Stretching-Induced Conductance Increase in a Spin-Crossover Molecule.

Frisenda, Riccardo; Harzmann, Gero D; Celis Gil, Jose A; Thijssen, Joseph M; Mayor, Marcel; van der Zant, Herre S J · Nano Lett · 2016

basic_science · Level V

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Abstract

We investigate transport through mechanically triggered single-molecule switches that are based on the coordination sphere-dependent spin state of Fe(II)-species. In these molecules, in certain junction configurations the relative arrangement of two terpyridine ligands within homoleptic Fe(II)-complexes can be mechanically controlled. Mechanical pulling may thus distort the Fe(II) coordination sphere and eventually modify their spin state. Using the movable nanoelectrodes in a mechanically controlled break-junction at low temperature, current-voltage measurements at cryogenic temperatures support the hypothesized switching mechanism based on the spin-crossover behavior. A large fraction of molecular junctions formed with the spin-crossover-active Fe(II)-complex displays a conductance increase for increasing electrode separation and this increase can reach 1-2 orders of magnitude. Theoretical calculations predict a stretching-induced spin transition in the Fe(II)-complex and a larger transmission for the high-spin configuration.