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Conjunction of Chirality and Slow Magnetic Relaxation in the Supramolecular Network Constructed of Crossed Cyano-Bridged CoII–WV Molecular Chains

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journal contribution
posted on 03.10.2012, 00:00 by Szymon Chorazy, Koji Nakabayashi, Kenta Imoto, Jacek Mlynarski, Barbara Sieklucka, Shin-ichi Ohkoshi
The addition of chiral 2,2′-(2,6-pyridinediyl)­bis­(4-isopropyl-2-oxazoline) (iPr-Pybox) to a self-assembled CoII–[WV(CN)8] magnetic system gives two enantiomorphic cyano-bridged chains, {[CoII((S,S)-iPr-Pybox)­(MeOH)]3[WV(CN)8]2·​5.5MeOH·​0.5H2O}n (1-SS) and {[CoII((R,R)-iPr-Pybox) (MeOH)]3[WV(CN)8]2·​5.5MeOH·​0.5H2O}n (1-RR). Both compounds crystallize with a structure containing a unique crossed arrangement of one-dimensional chains that form a microporous supramolecular network with large channels (14.9 Å × 15.1 Å × 15.3 Å) filled with methanol. The investigated materials exhibited optical chirality, as confirmed by natural circular dichroism and UV–vis absorption spectra. 1-(SS) and 1-(RR) are paramagnets with cyano-mediated CoII–WV magnetic couplings that lead to a specific spin arrangement with half of the WV ions coupled ferromagnetically with their CoII neighbors and the other half coupled antiferromagnetically. Significant magnetic anisotropy with the easy axis along the [101] direction was confirmed by single-crystal magnetic studies and can be explained by the single-ion anisotropy of elongated octahedral CoII sites. Below 3 K, the frequency-dependent χM(T) signal indicated slow magnetic relaxation characteristic of single-chain magnets.

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