Iron(II)-octacyanoniobate(IV) ferromagnet with TC 43 K

Abstract

We have synthesized the octacyanoniobate-based cyano-bridged 3D ferromagnet {[FeII(H2O)2]2[Nb IV(CN)8]·4H2O}n1 and characterized structurally, spectroscopically (XANES/EXAFS, IR, UV-Vis, Resonance Raman, 57Fe Mössbauer spectroscopy) and magnetically. 1 crystallizes in the tetragonal system, space group I4/m, a = 11.989(5) Å, c = 13.237(5) Å, V = 1902.6(13) Å3. 3D coordination architecture comprises two types of NbIV-C-N-Fe IIHS (HS = high spin) linkages with Fe-N-C angles of 154.5° and 167.5°. The XANES/EXAFS spectra at Fe:K and Nb:K lines confirm the presence of NbIV-C-N-FeII linkages. Magnetic measurements reveal ferromagnetic ordering below Tc = 43 K with some non-collinearity of NbIV (S = 1/2) and FeII (S = 2) magnetic moments. The molecular field model simulation reproduces well the M(T) curve and Tc value with one average exchange coupling constant J FeNb = + 8.1 cm-1. © 2009 The Royal Society of Chemistry.