Optically Activated Uptake and Release of Cu2+ or Ag+ Ions by or from a Photoisomerizable Monolayer-Modified Electrode

Abstract

Di-(N-butanoic acid-1,8-naphthalimide)-piperazine dithienylethene was covalently linked to a cysteamine monolayer associated with a Au surface to yield a photoisomerizable monolayer composed of the open or closed dithienylcyclopentene isomers (3a or 3b), respectively. Electrochemical and XPS analyses reveal that the association of metal ions to the monolayer is controlled by its photoisomerization state. We find that Cu(2+) ions reveal a high affinity for the open (3a) monolayer state, K(a) = 4.6 × 10(5) M(-1), whereas the closed monolayer state (3b) exhibits a substantially lower binding affinity for Cu(2+), K(a) = 4.1 × 10(4) M(-1). Similarly, Ag(+) ions bind strongly to the 3a monolayer state but lack binding affinity for the 3b state. The reversible photoinduced binding and dissociation of the metal ions (Cu(2+) or Ag(+)) with respect to the photoisomerizable monolayer are demonstrated, and the systems may be used for the photochemically controlled uptake and release of polluting ions. Furthermore, we demonstrate that the photoinduced reversible binding and dissociation of the metal ions to and from the photoisomerizable electrode control the wettability properties of the surface.