Ab Initio Study of the Endohedral Complexes of C₆₀, Si₆₀, and Ge₆₀with Monoatomic Ions:  Influence of Electrostatic Effects and Hardness

Abstract

An ab initio study of endohedral complexes of C 60 and its Si and Ge analogues with first, second, third, and fourth row alkali metal and halogen ions is performed using the multiplicative integral approximation and the 3-21 G basis set (3-21+G for the halogen ions). The properties of the endohedral ions are studied, and complexation energies are calculated using the counterpoise correction for the basis set superposition error. An (approximate) analytical expression for this complexation energy is derived within the framework of density-functional theory. The complexation energy sequences are rationalized using this expression and the properties of the fullerene cages, such as the electrostatic potential within the cage and the average distance of the electrons from the cage center. Besides electrostatic effects, i.e., the interaction of the ion with the electrostatic potential within the cage, the influence of the cage and guest-ion hardnesses on the stabilization energies are also investigated: a local hard and soft acids and bases principle can be invoked to explain the complexation energies within alkali metal and halogen ion series.

Alkali Metal Cation Affinities of Neutral Maingroup-Element Hydrides across the Periodic Table

“…This order in overlap values is also found if we take consistently the same M–NH 3 distance for all M. Thus, if we chose, for example, an M–N distance of 2.75 Å (i.e., the equilibrium distance in the case of M = K), these overlap values still decrease as 0.213, 0.206, 0.196, 0.186, and 0.165 along Li + , Na + , K + , Rb + , and Cs + , respectively. Both trends, in the HOMO–LUMO gap and bond overlap, agree with earlier findings of Geerlings et al, who interpreted them in terms of the hardness of the Lewis acids and bases. − We recall that the cation affinity increases down group 18 for all alkali metal cations. Note that, in absolute terms, this increase is lighter for the heavier alkali metal cations (see Figure ).…”

A Theoretical Study on the Stability of PtL2 Complexes of Endohedral Fullerenes: The Influence of Encapsulated Ions, Cage Sizes, and Ligands

“…Since then, many other experimental and computational works in such fields concerning cation-/anion-encapsulated fullerene chemistry have been greatly achieved. 6−13 Recently, Tobita and co-workers reported the preparations and structural characterizations of the intriguing FTMC, that is, iridium and platinum complexes of the lithium-cation-encapsulated fullerene Li + @C 60 . 14…”

Density functional theory studies of Si36H36 and C36H36 nanocages

“…Since the discovery of C 60 , exploration of similar silicon fullerenes has received considerable attention . This not only includes the analogs Si 60 but also other smaller cages .…”

“…[7][8][9][10][11][12] Since the discovery of C 60 , exploration of similar silicon fullerenes has received considerable attention. [13][14][15] This not only includes the analogs Si 60 but also other smaller cages. [16][17][18][19] Because fullerenes smaller than C 60 violate the isolated pentagon rule (IPR), [20] the synthesis of smaller fullerenes remains a challenge due to the high strain incurred in these structures.…”