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Issue 17, 2015
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Synthesis, characterization, and physical properties of oligo(1-(N,N-dimethylamino)pyrrole)s and their doped forms, precursors of candidates for molecular flat-band ferromagnets

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Abstract

Fully oxidized poly(1-(N,N-dimethylamino)pyrrole)s (PDMAPyn+), which are synthesized through doping with anions with the same number of polymer units as the original pyrrole, have been proposed as candidates for molecular flat-band magnets from the theoretical calculations of Aoki and coworkers (Phys. Rev. B: Condens. Matter Mater. Phys., 2003, 68, 140403; Phys. Rev. B: Condens. Matter Mater. Phys., 2010, 82, 235127). Here we describe the synthesis of neutral forms of oligo(1-(N,N-dimethylamino)pyrrole)s (ODMAPys) from the dimer (2) to the dodecamer (12). The crystal structures of 2–6 (i.e., up to the hexamer) were determined by single crystal X-ray analysis. The chemical and electrochemical formation of their oxidized forms is also reported. Electrochemical measurements of the ODMAPys indicated that oligomers 4, 6, and 8 underwent 2e oxidation, whereas 10 and 12 showed quasi-reversible 4e oxidation. The oxidized forms maintained considerable chemical stability; 42+, 62+, 82+, 104+, and 124+ were isolated as SbCl6 salts. The neutral forms were colorless (λmax = 240–270 nm), whereas the oxidized forms exhibited strong blue color with λmax = 670–950 nm. EPR spectroscopy indicated that the dications 42+, 62+, and 82+ in the solid salts were intrinsically diamagnetic, but the tetracation of 104+ was paramagnetic at 4.4 K, which was supported by magnetic measurements. These physical properties of the ODMAPys are different from those common to polypyrroles, but consistent with their predicted unique electronic structures.

Graphical abstract: Synthesis, characterization, and physical properties of oligo(1-(N,N-dimethylamino)pyrrole)s and their doped forms, precursors of candidates for molecular flat-band ferromagnets

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Publication details

The article was received on 23 Dec 2014, accepted on 18 Mar 2015 and first published on 19 Mar 2015


Article type: Paper
DOI: 10.1039/C4TC02941K
Citation: J. Mater. Chem. C, 2015,3, 4316-4320
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    Synthesis, characterization, and physical properties of oligo(1-(N,N-dimethylamino)pyrrole)s and their doped forms, precursors of candidates for molecular flat-band ferromagnets

    Y. Yamanoi, K. Takahashi, T. Hamada, N. Ohshima, M. Kurashina, Y. Hattori, T. Kusamoto, R. Sakamoto, M. Miyachi and H. Nishihara, J. Mater. Chem. C, 2015, 3, 4316
    DOI: 10.1039/C4TC02941K

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