Investigations of conductance of photochromic switching molecules

Recent experimental work has confirmed a dramatic conductance enhancement of more than two orders of magnitude after the optical switching between two molecular isomers of a dithienylethene-derivative on gold. To determine which dithienylethene-derivative may be the optimal candidate for use as an optical molecular switch, it is necessary to understand the nature of the conductance switching. To this end, a variety of theoretical tools were employed to study the critical aspects of this unique metal-molecule-metal junction. A plane wave based density functional method revealed marked differences between the two isomers with regard to the line-up of the molecular states and the contact states. A local orbital based density functional method was used to generate a tractable Hamiltonian for a Landauer based transport calculation. Three different derivatives are analyzed to determine which may be an appropriate candidate in a molecular electronic device. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.