Radial Control of Recognition and Redox Processes with Multivalent Nanoparticle Hosts

Mixed Monolayer Protected Gold Clusters (MMPCs) featuring both hydrogen bonding and aromatic stacking molecular recognition functionalities have been used to create multivalent hosts for flavins. Multitopic binding of these hosts to flavin was shown to have a strong radial dependence:  when the recognition site was brought closer to the MMPC surface, recognition was enhanced ∼3-fold due to increased preorganization. The effect of preorganization is reversed upon reduction of flavin, where the MMPC with longer side chains bind the flavin guest ∼7-fold stronger than the short chain counterpart due to unfavorable dipolar interactions between the electron-rich aromatic stacking units of the host and the anionic flavin guest. This fine-tuning of recognition and redox processes provides both a model for enzymatic systems and a tool for the fabrication of devices.