Molecular wires (MW) are the fundamental building blocks for
molecular electronic devices. The simplest definition for a MW
is a single molecular unit connected to two continuum reservoirs
of electrons (usually metallic leads). Modeling electron
transport in this coupled system is a complex problem uniting
methods from both chemistry and physics. We rely on Landauer
theory as the basis for studying the conductance properties of
MW systems. This relates the lead to lead current to the
transmission probability for an electron to scatter through the
molecule via the finite voltage, finite temperature Landauer
formula. Two different methods have been developed for the study
of this scattering. One is based on a solution of the Lippmann-
Schwinger equation and the other solves for the t matrix using
Schroedinger's equation. In both methods the chemistry of the
molecule and the binding of it to the leads is modeled using the
extended Huckel tight binding scheme. Using these two methods we
have been able to calculate