Modification of Molecular Conductance by in Situ Deprotection of Thiol-Based Porphyrin.
Acetylthio-protected free base porphyrins are used to form scanning tunneling microscope-molecular break junctions. The porphyrin molecules are deprotected in situ, before the self-assembly. Two types of molecular junctions are formed in the junctions: Au-S-Por-SAc-Au and Au-S-Por-S-Au. Lower conductance values and higher conductance values are observed. Computational modeling attributes the lower conductance to the Au-S-Por-SAc-Au junctions and the higher conductance to the Au-S-Por-S-Au junctions. First-principles calculation suggests that the reduced conductance in the protected porphyrin originates from the presence of the acetyl end groups (-COCH3), rather than from the elongation of the sulfur-gold (S-Au) bonds at the tip-molecule interface.
Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute , Troy, New York 12180, United States.
Qi
http://orcid.org/0000-0002-5700-6644
Q
Zhou
Department of Chemistry and Biochemistry, Kent State University , Kent, Ohio 44242, United States.
Atsushi
A
Yamada
Department of Chemistry and Biochemistry, Kent State University , Kent, Ohio 44242, United States.
Qingguo
Q
Feng
Department of Chemistry and Biochemistry, Kent State University , Kent, Ohio 44242, United States.
Austin
A
Hoskins
Department of Chemistry and Biochemistry, Kent State University , Kent, Ohio 44242, United States.
Barry D
http://orcid.org/0000-0002-6982-8995
BD
Dunietz
Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute , Troy, New York 12180, United States.
Kim M
http://orcid.org/0000-0002-8342-8699
KM
Lewis
Green’s function density functional theory; in situ deprotection; molecular break junctions; molecular conductance; porphyrin; scanning tunneling microscope