Single Molecule Conductance of Porphyrin Wires with Ultralow Attenuation

Abstract

A series of thioacetate-terminated butadiyne-linked porphyrin oligomers have been synthesized with one to three porphyrin repeat units. Single molecule electrical scanning tunneling microscopy measurements using the I(s) and I(t) methods were used to determine the molecule conductances for this series of oligomers. The molecular conductance shows an exponential falloff with sulfur-sulfur distance with a remarkably low attenuation factor of beta = (0.04 +/- 0.006) A-1.

Metal complexes in molecular junctions

“…Wires up to 5 nm incorporating Zn porphyrins were also found to display very low attenuation factors (0.4 nm −1 ). 8 …”

Electrical characteristics of conjugated self-assembled monolayers in large-area molecular junctions

“…2 Studies on various -conjugated molecules have been performed. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] The molecules, with delocalized electrons due to sp 2 hybridized carbon atoms, exhibit a smaller energy gap between the highest occupied molecular orbital ͑HOMO͒ and the lowest unoccupied molecular orbital ͑LUMO͒. For -conjugated molecules longer than ϳ3 nm hopping conduction was observed.…”

Resonant transport and electrostatic effects in single-molecule electrical junctions

“…1); electron-donating substituents (Me−, MeO−) resulted in significantly higher junction conductances and the electron-deficient C 6 F 4 group resulted in a lower conductance [18]. Many studies of metal-molecule-metal junctions have probed the molecular structural requirements for obtaining high junction conductance [19][20][21][22][23][24][25][26][27][28].…”