Rare examples of diphenoxido-bridged trinuclear Ni2IIFeIII complexes with a reduced salen type Schiff base ligand: Structures and magnetic properties

Three new trinuclear hetero-metallic complexes, [(NILR)(2)Fe(N-3)(3)] (1), [(NiLR(H2O))(2)Fe(C6H5CH2CO2)(2)]center dot (HSO4) (2) and [(NiLR(H2O))(2)Fe(C6H5CO2)(2)]center dot(HSO4)center dot(H2O)center dot(CH2Cl2) (3) have been synthesized using [NiLR] as a "metalloligand" (where H2LR = N,N'-bis(2-hydroxybenzyl)-1,3-propanediamine). All complexes have been characterized by elemental analysis, spectroscopic methods, single crystal XRD and magnetic study. In the angular trinuclear units of 1, the two terminals [NiLR] coordinate through double phenoxido bridges to the central Fe-III ion which is penta-coordinated having terminally coordinated azide ion. The two terminal Ni-II centers are connected to each other and also to neighbouring units through mu(1,3)-azido bridges to form an alternating chain. On the other hand, complexes, 2 and 3 are linear discrete trinuclear species [Ni-II-Fe-III-Ni-II] in which two terminal octahedral [NiLR] units coordinate to the central octahedral Fe-III ion, located on a crystallographic centre of symmetry, through a mu(2)-phenoxido oxygen atom and a bridging carboxylato ion. Variable temperature magnetic susceptibility measurements show the presence of antiferromagnetic exchange interactions in 1 mediated through the phenoxido bridges (J(1) = -33.2 cm(-1),) and mu(1,3)-N-3 single bridges (J(2) = -19.9 cm(-1) and J(3) = -16.7 cm(-1)). On the other hand, compounds 2 and 3 show ferromagnetic coupling interactions mediated through the double phenoxido bridges with J values of +4.9 and +3.0 cm(-1) for 2 and 3, respectively. (C) 2017 Elsevier Ltd. All rights reserved.