Structure-Property Relationships in Tricyanoferrate(III) Building Blocks and Trinuclear Cyanide-Bridged Complexes

• Published in: European journal of inorganic chemistry Vol. 2016; no. 15-16; pp. 2432 - 2442
• Main Authors: Zhang, Yuanzhu, Malik, Uma P., Quiggins, Benjamin, Nguyen, Hung, Beedle, Christopher C., Kovalev, Alexey E., Clérac, Rodolphe, Hill, Stephen, Bythell, Benjamin J., Holmes, Stephen M.
• Format: Journal Article
• Language: English
• Published: Blackwell Publishing Ltd 01.06.2016; Wiley-VCH Verlag
• Subjects: Chemical Sciences; Clusters; Cyanides; Ferromagnetic compounds; Material chemistry; Pyrazolylborate; Single-molecule magnets; Clusters; Pyrazolylborate; Cyanides; Single-molecule magnets; Ferromagnetic compounds
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201600199

The preparation, structures, and magnetic properties of two tricyanoferrates, [NEt4]2[(Tp*Me)FeII(CN)3]·MeCN (1) and [NEt4][(Tp*Me)FeIII(CN)3]·H2O (2), and three trinuclear derivatives, {[(Tp*Me)FeIII(CN)3]2[NiII(L)2]}·n(solvent) (L = bpy, 3; tren, 4; DETA, 5) are described. Magnetic measurements show that 2 is an S = 1/2 complex [g = 2.65(1)], while 3–5 display ST = 2 spin ground states, owing to cyanide‐mediated ferromagnetic exchange between FeIIILS (S = 1/2) and NiII (S = 1) ions. The χT vs. T data for 3–5 were modelled using an isotropic Heisenberg model and give J/kB and gavg values of +11.1(1) K and 2.48(1) for 3, 9.1(1) K and 2.6(1) for 4, and +11.2(1) K and 2.41(5) for 5 (with zJ′ = –0.28 K). High‐field/frequency EPR data indicates significant g‐anisotropy in 2 (gz = 3.6, gy = 2.2, gx = 2.0) and [NEt4][(Tp*)FeIII(CN)3]·H2O (6) (gz = 3.5, gy = 2.0, gx = 1.3), while 5 shows D = –2.09 cm–1, E = 0.08 cm–1, and B40 = –2.3 × 10–3 cm–1 with gz = 2.4 and gx = gy = 1.95. Despite significant magnetic anisotropy in 3–5, frequency‐dependent behavior is only seen for 5 above 1.8 K, suggesting that rapid quantum tunnelling of the magnetization is operative. The preparation, structures, and magnetic properties of a tricyanoferrate, [NEt4][(Tp*Me)Fe(CN)3] (2), and three trinuclear {FeIII2NiII} derivatives are described. High‐field/frequency EPR data indicates significant g‐anisotropy in 2 and considerable magnetic anisotropy in one {FeIII2NiII} complex (5).