Room temperature conductance switching in a molecular iron(iii) spin crossover junction

Senthil Kumar Karuppannan; Alejandro Martín-Rodríguez; Eliseo Ruiz; Phimphaka Harding; David J Harding; Xiaojiang Yu; Anton Tadich; Bruce Cowie; Dongchen Qi; Christian A Nijhuis

doi:10.1039/d0sc04555a

Room temperature conductance switching in a molecular iron(iii) spin crossover junction

Chem Sci. 2020 Nov 10;12(7):2381-2388. doi: 10.1039/d0sc04555a.

Authors

Affiliations

¹ Department of Chemistry, National University of Singapore 3 Science Drive Singapore 117543 Singapore chmnca@nus.edu.sg.
² Departament de Química Inorgànica, Institut de Recerca de Química Teòrica i Computacional, Universitat de Barcelona Diagonal 645 08028 Barcelona Spain eliseo.ruiz@qi.ub.edu.
³ Functional Materials and Nanotechnology Center of Excellence, Walailak University Thasala Nakhon Si Thammarat 80160 Thailand kphimpha@mail.wu.ac.th hdavid@mail.wu.ac.th.
⁴ Singapore Synchrotron Light Source, National University of Singapore 5 Research Link Singapore 117603 Singapore.
⁵ Australian Synchrotron Clayton Victoria 3168 Australia.
⁶ School of Chemistry and Physics, Queensland University of Technology Brisbane Queensland 4001 Australia.
⁷ Centre for Advanced 2D Materials & Graphene Research, National University of Singapore 6 Science Drive 2 Singapore 117546 Singapore.

Abstract

Herein, we report the first room temperature switchable Fe(iii) molecular spin crossover (SCO) tunnel junction. The junction is constructed from [Fe^III(qsal-I)₂]NTf₂ (qsal-I = 4-iodo-2-[(8-quinolylimino)methyl]phenolate) molecules self-assembled on graphene surfaces with conductance switching of one order of magnitude associated with the high and low spin states of the SCO complex. Normalized conductance analysis of the current-voltage characteristics as a function of temperature reveals that charge transport across the SCO molecule is dominated by coherent tunnelling. Temperature-dependent X-ray absorption spectroscopy and density functional theory confirm the SCO complex retains its SCO functionality on the surface implying that van der Waals molecule-electrode interfaces provide a good trade-off between junction stability while retaining SCO switching capability. These results provide new insights and may aid in the design of other types of molecular devices based on SCO compounds.