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Issue 9, 2011
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Magnetic properties and stability of negatively charged doubly bonded C1202 dimers

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A new ionic complex {(MDABCO+)·ZnIITMPP}2·(C1202−)·(C6H4Cl2)2.15·(C6H5CN)1.85 (1) (ZnIITMPP: zinc(II) tetrakis(4-methoxyphenyl)porphyrin; MDABCO+: the cation of N-methyldiazabicyclooctane) has been obtained as single crystals. The complex contains negatively charged doubly bonded C1202 dimers whose magnetic properties have been studied. Magnetic moment of the complex is 2.69 μB at 290 K indicating presence of about two spins per dimer. The dimers show narrow doublet-like EPR signal with gM = 2.0014 and the linewidth of 0.315 mT at 290 K. The data of SQUID measurements for 1 can be fitted according to the Heisenberg model for isolated antiferromagnetically interacting spin pairs with exchange interaction of J/kB = −44.7 K. The EPR signal from the dimers and magnetic susceptibility of 1 decrease below 40 K resulting in diamagnetic dilution of the sample and the appearance of triplet features of the signal. Two pairs of lines show peak separation of 5.2 and 2.6 mT and are centered at gT = 2.0008. Averaged separation of 10.2 Å between two spins was estimated. Additional narrow doublet-like signal is manifested at 40 K and below. The signal was centered at gI = 1.9984 (20 K) and was attributed to the impurity of non-dimerized C60˙ since its intensity did not exceed 4% from that of the signal from the dimers. Heating of 1 above 380 K resulted in irreversible dissociation of the C1202 dimers to monomeric C60˙ which was accompanied by transition from narrow to broad EPR signal. The degree of dimer-monomer conversion was 97.5% at 446 K.

Graphical abstract: Magnetic properties and stability of negatively charged doubly bonded C1202− dimers

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The article was received on 27 Jan 2011, accepted on 18 May 2011 and first published on 01 Jul 2011

Article type: Paper
DOI: 10.1039/C1NJ20074G
Citation: New J. Chem., 2011,35, 1829-1835
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    Magnetic properties and stability of negatively charged doubly bonded C1202 dimers

    D. V. Konarev, S. S. Khasanov, A. Otsuka, H. Yamochi, G. Saito and R. N. Lyubovskaya, New J. Chem., 2011, 35, 1829
    DOI: 10.1039/C1NJ20074G

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