Semiconductive coordination networks from 2,3,6,7,10,11-hexakis(alkylthio)triphenylenes and bismuth(III) halides: Synthesis, structure-property relations, and solution processing

This paper reports our initial efforts to promote electronic communications across polycyclic aromatic molecules through intervening metal halide moieties. Such efforts stand as part of the larger scheme to overcome the limitation of the van der Waals barrier in molecular semiconductors. In particular, the polycyclic aromatic ligands of 2,3,6,7,10,11-hexakis(alkylthio)triphenylene (alkyl: methyl, ethyl, and isopropyl; corresponding abbreviations for the molecules, HMTT, HETT, and HiPTT) were synthesized in an improved method, and interacted with bismuth(III) bromide and chloride to produce in high yields of a series of semiconductive hybrid networks featuring flexible network dimensionalities and electronic properties, as well as promising solution processing properties. Enlarging the side group from methyl to ethyl and to isopropyl groups effectively reduces the dimensionality of the bismuth halide components (and consequently the dimensionality of the overall coordination framework). Solid-state optical absorption measurements indicate effective electronic interactions between the organic pi-system and the bismuth trihalide component, and the electronic band gap decreases monotonically with increasing dimensionality of the coordination network. As compared to molecular semiconductors, these integrated hybrid networks feature stronger electronic communication across the organic molecules, and point to potentially higher charge carrier mobilities.