Visualization and Comprehension of Electronic and Topographic Contrasts on Cooperatively Switched Diarylethene-Bridged Ditopic Ligand

• Published in: Nanomaterials (Basel, Switzerland) Vol. 12; no. 8; p. 1318
• Main Authors: Hnid, Imen, Guan, Lihao, Chatir, Elarbi, Cobo, Saioa, Lafolet, Frédéric, Maurel, François, Lacroix, Jean-Christophe, Sun, Xiaonan
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 12.04.2022; MDPI
• Subjects: Acids; bipyridine; Chemical Sciences; cooperative switches; Density functional theory; Density of states; diarylethene; Electron density; high-resolution scanning tunneling microscopy; Irradiation; Isomers; Ligands; Light; Light irradiation; Liquid-solid interfaces; Material chemistry; Metal fatigue; Molecular machines; molecular orbital; Molecular orbitals; Organic chemistry; photochromic; Radiation; Scanning tunneling microscopy; Spectrum analysis; bipyridine; molecular orbital; diarylethene; photochromic; cooperative switches; DFT calculations; high-resolution scanning tunneling microscopy
• ISSN: 2079-4991; 2079-4991
• DOI: 10.3390/nano12081318

Diarylethene is a prototypical molecular switch that can be reversibly photoisomerized between its open and closed forms. Ligands bpy-DAE-bpy, consisting of a phenyl-diarylethene-phenyl (DAE) central core and bipyridine (bpy) terminal substituents, are able to self-organize. They are investigated by scanning tunneling microscopy at the solid-liquid interface. Upon light irradiation, cooperative photochromic switching of the ligands is recognized down to the submolecular level. The closed isomers show different electron density of states (DOS) contrasts, attributed to the HOMO or LUMO molecular orbitals observed. More importantly, the LUMO images show remarkable differences between the open and closed isomers, attributed to combined topographic and electronic contrasts mainly on the DAE moieties. The electronic contrasts from multiple HOMO or LUMO distributions, combined with topographic distortion of the open or closed DAE, are interpreted by density functional theory (DFT) calculations.