Electric-field induced bistability in single-molecule conductance measurements for boron coordinated curcuminoid compounds

Electric-field induced bistability in single-molecule conductance measurements for boron coordinated curcuminoid compounds

Olavarria Contreras, I.J. (TU Delft QN/van der Zant Lab; Kavli institute of nanoscience Delft)
Etcheverry-Berríos, Alvaro (Universidad de Chile)
Qian, Wenjie (Universitat Autònoma de Barcelona)
Gutiérrez Cerón, C.A. (Universidad de Chile)
Campos-Olguín, Aldo (Universidad de Chile)
Sañudo, E. Carolina (Universitat Politecnica de Catalunya)
Dulić, Diana (Universidad de Chile)
Ruiz, Eliseo (Universitat Politecnica de Catalunya)
Aliaga-Alcalde, Núria (Universitat Autònoma de Barcelona; Catalan Institution for Research and Advanced Studies (ICREA))
Soler, Monica (Universidad de Chile)
van der Zant, H.S.J. (TU Delft QN/van der Zant Lab; Kavli institute of nanoscience Delft)

2018

We have studied the single-molecule conductance of a family of curcuminoid molecules (CCMs) using the mechanically controlled break junction (MCBJ) technique. The CCMs under study contain methylthio (MeS-) as anchoring groups: MeS-CCM (1), the free-ligand organic molecule, and two coordination compounds, MeS-CCM-BF₂ (2) and MeS-CCM-Cu (3), where ligand 1 coordinates to a boron center (BF₂ group) and to a Cu^II moiety, respectively. We found that the three molecules present stable molecular junctions allowing detailed statistical analysis of their electronic properties. Compound 3 shows a slight increase in the conductance with respect to free ligand 1, whereas incorporation of BF₂ (compound 2) promotes the presence of two conductance states in the measurements. Additional experiments with control molecules point out that this bistability is related to the combination of MeS- anchoring groups and the BF₂ moiety within the structure of the molecules. Theoretical calculations show that this can be explained by the presence of two conformers once compound 2 is anchored between the gold electrodes. An energy minimum is found for a flat structure but there is a dramatic change in the magnitude and orientation of dipole moment (favouring a non-flat conformer in the presence of an external electric field) due to a conformational change of one of the terminal MeS- groups. The results thus point to an intricate interplay between the applied bias voltage and the molecule dipole moment which could be the basis for designing new molecules aiming at controlling their conformation in devices.

http://resolver.tudelft.nl/uuid:38a03746-b46f-42aa-b6de-9d815ef5d801

https://doi.org/10.1039/c8sc02337a

2041-6520

Chemical Science, 9 (34), 6988-6996

Institutional Repository

journal article

© 2018 I.J. Olavarria Contreras, Alvaro Etcheverry-Berríos, Wenjie Qian, C.A. Gutiérrez Cerón, Aldo Campos-Olguín, E. Carolina Sañudo, Diana Dulić, Eliseo Ruiz, Núria Aliaga-Alcalde, Monica Soler, H.S.J. van der Zant