Self-Assembled Monolayers of Ruthenium and Osmium Bis-Terpyridine Complexes-Insights of the Structure and Interaction Energies by Combining Scanning Tunneling Microscopy and Electrochemistry

摘要

Self-assembled monolayers of [Ru(terpy)(terpy-py)]~(2+) and [Os(terpy)(terpy-py)]~(2+) salts (terpy is 2,2':6',2"-terpyridine and terpy-py is 4'-(4-pyridyl)-2,2':6',2"-terpyridine) on platinum were investigated by means of STM and electrochemistry. The STM experiments reveal that the species within the monolayer are ordered in a hexagonal array. This information was utilized together with the scan rate dependency of the peak current density (j_p) of potential sweep experiments to calculate interaction energies within the monolayer. Significantly, the repulsive interactions within the monolayers of 2,2':6',2"-terpyridine complex are greater than those observed with analogous 2,2'-bipyridine species. This results in a lower overall surface coverage, an ordered structure where each particle has 6 closest neighbors, and a shift of the redox potentials toward more positive values with the terpy complexes. Also, a correlation between the solvent dielectric constant and the interaction energies could be established, reflecting the different ability of the solvent to screen charges depending upon its polarity.