Tip-Induced Structural Transitions in a Buckybowl Molecular Assembly.

Abstract

Conformational switching of three-dimensional curved molecules on surfaces is governed by complex potential energy landscapes shaped by substrate coupling and intermolecular constraints. Here, using low-temperature scanning tunneling microscopy, we investigate tip-induced structural transitions of individual sumanene buckybowls confined within a self-assembled 2U1D honeycomb lattice on Au(111). By combining tip proximity with bias-driven excitation, we trigger conformational switching that yields two operationally distinguishable outcomes: bowl inversion and molecular rotation, producing characteristic tunneling current jumps of distinct magnitudes. The inversion outcome leads to a robust locked configuration, whereas the rotated state is metastable and readily reverses under external perturbations. Occasional two-step current signatures raise the possibility that these outcomes may share a common rotational intermediate. Comparative experiments on Ag(111) and with corannulene reveal that the herringbone reconstruction of Au(111), together with molecular curvature and steric confinement, collectively governs the potential energy landscape that enables these transformations. These findings provide qualitative mechanistic understanding of conformational dynamics in surface-supported molecular architectures.