Basicity Enhancement by Adsorption of Amines on the Na8-Nanoclusters

Strong acids and bases are important compounds in organic chemistry and related industries. Therefore, considerable efforts have been made to design and synthesize molecules with high acidity and basicity [1,2].In this work, the electropositive property of Na8-nanocluster was employed to enhance the basicity of some common amines including ammonia, methyl amine, pyridine, methanol amine, and methanimine. The molecules, clusters, and complexes were structurally optimized by the B3LYP functional and the 6-31+G(d,p) basis set. The frequency calculations were performed at the same level of theory to obtain the thermodynamic properties such as ∆H and ∆G of adsorption and protonation. The results showed that adsorptions of the amines on the Na8 are not strong interactions (with ∆H values in the range of –30 to –40 kJ/mol). Also, the calculated proton affinities (-∆H of protonation) for the isolated amines were 850–990 kJ/mol. After adsorption of the amines on the Na8, their proton affinities increase so that the obtained proton affinity range was 970–1065 kJ/mol. The Mulliken charge analysis showed that, about 30% of the proton charge is accommodated by the Na8 cluster, therefore, protonation of the amines adsorbed on the Na8 results in more stable cation and consequently more basicity.

کلیدواژه ها:

Na8-nanocluster ، Basicity ، Amines ، DFT ، Adsorption