Adsorption of neutral and protonated Lewis bases on -nanocluster: basicity enhancement of the Lewis bases

Structural and energetic properties of (-8) nanoclusters were studied employing the B3LYP method and using 6-31+(d,p) basis set. Comparison of the calculated binding energies per atom ( of the cluster shows that the cluster with symmetry group is the most stable structure among the clusters. Adsorption of neutral and protonated forms of ammonia, methylamine, ethylamine, hydrazine, guanidine, pyridine, methanolamine, and methanimine on cluster was studied. Interaction of the neutral Lewis bases with was very weak such that the interaction energies were smaller than kJ mol. However, the protonated bases interact with more strongly with interaction energies generally in the range of to kJ mol. The protonated forms of methanolamine undergo dissociative adsorption on with adsorption energies of about kJ mol. Since the protonated bases are stabilized more than the corresponding neutral ones upon adsorption on cluster, the basicity of the Lewis bases enhances in the presence of . The calculated proton affinities of the isolated Lewis bases were smaller than 990 kJ mol while in the presence of the cluster, the basicity increases so that the calculated proton affinities were higher than 1000 kJ mol(-1). SYNOPSIS Adsorption of neutral amines on is very weak while protonated amines are more strongly adsorbed on . These results showed that the cluster stabilizes the protonated amines better than the corresponding neutral ones. Therefore, basicity of the amines is enhanced in the presence of the cluster.