H e 2 @ C 60 : Thoughts of the concept of a molecule and of the concept of a bond in quantum chemistry

We present a broad palette of discussions of the concepts of a molecule and a chemical bond that always lay down behind all computational modeling in quantum chemistry and of the endohedral fullerene He 2 @C 60 in particular. For this purpose, we offer the definition of quantum chemistry as composed of three ingredients. Each of them is illustrated by its particular concept, either that of a molecule or a bond. The third, computational ingredient is tackled to resolve the bonding manifold of He 2 @C 60 and to demonstrate that van‐der‐Waals binding of HeHe is converted within He 2 @C 60 into a stronger bond due to that C 60 acts as an electronic buffer and [He 2 ] moiety mimics a fractionally chargedHe 2 δ +. Experimental fingerprints of He 2 @C 60 are computed. © 2015 Wiley Periodicals, Inc.