CO adsorption on neutral iridium clusters

TL;DR

This study investigates how carbon monoxide binds to neutral iridium clusters of various sizes using infrared spectroscopy, revealing a consistent atop binding mode influenced by relativistic effects on the metal's electronic structure.

Contribution

It provides detailed spectroscopic data on CO binding geometries on iridium clusters and compares them with other transition metals and surfaces, highlighting the role of relativistic effects.

Findings

CO binds predominantly in atop geometry on iridium clusters

Binding frequencies range from 1962 to 1985 cm-1 depending on cluster size

Relativistic effects influence the preference for atop binding on iridium

Abstract

The adsorption of carbon monoxide on neutral iridium clusters in the size range of n = 3 to 21 atoms is investigated with infrared multiple photon dissociation spectroscopy. For each cluster size only a single v(CO) band is present with frequencies in the range between 1962 cm-1 (n = 8) and 1985 cm-1 (n = 18) which can be attributed to an atop binding geometry. This behaviour is compared to the CO binding geometries on clusters of other group 9 and 10 transition metals as well as to that on extended surfaces. The preference of Ir for atop binding is rationalized by relativistic effects on the electronic structure of the later 5d metals.