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Issue 9, 2011
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Influence of structure on exchange strength and relaxation barrier in a series of FeIIReIV(CN)2 single-chain magnets

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Abstract

Cyano-bridged single-chain magnets of the type L4FeReCl4(CN)2, where L = diethylformamide (DEF) (1), dibutylformamide (DBF) (2), dimethylformamide (DMF) (3), dimethylbutyramide (DMB) (4), dimethylpropionamide (DMP) (5), and diethylacetamide (DEA) (6), have been synthesized to enable a systematic study of the influence of structural perturbations on magnetic exchange and relaxation barrier. Across the series, varying the amide ligand leads to Fe–N–C bond angles ranging from 154.703(7)° in 1 to 180° in 6. Variable-temperature dc magnetic susceptibility data indicate ferromagnetic exchange coupling in all compounds, with the strength of exchange increasing linearly, from J = +4.2(2) cm−1 to +7.2(3) cm−1, with increasing Fe–N–C bond angle. Ac magnetic susceptibility data collected as a function of frequency reveal that the relaxation barrier of the chain compounds rises steeply with increasing exchange strength, from 45 cm−1 to 93 cm−1. This examination demonstrates that subtle tuning of orbital overlap, and thus exchange strength, can engender dramatic changes in the relaxation barrier. Indeed, the perfectly linear Fe–N–C bond angle in 6 leads to one of the highest barriers and coercive fields yet observed for a single-chain magnet.

Graphical abstract: Influence of structure on exchange strength and relaxation barrier in a series of FeIIReIV(CN)2 single-chain magnets

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Publication details

The article was received on 06 Apr 2011, accepted on 18 May 2011 and first published on 23 Jun 2011


Article type: Edge Article
DOI: 10.1039/C1SC00220A
Citation: Chem. Sci., 2011,2, 1688-1694
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    Influence of structure on exchange strength and relaxation barrier in a series of FeIIReIV(CN)2 single-chain magnets

    X. Feng, T. David Harris and J. R. Long, Chem. Sci., 2011, 2, 1688
    DOI: 10.1039/C1SC00220A

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