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

The authors describe the first study of trinuclear gold(I) pyrazolates on the mol. level by time-dependent scanning tunneling microscopy (STM). On the graphite/1-octanoic acid interface, dodecyl-functionalized gold pyrazolates formed concn.-controlled morphologies. The authors 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 deriv., all studied concns. resulted in a dimeric morphol. However, different concns. led to different transient states during the layer evolution. At low concns., 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 concns. a less stable “line” polymorph was obsd. The confinement of the mols. to the surface led to cooperative dynamics, in which two mols. 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. [on SciFinder(R)]