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Antiferromagnetic exchange and long-range magnetic ordering in the supramolecular networks constructed of hexacyanido-bridged LnIII(3-pyridone)–CrIII (Ln = Gd, Tb) chains

Abstract

The complexes of paramagnetic lanthanide(3+) ions (Gd3+, Tb3+) with 3-pyridone molecules combined in the aqueous solution with paramagnetic hexacyanidochromate(III) metalloligands lead to the formation of two novel crystalline {[LnIII(3-pyridone)2(H2O)4][CrIII(CN)6]}·H2O (Ln = Gd, 1; Ln = Tb, 2) materials. They are composed of bimetalic Ln–Cr cyanido-bridged zig-zag chains which are further tightly connected by the rich system of hydrogen bonds involving terminal cyanides, water molecules and 3-pyridone ligands. Both 1 and 2 reveal very weak yellowish colour as their strong absorption, related to the d-d transitions of cyanide Cr(III) complex and 3-pyridone ligands, is moved to the UV range. 1 and 2 exhibit the Ln–Cr antiferromagnetic exchange mediated within the coordinaiton chains by molecular cyanide bridges. The magnetic susceptibilty for the GdIII–CrIII 7/2–3/2 spin alternating chains of 1 was successfully analysed using the quantum Monte Carlo simulations, giving the magnetic coupling constant, J of −0.82 K. The additional interchain magnetic interactions ensured by the hydrogen bonding network result in the low temperature phase transition to the magnetically ordered state. The magnetic heat capacity measurements showed that 1, which employed isotropic Gd(III) spin centers, becomes the molecule-based magnets below 1.06 K, while 2, bearing the highly anisotropic Tb(III), reveals the higher critical temperature of 1.61 K. Thus, we are showing and discussing the crucial role of the non-covalent interactions in the induction of magnetic ordering for low dimensional cyanido-bridged coordination systems, and the positive impact of magnetic anisotropy on the strengthening of magnetic interactions.

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Publication details

The article was received on 03 Dec 2017, accepted on 09 Jan 2018 and first published on 10 Jan 2018


Article type: Paper
DOI: 10.1039/C7CE02077E
Citation: CrystEngComm, 2018, Accepted Manuscript
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    Antiferromagnetic exchange and long-range magnetic ordering in the supramolecular networks constructed of hexacyanido-bridged LnIII(3-pyridone)–CrIII (Ln = Gd, Tb) chains

    S. Chorazy, M. Rams, M. Wyczesany, K. Nakabayashi, S. Ohkoshi and B. Sieklucka, CrystEngComm, 2018, Accepted Manuscript , DOI: 10.1039/C7CE02077E

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