Theoretical studies on the interaction of some endohedral fullerenes {[X@C60]− (X = F−, Cl−, Br−) or [M@C60] (M = Li, Na, K)} with [Al(H2O)6]3+ and [Mg(H2O)6]2+ cations

The effect of various encaged species (F−, Cl−, Br−, Li, Na and K) on the interaction of fullerene molecule with [Al(H2O)6]3+ and [Mg(H2O)6]2+ cations was theoretically studied. At first, the possibility of encapsulation of above species into the fullerene cage was studied. Therefore, the formation energies were calculated for all of these compounds. Then the interactions between [X@C60]− (X = F−, Cl−, Br−) or [M@C60] (M = Li, Na, K) complexes, with [Al(H2O)6]3+ and [Mg(H2O)6]2+ cations were investigated. Density functional theory (DFT), atoms-in-molecules (AIM) and natural bond orbital (NBO) calculation were applied to understand the nature of the interactions. The interaction energies were also calculated for all compounds. Generally, our computations reveal that the encapsulated atom/ion increases the interaction of the fullerene surface with above cations. It was shown that the negative charge of carbon atoms in [M@C60] complexes is larger than in [X@C60]− anions. However, the strength of the reactions/interactions of [Al(H2O)6]3+ and [Mg(H2O)6]2+ cations with [X@C60]− endofullerenes is considerably greater than that with [M@C60]. Thus the results show that the total negative charge of endofullerene has significantly greater effect on the above interaction than the negative charge of fullerene carbon atoms.