The asymmetric molecule 4-[trans-2-(pyrid-4-yl-vinyl)] benzoic acid (PVBA) adsorbed
on Cu(111) is characterized by scanning tunneling microscopy (STM) and density functional theory
(DFT) to determine the influence of subsurface atomic layers on the adsorption. In contrast to the
6-fold symmetry of the first atomic layer of close-packed surfaces, we find that the arrangement of
the isolated molecules follows predominantly a 3-fold symmetry. This reduction in symmetry, where
the molecule selects a specific orientation along the Æ-211æ axes, reveals the contribution of lower lying
Cu layers to the molecular arrangement. Our calculations rationalize the interaction of the
substrate with the molecule in terms of electrostatic screening and local relaxation phenomena.
