Ligand Initiated Self-Assembly of Pt and Ir Nanoparticles about Ru(II) Diimines in Room Temperature Fluid Solution (vol 117, pg 1925, 2013)

The addition of Pt or Ir nanoparticles (np's) capped with poly(vinylpyrrolidone), designated M(PVP)(n), to aqueous-ethanol solutions of (bpy)(2)Ruppz(2+), bis(2,2'-bipyridine)-(4,7-phenanthrolino-5:6,5'6'-pyrazine)ruthenium(II), and (bpy)(2)Rudpp(2+), bis(2,2'-bipyridine)(2,3-bis(2-pyridyl)pyrazine)-ruthenium(II), leads to the spontaneous aggregation of the nanoparticles about the complex. A comparison of the aggregation about different Ru(II) diimines indicates aggregation initiates at the heteroleptic ligand. Although initiating at the ppz ligand, continued aggregation of the np's about the complex dilutes the specificity of the initial interaction, leading to larger aggregates of differing shape. TEM analyses of the aggregates indicate the volume occupied by the individual np's is a small fraction of the total volume of the aggregate, suggesting a somewhat open structure interlaced with the solvent. Correlating TEM analyses of the aggregation with the electronic spectra of the solutions reveals a new absorption assigned to the formation of the (bpy)(2)Ruppz(2+)-M(PVP)(n) aggregates. Analysis of the latter absorption as a function of the concentration of np's indicates stepwise formation of the (bpy)(2)Ruppz(2+)-M(PVP)(n) aggregates. Consistent with the self-assembly of the aggregates, intensity and lifetime quenching of the complex by the np's show that >= 80% of the quenching occurs by a static mechanism, i.e., the self-assembly of the (bpy)(2)Ruppz(2+)-M(PVP)(n) aggregates.