Dipole moments of polyenic oligomeric systems. Part II - Molecular organic wire resistivities: Polyacetylenes, allenes and polyynes

Polyacetylenic, allenic and polyynic molecular wire series, containing electron-donor (D) and electron-acceptor (A) groups as two terminal units of the oligomeric bridge (D-wire-A), can be well described by means of a one-dimensional conduction model, which considers a scattering process of electrons through the charge-transfer conduction bridge. The conduction constants (γ_i) of the oligomeric structures of the three molecular series under study were determined from the functional dependence between the dipole moment of the oligomers (μ_n) and the π-molecular orbital bridge length (L). According to our one-dimensional molecular organic wire model: μ_n = μ_o + μ_∞ (1 - e^-γL) where μ_o is the dipolar moment of the first compound of the oligomeric series without a bridge unit (n = 0) and μ_∞ is a limit value for L → ∞. By means of the Landauer theoretical expression for the conductance of a metallic one-dimensional conductor and our molecular wire conduction constants (γ_i), we determined the intrinsic resistivities associated with the molecular resistances of these oligomeric wires. Using this approach we determined, for the first time, the linear and non-linear contributions to the net molecular resistivity. The order of magnitudes of the linear resistivities determined in these oligomeric systems agrees very well with the expected results of experimental measurements for macroscopic wires.