Coverage-Induced Conformational Selectivity

Abstract

Different conformations of organic molecules are often almost isoenergetic, giving rise to their coexistence at finite temperature. In the gas phase, pressure was used to shift the equilibrium toward desired conformers. Here we use lateral pressure, enforced by increased coverage, to change the relative abundance of conformers of astraphloxin, an industrial dye, on Ag(100). We show in a variable temperature scanning tunnelling microscopy study that higher coverages enforce the predominance of one conformer only, leading to a homoconformational superstructure. The necessary conformational changes are possible at temperatures as low as 120 K.