Ligand effects on charge transport in platinum(II) acetylides

Abstract

To investigate the electrical characteristics of organometallic complexes as molecular conductors, organometallic π-conjugated molecules of the type trans-[PtL₂(C_≡CC₆H₄SAc-4)₂], where L=PCy₃, PBu₃, PPh₃, P(OEt)₃, P(OPh)₃, were synthesized and characterized by NMR, IR, UV, and X-ray spectroscopies. For the three complexes (L=PCy₃, PPh₃, and P(OEt)₃) that could be measured using a cross-wire junction technique, the current-voltage (I-V) characteristics of a molecular monolayer of these complexes showed no ligand effect, despite spectroscopic evidence that electronic interaction between the phosphine ligands and the π-system does occur. It was concluded that the tunneling efficiency across the molecule is the determining factor for conduction in this metal-molecule-metal system. It was also shown that the incorporation of a transition metal in π -conjugated molecular wires does not adversely affect charge transport compared to all-carbon π -conjugated molecular wires.