Odd-even effect in molecular electronic transport via an aromatic ring

Tal Toledano, Haim Sazan, Sabyasachi Mukhopadhyay, Hadas Alon, Keti Lerman, Tatyana Bendikov, Dan T. Major, Chaim N. Sukenik, Ayelet Vilan, David Cahen

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


A distinct odd-even effect on the electrical properties, induced by monolayers of alkyl-phenyl molecules directly bound to Si(111), is reported. Monomers of H2C=CH-(CH2)n-phenyl, with n = 2-5, were adsorbed onto Si-H and formed high-quality monolayers with a binding density of 50-60% Si(111) surface atoms. Molecular dynamics simulations suggest that the binding proximity is close enough to allow efficient π-π interactions and therefore distinctly different packing and ring orientations for monomers with odd or even numbers of methylenes in their alkyl spacers. The odd-even alternation in molecular tilt was experimentally confirmed by contact angle, ellipsometry, FT-IR, and XPS with a close quantitative match to the simulation results. The orientations of both the ring plane and the long axis of the alkyl spacer are more perpendicular to the substrate plane for molecules with an even number of methylenes than for those with an odd number of methylenes. Interestingly, those with an even number conduct better than the effectively thinner monolayers of the molecules with the odd number of methylenes. We attribute this to a change in the orientation of the electron density on the aromatic rings with respect to the shortest tunneling path, which increases the barrier for electron transport through the odd monolayers. The high sensitivity of molecular charge transport to the orientation of an aromatic moiety might be relevant to better control over the electronic properties of interfaces in organic electronics.

Original languageEnglish
Pages (from-to)13596-13605
Number of pages10
Issue number45
StatePublished - 18 Nov 2014

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© 2014 American Chemical Society.


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