Issue 8, 2013

Structure and magnetic properties of the ionic fullerene salt (TMP+)·(C60˙)·C6H5CN containing layers of monomeric C60˙ radical anions

Abstract

The fullerene salt, (TMP+)·(C60˙)·C6H5CN (1), with a layered structure was obtained as single crystals (TMP+ is the N,N,N′-trimethylpiperazinium cation). The fullerene layers alternating with the TMP+–C6H5CN layers along the c-axis have a honeycomb arrangement of C60˙ in which each fullerene has three neighbors with interfullerene C⋯C contacts in the 3.13–3.38 Å range. Despite the dense packing, the fullerene anions showed no intermolecular bond formation, even when down to helium temperatures. The structure of 1 was solved at 120 and 90 K. The fullerene molecules are disordered between three orientations at 120 K. The ordering transition observed in the 100–90 K range is accompanied by the trebling of the unit cell to provide three crystallographically independent fullerenes. The salt shows an asymmetric EPR signal down to 4 K which can be fitted by two Lorentzian lines with g1 = 1.9956 and a linewidth (ΔH) of 2.7 mT and g2 = 1.9815 and ΔH = 5.1 mT at room temperature. The ordering transition results in the abrupt narrowing of both lines in the 100–90 K range. The temperature dependence of the magnetic susceptibility of 1 follows the Curie–Weiss law with a negative Weiss temperature of −11 K, indicating an antiferromagnetic interaction of spins in the fullerene layers. Salt 1 is non-conducting with a room temperature resistivity of 7 × 107 Ω cm, which is probably due to the orientational disorder of the fullerenes and a relatively weak interaction between C60˙ in the layers. Indeed, the AM1 molecular orbital calculations show essentially smaller and more anisotropic overlap integrals between fullerenes than those in the layered metal (MDABCO+)·(C60˙)·TPC.

Graphical abstract: Structure and magnetic properties of the ionic fullerene salt (TMP+)·(C60˙−)·C6H5CN containing layers of monomeric C60˙− radical anions

Supplementary files

Article information

Article type
Paper
Submitted
18 Feb 2013
Accepted
23 May 2013
First published
28 May 2013

New J. Chem., 2013,37, 2521-2527

Structure and magnetic properties of the ionic fullerene salt (TMP+)·(C60˙)·C6H5CN containing layers of monomeric C60˙ radical anions

D. V. Konarev, A. V. Kuzmin, S. S. Khasanov, M. Ishikawa, A. Otsuka, H. Yamochi, G. Saito and R. N. Lyubovskaya, New J. Chem., 2013, 37, 2521 DOI: 10.1039/C3NJ00189J

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