Donor–acceptor interactions between molecular coadsorbates on Ru(001)

Abstract

The interactions in coadsorbed layers consisting of donor–acceptor molecules (CO, NH₃, PF₃) on Ru(001) were studied by thermal desorption and high-resolution electron energy loss spectroscopy (HREELS). Attractive interactions were observed when a donor and an acceptor (opposite dipoles) were coadsorbed, as in NH₃–CO and NH₃–PF₃. For these systems, HREELS evidence is presented for charge transfer between the coadsorbates and a shift in CO adsorption site. The polarization of charge away from NH₃ leads to an enhancement of the Ru–NH₃ bond strength. The interaction in the PF₃–CO system (of similarly oriented dipoles) appears to be neutral.