title: Exponential Attenuation of Through-Bond Transmission in a Polyene: Theory and Potential Realizations.
abstract: An exponential falloff with separation of electron transfer and transport through molecular wires is observed and has attracted theoretical attention. In this study, the attenuation of transmission in linear and cyclic polyenes is related to bond alternation. The explicit form of the zeroth Green's function in a Hückel model for bond-alternated polyenes leads to an analytical expression of the conductance decay factor β. The β values calculated from our model (β(CN) values, per repeat unit of double and single bond) range from 0.28 to 0.37, based on carotenoid crystal structures. These theoretical β values are slightly smaller than experimental values. The difference can be assigned to the effect of anchoring groups, which are not included in our model. A local transmission analysis for cyclic polyenes, and for [14]annulene in particular, shows that bond alternation affects dramatically not only the falloff behavior but also the choice of a transmission pathway by electrons. Transmission follows a well-demarcated system of π bonds, even when there is a shorter-distance path with roughly the same kind of "electronic matter" intervening.
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University , Baker Laboratory, Ithaca, New York 14853, United States.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Tsuji
authors.affiliation: Department of Mathematics, Massachusetts Institute of Technology , Building E18, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, United States.
authors.forename: Ramis
authors.initials: R
authors.lastname: Movassagh
authors.affiliation: School of Electrical and Computer Engineering, Purdue University , Electrical Engineering Building, 465 Northwestern Avenue, West Lafayette, Indiana 47907-2035, United States.
authors.forename: Supriyo
authors.initials: S
authors.lastname: Datta
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University , Baker Laboratory, Ithaca, New York 14853, United States.
authors.forename: Roald
authors.initials: R
authors.lastname: Hoffmann
keywords: annulenes; bond alternation; exponential falloff; molecular transmission