Cyanide-Bridged Fe-III-Mn-III Bimetallic Complexes with Dimeric and Chain Structures Constructed from a Newly Made mer-Fe Tricyanide: Structures and Magnetic Properties

Abstract

Four cyanide-linked Fe-III-Mn-III complexes were prepared by reacting Mn Schiff bases with a new molecular precursor (PPh4)[Fe(qcq)(CN)(3)] [1; qcq = 8-(2-quinolinecarboxamido)quinoline anion]. They include a dimeric molecule, [Fe(qcq)(CN)(3)][Mn(3-MeOsalen)(H2O)]center dot 2H(2)O [2 center dot 2H(2)O; 3-MeOsalen = N,N'-ethylenebis(3-methoxysalicylideneiminato) dianion], and three 1D zigzag chains, [Fe(qcq)(CN)(3)][Mn(5-Clsalen)]center dot 3H(2)O [3 center dot 2MeOH; 5-Clsalen = N,N'-ethylenebis(5-chlorosalicylideneiminato) dianion], [Fe(qcq)(CN)(3)][Mn(5-Brsalen)] center dot 2MeOH [4 center dot 2MeOH; 5-Brsalen = N,N'-ethylenebis(5-bromosalicylideneiminato) dianion], and Fe(qcq)(CN)31[Mn(salen)] center dot MeCN center dot H2O [5 center dot MeCN; salen = N,N'-ethylenebis(salicylideneiminato) dianion]. The complexes consist of extensive hydrogen bonding and pi-pi stacking interactions, generating multidimensional structures. Magnetic studies demonstrate that antiferromagnetic couplings are operative between Fe-III and Mn-III centers bridged by cyanide ligands. On the basis of an infinite chain model, magnetic coupling parameters of 2-5 range from -9.3 to -14.1 cm(-1). A long-range order is observed at 2.3 K for 3 and 2.2 K for 4, while compound 5 shows spin glass behavior possibly coupled with magnetic ordering.