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Issue 4, 2018
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Crystal structure and physical properties of radical cation salt based on 4,5-ethylenedioxy-4′-iodotetrathiafulvalene (EDO-TTF-I) with iodine bonding ability

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Abstract

Single crystals of 4,5-ethylenedioxy-4′-iodotetrathiafulvalene (EDO-TTF-I) with iodine bonding ability were obtained by recrystallization from acetonitrile and crystallized in the orthorhombic system with the space group Pbca. Bent EDO-TTF-I molecules formed the dimer structure, and a short I⋯O contact was observed between dimers. Electrocrystallization of EDO-TTF-I in absolute ethanol containing tetrabutylammonium hexafluorophosphate, (TBA)PF6, afforded single crystals of (EDO-TTF-I)2PF6. An X-ray structural analysis revealed that EDO-TTF-I molecules form dimerized stacking columns in a head-to-tail manner, which is referred to as a β′-type arrangement. Iodine bonds between EDO-TTF-I and PF6 anions and short I⋯S contacts between EDO-TTF-I molecules were observed. Tight-binding band calculations indicated that the strong molecular dimerization splits the energy band into upper and lower bands with a small energy gap, where the upper band is effectively half-filled. It was found that (EDO-TTF-I)2PF6 is semiconducting (σRT = 5.3 S cm−1 and Ea = 0.17 eV) and exhibits magnetic properties reminiscent of a low-dimensional localized spin system. The magnetic data were analyzed by the Bonner–Fisher model incorporating interchain interactions: |J|/kB = 67.1 K and zJ′/kB = −61.1 K. No splitting of the C[double bond, length as m-dash]C stretching modes was observed in the range of 5–300 K by Raman spectroscopy, indicating a homogeneous charge distribution of EDO-TTF-I0.5+. Therefore, (EDO-TTF-I)2PF6 is considered as a dimerized Mott insulator.

Graphical abstract: Crystal structure and physical properties of radical cation salt based on 4,5-ethylenedioxy-4′-iodotetrathiafulvalene (EDO-TTF-I) with iodine bonding ability

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Publication details

The article was received on 12 Dec 2017, accepted on 26 Jan 2018 and first published on 29 Jan 2018


Article type: Research Article
DOI: 10.1039/C7QM00575J
Citation: Mater. Chem. Front., 2018,2, 752-759
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    Crystal structure and physical properties of radical cation salt based on 4,5-ethylenedioxy-4′-iodotetrathiafulvalene (EDO-TTF-I) with iodine bonding ability

    Y. Nakano, Y. Takahashi, K. Ishida, M. Ishikawa, H. Yamochi and M. Uruichi, Mater. Chem. Front., 2018, 2, 752
    DOI: 10.1039/C7QM00575J

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