RESUMEN
Flattening helices while keeping the handedness: On-surface cyclodehydrogenation of bishelicene enantiomers leads stereospecifically to (M,M) and (P,P) chiral planar polyaromatic hydrocarbons. This is followed by their homochiral aggregation into a 2D conglomerate. Thermally induced cyclodehydrogenation proceeds stereospecifically to chiral, planar coronocoronene. Such a reaction is a special example of topochemistry in which enantiospecific conversion is supported by the alignment of the reactant by the surface.
RESUMEN
The adsorption behavior of tin phthalocyanine (SnPc) molecules on rutile TiO2(110) was studied by scanning tunneling microscopy (STM). Low-temperature STM measurements of single molecules reveal the coexistence of two conformations of molecules on the TiO2 surface. Density functional theory-based simulations (DFT) indicate that the difference originates from the position of the tin atom protruding from the molecule plane. The irreversible switching of Sn-up molecules into the Sn-down conformation was observed either after sample annealing at 200 °C or as a result of tip-induced manipulation. Room-temperature measurements conducted for a coverage of close to a monolayer showed no tendency for molecular arrangement.