Adsorption of neutral and protonated Lewis bases on $$\hbox {Na}_{8}$$ Na 8 -nanocluster: basicity enhancement of the Lewis bases

Abstract

Structural and energetic properties of Na n (n = 1-8) nanoclusters were studied employing the B3LYP method and using 6-31+(d,p) basis set. Comparison of the calculated binding energies per atom (E b) of the cluster shows that the Na 8 cluster with D 2 d symmetry group is the most stable structure among the Na n clusters. Adsorption of neutral and protonated forms of ammonia, methylamine, ethylamine, hydrazine, guanidine, pyridine, methanolamine, and methanimine on Na 8 cluster was studied. Interaction of the neutral Lewis bases with Na 8 was very weak such that the interaction energies were smaller than − 50 kJ mol −1. However, the protonated bases interact with Na 8 more strongly with interaction energies generally in the range of − 90 to − 350 kJ mol −1. The protonated forms of methanolamine undergo dissociative adsorption on Na 8 with adsorption energies of about − 800 kJ mol −1. Since the protonated bases are stabilized more than the corresponding neutral ones upon adsorption on Na 8 cluster, the basicity of the Lewis bases enhances in the presence of Na 8. The calculated proton affinities of the isolated Lewis bases were smaller than 990 kJ mol −1 while in the presence of the Na 8 cluster, the basicity increases so that the calculated proton affinities were higher than 1000 kJ mol −1 .