Reversible Control over Molecular Recognition in Surface-Bound Photoswitchable Hydrogen-Bonding Receptors: Towards Read–Write–Erase Molecular Printboards

The synthesis of an anthracene-bearing photoactive barbituric acid receptor and its subsequent grafting onto azide-terminated alkanethiol/Au self-assembled monolayers by using an Cu-catalyzed azide-alkyne reaction is reported. Monolayer characterization using contact-angle measurements, electrochemistry, and spectroscopic ellipsometry indicate that the monolayer conversion is fast and complete. Irradiation of the receptor leads to photodimerization of the anthracenes, which induces the open-to-closed gating of the receptor by blocking access to the binding site. The process is thermally reversible, and polarization-modulated IR reflection-absorption spectroscopy indicates that photochemical closure and thermal opening of the surface-bound receptors occur in 70 and 100 % conversion, respectively. Affinity of the open and closed surface-bound receptor was characterized by using force spectroscopy with a barbituric-acid-modified atomic force microscope tip. Sticky fingers: A photoactive barbiturate receptor is covalently bound to a surface to prepare molecular printboards in which hydrogen-bonding recognition can be written using light thanks to the intramolecular dimerization of appended anthracenes (see figure).