Using functionalized tips mounted on noncontact atomic force microscope to break chemical bonds within molecules – a computational perspective

“What would the properties of materials be if we could really arrange the atoms the way we want them? […] I can hardly doubt that when we have some control of the arrangement of things on a small scale we will get an enormously greater range of possible properties that substances can have, and of different things that we can do.” – Richard P. Feynman (1959). Feynman’s idea has been, partially, realized through the use of noncontact atomic force microscope (nc-AFM).

In a joint experimental-theoretical work, we report the details of a single dative bond breaking process using nc-AFM. The dative bond between carbon monoxide (CO) and ferrous phthalocyanine (FePc) is ruptured via mechanical forces applied by AFM tips. We employ real-space pseudopotentials constructed within density functional theory code, PARSEC (http://real-space.org/), to simulate nc-AFM images and calculate the intermolecular forces. We find the dative bond between CO and FePc can be ruptured either by an attractive force (Cu tip) of ~150 pN or by a repulsive force (CO tip) of ~220 pN with a significant contribution of shear forces, accompanied by changes of the spin state of the system.