Magnetic Edge State of Nanographene and Unconventional Nanographene-Based Host–Guest Systems

• Toshiaki Enoki

  Department of Chemistry, Tokyo Institute of Technology

• Kazuyuki Takai

  Department of Chemistry, Tokyo Institute of Technology

• Manabu Kiguchi

  Department of Chemistry, Tokyo Institute of Technology

Abstract

Nanographene, nanosized fragments of graphene, has edge-shape-dependent electronic structures different from those of infinite size graphene. Around the zigzag-shaped edges of a nanographene sheet, a nonbonding edge state of π-electron origin is created, which is the origin of electronic and chemical activities of nanographene. In addition, the strongly spin-polarized edge state has localized spin, giving magnetic activity. We investigate the magnetic properties of nanoporous activated carbon fibers consisting of a three-dimensional disordered network of nanographite domains, each of which is a stack of 3–4 nanographene sheets, in relation to host–guest interaction. Chemically inert guest species such as water, organic solvent, or argon, physisorptively condensed into the nanopores mechanically compress the nanographite domains, resulting in high spin/low spin magnetic switching of the edge-state spins. The presence of an energy gap and the nanographene edges decorated by oxygen-containing functional groups make nanographene less amphoteric, modifying charge-transfer mechanisms in the host–guest interaction. HNO3 shows a two-step charge-transfer process. In Br adsorption, physisorbed Br species cooperate with charge-transfer Br species, giving an interesting interplay of charge transfer and magnetic switching phenomena. In the K adsorption, physisorbed K atoms form antiferromagnetic K clusters in the nanopores, while a portion of K species are responsible for charge transfer. The reaction with fluorine creates magnetic σ-dangling bond states, at the expense of the π-conjugated electron system. The interplay between the edge-state spins and the σ-dangling bond spins gives a variety of magnetism depending on the fluorine concentration.

Journal

• Bulletin of the Chemical Society of Japan

  Bulletin of the Chemical Society of Japan 85 (3), 249-264, 2012-02-23

  Oxford University Press (OUP)

Keywords

• General Chemistry

Details

• CRID: 1360846644026968832
• NII Article ID: 130004153040
• DOI: 10.1246/bcsj.20110236
• ISSN: 13480634
• ISSN: 00092673
• Web Site: https://academic.oup.com/bcsj/article-pdf/85/3/249/56273882/bcsj.20110236.pdf
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