Cyanide-bridged Mn(III)-Fe(III) bimetallic complexes based on the pentacyano(1-methylimidazole)ferrate(III) building block: Structure and magnetic characterizations

Seven cyanide-bridged bimetallic complexes have been synthesized by the reaction of [Fe(1-CH(3)im)(CN)(5)](2-) with Mn(III) Schiff base complexes. Their crystal structure and magnetic properties have been characterized. Five complexes, [Mn-2(5-Brsalen)(2)Fe(CN)(5)(1-CH(3)im)]center dot H2O (1), [Mn-2(5-Clsalen)(2)(H2O)(2)Fe(CN)(5)(1-CH(3)im)]center dot H2O (2), [Mn-2(5-Clsaltn)(2)(H2O)(2)Fe(CN)(5)(1-CH(3)im)] (3), [Mn-2(5-Clsaltmen)(2)(H2O)(2)Fe(CN)(5)(1-CH(3)im)]center dot H2O (4), and [Mn-2(5-Brsaltmen)(2)(H2O)(2)Fe(CN)(5)(1-CH(3)im)]center dot CH3OH (5), are neutral and trinuclear with two [Mn(SB)](+) (SB2- = Schiff base ligands) and one [Fe(1-CH(3)im)(CN)(5)](2-). Complex {[Et4N][Mn(acacen)Fe(CN)(5)(1-CH(3)im)]}(n)center dot 6nH(2)O (6) is one-dimensional with alternate [Mn(acacen)](+) and [Fe(CN)(5)(1-CH(3)im)](2-) units. The two-dimensional complex {[Mn-4(saltmen)(4)Fe(CN)(5)(1-CH(3)im)]}(n)[ClO4](2n)center dot 9nH(2)O (7) consists of Mn4Fe units which are further connected by the phenoxo oxygen atoms. Magnetic studies show the presence of ferromagnetic Mn(III)-Fe(III) coupling in the trinuclear compounds with the magnetic coupling constant (J) ranging from 4.5 to 6.0 cm(-1), based on the Hamiltonian (H) over cap = -2J (S) over cap (Fe)((S) over cap (Mn(1)) + (S) over cap (Mn(2))). Antiferromagnetic interaction has been observed in complex 6, whereas ferromagnetic coupling occurs in complex 7. Complexes 6 and 7 exhibit long-range magnetic ordering with a T-N value of 4.0 K for 6 and T-c of 4.8 K for 7. Complex 6 shows metamagnetic behavior at 2 K, and complex 7 possesses a hysteresis loop with a coercive field of 500 Oe, typical of a soft ferromagnet.