Close relation between quantum interference in molecular conductance and diradical existence

Yuta Tsuji, Roald Hoffmann, Mikkel Strange, Gemma C. Solomon

Research output: Contribution to journalArticlepeer-review

48 Citations (Scopus)

Abstract

An empirical observation of a relationship between a striking feature of electronic transmission through a π-system, destructive quantum interference (QI), on one hand, and the stability of diradicals on the other, leads to the proof of a general theorem that relates the two. Subject to a number of simplifying assumptions, in a π-electron system, QI occurs when electrodes are attached to those positions of an N-carbon atom N-electron closed-shell hydrocarbon where the matrix elements of the Green's function vanish. These zeros come in two types, which are called easy and hard. Suppose an N+2 atom, N+2 electron hydrocarbon is formed by substituting 2 CH2 groups at two atoms, where the electrodes were. Then, if a QI feature is associated with electrode attachment to the two atoms of the original N atom system, the resulting augmented N+2 molecule will be a diradical. If there is no QI feature, i.e., transmission of current is normal if electrodes are attached to the two atoms, the resulting hydrocarbon will not be a diradical but will have a classical closed-shell electronic structure. Moreover, where a diradical exists, the easy zero is associated with a nondisjoint diradical, and the hard zero is associated with a disjoint one. A related theorem is proven for deletion of two sites from a hydrocarbon.

Original languageEnglish
Pages (from-to)E413-E419
JournalProceedings of the National Academy of Sciences of the United States of America
Volume113
Issue number4
DOIs
Publication statusPublished - Jan 26 2016

All Science Journal Classification (ASJC) codes

  • General

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