Side-chain effects in molecular electronic devices

We discuss the effect of an abundant structural element of molecules on the transmission probabilities of molecular electronic devices. We show that an attachment of side chains to a molecular conductor may lead to zero transmission probabilities. The gaps in the transmission-probability appear approximately at the eigenvalues of the isolated side chains, provided that the corresponding eigenstates are not localized away from the molecular conductor. Simple Huckel-type calculations serve to illustrate the described effect. Furthermore, we show that complex transmission-probability curves, obtained with Kohn-Sham density-functional theory, also exhibit the described side-chain effect. (c) 2005 American Institute of Physics.