached its peak by 3400 cm -1 , the upper limit of our measurements. In [Au10OCS] + and [Au10N2O] + , the narrow OCS and N2O molecular vibrational absorption features are clearly visible on top of this broad background and have been discussed elsewhere [62,87].…”

“…Full experimental and computational details are given in the Supporting Information, which includes refs [63][64][65][66] and [67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86], respectively. Briefly, clusters are generated by laser ablation of a gold target and cooled by collision in a clustering channel maintained at 105-300 K. Adsorbates are introduced either via a late mixing valve (OCS, N2O) [62,87] or seeded in the helium carrier gas (Ar). Previous experiments have shown that clusters thermalise effectively to the temperature of such sources [88].…”

Spectroscopy and Infrared Photofragmentation Dynamics of Mixed Ligand Ion–Molecule Complexes: Au(CO)x(N2O)y+

“…This vibrational band is significantly blue-shifted from that of free N 2 O by the electron donation from the 7σ HOMO–1 orbital (which is slightly antibonding with respect to the NN bond) to the Au + center, which itself exhibits significant sd hybridization (the Orgel effect) enhancing the orbital overlap. This binding mechanism has been discussed in detail in our previous studies of M­(N 2 O) n + ion–molecule complexes. ,− This band is observed only in complexes with fewer than two CO molecules (i.e., x < 2 complexes) in which N 2 O can occupy the core. In complexes with more CO molecules, nitrous oxide binds only in a second coordination shell, and no blue-shift is observed.…”

“…In practice, this means the presence of at least one weakly bound ligand, the loss of which, upon absorption of an infrared photon, occurs on a time scale faster than that of the experiment (∼10 μs). Well-defined spectral bands are observed in three distinct regions2200 ± 10, 2230 ± 10, and 2350 ± 10 cm –1 and can be interpreted in terms of a few general features: Both the CO stretch and the N 2 O antisymmetric (NN) stretch fundamental bands occur in this spectral region (the free molecule bands are shown in Figure as dashed lines at 2143.2 and 2223.5 cm –1 , respectively , ). Au + tends to form strongly bound, linear AuL 2 + complexes with two core ligands. ,, CO binds more strongly to Au + than does N 2 O and is preferentially found in the core. N 2 O can bind to the Au + center via either the terminal N atom or the O atom. ,− CO binds exclusively via the C atom (direct Au–O atom bound motifs lie >1.3 eV higher in energy). …”

“…N 2 O can bind to the Au + center via either the terminal N atom or the O atom. ,− CO binds exclusively via the C atom (direct Au–O atom bound motifs lie >1.3 eV higher in energy).…”