The I-V curves are computed for 2,7-dithiolpyrene and 4,4'-dithiol-diphenylacetylene between two Au(1 1 1) surfaces. For a given bias, up to about 2.5 eV. the current for 2,7-dithiolpyrene is about half that for 4,4'-dithiol-diphenylacetylene. However, the fused benzene rings in 2,7-dithiolpyrene eliminate the loss of current associated with rotation about the central C-2 that can occur for 4,4'-dithiol-diphenylacetylene. (C) 2004 Elsevier B.V. All rights reserved.