Labile self-assembled circular patterns of propyl bromide on Si(111)-7×7 at 50 K are shown to convert to corresponding stable circular patterns of atomic bromine through a maskless process of molecular scale imprinting. The imprinting depends on localized chemical reaction induced by either photons or electrons. At 50 K propyl bromide adsorbs in a vertical configuration with lateral attraction. By contrast, at 300 K, octyl chloride and bromide adsorbed horizontally, self-assembling spontaneously into the valuable configurations of switching corrals (‘type I’) and stable corrals (‘type II’). Both types of corral, switching and stable, can be seen to alter the local surface charge distribution.