'Perfect Match'—Combining Density Functional Calculations with Spectroscopic Characterization of Transition Metal Clusters

Abstract

Experimental and theoretical studies of small molecule reactions with metal clusters have in recent years assumed importance as models of heterogeneous catalysis. Metal–molecule adducts are of interest as both a desired step of a catalytic cycle and as a poisoning process. The physical and chemical properties of metal clusters vary dramatically with size. Fig. 1 shows the absolute rate coefficients of the reaction of niobium clusters, Nbn, with N2. Differences of over three orders of magnitude are observed as the cluster size is increased. The geometric structure of clusters has long been shown to be of utmost importance in determining properties, with niobium clusters Nb9, Nb11, and Nb12 all having been shown to have two structural isomers of different reactivity with N2 and D2. While many authors have been able to attribute these vast differences in properties to the geometric and, thus, electronic structure of the cluster, a predictive tool remains elusive. Current research is directed at harnessing the seemingly unstructured variation of the properties seen in metal clusters towards nanoscale catalysis.