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Air-Stable Thin Films with High and Anisotropic Electrical Conductivities Composed of a Carbon-Centered Neutral π‑Radical

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journal contribution
posted on 09.10.2019, 08:30 by Hiroshi Ito, Tsuyoshi Murata, Takahiro Miyata, Miwa Morita, Ryotaro Tsuji, Yasushi Morita
Air-stable thin films (50–720 nm thickness) composed of a carbon-centered neutral π-radical with high and anisotropic electrical conductivities were fabricated by vapor deposition of 4,8,12-trioxotriangulene (TOT). The thin films were air-stable over 15 months and were the aggregate of TOT microcrystals, in which a one-dimensional π-stacking column was formed through the strong singly occupied molecular orbital (SOMO)–SOMO interaction with two-electron-multicenter bond among the spin-delocalized π-planes. The orientations of the one-dimensional column of TOT were changed depending on the deposition rate and substrates, where face-on-oriented thin films were epitaxially grown on the graphite 0001 surface, and edge-on-oriented thin films were grown on glass, SiO2, and indium tin oxide substrates under a high-deposition rate condition. The films showed high electrical conductivities of 2.5 × 10–2 and 5.9 × 10–5 S cm–1 along and perpendicular to the π-stacking column, respectively, for an edge-on oriented thin film.