Adsorption-induced chirality influences surface orientation in organic self-assembled structures: An STM study of PVBA on Pd(1 1 1)

The adsorption of the planar organic molecule, 4-trans-2-(pyrid-4-yl-vinyl) benzoic acid (PVBA), on Pd(111) under ultrahigh vacuum conditions produces molecular dimers and trimers. Scanning tunneling microscopy (STM) images reveal that dimers are formed preferentially over the trimer structures. Adsorption of the asymmetric planar molecule induces chirality in the adsorbed structures and results in homo-chiral and hetero-chiral dimers of PVBA. The STM results further reveal an orientation-specific adsorption of the different chiralities. A statistical analysis of the observed structures indicates an equivalent presence of the two dimer types on a surface not inherently offering any form of chiral recognition. The chiral dimer pairs are further resolved through site-specific adsorption orientations with respect to the Pd lattice. These investigations demonstrate the cooperative roles of substrate-adsorbate binding and intermolecular interactions in the formation of these self-assembled structures.