SCIENTIFIC HIGHLIGHTS

Boron-(-diketone) compounds foster interplay between applied bias voltage and molecular dipole toward the achievement of bistability conductance measurements

MCBJ measurements show the possibility of having two conductance states in the same trace experiment by studying a boron-curcuminoid compound which different conformations rise to changes in the molecular dipole moment meanwhile measuring providing the observed bistability.

Mechanically-controlled break junction (MCBJ) experiments in a family of curcuminoid molecules (CCMoids) was explored. Single electron transport information was gathered using them as nanowires sandwiched between Au electrodes. The molecular set was formed by CCMoids with different S-based ending groups (MeS-, RS- (R = S-thiocarbamate) and 3-Thiophene-) akin to the electrodes and the coordination compounds achieved by the binding of CuII and BF2 moieties to such organic molecules. The nature of the side groups provided a gradient of conductance values where RS- sites gave conductance values one order of magnitude higher than the MeS- analogs. The coordination to CuII with respect to the free ligand did not provided drastic changes in the electronic transport; however, in the case of the MeS-CCM-BF2 system, the switching between two conductance values in individual traces was observed. The sum of additional MCBJ experiments in an extended family of molecules and the use of theoretical calculations, (providing models of the systems attached to the electrodes) revealed the relationship between the orientation of the dipole moment of the molecules within the junction and the bistability measurements.

Authors
Ignacio José Olavarría-Contreras,1 Alvaro Etcheverry-Berríos,2 Wenjie Qian,3 Cristian Gutiérrez-Cerón,4 Aldo Campos-Olguín,2 E. Carolina Sañudo,5,6 Diana Dulić,4 Eliseo Ruiz,5,7 Núria Aliaga-Alcalde,3,8 Monica Soler2 and Herre S. J. van der Zant1 

Affiliations:
1Kavli Institute of Nanoscience, Delft University of Technology, The Netherlands.
2Departamento de Ingeniería Química, Biotecnología y Materiales, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Chile
3Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain
4Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Chile
5Departament de Química Inorgànica i Orgànica, Universitat de Barcelona, Spain
6Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, Spain
7Institut de Química Teòrica i Computacional, Universitat de Barcelona, Spain
8ICREA (Institució Catalana de Recerca i Estudis Avançats), Spain

Publication:
Electric-field induced bistability in single-molecule conductance measurements for boron coordinated curcuminoid compounds
Chem. Sci. 9, 6988-6996 (2018)
DOI: 10.1039/C8SC02337A

Figure:
Examples of individual breaking traces (using MCBJ technique) of a MeS-CCM-BF2 compound where a switching between two conductance values is observed. The figures in front represent conformations of the molecule sandwiched between Au electrodes and the orientation of its dipole moment, in each case, giving rise to the bistability

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