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Unusual Length Dependence of the Conductance in Cumulene Molecular Wires
Author(s) -
Xu Wenjun,
Leary Edmund,
Hou Songjun,
Sangtarash Sara,
González M. Teresa,
RubioBollinger Gabino,
Wu Qingqing,
Sadeghi Hatef,
Tejerina Lara,
Christensen Kirsten E.,
Agraït Nicolás,
Higgins Simon J.,
Lambert Colin J.,
Nichols Richard J.,
Anderson Harry L.
Publication year - 2019
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201901228
Subject(s) - cumulene , allene , conductance , chemistry , alkene , molecule , homo/lumo , stereochemistry , computational chemistry , crystallography , chemical physics , physics , organic chemistry , condensed matter physics , catalysis
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.