STM Study of Gold(I) Pyrazolates: Distinct Morphologies, Layer Evolution, and Cooperative Dynamics

Abstract

We describe the first study of trinuclear gold(I) pyrazolates on the molecular level by time-dependent scanning tunneling microscopy (STM). On the graphite/1-octanoic acid interface dodecyl-functionalized gold pyrazolates formed concentration-controlled morphologies. We found two types of monomeric packing and one dimeric type with two trinuclear gold pyrazolates next to each other on the surface. For an octadecyl-functionalized derivative all studied concentrations resulted in a dimeric morphology. However, different concentrations led to different transient states during the layer evolution. At low concentrations, a transient monomeric state was present with the alkyl chains in a gauche-conformation that subsequently converted to a more optimized anti-conformation. At higher concentrations a less stable “line” polymorph was observed. The confinement of the molecules to the surface led to cooperative dynamics, in which two molecules in a dimer moved as if they were one particle. Furthermore, in a higher level of cooperativity, the rotation of one dimer appears to induce rotations in coupled neighboring dimers.