• Lambert, Colin John
• Xu, W.
• Hou, S.
• Leary, E.
• Christensen, K. E.
• González, M. T.
• Wu, Qingqing
• Agraït, N.
• Sangtarash, Sara
• Nichols, R. J.
• Tejerina, L.
• Sadeghi, Hatef
• Higgins, S. J.
• Anderson, H. L.
• Rubio-Bollinger, G.

Abstract

Cumulenes are sometimes described as “metallic” because an infinitely long cumulene would have the band structure of a metal. Herein, we report the single‐molecule conductance of a series of cumulenes and cumulene analogues, where the number of consecutive C=C bonds in the core is n=1, 2, 3, and 5. The [n]cumulenes with n=3 and 5 have almost the same conductance, and they are both more conductive than the alkene (n=1). This is remarkable because molecular conductance normally falls exponentially with length. The conductance of the allene (n=2) is much lower, because of its twisted geometry. Computational simulations predict a similar trend to the experimental results and indicate that the low conductance of the allene is a general feature of [n]cumulenes where n is even. The lack of length dependence in the conductance of [3] and [5]cumulenes is attributed to the strong decrease in the HOMO–LUMO gap with increasing length.

Topics

• impedance spectroscopy
• simulation
• wire
• band structure
• alkene