CO2 Binding at Gold Cluster Cations: An Infrared Free-Electron Laser Spectroscopic Investigation.

Abstract

Understanding the fundamental binding motifs of carbon dioxide is key to its efficient sequestration and/or molecular activation. In this context, gas-phase metal clusters represent key model systems for the design of next generation materials. Infrared spectroscopy, especially using free-electron lasers, provides a direct probe of molecular structure across a range of wavelengths inaccessible by tabletop light sources. Here, we report the investigation of CO2 binding to isolated gold cluster cations, Aun + (n = 4-11), using the FELICE light source, with structural assignments aided by quantum chemical calculations. In order to capture the well-known Fermi dyad arising from resonance between the symmetric stretch and the overtone of the bend, an anharmonic vibrational treatment has been employed. Binding to a gold cluster cation only weakly perturbs the CO2 which retains its linear geometry. Coordination occurs exclusively via an oxygen atom and a single gold atom of the cluster (η1-O), with very weak molecular activation observed. Successive CO2 molecules bind in similar fashion to the first leading to multiply-solvated clusters.

Abstract as supplied by the indexing source. © the authors / publisher.