Electronic Coupling of Molecular Complexes to Au electrodes Mediated via Host-Guest Interactions

Immobilization of molecular catalysts onto electrode surfaces using host-guest (HG) interactions enables facile regeneration of electrodes following catalyst degradation. Beyond this practical aspect, the architecture also offers a unique way to study the electronic coupling of molecules to the electrode through a nominally insulating linker. Here, we employ surface-enhanced infrared absorption spectroscopy (SEIRAS) to characterize the binding and the electronic coupling of Au-bound HG complexes. Distinct spectral features and binding kinetics differentiate host-bound species from physisorbed analogues, confirming well-defined HG assemblies on the surface. Analysis of the wavenumber shifts of the guest as a function of applied potential suggests that while the coupling of physisorbed guests with the surface is not strong, the host-bound guests show a substantial electronic coupling considering its distance from the surface of about 1.3 nm. Density functional theory calculations reveal the key role of the host in mediating this long-range coupling between the Au surface and the guest.