Grafting Crown Ether Alkali Host-Guest Complexes at Surfaces by Electrospray Ion Beam Deposition
The functionalization of surfaces with host guest compounds is promising for many applications, yet often limited by constraints such as the volatility of the functional compound or the lack of binding to the surface. We use electrospray ion beam deposition (ES-MD) on surfaces in ultrahigh vacuum as a novel approach to modify an atomically defined copper surface with preformed dibenzo-24-crown-8-alkali complexes, in which the central ion (H+, Na+, or Cs+) can be exchanged in the electrospray solution. In situ scanning tunneling microscopy maps the single alkali ion complexes as an oval protrusion with a four-lobe submolecular structure immobilized at the surface. Density functional theory calculations confirm that the crown ether is bound to the surface via the central alkali ion within its cavity, indicating that the properties of the molecular complex are retained after deposition.