Investigation of the geometrical arrangement and single molecule charge transport in self-assembled monolayers of molecular towers based on tetraphenylmethane tripod

Multipodal molecular platforms were designed recently to establish a well-defined contact between molecular electronic components and metallic electrodes to manufacture working devices based on molecular electronics. In this work, we use electrochemical techniques, scanning tunneling microscopy break junction technique and theoretical approaches combining density functional theory (DFT) and non-equilibrium Green's function (NEGF) formalism to investigate the geometrical arrangement and single molecule charge transport in self-assembled monolayers (SAMs) of molecular towers anchored by tetraphenylmethane tripod on Au (111) surface. The effect of the molecular length as well as the role of the position of anchoring groups was addressed. Electrochemical double-layer capacitance measurements and reductive desorption studies combined with theoretical modeling clearly demonstrated that the molecular towers form densely packed SAMs, in which the individual molecules are attached to the Au (111) surface by the tripodal base and the principal molecular axis is directed away from the electrode surface, providing thus desired orientation. Temperature resolved single molecule conductance measurements combined with DFT/NEGF calculations showed that the electric charge is transported by tunneling via highly conductive molecular junctions formed by the tripodal base. Our combined experimental and theoretical work demonstrates that tetraphenylmethane tripods are suitable platforms to bear functional groups serving as molecular electronic components.