Syntheses, crystal structures, MMCT and magnetic properties of four one-dimensional cyanide-bridged complexes comprised of MII–CN–FeIII (M = Fe, Ru, Os)

Abstract

Four new one-dimensional (1D) zigzag chain cyanide-bridged complexes [cis-M^II(L)₂(CN)₂Fe^III(salen)](PF₆) (M = Fe, L = bpy, 3; M = Fe, L = phen, 4; M = Ru, L = bpy, 5; M = Os, L = bpy, 6) (bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, salen = N,N′-ethylenebis(salicylideneaminato) dianion) have been synthesized and structurally as well as magnetically characterized, especially 3 and 4 are mixed-valence complexes. Fortunately, the crystals of complexes 3, 4 and 6 suitable for single-crystal X-ray diffraction analysis were obtained. In addition, the electronic absorption spectra indicate the existence of the MMCT (metal-to-metal charge transfer) bands in complexes 3–6. The temperature dependent magnetic susceptibilities reveal that the Fe(III)–Fe(III) exchange coupling separated by a diamagnetic cyanidometal –NC–M(II)–CN– bridge is weakly ferromagnetic for 3–5, but weakly anti-ferromagnetic for 6. Moreover, the specific heat measurements suggest complexes 3–5 exhibit a phase transition at 2.8 K, 2.7 K and 2.6 K, respectively.