Reactivity and Photoionization Studies of Bimetallic Cobalt−Manganese Clusters

The reactivity of selected Co n Mn m (8 ≤ m + n ≤ 23) clusters with N2 and the vertical ionization potentials (IPs) of selected Co n Mn m (8 ≤ m + n ≤ 31) clusters have been measured. No obvious correlation is found between the reactivities and the IPs. Inferences about cluster structure may be made from the nitrogen uptake data. In particular, whereas pure cobalt clusters tend to adopt structures having bulk packing, incorporation of manganese atoms into the cluster shifts the relative energies of close-lying isomers to favor an icosahedral growth sequence. For many cluster sizes, the maximum number of nitrogen molecules adsorbed on a cluster at −80 °C is equal to the number of cobalt atoms on the surface of the cluster, thereby giving insight into the cluster structure and the locations of the individual cobalt and manganese atoms in these bimetallic species.