Analysis of metallo-supramolecular systems using single-molecule force spectroscopy

Single-molecule force spectroscopy has been used for the investigation of the rupture behavior of individual metallo-supramolecular systems. For this purpose, a specifically designed unsymmetrical ,-functionalized poly(ethylene oxide) has been employed for mono-termination with a terpyridine ligand and subsequently for the attachment onto atomic force microscopy (AFM) tips and microscope slide substrates. Metallo-supramolecular complexes were formed by the use of ruthenium(III)-ruthenium(II) chemistry. Vertical stretching with the AFM cantilever ruptured the coordinative bonds. The rupture force of individual bisterpyridine ruthenium(II) complexes was determined to be 95 pN at a force loading rate of 1 nN s-1. Simultaneous rupturing of multiple parallel metallo-supramolecular bonds was also observed. Monte Carlo simulations corroborated the experimental observations. The presented results lay the basis for the application of such metallo-supramolecular systems in advanced functional nanomaterials.