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Supramolecular Chains and Coordination Nanowires Constructed of High-Spin CoII9WV6 Clusters and 4,4′-bpdo Linkers

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journal contribution
posted on 19.02.2016, 04:24 by Szymon Chorazy, Robert Podgajny, Wojciech Nitek, Michał Rams, Shin-ichi Ohkoshi, Barbara Sieklucka
Cyanido-bridged high-spin {CoII[CoII­(MeOH)3]8­[WV­(CN)8]6} (Co9W6) clusters revealing single-molecule magnet behavior were combined with 4,4′-bipyridine-N,N′-dioxide (4,4′-bpdo) linkers, giving unique H-bonded supramolecular {CoII9­(MeOH)24­[WV­(CN)8]6}·4,4′-bpdo·MeOH·2H2O (1) chains and one-dimensional coordination {CoII­[CoII­(4,4′-bpdo)1.5­(MeOH)]8­[WV­(CN)8]6}·2H2O (2) nanowires. The hydrogen-bonded chains of 1 are embedded within the three-dimensional supramolecular network stabilized by the series of noncovalent interactions between Co9W6 clusters, 4,4′-bpdo, and solvent molecules. The coordination nanowires 2, revealing an average core diameter of about 11 Å, are arranged parallel with the significant separation in the crystal structure, leading to a microporous supramolecular network with broad channels (12 × 12 Å) filled by methanol and water. Both 1 and 2 are stable only in a mother solution or an organic protectant, whereas they undergo the fast exchange of methanol ligands to water molecules during drying in the air. Synthesized materials preserve the magnetic characteristics of Co9W6 clusters with an effective ferromagnetic coupling, giving a ground-state spin of 15/2. For 2, the additional antiferromagnetic intercluster interactions are observed. Below 3 K, the frequency-dependent χM″(T) signals of 1 and 2 indicate the onset of slow magnetic relaxation. For 1, the relaxation time follows the Arrhenius law with an energy gap of Δ/kB = 10.3(5) K and τ0 = 4(1) × 10–9 s, which is consistent with single-molecule magnet behavior.

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