On-Surface Synthesis of Rigid Benzenoid- and Nonbenzenoid-Coupled Porphyrin–Graphene Nanoribbon Hybrids

Abstract

On-surface synthesis made the fabrication of extended, atomically precise π-conjugated nanostructures on solid supports possible, with graphene nanoribbons (GNRs) and porphyrin-derived oligomers standing out. To date, examples combining these two prominent material classes are scarce, even though the chemically versatile porphyrins and the atomistic details of the nanographene spacers promise an easy tunability of structural and functional properties of the resulting hybrid structures. Here, we report the on-surface synthesis of extended benzenoid- and nonbenzenoid-coupled porphyrin–graphene nanoribbon hybrids by sequential Ullmann-type and cyclodehydrogenation reactions of a tailored Zn­(II) 5,15-bis­(5-bromo-1-naphthyl)­porphyrin (Por­(BrNaph)2) precursor on Au(111) and Ag(111). Using bond-resolved noncontact atomic force microscopy (nc-AFM) and scanning tunneling microscopy (STM), we characterize the structures of reaction intermediates and products in detail and provide insight into the effects of the annealing protocol. We further demonstrate the stability and rigidity of the extended one-dimensional porphyrin–GNR oligomers by employing an STM-based manipulation procedure, which allows for spectroscopic measurement upon lifting.

On-surface synthesis of non-benzenoid conjugated polymers by selective atomic rearrangement of ethynylarenes

“…Nevertheless, there are only a few reports discussing the on-surface formation of non-benzenoid moieties, 18,[25][26][27][28][29] sometimes in conjugated polymers. 8,21,[30][31][32][33][34][35] Most of them have utilized strategies based on oxidative ring closure, 8,36 bond rotation 37 or the use of molecular precursors with embedded 5-membered rings. 38,39 Therefore, it is highly desirable to provide new strategies that allow the controlled formation and detailed analysis of such non-benzenoid molecules.…”

Tunable spin and conductance in porphyrin-graphene nanoribbon hybrids

“…Recently, several research groups have attempted to expand the synthetic 1D complexes including porphyrin cores in different ways 17,18 . The structures considered so far, both in experimental and theoretical works, have mainly been porphyrin oligomers/ polymers 19 , or porphyrin nanotapes 20 , which lack the GNRs segments as a backbone. Only finite nanostructures with two metal-free (H 2 ) Pors connected by a short GNR segment have been synthesized on surface by Mateo et al 21 .…”