Endohedral effect in inclusion complexes of the C6 cluster

An approximate theory of bonding in endohedral complexes that are formed by atoms, ions, and molecules trapped inside the C60 cage is formulated. It is found that the electrostatic potential at the cage center (the endohedral potential) determines such electronic properties of the endohedral complexes as the complexation energy, ionization potentials, and the stability with respect to internal electron transfer. The origins of the endohedral effect, i.e., the positive valuedness of the endohedral potential, are investigated with the help of the Thomas–Fermi theory. The theoretical predictions are demonstrated to be in good agreement with the numerical results of ab initio electronic structure calculations.