Spin-Crossover in Supramolecular Iron(II)-2,6-bis(1 H-Pyrazol-1-yl)pyridine Complexes
Toward Spin-State Switchable Single-Molecule Junctions
Senthil Kumar Kuppusamy (Karlsruhe Institut für Technologie)
Asato Mizuno (Karlsruhe Institut für Technologie)
Amador García-Fuente (Universidad de Oviedo)
S. van der Poel (Kavli institute of nanoscience Delft, TU Delft - QN/van der Zant Lab)
Benoît Heinrich (Institut de Physique et Chimie des Matériaux de Strasbourg)
Jaime Ferrer (Universidad de Oviedo)
H.S.J. van der Zant (TU Delft - QN/van der Zant Lab, Kavli institute of nanoscience Delft)
Mario Ruben (Karlsruhe Institut für Technologie, University of Strasbourg)
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Abstract
Spin-crossover (SCO) active iron(II) complexes are an integral class of switchable and bistable molecular materials. Spin-state switching properties of the SCO complexes have been studied in the bulk and single-molecule levels to progress toward fabricating molecule-based switching and memory elements. Supramolecular SCO complexes featuring anchoring groups for metallic electrodes, for example, gold (Au), are ideal candidates to study spin-state switching at the single-molecule level. In this study, we report on the spin-state switching characteristics of supramolecular iron(II) complexes 1 and 2 composed of functional 4-([2,2′-bithiophen]-5-ylethynyl)-2,6-di(1H-pyrazol-1-yl)pyridine (L1) and 4-(2-(5-(5-hexylthiophen-2-yl)thiophen-2-yl)ethynyl)-2,6-di(1H-pyrazol-1-yl)pyridine (L2) ligands, respectively. Density functional theory (DFT) studies revealed stretching-induced spin-state switching in a molecular junction composed of complex 1, taken as a representative example, and gold electrodes. Single-molecule conductance traces revealed the unfavorable orientation of the complexes in the junctions to demonstrate the spin-state dependence of the conductance.
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