Light-Induced Contraction/Expansion of 1D Photoswitchable Metallopolymer Monitored at the Solid–Liquid Interface

5 years ago

Light-Induced Contraction/Expansion of 1D Photoswitchable Metallopolymer Monitored at the Solid–Liquid Interface

Paolo Samorì, Gianaurelio Cuniberti, Arezoo Dianat, Artur Ciesielski, Mohamed El Garah, Etienne Borré, Matteo Mauro, Stéphane Bellemin-Laponnaz, Rafael Gutierrez

The use of a bottom-up approach to the fabrication of nanopatterned functional surfaces, which are capable to respond to external stimuli, is of great current interest. Herein, the preparation of light-responsive, linear supramolecular metallopolymers constituted by the ideally infinite repetition of a ditopic ligand bearing an azoaryl moiety and Co(II) coordination nodes is described. The supramolecular polymerization process is followed by optical spectroscopy in dimethylformamide solution. Noteworthy, a submolecularly resolved scanning tunneling microscopy (STM) study of the in situ reversible trans-to-cis photoisomerization of a photoswitchable metallopolymer that self-assembles into 2D crystalline patterns onto a highly oriented pyrolytic graphite surface is achieved for the first time. The STM analysis of the nanopatterned surfaces is corroborated by modeling the physisorbed species onto a graphene slab before and after irradiation by means of density functional theory calculation. Significantly, switching of the monolayers consisting of supramolecular Co(II) metallopolymer bearing trans-azoaryl units to a novel pattern based on cis isomers can be triggered by UV light and reversed back to the trans conformer by using visible light, thereby restoring the trans-based supramolecular 2D packing. These findings represent a step forward toward the design and preparation of photoresponsive “smart” surfaces organized with an atomic precision. The contraction and expansion of self-assembled metallopolymeric arrays containing azobenzene units, triggered by UV–vis and white light irradiation are studied with scanning tunneling microscopy at the solid/liquid interface.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/smll.201701790