  Our ability to understand and tailor metal-organic interfaces is mandatory to
functionalize organic complexes for next generation electronic and spintronic
devices. For magnetic data storage applications, metal-carrying organic
molecules, so called single molecular magnets (SMM) are of particular interest
as they yield the possibility to store information on the molecular scale. In
this work, we focus on the adsorption properties of the prototypical SMM
Sc3N@C80 grown in a monolayer film on the Ag(111) substrate. We provide clear
evidence of a pyramidal distortion of the otherwise planar Sc3N core inside the
carbon cage upon the adsorption on the Ag(111) surface. This adsorption induced
structural change of the Sc3N@C80 molecule can be correlated to a charge
transfer from the substrate into the lowest unoccupied molecular orbital of
Sc3N@C80, which significantly alters the charge density of the fullerene core.
Our comprehensive characterization of the Sc3N@C80-Ag(111) interface hence
reveals an indirect coupling mechanism between the Sc3N core of the fullerene
molecule and the noble metal surface mediated via an interfacial charge
transfer. Our work shows that such an indirect coupling between the
encapsulated metal centers of SMM and metal surfaces can strongly affect the
geometric structure of the metallic centers and thereby potentially also alters
the magnetic properties of SMMs on surfaces.
