American Chemical Society
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Tuning of Inter- versus Intrachain Magnetic Interactions in Cyano-Bridged NiII/MIII (M = Cr, Fe, Co) Chain Complexes

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posted on 2006-09-18, 00:00 authored by Mihail Atanasov, Peter Comba, Sebastian Förster, Gerald Linti, Thomas Malcherek, Ronald Miletich, Alexander I. Prikhod'ko, Hubert Wadepohl
The reaction of [M(CN)6]3- (M = Cr3+, Fe3+, Co3+) with the nickel(II) complex of 2,4-diamino-1,3,5-triazin-6-yl-{3-(1,3,5,8,12-pentaazacyclotetradecane)} ([NiL]2+) in excess of ANO3 or ACl (A = Li+, Na+, K+, Rb+, Cs+, NH4+) leads to the cyano-bridged dinuclear assemblies A{[NiL][M(CN)6]}·xH2O (x = 2−5). X-ray structures of Li{[NiL][Cr(CN)6]}·5H2O, NH4{[NiL][Cr(CN)6]}·3.5H2O, K{[NiL][Cr(CN)6]}·4H2O, K{[NiL][Fe(CN)6]}·4H2O, Rb{[NiL][Fe(CN)6]}·3.5H2O, and Cs{[NiL][Fe(CN)6]}·3.5H2O, as well as the powder diffractometry of the entire FeIII series, are reported. The magnetic properties of the assemblies are dependent on the monocation A and discussed in detail. New efficient pathways for ferromagnetic exchange between NiII and FeIII or CrIII are demonstrated. Field dependencies of the magnetization for the FeIII samples at low temperature and low magnetic field indicate a weak interchain antiferromagnetic coupling, which is switched to ferromagnetic coupling at increasing magnetic field (metamagnetic behavior). The interchain magnetic coupling can be tuned by the size of the A cations.