Single Molecule Junction of Polynuclear Alkynylplatinum-Based Organometallic Molecular Wires: A Theoretical Study of the Long-Range Transport Effect of Linkage to Gold Surfaces

Abstract

Density functional theory (DFT) and nonequilibrium Green’s function (NEGF) calculations were employed to elucidate the single-molecule conductance properties of a series of polynuclear alkynylplatinum-based organometallic wires, AcS[[(p-tol₃P)₂PtC≡C–C≡C–C≡C–C≡C]_mPt(Pp-tol₃)₂SAc (m = 1–3), featuring platinum centers incorporated within polyyne chains. This investigation aimed to determine the influence of the embedded platinum centers on conductance compared to all-carbon polyynes and organometallic wires with terminal metal entities. While the structural and electronic properties of the individual molecular units are minimally affected by the chain extension, DFT-NEGF calculations on the corresponding Au-wire-Au junctions reveal an exponential decay in conductance with increasing molecular length, consistent with a tunneling-dominated transport mechanism. However, for longer wires (m = 3), the markedly low conductance and partial localization of frontier orbitals indicate that hopping transport could contribute to the overall transport mechanism. These findings provide valuable insights into the factors governing charge transport, including the interplay of length, platinum incorporation, and orbital localization in polynuclear alkynylplatinum-based organometallic wires, which may have implications for the future design of molecular wires.