Designing Pancake-Bonded Heterodimers for Scanning Probe Microscopy.

Computational modeling of heterodimers of mono- and diradical molecules with C60- indicates that scanning probe microscopy could characterize multicenter covalent-like interactions, also known as pancake bonds, on surfaces. By functionalizing the SPM tip with C60 and creating its monoanionic state by applying the corresponding voltage, individual pancake-bonded heterodimers with various radical molecules can be formed and characterized. All three proposed radical/diradical molecules readily form pancake-bonded dimers with C60-, and their structural and energetic minima are easily discernible from the dispersion-bonded van der Waals heterodimers with C60. Two of the three newly designed heterodimers show intermolecular C···C distances that are shorter than the current shortest pancake bond. This exploratory work aims to stimulate new studies on the interactions of radical molecules by the use of SPM techniques.