Bottom-up Fabrication and Atomic-scale Characterization of Triply-linked, Laterally π-Extended Porphyrin Nanotapes

Porphyrin nanotapes (Por NTs) are highly promising structures for their use as molecular wires thanks to their high degree of π-conjugation, low HOMO-LUMO gaps, and exceptional conductance. Such structures have been repeatedly reported in solution-based approaches, but their on-surface synthesis, which allows an atomically-resolved characterization, remains unreported to this date. Here, we report the first example of meso-meso triply-fused Por NTs, which are prepared from a readily available Por precursor through a two-step synthesis on Au(111). The diradical character of the on-surface formed building block PorA 2 , a phenalenyl π-extended Zn(II)Por, facilitates intermolecular homocoupling and allows for the formation of laterally π-extended tapes. The structural and electronic properties of individual Por NTs are addressed, both on Au(111) and on a thin insulating NaCl layer, by high-resolution scanning probe microscopy/spectroscopy complemented by density functional theory calculations. Remarkably, the triply-linked, laterally π-extended Por NTs carry one unpaired electron at each end, which leads to magnetic end states. Our study provides an alternative and versatile route to the fabrication of Por NTs and the atomic-scale characterizations of their structural and electronic properties.