Two-dimensional condensation and reorientation of the bromide salt of the heptyl viologen cation radical at the Hg DMSO interface

In DMSO containing Br- ions, the heptyl viologen cation radical (HV .(+)) c an form two different types of two-dimensional (2D) phase on Hg. Thus, HV . (+) can take a planar conformation relative to the surface; however, depend ing on the applied potential, it can reorient itself to adopt a conformatio n where the bipyridine group lies edge-on or tilted relative to the electro de surface. We analyzed the structure and stability of the two phases and f ound HV .(+) and Br- ions to take part in a 1:1 ratio in both. We also stud ied the kinetics of formation of the two phases, as well as that of reorien tation between them, and found both to involve two-dimensional nucleation a nd growth mechanisms.