A small molecule walks along a surface between porphyrin fences that are assembled in situ.
An on-surface bimolecular system is described, comprising a simple divalent bis(imidazolyl) molecule that is shown to "walk" at room temperature via an inchworm mechanism along a specific pathway terminated at each end by oligomeric "fences" constructed on a monocrystalline copper surface. Scanning tunneling microscopy shows that the motion of the walker occurs along the [110] direction of the Cu surface with remarkably high selectivity and is effectively confined by the orthogonal construction of covalent porphyrin oligomers along the [001] surface direction, which serve as barriers. Density functional theory shows that the mobile molecule walks by attaching and detaching the nitrogen atoms in its imidazolyl "legs" to and from the protruding close-packed rows of the metal surface and that it can transit between two energetically equivalent extended and contracted conformations by overcoming a small energy barrier.
Surface Science Research Centre, Department of Chemistry, University of Liverpool, Liverpool L69 3BX (UK).
Sam
S
Haq
Surface Science Research Centre, Department of Chemistry, University of Liverpool, Liverpool L69 3BX (UK).
Bareld
B
Wit
School of Physics and Technology, Center for Electron Microscopy and MOE, Key Laboratory of Artificial Micro- and Nano-structures, Wuhan University, Wuhan 430072 (China).
Hongqian
H
Sang
Physics Department, King's College London, Strand, London, SE2 0LR (UK).
Andrea
A
Floris
School of Physics and Technology, Center for Electron Microscopy and MOE, Key Laboratory of Artificial Micro- and Nano-structures, Wuhan University, Wuhan 430072 (China).
Yu
Y
Wang
School of Physics and Technology, Center for Electron Microscopy and MOE, Key Laboratory of Artificial Micro- and Nano-structures, Wuhan University, Wuhan 430072 (China).
Jianbo
J
Wang
Laboratori de Química Orgànica, Facultat de Farmàcia and Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028 Barcelona (Catalonia, Spain).
Lluïsa
L
Pérez-García
Physics Department, King's College London, Strand, London, SE2 0LR (UK). lev.kantorovitch@kcl.ac.uk.
Lev
L
Kantorovitch
Institut de Ciència de Materials de Barcelona (CSIC), Campus Universitari, 08193 Bellaterra (Catalonia, Spain). David.Amabilino@nottingham.ac.uk.|Present address: School of Chemistry, The University of Nottingham, University Park, Nottingham NG7 2RD (UK). David.Amabilino@nottingham.ac.uk.
David B
DB
Amabilino
Surface Science Research Centre, Department of Chemistry, University of Liverpool, Liverpool L69 3BX (UK). raval@liv.ac.uk.
Rasmita
R
Raval
D003300:Copper / Q000737:chemistry; D016252:Microscopy, Scanning Tunneling; D049329:Nanostructures / Q000737:chemistry; D011166:Porphyrins / Q000737:chemistry*; D013499:Surface Properties
D011166:Porphyrins; D003300:Copper
diffusion; molecular machines; nanomaterials; scanning tunneling microscopy; surface chemistry