Determination of solvation numbers of [RuII(bpy)3] and [RuII(tpy)2] functionalized-PAMAM dendrimers adsorbed onto platinum electrode surfaces

The solvation numbers of generations 0–4 of [RuII(bpy)3] and [RuII(tpy)2] substituted polyamidoamine (PAMAM) starburst dendrimers adsorbed onto platinum electrode surfaces have been determined using the electrochemical quartz crystal microbalance. For both families of dendrimers, the solvation number increased with increasing generation although values for [RuII(bpy)3] were higher than for [RuII(tpy)2] dendrimers. This was ascribed to differences in the solvophobicity of tpy vs bpy ligands as well as to differences in solubility between the two dendrimer families. Although large numbers of solvent molecules were incorporated by all the dendrimers (for example, dend-64-[RuII(bpy)3] incorporated 2.5 × 103 acetonitrile molecules per dendrimer) when normalized to the surface area of the dendrimer molecules, the solvent layer had a thickness corresponding to less than one solvent molecule.